WO2014050198A1

WO2014050198A1 - Switching element and method for manufacturing same

Info

Publication number: WO2014050198A1
Application number: PCT/JP2013/063248
Authority: WO
Inventors: 直樹伴野; 宗宏多田; 阪本　利司
Original assignee: 日本電気株式会社
Priority date: 2012-09-28
Filing date: 2013-05-13
Publication date: 2014-04-03
Also published as: JPWO2014050198A1

Abstract

The present invention provides a "three-terminal switch" of novel structure, having two signal electrodes and a control electrode for controlling a switching action that forms or eliminates a metal bridge that couples the signal electrodes. When a metal-bridge-type switching element configured as a "three-terminal switch" is integrated in multi-layered copper wire, the advantage of enabling the current required in the switching action to be reduced to a far greater extent than a "two-terminal switch" is optimized, excellent control can be exercised in respect to the switching action, and the metal bridge for coupling the signal electrodes can be formed or eliminated. In the present invention, the side surface of a metal film and the side surface of a plug are used as the signal electrodes to constitute the "three-terminal switch," the side surfaces functioning as the electrodes are imparted with a curved shape, the contact surface area between the signal electrodes and an ion conductive layer is reduced, and the electric field is concentrated to a greater extent toward the curved sites. It is accordingly possible to realize an energy-efficient switch with exceptionally stable action.

Description

Switching element and method for manufacturing switching element

The present invention relates to a switching element and a method for manufacturing the switching element. The present invention relates to a variable resistance nonvolatile switching element, and more particularly to a metal bridge type switching element that can be used for the configuration of electronic devices such as programmable logic and memory, and a method of manufacturing the metal bridge type switching element.

In order to diversify the functions of programmable logic and promote implementation in electronic devices, it is necessary to reduce the size of switching elements that connect logic cells to each other and at the same time reduce their on-resistance. It becomes. It is known that the metal bridge type switching element is smaller in size and lower in on-resistance than the conventional semiconductor switch. As the metal bridge type switching element, there are a “2-terminal switch” disclosed in Patent Document 1 and a “3-terminal switch” disclosed in Non-Patent Document 1. The “two-terminal switch” has a structure in which an ion conductive layer is sandwiched between a “first electrode” that supplies metal ions and a “second electrode” that does not supply metal ions. ing. For example, as shown in FIG. 15, when the “second electrode” is grounded and a positive voltage is applied to the “first electrode”, the interface between the “first electrode” and the ion conductive layer is the “first electrode”. The metal becomes metal ions and dissolves in the ion conductive layer. On the other hand, on the “second electrode” side, using the electrons supplied from the “second electrode”, the metal ions in the ion conductive layer are deposited as metal in the ion conductive layer. A metal bridge structure is formed by the metal deposited in the ion conductive layer, and finally, a metal bridge connecting the “first electrode” and the “second electrode” is formed. Thereafter, when the “second electrode” is grounded and a negative voltage is applied to the “first electrode”, the metal that forms the metal bridge becomes metal ions and dissolves in the ion conductive layer. On the other hand, on the “first electrode” side, using the electrons supplied from the “first electrode”, the metal ions in the ion conductive layer become metal in the ion conductive layer, and the surface of the “first electrode” It precipitates in. Eventually, the metal bridge connecting the “first electrode” and the “second electrode” disappears. The two electrodes are switched by the formation and disappearance of metal bridges in the ion conductive layer. Since the “two-terminal switch” has a simple structure, the manufacturing process is simple, and the element size can be reduced to the nanometer order.

The wiring material of state-of-the-art semiconductor devices is mainly composed of copper, and a technique for efficiently forming a resistance variable nonvolatile switching element in the copper wiring is desired. Non-patent document 2 discloses a technique for integrating a metal bridge type switching element into a semiconductor device using an electrochemical reaction. Non-Patent Document 2 discloses a technique that combines the copper wiring on the semiconductor substrate and the “first electrode” of the metal bridge type switching element. If the structure disclosed in Non-Patent Document 2 is adopted, the process for newly forming the “first electrode” can be reduced. Therefore, a mask for manufacturing the “first electrode” is not required, and the number of photomasks (PR) to be added to manufacture the metal bridge type switching element is the same as that of the ion conductive layer and the “second electrode”. It can be two sheets required for production.

However, in the “two-terminal switch” in which signal transmission and switching control are performed at the same terminal, a current on the order of several hundreds of μA required for the formation / extinction of the metal bridge at the time of ON / OFF is applied to the signal terminal (“first electrode”). “Second electrode”).

Non-Patent Document 1 discloses a “three-terminal switch” provided with a “third electrode” that controls the formation and disappearance of a metal bridge in ON / OFF in addition to two terminals used for signal transmission. Yes. The “3-terminal switch” disclosed in Non-Patent Document 1 is the formation of a metal bridge that connects the source and the “second electrode” with the source of the FET as the “first electrode” in the signal transmission path. By erasing, the switch is written and erased. At this time, the metal ions used for forming the metal bridge are supplied from the “third electrode” into the ion conductive layer, and the metal ions eluted with the disappearance of the metal bridge are the “third electrode”. It is reduced to metal at the surface of the “electrode” and recovered. On the other hand, the metal deposited on the surface of the source and the “second electrode” connects the source and the “second electrode”, and by forming a metal bridge, two terminals used for signal transmission (the source and the “second electrode”) The “2-terminal switch” between “)” is turned on. On the contrary, as a result of elution of the metal deposited on the surface of the source and the “second electrode”, the disappearance of the metal bridge causes the “terminal” between the two terminals (source and “second electrode”) used for signal transmission. “Two-terminal switch” is turned off.

In the “three-terminal switch”, the current I ₃ flowing through the “third electrode” is divided into the current I ₁ flowing through the source and the current I ₂ flowing through the “second electrode” when the metal bridge is formed or eliminated. (I ₃ = I ₁ + I ₂ ). Therefore, compared with a “two-terminal switch” that controls signal transmission and switching at the same terminal, a “three-terminal switch” is provided with a “third electrode” that controls the formation and disappearance of metal bridges when ON / OFF. Then, the current flowing through the two terminals (source and “second electrode”) used for signal transmission can be greatly reduced.

In the “3-terminal switch” disclosed in Non-Patent Document 1, in the process of transition from the OFF state to the ON state, for example, when the source and the “second electrode” are grounded and the “third electrode” is applied with a positive voltage, At the interface between the “third electrode” and the ion conductive layer, the metal of the “third electrode” becomes metal ions and dissolves in the ion conductive layer. On the other hand, on the surface of the source and “second electrode”, metal ions in the ion conductive layer are formed on the surface of the source and “second electrode” using electrons supplied from the source and “second electrode”. To be deposited. The deposited metal forms a metal bridge between the source and the “second electrode”.

Conversely, in the process of transition from the ON state to the OFF state, for example, when the source and the “second electrode” are grounded and a negative voltage is applied to the “third electrode”, the metal constituting the metal bridge becomes a metal It becomes ions and dissolves in the ion conductive layer. On the other hand, at the interface between the “third electrode” and the ion conductive layer, using the electrons supplied from the “third electrode”, the metal ions in the ion conductive layer become a metal on the surface of the “third electrode”. To be deposited (recovered). As a result of dissolution of the metal constituting the metal bridge, cutting and extinction of the metal bridge proceed.

Patent Document 2 uses, as a “third terminal switch”, for example, a configuration schematically shown in FIG. 16, that is, a “third electrode” using an electrode made of copper capable of supplying metal ions, As the “electrode” and the “second electrode”, an electrode made of a refractory metal such as Pt, Ru, Ta, TaN, TiN, tungsten carbonitride (WCN) or a nitride thereof that does not supply metal ions is used. The case that is configured is disclosed. Patent Document 2 also discloses a form in which a “3-terminal switch” is integrated in a copper wiring.

Non-Patent Document 3 discloses a “3-terminal switch” that employs sidewall electrodes as “first electrode” and “second electrode”. At this time, the “third electrode” for supplying metal ions is formed so as to cover the ion conductive layer in contact with the side wall electrode. Accordingly, when a copper electrode, for example, a copper wiring or a copper plug, is used as the “third electrode” for supplying metal ions, the supply of copper ions from the copper wiring or the copper plug to the ion conductive layer is hindered. It is necessary to remove the covering of the copper wiring, the side wall surface of the copper plug, and the bottom surface by the barrier metal. Excluding the copper wiring and the side wall surface and bottom surface of the copper plug due to the barrier metal, copper diffusion from the side surface and bottom surface of the copper wiring and copper plug into, for example, an interlayer insulating film formed of SiO ₂ proceed. During operation for a long period of time, due to the diffusion of copper into the interlayer insulating film, a failure occurs in which adjacent copper wirings are short-circuited by “Cu dendrite”.

The device disclosed in Non-Patent Document 3, in particular, a “three-terminal switch” in which a “third electrode” for supplying metal ions is formed so as to cover the ion conductive layer is devised for integration in a multilayer wiring. Is not suggested in Non-Patent Document 3.

International Publication No. 2000/48196 JP 2011-2111165 A

“3-terminal switch” has the following advantages compared to “2-terminal switch”.

First, in the “3-terminal switch”, a signal terminal (first electrode and second electrode) used for signal transmission, and a control terminal (third electrode) used for controlling the switching at the time of ON / OFF operation of the switch. ) Is separated. By applying a switching voltage to the third electrode with respect to the first electrode and the second electrode, metal is deposited on the surface of the first electrode and the second electrode, and on the contrary, the metal is dissolved, and ON / OFF Rewriting between states. Therefore, in the “three-terminal switch”, the current I ₃ flowing through the “third electrode” and the current I ₁ flowing through the “first electrode” and the current I flowing through the “second electrode” when the metal bridge is formed and eliminated. Divided into _two (I ₃ = I ₁ + I ₂ ). The current I ₁ flowing through the “first electrode” and the current I ₂ flowing through the “second electrode” are deposited on the metal amount M ₁ deposited on the “first electrode” and the “second electrode”, respectively. It is dependent on the amount of metal M _2.

On the other hand, in the “two-terminal switch”, the current I _{1 ′} flowing through the “first electrode” and the current I _{2 ′} flowing through the “second electrode” are equal (I _{1 ′} = I ₂₎ when the metal bridge is formed or eliminated. _' ) The amount of current depends on the amount of metal deposited on the "second electrode".

Therefore, in the “three-terminal switch”, the current I ₁ flowing through the “first electrode” and the current I ₂ flowing through the “second electrode” when the metal bridge is formed (disappears) Compared with the current I _{1 ′} flowing through the “first electrode” and the current I _{2 ′} flowing through the “second electrode” at the time of formation (extinction), it can be significantly reduced.

The present inventors have found that it is desirable to satisfy the following three conditions when integrating the “3-terminal switch” in the copper wiring.

First, in order to integrate the “3-terminal switch” in the copper wiring and to control the ON / OFF operation of the switch well, the contact area S ₁ between the ion conductive layer and the “first electrode”, the ion conduction By reducing the contact area S ₂ between the layer and the “second electrode” as much as possible, the average current density I ₁ / S ₁ and the average current density I ₂ / S ₂ are increased, and the first electrode and the second electrode are improved in reproducibility. It is necessary to form a metal bridge between the electrodes.

Second, in the case where the “3-terminal switch” is integrated in the copper wiring, the “first electrode” and “second electrode” constituting the “3-terminal switch” are formed to reduce the number of steps of the copper wiring process. As for the “third electrode”, it is desirable to adopt a configuration that substitutes Cu wiring and Cu plug as much as possible. Third, for an electrode that cannot be substituted, it is desirable to employ a structure in which the number of etching processes is small and the etching process is easy when an electrode is manufactured by etching a metal film.

The structure of the conventional “3-terminal switch” does not satisfy all the above-mentioned three conditions when fabricated in a copper wiring. As a result, the variation in switching voltage or the copper associated with the fabrication of the switching element The increase in the number of wiring processes has led to an increase in the manufacturing cost of the entire semiconductor device.

In other words, when a “3-terminal switch” is integrated into a copper wiring, a proposal of a “3-terminal switch” that employs a configuration that satisfies the above three conditions is desired.

The present invention solves the above-described problems. The object of the present invention is to use a conventional copper wiring process, and can be integrated in a multilayer wiring layer, can be stably rewritten, and can be produced at a low cost. Type switching element and its manufacturing method. Another object is to provide a semiconductor device in which the metal bridge type switching element is provided in a multilayer wiring layer.

In order to achieve the above object, the metal bridge type switching element of the present invention comprises:
A first electrode that is a side wall portion of a metal film electrically connected to a Cu plug or Cu wiring constituting a multilayer wiring;
A second electrode which is a side wall portion of a metal film electrically connected to a Cu plug different from the first electrode;
An insulating film sandwiched between the first electrode and the second electrode;
An ion conductive layer capable of moving a metal ionized by an electric field is in contact with side surfaces of the first electrode and the second electrode;
It has at least one third electrode that is in contact with the ion conductive layer and supplies metal ions to the ion conductive layer, and the third electrode is composed of a Cu wiring that forms a multilayer wiring. Yes.
(Function)
First, since the signal electrode and the switching control electrode are separated as in the conventional three-terminal switch, the current that flows during switching is only the ion current of nA order necessary for metal deposition, and the current of μA order or more flows. Absent.

Also, the first electrode and the second electrode constituting the signal electrode are side walls of the metal film and have a small area, so that the electric field tends to concentrate. Therefore, the place where the metal bridge is formed is limited, and a stable three-terminal switching operation can be realized. This electric field concentration can reduce variations in operating voltage and operating current during switching operation.

Furthermore, since the first electrode and the second electrode are connected to the Cu plug or the Cu wiring, the three-terminal switching element of the present invention can be easily integrated into the Cu wiring.

In addition, the metal bridge-type switching element according to the present invention includes the configuration of the “two-terminal switch” in the following first embodiment and the “three-terminal switch” in the second embodiment to the fourth embodiment. A “three-terminal switch” configuration can be employed.

The metal bridge type switching element according to the first embodiment of the present invention is:
A variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a first metal film electrically connected to a first Cu plug and a first Cu wiring constituting the multilayer wiring layer;
The second electrode is a side wall portion of a second metal film electrically connected to a second Cu wiring constituting the multilayer wiring layer;
The metal bridge type switching element includes an insulating film sandwiched between the first metal film and the second metal film,
The first electrode composed of the side wall portion of the first metal film, the side wall portion of the insulating film, and the second electrode composed of the side wall portion of the second metal film form a laminated structure, and are formed on side surfaces of the laminated structure. The switching element is characterized in that the ion conductive layer is in contact therewith.

The metal bridge type switching element according to the second embodiment of the present invention is:
A variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a first metal film electrically connected to a first Cu plug and a first Cu wiring constituting the multilayer wiring layer;
The second electrode is a side wall portion of a second metal film electrically connected to a second Cu wiring constituting the multilayer wiring layer;
The metal bridge type switching element includes an insulating film sandwiched between the first metal film and the second metal film,
The first electrode composed of the side wall portion of the first metal film, the side wall portion of the insulating film, and the second electrode composed of the side wall portion of the second metal film form a stacked structure, and are formed on the side surfaces of the stacked structure. The ion conductive layer is in contact;
The metal bridge type switching element is
A third electrode in contact with the ion conductive layer and supplying metal ions into the ion conductive layer;
The third electrode is composed of a third Cu wiring constituting the multilayer wiring layer,
The portion where the ion conductive layer is in contact with the third Cu wiring and the supply of metal ions is selected on the upper surface of the third Cu wiring,
In the metal bridge type switching element, the switching operation between the ON state and the OFF state is performed by biasing the first electrode to the potential V ₁ , the second electrode to the potential V ₂ , and the third electrode to the potential V ₃ , respectively. And a bias difference | V ₃ −V ₁ | between the third electrode and the first electrode with respect to a bias difference | V ₂ −V ₁ | between the second electrode and the first electrode, The bias difference | V ₃ −V ₂ | between the third electrode and the second electrode is changed to | V ₃ −V ₂ |> | V ₂ −V ₁ |, | V ₃ −V ₁ |> | V ₂ −. By setting V ₁ |, the switching element is implemented by applying a switching voltage between the first electrode, the second electrode, and the third electrode.

For example, in the switching operation between the ON state and the OFF state in the metal bridge type switching element, the potential V ₁ of the first electrode and the potential V ₂ of the second electrode are biased to the same potential, and the third electrode The potential V ₃ is biased to a different potential, the bias difference | V ₃ −V ₁ | between the third electrode and the first electrode, and the bias difference | V ₃ − between the third electrode and the second electrode. By providing V ₂ |, a switching voltage is applied between the first electrode, the second electrode, and the third electrode.

The metal bridge type switching element according to the third embodiment of the present invention is:
A variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a first metal film electrically connected to a first Cu plug and a first Cu wiring constituting the multilayer wiring layer;
The second electrode is a second Cu wiring constituting the multilayer wiring layer,
The metal bridge type switching element is
Comprising an insulating film sandwiched between the first metal film and the second Cu wiring;
The first electrode composed of the side wall portion of the first metal film, the side wall portion of the insulating film, and the second Cu wiring form a laminated structure, and the ion conductive layer is in contact with the side surface of the laminated structure. There;
The metal bridge type switching element is
A third electrode in contact with the ion conductive layer and supplying metal ions into the ion conductive layer;
The third electrode is composed of a third Cu wiring constituting the multilayer wiring layer,
The portion where the ion conductive layer is in contact with the third Cu wiring and the supply of metal ions is selected on the upper surface of the third Cu wiring,
In the metal bridge type switching element, the switching operation between the ON state and the OFF state is performed by biasing the first electrode to the potential V ₁ , the second electrode to the potential V ₂ , and the third electrode to the potential V ₃ , respectively. And a bias difference | V ₃ −V ₁ | between the third electrode and the first electrode with respect to a bias difference | V ₂ −V ₁ | between the second electrode and the first electrode, The bias difference | V ₃ −V ₂ | between the third electrode and the second electrode is changed to | V ₃ −V ₂ |> | V ₂ −V ₁ |, | V ₃ −V ₁ |> | V ₂ −. By setting V ₁ |, the switching element is implemented by applying a switching voltage between the first electrode, the second electrode, and the third electrode.

In the metal bridge type switching element according to the first embodiment of the present invention, the metal bridge type switching element according to the second embodiment, and the metal bridge type switching element according to the third embodiment,
It is preferable that at least the side wall portion of the first metal film in contact with the ion conductive layer has a convex curvature.

The metal bridge type switching element according to the fourth embodiment of the present invention is:
A variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a barrier metal that covers a bottom portion and a side wall surface of a first Cu plug electrically connected to a first Cu wiring constituting the multilayer wiring layer,
The second electrode is a second Cu wiring constituting the multilayer wiring layer,
The metal bridge type switching element is
An insulating film sandwiched between a bottom surface of a barrier metal covering the bottom and side wall surfaces of the first Cu plug and a second Cu wiring;
The first electrode composed of a barrier metal sidewall covering the bottom and sidewall surfaces of the first Cu plug, the sidewall of the insulating film, and the second Cu wiring form a stacked structure, and the stacked structure The ion conductive layer is in contact with a side surface;
The metal bridge type switching element is
A third electrode in contact with the ion conductive layer and supplying metal ions into the ion conductive layer;
The third electrode is composed of a third Cu wiring constituting the multilayer wiring layer,
The portion where the ion conductive layer is in contact with the third Cu wiring and the supply of metal ions is selected on the upper surface of the third Cu wiring,
In the metal bridge type switching element, the switching operation between the ON state and the OFF state is performed by biasing the first electrode to the potential V ₁ , the second electrode to the potential V ₂ , and the third electrode to the potential V ₃ , respectively. And a bias difference | V ₃ −V ₁ | between the third electrode and the first electrode with respect to a bias difference | V ₂ −V ₁ | between the second electrode and the first electrode, The bias difference | V ₃ −V ₂ | between the third electrode and the second electrode is changed to | V ₃ −V ₂ |> | V ₂ −V ₁ |, | V ₃ −V ₁ |> | V ₂ −. By setting V ₁ |, the switching element is implemented by applying a switching voltage between the first electrode, the second electrode, and the third electrode.

In the metal bridge type switching element according to the present invention,
It is preferable that an upper surface of the ion conductive layer is covered with an ion barrier layer that blocks the metal ions.

Further, the metal bridge type switching element according to the present invention, in particular, the configuration of the “two-terminal switch” of the first embodiment and the “three-terminal switch” to the fourth embodiment of the second embodiment. A semiconductor device adopting the “3-terminal switch” configuration can have the following configuration.

A semiconductor device that employs a metal bridged switching element according to the first embodiment of the present invention,
A semiconductor device comprising a variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a first metal film electrically connected to a first Cu plug and a first Cu wiring constituting the multilayer wiring layer;
The second electrode is a side wall portion of a second metal film electrically connected to a second Cu wiring constituting the multilayer wiring layer;
The metal bridge type switching element includes an insulating film sandwiched between the first metal film and the second metal film,
The first electrode composed of the side wall portion of the first metal film, the side wall portion of the insulating film, and the second electrode composed of the side wall portion of the second metal film form a stacked structure, and are formed on the side surfaces of the stacked structure. , The ion conductive layer is in contact,
An upper surface of the ion conductive layer is covered with an ion barrier layer that blocks the metal ions.

A semiconductor device that employs a metal-bridged switching element according to the second embodiment of the present invention,
A semiconductor device comprising a variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a first metal film electrically connected to a first Cu plug and a first Cu wiring constituting the multilayer wiring layer;
The second electrode is a side wall portion of a second metal film electrically connected to a second Cu wiring constituting the multilayer wiring layer;
The metal bridge type switching element includes an insulating film sandwiched between the first metal film and the second metal film,
The first electrode composed of the side wall portion of the first metal film, the side wall portion of the insulating film, and the second electrode composed of the side wall portion of the second metal film form a stacked structure, and are formed on the side surfaces of the stacked structure. , The ion conductive layer is in contact,
An upper surface of the ion conductive layer is covered with an ion barrier layer that blocks the metal ions;
The metal bridge type switching element is
A third electrode in contact with the ion conductive layer and supplying metal ions into the ion conductive layer;
The third electrode is composed of a third Cu wiring constituting the multilayer wiring layer,
The portion where the ion conductive layer is in contact with the third Cu wiring and the supply of metal ions is selected on the upper surface of the third Cu wiring,
In the metal bridge type switching element, the switching operation between the ON state and the OFF state is performed by biasing the first electrode to the potential V ₁ , the second electrode to the potential V ₂ , and the third electrode to the potential V _3. And a bias difference | V ₃ −V ₁ | between the third electrode and the first electrode with respect to a bias difference | V ₂ −V ₁ | between the second electrode and the first electrode, The bias difference | V ₃ −V ₂ | between the third electrode and the second electrode is changed to | V ₃ −V ₂ |> | V ₂ −V ₁ |, | V ₃ −V ₁ |> | V ₂ −. By setting V ₁ |, the semiconductor device is implemented by applying a switching voltage between the first electrode, the second electrode, and the third electrode.

A semiconductor device that employs a metal-bridged switching element according to the third embodiment of the present invention,
A semiconductor device comprising a variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a first metal film that is electrically connected to a first Cu plug or Cu wiring constituting the multilayer wiring layer,
The second electrode is a second Cu wiring constituting the multilayer wiring layer,
The metal bridge type switching element is
Comprising an insulating film sandwiched between the first metal film and the second Cu wiring;
The first electrode composed of the side wall portion of the first metal film, the side wall portion of the insulating film, and the second Cu wiring form a laminated structure, and the ion conductive layer is in contact with the side surface of the laminated structure. There;
The metal bridge type switching element is
A third electrode in contact with the ion conductive layer and supplying metal ions into the ion conductive layer;
The third electrode is composed of a third Cu wiring constituting the multilayer wiring layer,
The portion where the ion conductive layer is in contact with the third Cu wiring and the supply of metal ions is selected on the upper surface of the third Cu wiring,
An upper surface of the ion conductive layer is covered with an ion barrier layer that blocks the metal ions;
In the metal bridge type switching element, the switching operation between the ON state and the OFF state is performed by biasing the first electrode to the potential V ₁ , the second electrode to the potential V ₂ , and the third electrode to the potential V _3. And a bias difference | V ₃ −V ₁ | between the third electrode and the first electrode with respect to a bias difference | V ₂ −V ₁ | between the second electrode and the first electrode, The bias difference | V ₃ −V ₂ | between the third electrode and the second electrode is changed to | V ₃ −V ₂ |> | V ₂ −V ₁ |, | V ₃ −V ₁ |> | V ₂ −. By setting V ₁ |, the semiconductor device is implemented by applying a switching voltage between the first electrode, the second electrode, and the third electrode.

A semiconductor device that employs a metal-bridged switching element according to the fourth embodiment of the present invention,
A semiconductor device comprising a variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a barrier metal that covers a bottom portion and a side wall surface of a first Cu plug electrically connected to a first Cu wiring constituting the multilayer wiring layer,
The second electrode is a second Cu wiring constituting the multilayer wiring layer,
The metal bridge type switching element is
An insulating film sandwiched between a bottom surface of a barrier metal covering the bottom and side wall surfaces of the first Cu plug and a second Cu wiring;
The first electrode composed of a barrier metal sidewall covering the bottom and sidewall surfaces of the first Cu plug, the sidewall of the insulating film, and the second Cu wiring form a stacked structure, and the stacked structure The ion conductive layer is in contact with a side surface;
The metal bridge type switching element is
A third electrode in contact with the ion conductive layer and supplying metal ions into the ion conductive layer;
The third electrode is composed of a third Cu wiring constituting the multilayer wiring layer,
The portion where the ion conductive layer is in contact with the third Cu wiring and the supply of metal ions is selected on the upper surface of the third Cu wiring,
In the metal bridge type switching element, the switching operation between the ON state and the OFF state is performed by biasing the first electrode to the potential V ₁ , the second electrode to the potential V ₂ , and the third electrode to the potential V _3. And a bias difference | V ₃ −V ₁ | between the third electrode and the first electrode with respect to a bias difference | V ₂ −V ₁ | between the second electrode and the first electrode, The bias difference | V ₃ −V ₂ | between the third electrode and the second electrode is changed to | V ₃ −V ₂ |> | V ₂ −V ₁ |, | V ₃ −V ₁ |> | V ₂ −. By setting V ₁ |, the semiconductor device is implemented by applying a switching voltage between the first electrode, the second electrode, and the third electrode.

