JP2002344041A - Tunnel junction element and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ferromagnetic tunnel junction element, which is much improved in quality by realizing an optimal reaction condition, when an interface layer is turned to a high-resistance layer through a reactive gas treatment. SOLUTION: By using a high-resistance film is formed by the use of radiation for heating to obtain this ferromagnetic tunnel junction element, radiation for heating is used to obtain a high-resistance film, so that the reaction of active gas on an interface layer can be activated; while being limited to the surface layer and its vicinity, the high-resistance film can be improved in the directional uniformity of film quality and chemical bonding condition, and excessive reaction and diffusion of reactive gas are restrained at the same time, so that a ferromagnetic tunnel junction element of high quality is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ferromagnetic tunnel junction device and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, attention has been focused on the potentially high MR ratio of ferromagnetic tunnel junction devices, and magnetic heads,
Application development to devices such as MRAM (Magnetic Random Access Memory) has been active. FIG. 1 is a conceptual diagram of a general ferromagnetic tunnel junction. A lower electrode and an interlayer insulating film are formed on the substrate. A contact hole is formed in the interlayer insulating film, and a ferromagnetic layer / high-resistance layer / ferromagnetic layer is buried in the contact hole. An upper electrode is formed on the upper ferromagnetic layer and the interlayer insulating film so as to cover the contact hole. If the resistivity of the ferromagnetic material is sufficiently low, it is possible to treat the upper electrode and the upper ferromagnetic material and the lower electrode and the lower ferromagnetic material as one.
In addition, in actual application of a device, a layer for controlling characteristics such as an antiferromagnetic film is inserted, and the structure is generally more complicated.

The main points of a ferromagnetic tunnel junction device are as follows.
The upper and lower ferromagnetic layers are sandwiched between the upper and lower ferromagnetic layers, and the upper and lower ferromagnetic layers are insulated except at the junction via the high resistance layer.

In order to use such a ferromagnetic tunnel junction device as a device such as a magnetic head or an MRAM, a ferromagnetic tunnel junction having a high rate of change in magnetoresistance is required.
Control the required junction resistance according to the type of device,
In addition, it is necessary to reduce the variation in characteristics between elements. Furthermore, the effective magnetoresistance change rate must be maintained at a high level with respect to heat resistance at a process temperature or higher at the time of processing into a device and operating bias voltage.

The rate of change in magnetoresistance depends on the spin polarizability of the upper and lower ferromagnetic layers near the interface with the high-resistance layer and the type and film quality of the high-resistance layer.

Materials having high polarizability include metallic magnetic alloys such as Fe ₅₀ Co ₅₀ and Ni ₆₀ Fe ₄₀ , and non-metallic magnetic alloys such as CrO ₂ and Fe ₂ O _3. Metal compounds are known.

On the other hand, the high resistance layer needs to be a uniform film having a thickness of several nm or less in order to electrically separate the upper and lower ferromagnetic layers and to allow a tunnel current to flow through the junction. In addition, due to thermal excitation or applied bias at the operating temperature, the current flows over the barrier barrier instead of the tunnel. If the leakage current component is large, the magnetoresistance change rate decreases, so the barrier height as the tunnel barrier must be high. .

As a conventional high-resistance layer, an oxide-based material such as Al ₂ O ₃ is known, and such a high-resistance layer is formed by forming a metal film on a lower ferromagnetic layer, and then forming the layer by oxygen. It is formed by oxidation treatment such as natural oxidation, oxidation by oxygen plasma, and oxidation by oxygen ion beam.

[0009]

However, when a high resistance layer is formed by oxidizing a metal film,
Since oxidation proceeds from the metal surface, it is difficult to control the oxidation state in the depth direction.

[0010] If unreacted metal remains due to insufficient oxidation, the rate of change in magnetoresistance is reduced, or the metal is diffused into the ferromagnetic layer to cause deterioration of magnetic properties. Conversely, excessive oxidation causes the underlying ferromagnetic layer to be oxidized, causing a decrease in the rate of change in magnetoresistance and deterioration in magnetic characteristics.

