JP2003051583A - Semiconductor storage device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely improve the barrier property of an iridium oxide film contained in the lower electrode of a capacitance element as an oxygen barrier film. SOLUTION: An interlayer insulating film 14 is formed on a semiconductor substrate 10 to cover a field-effect transistor, and a contact plug 15 is formed in the insulating film 14 so that the plug 15 may be connected to the drain region 12. The lower electrode 16 of the capacitance element is formed on the insulating film 14 so that the electrode 16 may be connected to the plug 15 and the electrode 16 is constituted of a first-conductivity barrier film 16a, a second-conductivity iridium oxide barrier film (oxygen barrier film) 16b, and a metallic film 16c. The mean crystal grain diameter of the granular crystals constituting the barrier film 16b is adjusted to <=1/2 of the thickness of the film 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an iridium oxide film, particularly an iridium oxide film used as an electrode of a stack type ferroelectric memory cell, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, research and development of a ferroelectric film having a spontaneous polarization characteristic have been actively conducted with the aim of putting a nonvolatile RAM capable of high-speed writing and reading with a low operating voltage into practical use.

In the case of realizing a highly integrated memory of the megabit class in a semiconductor memory using these high dielectric film or ferroelectric film as a capacitance insulating film, a stack type memory is used instead of the conventional planar type memory cell. Cells are used.

The problem with this stack type memory cell is that the contact surface between the contact plug formed in the interlayer insulating film covering the field effect transistor and the lower electrode of the capacitive element formed on the interlayer insulating film is This is to prevent the situation where the insulating metal oxide forming the ferroelectric film or the high dielectric film is oxidized during high-temperature heat treatment in an oxygen atmosphere necessary for crystallization.

Therefore, an iridium oxide film which is a conductive oxide is usually provided as an oxygen barrier film between the contact plug and the lower electrode.

As a method for forming an iridium oxide film, there has been proposed a reactive sputtering method in which a metal target made of iridium is sputtered and the sputtered iridium is oxidized in the vicinity of the substrate (Japan Photographic Society (1988), Vol. .51, No.1, P.3).

[0007]

However, the above-mentioned document does not discuss specific conditions for improving the oxygen barrier property of the iridium oxide film formed by the reactive sputtering method.

Therefore, there is a problem in the related art that the oxygen barrier property of the iridium oxide film cannot be reliably improved.

In view of the above, it is an object of the present invention to surely improve the barrier property of an iridium oxide film which an electrode of a capacitive element has as an oxygen barrier film.

[0010]

In order to achieve the above-mentioned object, a first semiconductor memory device according to the present invention comprises an interlayer insulating film formed on a semiconductor substrate and a contact plug formed on the interlayer insulating film. And an electrode having an iridium oxide film as an oxygen barrier film, the capacitor being formed on the interlayer insulating film and having an electrode connected to the contact plug. The average crystal grain of the granular crystals forming the iridium oxide film. The diameter is 1/2 or less of the thickness of the iridium oxide film.

According to the first semiconductor memory device of the present invention, since the average crystal grain size of the granular crystals forming the iridium oxide film is not more than half the thickness of the iridium oxide film, Since the diffusion path of oxygen atoms is bent and oxygen atoms are difficult to diffuse in the crystal grain boundaries, the oxygen barrier property of the iridium oxide film is surely improved.

In the first semiconductor memory device, the thickness of the iridium oxide film is preferably 200 nm or less.

By doing so, it is possible to ensure that the average crystal grain size of the granular crystals forming the iridium oxide film is 1/2 or less of the thickness of the iridium oxide film.

In a second semiconductor memory device according to the present invention, an interlayer insulating film formed on a semiconductor substrate, a contact plug formed on the interlayer insulating film, and an electrode formed on the interlayer insulating film and having a contact. The capacitor includes a capacitor connected to the plug, the electrode has an iridium oxide film as an oxygen barrier film, and the iridium oxide film has a plurality of layers having different average crystal grain sizes.

According to the second semiconductor memory device of the present invention, since the iridium oxide film serving as the oxygen barrier film has a plurality of layers having different average crystal grain sizes, the oxygen atoms have the average crystal grain size. Since it is difficult to diffuse the grain boundary of the crystal forming the layer having the smaller diameter, the oxygen barrier property of the iridium oxide film is improved. On the other hand, the layer having the larger average crystal grain size improves the adhesiveness with the film in contact with the oxygen barrier film.

In the second semiconductor memory device, it is preferable that the lower layer constituting the plurality of layers has a relatively large average grain size and the upper layer constituting the plurality of layers has a relatively small average grain size. .

In this way, the upper layer prevents the diffusion of oxygen atoms approaching from above the oxygen barrier film, and the lower layer improves the adhesion to the film formed on the lower side of the oxygen barrier film. You can

In this case, the thickness of the lower layer is preferably 30 nm or less and the thickness of the upper layer is preferably 200 nm or less.

By doing so, the upper layer can surely prevent the diffusion of oxygen atoms, and the lower layer can surely improve the adhesion to the film formed below the oxygen barrier film.

