JPH0778527A - Formation of thin film having preferential orientation therein - Google Patents

Abstract

PURPOSE:To form a thin film with preferential orientation in the surface on a substrate by generating plasma with specifically high density near the substrate on which a thin film is to be formed and forming a thin film while ionization ratio of particles being heightened. CONSTITUTION:A magnetic field is generated in the axial direction of a plasma gun 1 by a hollow coil 2 and an evaporation raw material 3 and an evaporation raw material hearth 4 are set on the opposite to the objective substrate with the axial of the plasma gun 1 as a center. Voltage is so applied to the plasma gun 1 as to make the hearth work as a positive pole to the plasma gun 1 by a plasma gun electric power source 7 and high density plasma with 10<9>/cm<3> plasma density is generated, the plasma is curved toward the hearth 4 on which a magnetic field with 5 gauss or higher is generated by a magnet 5, the evaporation raw material 3 is heated and evaporated, and thus a thin film is formed on the substrate 6 while the ionization ratio of particles to compose the thin film being heightened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thin film, which is an indispensable technique in the field of electronics and the like.

[0002]

2. Description of the Related Art As a method for forming a thin film, vapor deposition, sputtering, CVD and the like are known and widely used. However, when a thin film is formed on a polycrystalline or amorphous (glass, etc.) substrate using these methods, the orientation of the crystal axes of the thin film in the plane of the substrate becomes random, and the preferred orientation in the plane. No thin film was obtained.

[0003]

In order to use the electrical characteristics of a thin film, when the crystal of the thin film shows a random orientation, in the case of an ideal single crystal due to the disorder of the crystal orientation. It is shown that the electrical characteristics are deteriorated (especially, the mobility of electrons is lowered) compared with the above. When it is necessary to use in-plane anisotropy in electrical properties, it is indispensable to give the thin film a preferred orientation direction in the plane. It was impossible to form a thin film with in-plane preferred orientation on a polycrystalline substrate. An object of the present invention is to solve the above problems by forming a thin film having an in-plane preferential orientation on an amorphous or polycrystalline substrate.

[0004]

That is, according to the present invention, high-density plasma having a plasma density of 10 ⁹ / cm ³ or more is formed in the vicinity of a substrate on which a thin film is formed, and the ionization rate of particles forming the thin film is increased. Method for forming a thin film having in-plane preferential orientation characterized by film formation, preferential orientation in-plane characterized by forming a magnetic field of 5 gauss or more in the vicinity of a substrate on which the thin film is formed And a high-density plasma having a plasma density of 10 ⁹ / cm ³ or more in the vicinity of a substrate on which a thin film is formed to increase the ionization rate of particles forming the thin film and form the thin film. The present invention provides a method for forming a thin film having in-plane preferential orientation characterized by forming a film by forming a magnetic field of 5 gauss or more in the vicinity of a substrate.

The present invention uses a high density plasma for film formation and / or applies a magnetic field in an appropriate direction to give a thin film to be formed a preferred orientation direction in the plane of the substrate,
The purpose can be achieved. In addition, the in-plane preferential alignment film can be obtained under the above conditions regardless of the film forming method such as vapor deposition (including ion plating), sputtering, and CVD method.

It is desirable that the plasma density is 10 ⁹ / cm ³ or more, more preferably 10 ¹⁰ / cm ³ or more, in order to sufficiently increase the ionization rate of the particles formed with the thin film. The magnetic field formed in the vicinity of the substrate is preferably 5 gauss or more in order to align the orientation directions of the thin film to be formed. The upper limit of the magnetic field strength is 100
If it is about 00 gauss, it is sufficient to achieve such an object.

FIG. 1 is a conceptual sectional view of a vapor deposition apparatus which is an example of an apparatus for carrying out the present invention. 1 is a plasma gun,
Reference numeral 3 denotes a vapor deposition material (hereinafter also simply referred to as a raw material), 4 denotes a vapor deposition raw material hearth (hereinafter also simply referred to as a raw material hearth) which holds the vapor deposition raw material 3 and functions as one electrode of an electron beam, and 6 forms a thin film. It is a substrate to be.

