JPH07335575A - Manufacture of thin film - Google Patents

Abstract

PURPOSE:To provide a method in which a metal thin film constituting an element is changed into a single-crystal film in order to enhance the reliability of a semiconductor element, a magneto-resistance element or the like and in order to increase the performance. CONSTITUTION:A film face is irradiated on a single-crystal substrate by making use of a plasma, a film is formed by making use of a plasma, the energy of particles sent out to a substrate face or the film face during the formation of the film is controlled so as to be within a range of 50 to 300eV, the film is formed, and an epitaxial growth operation is performed at a high speed of 0.1nm/sec or higher. Thereby, a high-quality metal single-crystal film or a high-quality single-crystal multilayer thin film can be manufactured on a substrate, having a large constant misfit, at a high speed of 10 times or higher as compared with conventional cases and with good reproducibility. By making use of it, a high-performance magnetoresistance element, a high-reliability metal interconnection film, a high-performance transistor and the like whose sensitivity is high and whose output is high can be manufactured easily.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is used for a magnetoresistive element used for a magnetic sensor, a metal wiring thin film and a metal electrode thin film used for a semiconductor device, so that each has a high sensitivity magnetoresistive element or excellent electromigration resistance The present invention relates to a method for manufacturing a single crystal metal thin film, which can be used as a wiring or an electrode through which high-speed electrons can pass without decelerating, and which enables manufacturing of a high-performance magnetoresistive element or a highly reliable semiconductor device.

[0002]

2. Description of the Related Art Metal thin films are important elements for constructing various functional devices. Typical examples thereof are a NiFeCo alloy thin film that constitutes a magnetic sensor, an Al-based alloy thin film for wiring used in semiconductor devices, and the like.
Since these metal thin films have different technical problems depending on their applications, it is customary that the technical ideas for solving the problems also differ. However, from the viewpoint of crystallinity, these metal thin films currently put into practical use have technical problems that are quite common. For example, a thin film in a polycrystalline state is used for a metal thin film used in a metal magnetoresistive element or a semiconductor device, etc., but if these are made into a single crystal thin film, it will be significantly superior in function. .
If the magnetoresistive element is a single crystal film, a large magnetocrystalline anisotropy appears and high sensitivity can be obtained. Especially recently Pa
The Co / Cu multilayer film found by rkin etc. and the Co / Cu / NiFe / Cu multilayer film by Shinjo et al. show a large magnetoresistive effect from 10% to over 50% at room temperature, but have low sensitivity. Therefore, it is difficult to apply for industrial application. In addition, Co /
The sensitivity is increased by using a single crystal for the Cu multilayer film. This is because the single crystal is used to increase the sensitivity by utilizing the magnetocrystalline anisotropy.

Al-based alloy thin films and the like are used for wiring films and the like in semiconductor devices, but they are one of the factors that reduce reliability such as disconnection due to electromigration, stress migration, etc. By using a film, it is possible to prevent disconnection and significantly increase reliability. Further, a transistor element using a metal electrode is promising as a high-speed operation device, but in order to allow electrons to pass at a high speed, it needs to be a single crystal metal. As described above, by monocrystallizing the polycrystalline metal film, it is possible to bring out the unique essential properties of the material and to exhibit a large function.

However, in order to manufacture a single crystal, in order to cope with the difference in the lattice constant between the single crystal substrate used and the film material, the substrate temperature during film formation is increased and the atoms on the surface of the crystal are removed. It is necessary to take into consideration such things as making it easy to move, and there is no choice but to use a special method with a low film formation rate. For example, the above-mentioned method for producing a single crystal of a Co / Cu multilayer film by Inomata uses a special method called an ion beam sputtering method, and the film forming rate is 0.02 nm / sec or less, which is very slow.
There is a problem in productivity for practical use. Further, the Al single crystal thin film production must be formed by a special method such as the MOCVD method, the MBE method, or the ion cluster beam film forming method, and it is difficult to put it into practical use because the film forming speed is slow.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is a magnetoresistive metal thin film for a high-sensitivity magnetoresistive element, a multilayer film, an electrode film used in a semiconductor device, or an electromigration resistant metal. An object of the present invention is to provide a method for manufacturing a single crystal metal thin film and a multilayer film for obtaining a wiring film.