By adopting the structure of the metal bridge type switching element according to the present invention, the metal bridge type nonvolatile switch element can be easily integrated in the multilayer wiring layer of the LSI. At the same time, in the metal bridge type switching element according to the present invention, the current required for the ON / OFF operation of the switch due to the formation / extinction of the metal bridge is a minute current. As a result, it is possible to easily realize a programmable logic configured using a metal bridged nonvolatile switching element that significantly reduces power consumption. Further, since the current required for the ON / OFF operation of the switch is a minute current, the size of the transistor mounted on the ON / OFF operation drive circuit of the metal bridge type switching element can be reduced, and the drive circuit can be reduced in area. .

In the metal bridge type switching device according to the present invention, the signal electrode (first electrode and second electrode) and the switching control electrode (first electrode 3) constituting the “three-terminal switch” are turned on / off. In this process, since a situation where the metal bridge is connected does not occur, a nonvolatile switching element excellent in ON / OFF operation reliability can be realized.

FIG. 1 is a diagram schematically illustrating an example of the configuration of the two-terminal switching element according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing the configuration of the two-terminal switching element of the first embodiment according to the first embodiment of the present invention. FIG. 3-1 is a cross-sectional view schematically showing an example of the manufacturing process of the two-terminal switching element of the first embodiment according to the first embodiment of the present invention. In the manufacturing process, FIG. FIG. 5 is a diagram showing a step 3; FIG. 3-2 is a cross-sectional view schematically showing an example of the manufacturing process of the two-terminal switching element of the first embodiment according to the first embodiment of the present invention. FIG. FIG. 4 is a diagram schematically illustrating an example of the configuration of the three-terminal switching element according to the second embodiment of the present invention. FIG. 5: is sectional drawing which shows typically the structure of the 3 terminal switching element of 1st embodiment concerning 2nd embodiment of this invention. FIG. 6A is a cross-sectional view schematically showing an example of the manufacturing process of the three-terminal switching element of the first embodiment according to the second embodiment of the present invention. In the manufacturing process, FIG. FIG. 10 is a diagram showing a step 5; FIG. 6-2 is a cross-sectional view schematically showing an example of the manufacturing process of the three-terminal switching element of the first embodiment according to the second embodiment of the present invention. In the manufacturing process, FIG. FIG. FIG. 7: is sectional drawing which shows typically the structure of the 3 terminal switching element of 2nd embodiment concerning 2nd embodiment of this invention. FIG. 8-1 is a cross-sectional view schematically showing an example of the manufacturing process of the three-terminal switching element of the second embodiment according to the second embodiment of the present invention. In the manufacturing process, FIG. FIG. 5 is a diagram showing a step 3; FIG. 8-2 is a cross-sectional view schematically showing an example of the manufacturing process of the three-terminal switching element of the second embodiment according to the second embodiment of the present invention. FIG. FIG. 9 is a diagram schematically illustrating an example of the configuration of the three-terminal switching element according to the third embodiment of the present invention. FIG. 10: is sectional drawing which shows typically the structure of the 3 terminal switching element of 1st embodiment concerning 3rd embodiment of this invention. FIG. 11-1 is a cross-sectional view schematically showing an example of the manufacturing process of the three-terminal switching element of the first embodiment according to the third embodiment of the present invention. FIG. 10 is a diagram showing a step 5; FIG. 11-2 is a cross-sectional view schematically showing an example of the manufacturing process of the three-terminal switching element of the first embodiment according to the third embodiment of the present invention. FIG. FIG. 12 is a diagram schematically illustrating an example of a configuration of a three-terminal switching element according to the fourth embodiment of the present invention. FIG. 13: is sectional drawing which shows typically the structure of the 3 terminal switching element of the 1st embodiment concerning 4th embodiment of this invention. FIG. 14 is a cross-sectional view schematically showing an example of a manufacturing process of the three-terminal switching element according to the first embodiment, according to the fourth embodiment of the present invention. FIG. FIG. 15 is a diagram for explaining a switching process in the metal bridge type switching element adopting the configuration of “two-terminal switch”, and the upper stage is a transition process (set process) from the “OFF” state to the “ON” state. The lower part is a diagram for explaining the transition process (reset process) from the “ON” state to the “OFF” state. FIG. 16 shows the first electrode and the second electrode used for signal transmission and the third electrode used for control of the switching operation in the metal bridge type switching element adopting the configuration of the conventional “3-terminal switch”. It is a figure which shows an example of arrangement | positioning typically.

Note that the reference numerals in FIGS. 1 to 14 mean the following.

0104, 0204, 0304, 0404, 0504, 0604, 0704, 0804, 0904, 1004, 1104, 1204, 1304, 1404 Ion conductive layers 0101, 0201, 0301, 0401, 0501, 0601, 0701, 0901, 1001, 1101, 1201, 1301, 1401 First electrode 0102, 0202, 0302, 0402, 0502, 0602, 0702, 1002, 1102, 1302, 1402 Second electrode 0105, 0405, 0905, 1009 Metal bridge 0107, 0207, 0307 First wiring 0212 , 0312, 0512, 0612, 0712, 0802, 0812, 1012, 1112, 1312, 1412 Second wiring 0108, 0208, 0308, 0408, 0508, 06 8, 0708, 0808, 0907, 1008, 1108 1st metal film 0109, 0209, 0309, 0409, 0509, 0609, 0709, 0809 2nd metal film 0203, 0205, 0214, 0217, 0305, 0303, 0314, 0317, 0503, 0505, 0514, 0517, 0603, 0605, 0614, 0617, 0703, 0705, 0714, 0717, 0723, 0805, 0803, 0814, 0817, 0823, 1005, 1014, 1015, 1016, 1017, 1105, 1114, 1117, 1305, 1314, 1317, 1405, 1414, 1417 Barrier insulating film 0106, 0206, 0306, 0406, 0506, 0606, 0706, 0806, 0906, 1006 1106, 1206, 1306, 1406 Plugs 0210, 0310 First barrier metal 0211, 0311, 0511, 0611, 0711, 0811, 1011, 1111, 1311, 1411 Second barrier metal 0103, 0213, 0215, 0216, 0315, 0316, 0403, 0513, 0515, 0516, 0613, 0615, 0616, 0713, 0715, 0716, 0813, 0815, 0816, 0903, 1013, 1113, 1115, 1116, 1203, 1313, 1315, 1316, 1413, 1415, 1416 Insulating film 0218, 0321, 0322, 0318, 0518, 0618, 0625, 0626, 0627, 0718, 0818, 0825, 0826, 0827, 1018 1109, 1118, 0923, 1420 Hard mask 0219, 0319, 0519, 0619, 0719, 0819, 1019, 1119, 1319, 1419 Semiconductor substrate 0220, 0320 2 terminal switch 0520, 0620, 0720, 0820, 1020, 1120, 1318 , 1418 Three-terminal switch 0221, 0524, 0724, 1205, 1309 Metal bridge 0407, 0507, 0607, 0707, 0807, 0902, 1007, 1107, 1202, 1307, 1407 First wiring A
0410, 0522, 0622, 0722, 0822, 0908, 0922, 1207, 1303, 1403 1st wiring B
0510, 0610, 0710, 0810, 1010, 1110, 1310, 1410 First barrier metal A
0521, 0621, 0721, 0821, 1021, 0921, 1308, 1408 First barrier metal B
0523, 0623, 1003, 1103 Protective insulating film

Hereinafter, the present invention will be described in more detail.

In the metal bridge type switching element according to the present invention, for example, the configuration of the “2-terminal switch” of the first embodiment and the “3-terminal switch” to the fourth embodiment of the second embodiment described below are explained. The configuration of the “3-terminal switch” can be employed. The features of the “two-terminal switch” of the first embodiment and the “three-terminal switch” of the second embodiment to the “three-terminal switch” of the fourth embodiment are as follows. explain.

(First embodiment)
The first embodiment of the metal bridge type switching element according to the present invention is a metal bridge type switching element adopting the configuration of a “two-terminal switch” described below.

The configuration of the “two-terminal switch” employed in the metal bridge type switching element according to the first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view schematically showing an example of the configuration of the “two-terminal switch” of the first embodiment.

As shown in FIG. 1, the “two-terminal switch” of the first embodiment includes a first metal film 0108 electrically connected to the plug 0106 and a first metal film 0107 electrically connected to the first wiring 0107. A two-metal film 0109 and an interlayer insulating film 0103 sandwiched between the first metal film 0108 and the second metal film 0109 and electrically separating them are provided.

The three-layer structure including the first metal film 0108, the interlayer insulating film 0103, and the second metal film 0109 is patterned in the same planar shape, and on the side surface of the patterned three-layer structure, the first metal film 0108 The side wall surface, the side wall surface of the interlayer insulating film 0103, and the side wall surface of the second metal film 0109 are exposed.

The ion conductive layer 0104 is provided so as to contact only a part of the side surface of the patterned three-layer structure. Of the side wall surface of the first metal film 0108, the portion in contact with the ion conductive layer 0104 functions as the first electrode 0101. Of the side wall surface of the second metal film 0109, the portion in contact with the ion conductive layer 0104 is It functions as the second electrode 0102. The ion conductive layer 0104 serves as a medium for conducting metal ions. Therefore, the “two-terminal switch” of the first embodiment is configured by using the first electrode 0101, the ion conductive layer 0104, and the second electrode 0102.

The second metal film 0109 is made of a metal that can supply metal ions to the ion conductive layer 0104. It is desirable to employ copper (Cu) as the metal capable of supplying the metal ions.

On the upper surface of the second metal film 0109, an interlayer insulating film 0103 is formed. The interlayer insulating film 0103 is an insulating material that can be vapor-deposited and formed using an insulating material that does not exhibit ion conductivity, such as a SiC film, a SiCN film, a SiN film, and a stacked structure thereof. can do.

The conductive material constituting the first metal film 0108 includes tantalum (Ta), titanium (Ti), tungsten (W), ruthenium (Ru), platinum (Pt), nickel (Ni), tantalum nitride (TaN), Titanium nitride (TiN) is suitable, and a laminate of these may be employed. In particular, Ru is preferable. The first metal film 0108 made of these conductive materials. A top surface of the interlayer insulating film 0103 is formed by a sputtering method, a laser ablation method, or a plasma CVD method.

When the “two-terminal switch” of the first embodiment transitions from the OFF state to the ON state, for example, when the first electrode 0101 is grounded and a positive voltage is applied to the second electrode 0102, the second electrode 0102 and the ion At the interface of the conductive layer 0104, metal ions (for example, copper ions) are supplied from the second electrode 0102 to the ion conductive layer 0104. On the other hand, at the interface between the first electrode 0101 and the ion conductive layer 0104, the first electrode 0101 is connected. Metal (for example, copper) precipitates on the side wall surface. The formation of the metal bridge 0105 due to the metal deposition starts from the lower end of the side wall surface of the first electrode 0101 and proceeds along the side wall surface of the interlayer insulating film 0103 toward the upper end of the side wall surface of the second electrode 0102. proceed.

In the “two-terminal switch” of the first embodiment, when the transition from the OFF state to the ON state is completed, the metal bridge 0105 is formed so as to connect the lower end of the first electrode 0101 and the upper end of the second electrode 0102. .

In the configuration of the “two-terminal switch” of the first embodiment shown in FIG. 1, the planar shape of the patterned three-layer structure is a circle, and accordingly, the planar shapes of the first metal film 0108 and the second metal film 0109 Is round. Therefore, the first electrode 101 made of the side wall surface of the first metal film 0108 and the second electrode 0102 made of the side wall surface of the second metal film 0109 also have the same curvature.

The ion conductive layer 0104 is formed by using a sputtering method, a laser ablation method, or a plasma CVD method in order to form the side surface of the three-layer structure having a curvature. As a material of the ion conductive layer 0104, it is necessary to select a material having a high conductivity of metal ions and capable of vapor phase etching processing in an LSI production line.

One of the candidate materials that can be used to fabricate the ion conductive layer 0104 is chalcogenide GeSbTe, which is used as a material for the phase change layer in the phase change element. As a means for forming the ion conductive layer 0104 made of GeSbTe on the side surface of the three-layer structure having a curvature, there is a method of forming a film by sputtering using a GeSbTe sintered target. Specifically, using a Ge ₂ Sb ₂ Te ₅ target, a film is formed of a film made of Ge ₂ Sb ₂ Te _5.

Another material candidate that can be used for manufacturing the ion conductive layer 0104 is a SIOCH-based material containing silicon, oxygen, carbon, and hydrogen, which is formed by a plasma CVD method. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material (cyclic organosiloxane) vapor is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is supplied directly to the reaction chamber in a separate line.

(Switching operation)
A driving method during ON / OFF operation (switching) in the “two-terminal switch” of the first embodiment shown in FIG. 1 will be described.

(A) ON operation (transition process from OFF state to ON state)
At the time of transition from the OFF state to the ON state, for example, the second electrode 0102 is grounded and a negative voltage (−V _ON <0 V) is applied to the first electrode 0101. At the interface between the second electrode 0102 and the ion conductive layer 0104, the metal is ionized (oxidized) by an electric field caused by the applied negative voltage, and the generated metal ions are supplied into the ion conductive layer 0104. The supplied metal ions migrate to the first electrode 0101 side by an electric field in the ion conductive layer 0104. The migrated metal ions receive electrons injected from the first electrode 0101 into the ion conductive layer 0104 and are reduced to metal. By this electrochemical reaction, metal deposition starts from the lower end of the surface (side wall surface) of the first electrode 0101, and the formation of the metal bridge 0105 according to the lines of electric force between the first electrode 0101 and the second electrode 0102. proceed. When the metal bridge 0105 formed from the first electrode 0101 side reaches the surface (side wall surface) of the second electrode 0102, the resistance value between the first electrode 0101 and the second electrode 0102 becomes low resistance, and the ON state Become.

The bias at the time of transition from the OFF state to the ON state may be such that the first electrode 0101 is grounded and a positive voltage (+ V _ON > 0 V) is applied to the second electrode 0102.

(B) OFF operation (transition process from ON state to OFF state)
On the other hand, at the time of transition from the ON state to the OFF state, for example, the second electrode 0102 is grounded and a positive voltage (+ V _OFF > 0 V) is applied to the first electrode 0101. First, on the second electrode 0102 side, ionization (oxidation) of the metal constituting the metal bridge 0105 and elution of metal ions into the ion conductive layer 0104 proceed (dissolution reaction). The metal ions eluted in the ion conductive layer 0104 migrate toward the surface (side wall surface) of the second electrode 0102 by an electric field formed in the ion conductive layer 0104. Metal ions are reduced by electrons injected into the ion conductive layer 0104 from the surface (side wall surface) of the second electrode 0102. The generated metal is re-deposited on the surface (side wall surface) of the second electrode 0102. When the dissolution of the metal bridge 0105 proceeds and the electrical connection between the surface (side wall surface) of the second electrode 0102 and the metal bridge 0105 is interrupted, the resistance value between the first electrode 0101 and the second electrode 0102 becomes high resistance. It will be in an OFF state.

The bias at the time of transition from the ON state to the OFF state may be such that the first electrode 0101 is grounded and a negative voltage (−V _OFF <0 V) is applied to the second electrode 0102.

Since the first electrode 0101 and the second electrode 0102 constituting the “two-terminal switch” of the first embodiment shown in FIG. 1 have curvature, the first electrode 0101 and the second electrode 0101 are switched during the ON / OFF operation (switching). The electric field formed in the ion conductive layer by the switching voltage applied between the two electrodes 0102 is concentrated on this curvature portion, and a stable and small switching operation can be obtained.

(First embodiment)
The two-terminal switching element of the first embodiment according to the first embodiment of the present invention will be described.

The two-terminal switching element of the first embodiment is formed inside a multilayer wiring layer provided in the semiconductor device. FIG. 2 shows the structure of the two-terminal switching element of the first embodiment formed inside a multilayer wiring layer provided in the semiconductor device.

The multilayer wiring layer provided in the semiconductor device shown in FIG. 2 includes a plug 0206 electrically connected to the first metal film 0208, a second wiring 0212 manufactured integrally with the plug 0206, and a second metal film. A first wiring 0207 connected to 0209 is provided. A barrier insulating film 0203 is sandwiched between the first metal film 0208 and the second metal film 0209, and the three-layer structure including the first metal film 0208, the barrier insulating film 0203, and the second metal film 0209 is a hard mask. By using 0218 as an etching mask and performing etching, it is patterned in the same planar shape. On the side surface of the patterned three-layer structure, the side wall portion of the first metal film 0208, the side wall portion of the barrier insulating film 0203, and the side wall portion of the second metal film 0209 are exposed.

A part of the side surface of the patterned three-layer structure is in contact with the ion conductive layer 0204, and the side wall portion of the first metal film 0208 in contact with the ion conductive layer 0204 is used as the first electrode 0201, A side wall portion of the second metal film 0209 that is in contact with the ion conductive layer 0204 is used as the second electrode 0202.

The two-terminal switch 0220 includes a first electrode 0201, a second electrode 0202, and an ion conductive layer 0204 that is in contact with the side wall portion.

A barrier insulating film 0214 is provided between the ion conductive layer 0204 and the interlayer insulating film 0215, and diffusion of metal ions from the ion conductive layer 0204 to the interlayer insulating film 0215 is performed using the barrier insulating film 0214. It is preventing. In addition, a barrier insulating film 0205 is provided between the ion conductive layer 0204 and the interlayer insulating film 0213, and metal ions from the ion conductive layer 0204 to the interlayer insulating film 0213 are formed using the barrier insulating film 0205. Prevents diffusion.

The barrier insulating film 0205 covers the upper surface of the interlayer insulating film 0213 and the upper surface of the first wiring 0207, and an opening is formed in the upper surface of the first wiring 0207. The two metal film 0209 and the upper surface portion of the first wiring 0207 are electrically connected. Accordingly, the barrier insulating film 0205 prevents contact between the second metal film 0209 and the upper surface of the interlayer insulating film 0213, and prevents diffusion of the metal constituting the second metal film 0209 into the interlayer insulating film 0213. .

The hard mask 0218 used for the etching process of the three-layer structure plays a role of preventing contact between the upper surface of the first metal film 0208 and the ion conductive layer 0204. The plug 0206 and the upper surface portion of the first metal film 0208 are electrically connected through an opening provided in the hard mask 0218.

Outside the region used for manufacturing the two-terminal switch 0220, the interlayer insulating film 0213, the barrier insulating film 0205, the ion conductive layer 0204, the barrier insulating film 0214, the interlayer insulating film 0215, and the interlayer insulating film 0216 are formed over the semiconductor substrate 0219. , And the barrier insulating film 0217 are stacked in this order to form a stacked structure.

The first wiring 0207 is embedded in the wiring trench provided on the interlayer insulating film 0213 formed on the semiconductor substrate 0219 with the first barrier metal 0210 interposed therebetween. The first barrier metal 0210 that covers the bottom surface and the side wall surface of the first wiring 0207 prevents diffusion of the metal constituting the first wiring 0207 into the interlayer insulating film 0213.

In the multilayer wiring layer, the second wiring 0212 is embedded in the wiring groove formed in the interlayer insulating film 0216, and the lower layer formed in the interlayer insulating film 0215, the barrier insulating film 0214, the ion conductive layer 0204, and the hard mask 0218. A plug 0206 is embedded in the hole (via hole), the second wiring 0212 and the plug 0206 are integrated, and the second wiring 0220 and the side and bottom surfaces of the plug 0206 are covered with the second barrier metal 0211.

A two-terminal switch 0220 shown in FIG. 2 is a variable resistance nonvolatile switching element, and in particular, uses metal ion migration and an electrochemical reaction in an ion conductor to form and extinguish a metal bridge. A metal bridge type switching element is configured. In the two-terminal switch 0220, a stacked structure of an etched second metal film 0209, a barrier insulating film 0205, a first metal film 0208, and a hard mask 0218 is formed on the opened barrier insulating film 0205. An ion conductive layer 0204 is formed so as to cover the upper surface of the barrier insulating film 0205 and the upper surface and side surfaces of the stacked structure, and the barrier insulating film 0214 is formed on the ion conductive layer 0204.

In the two-terminal switch 0220, the first metal film 0208 constituting the first electrode 0201 is electrically connected to the second wiring 0220, the plug 0206, and the second barrier metal 0211. In addition, the second metal film 0209 constituting the second electrode 0202 is electrically connected to the first wiring 0207 and the first barrier metal 0210 through an opening opened in the barrier insulating film 0205.

The two-terminal switch 0220 controls the ON / OFF state by applying a switching voltage or passing a switching current between the second wiring 0212 and the first wiring 0207. For example, metal ions are supplied from the side wall surface of the second electrode 0220 into the ion conductive layer 0204, metal atoms are precipitated by electrons supplied from the side wall surface of the first electrode, and electric field diffusion of metal ions in the ion conductive layer 0204 is performed. The metal bridge is generated and the transition operation from the OFF state to the ON state (ON operation) is controlled. The first metal film 0208 has a two-layer structure, and the surface (upper surface) in contact with the second barrier metal 0211 covering the bottom and side surfaces of the plug 0206 is made of the same conductive material as the second barrier metal 0211. Use. When the same conductive material is used, the second barrier metal 0211 is formed so as to cover the upper surface of the first metal film 0208 exposed at the bottom of the pilot hole (via hole) and the side wall surface of the pilot hole (via hole). When forming, at the interface between the upper surface of the first metal film 0208 and the second barrier metal 0211, the same conductive material is integrated to reduce the contact resistance. With the integration, the adhesiveness is also improved, and the reliability of the two-terminal switch 0220 can be improved.

The semiconductor substrate 0219 is a substrate on which a semiconductor element is formed. As the semiconductor substrate 0219, for example, a silicon substrate, a single crystal substrate, an SOI (Silicon-on-Insulator) substrate, a TFT (Thin-Film Transistor) substrate, a liquid crystal manufacturing substrate, or the like can be used.

The interlayer insulating film 0213 is an insulating film formed over the semiconductor substrate 0219. For the interlayer insulating film 0213, for example, SiO ₂ , a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of a silicon oxide film can be used. The interlayer insulating film 0213 may be a stack of a plurality of insulating films. In the interlayer insulating film 0213, a wiring groove for embedding the first wiring 0207 is formed, and the first wiring 0207 is embedded in the wiring groove via the first barrier metal 0210.

The first wiring 0207 is a wiring buried in the wiring trench formed in the interlayer insulating film 0213 through the first barrier metal 0210. In the first embodiment, the first wiring 0207 is made of Cu and is a “copper wiring”. The main component may be Cu and alloyed with Al. The first wiring 0207 is in direct contact with the second metal film 0209 that forms the second electrode 0202.

The first barrier metal 0210 has a barrier property that covers the side wall surface and the bottom surface of the first wiring 0207 in order to prevent the metal (Cu) constituting the first wiring 0207 from diffusing into the interlayer insulating film 0213 and the lower layer. It is a conductive film having As the first barrier metal 0210, for example, when the first wiring 0210 is formed of a metal material mainly composed of Cu, tantalum (Ta), tantalum nitride (TaN), titanium nitride (which has a barrier property against Cu) A high melting point metal such as TiN) or tungsten carbonitride (WCN), a nitride thereof, or a laminated film thereof can be used.

The barrier insulating film 0205 is formed on the surface of the first wiring 0207 and on the interlayer insulating film 0213. By covering with the barrier insulating film 0205, oxidation of the metal (for example, Cu) constituting the first wiring 0205 is prevented. The barrier insulating film 0205 has a role of preventing diffusion of metal ions (Cu ions) existing in the ion conductive layer 0204 into the interlayer insulating film 0213. In addition, as a result of providing the barrier insulating film 0205, the contact between the surface of the first wiring 0207 and the ion conductive layer 0204 is cut off, and when the switching voltage of the ON operation is applied to the two-terminal switch 0220, the first wiring The phenomenon that the metal (for example, Cu) constituting 0205 is ionized and supplied into the ion conductive layer 0204 does not occur. As the barrier insulating film 0205, for example, a SiC film, a SiCN film, a SiN film, a stacked structure thereof, or the like can be used.

An opening is formed in the barrier insulating film 0205 over the first wiring 0207. In the opening of the barrier insulating film 0205, the second metal film 0209 is in electrical contact with the surface of the first wiring 0207. The opening of the barrier insulating film 0205 is formed in the region of the first wiring 0207. The wall surface of the opening of the barrier insulating film 0205 is a tapered surface having a wide opening cross-sectional area from the boundary surface with the surface of the first wiring 0207 toward the upper surface of the barrier insulating film 0205. The taper angle θ _{taper of the} wall surface of the opening of the barrier insulating film 0210 is set to 85 ° or less (θ _taper ≦ 85 °) with respect to the upper surface of the first wiring 0207.

The second electrode 0202 and the first electrode 0201 are electrodes that transmit signals in the two-terminal switch 0220. The first electrode 0201 is a portion in direct contact with the ion conductive layer 0204 in the side wall portion of the first metal film 0208. The second electrode 0202 is a portion in direct contact with the ion conductive layer 0204 in the side wall portion of the second metal film 0209.

The second metal film 0209 is made of Cu or a conductive material containing Cu as a main component. The first metal film 0208 is composed of two layers of different metals. The lower layer of the first metal film 0208 that is in contact with the upper surface of the barrier insulating film 0203 is less likely to be ionized by an electric field generated at the interface in contact with the ion conductive layer 0204 when a switching voltage for OFF operation is applied to the two-terminal switch 0220. A metal that is difficult to diffuse or conduct in the ion conductive layer 0204 is used. For forming the lower layer of the first metal film 0208, for example, Pt, Ru, or the like can be used. The upper layer of the first metal film 0208 that is in contact with the lower surface of the hard mask 0218 has a role of protecting the lower layer. That is, for example, in the step of forming the hard mask 0218 so as to cover the first metal film 0208 and the step of forming the via hole for forming the plug 0206, the etching step of forming an opening in the hard mask 0218. The upper layer protects the lower layer, thereby suppressing damage to the lower layer during the process. As a result of suppressing damage to the lower layer of the first metal film 0208, the switching characteristics of the two-terminal switch 0220 can be maintained. For forming the upper layer of the first metal film 0208, for example, Ta, Ti, W, Al, or a nitride thereof can be used. The upper layer of the first metal film 0207 is electrically connected to the plug 0206 and the second wiring 0212 formed integrally with the plug 0206 through the second barrier metal 0211 in the opening provided in the hard mask 0218. ing.