As one means for improving the controllability, for example, a method of forming a metal film and oxidizing it a plurality of times and stacking it in multiple stages is used. At this time, in order to make the metal layer uniform in the thickness direction, it is desirable that the one-stage metal film be thin.However, if oxygen having a high energy state such as plasma oxidation is used for the oxidation treatment method in this case, excessive oxidation is performed. It is difficult to suppress it, and even if oxygen does not directly oxidize the magnetic film below the metal film, excess oxygen is incorporated into the film, and excess oxygen is added to the ferromagnetic layer at the upper and lower interfaces by heat treatment. To oxidize and deteriorate the characteristics. On the other hand, when the natural oxidation method is used, it takes a long time for the oxidation treatment, the state of the chemical bond between the metal film and oxygen is insufficient, the height of the tunnel barrier is reduced, and the characteristic is easily deteriorated.

In view of the above-mentioned conventional problems, the present invention improves the homogeneity of a high-resistance film in the direction of film quality and the state of chemical bonding of the film while suppressing excessive oxidation and diffusion of oxygen. , And a method of manufacturing the same.

[0013]

In order to achieve this object, a ferromagnetic tunnel junction device according to the present invention comprises a conductive layer 1 including a ferromagnetic layer 1 of a metal or a compound at least within 5 nm from a junction interface; At least 5n from the joint interface
A conductive layer 2 including a ferromagnetic layer 2 which is a metal or a compound within a distance of about m is formed at the same time as the interface layer 1 is formed via the high-resistance layer 1, and the interface layer 1 is formed in a reactive gas. To form the high resistance layer 1 by heating by radiation at
Alternatively, the step of forming the interface layer 1 and heating in a reactive gas by radiation is repeated a plurality of times to form the high-resistance layer 1.

By radiant heating, it is possible to activate the reaction between the interface layer and the reactive gas in a focused manner, thereby shortening the reaction time and improving the quality of the high-resistance film, and at the same time, through the film surface. Since energy is transmitted, excess oxygen can be prevented from being taken into the film.

When the ferromagnetic layer and the junction interface are separated from each other by more than 5 nm, it is possible to control the reaction state and form a high-resistance film without oxidizing the ferromagnetic layer without necessarily using the present invention. However, in that case, the spin-polarized state of the tunnel-conducting electrons is lost, and the magnetoresistance ratio is remarkably deteriorated. In order for the spin polarization state not to be lost, the ferromagnetic layer and the junction interface need to be 5 nm, more preferably the ferromagnetic layer and the junction interface are directly adjacent to each other. However, in that case, the control of the oxidation state by the conventional method becomes difficult, and the present invention is required.

Another ferromagnetic tunnel junction device of the present invention comprises:
A conductive layer 1 including a ferromagnetic layer 1 of a metal or a compound at least within 5 nm from a junction interface and a conductive layer 2 including a ferromagnetic layer 2 of a metal or a compound at least within 5 nm from a junction interface are formed of a high-resistance layer 1b. And the high resistance layer 1b is formed while the interface layer 1b is heated by radiation in a reactive gas to form the high resistance layer 1b.

According to another ferromagnetic tunnel junction device of the present invention,
A conductive layer 1 including a ferromagnetic layer 1 made of a metal or a compound at least within 5 nm from the junction interface and a conductive layer 2 containing a ferromagnetic layer 2 made of a metal or a compound at least within 5 nm from the junction interface are formed of a high-resistance layer 1c. At the same time, the high-resistance layer 1c is formed by forming the interface layer 1c in a reactive gas and then heating by radiation to form the high-resistance layer 1c.

According to another ferromagnetic tunnel junction device of the present invention,
A conductive layer 1 including a ferromagnetic layer 1 of a metal or a compound at least within 5 nm from a junction interface and a conductive layer 2 including a ferromagnetic layer 2 of a metal or a compound at least within 5 nm from a junction interface are formed of a high resistance layer 1d At the same time, the high-resistance layer 1d is formed by forming the interface layer 1d in a reactive gas and then heating it by radiation in the reactive gas to form the high-resistance layer 1d. I do.

In these inventions, as described in detail in the first invention, when the interface layer is formed into a high-resistance layer by reaction with a reactive gas, the vicinity of the interface where the reaction occurs by using radiant heating. The reaction alone can be activated only by itself to obtain a uniform and high-resistance layer with good film quality. In order to efficiently transmit the spin-polarized state of the electrons conducting tunnel conduction, the interface between the ferromagnetic layer and the junction needs to be 5 nm or less.
More preferably, direct contact makes it possible to obtain a high magnetoresistance change rate.