A third semiconductor memory device according to the present invention includes a field effect transistor formed on a semiconductor substrate, an interlayer insulating film formed so as to cover the field effect transistor, and an interlayer insulating film. A contact plug connected to a source region or a drain region of a field effect transistor, and a capacitor element formed on an interlayer insulating film and having a lower electrode connected to the contact plug, the lower electrode serving as an oxygen barrier film. The average crystal grain size of the granular crystal that has the iridium oxide film and constitutes the iridium oxide film is not more than 1/2 of the thickness of the iridium oxide film.

According to the third semiconductor memory device of the present invention, the average crystal grain size of the granular crystals forming the iridium oxide film is not more than 1/2 of the thickness of the iridium oxide film. Since the diffusion path of oxygen atoms is bent and oxygen atoms are difficult to diffuse in the crystal grain boundaries, the oxygen barrier property of the iridium oxide film is surely improved.

In the third semiconductor memory device, the thickness of the iridium oxide film is preferably 200 nm or less.

By doing so, it is possible to ensure that the average crystal grain size of the granular crystals forming the iridium oxide film is 1/2 or less of the thickness of the iridium oxide film.

In a fourth semiconductor memory device according to the present invention, a field effect transistor formed on a semiconductor substrate, an interlayer insulating film formed so as to cover the field effect transistor, and an interlayer insulating film are formed. A contact plug connected to a source region or a drain region of a field effect transistor, and a capacitor element formed on an interlayer insulating film and having a lower electrode connected to the contact plug, the lower electrode serving as an oxygen barrier film. It has an iridium oxide film, and the iridium oxide film has a plurality of layers having different average crystal grain sizes.

According to the fourth semiconductor memory device of the present invention, the iridium oxide film serving as the oxygen barrier film has a plurality of layers having different average crystal grain sizes. Since it is difficult to diffuse the grain boundary of the crystal forming the layer having the smaller diameter, the oxygen barrier property of the iridium oxide film is improved. On the other hand, the layer having the larger average crystal grain size improves the adhesiveness with the film in contact with the oxygen barrier film.

In the fourth semiconductor memory device, it is preferable that the lower layer forming the plurality of layers has a relatively large average crystal grain size, and the upper layer forming the plurality of layers has a relatively small average grain size. .

In this way, the upper layer prevents diffusion of oxygen atoms approaching from above the oxygen barrier film, and the lower layer improves the adhesion to the film formed on the lower side of the oxygen barrier film. You can

In this case, the thickness of the lower layer is preferably 30 nm or less and the thickness of the upper layer is preferably 200 nm or less.

By doing so, the upper layer can surely prevent the diffusion of oxygen atoms, and the lower layer can surely improve the adhesion to the film formed below the oxygen barrier film.

According to a first method of manufacturing a semiconductor memory device of the present invention, an interlayer insulating film formed on a semiconductor substrate, a contact plug formed on the interlayer insulating film, and an interlayer insulating film are formed. An electrode is provided with a capacitor connected to a contact plug, and the electrode is intended for a method for manufacturing a semiconductor memory device having an iridium oxide film as an oxygen barrier film,
It is equipped with a step of forming an iridium oxide film by a reactive sputtering method performed by introducing oxygen gas and argon gas into a reaction chamber in which a target containing iridium is placed. Is defined as x and the actual partial pressure of the argon gas in the reaction chamber is defined as y, the condition of x / (x + y)> 0.5 holds.

A second method of manufacturing a semiconductor memory device according to the present invention is a field effect transistor formed on a semiconductor substrate, an interlayer insulating film formed so as to cover the field effect transistor, and an interlayer insulating film. A contact plug connected to the source region or the drain region of the field-effect transistor, and a capacitor element formed on the interlayer insulating film and having a lower electrode connected to the contact plug. The method of manufacturing a semiconductor memory device having an iridium oxide film as a barrier film is targeted. In the reactive sputtering method, the actual partial pressure of oxygen gas in the reaction chamber is x, and the actual partial pressure of argon gas in the reaction chamber is y. Is set under the condition that x / (x + y)> 0.5 holds.

According to the first or the second method for manufacturing a semiconductor memory device of the present invention, the ratio of oxygen gas to argon atoms in the gas introduced into the reaction chamber becomes large, so that sputtering is performed by colliding with the target. Since the generated atoms are changed from argon atoms to oxygen atoms, the kinetic energy of the sputtered particles becomes small, and the average crystal grain size of the particles forming the iridium oxide film becomes small accordingly.

Therefore, according to the first or second method of manufacturing a semiconductor memory device, the diffusion path of oxygen atoms in the iridium oxide film is bent, and it is difficult for oxygen atoms to diffuse in the crystal grain boundaries. The oxygen barrier property is definitely improved.

Moreover, since the iridium oxide film can be formed while the substrate is kept at room temperature or higher, the adhesion between the contact plug and the lower electrode of the capacitor is improved.

A third method for manufacturing a semiconductor device according to the present invention is an interlayer insulating film formed on a semiconductor substrate, a contact plug formed on the interlayer insulating film, and an electrode formed on the interlayer insulating film. Is provided with a capacitor connected to a contact plug, and the electrode is intended for a method for manufacturing a semiconductor memory device having an iridium oxide film composed of multiple layers having different average crystal grain sizes as an oxygen barrier film. , X is the actual partial pressure of oxygen gas in the reaction chamber, and y is the actual partial pressure of argon gas in the reaction chamber, the relationship of x / (x + y) <0.5 holds in the first stage. The second step, which is performed under the condition, is performed under the condition that the relationship of x / (x + y)> 0.5 holds.