As a result, the barrier insulating film 0203 is provided between the first metal film 0208 and the second metal film 0209. The barrier insulating film 0203 has a role of insulating the first metal film 0208 and the second metal film 0209 so as not to short-circuit each other. As the barrier insulating film 0203, for example, a SiC film, a SiCN film, a SiN film, a stacked structure thereof, or the like can be used.

The ion conductive layer 0204 is a film that can supply metal ions (Cu ions) from the second electrode when an ON operation switching voltage is applied to the two-terminal switch 0220. Further, it is a film in which metal ions (Cu ions) can move by an electric field present in the ion conductive layer 0204. For the ion conductive layer 0204, a material whose resistance is changed by the action (diffusion, ion transmission, etc.) of the metal included in the ion conductive layer can be used, and when the resistance change of the two-terminal switch 0220 is performed by deposition of metal ions. A membrane capable of ion conduction is used. Metal ions are supplied from the second electrode 0202 as Cu ions. A pilot hole for embedding the plug 0214 is formed in the barrier insulating film 0214, and the plug 0206 is embedded in the pilot hole via the second barrier metal 0211.

One candidate material that can be used to fabricate the ion conducting layer 0204 is chalcogenide GeSbTe, which is used in the phase change element as a material for the phase change layer. As a means for forming the ion conductive layer 0204 made of GeSbTe on the side surface of the three-layer structure having a curvature, there is a method of performing sputtering film formation using a GeSbTe sintered target. Specifically, using a Ge ₂ Sb ₂ Te ₅ target, a film is formed of a film made of Ge ₂ Sb ₂ Te _5.

Another material candidate that can be used for manufacturing the ion conductive layer 0204 is a SIOCH material containing silicon, oxygen, carbon, and hydrogen, which is formed by a plasma CVD method. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material (cyclic organosiloxane) vapor is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is supplied directly to the reaction chamber in a separate line.

The hard mask 0218 is used as a hard mask (etching mask) when the first metal film 0208, the barrier insulating film 0203, and the second metal film 0209 are etched. For the hard mask 0218, for example, a SiN film, a SiO ₂ film, or a laminate thereof can be used.

The barrier insulating film 0214 is an insulating film having a function of preventing diffusion of metal ions contained in the ion conductive layer 0204 into the interlayer insulating film 0215 without damaging the two-terminal switch 0220. In addition, the barrier insulating film 0214 has a function of preventing the desorption of oxygen contained in the ion conductive layer 0204, and prevents damage to the ion conductive layer 0204 during the formation process of the interlayer insulating film 0215. It also has a function to do. As the barrier insulating film 0214, for example, a SiN film, a SiCN film, or the like can be used. The barrier insulating film 0214 is preferably made of the same material as the barrier insulating film 0205.

The interlayer insulating film 0215 is an insulating film formed over the barrier insulating film 0214. For the interlayer insulating film 0215, for example, a SiO ₂ or SiOC film can be used. The interlayer insulating film 0215 may be a stack of a plurality of insulating films. The interlayer insulating film 0215 may be made of the same material as the interlayer insulating film 0213 and the interlayer insulating film 0216.

In the interlayer insulating film 0215, the barrier insulating film 0214, the ion conductive layer 0204, and the hard mask 0218, a pilot hole (via hole) for embedding the plug 0214 is formed, and the second barrier metal 0211 is formed in the pilot hole (via hole). A plug 0206 is embedded via

The interlayer insulating film 0216 is an insulating film formed over the interlayer insulating film 0215. As the interlayer insulating film 0216, for example, a SiO ₂ film, a SiOC film, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of SiO ₂ can be used. The interlayer insulating film 0216 may be a stack of a plurality of insulating films. The interlayer insulating film 0216 may be formed of the same material as the interlayer insulating film 0215 and the interlayer insulating film 0213. Alternatively, the interlayer insulating film 0216 and the interlayer insulating film 0215 can be formed using different insulating materials, and a significant difference can be provided in the etching characteristics. In the interlayer insulating film 0216, a wiring groove for embedding the second wiring 0212 is formed, and the second wiring 0212 is embedded in the wiring groove via the second barrier metal 0211.

The second wiring 0212 is a wiring embedded in the wiring trench formed in the interlayer insulating film 0216 via the second barrier metal 0211. The second wiring 0212 is integrated with the plug 0206.

After forming a pilot hole (via hole) for embedding the plug 0214 and a wiring groove for embedding the second wiring 0212, the second wiring is inserted into the pilot hole (via hole) and the wiring groove via the second barrier metal 0211. 0212 and the plug 0206 are integrated and embedded. For example, Cu can be used for forming the second wiring 0212 and the plug 0206.

In the second barrier metal 0211, the metal constituting the second wiring 0212 and the plug 0206 includes an interlayer insulating film 0216, an interlayer insulating film 0215, a barrier insulating film 0214, an ion conductive layer 0204, a hard mask 0218, and a lower layer (first In order to prevent diffusion into the metal film 0208), the conductive film has a barrier property and covers the side surfaces and the bottom surface of the second wiring 0212 and the plug 0206. For example, when the second wiring 0212 and the plug 0206 are made of a metal material containing Cu as a main component, the second barrier metal 0212 includes a refractory metal such as Ta, TaN, TiN, and WCN, nitride thereof, and the like. Alternatively, or a stacked film thereof can be used.

The barrier insulating film 0217 is formed on the upper surface of the second wiring 0212 and the interlayer insulating film 0216, and prevents oxidation of a metal (for example, Cu) constituting the second wiring 0217, or the second wiring 0212 to the upper layer. It is an insulating film which has a role which prevents the spreading | diffusion of the metal (for example, Cu) which comprises. As the barrier insulating film 0217, for example, a SiC film, a SiCN film, a SiN film, a stacked structure thereof, or the like can be used.

(Switching operation)
A driving method during the switching operation of the two-terminal switch of the first embodiment shown in FIG. 2 will be described.

(A) ON operation (transition process from OFF state to ON state)
The first wiring 0207 is grounded. As a result, the second metal film 0209 electrically connected to the surface of the first wiring 0207 is also grounded, and the second electrode 0202 constituted by the side wall surface of the second metal film 0209 is also grounded. Therefore, the potential V ₂ of the second electrode 0202 is V ₂ = 0V.

On the other hand, a negative voltage (−V _ON <0 V) is applied to the second wiring 0212. As a result, a negative voltage (−V _ON <0 V) is also applied to the first metal film 0208 electrically connected to the plug 0206 formed integrally with the second wiring 0212, and the first metal film 0208 is applied. The first electrode 0201 constituted by the side wall surface of the negative electrode is also in a state where a negative voltage (−V _ON <0 V) is applied. Therefore, the potential V ₁ of the first electrode 0201 is V ₁ = −V _ON .

At the interface between the second electrode 0202 and the ion conductive layer 0204, the metal constituting the second electrode 0202 is ionized by an electric field generated by applying a negative voltage (−V _ON <0 V), and the metal is transferred to the ion conductive layer 0204. Ions (Cu ions) are supplied. The supplied metal ions (Cu ions) migrate to the first electrode 0201 side by an electric field in the ion conductive layer 0204. The migrated metal ions receive electrons from the first electrode 0201 according to the lines of electric force between the first electrode 0201 and the second electrode 0202, and are deposited as metal by an electrochemical reaction. Formation of the metal bridge 0221 from the lower layer portion of the first electrode 0201 to the upper end portion of the second electrode 0202 proceeds by the deposited metal. By forming the metal bridge 0221 that connects the lower layer portion of the first electrode 0201 and the upper end portion of the second electrode 0202, the resistance value between the first electrode 0201 and the second electrode 0202 becomes low resistance, and the ON state is obtained.

In the transition to the ON state described above, the first electrode 0201 may be grounded (V ₁ = 0V) and a positive voltage may be applied to the second electrode 0202 (V ₂ = + V _ON > 0V).

(B) OFF operation (transition process from ON state to OFF state)
The first wiring 0207 is grounded. As a result, the second metal film 0209 electrically connected to the surface of the first wiring 0207 is also grounded, and the second electrode 0202 constituted by the side wall surface of the second metal film 0209 is also grounded. Therefore, the potential V ₂ of the second electrode 0202 is V ₂ = 0V.

On the other hand, a positive voltage (+ V _OFF > 0 V) is applied to the second wiring 0212. As a result, a positive voltage (+ V _OFF > 0 V) is also applied to the first metal film 0208 electrically connected to the plug 0206 formed integrally with the second wiring 0212, and the first metal film 0208 The first electrode 0201 constituted by the side wall surface is also in a state where a positive voltage (+ V _OFF > 0 V) is applied. Therefore, the potential V ₁ of the first electrode 0201 is V ₁ = + V _OFF .

When a positive voltage (+ V _OFF > 0 V) is applied to the first electrode 0201, the metal constituting the metal bridge 0221 is ionized by the generated electric field at the interface between the ion conductive layer 0204 and the metal bridge 0221, The dissolution reaction proceeds. Metal ions (Cu ions) generated by a dissolution reaction on the surface of the metal bridge 0221 migrate to the second electrode 0202 side by an electric field present in the ion conductive layer 0204. The metal ions that have reached the interface between the second electrode 0202 and the ion conductive layer 0204 receive electrons from the second electrode 0202 and are deposited as metal by an electrochemical reaction.

When the dissolution reaction proceeds and the conduction path connecting the lower layer portion of the first electrode 0201 and the upper end portion of the second electrode 0202 by the metal bridge 0221 is interrupted, the resistance value between the first electrode 0201 and the second electrode 0202 Becomes a high resistance and transits to the OFF state.

In the above transition to the ON state, the first electrode 0201 may be grounded (V ₁ = 0V), and a negative voltage may be applied to the second electrode 0202 (V ₂ = −V _OFF <0V).

Since the first electrode 0201 and the second electrode 0202 have curvature, the electric field concentrates on the curvature portion during switching between the ON state and the OFF state, and an operation with stable and small variation can be obtained.

In the two-terminal switch 0220 shown in FIG. 2, the planar shape of the first metal film 0208 and the second metal film 0209 is “circular” with the plug 0206 as the central axis. At that time, in the two-terminal switch 0220 having axial symmetry with the plug 0206 as the central axis, the position where the metal bridge 0221 is formed during the switching operation is the position shown in FIG. The position may be symmetrical with respect to the line.

(Manufacturing process)
In a semiconductor device comprising a variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate, the two-terminal switching element of the first embodiment shown in FIG. A manufacturing process for manufacturing a nonvolatile switching element will be described. 3A and 3B are cross-sectional views schematically showing an example of the manufacturing process of the two-terminal switching element of the first embodiment. FIG. 3A is a diagram illustrating steps 1 to 3 in the manufacturing process, and FIG. 3B is a diagram illustrating steps 4 to 8 in the manufacturing process.

(Process 1)
An interlayer insulating film 0313 (eg, 300 nm thick SiO ₂ , 150 nm thick SiOCH, 100 nm thick SiO ₂ ) is deposited on a semiconductor substrate 0319 (eg, a substrate on which a semiconductor element is formed), and then lithography is performed. Using a method (including photoresist formation, dry etching, and photoresist removal), a wiring groove is formed in the interlayer insulating film 0313, and then a first barrier metal 0310 (for example, TaN / Ta, film thickness) is formed in the wiring groove. The first wiring 0307 (for example, Cu) is buried via 5 nm / 5 nm). The interlayer insulating film 0313 can be formed by a plasma CVD method. The first wiring 0307 is formed, for example, by forming a first barrier metal 0310 (for example, a TaN / Ta laminated film) by the PVD method. After forming the Cu seed by the PVD method, Cu is embedded in the wiring groove by the electrolytic plating method. Then, after heat treatment at a temperature of 200 ° C. or higher, excess copper other than in the wiring trench can be removed by CMP. As a method for forming such a series of copper wirings, a general method in this technical field can be used. Here, the CMP (Chemical Mechanical Polishing) method is to planarize the unevenness on the wafer surface that occurs during the multilayer wiring formation process by bringing the polishing liquid into contact with a rotating polishing pad while flowing the polishing liquid over the wafer surface. Is the method. By polishing excess copper embedded in the wiring trench, a buried wiring (damascene wiring) is formed, or by planarizing the interlayer insulating film 0313 by polishing.

(Process 2)
A barrier insulating film 0305 (eg, SiN, film thickness of 30 nm) is formed over the interlayer insulating film 0313 including the first wiring 0307. Here, the barrier insulating film 0305 can be formed by a plasma CVD method. The thickness of the barrier insulating film 0305 is preferably about 10 nm to 50 nm. A hard mask 0321 (eg, SiO ₂ ) is formed over the barrier insulating film 0305. At this time, the hard mask 0321 is preferably made of a material different from the barrier insulating film 0305 from the viewpoint of maintaining a high etching selectivity in the dry etching process, and may be an insulating film or a conductive film. For the hard mask 0321, for example, SiO ₂ , SiN, SiCN, TiN, Ti, Ta, TaN, or the like can be used, and a laminated body of SiCN / SiO ₂ can be used.

(Process 3)
An opening is patterned on the hard mask 0321 using a photoresist (not shown), and an opening pattern is formed on the hard mask 0321 by dry etching using the photoresist as a mask. Strip the resist. At this time, the dry etching is not necessarily stopped on the upper surface of the barrier insulating film 0321 and may reach the inside of the barrier insulating film 0321.

(Process 4)
Using the hard mask 0321 as a mask, the barrier insulating film 0305 exposed from the opening of the hard mask 0321 is etched back (dry etching), whereby an opening is formed in the barrier insulating film 0305 and the opening of the barrier insulating film 0305 is formed. Then, the first wiring 0307 is exposed, and then an organic stripping process is performed with an amine-based stripping solution or the like to remove copper oxide formed on the exposed surface of the first wiring 0307 and etching that occurs at the time of etch back Remove double products. When the barrier insulating film 0305 is etched back, the wall surface of the opening of the barrier insulating film 0305 can be tapered by using reactive dry etching. In reactive dry etching, a gas containing fluorocarbon can be used as an etching gas. The hard mask 0321 is preferably completely removed during the etch-back, but may remain as it is when it is an insulating material. The shape of the opening in the barrier insulating film 0305 can be a circle, and the diameter of the circle can be 30 nm to 500 nm. The oxide on the surface of the first wiring 0307 is removed by RF (Radio Frequency) etching using a non-reactive gas. As the non-reactive gas, helium or argon can be used.

(Process 5)
On the opened barrier insulating film 0305, a second metal film 0309 (for example, Cu 10 nm), a barrier insulating film 0303 (for example, SiCN film, 10 nm in thickness), and a first metal film 0308 (for example, Ru 10 nm and Ta 10 nm are deposited in this order). Are deposited in order. Further, a hard mask 0318 (eg, SiN film, film thickness 30 nm) and a hard mask 0322 (eg, SiO ₂ film, film thickness 100 nm) are stacked in this order. In Step 5, the hard mask 0318 and the hard mask 0322 can be formed by a plasma CVD method. In step 5, the first metal film 0308 and the second metal film 0309 are formed by sputtering. Further, a photoresist (not shown) for patterning the hard mask 0322 is formed, and then the hard mask 0322 is dry-etched using the photoresist as a mask until the hard mask 0318 appears, and then oxygen plasma ashing is performed. The photoresist is removed using organic stripping. The shape of the photoresist as viewed from above is a circle or an ellipse depending on the exposure pattern of the mask.

Alternatively, the exposure pattern may be rectangular or square, and the curvature may be given by side etching when the hard mask 0322 is etched.

(Step 6)
Next, using the hard mask 0322 as an etching mask, the hard mask 0318, the first metal film 0308, the barrier insulating film 0303, and the second metal film 0309 are successively dry-etched to form the first electrode 0301 and the second electrode 0302. To do. At this time, it is preferable that the hard mask 0322 is completely removed by etching during the series of etching processes. A part of the hard mask 0322 (a residual film having a uniform thickness) may remain as it is. In step 6, for example, when the upper layer of the first metal film 0308 is Ta, it can be processed by Cl ₂ RIE. When the lower layer of the first metal film 0308 is Ru, and when the second metal film 0309 is In the case of Cu, RIE processing can be performed with a mixed gas of Cl ₂ / O ₂ . By using such a hard mask RIE method, etching can be performed without exposing the first metal film 0308 and the second metal film 0309 to oxygen plasma ashing for resist removal.

Further, when the resist oxidation treatment is performed by oxygen plasma after the etching process, the oxidation plasma treatment can be irradiated without depending on the resist stripping time. In step 6, the etching recipe may be adjusted so that the hard mask 0318, the first metal film 0308, the barrier insulating film 0303, and the second metal film 0309 have curvature.

(Step 7)
Next, an SIOCH-based ion containing silicon, oxygen, carbon, and hydrogen is used as the ion conductive layer 0304 so as to be in contact with the side surfaces of the barrier insulating film 0305, the first electrode 0301, the second electrode 0302, and the barrier insulating film 0303 over the hard mask 0318. A conductive layer is formed with a thickness of about 20 nm to 80 nm by a CVD method. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is directly supplied to the reaction chamber by another line. The temperature is preferably about 250 ° C to 350 ° C. Next, SiN or SiCN is formed to a thickness of 30 nm as the barrier insulating film 0314 over the ion conductive layer 0304. In step 8, the barrier insulating film 0314 can be formed by a plasma CVD method. For example, it is preferable to use a SiN film in which a mixed gas of SiH ₄ / N ₂ is formed by high-density plasma. Although the ion conductive layer 0304 remains in a region other than the two-terminal switch element 0320, it functions as an insulating film and thus does not affect the operation of the two-terminal switch and the multilayer wiring. In step 7, 300 nm of SiO ₂ is formed as an interlayer insulating film 0315 on the barrier insulating film 0314. Further, in order to eliminate the level difference caused by the two-terminal switch 0320, the interlayer insulating film 0315 is flattened by polishing by about 170 nm by a CMP method. The interlayer insulating film 0315 is desirably formed of SiO ₂ using high-density plasma in order to reliably fill the steps of the two-terminal switch element 0320.

(Process 8)
Next, an interlayer insulating film 0316 (for example, a laminate of SiOC and SiO ₂ having a low relative dielectric constant) is deposited on the interlayer insulating film 0315, and then a pilot hole for the plug 0306 and a wiring groove for the second wiring 0312 are deposited. Is formed by dry etching, and a second wiring 0312 (for example, Cu) and a plug are inserted into the wiring groove and the prepared hole through a second barrier metal 0311 (for example, TaN / Ta) using a copper dual damascene wiring process. 0306 (for example, Cu) is formed at the same time, and then a barrier insulating film 0317 (for example, a SiCN film) is deposited over the interlayer insulating film 0316 including the second wiring 0312. In step 8, the second wiring 0312 and the plug 0306 are formed by, for example, forming a second barrier metal 0311 (for example, a TaN / Ta laminated film) by the PVD method, forming a Cu seed by the PVD method, and then performing electrolytic plating. It can be formed by embedding copper in the wiring groove by the method, after heat treatment at a temperature of 200 ° C. or higher, and then removing excess copper other than in the wiring groove by the CMP method. As a method for forming such a series of copper wirings, a general method in this technical field can be used. In step 8, by making the upper layer of the second barrier metal 0311 and the first metal film 0308 the same material, the contact resistance between the plug 0306 and the first metal film 0308 is reduced, and the element performance is improved (in the ON state). The resistance of the two-terminal switch can be reduced). In Step 8, the interlayer insulating film 0316 and the barrier insulating film 0317 can be formed by a plasma CVD method. In step 8, when forming the prepared hole of the plug 0306, it reaches the upper layer of the first metal film 0308, and the material of the upper layer of the first metal film 0308 functions as an etching stopper material. A fluorocarbon gas is used for dry etching of the prepared hole for the plug 0306 and the wiring groove for the second wiring 0312.

(Second embodiment)
The second embodiment of the metal bridge type switching element according to the present invention is a metal bridge type switching element adopting the configuration of a “three-terminal switch” described below.

The configuration of the “three-terminal switch” employed in the metal bridge type switching element according to the second embodiment of the present invention will be described. FIG. 4 is a cross-sectional view schematically showing an example of the configuration of the “3-terminal switch” of the second embodiment.

As shown in FIG. 4, the “three-terminal switch” of the second embodiment includes a first metal film 0408 electrically connected to the plug 0406 and a first metal film 0408 electrically connected to the first wiring A0407. A two-metal film 0409 and an interlayer insulating film 0403 sandwiched between and electrically separating the first metal film 0408 and the second metal film 0409 are provided.

The three-layer structure including the first metal film 0408, the interlayer insulating film 0403, and the second metal film 0409 is patterned in the same planar shape, and the side surface of the patterned three-layer structure has the first metal film 0408 The side wall surface, the side wall surface of the interlayer insulating film 0403, and the side wall surface of the second metal film 0409 are exposed.

In addition to the first wiring A0407, a first wiring B0410 used as a third electrode is formed.

The ion conductive layer 0404 is provided so as to contact only the upper surface of the first wiring B0410 and a part of the side surface of the patterned three-layer structure. Of the side wall surface of the first metal film 0408, a portion in contact with the ion conductive layer 0404 functions as the first electrode 0401. Of the side wall surface of the second metal film 0409, a portion in contact with the ion conductive layer 0404 is It functions as the second electrode 0402. The ion conductive layer 0404 serves as a medium for conducting metal ions. Therefore, the “three-terminal switch” of the second embodiment is configured by using the first wiring B 0410, the first electrode 0401, the ion conductive layer 0404, and the second electrode 0402 that are used as the third electrode. .

The conductive material constituting the second metal film 0409 includes tantalum (Ta), titanium (Ti), tungsten (W), ruthenium (Ru), platinum (Pt), nickel (Ni), tantalum nitride (TaN), Titanium nitride (TiN) is suitable, and a laminate of these may be employed. In particular, Ru is preferable.

An interlayer insulating film 0403 is formed on the upper surface of the second metal film 0409. The interlayer insulating film 0403 is an insulating material that can be vapor-deposited and formed using an insulating material that does not exhibit ion conductivity, such as a SiC film, a SiCN film, a SiN film, and a stacked structure thereof. can do.

The conductive material constituting the first metal film 0408 includes tantalum (Ta), titanium (Ti), tungsten (W), ruthenium (Ru), platinum (Pt), nickel (Ni), tantalum nitride (TaN), Titanium nitride (TiN) is suitable, and a laminate of these may be employed. In particular, Ru is preferable. The first metal film 0408 made of these conductive materials. A top surface of the interlayer insulating film 0403 is formed by a sputtering method, a laser ablation method, or a plasma CVD method.

In the configuration of the “three-terminal switch” of the second embodiment shown in FIG. 4, the planar shape of the patterned three-layer structure is a circle, and therefore the planar shape of the first metal film 0408 and the second metal film 0409. Is round. Therefore, the first electrode 0401 made of the side wall surface of the first metal film 0408 and the second electrode 0402 made of the side wall surface of the second metal film 0409 also have the same curvature.

The ion conductive layer 0404 is formed using a sputtering method, a laser ablation method, or a plasma CVD method in order to be in contact with the surface of the first wiring B 0410 and the side surface of the three-layer structure having a curvature. As a material of the ion conductive layer 0404, it is necessary to select a material having a high conductivity of metal ions and capable of vapor phase etching processing in an LSI production line.

One of the candidate materials that can be used to fabricate the ion conductive layer 0404 is chalcogenide GeSbTe, which is used as a material for the phase change layer in the phase change element. As a means for forming the ion conductive layer 0404 made of GeSbTe on the side surface of the three-layer structure having a curvature, there is a method of forming a film by sputtering using a GeSbTe sintered target. Specifically, using a Ge ₂ Sb ₂ Te ₅ target, a film is formed of a film made of Ge ₂ Sb ₂ Te _5.

Another material candidate that can be used for manufacturing the ion conductive layer 0404 is a SIOCH-based material containing silicon, oxygen, carbon, and hydrogen, which is formed by a plasma CVD method. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material (cyclic organosiloxane) vapor is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is supplied directly to the reaction chamber through another line.

The first wiring B0410 used as the third electrode is made of a metal material capable of supplying metal ions to the ion conductive layer 0404. For example, the main metal is Cu, and an alloy with Al or the like may be used.

(Switching operation)
A driving method during ON / OFF operation (switching) in the “3-terminal switch” of the second embodiment shown in FIG. 4 will be described.

(A) ON operation (transition process from OFF state to ON state)
At the time of transition from the OFF state to the ON state, for example, the first electrode 0401 and the second electrode 0402 are grounded, and a positive voltage (+ V _ON > 0 V) is applied to the first wiring B 0410 used as the third electrode. . At the interface between the first wiring B0410 and the ion conductive layer 0404, the metal is ionized (oxidized) by the electric field caused by the applied positive voltage, and the generated metal ions are supplied into the ion conductive layer 0404. The supplied metal ions migrate to the second electrode 0402 and the first electrode 0401 side by an electric field in the ion conductive layer 0404. The migrated metal ions receive electrons injected into the ion conductive layer 0404 from the second electrode 0402 and the first electrode 0401 and are reduced to metal. By this electrochemical reaction, metal deposition starts from the lower end of the surface of the second electrode 0402 and the surface (side wall surface) of the first electrode 0401. Formation of the metal bridge 0405 proceeds in accordance with the lines of electric force between the first electrode 0401, the second electrode 0402, and the first wiring B0410 (third electrode). A metal bridge 0405 formed from the lower surface of the surface of the second electrode 0402 and the surface (side wall surface) of the first electrode 0401 extends along the side wall surface of the interlayer insulating film 0403 on the surface (side wall surface) of the second electrode 0402. When a conduction path that connects the upper end and the lower end of the surface (side wall surface) of the first electrode 0401 is formed, the resistance value between the first electrode 0401 and the second electrode 0402 becomes low, and the ON state is established.