Similar effects can be obtained by combining the above inventions. Specifically, a method of further radiant heating after forming the interface layer while radiant heating in a reactive gas,
After forming the interface layer while radiant heating in a reactive gas,
The same effect can be obtained even if a high resistance layer is formed by radiant heating in a reactive gas.

When the flash annealing method is used as the heating method by radiation according to the present invention, the flash annealing method in which a large amount of light is heated in a short time can activate only the vicinity of the interface where the reaction is occurring. can get.

When a laser annealing method is used as the heating method by radiation of the present invention, the vicinity of the interface where the reaction is occurring can be activated by using light having only a wavelength that provides a favorable effect, so that a good effect can be obtained.

When the pulse laser annealing method is used as the heating method by radiation according to the present invention, the vicinity of the interface where a reaction occurs with a large energy in a short time can be activated by using only light having a wavelength that can provide a favorable effect. A good effect can be obtained.

When the reflectance for the interface layer 1 is η1 and the reflectance for the high-resistance layer 1 is η2 as the wavelength used for the radiant heating of the present invention, if a wavelength of η1> η2 is used, the In addition, since the activation can be performed with emphasis on a portion where the reaction has started to occur, a good effect can be obtained.

B, C, Al, S
i, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta,
When an alloy film composed of at least one of W is used, a compound of these metals can form a potentially high tunnel barrier, and thus a good effect can be obtained.

When N, O, or a mixed gas thereof is used as the reactive gas of the present invention, a compound obtained from these reactive gases can form a potentially high tunnel barrier, and thus a good effect is obtained.

As the high resistance layer of the present invention, MaXb (M =
B, C, Al, Si, Ti, V, Cr, Zr, Nb, M
at least one element selected from o, Hf, Ta, and W; X = N, at least one element selected from O)
When using a compound represented by, and the light source used for radiant heating is mainly a light source having an absorption wavelength of MX bond, when forming a high resistance layer by reaction with a reactive gas from the interface layer, The efficiency of activating the reaction itself is improved, and a good effect is obtained.

If the required energy is applied to the annealing by radiation of the present invention in a time of one minute or less per time, the extra energy which is not used for activating the reaction but diffuses as heat into the film is adversely affected. Can be held down. More preferably, when the necessary energy is applied in a time of 1 second or less, a better effect can be obtained.

In the annealing by radiation of the present invention, at least 5 nm from the surface of the interface layer by radiation heating.
By including a thermal process in which a temperature gradient of 10 ° C./nm or more is formed in the following range, only the vicinity of the reaction interface can be activated, and a good effect can be obtained.

[0030]

Embodiments of the present invention will be described below. As the substrate, a substrate whose surface is insulated, for example, a thermally oxidized Si substrate, a quartz substrate, a sapphire substrate, or the like can be used. The surface of the substrate is preferably smooth, and a smoothing process such as chemomechanical polishing may be performed if necessary. A base electrode is formed as needed on the substrate, and a first ferromagnetic layer is formed on the base electrode. After forming a high resistance layer on the first ferromagnetic layer, a second ferromagnetic layer is formed, and if necessary, a reaction preventing layer is formed on the second ferromagnetic layer. This thin film is finely processed and processed into the general ferromagnetic tunnel junction device shown in FIG.
As a film forming method, a general thin film forming method such as a sputtering method, an MBE method, or an ion beam sputtering method can be used. As the fine processing method, a known fine processing method, for example,
A photolithography method using a contact mask or a stepper or a focused ion beam (FIB) processing method can be used.

As a method of forming the high resistance layer, a sputtering method, M
A general thin film formation method in a high vacuum such as a BE method or an ion beam sputtering method can be used, and a mechanism for introducing a reactive gas into a vacuum chamber and incorporating a radiation heating mechanism can be used. At this time, if a cooling mechanism is provided in the substrate holder, it becomes possible to increase the temperature gradient applied near the surface by radiation. As a mechanism of radiant heating, a method using a normal filament lamp, a halogen lamp, a mercury lamp, a strobe light source, a laser light source installed in a vacuum chamber, or a method of radiant heating through a window from outside the vacuum chamber can be used. . At that time, a shutter, a reflecting mirror, or the like is used as necessary.