According to a fourth method of manufacturing a semiconductor memory device of the present invention, a field effect transistor formed on a semiconductor substrate, an interlayer insulating film formed so as to cover the field effect transistor, and an interlayer insulating film. A contact plug connected to the source region or the drain region of the field-effect transistor, and a capacitor element formed on the interlayer insulating film and having a lower electrode connected to the contact plug. The method of manufacturing a semiconductor memory device having a multi-layered iridium oxide film having a different average crystal grain size as a barrier film is targeted. The reactive sputtering method uses the actual partial pressure of oxygen gas in the reaction chamber as x. The first step is carried out under the condition that the relation of x / (x + y) <0.5 is established, where y is the actual partial pressure of the argon gas. The second stage takes place in the, x /
It is performed under the condition that the relationship of (x + y)> 0.5 is established.

According to the third or fourth semiconductor memory device manufacturing method of the present invention, the first step of the reactive sputtering step is performed under the condition that x / (x + y) <0.5. , The kinetic energy of the particles to be sputtered is increased, so that the adhesion between the contact plug and the lower electrode is improved, and the relationship of x / (x + y)> 0.5 is established in the second step of the reactive sputtering process. Since it is carried out under the conditions, the kinetic energy of the particles to be sputtered becomes small, so that the average crystal grain size of the particles forming the iridium oxide film becomes small.

Therefore, according to the third or fourth semiconductor memory device manufacturing method, the adhesion between the contact plug and the electrode of the capacitor is improved, and the oxygen barrier property of the iridium oxide film is improved.

The first to fourth semiconductor memory device manufacturing methods according to the present invention further include the step of subjecting the iridium oxide film to heat treatment at a temperature of 500 ° C. to 600 ° C. in a nitrogen atmosphere. It is preferable.

In this case, since the heat treatment improves the denseness of the iridium oxide film, the oxygen barrier property of the iridium oxide film is further improved.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A semiconductor memory device and a method of manufacturing the same according to a first embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, a source region 11 and a drain region 12 are formed on the surface of the semiconductor substrate 10, and a gate electrode 13 is formed on the semiconductor substrate 10.
Are formed, and the source region 11, the drain region 12 and the gate electrode 13 form a field effect transistor.

An interlayer insulating film 14 is formed on the semiconductor substrate 10 so as to cover the field effect transistor, and the interlayer insulating film 14 is made of polysilicon so as to be connected to the drain region 12. Contact plug 15
Are formed.

A lower electrode 16 of the capacitive element is formed on the interlayer insulating film 14 so as to be connected to the contact plug 15, and the lower electrode 16 is formed from the first conductive layer in order from the bottom. The barrier film 16a, the second conductive barrier film 16b, and the metal film 16c are included.

The first conductive barrier film 16a is, for example, a titanium film having a thickness of, for example, 20 nm, a titanium aluminum nitride film having a thickness of, for example, 40 nm, and iridium having a thickness of, for example, 100 nm, which are sequentially deposited from the bottom. It is made of a film and has a function of preventing diffusion of polysilicon forming the contact plug 15.

The second conductive barrier film 16b is, for example, 1
The iridium oxide film having a thickness of 60 nm covers the side surface and the upper surface of the first conductive barrier film 16a. The second conductive barrier film 16b has a structure in which the first conductive barrier film 16a is oxidized during high-temperature heat treatment in an oxygen atmosphere for crystallizing an insulating metal oxide that forms the capacitive insulating film 17 described later. It has a function to prevent

The metal film 16c is made of a platinum film having a thickness of 50 nm, for example.

A capacitive insulating film 17 having a thickness of, for example, 160 nm is formed on the interlayer insulating film 14 so as to cover the lower electrode 16, and the capacitive insulating film 17 has, for example, SrBi 2 having a bismuth layered perovskite structure. (Ta1
-xNbx) O9 (where 0≤x≤1).

On the capacitance insulating film 17, for example, 100 n
Upper electrode 1 of a capacitive element made of a platinum film having a thickness of m
8 is formed.

As a feature of this embodiment, the structure of the second conductive barrier film 16b as the oxygen barrier film will be described below.

By the way, since oxygen diffuses through the grain boundaries of the crystals forming the oxygen barrier film, in order to improve the barrier property of the oxygen barrier film, (1) the oxygen barrier film is formed by a large columnar crystal having a strong orientation. And a method for improving the density of the crystal grain boundary that becomes a diffusion path of oxygen atoms, and (2)
It is considered that the grain size of the crystal forming the oxygen barrier film is reduced to bend the diffusion path of oxygen atoms.

However, when the iridium oxide film is deposited by the sputtering method, only a film having a poor orientation can be obtained. Therefore, the method (1) is not suitable for improving the oxygen barrier property of iridium oxide. Method (2) is suitable.