[0006]

In order to achieve the above object, the present invention forms a metal thin film on a single crystal substrate having an absolute value of the lattice constant mismatch of 3% to 40% with the single crystal. In the film forming method, the plasma method is used to irradiate the film surface, and the energy of the particles that are formed by using plasma and irradiate the substrate surface or the film surface during film formation is 5 eV or less. Controlled to be in the range of 300 eV, 0.1 nm /
Provided is a method for producing a single crystal metal thin film, which comprises epitaxially growing a single crystal at a high speed of at least sec. In particular, the plasma method is an ECR sputtering method, and the voltage applied to the target is −
It may be controlled between 5V and -300V. Further, the first layer is formed by the above method, and then the sputtering method,
Provided is a method for producing a multilayer film of a single crystal metal thin film, which comprises forming a layer after the second layer on the first layer by using any one of a vacuum deposition method and a CVD method.

[0007]

The present invention will be described in detail below. The single crystal metal thin film is useful when used in a magnetoresistive element or a semiconductor device as described above. In that case, the substrate is silicon or gallium arsenide, strontium titanate,
Alternatively, it may be magnesium oxide or the like and may be various. Further, as the metal film, various materials such as aluminum, copper, nickel-based alloy, and cobalt-based alloy are used depending on the application. Therefore, it is rare that the lattice constant matches the film of the substrate. However, the misfit is 3% to 4 in absolute value.
In most cases, it falls between 0%. Further, usually, in order to obtain a single crystal of a metal thin film, a single crystal substrate having the same lattice constant as the crystal lattice of the thin film is used, and the thin film is epitaxially grown thereon. As a method therefor, the MBE method in ultrahigh vacuum is used. This is a technique in which the moving directions of vaporized film component atoms are aligned with the direction of the substrate, the atoms are ejected, and the atoms are deposited on the substrate. At this time, it is necessary to heat the substrate to several hundreds of degrees so that the atoms flying to the film surface on the substrate move freely on the film surface and settle in the correct atomic arrangement to promote surface diffusion of the atoms. In such a method, it is basically important to grow the film epitaxially while keeping the film in a thermal equilibrium state. Therefore, when the lattice constants between the substrate and the film are different, that is, when there is a lattice mismatch, it becomes difficult to grow epitaxially. In particular,
It is very difficult to perform single crystal epitaxial growth in the case where there is a large lattice mismatch by a sputtering method which has a high film forming rate and high productivity. Due to the lattice mismatch, the crystallinity is likely to be unstable during film formation. Also,
In the sputtering method, since the film is formed by exposing both the target and the substrate to the plasma atmosphere, various particles other than the atoms sputtered from the target are irradiated on the film surface. Among the effects of irradiation of the film surface, the irradiation effect of ions of several tens of eV removes impurities mixed in the film as residual gas components from the film, promotes diffusion of film atoms on the substrate, Alternatively, smoothing the film surface has the effect of creating a dense, high-quality film. However, irradiation with high-energy particles of several hundreds eV or more has an adverse effect by generating defects in the film, and further makes the crystallinity of the film unstable. Such high-energy particles include charged particles such as ions and electrons and high-energy particles such as neutral particles having no electric charge. Therefore, it is important to control the energy of these particles. The charged particles may be decelerated by applying an electric field by using an appropriate electrode.

In the ECR sputtering method, charged particles flow into the substrate surface by diffusion due to a magnetic field gradient, and the energy thereof is as small as several tens of electron volts. Therefore, it is possible to obtain the low-energy ion irradiation effect by eliminating the influence of irradiation by the high-energy charged particles without decelerating by the special electrode. However, the effects of irradiation with high energy neutrals remain.

In the sputtering method, mainly ionized gas molecules are attracted to and collide with the target, causing mechanical energy exchange between the ion particles and the target, and knocking out the atoms of the target. . However, at this time, there are a small number of ions that lose their charge without performing mechanical energy exchange. Such particles become recoil atoms (or molecules), and their energy is considered to be almost the same as the voltage applied to the target.

Usually, in the sputtering method, a voltage of several hundreds of volts or more is applied, so that the film surface is irradiated with neutral particles of several hundreds of electron volts or more, which disturbs the crystallinity of the film. become. Under such conditions, epitaxial growth will be significantly impeded, especially if the lattice mismatch between the substrate crystal and the film is large. However, the energy of such neutral recoil particles can be lowered by reducing the absolute value of the voltage applied to the target. By reducing the energy of the neutral recoil particles to less than 300 electron volts, the adverse effect on the crystallinity and epitaxial growth of the film will be eliminated.

