JPH04131381A - Formation of thin film - Google Patents

Abstract

PURPOSE:To remarkably reduce electric power consumption and to allow the formation of a thin film even on the side faces of an object having a rugged surface by imparting limited pulse forms to a microwave electric field and magnetic field generating electric power and further having a perfect synchronization in both pulse forms. CONSTITUTION:A magnetic field-possessing plasma CVD device is constituted by forming the microwave (1.5 to 300KW average electric power) for plasma generation and the magnetic field generating electric power for the purpose of generating plasma in the form of pulses and forming these pulses in such a manner that both pulse waveforms have the state respectively simultaneously turning on and simultaneously turning off. The atoms excited in the high energy state exist even in the position apart by 10 to 50cm from the region where the microwave electric field is maximized, i.e., the high-density plasma generating region if energy is kept applied to active species by simultaneously irradiating the active species with light in order to maintain the higher energy state even before the arrival of the high-density plasma on an object surface after this plasma is generated by the interaction between the pulse microwaves and the magnetic field. The thin film is thus formed in the larger space.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention applies a microwave electric field and an external magnetic field, and uses their interaction to introduce a reactive gas into a space or its vicinity, which is activated by plasma. imparting a limited pulse shape to microwave electric field and magnetic field generation power in forming a thin film by causing oxidation, decomposition or reaction to form a film on the entire surface of a thin film forming object;
Furthermore, it relates to a thin film synthesis method that achieves a significant power consumption range by developing complete synchronization of both pulse shapes.

[Prior art]

Conventionally, attempts have been made to form thin films using many methods, and it can be said that the diversification of methods such as CVD, sputtering, and MBE has led to many possibilities. In particular, active research and development including mechanism analysis is being carried out on the plasma CVD method, which attempts to form thin films through activation, decomposition, and reaction using plasma. Many have been proposed. In particular, the CVD method that uses magnetic field resonance (hereinafter referred to as magnetic field plasma CVD method) uses plasma with a much higher density than conventional methods and can form films with high efficiency, so development is progressing.
It has also been expected to be applied in many fields. However, in the field of actual industrial production, the application of the magnetic field Bradama CVD method has not progressed, even though it is possible to form a film of unprecedented high quality.

This is simply because the magnetic field plasma CVD method involves huge power consumption.

〔the purpose〕

The present invention utilizes magnetic field plasma CVD, which enables high-quality film formation.
In order for the law to have higher practicality as a production technology,
The goal is to provide effective operational technology.

[Structure of the invention]

According to the present invention, the object can be achieved by injecting microwaves and generating power of a magnetic field into such a magnetic field plasma CVD apparatus so as to have a pulse waveform.

Here, the pulse waveform given to the microwave/magnetic field power is shown in FIG. (A) is an example of a single rectangular pulse;
(B) is an example of a multistage rectangular pulse.

Such multi-stage pulses can be used, for example, in diamond thin films. Here, in diamond or hard carbon films, it is said that a structure constituted by SP3 bonds is preferable, and it is important to remove SP2 bonds, which are simultaneously generated during film formation. For this purpose, selective etching using H,0 plasma is usually performed. According to the present inventors, the dissociation energy of SP3 bond and SP2 bond is approximately 6.5, and the first peak is 5 to 50 KW, which is stronger than the second peak, which is 5/6 of 4. , 6-46K
By setting it to W, it is possible to more reliably increase the number of SP3 connections. It should be noted that, instead of a rectangular wave as shown in FIG. 3, a needle-like peak wave may be used as long as it is permitted under the synthesis conditions.

The magnetic field plasma CVD apparatus in the present invention usually uses EC
Much higher than what is known as R plasma CVD equipment, 0.3~30torr preferably 0°3~
The film is formed using high-density plasma using "hybrid resonance" at a pressure of 3 Torr, and the film is intended to be coated to a uniform thickness over the entire surface of a large-area substrate.