As a bias at the time of transition from the OFF state to the ON state, the first wiring B0410 (third electrode) is grounded, and a negative voltage (−V _ON <0 V) is applied to the first electrode 0401 and the second electrode 0402. But it ’s okay.

(B) OFF operation (transition process from ON state to OFF state)
On the other hand, at the time of transition from the ON state to the OFF state, for example, the first electrode B401 and the second electrode 0402 are grounded, and a negative voltage (−V _OFF < 0V) is applied. First, on the first electrode 0401 and second electrode 0402 side, ionization (oxidation) of the metal constituting the metal bridge 0405 and elution of metal ions into the ion conductive layer 0404 proceed (dissolution reaction). The metal ions eluted in the ion conductive layer 0404 migrate toward the surface of the first wiring B0410 (third electrode) by the electric field formed in the ion conductive layer 0404. Metal ions are reduced by electrons injected into the ion conductive layer 0404 from the surface of the first wiring B0410 (third electrode). The generated metal is re-deposited on the surface of the first wiring B0410 (third electrode). The dissolution of the metal bridge 0405 proceeds, and a conduction path that connects the upper end of the surface (sidewall surface) of the second electrode 0402 and the lower end of the surface (sidewall surface) of the first electrode 0401 along the side wall surface of the interlayer insulating film 0403. When the current stops, the resistance value between the first electrode 0401 and the second electrode 0402 becomes high resistance, and the OFF state is entered.

The bias at the time of transition from the ON state to the OFF state is also a mode in which the first wiring B0410 (third electrode) is grounded and a positive voltage (+ V _OFF > 0 V) is applied to the first electrode 0401 and the second electrode 0402. good.

The side surfaces of the first electrode 0401 and the second electrode 0402 constituting the “three-terminal switch” of the second embodiment shown in FIG. 4 have curvature, so that the first electrode 0401 is turned on during the ON / OFF operation (switching). The electric field formed in the ion conductive layer by the switching voltage applied between the second electrode 0402 and the first wiring B0410 (third electrode) is concentrated on this curvature portion, and switching operation is stable and has little variation. Is obtained.

(First embodiment)
A three-terminal switching element according to the first embodiment according to the second embodiment of the present invention will be described.

The three-terminal switching element of the first embodiment is formed inside a multilayer wiring layer provided in the semiconductor device. FIG. 5 shows the structure of the three-terminal switching element 0520 of the first embodiment, which is formed inside a multilayer wiring layer provided in the semiconductor device.

The multilayer wiring layer provided in the semiconductor device illustrated in FIG. 5 includes a plug 0506 electrically connected to the first metal film 0508, a second wiring 0512 and a second metal film 0509 that are integrally formed with the plug 0506. The first wiring A 0507 connected and the first wiring B 0522 used as the third electrode are provided. A barrier insulating film 0503 is sandwiched between the first metal film 0508 and the second metal film 0509. The three-layer structure including the first metal film 0508, the barrier insulating film 0503, and the second metal film 0509 has a hard mask. By using 0518 as an etching mask and performing etching, it is patterned in the same planar shape. On the side surface of the patterned three-layer structure, the side wall portion of the first metal film 0508, the side wall portion of the barrier insulating film 0503, and the side wall portion of the second metal film 0509 are exposed.

A part of the side surface of the patterned three-layer structure is in contact with the ion conductive layer 0504, and the side wall portion of the first metal film 0508 in contact with the ion conductive layer 0504 is used as the first electrode 0501. A side wall portion of the second metal film 0509 that is in contact with the ion conductive layer 0504 is used as the second electrode 0502. A part of the surface of the first wiring B 0522 used as the third electrode is in contact with the ion conductive layer 0504 in the opening of the barrier insulating film 0505.

The three-terminal switch 0520 includes a first wiring B 0522, a first electrode 0501, a second electrode 0502, and an ion conductive layer 0504 that are used as a third electrode.

The multilayer wiring layer includes an interlayer insulating film 0513, a barrier insulating film 0505, a protective insulating film 0523, an ion conductive layer 0504, a barrier insulating film 0514, an interlayer insulating film 0515, an interlayer insulating film 0516, and a barrier insulating layer on the semiconductor substrate 0519. An insulating stacked body in which the films 0517 are stacked in this order is included.

A second wiring 0512 is embedded in a wiring groove formed in the interlayer insulating film 0516, and pilot holes formed in the interlayer insulating film 0515, the barrier insulating film 0514, the ion conductive layer 0504, the protective insulating film 0523, and the hard mask 0518. The plug 0506 is embedded in the second wiring 0512 and the plug 0506, and the second wiring 0520 and the side surface and bottom surface of the plug 0506 are covered with the second barrier metal 0511.

A barrier insulating film 0514 is provided between the ion conductive layer 0504 and the interlayer insulating film 0515, and diffusion of metal ions from the ion conductive layer 0504 to the interlayer insulating film 0515 is performed using the barrier insulating film 0514. It is preventing. In addition, a protective insulating film 0523 and a barrier insulating film 0505 are provided between the ion conductive layer 0504 and the interlayer insulating film 0513. The protective insulating film 0523 and the barrier insulating film 0505 are used to start from the ion conductive layer 0504. Diffusion of metal ions into the interlayer insulating film 0513 is prevented.

The barrier insulating film 0505 covers the upper surface of the interlayer insulating film 0513, the upper surface of the first wiring A0507, and the upper surface of the first wiring B0522, and the upper surface portion of the first wiring A0507 and the upper surface portion of the first wiring B0522. An opening is formed in the. The second metal film 0509 and the upper surface portion of the first wiring A0507 are electrically connected through this opening. Further, the ion conductive layer 0504 is in contact with the surface of the first wiring B 0522 through the opening. Therefore, the barrier insulating film 0505 prevents contact between the second metal film 0509 and the upper surface of the interlayer insulating film 0513. As a result, diffusion of the metal constituting the second metal film 0509 into the interlayer insulating film 0513 is prevented.

The three-terminal switch 0520 includes a second metal film 0509, a barrier insulating film 0503, and a first metal film 0501 that form the processed second electrode 0502 on the opened barrier insulating film 0505. 0508, a hard mask 0508, a protective insulating film 0523, and a first wiring B 0522 also serving as a third electrode under another opened barrier insulating film 0505. The upper surface of the protective insulating film 0523, the hard mask 0518, and the first metal An ion conductive layer 0504 is formed so as to cover the side surfaces of the film 0508, the barrier insulating film 0503, the second metal film 0509, and the upper surface of the first wiring B 0522, and the barrier insulating film 0514 is formed thereon. Yes.

In the three-terminal switch 0520, the first metal film 0508 constituting the first electrode 0501 is electrically connected through the plug 0506 and the second barrier metal 0511. In addition, the second metal film 0509 constituting the second electrode 0502 is electrically connected to the first wiring A 0507 and the first barrier metal A 0510 through an opening opened in the barrier insulating film 0205. The third electrode also serves as the first wiring B0522.

The first metal film 0508 constituting the first electrode 0501 has a two-layer structure, and the same material as the second barrier metal 0511 is used for the surface (upper layer) in contact with the plug 0506. By doing so, the second barrier metal 0511 of the plug 0506 and the upper layer of the first metal film 0508 constituting the first electrode 0501 are integrated to reduce contact resistance and to improve reliability by improving adhesion. The improvement of property can be realized.

The semiconductor substrate 0519 is a substrate on which a semiconductor element is formed. As the semiconductor substrate 0519, for example, a substrate such as a silicon substrate, a single crystal substrate, an SOI (Silicon-on-Insulator) substrate, a TFT (Thin-Film Transistor) substrate, a liquid crystal manufacturing substrate, or the like can be used.

The interlayer insulating film 0513 is an insulating film formed over the semiconductor substrate 0519. As the interlayer insulating film 0513, for example, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of SiO _{2 or} a silicon oxide film can be used. The interlayer insulating film 0513 may be a stack of a plurality of insulating films. In the interlayer insulating film 0513, a wiring groove for embedding the first wiring A0507 and the first wiring B0522 is formed, and the first wiring A0507 is inserted into the wiring groove via the first barrier metal A0510. A first wiring layer B0522 is embedded via B0521.

The first wiring A 0507 and the first wiring B 0522 are wirings embedded in the wiring trench formed in the interlayer insulating film 0513 via the first barrier metal A 0510 and the first barrier metal B 0521. The first wiring A 0507 is in direct contact with the second metal film 0509 that forms the second electrode 0502. The first wiring B 0522 is in direct contact with the ion conductive layer 0504. The first wiring A0507 and the first wiring B0522 are made of Cu, but may be alloyed with Al. The first wiring B 0522 functions as a third electrode that supplies Cu ions into the three-terminal ion conductive layer 0504.

The first barrier metal A0510 and the first barrier metal B0521 cover the side and bottom surfaces of the wiring in order to prevent the metal constituting the first wiring A0507 and the first wiring B0522 from diffusing into the interlayer insulating film 0513 and the lower layer. It is a conductive film having a barrier property. As the first barrier metal A0510 and the first barrier metal B0521, for example, when the first wiring A0507 and the first wiring B0522 are made of a metal element whose main component is Cu, tantalum (Ta), tantalum nitride (TaN) Alternatively, a refractory metal such as titanium nitride (TiN) or tungsten carbonitride (WCN), a nitride thereof, or a laminated film thereof can be used.

The barrier insulating film 0505 is formed over the interlayer insulating film 0513 including the first wiring A0507 and the first wiring B0522, and prevents the metal (for example, Cu) constituting the first wiring A0507 and the first wiring B0522 from being oxidized. It has a role of preventing diffusion of the metal constituting the first wiring A 0507 and the first wiring B 0522 into the ion conductive layer 0504. For the barrier insulating film 0505, for example, a SiC film, a SiCN film, a SiN film, a stacked structure thereof, or the like can be used.

The barrier insulating film 0505 has an opening over the first wiring A0507 and the first wiring B0522. In the opening of the barrier insulating film 0505, the first wiring A0507 and the second metal film 0209 constituting the second electrode 0502 are in contact with each other, and the first wiring B0522 and the ion conductive layer 0504 are in contact with each other. The opening of the barrier insulating film 0505 is formed in each region of the first wiring A0507 and the first wiring B0522. The wall surface of the opening of the barrier insulating film 0505 is a tapered surface that becomes wider as the distance from the first wiring A 0507 and the first wiring B 0522 increases. The taper angle θ _{taper of the} wall surface of the opening of the barrier insulating film 0510 is set to 85 ° or less (θ _taper ≦ 85 °) with respect to the upper surface of the first wiring 0207.

The second electrode 0502 and the first electrode 0501 are electrodes that transmit signals in the three-terminal switch 0520, and are in direct contact with the ion conductive layer 0504. The second metal film 0509 constituting the second electrode 0502 is not easily ionized, and a metal that is difficult to diffuse or conduct is used for the ion conductive layer 0504. For example, Pt, Ru, etc. can be used. The second electrode 0502 is a side wall portion of the second metal film 0509. The first metal film 0508 constituting the first electrode 0501 is composed of two layers of different metals. The first electrode 0501 is a side wall portion of the first metal film 0508. The lower layer in contact with the barrier insulating film 0503 and the ion conductive layer 0504 is not easily ionized, and a metal that is difficult to diffuse or conduct is used for the ion conductive layer 0504. For example, Pt, Ru, etc. can be used. Further, the upper layer of the first metal film 0508 constituting the first electrode 0501 is in contact with the hard mask 0518 and the ion conductive layer 0504. The upper layer of the first metal film 0508 has a role of protecting the lower layer. That is, when the upper layer protects the lower layer, damage to the lower layer during the process can be suppressed, and the switching characteristics of the three-terminal switch 0520 can be maintained. For this upper layer, for example, Ta, Ti, W, Al or nitrides thereof can be used. The upper layer of the first metal film 0507 is electrically connected to the plug 0506 through the second barrier metal 0511.

The barrier insulating film 0503 is provided between the first metal film 0508 constituting the first electrode 0501 and the second metal film 0509 constituting the second electrode 0502. The barrier insulating film 0503 has a role of insulating the first metal film 0508 constituting the first electrode 0501 and the second metal film 0509 constituting the second electrode 0502 so that they are not short-circuited. For the barrier insulating film 0503, for example, a SiC film, a SiCN film, a SiN film, a stacked structure thereof, or the like can be used.

The ion conductive layer 0504 is a film in which metal ions (Cu ions) can move in an electric field. For the ion conductive layer 0504, a material whose resistance is changed by the action of metal (diffusion, ion transmission, etc.) included in the ion conductive layer can be used. When the resistance change of the three-terminal switch 0520 is performed by forming / disappearing a metal bridge, a film is used in which metal ions supplied from the first wiring B 0522 that also serves as the third electrode can conduct ions. Metal ions are supplied as Cu ions from the first wiring B 0522 that also serves as the third electrode. A pilot hole for embedding the plug 0514 is formed in the barrier insulating film 0514, and the plug 0506 is embedded in the pilot hole via the second barrier metal 0511.

One of the candidate materials that can be used to fabricate the ion conductive layer 0504 is chalcogenide GeSbTe, which is used as a material for the phase change layer in the phase change element. As a means for forming the ion conductive layer 0504 made of GeSbTe on the side surface of the three-layer structure having a curvature, there is a method of performing sputtering film formation using a GeSbTe sintered target. Specifically, using a Ge ₂ Sb ₂ Te ₅ target, a film is formed of a film made of Ge ₂ Sb ₂ Te _5.

Another material candidate that can be used for manufacturing the ion conductive layer 0504 is a SIOCH-based material containing silicon, oxygen, carbon, and hydrogen, which is formed by a plasma CVD method. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material (cyclic organosiloxane) vapor is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is supplied directly to the reaction chamber through another line.

The hard mask 0518 is a film serving as a hard mask when the first metal film 0508 constituting the first electrode 0501, the barrier insulating film 0503, and the second metal film 0509 constituting the second electrode 0502 are etched. For the hard mask 0518, for example, a SiN film, a SiO ₂ film, or a laminate thereof can be used.

The protective insulating film 0523 has the side surfaces of the first metal film 0508 forming the first electrode 0501, the barrier insulating film 0503, and the second metal film 0509 forming the second electrode 0502 on the first wiring B 0522 that also serves as the third electrode. The barrier insulating film 0503 is a film used for protection from ashing treatment when opening. Since oxygen plasma is used for the ashing treatment, the first electrode 0501 and the second electrode 0509 which are side surfaces of the first metal film 0508 and the second metal film 0509 are oxidized. As the protective insulating film 0523, for example, a SiN film, a SiCN film, or a stacked layer thereof can be used.

The barrier insulating film 0514 is an insulating film having a function of preventing diffusion of metal ions (Cu ions) contained in the ion conductive layer 0504 into the interlayer insulating film 0515 without damaging the three-terminal switch 0520. As the barrier insulating film 0514, for example, a SiN film, a SiCN film, or the like can be used. The barrier insulating film 0514 is preferably made of the same material as the barrier insulating film 0505. A pilot hole for embedding the plug 0506 is formed in the barrier insulating film 0514, and the plug 0506 is embedded in the pilot hole via the second barrier metal 0511.

The interlayer insulating film 0515 is an insulating film formed over the barrier insulating film 0514. For the interlayer insulating film 0515, for example, a SiO ₂ , SiOC film or the like can be used. The interlayer insulating film 0515 may be a stack of a plurality of insulating films. The interlayer insulating film 0515 may be made of the same material as the interlayer insulating film 0513 and the interlayer insulating film 0516. A pilot hole for embedding the plug 0506 is formed in the interlayer insulating film 0515, and the plug 0506 is embedded in the pilot hole via the second barrier metal 0511.

The interlayer insulating film 0516 is an insulating film formed over the interlayer insulating film 0515. As the interlayer insulating film 0516, for example, a SiO ₂ , a SiOC film, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of SiO ₂ can be used. The interlayer insulating film 0516 may be a stack of a plurality of insulating films. The interlayer insulating film 0516 may be formed of the same material as the interlayer insulating film 0515 and the interlayer insulating film 0513. Alternatively, the interlayer insulating film 0516 and the interlayer insulating film 0515 can be formed using different insulating materials, and a significant difference can be provided in the etching characteristics. In the interlayer insulating film 0516, a wiring groove for embedding the second wiring 0512 is formed, and the second wiring 0512 is embedded in the wiring groove via the second barrier metal 0511.

The second wiring 0512 is a wiring embedded in the wiring trench formed in the interlayer insulating film 0516 via the second barrier metal 0511. The second wiring 0512 is integrated with the plug 0506. The plug 0506 is embedded in the prepared holes formed in the interlayer insulating film 0515, the barrier insulating film 0514, and the hard mask 0518 via the second barrier metal 0511. The plug 0506 is electrically connected to the first metal film 0508 constituting the first electrode 0501 through the second barrier metal 0511. For example, Cu can be used for the second wiring 0512 and the plug 0506.

The second barrier metal 0511 has the second wiring 0512 and the plug 0506 in order to prevent the metal constituting the second wiring 0512 (including the plug 0506) from diffusing into the interlayer insulating film 0516, the interlayer insulating film 0515, or the lower layer. It is the electroconductive film which has the barrier property which coat | covers the side surface and bottom face of this. For example, when the second wiring 0512 and the plug 0506 are made of a metal element whose main component is Cu, the second barrier metal 0512 includes a refractory metal such as Ta, TaN, TiN, and WCN, a nitride thereof, and the like. Alternatively, or a stacked film thereof can be used.

The barrier insulating film 0517 is formed on the interlayer insulating film 0516 including the second wiring 0512, prevents oxidation of the metal (for example, Cu) constituting the second wiring 0517, and configures the second wiring 0512 to the upper layer. It is an insulating film having a role of preventing metal diffusion. For the barrier insulating film 0517, for example, a SiC film, a SiCN film, a SiN film, a stacked structure thereof, or the like can be used.

(Switching operation)
A driving method during the switching operation of the three-terminal switch of the first embodiment shown in FIG. 5 will be described.

(A) ON operation (transition process from OFF state to ON state)
First, the second electrode 0502 is electrically connected to the second electrode 0502. The second metal film 0509 is electrically connected to the first electrode 0501 through the first wiring 0507. The first metal film 0508, the plug 0506, and the second wiring 0512 are grounded. Further, when a positive voltage (+ V _ON > 0 V) is applied to the first wiring B 0522 also serving as the third electrode, metal ions (Cu ions) are diffused from the first wiring B 0522 also serving as the third electrode into the ion conductive layer 0504, Migrate to the first electrode 0501 and the second electrode 0502 side. The migrated metal ions receive electrons from the first electrode 0501 and the second electrode 0502, and a metal bridge 0524 is deposited by an electrochemical reaction. As a result, the resistance value between the first electrode 0501 and the second electrode 0502 becomes low resistance, and is turned on.

In the transition to the ON state, the first wiring B 0522 also serving as the third electrode may be grounded, and a negative voltage (−V _ON <0 V) may be applied to the first electrode 0501 and the second electrode 0502.

(B) OFF operation (transition process from ON state to OFF state)
On the other hand, the second electrode 0502 is electrically connected to the second electrode 0502. The second metal film 0509 is electrically connected to the first electrode 0501 through the first wiring 0507. When a negative voltage (= V _OFF <0 V) is applied to the first wiring B 0522 that is grounded via the first metal film 0508, the plug 0506, and the second wiring 0512 and also serves as the third electrode, the dissolution reaction of the metal bridge 0521 The metal bridge 0524 becomes metal ions (Cu ions) and is dispersed in the ion conductive layer 0504. As a result, the resistance value between the first electrode 0501 and the second electrode 0502 becomes high resistance, and transitions to the OFF state.

In the transition to the OFF state, the first wiring B 0522 also serving as the third electrode may be grounded, and a positive voltage (+ V _OFF > 0 V) may be applied to the first electrode 0501 and the second electrode 0502.

Since the side surfaces of the first electrode 0501 and the second electrode 0502 have curvature, an electric field concentrates on the curvature portion when switching voltage is applied when switching between the ON state and the OFF state, and the variation is stable and small in variation. Switching operation is obtained.

(Manufacturing process)
In a semiconductor device comprising a variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate, the three-terminal switching element of the first embodiment shown in FIG. A manufacturing process for manufacturing a nonvolatile switching element will be described. FIGS. 6A and 6B are cross-sectional views schematically showing an example of the manufacturing process of the three-terminal switching element of the first embodiment. FIG. 6A is a diagram illustrating steps 1 to 5 in the manufacturing process, and FIG. 6B is a diagram illustrating steps 6 to 10 in the manufacturing process.

(Process 1)
An interlayer insulating film 0613 (eg, 300 nm thick SiO ₂ , 150 nm thick SiOCH, 100 nm thick SiO ₂ ) is deposited on a semiconductor substrate 0619 (eg, a substrate on which a semiconductor element is formed), and then lithography is performed. Using a method (including photoresist formation, dry etching, and photoresist removal), a wiring groove is formed in the interlayer insulating film 0513, and then the first barrier metal A0610 and the first barrier metal B0621 (for example, The first wiring A0607 and the first wiring B0622 (for example, Cu) are embedded via TaN / Ta and a film thickness of 5 nm / 5 nm. The interlayer insulating film 0613 can be formed by a plasma CVD method. The first wiring A0607 and the first wiring B0622 are formed, for example, by forming a first barrier metal A0610 and a first barrier metal B0621 (for example, a stacked film of TaN / Ta) by a PVD method, and after forming a Cu seed by a PVD method, It can be formed by embedding Cu in the wiring trench by an electrolytic plating method, after heat treatment at a temperature of 200 ° C. or higher, and then removing excess copper other than in the wiring trench by a CMP method. As a method for forming such a series of copper wirings, a general method in this technical field can be used. Here, the CMP (Chemical Mechanical Polishing) method is to planarize the unevenness on the wafer surface that occurs during the multilayer wiring formation process by bringing the polishing liquid into contact with a rotating polishing pad while flowing the polishing liquid over the wafer surface. Is the method. By polishing excess copper embedded in the wiring trench, a buried wiring (damascene wiring) is formed, or by planarizing the interlayer insulating film 0613 by polishing.

(Process 2)
A barrier insulating film 0605 (eg, SiN, film thickness of 30 nm) is formed over the surface of the first wiring A 0607 and the first wiring B 0622 and the interlayer insulating film 0613. Here, the barrier insulating film 0605 can be formed by a plasma CVD method. The thickness of the barrier insulating film 0605 is preferably about 10 nm to 50 nm. A hard mask 0625 (eg, SiO ₂ ) is formed over the barrier insulating film 0605. At this time, the hard mask 0625 is preferably made of a material different from the barrier insulating film 0605 from the viewpoint of maintaining a high etching selectivity in the dry etching process, and may be an insulating film or a conductive film. For the hard mask 0625, for example, SiO ₂ , SiN, SiCN, TiN, Ti, Ta, TaN or the like can be used, and a laminated body of SiCN / SiO ₂ can be used.

(Process 3)
Using a photoresist (not shown) on the hard mask 0625, an opening is patterned only on the first wiring A0607, and an opening pattern is formed on the hard mask 0625 by dry etching using the photoresist as a mask. Thereafter, the photoresist is removed by oxygen plasma ashing or the like. At this time, dry etching is not necessarily stopped on the upper surface of the barrier insulating film 0605, and may reach the inside of the barrier insulating film 0605.

(Process 4)
Using the hard mask 0625 as an etching mask, the barrier insulating film 0605 exposed from the opening of the hard mask 0625 is etched back (dry etching), whereby an opening is formed in the barrier insulating film 0605. The first wiring A0607 is exposed in the opening of the barrier insulating film 0605, and then an organic stripping process is performed with an amine-based stripping solution or the like, thereby removing copper oxide formed on the exposed surface of the first wiring A0607. Etching byproducts generated during etch back are removed. In the etch back of the barrier insulating film 0605, the wall surface of the opening of the barrier insulating film 0605 can be tapered by using reactive dry etching. In reactive dry etching, a gas containing fluorocarbon can be used as an etching gas. The hard mask 0625 is preferably completely removed during the etch back, but may remain as it is when it is an insulating material. The shape of the opening in the barrier insulating film 0605 can be a circle, and the diameter of the circle can be 30 nm to 500 nm. The oxide on the surface of the first wiring 0607 is removed by RF (Radio Frequency) etching using a non-reactive gas. As the non-reactive gas, helium or argon can be used.

(Process 5)
On the opened barrier insulating film 0605, a second metal film 0609 (for example, Ru 10 nm), a barrier insulating film 0603 (for example, SiCN film, film thickness 10 nm), and a first metal film 0608 (for example, Ru 10 nm and Ta 10 nm are deposited in this order). Are deposited in order. Further, a hard mask 0618 (eg, SiN film, film thickness 30 nm) and a hard mask 0626 (eg, SiO ₂ film, film thickness 100 nm) are stacked in this order. In Step 5, the hard mask 0618 and the hard mask 0626 can be formed by a plasma CVD method. In step 5, the first metal film 0608 and the second metal film 0609 are formed by sputtering. Further, a photoresist (not shown) for patterning the hard mask 0626 is formed. After that, using the photoresist as a mask, the hard mask 0626 is dry-etched until the hard mask 0618 appears, and then oxygen plasma ashing is performed. The photoresist is removed using organic stripping. Depending on the exposure pattern of the photoresist mask, the planar shape of the hard mask 0626 (the shape viewed from above) is a circle or an ellipse. Alternatively, the exposure pattern of the photoresist mask itself is rectangular or square, and when the hard mask 0626 is etched, the corners are removed by side etching. As a result, the planar shape of the hard mask 0626 has a curvature. It may be allowed.

(Step 6)
Next, using the hard mask 0626 as a mask, the hard mask 0618, the first metal film 0608, the barrier insulating film 0603, and the second metal film 0609 are continuously dry-etched to form the first electrode 0601 and the second electrode 0602. . At this time, the hard mask 0626 is preferably completely removed during the etch back, but may remain as it is. In step 6, for example, when the upper layer of the first metal film 0608 is Ta, it can be processed by Cl ₂ RIE, and when the lower layer of the first metal film 0608 and the second metal film are Ru, Cl can be processed. RIE processing can be performed with a mixed gas of ₂ / O ₂ . By using such a hard mask RIE method, the first metal film 0608 and the second metal film 0609 can be etched without being exposed to oxygen plasma ashing for resist removal. When the resist used for patterning the hard mask 0626 is oxidized with oxygen plasma after processing, the first metal film 0608 is covered with the hard mask 0626. In the resist stripping step, when the irradiation with oxidation plasma is performed, the first metal film 0608 covered with the hard mask 0626 is not oxidized even if the irradiation time is increased. In step 6, the etching recipe may be adjusted so that the planar shapes of the hard mask 0618, the first metal film 0608, the barrier insulating film 0603, and the second metal film 0609 have curvature.