When the method (2) is adopted, the average crystal grain size needs to be 1/2 or less of the film thickness in order to bend the diffusion path of oxygen atoms.

FIG. 2A shows the cross-sectional structure of the second conductive barrier film 16b according to this embodiment, and FIG.
The cross-sectional structure of a conventional oxygen barrier film (corresponding to the second conductive barrier film 16b according to this embodiment) is shown.
The film thickness of the second conductive barrier film 16b and the film thickness of the conventional oxygen barrier film are both 200 nm or less.

In the conventional oxygen barrier film shown in FIG. 2B, since the average crystal grain size is equal to the film thickness of the oxygen barrier film, the diffusion path of oxygen atoms is linear. On the other hand, in the second conductive barrier film 16b according to the present embodiment, the average crystal grain size is 1/2 of the film thickness of the oxygen barrier film, so the diffusion path of oxygen atoms is bent. . For this reason, oxygen atoms are difficult to diffuse in the crystal grain boundaries, so that the oxygen barrier property of the second conductive barrier film 16b is improved.

FIG. 3 shows the relationship between (average crystal grain size / film thickness) in the second conductive barrier film 16b and contact resistance. The contact resistance was measured by using a plurality of semiconductor memory devices shown in FIG. 1 to form a contact chain with the drain region 12, the contact plug 15 and the lower electrode 16, and evaluating the contact resistance in this contact chain. . Incidentally, FIG.
The vertical axis of indicates the value of one contact resistance in the contact chain.

As can be seen from FIG. 3, (average grain size /
When the film thickness) is 50% or less, the contact resistance becomes 2 kΩ or less, which is not a problem in the operation of the device, and the variation is small. On the other hand, when the (average crystal grain size / film thickness) exceeds 50%, the variation in contact resistance increases, and when the (average crystal grain size / film thickness) exceeds 60%, the variation in contact resistance varies. It becomes extremely large.

A method of manufacturing the second conductive barrier film (iridium oxide film) 16b in the semiconductor memory device according to the first embodiment of the present invention will be described below.

(First Manufacturing Method of Semiconductor Memory Device According to First Embodiment) The first manufacturing method is a method of forming an iridium oxide film by reactive sputtering using a parallel plate type DC magnetron sputtering apparatus. That is, an iridium oxide film made of granular crystals and having an average crystal grain size of half or less of the film thickness is deposited on the substrate. In this case, as the gas introduced into the reaction chamber, argon gas is used as the inert gas and oxygen is used as the active gas.

In order to reduce the crystal grain size, it is preferable to reduce the kinetic energy of particles that move around on the substrate surface after reaching the substrate.

Therefore, the first manufacturing method is to lower the substrate temperature below room temperature. Specifically, when the substrate is cooled to about 10 ° C. with liquid nitrogen or the like, the kinetic energy of the particles reaching the substrate is surely reduced, so that the average crystal grain size becomes 80 nm or less. Can be reduced to 1/2 or less of the film thickness.

However, there is a problem that the iridium oxide film formed by the reactive sputtering method is easily peeled off while the substrate is kept at a temperature lower than room temperature.

(Second Manufacturing Method of Semiconductor Memory Device According to First Embodiment) The second manufacturing method is also one which is formed by reactive sputtering using a parallel plate type DC magnetron sputtering apparatus, and a substrate An iridium oxide film made of granular crystals and having an average crystal grain size of half or less of the film thickness is deposited on the upper surface. In this case, as the gas introduced into the reaction chamber, argon gas is used as the inert gas and oxygen is used as the active gas.

In the second manufacturing method, in order to reduce the kinetic energy of particles reaching the substrate, the ratio of oxygen gas to argon gas is increased and iridium atoms are sputtered from oxygen atoms having a small mass. is there. In this method, it is necessary to adjust the introduction ratio of oxygen gas to argon gas according to conditions such as the type of apparatus, the pressure in the reaction chamber, the magnitude of sputtering power, and the like. The reason is that iridium, which is being sputtered and flying, is associated with oxygen atoms (so-called getter effect).
Is due to.

In FIG. 4, the substrate temperature is set to 400 ° C.
When an iridium oxide film (film thickness = 160 nm) is formed by reactive sputtering performed by introducing O 2 gas and Ar gas into a reaction chamber in which the pressure is set to 0.67 Pa and the sputtering power is set to 1 kW. ,
O2 gas flow rate / (O2 gas flow rate + Ar gas flow rate)
The relationship between (hereinafter, simply referred to as oxygen gas ratio) and the sheet resistance of the iridium oxide film, that is, the oxygen gas ratio dependency of the sheet resistance is shown. In this case, the film thickness is 160 nm
The sheet resistance for the average crystal grain size of the granular crystals forming the iridium oxide film to be 1/2 or less of the film thickness is 9Ω
/ □ or more.

In FIG. 4, since oxygen atoms are consumed by the getter effect in the region A, the second conductive barrier film 16b is substantially an iridium film and has a low sheet resistance.

In the region B, the getter effect is saturated, and the oxygen atoms in the reaction chamber increase, so that the surface of the target is oxidized and the second conductive barrier film increases with the increase of O 2 gas. The sheet resistance of 16b rapidly increases.