These film-forming objects are placed in the hybrid resonance space or a space apart from it that maintains an active state, and the reaction product is coated on the surface of the object. For this purpose,
An object having a surface to be formed is disposed in or near a region where the electric field strength of microwave power is maximum. In addition, in order to generate and sustain high-density plasma at a high pressure of 0.03 to 30 torr, the space containing the column is first filled with 1X
ECR (
(electron cyclotron resonance). Introducing gas, 0.03 to 30 torr, preferably 0.3 to 3 torr
The plasma state is maintained and changed to a high space pressure of rr, and the concentration of product gas per unit space in this space is about 102 to 104 times higher than that of the conventional ECRCVD method.

This makes it possible to form a film of a material that can only decompose or react under such high pressure.

For example, the aforementioned diamond, i-carbon (diamond or carbon coating with microcrystalline grains), high melting point metal or insulating ceramic coating. Furthermore, since the pressure is high, the mean free path of the reactive gas becomes short, making it easier for the reactive gas to diverge in all directions, making it possible to form a film even on the sides of objects with uneven surfaces.

That is, the present invention adds the force of a magnetic field to the conventionally known plasma CVD method using microwaves, and uses the interaction between the electric field and the magnetic field of the microwaves.

However, I X 10-' ~ I X 10-'tor
Effective ECR (Luctron Cyclotron Resonance) conditions were not used. The present invention utilizes high-density, high-energy plasma to form a film at a high pressure of 0.03 to 30 torr at which "hybrid resonance" occurs. By utilizing the high energy state in the hybrid resonance space, it has become possible to form thin film materials with excellent reproducibility.

Now, as mentioned above, the present invention provides a magnetic field plasma CVD apparatus with microwaves (average power 1
．． The magnetic field generation power is pulsed (5 to 30 KW), and the two are completely synchronized. In this case, it is possible to input microwaves and magnetic fields using pulse waves with a peak peak value of about 5.0 to 50 kW, so it is possible to input microwaves and magnetic fields using pulse waves with a peak value of approximately 5.0 to 50 kW. Compared to the case where power of 1.5 to 30 KW is input, an efficiency improvement of about 30 to 40% can be achieved, and the power consumption of the magnetic field plasma CVD apparatus can be reduced. Pulse wavelength of pulse wave is 1-10m
5, preferably 3-6 ms. Furthermore, since the strength of the applied magnetic field can be changed arbitrarily, it is possible to set resonance conditions not only for electrons but also for specific ions.

Furthermore, when pulses are used in the magnetic field plasma CVD apparatus, there is an advantage that the crystal grains of the formed thin film material become denser and uniform adhesion/deposition is achieved regardless of the unevenness of the film forming object. It also became clear.

Additionally, in addition to the configuration of the present invention, after generating high-density plasma through the interaction of pulsed microwaves and a magnetic field, the high-energy state is maintained even before reaching the object surface, so that light (e.g. When irradiated with ultraviolet light (ultraviolet light) at the same time and continuing to give energy to the active species, the area where the microwave electric field is maximum, that is, the area where high-density plasma is generated, is 10 to 50 cm away.
Even at a position as far away as m (a position where the active state of the reactive gas can be maintained), atoms excited to a high energy state exist, making it possible to form a thin film in a larger space. In the present invention, a cylindrical column was disposed in such a space, a film-forming object was disposed inside the twenty columns, and a film was formed on the surface thereof.

Examples will be shown below to further explain the present invention.

〔Example〕

FIG. 1 shows a microwave plasma CVD apparatus capable of applying a magnetic field used in the present invention.

In the same figure, this device consists of a plasma generation space (1) that can be maintained in a reduced pressure state, an auxiliary space (2), an electromagnet (5) that generates an L Curs magnetic field (5"), and its power source (2).
5).

Pulse microwave oscillator (4), turbo molecular pump (8) that constitutes the exhaust system, rotary pump (14), pressure adjustment valve (11), substrate holder (10''), film forming object (10), microwave Introduction window (15), gas system (6), (7), water cooling system (18), (18'),
Halogen lamp (20), reflecting mirror (21).

It consists of a heating space (3).