(Step 7)
Next, a protective insulating film 0623 (eg, SiCN film, 30 nm) and a hard mask 0627 (eg, SiO 2) are in contact with the hard mask 0618, the first electrode 0601, the barrier insulating film 0603, the second electrode 0602, and the barrier insulating film 0605. A film, 50 nm) is deposited. In Step 7, the protective insulating film 0623 and the hard mask 0627 can be formed by a plasma CVD method. Further, a photoresist (not shown) for patterning the hard mask 0627 is formed, and then the hard mask 0627 is dry-etched, and then the photoresist is removed using oxygen plasma ashing and organic peeling.

(Process 8)
Using the hard mask 0627 as a mask, the barrier insulating film 0605 exposed from the opening of the hard mask 0627 is etched back (dry etching), whereby an opening is formed in the barrier insulating film 0605 and the opening of the barrier insulating film 0605 is formed. Then, the first wiring B0622 is exposed, and then an organic stripping process is performed with an amine-based stripping solution or the like to remove copper oxide formed on the exposed surface of the first wiring B0622, and etching that has occurred at the time of etch back Remove double products. At this time, the openings of the hard mask 0627 are the side surfaces of the first metal film 0608 and the second metal film 0609 where the first electrode 0601 and the second electrode 0602 are formed, the side surfaces of the barrier insulating film 0603, and the side surfaces of the hard mask 0618. Since the hard mask 0618 and the first metal film 0608 become hard masks at the time of etch back, the side surface of the opening portion of the barrier insulating film 0605 is self-aligned so that the first electrode 0601 is closer to the first wiring A 0607 side. And the second electrode 0602. In the etch back of the barrier insulating film 0605, the wall surface of the opening of the barrier insulating film 0605 can be tapered by using reactive dry etching. In reactive dry etching, a gas containing fluorocarbon can be used as an etching gas. The hard mask 0627 is preferably completely removed during the etch back, but may remain as it is when it is an insulating material. The shape of the opening in the barrier insulating film 0605 has a curvature, and the maximum length of the opening in the planar direction is 30 nm to 500 nm. Further, the oxide on the surface of the first wiring 0607 is removed by RF (Radio Frequency) etching using a non-reactive gas. As the non-reactive gas, helium or argon can be used.

(Step 9)
Next, silicon, oxygen, and carbon are used as the ion conductive layer 0604 so as to be in contact with the protective insulating film 0623, the hard mask 0618, the first electrode 0601, the barrier insulating film 0605, the second electrode 0602, the barrier insulating film 0603, and the first wiring B 0622. Then, an SIOCH-based ion conductive layer containing hydrogen is formed to a thickness of about 20 nm to 80 nm by CVD. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is directly supplied to the reaction chamber by another line. The temperature is preferably about 250 ° C to 350 ° C. Next, SiN or SiCN is formed to a thickness of 30 nm as the barrier insulating film 0614 over the ion conductive layer 0604. In step 9, the barrier insulating film 0614 can be formed by a plasma CVD method. For example, it is preferable to use a SiN film in which a mixed gas of SiH ₄ / N ₂ is formed by high-density plasma. Although the ion conductive layer 0604 remains in a region other than the three-terminal switch element 0620, it functions as an insulating film and does not affect the operation of the three-terminal switch and the multilayer wiring. In step 9, a SiO ₂ film having a thickness of 300 nm is formed as an interlayer insulating film 0615 on the barrier insulating film 0614. Further, in order to eliminate the level difference caused by the three-terminal switch 0620, the interlayer insulating film 0615 is flattened by polishing about 170 nm by a CMP method. The interlayer insulating film 0615 is desirably formed of SiO ₂ using high-density plasma in order to reliably fill the steps of the three-terminal switch element 0620.

(Process 10)
Next, an interlayer insulating film 0616 (for example, a laminate of SiOC and SiO ₂ having a low relative dielectric constant) is deposited on the interlayer insulating film 0615, and then a pilot hole for the plug 0606 and a wiring groove for the second wiring 0612 are formed. Is formed by dry etching, and a second wiring 0612 (for example, Cu) and a plug are inserted into the wiring groove and the prepared hole through a second barrier metal 0611 (for example, TaN / Ta) using a copper dual damascene wiring process. 0606 (for example, Cu) is formed at the same time, and then a barrier insulating film 0617 (for example, a SiCN film) is deposited on the interlayer insulating film 0616 including the second wiring 0612. In step 10, the second wiring 0612 and the plug 0606 are formed by, for example, forming a second barrier metal 0611 (for example, a stacked film of TaN / Ta) by the PVD method, forming a Cu seed by the PVD method, and then performing electrolytic plating. It can be formed by embedding copper in the wiring groove by the method, after heat treatment at a temperature of 200 ° C. or higher, and then removing excess copper other than in the wiring groove by the CMP method. As a method for forming such a series of copper wirings, a general method in this technical field can be used. In step 10, by making the upper layer of the second barrier metal 0611 and the first metal film 0608 the same material, the contact resistance between the plug 0606 and the first metal film 0608 is reduced, and the element performance is improved (in the ON state). The resistance of the three-terminal switch can be reduced). In Step 10, the interlayer insulating film 0616 and the barrier insulating film 0617 can be formed by a plasma CVD method. In step 10, when forming the prepared hole of the plug 0606, it reaches the upper layer of the first metal film 0608, and the material of the upper layer of the first metal film 0608 functions as an etching stopper material. For dry etching of the pilot hole for the plug 0606 and the wiring groove for the second wiring 0612, a fluorocarbon-based gas is used.

(Second embodiment)
A three-terminal switching element according to a second embodiment according to the second embodiment of the present invention will be described.

The three-terminal switching element of the second embodiment is formed inside a multilayer wiring layer provided in the semiconductor device. FIG. 7 shows the structure of the three-terminal switching element 0720 according to the second embodiment, which is formed in the multilayer wiring layer provided in the semiconductor device.

A three-terminal switch 0720 is formed inside a multilayer wiring layer provided in the semiconductor device. The multilayer wiring layer includes a plug 0706 electrically connected to the first metal film 0708 constituting the first electrode 0701 and a first wiring A0707 connected to the second metal film 0709 constituting the second electrode 0702. The ion conductive layer 0704 is in contact with the first electrode 0701 and the second electrode 0702, and includes a barrier insulating film 0703 between the first metal film 0708 and the second metal film 0709, and the ion conductive layer 0704 and the interlayer insulating film. Between 0715, the barrier insulating film 0714 exists. The plug 0706 is connected to the second wiring 0712. Further, the first wiring B 0722 also serves as the third electrode, and is in contact with the ion conductive layer 0704 through the opening of the barrier insulating film 0705.

The multilayer wiring layer is formed by stacking an interlayer insulating film 0713, a barrier insulating film 0705, an ion conductive layer 0704, a barrier insulating film 0714, an interlayer insulating film 0715, an interlayer insulating film 0716, and a barrier insulating film 0717 over the semiconductor substrate 0719. An insulating laminate.

A second wiring 0712 is embedded in a wiring groove formed in the interlayer insulating film 0716, and a plug 0706 is embedded in pilot holes formed in the interlayer insulating film 0715, the barrier insulating film 0714, the ion conductive layer 0704, and the hard mask 0718. The second wiring 0712 and the plug 0706 are integrated with each other, and the side surfaces and bottom surfaces of the second wiring 0720 and the plug 0706 are covered with the second barrier metal 0711.

On the opened barrier insulating film 0705, the processed second electrode 0702, the second metal film 0709, the barrier insulating film 0703, the first electrode 0701, the first metal film 0708, the hard mask 0718, There is a first wiring B 0722 also serving as a third electrode under another opened barrier insulating film 0705, and the upper surface of the hard mask 0718, the first metal film 0708, the barrier insulating film 0703, the second metal film 0709, the barrier An ion conductive layer 0704 is formed so as to cover a side surface of the insulating film 0723 and an upper surface of the first wiring B 0722, and a barrier insulating film 0714 is formed thereon. The first wiring B 0722 also serving as the third electrode is electrically separated from the first metal film 0708 also serving as the first electrode 0701 by the barrier insulating film 0723.

The first metal film 0708 constituting the first electrode 0701 is electrically connected to the plug 0706 via the second barrier metal 0711. In addition, the second metal film 0709 constituting the second electrode 0702 is electrically connected to the first wiring A0707 and the first barrier metal A0710 through the opening opened in the barrier insulating film 0705. The third electrode also serves as the first wiring B0722.

The first metal film 0708 constituting the first electrode 0701 has a two-layer structure, and the surface (upper layer) in contact with the plug 0706 is made of the same material as the second barrier metal 0711. In this way, the second barrier metal 0711 of the plug 0706 and the upper layer of the first metal film 0708 constituting the first electrode 0701 of the three-terminal switch 0720 are integrated, reducing the contact resistance, and the adhesiveness. Improvement of reliability can be realized by improving the above.

The semiconductor substrate 0719 is a substrate on which a semiconductor element is formed. As the semiconductor substrate 0719, for example, a substrate such as a silicon substrate, a single crystal substrate, an SOI (Silicon on Insulator) substrate, a TFT (Thin Film Transistor) substrate, or a liquid crystal manufacturing substrate can be used.

The interlayer insulating film 0713 is an insulating film formed over the semiconductor substrate 0719. As the interlayer insulating film 0713, for example, SiO ₂ , a low dielectric constant film (for example, a SiOCH film) having a lower dielectric constant than that of a silicon oxide film can be used. The interlayer insulating film 0713 may be a stack of a plurality of insulating films. In the interlayer insulating film 0713, a wiring groove for embedding the first wiring A0707 and the first wiring B0722 is formed, and the first wiring A0707 is inserted into the wiring groove via the first barrier metal A0710. The first wiring layer B0722 is embedded via B0721.

The first wiring A0707 and the first wiring B0722 are wirings embedded in the wiring trench formed in the interlayer insulating film 0713 via the first barrier metal A0710 and the first barrier metal B0721. The first wiring A0707 is in direct contact with the second metal film 0709 forming the second electrode 0702. The first wiring B 0722 is in direct contact with the ion conductive layer 0704. The first wiring A0707 and the first wiring B0722 are made of Cu, but may be alloyed with Al. The first wiring B 0722 functions as a third electrode for supplying Cu ions into the three-terminal ion conductive layer 0704.

The first barrier metal A0710 and the first barrier metal B0721 cover the side and bottom surfaces of the wiring in order to prevent the metal constituting the first wiring A0707 and the first wiring B0722 from diffusing into the interlayer insulating film 0713 or the lower layer. It is a conductive film having a barrier property. For the first barrier metal A0710 and the first barrier metal B0721, for example, when the first wiring A0707 and the first wiring B0722 are made of a metal material containing Cu as a main component, tantalum (Ta), tantalum nitride (TaN) Alternatively, a refractory metal such as titanium nitride (TiN) or tungsten carbonitride (WCN), a nitride thereof, or a laminated film thereof can be used.

The barrier insulating film 0705 is formed on the surface of the first wiring A0707 and the first wiring B0722, the interlayer insulating film 0713, and prevents oxidation of the metal (for example, Cu) constituting the first wiring A0707 and the first wiring B0722. , Has a role of preventing diffusion of the metal constituting the first wiring A0707 and the first wiring B0722 into the ion conductive layer 0704. For the barrier insulating film 0705, for example, a SiC film, a SiCN film, a SiN film, and a stacked structure thereof can be used.

The barrier insulating film 0705 has an opening over the first wiring A0707 and the first wiring B0722. In the opening of the barrier insulating film 0705, the first wiring A0707 and the second metal film 0709 constituting the second electrode 0702 are in contact with each other, and the first wiring B0722 and the ion conductive layer 0704 are in contact with each other. The opening of the barrier insulating film 0705 is formed in each region of the first wiring A0707 and the first wiring B0722. The wall surface of the opening of the barrier insulating film 0705 has a tapered surface that becomes wider as the distance from the first wiring A0707 and the first wiring B0722 increases. The taper angle θ _{taper of the} wall surface of the opening of the barrier insulating film 0710 is set to 85 ° or less (θ _taper ≦ 85 °) with respect to the upper surface of the first wiring 0207.

The second electrode 0702 and the first electrode 0701 are electrodes that transmit signals in the three-terminal switch 0720, and are in direct contact with the ion conductive layer 0704. The second metal film 0709 constituting the second electrode 0702 is not easily ionized, and a metal that is difficult to diffuse or conduct is used for the ion conductive layer 0704. For example, Pt, Ru, etc. can be used. The second electrode 0702 is a side wall portion of the second metal film 0709. The first metal film 0708 constituting the first electrode 0701 is composed of two layers of different metals. The first electrode 0701 is a side wall portion of the first metal film 0708. The lower layer in contact with the barrier insulating film 0703 and the ion conductive layer 0704 is not easily ionized, and a metal that is difficult to diffuse or conduct is used for the ion conductive layer 0704. For example, Pt, Ru, etc. can be used. Further, the upper layer of the first metal film 0708 constituting the first electrode 0701 is in contact with the hard mask 0718 and the ion conductive layer 0704. The upper layer of the first metal film 0708 has a role of protecting the lower layer. That is, when the upper layer protects the lower layer, damage to the lower layer during the process can be suppressed, and the switching characteristics of the three-terminal switch 0720 can be maintained. For this upper layer, for example, Ta, Ti, W, Al or nitrides thereof can be used. The upper layer of the first metal film 0707 is electrically connected to the plug 0706 through the second barrier metal 0711.

The barrier insulating film 0723 is provided between the first wiring B 0722 that also serves as the third electrode and the second metal film 0709 that constitutes the second electrode 0702. The barrier insulating film 0723 has a role of insulating the first wiring B 0722 serving also as the third electrode and the second metal film 0709 constituting the second electrode 0702 so as not to be short-circuited. For the barrier insulating film 0723, for example, a SiC film, a SiCN film, a SiN film, a stacked structure thereof, or the like can be used.

The barrier insulating film 0703 is provided between the first metal film 0708 constituting the first electrode 0701 and the second metal film 0709 constituting the second electrode 0702. The barrier insulating film 0703 has a role of insulating the first metal film 0708 constituting the first electrode 0701 and the second metal film 0709 constituting the second electrode 0702 so that they are not short-circuited. For the barrier insulating film 0703, for example, a SiC film, a SiCN film, a SiN film, a stacked structure thereof, or the like can be used.

The ion conductive layer 0704 is a film in which metal ions (Cu ions) can move in an electric field. For the ion conductive layer 0704, a material whose resistance is changed by the action (diffusion, ion transmission, etc.) of the metal included in the ion conductive layer can be used. When the resistance change of the three-terminal switch 0720 is performed by forming / disappearing a metal bridge, a film that can conduct ions of metal ions supplied from the first wiring B 0722 also serving as the third electrode is used. Metal ions are supplied as Cu ions from the first wiring B 0722 that also serves as the third electrode. A pilot hole for embedding the plug 0714 is formed in the barrier insulating film 0714, and the plug 0706 is embedded in the pilot hole via the second barrier metal 0711.

One of the material candidates that can be used to fabricate the ion conductive layer 0704 is chalcogenide GeSbTe, which is used in the phase change element as a material for the phase change layer. As a means for forming the ion conductive layer 0704 made of GeSbTe on the side surface of the three-layer structure having a curvature, there is a method of performing sputtering film formation using a GeSbTe sintered target. Specifically, using a Ge ₂ Sb ₂ Te ₅ target, a film is formed of a film made of Ge ₂ Sb ₂ Te _5.

Another material candidate that can be used for manufacturing the ion conductive layer 0704 is a SIOCH-based material containing silicon, oxygen, carbon, and hydrogen, which is formed by a plasma CVD method. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material (cyclic organosiloxane) vapor is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is supplied directly to the reaction chamber through another line.

The hard mask 0718 is a film serving as a hard mask when the first metal film 0708 constituting the first electrode 0701, the barrier insulating film 0703, and the second metal film 0709 constituting the second electrode 0702 are etched. For the hard mask 0718, for example, a SiN film, a SiO ₂ film, or a laminate thereof can be used.

The barrier insulating film 0714 is an insulating film having a function of preventing detachment and diffusion of oxygen and metal contained in the ion conductive layer 0704 without damaging the three-terminal switch 0720. As the barrier insulating film 0714, for example, a SiN film, a SiCN film, or the like can be used. The barrier insulating film 0714 is preferably made of the same material as the barrier insulating film 0705. A pilot hole for embedding the plug 0706 is formed in the barrier insulating film 0714, and the plug 0706 is embedded in the pilot hole via the second barrier metal 0711.

The interlayer insulating film 0715 is an insulating film formed over the barrier insulating film 0714. For the interlayer insulating film 0715, for example, a SiO ₂ , SiOC film or the like can be used. The interlayer insulating film 0715 may be a stack of a plurality of insulating films. The interlayer insulating film 0715 may be formed of the same material as the interlayer insulating films 0713 and 0716. A pilot hole for embedding the plug 0706 is formed in the interlayer insulating film 0715, and the plug 0706 is embedded in the pilot hole via the second barrier metal 0711.

The interlayer insulating film 0716 is an insulating film formed over the interlayer insulating film 0715. As the interlayer insulating film 0716, for example, a SiO ₂ , a SiOC film, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of SiO ₂ can be used. The interlayer insulating film 0716 may be formed of the same material as the interlayer insulating film 0715 and the interlayer insulating film 0713. Alternatively, the interlayer insulating film 0716 and the interlayer insulating film 0715 can be formed using different insulating materials, and a significant difference can be provided in the etching characteristics. The interlayer insulating film 0716 may be formed of the same material as the interlayer insulating films 0715 and 0713. In the interlayer insulating film 0716, a wiring groove for embedding the second wiring 0712 is formed, and the second wiring 0712 is embedded in the wiring groove via the second barrier metal 0711.

The second wiring 0712 is a wiring embedded in the wiring trench formed in the interlayer insulating film 0716 with the second barrier metal 0711 interposed therebetween. The second wiring 0712 is integrated with the plug 0706. The plug 0706 is embedded in a prepared hole formed in the interlayer insulating film 0715, the barrier insulating film 0714, and the hard mask 0718 via the second barrier metal 0711. The plug 0706 is electrically connected to the first metal film 0708 constituting the first electrode 0701 through the second barrier metal 0711. For example, Cu can be used for the second wiring 0712 and the plug 0706.

The second barrier metal 0711 includes side surfaces of the second wiring 0712 and the plug 0706 in order to prevent the metal constituting the second wiring 0712 (including the plug 0706) from diffusing into the interlayer insulating films 0716 and 0715 and the lower layer. It is a conductive film having a barrier property covering the bottom surface. For example, when the second wiring 0712 and the plug 0706 are made of a metal element whose main component is Cu, the second barrier metal 0712 includes a refractory metal such as Ta, TaN, TiN, and WCN, a nitride thereof, and the like. Alternatively, or a stacked film thereof can be used.

The barrier insulating film 0717 is formed on the interlayer insulating film 0716 including the second wiring 0712, prevents oxidation of the metal (for example, Cu) constituting the second wiring 0717, and configures the second wiring 0712 to the upper layer. It is an insulating film having a role of preventing metal diffusion. For the barrier insulating film 0717, for example, a SiC film, a SiCN film, a SiN film, a stacked structure thereof, or the like can be used.

(Switching operation)
A driving method during the switching operation of the three-terminal switch of the second embodiment shown in FIG. 7 will be described.

(A) ON operation (transition process from OFF state to ON state)
First, the second electrode 0702 is electrically connected to the second electrode 0702. The second metal film 0709 is electrically connected to the first electrode 0701 via the first wiring 0707. The first metal film 0708, the plug 0706, and the second wiring 0712 are grounded. Further, when a positive voltage (+ V _ON > 0 V) is applied to the first wiring B 0722 also serving as the third electrode, metal ions (Cu ions) diffuse from the first wiring B 0722 also serving as the third electrode into the ion conductive layer 0704, Migrate to the first electrode 0701 and second electrode 0702 side. The migrated metal ions receive electrons from the first electrode 0701 and the second electrode 0702, and a metal bridge 0724 is deposited by an electrochemical reaction. As a result, the resistance value between the first electrode 0701 and the second electrode 0702 becomes low resistance and is turned on.

In the transition to the ON state, the first wiring B 0722 also serving as the third electrode may be grounded, and a negative voltage (−V _ON <0 V) may be applied to the first electrode 0701 and the second electrode 0702.

(B) OFF operation (transition process from ON state to OFF state)
A second metal film 0709 in which the second electrode 0702 is electrically connected to the second electrode 0702 is connected to the first electrode 0701 through the first wiring 0707, and the first electrode 0701 is electrically connected to the first electrode 0701. The metal film 0708, the plug 0706, and the second wiring 0712 are grounded. When a negative voltage (−V _OFF <0 V) is applied to the first wiring B 0722 also serving as the third electrode, the dissolution reaction of the metal bridge 0721 proceeds, and the metal bridge 0724 becomes metal ions (Cu ions), and the ion conductive layer Disperse in 0704. As a result, the resistance value between the first electrode 0701 and the second electrode 0702 becomes high resistance and transitions to the OFF state.

In the transition to the OFF state, the first wiring B 0722 also serving as the third electrode may be grounded, and a positive voltage (+ V _OFF > 0 V) may be applied to the first electrode 0701 and the second electrode 0702.

Since the side surfaces of the first electrode 0701 and the second electrode 0702 have curvature, when a switching voltage is applied during switching between the ON state and the OFF state, the electric field concentrates on the curvature portion, and switching is stable and has little variation. Operation is obtained.

(Manufacturing process)
In a semiconductor device comprising a variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate, the three-terminal switching element of the second embodiment shown in FIG. A manufacturing process for manufacturing a nonvolatile switching element will be described. FIGS. 8A and 8B are cross-sectional views schematically showing an example of the manufacturing process of the three-terminal switching element of the second embodiment. FIG. 8A is a diagram showing steps 1 to 6 in the manufacturing process, and FIG. 8B is a diagram showing steps 7 to 10 in the manufacturing process.

(Process 1)
An interlayer insulating film 0813 (eg, 300 nm thick SiO ₂ , 150 nm thick SiOCH, 100 nm thick SiO ₂ ) is deposited on a semiconductor substrate 0819 (eg, a substrate on which a semiconductor element is formed), and then lithography is performed. A wiring trench is formed in the interlayer insulating film 0813 using a method (including photoresist formation, dry etching, and photoresist removal), and then a first barrier metal A0810 and a first barrier metal B0821 (for example, The first wiring A0807 and the first wiring B0922 (for example, Cu) are embedded through (TaN / Ta, film thickness 5 nm / 5 nm). The interlayer insulating film 0813 can be formed by a plasma CVD method. For example, the first wiring A0807 and the first wiring B0822 are formed by forming a first barrier metal A0810 and a first barrier metal B (for example, a TaN / Ta laminated film) by a PVD method, and after forming a Cu seed by a PVD method, Cu can be formed by embedding Cu in the wiring trench by an electrolytic plating method, after heat treatment at a temperature of 200 ° C. or higher, and then removing excess copper other than in the wiring trench by a CMP method. As a method for forming such a series of copper wirings, a general method in this technical field can be used. Here, the CMP (Chemical Mechanical Polishing) method is to planarize the unevenness on the wafer surface that occurs during the multilayer wiring formation process by bringing the polishing liquid into contact with a rotating polishing pad while flowing the polishing liquid over the wafer surface. Is the method. By polishing excess copper embedded in the wiring trench, a buried wiring (damascene wiring) is formed, or by planarizing the interlayer insulating film 0813 by polishing.

(Process 2)
A barrier insulating film 0805 (for example, SiN, film thickness of 30 nm) is formed on the upper surface of the first wiring A0807 and the first wiring B0822, and on the interlayer insulating film 0913. Here, the barrier insulating film 0805 can be formed by a plasma CVD method. The thickness of the barrier insulating film 0805 is preferably about 10 nm to 50 nm. A hard mask 0825 (eg, SiO ₂ ) is formed over the barrier insulating film 0805. At this time, the hard mask 0825 is preferably made of a material different from the barrier insulating film 0805 from the viewpoint of maintaining a high etching selectivity in the dry etching process, and may be an insulating film or a conductive film. For the hard mask 0825, for example, SiO ₂ , SiN, SiCN, TiN, Ti, Ta, TaN or the like can be used, and a laminated body of SiCN / SiO ₂ can be used.

(Process 3)
An opening is patterned only on the first wiring B 0822 using a photoresist (not shown) on the hard mask 0825, and an opening pattern is formed on the hard mask 0825 by dry etching using the photoresist as a mask. Thereafter, the photoresist is removed by oxygen plasma ashing or the like. At this time, dry etching is not necessarily stopped on the upper surface of the barrier insulating film 0805, and may reach the inside of the barrier insulating film 0805.

Using the hard mask 0825 as a mask, the barrier insulating film 0805 exposed from the opening of the hard mask 0825 is etched back (dry etching), whereby an opening is formed in the barrier insulating film 0805 and the opening of the barrier insulating film 0805 is formed. Then, the first wiring B0822 is exposed, and thereafter, an organic stripping process is performed with an amine-based stripping solution to remove copper oxide formed on the exposed surface of the first wiring B0822, and etching that occurs at the time of etch back Remove double products. In the etch back of the barrier insulating film 0805, the wall surface of the opening of the barrier insulating film 0805 can be tapered by using reactive dry etching. In reactive dry etching, a gas containing fluorocarbon can be used as an etching gas. The hard mask 0825 is preferably completely removed during the etch back, but may remain as it is when it is an insulating material. The shape of the opening in the barrier insulating film 0805 can be a circle, and the diameter of the circle can be 30 nm to 500 nm. The oxide on the surface of the first wiring B0822 is removed by RF (Radio-Frequency; high frequency) etching using a non-reactive gas. As the non-reactive gas, helium or argon can be used.