In the region C, since the surface of the target is completely oxidized, the second conductive barrier film 16b is completely an iridium oxide film.
The sheet resistance of the conductive barrier film 16b is almost unchanged.

In the region D, since the ratio of O 2 atoms to Ar atoms in the reaction chamber becomes large, the atoms that collide with the target and cause sputtering are changed from Ar atoms to O atoms.
Turns into two atoms. Since the O2 atom has a smaller mass and a smaller momentum than the Ar atom, the ratio of sputtered particles is low, so that the deposition rate is low. Further, since the kinetic energy of the sputtered particles is also small, the particle size of the particles forming the second conductive barrier film 16b is small and the sheet resistance is high.

In the region E, the flow rate of Ar gas is extremely low, so that no discharge occurs.

Therefore, if the sputtering is performed under the condition of the region D, an iridium oxide film made of granular crystals having a small grain size can be surely obtained.

By the way, when the sputtering power, which is one of the sputtering conditions, is increased, the current density of the sputtering is increased, so that the getter effect remarkably appears.

FIG. 5 shows the sputtering power and oxygen gas ratio when an iridium oxide film was formed by reactive sputtering performed by introducing O 2 gas and Ar gas into a reaction chamber whose pressure was set to 0.67 Pa. connection of,
That is, it shows the power dependence of the oxygen gas ratio.

As can be seen from FIG. 5, as the sputtering power increases, the region A, that is, the region where oxygen atoms are consumed by the getter effect, increases, and the oxygen gas ratio changing from the region A to the region B increases. Along with this, the oxygen gas ratio changing from the region B to the region C and the oxygen gas ratio changing from the region C to the region D also increase.

FIG. 6 shows the pressure and oxygen gas ratio in the reaction chamber when an iridium oxide film is formed by reactive sputtering performed by introducing O 2 gas and Ar gas into the reaction chamber in which the sputtering power is set to 1 kW. And the pressure dependence of the oxygen gas ratio.

As can be seen from FIG. 6, when the pressure in the reaction chamber, which is one of the sputtering conditions, is increased, the effect of the getter effect is reduced, and the oxygen gas ratio changing from the region A to the region B is reduced. Along with this, the oxygen gas ratio changing from the region B to the region C and the oxygen gas ratio changing from the region C to the region D also decrease.

Here, the region D, that is, the region where an iridium oxide film made of granular crystals having a small grain size can be reliably obtained is defined.

First, the amount of oxygen gas used to form iridium oxide is a value obtained by subtracting the amount of O ₂ gas in the region A from the amount of O ₂ gas introduced into the reaction chamber.
This corresponds to x in FIG. 4, and the amount of Ar gas corresponds to y in FIG.

Therefore, the area D is x / (x + y)> 0.5.
Therefore, if reactive sputtering is performed within the range that satisfies this relational expression, an iridium oxide film composed of granular crystals having a small grain size and having a high oxygen barrier property can be reliably formed. .

Also, since the iridium oxide film can be formed while the substrate is kept at room temperature or higher, the adhesion of the iridium oxide film is also improved.

(Second Embodiment) A semiconductor memory device and a method of manufacturing the same according to a second embodiment of the present invention will be described below with reference to FIGS.

The basic structure of the semiconductor memory device according to the second embodiment is the same as that of the semiconductor memory device according to the first embodiment, and as shown in FIG. A region 11 and a drain region 12 are formed, and a gate electrode 13 is formed on the semiconductor substrate 10. The source region 11, the drain region 12 and the gate electrode 13 form a field effect transistor. There is.

An interlayer insulating film 14 is formed on the semiconductor substrate 10 so as to cover the field effect transistor, and the interlayer insulating film 14 is made of polysilicon so as to be connected to the drain region 12. Contact plug 15
Are formed.

A lower electrode 16 of the capacitive element is formed on the interlayer insulating film 14 so as to be connected to the contact plug 15, and the lower electrode 16 is formed from the first conductive layer in order from the bottom. The barrier film 16a, the second conductive barrier film 16b, and the metal film 16c are included.

FIG. 7 shows a cross-sectional structure of the second conductive barrier film 16b. The second conductive barrier film 16b is
A lower layer 16b for improving the adhesion between the upper layer 16ba functioning as an oxygen barrier layer and the first conductive barrier film 16a.
It has a laminated structure with b.

The crystal structure of the upper layer 16ba is a granular crystal. The crystal structure of the lower layer 16bb may be a granular crystal or a columnar crystal, but the average crystal grain size D ₂ of the lower layer 16bb is the upper layer 1
It has a feature that it is larger than the average crystal grain size D _{1 of} 6 ba. Since the thickness of the lower layer 16bb may be smaller than the crystal grain size as shown in FIG. 7, the average crystal grain sizes D ₁ and D ₂ referred to here are the second conductive barrier film 1
The value in the plane direction of 6b is used.

The average crystal grain size D of the upper layer 16ba
₁ is 1/2 or less of the film thickness of the upper layer 16ba.

By the way, the lower layer 16bb functions as an adhesion layer, but has a poor oxygen barrier property. Therefore, it is preferable that the film thickness of the lower layer 16bb is as small as possible within the range where the adhesiveness can be secured. The film thickness of the lower layer 16bb is specifically about 5 nm to 30 nm, preferably about 10 nm.