First, the thin film forming object (10) is placed on the substrate holder (10'),
Plasma generation space (
1). This substrate holder (10') was made of quartz so as not to disturb the microwave and magnetic field as much as possible.

As part of the fabrication process, the entire structure was first assembled using a turbo molecular pump (
8), I X 1.0-'to by rotary pump
Evacuate to below rr. Next, a non-product gas (a gas that does not constitute a post-decomposition reaction body), for example, hydrogen (6), is added to 303C
It is introduced into the plasma generation region (1) through the CM gas system (7), and the pressure is set to I x 10-'torr. In the drawing, the gas flows from the top to the bottom.

However, it may be from the bottom to the top, from the left to the right, or from the right to the left.

Here, a microwave with a frequency of 2.45 GHz is applied from the outside as a pulse with a peak value of 5 KW at a period of 8 ms. Magnet (
5) and (5'') are similarly applied at a period of 8 ms, and both are completely synchronized to generate high-density plasma in the plasma generation space (1).

From this high-density plasma region, high-energy non-product gas or electrons are released into the object (10') on the substrate holder (10').
0) and clean the surface. Next, while introducing this non-product gas, gases such as product gas (gas constituting the post-decomposition/reaction gas) such as carbide gas (acetylene (C2H2), ethylene (C
2H,) or methane (CH,), methyl alcohol (
CH30H), ethyl alcohol (C2H50H), etc.)
is introduced at a flow rate of 20 SCCM. Then, the pressure in the space is reduced to 0.0 while maintaining the already generated plasma state.
The pressure is changed to 3 to 30 torr, preferably 0.1 to 3 torr, for example 0.5 torr. By increasing the pressure in this space, the concentration of product gas per unit space can be increased and the film growth rate can be increased. At the same time, the circulation of gas can be increased. In this way, plasma can be generated once at a low pressure, and the active concentration of the product gas can be increased while maintaining the plasma state.

Then, high-energy excited atoms are generated and the substrate holder (
A thin film is formed on the object (10) above (10°).

In Figure 1, the magnetic field consists of two ring-shaped magnets (5),
A Helmholtz coil system using (5") was adopted.Furthermore, the strength of the electric and magnetic fields was investigated for the space (30) divided into four. The results are shown in Figure 2.

In FIG. 2 (A), the horizontal axis (X-axis) is the horizontal direction of the space (30) (reactive gas release direction), and the vertical axis (R-axis)
indicates the diameter direction of the magnet. The curves in the drawings indicate equipotential surfaces of the magnetic field. The number shown on the line indicates the strength of the magnetic field obtained when the magnet (5) is about 2000 Gauss. By adjusting the strength of the magnet (5), the space (100) (875 Gauss ± 18
(within 5 Gauss), it is possible to make the strength of the magnetic field approximately uniform over a large area over a wide area of the formation surface of the substrate. The drawing shows an isomagnetic scene, in particular the line (26) at 875
It is an isomagnetic scene that produces Gaussian ECR (electron cyclotron resonance) conditions.

The space (100) that produces this resonance condition is designed to be a region where the electric field is maximum, as shown in FIG. 2(B). The horizontal axis in FIG. 2(B) indicates the direction in which the reactive gas flows, as in FIG. 2(A), and the vertical axis indicates the strength of the electric field (electric field strength).

Then, in addition to the electric field region (100), the region (100") also corresponds to the region where the maximum occurs. However, the magnetic field corresponding to this region (Fig. 2 (A)) exists in many isomagnetic fields. That is, In the region (100'), the variation in film thickness in the diametrical direction (vertical axis direction in FIG. 2(A)) of the surface of the substrate becomes large, and the EC satisfies the resonance condition of (26').
Only a good quality film could be formed under the R condition. As a result, a uniform and homogeneous coating cannot be expected.

Of course, if you want to form a donut-shaped coating, you may do otherwise.

There is also a region on the opposite side of the origin symmetrical to region (100) where the electric field is maximum and the magnetic field is constant over a wide region. When there is no need to heat the substrate, forming a film in such a space is also effective for growth. However, it is difficult to find a way to heat without disturbing the electric field of pulsed microwaves.