(Process 4)
A barrier insulating film 0823 having a thickness of about 10 nm is formed over the opened barrier insulating film 0823 and the first wiring B 0822. For the barrier insulating film 0823, a SiC film or a SiCN film can be used.

(Process 5)
A hard mask 0826 (eg, SiO ₂ ) is formed over the barrier insulating film 0823. At this time, the hard mask 0826 is preferably made of a material different from the barrier insulating film 0823 from the viewpoint of maintaining a high etching selectivity in the dry etching process, and may be an insulating film or a conductive film. For the hard mask 0826, for example, SiO ₂ , SiN, SiCN, TiN, Ti, Ta, TaN or the like can be used, and a laminated body of SiCN / SiO ₂ can be used.

(Step 6)
An opening is patterned only on the first wiring A0807 using a photoresist (not shown) on the hard mask 0825, and an opening pattern is formed on the hard mask 0826 by dry etching using the photoresist as a mask. Thereafter, the photoresist is removed by oxygen plasma ashing or the like. At this time, the dry etching is not necessarily stopped on the upper surface of the barrier insulating film 0823, and may reach the inside of the barrier insulating film 0823 and the barrier insulating film 0805.

Using the hard mask 0826 as a mask, the barrier insulating film 0823 and the barrier insulating film 0805 exposed from the opening of the hard mask 0826 are etched back (dry etching) to form openings in the barrier insulating film 0823 and the barrier insulating film 0805. Then, the first wiring A0807 is exposed from the openings of the barrier insulating film 0823 and the barrier insulating film 0805, and thereafter, organic stripping treatment is performed with an amine-based stripping solution or the like to form the exposed surface of the first wiring A0807. The removed copper oxide is removed, and etching byproducts generated during the etch back are removed. In the etch-back of the barrier insulating film 0823 and the barrier insulating film 0805, the wall surfaces of the openings of the barrier insulating film 0823 and the barrier insulating film 0805 can be tapered by using reactive dry etching. In reactive dry etching, a gas containing fluorocarbon can be used as an etching gas. The hard mask 0825 is preferably completely removed during the etch back, but may remain as it is when it is an insulating material. The shape of the opening in the barrier insulating film 0823 and the barrier insulating film 0805 can be circular, and the diameter of the circle can be 30 nm to 500 nm. The oxide on the surface of the first wiring A0807 is removed by RF (Radio-Frequency) using non-reactive gas. As the non-reactive gas, helium or argon can be used.

(Step 7)
A second metal film 0809 (for example, Ru3 nm and Ta5 nm are deposited in this order), a barrier insulating film 0803 (for example, a SiN film, a film thickness of 5 nm to 10 nm) on the opened barrier insulating film 0823 and the first wiring A0807; A first metal film 0808 (for example, Ta 3 nm, Ru 5 nm, and Ta 25 nm are deposited in this order) is sequentially deposited. Further, a hard mask 0818 (for example, SiN film, film thickness of 30 nm) and a hard mask 0827 (for example, SiO ₂ film, film thickness of 100 nm) are stacked in this order. In Step 7, the hard masks 0818 and 0827 can be formed by a plasma CVD method. In step 7, the first metal film 0808 and the second metal film 0809 are formed by sputtering. Further, a photoresist (not shown) for patterning the hard mask 0827 is formed. After that, using the photoresist as a mask, the hard mask 0826 is dry-etched until the hard mask 0818 appears, and then oxygen plasma ashing is performed. The photoresist is removed using organic stripping. Depending on the exposure pattern of the photoresist mask, the planar shape of the hard mask 1109 (the shape seen from the top surface) is a circle or an ellipse. Alternatively, the exposure pattern of the photoresist mask itself is rectangular or square, and when the hard mask 0827 is etched, the corners are removed by side etching. As a result, the planar shape of the hard mask 0827 has a curvature. It may be allowed.

(Process 8)
Next, using the hard mask 0827 as a mask, the hard mask 0818, the first metal film 0808, the barrier insulating film 0803, the second metal film 0809, and the barrier insulating film 0823 are continuously dry-etched to form the first electrode 0801 and the second electrode An electrode 0802 is formed and the first wiring A0807 is exposed. At this time, the hard mask 0827 is preferably completely removed during the etch-back, but may remain as it is. In step 8, the Ta films of the first metal film 0808 and the second metal film 0809 can be processed by Cl ₂ RIE, and the Ru film can be processed by RIE with a mixed gas of Cl ₂ / O ₂ . By using such a hard mask RIE method, the first metal film 0808 and the second metal film 0809 can be etched without being exposed to oxygen plasma ashing for resist removal. In addition, when the resist used for patterning the hard mask 0827 is oxidized with oxygen plasma after processing, the first metal film 0808 is covered with the hard mask 0827. In the resist stripping process, when the irradiation with the oxidation plasma is performed, the first metal film 0808 covered with the hard mask 0827 is not oxidized even if the irradiation time is increased.

Further, when the barrier insulating film 0823 is processed, etching is performed using a fluorocarbon-based gas (for example, CF ₄ ). In Step 7, the etching recipe may be adjusted so that the planar shapes of the hard mask 0818, the first metal film 0808, the barrier insulating film 0803, the second metal film 0809, and the barrier insulating film 0823 have a curvature.

(Step 9)
Next, an ion conductive layer 0804 is formed in contact with the protective insulating film 0823, the hard mask 0818, the first electrode 0801, the barrier insulating film 0805, the second electrode 0802, the barrier insulating film 0803, the barrier insulating film 0823, and the first wiring B0822. Then, an SIOCH ion conductive material containing silicon, oxygen, carbon, and hydrogen is formed to a thickness of about 20 nm to 80 nm by a CVD method. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is directly supplied to the reaction chamber by another line. The temperature is preferably about 250 ° C to 350 ° C. Next, SiN or SiCN is formed to a thickness of 30 nm as the barrier insulating film 0814 over the ion conductive layer 0804. In Step 9, the barrier insulating film 0814 can be formed by a plasma CVD method. For example, it is preferable to use a SiN film in which a mixed gas of SiH ₄ / N ₂ is formed by high-density plasma. Although the ion conductive layer 0804 remains in a region other than the three-terminal switch element 0820, it functions as an insulating film and does not affect the operation of the three-terminal switch and the multilayer wiring. Step 9 is to deposit 300 nm of SiO ₂ as an interlayer insulating film 0815 on the barrier insulating film 0814. Further, in order to eliminate the level difference caused by the three-terminal switch 0820, the interlayer insulating film 0815 is flattened by polishing by about 170 nm by a CMP method. The interlayer insulating film 0815 is desirably formed of SiO ₂ using high-density plasma in order to reliably fill the step of the three-terminal switch element 0820.

(Process 10)
Next, an interlayer insulating film 0816 (for example, a laminate of SiOC and SiO ₂ having a low relative dielectric constant) is deposited on the interlayer insulating film 0815, and then a pilot hole for the plug 0806 and a wiring groove for the second wiring 0812 are formed. Is formed by dry etching, and a second wiring 0812 (for example, Cu) and a plug are inserted into the wiring groove and the prepared hole through a second barrier metal 0811 (for example, TaN / Ta) using a copper dual damascene wiring process. 0806 (for example, Cu) is formed at the same time, and then a barrier insulating film 0817 (for example, a SiCN film) is deposited over the interlayer insulating film 0816 including the second wiring 0812. In step 10, the second wiring 0812 and the plug 0806 are formed by, for example, forming a second barrier metal 0811 (for example, a TaN / Ta laminated film) by the PVD method, forming a Cu seed by the PVD method, and then performing electrolytic plating. It can be formed by embedding copper in the wiring groove by the method, after heat treatment at a temperature of 200 ° C. or higher, and then removing excess copper other than in the wiring groove by the CMP method. As a method for forming such a series of copper wirings, a general method in this technical field can be used. In step 10, the upper layer of the second barrier metal 0811 and the first metal film 0808 are made of the same material, so that the contact resistance between the plug 0806 and the first metal film 0808 is reduced and the device performance is improved (in the ON state). The resistance of the three-terminal switch can be reduced). In Step 10, the interlayer insulating film 0816 and the barrier insulating film 0817 can be formed by a plasma CVD method. In step 10, when forming the prepared hole of the plug 0806, it reaches the upper layer of the first metal film 0808, and the material of the upper layer of the first metal film 0808 functions as an etching stopper material. A fluorocarbon gas is used for dry etching of the prepared hole for the plug 0806 and the wiring groove for the second wiring 0812.

(Third embodiment)
The third embodiment of the metal bridge type switching element according to the present invention is a metal bridge type switching element adopting the configuration of a “three-terminal switch” described below.

The configuration of the “3-terminal switch” employed in the metal bridge type switching element according to the third embodiment of the present invention will be described. FIG. 9 is a cross-sectional view schematically showing an example of the configuration of the “3-terminal switch” of the third embodiment.

As shown in FIG. 9, the three-terminal switch includes a first metal film 0907 connected to the plug 0906, a first wiring A0902 that also serves as the second electrode, and a first electrode 0901 that is a side surface of the first metal film 0907. And the first wiring A 0902 also serving as the second electrode, the ion conductive layer 0904 in contact with the side surface of the interlayer insulating film 0903, and the first wiring B 0908 also serving as the third electrode in contact with the ion conductive layer 0904. The metal bridge 0905 formed at the time of transition to ON is formed so as to connect the first electrode 0901 and the first wiring layer B0908 that also serves as the second electrode. The ion conductive layer 0904 serves as a medium for conducting metal ions.

The first metal film 0907 constituting the first electrode 0901 is made of tantalum (Ta), titanium (Ti), tungsten (W), ruthenium (Ru), platinum (Pt), nickel (Ni), tantalum nitride (TaN). Titanium nitride (TiN) is suitable, and these layers may be used. Ru is particularly preferable. These metals are formed by sputtering, laser ablation, or plasma CVD.

The planar shape of the first metal film 0907 constituting the first electrode 0901 has a curvature. Therefore, the first electrode 0901 also has a curvature.

The ion conductive layer 0904 is formed by sputtering, laser ablation, or plasma CVD. As a material for the ion conductive layer 0904, it is necessary to select a material having a high metal ion conductivity and which can be processed in an LSI production line.

One of the material candidates that can be used for the production of the ion conductive layer 0904 is chalcogenide GeSbTe, which is used as a material of the phase change layer in the phase change element. As a means for forming the ion conductive layer 0904 made of GeSbTe on the side surface of the multilayer structure having a curvature, there is a method of forming a film by sputtering using a sintered target of GeSbTe. Specifically, using a Ge ₂ Sb ₂ Te ₅ target, a film is formed of a film made of Ge ₂ Sb ₂ Te _5.

Another material candidate that can be used for manufacturing the ion conductive layer 0904 is a SIOCH-based material containing silicon, oxygen, carbon, and hydrogen, which is formed by a plasma CVD method. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material (cyclic organosiloxane) vapor is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is supplied directly to the reaction chamber through another line.

The first wiring A 0902 that also serves as the second electrode and the first wiring B 0908 that also serves as the third electrode are made of a metal that can supply metal ions to the ion conductive layer 0904. For example, the main metal is Cu, and an alloy with Al or the like may be used.

(Switching operation)
A driving method during the switching operation of the three-terminal switch of the third embodiment shown in FIG. 9 will be described.

(A) ON operation (transition process from OFF state to ON state)
First, when the first wiring A0902 that also serves as the first electrode 0901 and the second electrode is grounded and a positive voltage (+ V _ON > 0V) is applied to the first wiring B0908 that also serves as the third electrode, metal ions are generated from the first wiring B0908. It diffuses into the ion conductive layer 0904 and migrates to the first electrode 0901 and the first wiring A0902 side. The migrated metal ions receive electrons from the first electrode 0901 and the first wiring A0902, and a metal bridge 0905 is deposited between the first electrode 0901 and the first wiring A0902 by an electrochemical reaction according to the lines of electric force. As a result, the resistance value between the first electrode 0901 and the first wiring A0902 becomes low, and the device is turned on.

In the transition to the ON state, the first wiring B 0910 that also serves as the third electrode may be grounded, and a negative voltage (−V _ON <0 V) may be applied to the first electrode 0901 and the first wiring A 0902.

(B) OFF operation (transition process from ON state to OFF state)
On the other hand, when the first wiring A0902 also serving as the first electrode 0901 and the second electrode is grounded and a negative voltage (−V _OFF <0V) is applied to the first wiring B0908 also serving as the third electrode, the dissolution reaction of the metal bridge 0905 The metal bridge 0905 becomes metal ions and is dispersed in the ion conductive layer 0904. As a result, the resistance value between the first electrode 0901 and the first wiring A0902 becomes high resistance, and transitions to the OFF state.

In the transition to the OFF state, the first wiring B0710 that also serves as the third electrode may be grounded, and a positive voltage (+ V _OFF > 0 V) may be applied to the first electrode 0901 and the first wiring A0902.

Since the side surface shape of the first electrode 0901 has a curvature, when a switching voltage is applied at the time of switching between the ON state and the OFF state, an electric field concentrates on the curvature portion, and an operation with stable and small variation is obtained.

(First embodiment)
A three-terminal switching element according to the first embodiment according to the third embodiment of the present invention will be described.

The three-terminal switching element of the first embodiment is formed inside a multilayer wiring layer provided in the semiconductor device. FIG. 10 shows the structure of the three-terminal switching element 1020 of the second embodiment, which is formed inside a multilayer wiring layer provided in the semiconductor device.

A three-terminal switch 1020 is formed inside a multilayer wiring layer provided in the semiconductor device. The multilayer wiring layer includes a plug 1006 electrically connected to the first metal film 1008 constituting the first electrode 1001, and a first wiring A1007 constituting the second electrode 1002, and the ion conductive layer 1004 is the first electrode. 1001 and the second electrode 1002, a barrier insulating film 1005 is provided between the first metal film 1008 and the first wiring A 1007, and a barrier insulating film 1014 exists between the ion conductive layer 1004 and the interlayer insulating film 1015. To do. The plug 1006 is connected to the second wiring 1012. Further, the first wiring B1022 also serves as the third electrode, and is in contact with the ion conductive layer 1004 through the opening of the barrier insulating film 1005.

The multilayer wiring layer includes an interlayer insulating film 1013, a barrier insulating film 1005, a protective insulating film 1023, an ion conductive layer 1004, a barrier insulating film 1014, an interlayer insulating film 1015, an interlayer insulating film 1016, and a barrier insulating film on the semiconductor substrate 1019. An insulating stacked body is formed in the order of the film 1017.

A second wiring 1012 is embedded in a wiring groove formed in the interlayer insulating film 1016, and pilot holes formed in the interlayer insulating film 1015, the barrier insulating film 1014, the ion conductive layer 1004, the protective insulating film 1003, and the hard mask 1018. The plug 1006 is embedded in the second wiring 1012 and the plug 1006, and the side surfaces and the bottom surface of the second wiring 1012 and the plug 1006 are covered with the second barrier metal 1011.

In the three-terminal switch 1020, a first metal film 1008, a hard mask 1008, and a protective insulating film 1003 constituting the first electrode 1001 are provided on the opened barrier insulating film 1005. An ion conductive layer 1004 is formed so as to cover the mask 1018, the first metal film 1008, the side surfaces of the barrier insulating film 1005, the upper surface of the first wiring A 1007, and the upper surface of the first wiring B 1022. An insulating film 1014 is formed.

The first metal film 1008 constituting the first electrode 1001 is electrically connected to the plug 1006 via the second barrier metal 1011. In addition, the first wiring A configuring the second electrode 1002 is electrically connected to the first wiring A 1007 and the first barrier metal A 1010 through an opening opened in the barrier insulating film 1005. The third electrode also serves as the first wiring B1022.

The first metal film 1008 constituting the first electrode 1001 has a two-layer structure, and the same material as the second barrier metal 1011 is used for the surface (upper layer) in contact with the plug 1006. By doing so, the second barrier metal 1011 of the plug 1006 and the upper layer of the first metal film 1008 constituting the first electrode 1001 of the three-terminal switch 1020 are integrated, the contact resistance is reduced, and the adhesiveness is reduced. Improvement of reliability can be realized by improving the above.

The semiconductor substrate 1019 is a substrate on which a semiconductor element is formed. As the semiconductor substrate 1019, for example, a silicon substrate, a single crystal substrate, an SOI (Silicon on Insulator) substrate, a TFT (Thin Film Transistor) substrate, a liquid crystal manufacturing substrate, or the like can be used.

The interlayer insulating film 1013 is an insulating film formed on the semiconductor substrate 1019. As the interlayer insulating film 1013, for example, SiO ₂ , a low dielectric constant film (for example, SiOCH film) having a relative dielectric constant lower than that of a silicon oxide film can be used. The interlayer insulating film 1013 may be a stack of a plurality of insulating films. In the interlayer insulating film 1013, a wiring groove for embedding the first wiring A1007 and the first wiring B1022 is formed, and the first wiring A1007 is inserted into the wiring groove via the first barrier metal A1010. The first wiring B1022 is embedded through B1021.

The first wiring A 1007 and the first wiring B 1022 are wirings embedded in the wiring trench formed in the interlayer insulating film 1013 via the first barrier metal A 1010 and the first barrier metal B 1021. The first wiring A1007 also serves as the second electrode 1002. The first wiring B1022 is in direct contact with the ion conductive layer 1004. The first wiring A1007 and the first wiring B1022 are made of Cu, but may be alloyed with Al. The first wiring B1022 functions as a third electrode that supplies Cu ions into the three-terminal ion conductive layer 1004.

The first barrier metal A1010 and the first barrier metal B1021 cover the side and bottom surfaces of the wiring in order to prevent the metal constituting the first wiring A1007 and the first wiring B1022 from diffusing into the interlayer insulating film 1013 or the lower layer. It is a conductive film having a barrier property. In the first barrier metal A1010 and the first barrier metal B1021, for example, when the first wiring 1010 is made of a metal element mainly composed of Cu, tantalum (Ta), tantalum nitride (TaN), titanium nitride (TiN) ), A refractory metal such as tungsten carbonitride (WCN), a nitride thereof, or a laminated film thereof.

The barrier insulating film 1005 is formed on the interlayer insulating film 1013 including the first wiring A1007 and the first wiring B1022, and prevents oxidation of the metal (for example, Cu) constituting the first wiring A1007 and the first wiring B1022, It has a role of preventing diffusion of the metal constituting the first wiring A 1007 and the first wiring B 1022 into the ion conductive layer 1004. As the barrier insulating film 1005, for example, a SiC film, a SiCN film, a SiN film, a stacked structure thereof, or the like can be used.

The barrier insulating film 1005 has an opening over the first wiring A1007 and the first wiring B1022. In the opening of the barrier insulating film 1005, the first wiring A1007 and the first wiring B1022 constituting the second electrode 1002 are exposed, and both are in contact with the ion conductive layer 1004. The opening of the barrier insulating film 1005 is formed in a region including the first wiring A1007 and the first wiring B1022. The wall surface of the opening of the barrier insulating film 1005 is a tapered surface that becomes wider as the distance from the first wiring A1007 and the first wiring B1022 increases. The taper angle θ _{taper of the} wall surface of the opening of the barrier insulating film 1005 is set to 85 ° or less (θ _taper ≦ 85 °) with respect to the upper surfaces of the first wiring A 1007 and the first wiring B 1022.

The first electrode 1001 is an electrode that transmits a signal in the three-terminal switch 1020 and is in direct contact with the ion conductive layer 1004. The first metal film 1008 constituting the first electrode 1001 is composed of two layers of different metals. The first electrode 1001 is a side wall portion of the first metal film 1008. The lower layer in contact with the barrier insulating film 1003 and the ion conductive layer 1004 is not easily ionized, and a metal that is difficult to diffuse or conduct is used for the ion conductive layer 1004. For example, Pt, Ru, etc. can be used. The upper layer of the first metal film 1008 constituting the first electrode 1001 is in contact with the hard mask 1018 and the ion conductive layer 1004. The upper layer of the first metal film 1008 has a role of protecting the lower layer. That is, when the upper layer protects the lower layer, damage to the lower layer during the process can be suppressed, and the switching characteristics of the three-terminal switch 1020 can be maintained. For this upper layer, for example, Ta, Ti, W, Al or nitrides thereof can be used. The upper layer of the first metal film 1007 is electrically connected to the plug 1006 through the second barrier metal 1011.

The ion conductive layer 1004 is a film in which metal ions (Cu ions) can move in an electric field. For the ion conductive layer 1004, a material whose resistance is changed by the action (diffusion, ion transmission, etc.) of the metal included in the ion conductive layer can be used. When the resistance change of the three-terminal switch 1020 is performed by formation / disappearance of a metal bridge, a film capable of conducting ions of metal ions supplied from the first wiring B1022 also serving as the third electrode is used. The metal ions are supplied as Cu ions from the first wiring B1022 that also serves as the third electrode. A pilot hole for embedding the plug 1006 is formed in the barrier insulating film 1014, and the plug 1006 is embedded in the pilot hole via the second barrier metal 1011.

One candidate material that can be used to fabricate the ion conductive layer 1004 is chalcogenide GeSbTe, which is used as a phase change layer material in phase change elements. As a means for forming the ion conductive layer 1004 made of GeSbTe on the side surface of the laminated structure having a curvature, there is a method of performing sputtering film formation using a GeSbTe sintered target. Specifically, using a Ge ₂ Sb ₂ Te ₅ target, a film is formed of a film made of Ge ₂ Sb ₂ Te _5.

Another material candidate that can be used for manufacturing the ion conductive layer 1004 is a SIOCH-based material containing silicon, oxygen, carbon, and hydrogen, which is formed by a plasma CVD method. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material (cyclic organosiloxane) vapor is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is supplied directly to the reaction chamber through another line.

The hard mask 1018 is a film that serves as a hard mask when the first metal film 1008 constituting the first electrode 1001 is etched. For the hard mask 1018, for example, a SiN film, a SiO ₂ film, or a laminate thereof can be used.
The protective insulating film 1023 opens the barrier insulating film 1003 on the first wiring B1022 also serving as the third electrode and the first wiring A1007 also serving as the second electrode on the side surface of the first metal film 1008 constituting the first electrode 1001. At this time, it is a film used for protection from oxidation by resist ashing. Since oxygen plasma is used for the ashing treatment, when exposed to oxygen plasma, the first electrode 1001 that is the side surface of the first metal film 1008 is oxidized. As the protective insulating film 1023, for example, a SiN film, a SiCN film, or a stacked layer thereof can be used.

The barrier insulating film 1014 is an insulating film having a function of preventing the detachment and diffusion of oxygen and metal contained in the ion conductive layer 1004 without damaging the three-terminal switch 1020. As the barrier insulating film 1014, for example, a SiN film, a SiCN film, or the like can be used. The barrier insulating film 1014 is preferably made of the same material as the barrier insulating film 1005. A pilot hole for embedding the plug 1006 is formed in the barrier insulating film 1014, and the plug 1006 is embedded in the pilot hole via the second barrier metal 1011.

The interlayer insulating film 1015 is an insulating film formed on the barrier insulating film 1014. As the interlayer insulating film 1015, for example, a SiO ₂ or SiOC film can be used. The interlayer insulating film 1015 may be a stack of a plurality of insulating films. The interlayer insulating film 1015 may be made of the same material as the interlayer insulating films 1013 and 1016. A pilot hole for embedding the plug 1006 is formed in the interlayer insulating film 1015, and the plug 1006 is embedded in the pilot hole via the second barrier metal 1011.

The interlayer insulating film 1016 is an insulating film formed on the interlayer insulating film 1015. As the interlayer insulating film 1016, for example, a SiO ₂ , a SiOC film, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of SiO ₂ can be used. The interlayer insulating film 1016 may be made of the same material as the interlayer insulating film 1015 and the interlayer insulating film 1013. In addition, the interlayer insulating film 1016 and the interlayer insulating film 1015 can be manufactured using different insulating materials, and a significant difference can be provided in the etching characteristics. The interlayer insulating film 1016 may be made of the same material as the interlayer insulating films 1015 and 1013. In the interlayer insulating film 1016, a wiring groove for embedding the second wiring 1012 is formed, and the second wiring 1012 is embedded in the wiring groove via the second barrier metal 1011.

The second wiring 1012 is a wiring buried in a wiring groove formed in the interlayer insulating film 1016 via the second barrier metal 1011. The second wiring 1012 is integrated with the plug 1006. The plug 1006 is embedded in the prepared holes formed in the interlayer insulating film 1015, the barrier insulating film 1014, and the hard mask 1018 via the second barrier metal 1011. The plug 1006 is electrically connected to the first metal film 1008 constituting the first electrode 1001 through the second barrier metal 1011. For example, Cu can be used for the first wiring 1012 and the plug 1006.

The second barrier metal 1011 is formed on the side surfaces of the second wiring 1012 and the plug 1006 in order to prevent the metal constituting the second wiring 1012 (including the plug 1006) from diffusing into the interlayer insulating films 1016 and 1015 and the lower layer. It is a conductive film having a barrier property covering the bottom surface. For example, when the second wiring 1012 and the plug 1006 are made of a metal element containing Cu as a main component, the second barrier metal 1012 includes a refractory metal such as Ta, TaN, TiN, and WCN, a nitride thereof, and the like. Alternatively, or a stacked film thereof can be used.

The barrier insulating film 1017 is formed on the interlayer insulating film 1016 including the second wiring 1012, prevents oxidation of the metal (for example, Cu) constituting the second wiring 1017, and configures the second wiring 1012 to the upper layer. It is an insulating film having a role of preventing metal diffusion. As the barrier insulating film 1017, for example, a SiC film, a SiCN film, a SiN film, a stacked structure thereof, or the like can be used.

(Switching operation)
A driving method during the switching operation of the three-terminal switch of the first embodiment shown in FIG. 10 will be described.