Since the upper layer 16ba functions as an oxygen barrier layer, it is preferable that the upper layer 16ba be as thick as possible within the range where film formation is possible. Specifically, the film thickness of the upper layer 16ba is preferably not less than twice the average crystal grain size D ₁ of the upper layer 16ba and not more than 200 nm.

(Method for Manufacturing Semiconductor Memory Device According to Second Embodiment) Hereinafter, a method for manufacturing the second conductive barrier film (iridium oxide film) 16b in the semiconductor memory device according to the second embodiment of the present invention. Will be described.

The method of manufacturing the second conductive barrier film 16b according to the second embodiment is also one in which it is formed by reactive sputtering using a parallel plate type DC magnetron sputtering apparatus, and is formed on the substrate by granular crystals. Then, an iridium oxide film having an average crystal grain size of half or less of the film thickness is deposited. In this case, as the gas introduced into the reaction chamber, argon gas is used as the inert gas and oxygen is used as the active gas.

By the way, if the kinetic energy of the particles that reach the substrate is made small, the crystal grain size can be made small. However, in this way, it becomes difficult for the sputtered particles to be implanted into the substrate, so that the iridium oxide film and the substrate are not separated. There is a problem that the adhesion layer is not formed between the two layers, which deteriorates the adhesion of the iridium oxide film.

Therefore, in the first step of the sputtering step, the adhesion layer is formed by performing the sputtering under the condition that the kinetic energy of the particles to be sputtered is increased, and in the second step of the sputtering step, the particles to be sputtered are sputtered. It is preferable to reduce the crystal grain size by performing sputtering under the condition that the kinetic energy becomes small.

Specifically, in the first stage, x / (x +
It is preferable that sputtering is performed under the condition of y) <0.5, and then, in the second step, sputtering is performed under the condition of x / (x + y)> 0.5. In this case, the first
Since the iridium oxide film formed in the stage has a poor oxygen barrier property, it is preferably as thin as possible. Specifically, the thickness of the iridium oxide film formed in the first step is
It is preferably 30 nm or less, more preferably about 20 nm.

According to the first to third manufacturing methods, it is possible to form an iridium oxide film having an average crystal grain size of half or less of the film thickness. It is preferable that the iridium oxide film be densified by performing a heat treatment at a temperature of from ℃ to 600 ℃, for example, at a temperature of 550 ℃. In this case, the reason why the temperature of 500 ° C. or higher is preferable is that the film quality is densified by sufficient baking, and the reason that the temperature of 600 ° C. or lower is preferable is that the surface morphology becomes rough due to the oxidation of unreacted iridium. This is to prevent it.

Therefore, if the iridium oxide film is subjected to a heat treatment at a temperature of 500 ° C. to 600 ° C. after sputtering, the density of the crystal grain boundaries, which become diffusion paths for oxygen atoms, is improved, so that the oxygen content of the iridium oxide film is increased. The barrier property is further improved.

[0097]

According to the first or third semiconductor memory device of the present invention, the average crystal grain size of the granular crystals forming the iridium oxide film is ½ or less of the film thickness. Because the diffusion path of oxygen atoms bends,
Since oxygen atoms are difficult to diffuse in the crystal grain boundaries, the oxygen barrier property of the iridium oxide film is surely improved.

According to the second or fourth semiconductor memory device of the present invention, since the iridium oxide film has a plurality of layers having different average crystal grain sizes, the oxygen atom of the one having a smaller average crystal grain size is used. Since it is difficult to diffuse the grain boundaries of the crystals constituting the layer, the oxygen barrier property of the iridium oxide film is improved, and the layer with the larger average crystal grain size improves the adhesiveness with the film in contact with the oxygen barrier film. .

According to the first or third method of manufacturing a semiconductor memory device of the present invention, the ratio of oxygen gas to argon atoms in the gas introduced into the reaction chamber becomes large, so that the kinetic energy of sputtered particles is increased. Becomes smaller, and accordingly, the average crystal grain size of the particles forming the iridium oxide film becomes smaller, and the iridium oxide film can be formed while the substrate is kept at room temperature or higher. Therefore, the oxygen barrier property of the iridium oxide film is surely improved and the adhesion between the contact plug and the lower electrode is also improved.

According to the second or fourth method for manufacturing a semiconductor memory device of the present invention, in the first step of the reactive sputtering step, the kinetic energy of the particles to be sputtered increases, so that the contact plug and the lower electrode. And the kinetic energy of the particles to be sputtered becomes smaller in the second step of the reactive sputtering process, so that the average crystal grain size of the particles forming the iridium oxide film becomes smaller. Therefore, the oxygen barrier property of the iridium oxide film is surely improved and the adhesion between the contact plug and the lower electrode is also improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a semiconductor memory device according to a first embodiment of the present invention.

2A is a cross-sectional view of a second conductive barrier film (oxygen barrier film) in the semiconductor memory device according to the first embodiment of the present invention, and FIG. 2B is a conventional semiconductor memory device. FIG. 3 is a cross-sectional view of an oxygen barrier film in the device.