Further, if the absolute value of the voltage applied to the target is too small, sputtering of the target ions will not be performed efficiently. The minimum absolute value of the applied voltage depends on the target material, but is preferably 5 V or more. Therefore, such a target applied voltage is appropriate in the range of -5V to -300V with the chamber at the ground potential, although there are some differences depending on the device. However, in order to obtain reproducible results, it is preferable that the voltage is in the range of -20V to -100V. In the conventional flat plate magnetron sputtering method,
At such a low applied voltage, stable discharge of plasma is hindered and stable film formation becomes impossible.

Further, in the ion beam sputtering method,
Due to the structure, most of the neutral gas molecules recoiled by the target fly in the direction of the substrate rather than in the direction of the substrate, so that the influence of the high-energy neutral particles is relatively small.
However, the stability is lacking because there are a small number of neutral particles that directly hit the substrate. Further, the film forming rate becomes very low, which is not practical.

In the ECR sputtering method, the plasma stability is not affected by the target applied voltage, and the charged particles of low energy of several tens of electron volts for irradiating the film are, as described above, a film of film atoms. Since in-plane diffusion is promoted and a film with high crystallinity is generated, even if there is a large lattice mismatch between the substrate crystal and the film crystal, epitaxial growth can be easily performed at a high film formation rate.

Further, as a method for growing crystals by irradiating the film surface with ions during film formation, there is an ion cluster beam film forming method, which is an atom (or atomic cluster) vaporized from a vapor deposition source with an electron. It is a method of irradiating, ionizing and flying to the film surface with low energy, but there are many unstable factors such as difference in ionization rate due to vapor deposition material, control of electrostatic lens system that accelerates ionized electrons, and film formation speed Is also slow.

There is also a method of preparing an ion gun for ion irradiation and irradiating argon ions or the like during film formation. However, it is a normal ion gun to irradiate a large amount of ions having an energy of several tens eV on the film surface. It is difficult, and even if it can be done, it cannot be said to be practical because the control of the electrostatic lens and the magnetic lens for energy control becomes complicated.
It is inferior to the ECR sputtering method.

Furthermore, if an epitaxial layer of several atomic layers is grown on the substrate by the ECR sputtering method, the surface can be easily epitaxially grown by the sputtering method. In this case, since the formation is made of a solid atomic arrangement, the film grows as a stable single crystal even when irradiated with high energy particles as pointed out in the ordinary sputtering method.

[0017]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of the ECR sputtering device. After evacuation to an ultimate vacuum of 5 × 10 ⁻⁷ Torr or less, 3.5 × 10 ⁻⁴ Torr of argon gas was introduced into the chamber 1. After that, in the plasma generation chamber 2, about 875 Gaus
A coil 3 having a magnetic field of s installed outside the plasma generation chamber 2.
It was applied from. After that, the plasma generation chamber 2 is set to 2.45.
A microwave of GHz is introduced to cause electron cyclotron resonance (ECR) to generate high density plasma. The plasma flows out in the direction of the substrate 4 along the magnetic field gradient generated by the applied magnetic field. A hollow cylindrical Ni80Fe20 alloy target 4 is disposed between the plasma generation chamber 2 and the substrate 4 so as to surround the plasma flow, and a voltage is applied to the target 5 to attract argon ions and perform sputtering. In this embodiment, the target potential of −30 V was applied with the chamber potential as the ground potential. The target current obtained was 0.5 A and the film formation rate was 0.25 n.
It was m / sec. Further, as the substrate 4, MgO (1
10) A single crystal substrate was used, and the substrate temperature was room temperature.

The X-ray diffraction pattern of this sample is shown in FIG.
From this figure, it can be seen that the Ni80Fe20 film has a (110) orientation. Since the Ni80Fe crystal has a face-centered cubic structure, the thin film has a dense crystal plane. It is energetically stable that the (111) plane is parallel to the substrate 4. Usually, in the case of a polycrystalline film, crystal grains having a (111) orientation and having random orientation are formed in the film surface. MgO substrate 4 and Ni8
The crystal mismatch with the 0Fe thin film is about -16% based on the crystal lattice constant of the substrate, which is close to about -20%.
Ordinary sputtering method, MBE method, or MOCV
Such orientation cannot be obtained by the D method.