(A) ON operation (transition process from OFF state to ON state)
First, the first wiring A 1007 that also serves as the second electrode 1002, and the first metal film 1008 that is electrically connected to the first electrode 1001, the plug 1006, and the second wiring 1012 are grounded. Further, when a positive voltage (+ V _ON > 0V) is applied to the first wiring B1022 also serving as the third electrode, metal ions (Cu ions) diffuse from the first wiring B1022 also serving as the third electrode into the ion conductive layer 1004, Migrate to the first electrode 1001 and second electrode 1002 side. The migrated metal ions receive electrons from the first electrode 1001 and the second electrode 1002, and a metal bridge 1009 is deposited by an electrochemical reaction. As a result, the resistance value between the first electrode 1001 and the second electrode 1002 becomes low resistance, and is turned on.

In the transition to the ON state, the first wiring B1022 that also serves as the third electrode may be grounded, and a negative voltage (−V _ON <0 V) may be applied to the first electrode 1001 and the second electrode 1002.

(B) OFF operation (transition process from ON state to OFF state)
On the other hand, the first electrode 1001 is electrically connected to the first electrode 1001 via the first wiring A1007 also serving as the second electrode 1002, the plug 1006, and the second wiring 1012, respectively. Ground. When a negative voltage (−V _OFF <0V) is applied to the first wiring B1022 that also serves as the third electrode, the dissolution reaction of the metal bridge 1009 proceeds, and the metal bridge 1009 becomes metal ions (Cu ions), and the ion conductive layer Disperse in 1004. As a result, the resistance value between the first electrode 1001 and the second electrode 1002 becomes high resistance and transitions to the OFF state.

In the transition to the OFF state, the first wiring B1022 also serving as the third electrode may be grounded, and a positive voltage (+ V _OFF > 0V) may be applied to the first electrode 1001 and the second electrode 1002.

Since the shape of the side surface of the first electrode 1001 has a curvature, when a switching voltage is applied at the time of switching between the ON state and the OFF state, an electric field concentrates on the curvature portion, and an operation with stable and small variation is obtained.

(Manufacturing process)
In a semiconductor device comprising a variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate, the three-terminal switching element of the first embodiment shown in FIG. A manufacturing process for manufacturing a nonvolatile switching element will be described. FIGS. 11A and 11B are cross-sectional views schematically showing an example of the manufacturing process of the three-terminal switching element of the first embodiment. FIG. 11A is a diagram showing steps 1 to 5 in the manufacturing process, and FIG. 11B is a diagram showing steps 6 to 8 in the manufacturing process.

(Process 1)
On the semiconductor substrate 1119 (for example, a substrate on which a semiconductor element is formed), an interlayer insulating film 1113 (for example, 300 nm thick SiO ₂ , 150 nm thick SiOCH, 100 nm thick SiO ₂ ) is deposited, and then Using a lithography method (including photoresist formation, dry etching, and photoresist removal), a wiring groove is formed in the interlayer insulating film 1113, and then the first barrier metal A1110 and the first barrier metal B (for example, , TaN / Ta, film thickness 5 nm / 5 nm) is embedded in the first wiring A1107 and the first wiring B1122 (for example, Cu). The interlayer insulating film 1113 can be formed by a plasma CVD method. The first wiring A1107 and the first wiring B1122 are formed, for example, by forming a first barrier metal A1110 and a first barrier metal B1122 (for example, a TaN / Ta laminated film) by a PVD method, and after forming a Cu seed by a PVD method, It can be formed by embedding Cu in the wiring trench by an electrolytic plating method, after heat treatment at a temperature of 200 ° C. or higher, and then removing excess copper other than in the wiring trench by a CMP method. As a method for forming such a series of copper wirings, a general method in this technical field can be used. Here, the CMP (Chemical Mechanical Polishing) method is to planarize the unevenness of the wafer surface that occurs during the multilayer wiring formation process by bringing the polishing liquid into contact with a rotating polishing pad while flowing the polishing liquid over the wafer surface and polishing it. Is the method. By polishing excess copper embedded in the wiring trench, a buried wiring (damascene wiring) is formed, or by planarizing the interlayer insulating film 1113 by polishing.

(Process 2)
A barrier insulating film 1105 (eg, SiN, film thickness of 30 nm) is formed on the surface of the first wiring A 1107 and the first wiring B 1122 and on the interlayer insulating film 1113. Here, the barrier insulating film 1105 can be formed by a plasma CVD method. The thickness of the barrier insulating film 1105 is preferably about 10 nm to 50 nm.

(Process 3)
A first metal film 1108 (for example, Ru 10 nm and Ta 10 nm are deposited in this order) is deposited on the opened barrier insulating film 1105. Further, a hard mask 1118 (for example, SiN film, film thickness 30 nm) and a hard mask 1109 (for example, SiO ₂ film, film thickness 100 nm) are stacked in this order. In Step 3, the hard mask 1118 and the hard mask 1109 can be formed by a plasma CVD method. In step 3, the first metal film 1108 is formed by sputtering. Further, a photoresist (not shown) for patterning the hard mask 1109 is formed, and then the hard mask 1109 is dry-etched using the photoresist as an etching mask until the hard mask 1118 appears. Thereafter, the photoresist is removed using oxygen plasma ashing and organic peeling. Depending on the exposure pattern of the photoresist mask, the planar shape of the hard mask 1109 (the shape seen from the top surface) is a circle or an ellipse. Alternatively, the exposure pattern itself of the photoresist mask is rectangular or square, and when the hard mask 1109 is etched, the corners are removed by side etching. As a result, the planar shape of the hard mask 1109 has a curvature. It may be allowed.

(Process 4)
Next, using the hard mask 1109 as a mask, the hard mask 1118 and the first metal film 1108 are continuously dry-etched to form the first electrode 1101 and the second electrode 1102. At this time, the hard mask 1109 is preferably completely removed during the etch back, but may remain as it is. In step 4, for example, when the upper layer of the first metal film 1108 is Ta, it can be processed by Cl ₂ RIE, and when the lower layer of the first metal film 1109 is Ru, Cl ₂ / O. RIE processing can be performed with a mixed gas of ₂ . By using such a hard mask RIE method, etching can be performed without exposing the first metal film 1108 to oxygen plasma ashing for resist removal. In addition, when the resist used for patterning the hard mask 1109 is oxidized with oxygen plasma after processing, the first metal film 1108 is covered with the hard mask 1109. In the resist peeling step, when the oxidation plasma is irradiated, the first metal film 1108 covered with the hard mask 1109 is not oxidized even if the irradiation time is long.

In step 4, the etching recipe may be adjusted so that the planar shape of the hard mask 1118 and the first metal film 1108 has a curvature.

(Process 5)
Next, a protective insulating film 1103 (for example, SiCN film, 30 nm) and a hard mask 1123 (for example, SiO 2 film, 50 nm) are deposited so as to be in contact with the sidewalls of the hard mask 1118, the first electrode 1101, and the barrier insulating film 1105. To do. In step 5, the protective insulating film 1103 and the hard mask 1123 can be formed by a plasma CVD method. Further, a photoresist (not shown) for patterning the hard mask 1123 is formed, and then the hard mask 1123 is dry-etched using the photoresist as a mask, and then oxygen plasma ashing and organic peeling are used. Remove the photoresist.

(Step 6)
Using the hard mask 1123 as a mask, the barrier insulating film 1105 exposed from the opening of the hard mask 1123 is etched back (dry etching), whereby an opening is formed in the barrier insulating film 1105. The first wiring A1107 and the first wiring B1122 are exposed in the opening of the barrier insulating film 1105, and then an organic stripping process is performed with an amine-based stripping solution, so that the first wiring A1107 and the first wiring B1122 are exposed. The copper oxide formed on the exposed surface is removed, and the etching byproduct generated during the etch back is removed. At this time, the opening of the hard mask 1123 is closer to the first wiring A 1107 side than the first metal film 1108 on which the first electrode 1101 is formed and the side surfaces of the hard mask 1118. As a result, the hard mask 1118 and the first metal film 1108 become hard masks at the time of etch back, so that the side surface of the opening of the barrier insulating film 1105 is aligned with the side surface of the first electrode 1101 by self-alignment. In the etch back of the barrier insulating film 1105, the wall surface of the opening of the barrier insulating film 1105 can be tapered by using reactive dry etching. In reactive dry etching, a gas containing fluorocarbon can be used as an etching gas. The hard mask 1124 is preferably completely removed during the etch back, but may remain as it is in the case of an insulating material. The shape of the opening in the barrier insulating film 1105 has a curvature, and the maximum length of the opening in the planar direction is 30 nm to 500 nm. Further, oxides on the surfaces of the first wiring A1107 and the first wiring B1122 are removed by RF (Radio Frequency) using a non-reactive gas. As the non-reactive gas, helium or argon can be used. The exposed upper surface of the first wiring A 1107 becomes the second electrode 1102.

(Step 7)
Next, a SIOCH ion conductive material containing silicon, oxygen, carbon, and hydrogen as the ion conductive layer 1104 so as to be in contact with the protective insulating film 1103, the hard mask 1118, the first electrode 1101, the barrier insulating film 1105, and the first wiring B 1122. Are formed by CVD to a thickness of about 20 nm to 80 nm. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is directly supplied to the reaction chamber by another line. The temperature is preferably about 250 ° C to 350 ° C. Next, SiN or SiCN is formed to a thickness of 30 nm as the barrier insulating film 0714 on the ion conductive layer 1104. In step 7, the barrier insulating film 1114 can be formed by a plasma CVD method. For example, it is preferable to use a SiN film formed by high-density plasma of a mixed gas of SiH ₄ / N ₂ . Although the ion conductive layer 1104 remains in a region other than the three-terminal switch element 1120, it functions as an insulating film and does not affect the operation of the three-terminal switch and the multilayer wiring. In step 7, 300 nm of SiO ₂ is deposited as an interlayer insulating film 1115 on the barrier insulating film 1114. Further, in order to eliminate the level difference caused by the three-terminal switch 1120, the interlayer insulating film 1115 is flattened by polishing about 170 nm by a CMP method. The interlayer insulating film 1115 is desirably formed of SiO ₂ using high-density plasma in order to reliably fill the steps of the three-terminal switch element 1120.

(Process 8)
Next, an interlayer insulating film 1116 (for example, a laminate of SiOC and SiO ₂ having a low relative dielectric constant) is deposited on the interlayer insulating film 1115, and then a pilot hole for the plug 1106 and a wiring groove for the second wiring 1112 are deposited. Is formed by dry etching, and a second wiring 1112 (for example, Cu) and a plug are inserted into the wiring groove and the prepared hole through a second barrier metal 1111 (for example, TaN / Ta) using a copper dual damascene wiring process. 1106 (for example, Cu) is formed at the same time, and then a barrier insulating film 1117 (for example, a SiCN film) is deposited on the interlayer insulating film 1116 including the second wiring 1112. In step 8, the second wiring 1112 and the plug 1106 are formed by, for example, forming a second barrier metal 1111 (for example, a TaN / Ta laminated film) by the PVD method, forming a Cu seed by the PVD method, and then performing electrolytic plating. It can be formed by embedding copper in the wiring groove by the method, after heat treatment at a temperature of 200 ° C. or higher, and then removing excess copper other than in the wiring groove by the CMP method. As a method for forming such a series of copper wirings, a general method in this technical field can be used. In step 8, the upper layer of the second barrier metal 1111 and the first metal film 1108 is made of the same material, so that the contact resistance between the plug 1106 and the first metal film 1108 is reduced and the device performance is improved (in the ON state). The resistance of the three-terminal switch can be reduced). In Step 8, the interlayer insulating film 1116 and the barrier insulating film 1117 can be formed by a plasma CVD method. In step 8, when forming the pilot hole for the plug 1106, the pilot hole reaches the upper layer of the first metal film 1108, and the material of the upper layer of the first metal film 1108 functions as an etching stopper material. A fluorocarbon-based gas is used for dry etching of the prepared hole for the plug 1106 and the wiring groove for the second wiring 1112.

(Fourth embodiment)
The fourth embodiment of the metal bridge type switching element according to the present invention is a metal bridge type switching element adopting the configuration of a “three-terminal switch” described below.

The configuration of the “3-terminal switch” employed in the metal bridge type switching element according to the fourth embodiment of the present invention will be described. FIG. 10 is a cross-sectional view schematically showing an example of the configuration of the “3-terminal switch” of the fourth embodiment.

As shown in FIG. 10, the “three-terminal switch” of the fourth embodiment includes a plug 1206 that also serves as the first electrode 1201, a first wiring A1202 that also serves as the second electrode, and a first wiring A1202 that also serves as the second electrode. The ion conductive layer 1204 in contact with the side surface of the interlayer insulating film 1203 and the first wiring B 1207 also serving as the third electrode in contact with the ion conductive layer 1204 are formed. The metal bridge 1205 formed at the time of transition to the ON state is formed so as to connect the first electrode 1201 and the first wiring layer B 1207 that also serves as the second electrode. The ion conductive layer 1204 is supplied from the first wiring B 1207 (third electrode). It becomes a medium for conducting metal ions.

The side surface and the bottom surface of the plug 1206 are covered with the second barrier metal 1311, and the first electrode 1201 is a portion in contact with the ion conductive layer 1204 of the second barrier metal 1311. Tantalum (Ta) and tantalum nitride (TaN) are suitable for the conductive material constituting the second barrier metal 1311, and a laminate of these may be used. The second barrier metal 1311 made of a conductive material is formed using a sputtering method or a plasma CVD method.

The plane (cross section) shape of the pilot hole for the plug 1206 has a curvature. Therefore, the first electrode 0901, which is a portion in contact with the ion conductive layer 1204 of the second barrier metal 1311, also has a curvature.

The ion conductive layer 1204 is formed using a sputtering method, a laser ablation method, or a plasma CVD method. As a material for the ion conductive layer 1204, it is necessary to select a material having a high conductivity of metal ions (Cu ions) and capable of being etched in an LSI production line.

One candidate material that can be used to fabricate the ion conducting layer 1204 is chalcogenide GeSbTe, which is used as a phase change layer material in phase change elements. As a means for forming the ion conductive layer 1204 made of GeSbTe, there is a method of forming a film by sputtering using a sintered target of GeSbTe. Specifically, using a Ge ₂ Sb ₂ Te ₅ target, a film is formed of a film made of Ge ₂ Sb ₂ Te _5.

Another material candidate that can be used for manufacturing the ion conductive layer 1204 is a SIOCH-based material containing silicon, oxygen, carbon, and hydrogen, which is formed by a plasma CVD method. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material (cyclic organosiloxane) vapor is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is supplied directly to the reaction chamber through another line.

The first wiring A 1202 that also serves as the second electrode and the first wiring B 1207 that also serves as the third electrode are made of a metal that can supply metal ions to the ion conductive layer 1204. For example, the main metal is Cu, and an alloy with Al or the like may be used.

(Switching operation)
A driving method during the switching operation of the three-terminal switch of the fourth embodiment shown in FIG. 12 will be described.

(A) ON operation (transition process from OFF state to ON state)
First, when the first wiring A1202 that also serves as the first electrode 1201 and the second electrode is grounded and a positive voltage (+ V _ON > 0 V) is applied to the first wiring 1207 that also serves as the third electrode, metal ions are generated from the first wiring B1207. It diffuses into the ion conductive layer 0904 and migrates to the first electrode 1201 and the first wiring A 1202 side. The migrated metal ions receive electrons from the first electrode 1201 and the first wiring A 1202, and a metal bridge 1205 is deposited between the first electrode 1201 and the first wiring A 1202 by an electrochemical reaction according to the lines of electric force. As a result, the resistance value between the first electrode 1201 and the first wiring A0902 becomes low resistance and is turned on.

In the transition to the ON state, the first wiring B 1207 that also serves as the third electrode may be grounded, and a negative voltage (−V _ON <0 V) may be applied to the first electrode 1201 and the first wiring A 1202.

(B) OFF operation (transition process from ON state to OFF state)
On the other hand, when the first wiring A 1202 that also serves as the first electrode 1201 and the second electrode is grounded and a negative voltage (−V _OFF <0 V) is applied to the first wiring B 1207 that also serves as the third electrode, the dissolution reaction of the metal bridge 0905 occurs. The metal bridge 0905 becomes metal ions and is dispersed in the ion conductive layer 1204. As a result, the resistance value between the first electrode 1201 and the first wiring A 1202 becomes high resistance, and transitions to an off state.

In the transition to the OFF state, the first wiring B 1207 also serving as the third electrode may be grounded, and a positive voltage (+ V _OFF > 0 V) may be applied to the first electrode 1201 and the first wiring A 1202.

Since the plug 1206 also serving as the first electrode 1201 has a curvature, an electric field concentrates on the curvature portion during the switching operation between the ON state and the OFF state, and a switching operation with stable and small variation can be obtained.

(First embodiment)
A three-terminal switching element according to the first embodiment of the fourth embodiment of the present invention will be described.

The three-terminal switching element of the first embodiment is formed inside a multilayer wiring layer provided in the semiconductor device. FIG. 13 shows the structure of the three-terminal switching element of the second embodiment formed inside a multilayer wiring layer provided in the semiconductor device.

A three-terminal switch 1318 is formed in a multilayer wiring layer provided in the semiconductor device. The multilayer wiring layer includes a plug 1306 constituting the first electrode 1301 and a first wiring A1307 constituting the second electrode 1302, and the ion conductive layer 1304 comprises the first wiring constituting the first electrode 1301 and the second electrode 1302. It is in contact with A1307. The plug 1306 is connected to the second wiring 1312. Further, the first wiring B 1303 also serves as the third electrode, and is in contact with the ion conductive layer 1304 at the opening of the barrier insulating film 1305.

The multilayer wiring layer is stacked on the semiconductor substrate 1319 in the order of the interlayer insulating film 1313, the barrier insulating film 1305, the ion conductive layer 1304, the barrier insulating film 1314, the interlayer insulating film 1315, the interlayer insulating film 1316, and the barrier insulating film 1317. An insulating laminate.

A second wiring 1312 is embedded in a wiring groove formed in the interlayer insulating film 1316, and a plug 1306 is embedded in a pilot hole formed in the interlayer insulating film 1315, the barrier insulating film 1314, and the ion conductive layer 1304. The second wiring 1312 and the plug 1306 are integrated with each other, and the side surfaces and the bottom surface of the second wiring 1312 and the plug 1306 are covered with the second barrier metal 1311.

In the three-terminal switch 1318, the plug 1306 constituting the first electrode 1301 is provided on the opened barrier insulating film 1305, the second barrier metal 1311 constituting the plug 1306, the side surface of the barrier insulating film 1305, the first An ion conductive layer 1304 is formed so as to cover the upper surface of the wiring A 1307 and the upper surface of the first wiring B 1303, and a barrier insulating film 1314 is formed thereon.

The plug 1306 constituting the first electrode 1301 is electrically connected through the second barrier metal 1311. Further, the first wiring A 1307 constituting the second electrode 1302 is electrically connected to the first wiring A 1307 and the first barrier metal A 1310 through the opening opened in the barrier insulating film 1305. The third electrode also serves as the first wiring B1303.

The plug 1306 constituting the first electrode 1301 uses the second barrier metal 1311 material as it is.

The semiconductor substrate 1319 is a substrate on which a semiconductor element is formed. As the semiconductor substrate 1319, for example, a silicon substrate, a single crystal substrate, an SOI (Silicon on Insulator) substrate, a TFT (Thin Film Transistor) substrate, a liquid crystal manufacturing substrate, or the like can be used.

The interlayer insulating film 1313 is an insulating film formed on the semiconductor substrate 1319. As the interlayer insulating film 1313, for example, SiO ₂ , a low dielectric constant film (for example, SiOCH film) having a lower relative dielectric constant than that of a silicon oxide film, or the like can be used. The interlayer insulating film 1313 may be a stack of a plurality of insulating films. In the interlayer insulating film 1313, a wiring groove for embedding the first wiring A1307 and the first wiring B1303 is formed, and the first wiring A1307 is inserted into the wiring groove via the first barrier metal A1310. A first wiring B1303 is embedded via B1308.

The first wiring A 1307 and the first wiring B 1303 are wirings embedded in the wiring trench formed in the interlayer insulating film 1313 via the first barrier metal A 1310 and the first barrier metal B 1308. The first wiring A 1307 also serves as the second electrode 1302. The first wiring B1303 is in direct contact with the ion conductive layer 1304. The first wiring A1307 and the first wiring B1303 are made of Cu, but may be alloyed with Al. The first wiring B1303 functions as a third electrode that supplies Cu ions into the ion conductive layer 1304.

The first barrier metal A1310 and the first barrier metal B1308 cover the side and bottom surfaces of the wiring in order to prevent the metal constituting the first wiring A1307 and the first wiring B1303 from diffusing into the interlayer insulating film 1313 or the lower layer. It is a conductive film having a barrier property. For the first barrier metal A1310 and the first barrier metal B1121, for example, when the first wiring is made of a metal element whose main component is Cu, tantalum (Ta), tantalum nitride (TaN), titanium nitride (TiN) Alternatively, a refractory metal such as tungsten carbonitride (WCN), a nitride thereof, or a laminated film thereof can be used.

The barrier insulating film 1305 is formed on the interlayer insulating film 1313 including the first wiring A1307 and the first wiring B1303, and prevents oxidation of the metal (for example, Cu) constituting the first wiring A1307 and the first wiring B1303. It has a role of preventing diffusion of the metal constituting the first wiring A 1307 and the first wiring B 1303 into the ion conductive layer 104. As the barrier insulating film 1305, for example, a SiC film, a SiCN film, a SiN film, a stacked structure thereof, or the like can be used.

The barrier insulating film 1305 has an opening on the first wiring A 1307 and the first wiring B 1303. In the opening of the barrier insulating film 1305, the first wiring A 1307 and the first wiring B 1303 that constitute the second electrode 1302 are exposed, and both are in contact with the ion conductive layer 1304. The opening of the barrier insulating film 1305 is formed in a region including the first wiring A 1307 and the first wiring B 1303. The wall surface of the opening of the barrier insulating film 1305 is a tapered surface that becomes wider as the distance from the first wiring A1307 and the first wiring B1303 increases. The tapered surface of the opening of the barrier insulating film 1305 is set to 85 ° or less with respect to the upper surfaces of the first wiring A 1307 and the first wiring B 1303.

The ion conductive layer 1304 is a film in which metal ions (Cu ions) can move in an electric field. For the ion conductive layer 1304, a material whose resistance is changed by the action (diffusion, ion transmission, etc.) of the metal included in the ion conductive layer can be used. In the case where the resistance change of the three-terminal switch 1318 is performed by formation / disappearance of a metal bridge, a film capable of conducting ions of metal ions supplied from the first wiring B 1322 that also serves as the third electrode is used. Metal ions are supplied as Cu ions from the first wiring B1322 that also serves as the third electrode. A pilot hole for embedding the plug 1306 is formed in the barrier insulating film 1314, and the plug 1306 is embedded in the pilot hole via the second barrier metal 1311.

One candidate material that can be used to fabricate the ion conductive layer 1304 is chalcogenide GeSbTe, which is used as a phase change layer material in phase change elements. As a means for forming the ion conductive layer 1304 made of GeSbTe, there is a method of performing sputtering film formation using a GeSbTe sintered target. Specifically, using a Ge ₂ Sb ₂ Te ₅ target, a film is formed of a film made of Ge ₂ Sb ₂ Te _5.

Another material candidate that can be used for manufacturing the ion conductive layer 1304 is a SIOCH-based material containing silicon, oxygen, carbon, and hydrogen, which is formed by a plasma CVD method. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material (cyclic organosiloxane) vapor is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is supplied directly to the reaction chamber through another line.

The barrier insulating film 1314 is an insulating film having a function of preventing diffusion of metal ions contained in the ion conductive layer 1304 into the interlayer insulating film 1315 without damaging the three-terminal switch 1318. In addition, the ion conductive layer 1304 has a function of suppressing desorption of oxygen in the SIOCH material. As the barrier insulating film 1314, for example, a SiN film, a SiCN film, or the like can be used. The barrier insulating film 1314 is preferably made of the same material as the barrier insulating film 1305. A pilot hole for embedding the plug 1306 is formed in the barrier insulating film 1314, and the plug 1306 is embedded in the pilot hole via the second barrier metal 1311.

The interlayer insulating film 1315 is an insulating film formed on the barrier insulating film 1314. As the interlayer insulating film 1315, for example, a SiO ₂ or SiOC film can be used. The interlayer insulating film 1315 may be a stack of a plurality of insulating films. The interlayer insulating film 1315 may be formed of the same material as the interlayer insulating film 1313 and the interlayer insulating film 1316. A pilot hole for embedding the plug 1306 is formed in the interlayer insulating film 1315, and the plug 1306 is embedded in the pilot hole via the second barrier metal 1311.

The interlayer insulating film 1316 is an insulating film formed on the interlayer insulating film 1315. As the interlayer insulating film 1316, for example, a SiO ₂ , a SiOC film, a low dielectric constant film (for example, a SiOCH film) having a relative dielectric constant lower than that of SiO ₂ can be used. The interlayer insulating film 1316 may be a stack of a plurality of insulating films. The interlayer insulating film 1316 may be made of the same material as the interlayer insulating film 1315 and the interlayer insulating film 1313. Alternatively, the interlayer insulating film 1316 and the interlayer insulating film 1315 can be formed using different insulating materials, and a significant difference can be provided in the etching characteristics. In the interlayer insulating film 1316, a wiring groove for embedding the second wiring 1312 is formed, and the second wiring 1312 is embedded in the wiring groove via the second barrier metal 1311.

The second wiring 1312 is a wiring embedded in a wiring groove formed in the interlayer insulating film 1316 via the second barrier metal 1311. The second wiring 1312 is integrated with the plug 1306. The plug 1306 is embedded in a prepared hole formed in the interlayer insulating film 1315 and the barrier insulating film 1314 via the second barrier metal 1311.

The first electrode 1301 is a side surface of the plug 1306 and is composed of the second barrier metal 1311. The first electrode 1301 is an electrode that transmits a signal in the three-terminal switch 1318, and is in direct contact with the ion conductive layer 1304. For the first wiring 1312 and the plug 1306, for example, Cu can be used.

The second barrier metal 1311 includes the second wiring 1312 and the plug in order to prevent the metal constituting the second wiring 1312 (including the plug 1306) from diffusing into the interlayer insulating film 1316, the interlayer insulating film 1315, or the lower layer. 1306 is a conductive film having a barrier property that covers the side and bottom surfaces of 1306. For example, when the second wiring 1312 and the plug 1306 are made of a metal element whose main component is Cu, the second barrier metal 1012 includes a refractory metal such as Ta, TaN, TiN, and WCN, a nitride thereof, and the like. Alternatively, or a stacked film thereof can be used.