FIG. 3 is a diagram showing a relationship between (average crystal grain size / film thickness) and a contact resistance in a second conductive barrier film (oxygen barrier film) in the semiconductor memory device according to the first embodiment of the present invention. is there.

[4] The iridium oxide film by the method of manufacturing a semiconductor memory device according to a first embodiment of the present invention definitive when deposited, O ₂ gas flow rate / (the flow rate of O ₂ gas flow rate + Ar gas), It is a figure which shows the relationship with the sheet resistance of an iridium oxide film.

FIG. 5 is a diagram showing a relationship between sputtering power and oxygen gas ratio when an iridium oxide film is formed by the method for manufacturing a semiconductor memory device according to the first embodiment of the present invention.

FIG. 6 is a diagram showing the relationship between the pressure in the reaction chamber and the oxygen gas ratio when an iridium oxide film is formed by the method for manufacturing a semiconductor memory device according to the first embodiment of the present invention.

FIG. 7 is a cross-sectional view of a second conductive barrier film (oxygen barrier film) in the semiconductor memory device according to the second embodiment of the present invention.

[Explanation of symbols]

10 semiconductor substrate 11 source region 12 drain region 13 gate electrode 14 interlayer insulating film 15 contact plug 16 lower electrode 16a first conductive barrier film 16b second conductive barrier film (oxygen barrier film) 16ba second conductive barrier Lower layer of film (adhesion layer) 16bb Upper layer of second conductive barrier film (oxygen barrier film) 16c Metal film 17 Capacitance insulating film 18 Upper electrode

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[Procedure amendment]

[Submission date] April 9, 2002 (2002.4.9)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

A second method of manufacturing a semiconductor memory device according to the present invention is a field effect transistor formed on a semiconductor substrate, an interlayer insulating film formed so as to cover the field effect transistor, and an interlayer insulating film. A contact plug connected to the source region or the drain region of the field-effect transistor, and a capacitor element formed on the interlayer insulating film and having a lower electrode connected to the contact plug. A method for manufacturing a semiconductor memory device having an iridium oxide film as a barrier film is provided.
Oxygen gas and
Reactive sputtering method performed by introducing argon gas
The reactive sputtering method has a step of forming an iridium oxide film by using x. When the actual partial pressure of oxygen gas in the reaction chamber is x and the actual partial pressure of argon gas in the reaction chamber is y, x / It is performed under the condition that the relationship of (x + y)> 0.5 is established.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction content]

A third method for manufacturing a semiconductor device according to the present invention is an interlayer insulating film formed on a semiconductor substrate, a contact plug formed on the interlayer insulating film, and an electrode formed on the interlayer insulating film. There a capacitive element connected to the contact plug, the electrode is a method of manufacturing a semiconductor memory device having iridium oxide film having an average crystal grain size is different from each other multilayer as an oxygen barrier film is intended for, including iridium
In the reaction chamber where the target is placed, oxygen gas and
Gas is introduced by the reactive sputtering method.
The reactive sputtering method is provided with a step of forming an iridium oxide film. When the actual partial pressure of oxygen gas in the reaction chamber is x and the actual partial pressure of argon gas in the reaction chamber is y, The step is performed under the condition that the relationship of x / (x + y) <0.5 is satisfied, and the second step performed thereafter is performed under the condition that the relationship of x / (x + y)> 0.5 is satisfied.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction content]

According to a fourth method of manufacturing a semiconductor memory device of the present invention, a field effect transistor formed on a semiconductor substrate, an interlayer insulating film formed so as to cover the field effect transistor, and an interlayer insulating film. A contact plug connected to the source region or the drain region of the field-effect transistor, and a capacitor element formed on the interlayer insulating film and having a lower electrode connected to the contact plug. A method of manufacturing a semiconductor memory device having a multilayered iridium oxide film having a different average crystal grain size as a barrier film is targeted .
Oxygen gas and argon gas in the reaction chamber where the get is placed
Is introduced by the reactive sputtering method.
The reactive sputtering method is provided with a step of forming a rhidium film. When the actual partial pressure of oxygen gas in the reaction chamber is x and the actual partial pressure of argon gas in the reaction chamber is y,
The first step is performed under the condition that the relationship of x / (x + y) <0.5 is established, and the second step performed thereafter is x / (x + y) <0.5.
It is performed under the condition that the relationship of (x + y)> 0.5 is established.

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Claims (15)