As a high-density plasma supply source used in the present invention, it is preferable to use an arc discharge high-density plasma gun 1 capable of easily supplying a very high-density electron beam and plasma. The arc discharge type plasma gun 1 includes a compound cathode type plasma generator,
Alternatively, a pressure gradient type plasma generator or a plasma generator in which both are combined is preferable. Such a plasma generator is described in "Vacuum", Vol. 25, No. 10 (published in 1982).

The composite cathode type plasma generator has an auxiliary cathode having a small heat capacity and a main cathode made of LaB ₆ ,
The initial discharge is concentrated on the auxiliary cathode and heated in a short time, and the main cathode LaB ₆ is heated by using it to heat the main cathode LaB ₆
Is a plasma generator that performs arc discharge as the final cathode. For example, a device as shown in FIG.

As the auxiliary cathode 52, a coil of a refractory metal such as W, Ta or Mo, or a pipe-shaped one can be used. Reference numeral 53 is a disk made of W or the like for protecting the cathode, 54 is a cylinder made of Mo or the like, 55 is a disk-shaped heat shield made of Mo or the like, 56 is cooling water, and 57 is a cathode support base made of stainless steel or the like. , 58 are gas inlets.

In such a compound cathode type plasma generator, the auxiliary cathode 52 having a small heat capacity is intensively heated by the initial discharge to operate as the initial cathode and indirectly La.
Before the auxiliary cathode 52 reaches a high temperature of 2500 ° C. or higher and affects its life, it is a method of heating the B ₆ main cathode 51 and finally shifting to arc discharge by the LaB ₆ main cathode 51. The main cathode 51 of LaB ₆ is 1500 ° C-
It is a great advantage that it is heated to 1800 ° C., a large electron beam can be emitted, and a further temperature rise of the auxiliary cathode 52 can be avoided.

The pressure gradient type plasma generator is
An intermediate electrode is interposed between the cathode and the anode, and the cathode area is several Ts.
The discharge is carried out at about orr and the anode region is maintained at about 10 ^-3 Torr, and there is no damage to the cathode due to backflow of ions from the anode region, and in comparison with the discharge type without intermediate electrode. In addition, the gas efficiency of the carrier gas for producing the discharge electron beam is extremely high, and there is an advantage that a large current discharge is possible.

The composite cathode type plasma generator and the pressure gradient type plasma generator have the above-mentioned advantages, respectively. A plasma generator in which both are combined, that is, a composite cathode is used as a cathode and an intermediate electrode is used. Since the plasma generator having the above arrangement can also obtain the above advantages at the same time, the arc discharge type plasma gun 1 used in the present invention is also provided.
Is very preferable as

Next, the structure of the vapor deposition chamber 10 will be described with reference to FIG. A magnetic field is formed in the axial direction of the plasma gun by the air-core coil 2, and the direction of the magnetic field formed at that time is the output direction of the gun. Further, the vapor deposition raw material 3 and the vapor deposition raw material hearth 4 are arranged on the side opposite to the target substrate 6 with the axis of the plasma gun as the center.

A magnet 5 is arranged immediately below the vapor deposition hearth 4 for the purpose of bending the high-density plasma 9 containing the electron beam component in the direction of the hearth 4. In this case, in order for the magnetic field lines emitted from the plasma gun 1 to efficiently converge on the hearth 4,
The magnets 5 are arranged so that the hearth 4 becomes the S pole and the N pole from the side of the hearth 4, and a voltage is applied from the plasma gun power source 7 so that the hearth 4 becomes the anode with respect to the plasma gun 1 and the The vapor deposition material 3 is heated and evaporated by the electron beam. Further, the substrate 6 forming the thin film is arranged so as to face the hearth 4. At this time, the substrate 6 may be heated by the heater 11, and the substrate bias power supply 12 may apply a DC or RF voltage. When performing the reactive deposition, the reaction gas 13 is introduced.

[0016]

In the present invention, the high-density plasma increases the ionization rate of vapor deposition particles to allow the ITO film to be oriented in a direction not originally oriented, and the magnetic field has a function of aligning the orientation direction in one direction. it is conceivable that.