The barrier insulating film 1317 is formed on the surface of the second wiring 1312 and the interlayer insulating film 1316, and prevents the oxidation of the metal (for example, Cu) constituting the second wiring 1317, or configures the second wiring 1312 to the upper layer. It is an insulating film having a role of preventing diffusion of metal (Cu). As the barrier insulating film 1317, for example, a SiC film, a SiCN film, a SiN film, a stacked structure thereof, or the like can be used.

(Switching operation)
A driving method during the switching operation of the three-terminal switch of the first embodiment shown in FIG. 13 will be described.

(A) ON operation (transition process from OFF state to ON state)
First, the first wiring A 1307 that also serves as the second electrode 1302, the plug 1306 that also serves as the first electrode 1301, and the second wiring 1312 are grounded. Further, a positive voltage (+ V _ON > 0 V) is applied to the first wiring B 1303 that also serves as the third electrode. Metal ions (Cu ions) diffuse into the ion conductive layer 1304 from the first wiring B 1303 that also serves as the third electrode, and migrate to the first electrode 1301 and the second electrode 1302 side. The migrated metal ions receive electrons from the first electrode 1301 and the second electrode 1302, and are deposited as metal. The first electrode 1301 and the second electrode 1302 are connected by a metal bridge 1309 made of deposited metal. By the formation of the metal bridge 1309, the resistance value between the first electrode 1301 and the second electrode 1302 becomes low resistance, and is turned on.

In the above transition to the ON state, the first wiring B 1303 that also serves as the third electrode may be grounded, and a negative voltage (−V _ON <0 V) may be applied to the first electrode 1301 and the second electrode 1302.

(B) OFF operation (transition process from ON state to OFF state)
On the other hand, the first wiring A1307 also serving as the second electrode 1302, the plug 1306 also serving as the first electrode 1301, and the second wiring 1312 are grounded, and a negative voltage (− V _OFF <0V) is applied. The dissolution reaction of the metal constituting the metal bridge 1309 connecting the second electrode 1302 and the first electrode 1301 proceeds. The metal is ionized by the electric field generated at the interface between the ion conductive layer 1304 and the metal bridge 1309, and the generated metal ions (Cu ions) are dispersed toward the first wiring B 1303 by the electric field present in the ion conductive layer 1304. . As a result of the dissolution of the metal bridge 1309, the conduction path between the second electrode 1302 and the first electrode 1301 is cut off, so that the resistance value between the first electrode 1301 and the second electrode 1302 becomes high resistance, and the OFF state is established. Transition.

In the transition to the above-described OFF state, the first wiring B 1303 that also serves as the third electrode may be grounded, and a positive voltage (+ V _OFF > 0 V) may be applied to the first electrode 1301 and the second electrode 1302.

Since the side surface of the plug 1306 that also serves as the first electrode 1301 has a curvature, an electric field concentrates on the curvature portion during the switching operation between the ON state and the OFF state, and a switching operation that is stable and has little variation can be obtained.

(Manufacturing process)
In a semiconductor device comprising a variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate, the three-terminal switching element of the first embodiment shown in FIG. A manufacturing process for manufacturing a nonvolatile switching element will be described. FIG. 14 is a cross-sectional view schematically showing an example of a manufacturing process of the three-terminal switching element according to the first embodiment. FIG. 14 is a diagram showing steps 1 to 6 in the manufacturing process.

(Process 1)
An interlayer insulating film 1413 (eg, 300 nm thick SiO ₂ , 150 nm thick SiOCH, 100 nm thick SiO ₂ ) is deposited on a semiconductor substrate 1419 (eg, a substrate on which a semiconductor element is formed), and then lithography is performed. A wiring trench is formed in the interlayer insulating film 1413 using a method (including photoresist formation, dry etching, and photoresist removal), and then a first barrier metal A 1410 and a first barrier metal B 1408 (for example, The first wiring A1407 and the first wiring B1403 (for example, Cu) are embedded via TaN / Ta and a film thickness of 5 nm / 5 nm. The interlayer insulating film 1413 can be formed by a plasma CVD method. For example, the first wiring A1407 and the first wiring B1403 are formed by forming a first barrier metal A1410 and a first barrier metal B1408 (for example, a TaN / Ta laminated film) by a PVD method, and after forming a Cu seed by a PVD method, It can be formed by embedding Cu in the wiring trench by an electrolytic plating method, after heat treatment at a temperature of 200 ° C. or higher, and then removing excess copper other than in the wiring trench by a CMP method. As a method for forming such a series of copper wirings, a general method in this technical field can be used. Here, the CMP (Chemical Mechanical Polishing) method is to planarize the unevenness of the wafer surface that occurs during the multilayer wiring formation process by bringing the polishing liquid into contact with a rotating polishing pad while flowing the polishing liquid over the wafer surface and polishing it. Is the method. By polishing excess copper embedded in the wiring trench, a buried wiring (damascene wiring) is formed, or by planarizing the interlayer insulating film 1413 by polishing.

(Process 2)
A barrier insulating film 1405 (eg, SiN, film thickness of 30 nm) is formed over the surface of the first wiring A 1407 and the first wiring B 1403 and the interlayer insulating film 1413. Here, the barrier insulating film 1405 can be formed by a plasma CVD method. The thickness of the barrier insulating film 1405 is preferably about 10 nm to 50 nm.

(Process 3)
Next, a hard mask 1420 (eg, SiO ₂ film, 50 nm) is deposited so as to be in contact with the barrier insulating film 1405. In step 3, the hard mask 1420 can be formed by a plasma CVD method. Further, a photoresist (not shown) for patterning the hard mask 1420 is formed, and then the hard mask 1420 is dry-etched using the photoresist as an etching mask, and then oxygen plasma ashing and organic peeling are used. , Remove the photoresist.

(Process 4)
Using the hard mask 1420 as a mask, the barrier insulating film 1405 exposed from the opening of the hard mask 1420 is etched back (dry etching), whereby an opening is formed in the barrier insulating film 1405 and the opening of the barrier insulating film 1405 is formed. Then, the first wiring A1407 and the first wiring B1403 are exposed, and thereafter, an organic stripping process is performed with an amine-based stripping solution or the like, so that the copper oxide formed on the exposed surfaces of the first wiring A1407 and the first wiring B1403 is removed. In addition to the removal, the etching by-product generated during the etch back is removed. In the etch back of the barrier insulating film 1405, the wall surface of the opening of the barrier insulating film 1405 can be tapered by using reactive dry etching. In reactive dry etching, a gas containing fluorocarbon can be used as an etching gas. The hard mask 1420 is preferably completely removed during the etch back, but may remain in place when it is an insulating material. The shape of the opening of the barrier insulating film 1405 has a curvature, and the maximum length of the opening in the planar direction is 30 nm to 500 nm. Further, oxides on the surfaces of the first wiring A 1407 and the first wiring B 1403 are removed by RF (Radio Frequency) using a non-reactive gas. As the non-reactive gas, helium or argon can be used. The exposed upper surface of the first wiring A 1407 becomes the second electrode 1402.

(Process 5)
Next, an SIOCH ion conductive material containing silicon, oxygen, carbon, and hydrogen is used as an ion conductive layer 1404 so as to be in contact with the barrier insulating film 1405, the first wiring A 1407, and the first wiring B 1403 by a CVD method with a thickness of about 20 nm to 80 nm. Form. Using the carrier gas helium, the raw material mixed gas containing vaporized cyclic organosiloxane vapor and helium flow into the reaction chamber, the supply of both is stabilized, and when the pressure in the reaction chamber becomes constant, the RF power Start application. The supply amount of the raw material is 10 to 200 sccm, the supply of helium is 500 sccm via the raw material vaporizer, and 500 sccm is directly supplied to the reaction chamber by another line. The temperature is preferably about 250 ° C to 350 ° C. Next, SiN or SiCN is formed to a thickness of 30 nm as the barrier insulating film 1414 over the ion conductive layer 1404. In step 7, the barrier insulating film 1414 can be formed by a plasma CVD method. For example, it is preferable to use a SiN film formed by high-density plasma of a mixed gas of SiH ₄ / N ₂ . Although the ion conductive layer 1404 remains in a region other than the three-terminal switch element 1418, it functions as an insulating film and thus does not affect the operation of the three-terminal switch and the multilayer wiring. In step 5, 300 nm of SiO ₂ is formed as an interlayer insulating film 1415 on the barrier insulating film 1414. Further, in order to eliminate the level difference caused by the three-terminal switch 1418, the interlayer insulating film 1415 is flattened by polishing about 170 nm by a CMP method. The interlayer insulating film 1415 is desirably formed of SiO ₂ using high-density plasma in order to reliably fill the steps of the three-terminal switch element 1418.

(Step 6)
Next, an interlayer insulating film 1416 (for example, a laminate of SiOC and SiO ₂ having a low relative dielectric constant) is deposited on the interlayer insulating film 1415, and then a pilot hole for the plug 1406 and a wiring groove for the second wiring 1412 are deposited. Is formed by dry etching, and a second wiring 1412 (for example, Cu) and a plug are inserted into the wiring groove and the prepared hole through a second barrier metal 1411 (for example, TaN / Ta) using a copper dual damascene wiring process. 1106 (for example, Cu) is formed at the same time, and then a barrier insulating film 1417 (for example, a SiCN film) is deposited on the interlayer insulating film 1416 including the second wiring 1412. In step 6, the second wiring 1412 and the plug 1406 are formed by, for example, forming a second barrier metal 1411 (for example, a TaN / Ta laminated film) by the PVD method, forming a Cu seed by the PVD method, and then performing electrolytic plating. It can be formed by embedding copper in the wiring groove by the method, after heat treatment at a temperature of 200 ° C. or higher, and then removing excess copper other than in the wiring groove by the CMP method. As a method for forming such a series of copper wirings, a general method in this technical field can be used. In step 6, the side surface in contact with the second barrier metal 1411 and the ion conductive layer 1404 is the first electrode 1401. In Step 6, the interlayer insulating film 1416 and the barrier insulating film 1417 can be formed by a plasma CVD method. In step 6, the barrier insulating film 1405 is reached when the prepared hole of the plug 1406 is formed. Fluorocarbon-based gas is used for dry etching of the prepared hole for the plug 1406 and the wiring groove for the second wiring 1412.

While the present invention has been described with reference to the embodiments (and examples), the present invention is not limited to the above embodiments (and examples). Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

This application claims priority based on Japanese Patent Application No. 2012-217319 filed on September 28, 2012, the entire disclosure of which is incorporated herein.

The switching element according to the present invention can be used as a nonvolatile switching element provided in a multilayer wiring layer of a semiconductor device.

Some or all of the above embodiments may be described as in the following supplementary notes, but are not limited to the following.

(Appendix 1)
A first electrode which is a side wall portion of a metal film electrically connected to a Cu plug or Cu wiring constituting a multilayer wiring;
A second electrode which is a side wall portion of a metal film electrically connected to a Cu wiring different from the first electrode;
An insulating film sandwiched between the first electrode and the second electrode;
A switching element, wherein an ion conductive layer capable of moving a metal ionized by an electric field is in contact with side surfaces of the first electrode and the second electrode.

(Appendix 2)
The at least one third electrode that is in contact with the ion conductive layer and supplies metal ions to the ion conductive layer, and the third electrode is constituted by a Cu wiring that forms a multilayer wiring. 2. The switching element according to 1.

(Appendix 3)
A first electrode which is a side wall portion of a metal film electrically connected to a Cu plug or Cu wiring constituting a multilayer wiring;
A second electrode that is a Cu wiring different from the first electrode;
Comprising an insulating film sandwiched between the first electrode and the second electrode;
An ion conductive layer capable of moving a metal ionized by an electric field is in contact with the side surface of the first electrode and the upper surface and side surface of the second electrode;
Switching comprising: having at least one third electrode in contact with the ion conductive layer and supplying metal ions to the ion conductive layer, the third electrode being constituted by a Cu wiring forming a multilayer wiring. element.

(Appendix 4)
4. The switching element according to any one of appendix 1 to appendix 3, wherein at least one of the first electrode and the second electrode has a convex curvature.

(Appendix 5)
The switching element according to any one of appendix 1 to appendix 4, wherein an upper surface of the ion conductive layer is covered with an ion barrier layer that blocks the metal ions.

(Appendix 6)
A semiconductor device having a switching element inside a multilayer wiring layer on a semiconductor substrate,
The multilayer wiring includes at least a Cu wiring and a Cu plug,
A barrier insulating film is provided on the Cu wiring,
The barrier insulating film is provided with one opening each reaching the two Cu wirings,
A second electrode of the switching element is electrically connected to one of the Cu wirings;
A first electrode is provided on the second electrode with an insulating film interposed therebetween,
The first electrode is electrically connected to the Cu plug;
An ion conductive layer capable of moving metal ions by an electric field is in contact with side surfaces of the first electrode and the second electrode and another Cu wiring,
The Cu wiring of the multilayer wiring that is in contact with the ion conductive layer and insulated by the second electrode and the barrier insulating film also serves as the third electrode,
A semiconductor device, wherein a barrier insulating film is provided on an upper surface of the ion conductive layer.

(Appendix 7)
A semiconductor device having a switching element inside a multilayer wiring layer on a semiconductor substrate,
The multilayer wiring includes at least a Cu wiring and a Cu plug,
A barrier insulating film is provided on the Cu wiring,
The barrier insulating film is provided with one opening that reaches the two Cu wirings,
One of the Cu wirings also serves as the second electrode,
A first electrode is provided on the second electrode with a barrier insulating film interposed therebetween,
The first electrode is electrically connected to the Cu plug;
An ion conductive layer capable of moving metal ions by an electric field is in contact with the side surfaces of the first electrode and the second electrode and another Cu wiring,
The Cu wiring of the multilayer wiring in contact with the ion conductive layer also serves as the third electrode,
A semiconductor device, wherein a barrier insulating film is provided on an upper surface of the ion conductive layer.

(Appendix 8)
A semiconductor device having a switching element inside a multilayer wiring layer on a semiconductor substrate,
The multilayer wiring includes at least a Cu wiring and a Cu plug,
A barrier insulating film is provided on the Cu wiring,
The barrier insulating film is provided with one opening that reaches the two Cu wirings,
One of the Cu wirings also serves as the second electrode,
One of the Cu plugs also serves as the first electrode,
An ion conductive layer capable of moving metal ions by an electric field is in contact with the side surfaces of the first electrode and the second electrode and another Cu wiring,
The Cu wiring of the multilayer wiring in contact with the ion conductive layer also serves as the third electrode,
A semiconductor device, wherein a barrier insulating film is provided on an upper surface of the ion conductive layer.

(Appendix 9)
A method of manufacturing a semiconductor device having a switching element inside a multilayer wiring layer on a semiconductor substrate,
The multilayer wiring includes at least a Cu wiring and a Cu plug,
A barrier insulating film is provided on the Cu wiring,
The barrier insulating film is provided with one opening each reaching the two Cu wirings,
A second electrode of the switching element is electrically connected to one of the Cu wirings;
A first electrode is provided on the second electrode with an insulating film interposed therebetween,
The first electrode is electrically connected to the Cu plug;
An ion conductive layer capable of moving metal ions by an electric field is in contact with side surfaces of the first electrode and the second electrode and another Cu wiring,
The Cu wiring of the multilayer wiring in contact with the ion conductive layer also serves as the third electrode,
A barrier insulating film is provided on the upper surface of the ion conductive layer,
When opening the opening of the barrier insulating film in contact with the third electrode,
A method of manufacturing a semiconductor device, wherein a laminated film composed of the second electrode, the insulating film, and the first electrode is used as a part of a mask.

Claims

A variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a first metal film electrically connected to a first Cu plug and a first Cu wiring constituting the multilayer wiring layer;
The second electrode is a side wall portion of a second metal film electrically connected to a second Cu wiring constituting the multilayer wiring layer;
The metal bridge type switching element includes an insulating film sandwiched between the first metal film and the second metal film,
The first electrode composed of the side wall portion of the first metal film, the side wall portion of the insulating film, and the second electrode composed of the side wall portion of the second metal film form a laminated structure, and are formed on side surfaces of the laminated structure. The switching element, wherein the ion conductive layer is in contact.
The metal bridge type switching element is
A third electrode in contact with the ion conductive layer and supplying metal ions into the ion conductive layer;
The third electrode is composed of a third Cu wiring constituting the multilayer wiring layer,
The portion where the ion conductive layer is in contact with the third Cu wiring and the supply of metal ions is selected on the upper surface of the third Cu wiring,
In the metal bridge type switching element, the switching operation between the ON state and the OFF state is performed by biasing the first electrode to the potential V 1 , the second electrode to the potential V 2 , and the third electrode to the potential V 3. The bias difference | V 2 −V 1 | between the second electrode and the first electrode is different from the bias difference | V 3 −V 1 | between the third electrode and the first electrode, The bias difference | V 3 −V 2 | between the third electrode and the second electrode is changed to | V 3 −V 2 |> | V 2 −V 1 |, | V 3 −V 1 |> | V 2 −. The switching element according to claim 1, wherein the switching element is implemented by applying a switching voltage between the first electrode, the second electrode, and the third electrode by setting V 1 |. .
A variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a first metal film electrically connected to a first Cu plug and a first Cu wiring constituting the multilayer wiring layer;
The second electrode is a second Cu wiring constituting the multilayer wiring layer,
The metal bridge type switching element is
Comprising an insulating film sandwiched between the first metal film and the second Cu wiring;
The first electrode composed of the side wall portion of the first metal film, the side wall portion of the insulating film, and the second Cu wiring form a laminated structure, and the ion conductive layer is in contact with the side surface of the laminated structure. There;
The metal bridge type switching element is
A third electrode in contact with the ion conductive layer and supplying metal ions into the ion conductive layer;
The third electrode is composed of a third Cu wiring constituting the multilayer wiring layer,
The portion where the ion conductive layer is in contact with the third Cu wiring and the supply of metal ions is selected on the upper surface of the third Cu wiring,
In the metal bridge type switching element, the switching operation between the ON state and the OFF state is performed by biasing the first electrode to the potential V 1 , the second electrode to the potential V 2 , and the third electrode to the potential V 3 , respectively. The bias difference | V 2 −V 1 | between the second electrode and the first electrode is different from the bias difference | V 3 −V 1 | between the third electrode and the first electrode, The bias difference | V 3 −V 2 | between the third electrode and the second electrode is changed to | V 3 −V 2 |> | V 2 −V 1 |, | V 3 −V 1 |> | V 2 −. A switching element, which is implemented by applying a switching voltage between the first electrode, the second electrode, and the third electrode by setting V 1 |.
The switching according to any one of claims 1 to 3, wherein at least a side wall portion of the first metal film that is in contact with the ion conductive layer has a convex curvature. element.
A variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a barrier metal that covers a bottom portion and a side wall surface of a first Cu plug electrically connected to a first Cu wiring constituting the multilayer wiring layer,
The second electrode is a second Cu wiring constituting the multilayer wiring layer,
The metal bridge type switching element is
An insulating film sandwiched between a bottom surface of a barrier metal covering the bottom and side wall surfaces of the first Cu plug and a second Cu wiring;
The first electrode composed of a barrier metal sidewall covering the bottom and sidewall surfaces of the first Cu plug, the sidewall of the insulating film, and the second Cu wiring form a stacked structure, and the stacked structure The ion conductive layer is in contact with a side surface;
The metal bridge type switching element is
A third electrode in contact with the ion conductive layer and supplying metal ions into the ion conductive layer;
The third electrode is composed of a third Cu wiring constituting the multilayer wiring layer,
The portion where the ion conductive layer is in contact with the third Cu wiring and the supply of metal ions is selected on the upper surface of the third Cu wiring,
In the metal bridge type switching element, the switching operation between the ON state and the OFF state is performed by biasing the first electrode to the potential V 1 , the second electrode to the potential V 2 , and the third electrode to the potential V 3. The bias difference | V 2 −V 1 | between the second electrode and the first electrode is different from the bias difference | V 3 −V 1 | between the third electrode and the first electrode, The bias difference | V 3 −V 2 | between the third electrode and the second electrode is changed to | V 3 −V 2 |> | V 2 −V 1 |, | V 3 −V 1 |> | V 2 −. A switching element, which is implemented by applying a switching voltage between the first electrode, the second electrode, and the third electrode by setting V 1 |.
The switching element according to any one of claims 1 to 5, wherein an upper surface of the ion conductive layer is covered with an ion barrier layer that blocks the metal ions.
A semiconductor device comprising a variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a first metal film electrically connected to a first Cu plug and a first Cu wiring constituting the multilayer wiring layer;
The second electrode is a side wall portion of a second metal film electrically connected to a second Cu wiring constituting the multilayer wiring layer;
The metal bridge type switching element includes an insulating film sandwiched between the first metal film and the second metal film,
The first electrode composed of the side wall portion of the first metal film, the side wall portion of the insulating film, and the second electrode composed of the side wall portion of the second metal film form a stacked structure, and are formed on the side surfaces of the stacked structure. , The ion conductive layer is in contact,
The semiconductor device according to claim 1, wherein an upper surface of the ion conductive layer is covered with an ion barrier layer that blocks the metal ions.
The metal bridge type switching element is
A third electrode in contact with the ion conductive layer and supplying metal ions into the ion conductive layer;
The third electrode is composed of a third Cu wiring constituting the multilayer wiring layer,
The portion where the ion conductive layer is in contact with the third Cu wiring and the supply of metal ions is selected on the upper surface of the third Cu wiring,
In the metal bridge type switching element, the switching operation between the ON state and the OFF state is performed by biasing the first electrode to the potential V 1 , the second electrode to the potential V 2 , and the third electrode to the potential V 3. The bias difference | V 2 −V 1 | between the second electrode and the first electrode is different from the bias difference | V 3 −V 1 | between the third electrode and the first electrode, The bias difference | V 3 −V 2 | between the third electrode and the second electrode is changed to | V 3 −V 2 |> | V 2 −V 1 |, | V 3 −V 1 |> | V 2 −. The semiconductor device according to claim 7, wherein the semiconductor device is implemented by applying a switching voltage between the first electrode, the second electrode, and the third electrode by setting V 1 |. .
A semiconductor device comprising a variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a first metal film that is electrically connected to a first Cu plug or Cu wiring constituting the multilayer wiring layer,
The second electrode is a second Cu wiring constituting the multilayer wiring layer,
The metal bridge type switching element is
Comprising an insulating film sandwiched between the first metal film and the second Cu wiring;
The first electrode composed of the side wall portion of the first metal film, the side wall portion of the insulating film, and the second Cu wiring form a laminated structure, and the ion conductive layer is in contact with the side surface of the laminated structure. There;
The metal bridge type switching element is
A third electrode in contact with the ion conductive layer and supplying metal ions into the ion conductive layer;
The third electrode is composed of a third Cu wiring constituting the multilayer wiring layer,
The portion where the ion conductive layer is in contact with the third Cu wiring and the supply of metal ions is selected on the upper surface of the third Cu wiring,
An upper surface of the ion conductive layer is covered with an ion barrier layer that blocks the metal ions;
In the metal bridge type switching element, the switching operation between the ON state and the OFF state is performed by biasing the first electrode to the potential V 1 , the second electrode to the potential V 2 , and the third electrode to the potential V 3 , respectively. The bias difference | V 2 −V 1 | between the second electrode and the first electrode is different from the bias difference | V 3 −V 1 | between the third electrode and the first electrode, The bias difference | V 3 −V 2 | between the third electrode and the second electrode is changed to | V 3 −V 2 |> | V 2 −V 1 |, | V 3 −V 1 |> | V 2 −. The semiconductor device is implemented by applying a switching voltage between the first electrode, the second electrode, and the third electrode by setting V 1 |.
A semiconductor device comprising a variable resistance nonvolatile switching element provided in a multilayer wiring layer formed on a semiconductor substrate,
The variable resistance nonvolatile switching element includes at least a first electrode, a second electrode, and an ion conductive layer capable of moving metal ions by an electric field,
The ion conductive layer is in contact with the first electrode and the second electrode,
In the ion conductive layer that is in contact with the first electrode and the second electrode, a metal bridge is formed between the first electrode and the second electrode to form a signal transmission path, whereby the switching element is formed. Is turned on,
In the ion conductive layer in contact with the first electrode and the second electrode, the metal bridge is dissolved, and a signal transmission path is cut between the first electrode and the second electrode. The switching element constitutes a metal bridge type switching element that is in an OFF state;
The first electrode is a side wall portion of a barrier metal that covers a bottom portion and a side wall surface of a first Cu plug electrically connected to a first Cu wiring constituting the multilayer wiring layer,
The second electrode is a second Cu wiring constituting the multilayer wiring layer,
The metal bridge type switching element is
An insulating film sandwiched between a bottom surface of a barrier metal covering the bottom and side wall surfaces of the first Cu plug and a second Cu wiring;
The first electrode composed of a barrier metal sidewall covering the bottom and sidewall surfaces of the first Cu plug, the sidewall of the insulating film, and the second Cu wiring form a stacked structure, and the stacked structure The ion conductive layer is in contact with a side surface;
The metal bridge type switching element is
A third electrode in contact with the ion conductive layer and supplying metal ions into the ion conductive layer;
The third electrode is composed of a third Cu wiring constituting the multilayer wiring layer,
The portion where the ion conductive layer is in contact with the third Cu wiring and the supply of metal ions is selected on the upper surface of the third Cu wiring,
In the metal bridge type switching element, the switching operation between the ON state and the OFF state is performed by biasing the first electrode to the potential V 1 , the second electrode to the potential V 2 , and the third electrode to the potential V 3 , respectively. The bias difference | V 2 −V 1 | between the second electrode and the first electrode is different from the bias difference | V 3 −V 1 | between the third electrode and the first electrode, The bias difference | V 3 −V 2 | between the third electrode and the second electrode is changed to | V 3 −V 2 |> | V 2 −V 1 |, | V 3 −V 1 |> | V 2 −. The semiconductor device is implemented by applying a switching voltage between the first electrode, the second electrode, and the third electrode by setting V 1 |.