Further, when the electron channeling pattern was observed for this sample, a clear channeling pattern was observed, and it was confirmed that the crystal orientations in the film plane were also uniform.
It was confirmed that the film was a single crystal. From the channeling pattern, it was confirmed that the crystal orientations in the film plane were also aligned, and that the film was a single crystal. From the channeling figure, the epitaxial relationship in the film plane is <001> Ni80.
Fe20 // <001> MgO, <11-0> Ni80
It was found to be Fe20 // <11-0> MgO. Furthermore, a large magnetocrystalline anisotropy was observed in the film plane, and the easy axis of magnetization was the <001> direction. It can be seen that when a magnetic field of 10 oersted is applied in the easy axis direction, the electric resistance change is about 5%, and the magnetoresistive effect is shown with high sensitivity.

(Comparative Example 1) Only the target applied voltage was-
The voltage was set to 500 V, and the other conditions were the same as in Example 1. The X-ray diffraction pattern of this example is shown in FIG. N compared to FIG.
The (220) diffraction line of the i80Fe20 thin film is weak,
1) It can be seen that the diffraction line is large. In this sample, no electron channeling pattern was observed in Si,
It was found to be polycrystalline. Further, no magnetic anisotropy was observed, and no magnetoresistive effect was observed. When a sample was prepared by changing the target applied voltage, it was confirmed that a single crystal thin film could not be formed if the absolute value of the applied voltage was 300 V or more. Furthermore, in the ordinary sputtering method, 20
A single crystal could not be formed even with an applied voltage of 0V. They are,
This is the effect of high-energy neutral recoil argon atoms.

(Example 2) Ni80Fe20 (1 nm) / Cu (6 nm) / Co on the MgO (110) substrate 4
(1 nm) / Cu (6 nm) in the order of 10
Layered twice. However, here, only Ni80Fe20 was produced by the ECR sputtering method, and for Co and Cu, the argon pressure was 4 × 10 ⁻³ Torr under the normal DC magnetron sputtering conditions, and the deposition rate was 0.25 for Cu.
nm / sec and Co were 0.3 nm / sec. FIG. 4 shows the X-ray diffraction pattern of this sample. Ni80Fe20,
The (220) diffraction peaks of Cu and Co overlap each other to form a single peak, and the modulation peak due to the multilayer film appears on both sides. In addition, one cycle 14 on the low diffraction angle side.
A long-period diffraction pattern corresponding to nm was also observed, and it was confirmed to be a single crystal. The epitaxial relationship between the substrate 4 and the multilayer film was the same as in Example 1. Also, within the film surface <
A large magnetic anisotropy having an easy axis of magnetization in the 001> direction was also observed. Further, a large magnetoresistive effect was also observed, and when a magnetic field was applied in the film inner surface <001> direction, which is the easy axis of magnetization, a high sensitivity of about 1% / oe was exhibited at a magnetic field of about 20 Oersted.

(Example 3) As the substrate 4, MgO (10
0) A substrate was used. Ni80Fe as the first layer on the substrate 4
20 thin films were grown to 0.6 nm by the ECR sputtering method, and then Cu thin films were grown to 500 nm by the DC magnetron sputtering method. As for the sputtering conditions, for ECR sputtering, the value of the target applied voltage was set to −15 V with respect to the chamber potential, and the other conditions were the same as in the case of Example 1. For magnetron sputtering, the film formation rate was 1 nm / sec. FIG. 5 shows the X-ray diffraction pattern of this sample. From the (200) peak of Cu, it can be seen that the (100) crystal plane is oriented parallel to the film surface. When an electron channeling pattern was observed for this sample, a channeling pattern was observed, and it was confirmed that the film was a single crystal film with a uniform crystallographic direction in the film plane. The in-plane epitaxial relationship is <010> Cu // <010> MgO, <00>
It was 1> Cu // <001> MgO. In this sample, the underlying Ni80Fe20 thin film is 0.6 nm, indicating that it has at most 3 atomic layers, but is still sufficient to provide epitaxial sites for Cu atoms flying on it. This sample is patterned and 250
A current having a current density of 1 × 10 ⁷ A / cm ² was passed in an atmosphere of ℃, and the time change of the electric resistance was observed, but the electric resistance hardly changed even after 2000 hours, and the electromigration resistance was good. Showed sex.

Example 4 The same results as in Example 3 were obtained when pure Co was used instead of Ni80Fe20 used as the underlayer material in Example 3. In addition, pure Ni
The same results as in Example 3 were obtained by using.