[0017]

[Example] Using a device as shown in FIG. 1, a raw material of In ₂ O ₃ (containing 7 wt% or more of SnO ₂ ) is heated by a high-density plasma beam and evaporated to form a transparent conductive film ( ITO) was prepared. At that time, a magnetic field of 100 G was applied parallel to the substrate. An ITO film was formed under the conditions of a substrate temperature of 200 ° C. and an oxygen partial pressure of 1 mTorr. The plasma density was about 10 ⁹ / cm ³ near the substrate.
In order to investigate the preferential in-plane orientation direction of this ITO film, evaluation was performed by the X-ray polar figure method (Pole figure method, which shows that the diffraction intensity in the shaded direction is high).

FIG. 3 shows a polar diagram of the (222) plane of the crystal of this film. The figure becomes dot-like, indicating that this film has in-plane preferred orientation. Reflecting this, the electric characteristics of this film have a specific resistance of 1.74 × 10 ⁻⁴ Ω · c.
m (mobility 41.0 cm ² / Vsec.) was excellent.

[0019]

[Comparative Example] For comparison, FIG. 4 shows a polar diagram of the (222) plane of the ITO film formed by the ordinary sputtering method (substrate temperature 300 ° C., oxygen partial pressure 2 mTorr). The plasma density was 10 ⁷ / cm ³ or less near the substrate, and no magnetic field was applied to the substrate. Substrate and ITO
The same raw material as that used in the example was used. The polar figure is ring-shaped, indicating that this film has no in-plane orientation.
Also, it is understood that the electrical characteristics of the film are inferior to those having the in-plane orientation with the specific resistance of 2.0 × 10 ⁻⁴ Ω · cm (mobility 38 cm ² / Vsec.

[0020]

EFFECTS OF THE INVENTION By applying the present invention, it becomes possible to form an in-plane preferentially oriented thin film on an amorphous or polycrystalline substrate which has been impossible in the past. As a result, the electrical properties and mechanical properties of the film are improved, and the properties can be made anisotropic.

[Brief description of drawings]

FIG. 1 is a conceptual cross-sectional view of a vapor deposition apparatus which is an example of an apparatus used in the present invention.

FIG. 2 is a sectional view of an example of an arc discharge type plasma gun used in the present invention.

FIG. 3 is an X-ray polar diagram of the (222) plane of the ITO thin film of the example.

FIG. 4 is an X-ray polar pattern of an ITO thin film prepared in a comparative example.

[Explanation of symbols]

1: Arc discharge type plasma gun 2: Air-core coil 3: Evaporation raw material 4: Evaporation raw material Hearth 5: Magnet 6: Substrate 7: Plasma gun power supply 9: High density plasma 10: Deposition chamber 11: Substrate heating power supply 12: Substrate bias power supply (DC or RF) 13: Reaction gas inlet 51: LaB ₆ main cathode 52: Ta pipe auxiliary cathode 53: W disk for protecting the cathode 54: Mo cylinder 55: Mo disk Heat shield 56: Cooling water 57: Cathode support made of stainless steel 58: Gas inlet

Claims (5)

[Claims] 1. A surface characterized in that high-density plasma having a plasma density of 10 ⁹ / cm ³ or more is formed in the vicinity of a substrate on which a thin film is formed, and the ionization rate of particles forming the thin film is increased to form the film. A method for forming a thin film having a preferred orientation in the interior. 2. A method of forming a thin film having in-plane preferential orientation, which comprises forming a film by forming a magnetic field of 5 gauss or more in the vicinity of a substrate on which the thin film is formed. ^3. A high density plasma having a plasma density of 10 ⁹ / cm ³ or more is formed in the vicinity of a substrate on which a thin film is formed to increase the ionization rate of particles forming the thin film, and 5 gauss in the vicinity of the substrate on which the thin film is formed. A method for forming a thin film having in-plane preferential orientation, characterized by forming the above magnetic field to form a film. 4. The method for producing a thin film having in-plane preferential orientation according to claim 2, wherein a magnetic field is formed parallel to the substrate. 5. The method for producing a thin film having in-plane preferential orientation according to claim 1, wherein an ITO film having in-plane preferential orientation is formed.