Flash annealing means annealing in a short time, a method using a strobe light source, a lamp using a normal filament, a halogen lamp, a mercury lamp, a method using a condenser mirror and a high-speed shutter, a normal filament. , A halogen lamp, a mercury lamp, etc., a condenser mirror, a method using a light-shielding plate having a slit, and a substrate rotating mechanism can be used.

The above-mentioned methods are merely examples, and do not necessarily limit the present invention to the above-described specific examples.

(Embodiment 1) Five thermal oxide films are used as substrates.
Cu was prepared as a base electrode by RF magnetron sputtering on the Si single crystal wafer having a thickness of 2,000 mm. For the upper electrode, Cu produced by the same method was used. On the underlying electrode, Ta was deposited by DC magnetron sputtering at 30 °, and Ir ₂₀ Mn ₈₀ as an antiferromagnetic film was deposited thereon.
The film was formed while applying a magnetic field of 200 Oe at 0 °. On the antiferromagnetic layer, while the same magnetic field applied to the Fe ₇₀ Co ₃₀ as the first ferromagnetic layer and 100Å deposited. The second ferromagnetic layer is made of Fe ₇₀ Co ₃₀ of 30 °, followed by Ni ₈₀ Fe ₂₀ of 10 °.
0 °, produced by RF magnetron sputtering. Micromachining using photolithography method using a contact mask, the SiO ₂ by an RF magnetron sputtering method 300
A film was formed and used as an interlayer insulating film to be processed into an element. 4
The junction resistance and the rate of change in magnetoresistance were measured by the terminal method.
500O in the pin direction in a vacuum of 1 × 10 ^-5 torr or less
Heat treatment was performed for 1.5 hours while applying a magnetic field of e, and changes in characteristics were examined. The ultimate degree of vacuum at the time of film formation is 5 × 10 ⁻⁷ torr.
The film was formed as follows.

The interface layer was formed by RF magnetron sputtering or ion beam sputtering at an ultimate vacuum of 1 × 10 ⁻⁷ torr or less. In the case of a natural reaction such as natural oxidation as a reaction process for forming a high resistance layer, a method of introducing a reaction gas into a chamber and exposing the surface to the reaction gas for a predetermined time was used. The plasma reaction such as plasma oxidation is a method in which plasma discharge is performed in a state where a reactive gas is mixed in Ar gas, and the surface is exposed to plasma for a predetermined time. Reactive vapor deposition refers to a method in which a reactive gas is introduced when an interface layer is formed by sputtering or ion beam sputtering, and a film is formed while reacting. In the conventional example, the substrate heating uses a method in which a sheath heater is embedded in a substrate holder and heated by heat conduction from a portion where the substrate is in contact with the holder.

As a radiant light source, a lamp using a normal filament, or a mercury lamp and a condenser were installed in the chamber. Alternatively, an excimer laser was installed so that the substrate could be irradiated from outside the chamber through a window. During flash annealing, separate from the lamp shutter,
Between the shutter and the light source, a light-shielding plate having a slit of 5 mm width was provided on the light-collecting surface, and the light was passed over the slit by a substrate rotating mechanism.

Table 1 summarizes the processes used as the method for forming the high resistance layer and the device characteristics obtained as a result.

[0038]

[Table 1]

In Table 1, Al, Si, Ti, V, C
Similar results were obtained when r, Zr, Nb, Mo, Hf, Ta, and W were changed. O _{2 in} Table 1 was changed to N ₂ and A
Even if 1 was changed to B and C, the result of the same tendency was obtained. Similar results were obtained by changing the RF magnetron sputtering in Table 1 to DC magnetron sputtering, ion beam sputtering, or MBE deposition. Similar results were obtained by replacing the lamps in Table 1 with halogen lamps and mercury lamps.

As described above, by using the present invention, it is possible to obtain a ferromagnetic tunnel junction device superior to the conventional one.

[0041]

As described above, according to the present invention, the reaction between the interface layer and the reaction gas can be activated only near the surface by using radiation heating when producing a high resistance film. In addition, it is possible to manufacture a high-quality ferromagnetic tunnel junction device while suppressing the excessive reaction and diffusion of the reaction gas while improving the homogeneity of the high resistance film in the direction of the film quality and the chemical bonding state of the film.