[Claims] 1. An inter-layer insulating film formed on a semiconductor substrate, a contact plug formed on the inter-layer insulating film, and a capacitor element formed on the inter-layer insulating film and having an electrode connected to the contact plug. The electrode has an iridium oxide film as an oxygen barrier film, and the average crystal grain size of the granular crystals forming the iridium oxide film is ½ or less of the thickness of the iridium oxide film. And semiconductor memory device. 2. The film thickness of the iridium oxide film is 200 n
The semiconductor memory device according to claim 1, wherein the semiconductor memory device has a thickness of m or less. 3. An interlayer insulating film formed on a semiconductor substrate, a contact plug formed on the interlayer insulating film, and a capacitive element formed on the interlayer insulating film and having an electrode connected to the contact plug. The semiconductor memory device according to claim 1, wherein the electrode has an iridium oxide film as an oxygen barrier film, and the iridium oxide film has a plurality of layers having different average crystal grain sizes. 4. The average crystal grain size of a lower layer forming the plurality of layers is relatively large, and the average crystal grain size of an upper layer forming the plurality of layers is relatively small. 3. The semiconductor memory device according to item 3. 5. The film thickness of the lower layer is 30 nm or less,
The semiconductor memory device according to claim 4, wherein the film thickness of the upper layer is 200 nm or less. 6. A field effect transistor formed on a semiconductor substrate, an interlayer insulating film formed to cover the field effect transistor, a source of the field effect transistor formed on the interlayer insulating film. A contact plug connected to the region or the drain region, and a capacitor element formed on the interlayer insulating film and having a lower electrode connected to the contact plug, the lower electrode including an iridium oxide film as an oxygen barrier film. The semiconductor memory device according to claim 1, wherein the average crystal grain size of the granular crystals forming the iridium oxide film is ½ or less of the thickness of the iridium oxide film. 7. The film thickness of the iridium oxide film is 200 n
7. The semiconductor memory device according to claim 6, wherein the thickness is m or less. 8. A field effect transistor formed on a semiconductor substrate, an interlayer insulating film formed so as to cover the field effect transistor, and a source of the field effect transistor formed on the interlayer insulating film. A contact plug connected to the region or the drain region, and a capacitor element formed on the interlayer insulating film and having a lower electrode connected to the contact plug, the lower electrode including an iridium oxide film as an oxygen barrier film. The semiconductor memory device according to claim 1, wherein the iridium oxide film has a plurality of layers having different average crystal grain sizes. 9. The average crystal grain size of a lower layer forming the plurality of layers is relatively large, and the average crystal grain size of an upper layer forming the plurality of layers is relatively small. 8. The semiconductor memory device according to item 8. 10. The semiconductor memory device according to claim 9, wherein the film thickness of the lower layer is 30 nm or less, and the film thickness of the upper layer is 200 nm or less. 11. An interlayer insulating film formed on a semiconductor substrate, a contact plug formed on the interlayer insulating film,
A method of manufacturing a semiconductor memory device, comprising: a capacitive element formed on the interlayer insulating film, the electrode being connected to the contact plug, the electrode having an iridium oxide film as an oxygen barrier film, the method including: iridium The method includes a step of forming the iridium oxide film by a reactive sputtering method performed by introducing oxygen gas and argon gas into a reaction chamber in which a target is placed, and the reactive sputtering method is a method of actually using oxygen gas in the reaction chamber. Where x is the partial pressure of x and y is the actual partial pressure of the argon gas in the reaction chamber, x / (x + y)> 0.5
The method for manufacturing a semiconductor memory device is performed under the condition that 12. A field effect transistor formed on a semiconductor substrate, an interlayer insulating film formed so as to cover the field effect transistor, and a source of the field effect transistor formed on the interlayer insulating film. A contact plug connected to the region or the drain region and a capacitor element formed on the interlayer insulating film and having a lower electrode connected to the contact plug, the lower electrode including an iridium oxide film as an oxygen barrier film. A method for manufacturing a semiconductor memory device having, wherein in the reactive sputtering method, an actual partial pressure of oxygen gas in the reaction chamber is x, and an actual partial pressure of argon gas in the reaction chamber is y. x / (x + y)> 0.5
The method for manufacturing a semiconductor memory device is performed under the condition that 13. An interlayer insulating film formed on a semiconductor substrate, a contact plug formed on the interlayer insulating film,
A semiconductor memory having a capacitor element formed on the interlayer insulating film, the electrode being connected to the contact plug, and the electrode having an iridium oxide film composed of multiple layers having different average crystal grain sizes as an oxygen barrier film. A method of manufacturing an apparatus, wherein in the reactive sputtering method, when an actual partial pressure of oxygen gas in the reaction chamber is x and an actual partial pressure of argon gas in the reaction chamber is y, a first The steps are x / (x
+ Y) <0.5 is satisfied, and the subsequent second step is performed under the condition that x / (x + y)> 0.5 is satisfied. Production method. 14. A field effect transistor formed on a semiconductor substrate, an interlayer insulating film formed to cover the field effect transistor, and a source of the field effect transistor formed on the interlayer insulating film. A contact plug connected to the region or the drain region, and a capacitor element formed on the interlayer insulating film and having a lower electrode connected to the contact plug, the lower electrode serving as an oxygen barrier film having an average crystal grain size. Is a method of manufacturing a semiconductor memory device having an iridium oxide film composed of different multilayers, wherein the reactive sputtering method is set such that an actual partial pressure of oxygen gas in the reaction chamber is x, When the actual partial pressure is y, the first step is x / (x
+ Y) <0.5 is satisfied, and the subsequent second step is performed under the condition that x / (x + y)> 0.5 is satisfied. Production method. 15. The method according to claim 11, further comprising the step of subjecting the iridium oxide film to a heat treatment at a temperature of 500 ° C. to 600 ° C. in a nitrogen atmosphere. A method for manufacturing a semiconductor memory device according to claim 1.