As a result, considering the ease of loading and unloading the substrate and the ease of heating, the area (100) in Figure 2 (A) is the most industrially mass-producible of the three areas in order to obtain a uniform and homogeneous coating. It was an excellent location.

As a result, in the present invention, when the substrate (10) is disposed in the area (100), if this substrate is circular, the radius is 100.
It became possible to uniformly and homogeneously form a film with a radius of up to 50 mm, preferably up to 50 mm in radius.

For an even larger area, for example, to achieve the same uniform film thickness over an area four times larger than this, the frequency should be set to 2.45 GH.
If the frequency is set to 1.225 GHz instead of z, the diameter of this space (direction R in FIG. 2(A)) can be doubled.

In this example, using this method and using hydrogen-diluted methanol as a starting material, the average microwave output was 1.5 kW (peak value 3
．． Synthesis of a diamond thin film was attempted using a pulse cycle of 8 ms (4 kW) and a pulse period of 8 ms. When the cross section of the resulting thin film was observed using a scanning electron microscope, it was found that crystalline diamond had grown in the form of grains. In particular, the size of the grain is a steady value (
It was 5 to 10 times larger than when using continuous wave (continuous wave) microwaves.

Also, until now, some diamonds had a small diameter at the initial stage of growth, and as the thickness increased, some diamonds became thicker.
Adhesion to the surface to be formed was poor. However, in the pulse wave method of the present invention, the thickness of the diamond on the formation surface was large, and it was morphologically estimated that the diamond had good adhesion as a crystal. Furthermore, when an electron beam diffraction image was taken, diamond (single crystal grain) spots were observed, and the average output power was 1.
．． At 5KW or more, a film with a clearer diamond structure was obtained.

In addition, by using the method of the present invention, a polycrystalline film of silicon carbide can be formed on a substrate using a silicon carbide gas (methylsilane). It is also possible to flow the boronide and nitride simultaneously to form a boron nitride film, for example, by reaction of diborane with nitrogen. Bi (bismuth) type, YBCO
A thin film of an oxide superconducting material such as Tl (thallium) type, Tl (thallium) type, or (vanadium, non-copper) type oxide may be formed. Aluminum nitride, aluminum oxide, zirconia, and boron phosphide can also be produced in the same way. It is also possible to create a multilayer film of these and diamond. The formation on objects of films of high-melting point conductors of tanksten, titanium, molybdenum or their silicides can also be produced by decomposition reactions of the halides or hydrides of these metals themselves or by reaction of these with silane. .

〔Effect of the invention〕

Pulsed microwave/magnetic field plasma CVD in the present invention
It has become clear that thin film fabrication technology using this method can produce uniform thin film materials with lower input power than conventional methods using steady continuous waves. That is, the effects of pulsing in the present invention are that low energy consumption is realized and that a film can be formed even on the side surface of an object having an uneven surface.

By adopting the method of the present invention or experimentally discovered, it has become possible to widely apply the magnetic field microwave plasma CVD method, which is very promising for thin film production. Furthermore, compared to conventional methods, it has become possible to form a uniform thin film on a large surface with irregularities.

[Brief explanation of the drawing]

FIG. 1 schematically shows a microwave CVD apparatus using magnetic field/electric field interaction used in the present invention. FIG. 2 shows the magnetic field and electric field characteristics by computer simulation. FIG. 3 shows an example of the pulse form of microwave/magnetic field power. 1... Plasma generation space 4... Microwave oscillator 5.5''... External magnetic field generator 8... Turbo molecular pump 10... Film forming object or substrate 10...
Substrate holder 20...Halogen lamp 21...Reflector

Claims (2)

[Claims] 1. In the production of thin films using the plasma CVD method, which uses a magnetic field to generate high-density plasma, the input power for plasma generation and the input power for magnetic field generation each have a pulse waveform. , and the pulse waveforms of both are completely synchronized. 2. A method for producing a thin film, characterized in that the power input according to claim 1 is performed by microwaves.