[Brief description of the drawings]

FIG. 1 is a schematic view of a general ferromagnetic tunnel junction device.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11C 11/15 H01F 10/12 H01F 10/12 41/32 41/32 H01L 43/12 H01L 27/105 G01R 33/06 R 43/12 H01L 27/10 447 (72) Inventor Akihiro Odagawa 1006 Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Kenji Iijima 1006 Kadoma, Kazuma, Kadoma, Osaka Matsushita Electric Within Sangyo Co., Ltd. (72) Inventor Hiroshi Sakakima 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.F-term (reference)

Claims (13)

[Claims] 1. A conductive layer 1 including a ferromagnetic layer 1 of a metal or a compound at least within 5 nm from a junction interface;
In a tunnel junction element in which a conductive layer 2 including a ferromagnetic layer 2 of a metal or a compound within at least 5 nm from a junction interface is joined via a high-resistance layer 1, an interface layer 1 is formed first. 1 is formed into a high resistance layer 1 by heating in a reactive gas by radiation, or
A tunnel junction element, wherein the step of forming the interface layer 1 and heating by radiation in a reactive gas is repeated a plurality of times to form the high resistance layer 1, and a method of manufacturing the same. 2. A conductive layer 1 including a ferromagnetic layer 1 of a metal or a compound at least within 5 nm of a junction interface;
In a tunnel junction element in which a conductive layer 2 including a metal or compound ferromagnetic layer 2 is joined at least within 5 nm from a junction interface via a high resistance layer 1b, the high resistance layer 1b is connected to the interface layer 1b. A tunnel junction element and a method of manufacturing the same, characterized in that a film is formed while being heated by radiation in a reactive gas to form a high resistance layer 1b. 3. A conductive layer 1 including a ferromagnetic layer 1 of a metal or a compound at least within 5 nm from a junction interface;
In a tunnel junction element in which a conductive layer 2 including a ferromagnetic layer 2 of a metal or a compound within at least 5 nm from a junction interface is joined via a high-resistance layer 1c, the high-resistance layer 1c is connected to the interface layer 1c. A tunnel junction element and a method for manufacturing the same, characterized in that after forming a film in a reactive gas, the layer is heated by radiation to form a high resistance layer 1c. 4. A conductive layer 1 including a ferromagnetic layer 1 of a metal or a compound at least within 5 nm from a junction interface;
In a tunnel junction element in which a conductive layer 2 including a ferromagnetic layer 2 of a metal or a compound is bonded via a high-resistance layer 1d at least within 5 nm from a junction interface, the high-resistance layer 1d is connected to the interface layer 1d. A tunnel junction element and a method for manufacturing the same, characterized in that after forming a film in a reactive gas, the layer is heated by radiation in the reactive gas to form a high resistance layer 1d. 5. The tunnel junction element according to claim 1, wherein the radiation heating method is a flash annealing method. 6. The tunnel junction device according to claim 1, wherein the radiation heating method is a laser annealing method. 7. The tunnel junction device according to claim 1, wherein the heating by radiation is a pulse laser annealing method.
And its manufacturing method. 8. The absorptance of the wavelength used for radiant heating for the interface layer 1 is η1, and the absorptivity for the high-resistance layer 1 is η2.
8. The tunnel junction device according to claim 1, wherein a wavelength satisfying η1 <η2 is used. 9. An interface layer 1 comprising B, C, Al, Si, Ti,
9. The tunnel junction device according to claim 1, comprising at least one of V, Cr, Zr, Nb, Mo, Hf, Ta, and W, and a method for manufacturing the same. 10. The tunnel junction element according to claim 1, wherein the reactive gas is N, O, or a mixed gas thereof. 11. The high resistance layer is mainly composed of MaXb (M = B,
C, Al, Si, Ti, V, Cr, Zr, Nb, Mo,
At least one element selected from Hf, Ta, and W.
The tunnel junction element according to claim 1, wherein the light source used for radiant heating is a light source mainly having an absorption wavelength of an MX bond. And its manufacturing method. 12. The tunnel junction device according to claim 1, wherein an annealing time by radiation is 1 minute or less per time. 13. At the time of annealing by radiation, at least 10 nm from the surface of the interface layer 1 within a range of 5 nm or less.
13. The tunnel junction device according to claim 1, further comprising a thermal process in which a temperature gradient of not less than ° C./nm is formed.