(Example 5) Si (100) as the substrate 4
A single crystal substrate was used. ECR of Ag on the first layer on the substrate 4
A film having a thickness of 0.5 nm was formed by a sputtering method, and a film of Cu was also formed thereon by an ECR sputtering method so as to have a thickness of 500 nm.
The ECR sputtering condition is that the target applied voltage is A
It was -5V for g and -20V for Cu. Other conditions are the same as those in the first embodiment. From the observation of X-ray and electron channeling pattern, (10
0) It was confirmed that an oriented Cu film was obtained. The epitaxial relationship is <010> Cu // <010> S in the film plane.
i, <001> Cu // <001> Si. Furthermore, when the current-carrying test shown in Example 4 was performed on this Cu film, the electric resistance did not change even after 2000 hours, and good electromigration resistance was obtained.

(Example 6) Instead of Cu used in Example 5, Al was used to form a film. That is, Si (10
0) 1 nm of Ag and 500 nm of Al were formed on the substrate 4 by the ECR sputtering method. The ECR sputtering conditions are the same as in Example 5. Al of this sample
The crystallinity of the film was also evaluated from the X-ray and electron channeling patterns. As a result, single crystal (100) oriented Al
It was confirmed that it was a film. The epitaxial relation is that <010> Al // <010> Si, <0> in the film plane.
It was 01Al> // <001> Si. Furthermore, this A
When the current-carrying test shown in Example 4 was performed on the l film, the electrical resistance did not change even after 2000 hours, and good electromigration resistance was obtained.

Example 7 Instead of Ag used in Example 6, an Au film was used for film formation. That is, Si (10
0) Au was deposited to a thickness of 1 nm and Al was deposited to a thickness of 500 nm on the substrate 4 by ECR sputtering. The ECR sputtering conditions are the same as in Example 5. The crystallinity of the Al film of this sample was also evaluated from the X-ray and electron channeling patterns. As a result, single crystal (100) oriented Al
It was confirmed that it was a film. The epitaxial relation is that <010> Al // <010> Si, <0> in the film plane.
It was 01> Al // <001> Si. Furthermore, this A
When the current-carrying test shown in Example 4 was performed on the l film, the electrical resistance did not change even after 2000 hours, and good electromigration resistance was obtained. Furthermore, similar results were obtained even when the base film Pd or Pt was formed under the same conditions.

[0027]

According to the method for producing a single crystal metal thin film disclosed by the present invention, a high quality metal single crystal thin film or a metal single crystal multilayer thin film is directed to a substrate having a large constant misfit, which is more than 10 times as large as the conventional one. It has become possible to manufacture at high speed and with good reproducibility. By utilizing this, it becomes possible to easily manufacture a high-performance magnetoresistive element having high sensitivity and high output, a highly reliable metal wiring film, a high-performance transistor, and the like.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an outline of an ECR sputtering device.

2 is a graph showing an X-ray diffraction pattern of the sample of Example 1. FIG.

FIG. 3 is a graph showing an X-ray diffraction pattern of a sample of Comparative Example 1.

FIG. 4 is a graph showing an X-ray diffraction pattern of the sample of Example 2.

FIG. 5 is a graph showing an X-ray diffraction pattern of the sample of Example 3.

[Explanation of symbols]

 1 chamber 2 plasma generation chamber 3 coil 4 substrate 5 target

Claims (3)

[Claims] 1. A method for forming a metal thin film having a lattice constant mismatch of 3% to 40% with respect to the single crystal on a single crystal substrate by using a plasma method, Irradiation is performed, and the energy of the particles that are deposited using plasma and that irradiate the substrate surface or the film surface during deposition is controlled to be in the range of 5 eV to 300 eV, and 0.1 nm / sec or more. 1. A method for producing a single crystal metal thin film, which comprises epitaxially growing a single crystal at high speed. 2. The single crystal metal according to claim 1, wherein the plasma method is an ECR sputtering method, and the voltage applied to the target is controlled between −5 V and −300 V with respect to the chamber. Thin film manufacturing method. 3. A method for forming a metal thin film having an absolute value of the lattice constant mismatch with the single crystal within 3% to 40% on the single crystal substrate, wherein the method comprises forming a metal thin film. Forming the first layer by the method described above, and then sputtering, vacuum deposition and CV.
A method for producing a single crystal metal thin film, comprising forming a second layer and subsequent layers on the first layer by using any one of the methods D.