JPS5824371B2 - Method for manufacturing silicon carbide thin film - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method of manufacturing a silicon carbide thin film.

The details relate to a method for manufacturing silicon carbide thin films that utilizes the high energy state within the plasma region of electrical discharge.The purpose of this is to produce silicon carbide thin films of several microns or smaller, which was previously considered impossible. The aim is to obtain thin films and to impart the excellent properties of silicon carbide to the surfaces of various materials.

Silicon carbide has been known as so-called carborundum, and its hardness is close to that of diamond, and it has been widely used as a thermoelectric material and an abrasive material.

In addition, in recent years, its applications as a semiconductor material in light emitting diodes and other applications have been studied and attracting attention.

However, at present, there are almost no attempts to reduce the thickness of silicon carbide.

Silicon carbide is synthesized by a gas phase reaction at a high temperature of up to 2000° C., but it is impossible to directly use this reaction as a means of forming a thin film due to the high temperature.

In an attempt to lower the temperature of this reaction, an example has been reported in which silicon tetrachloride and methane were reacted by a gas discharge, but this has not been put to practical use.

As a result of various studies on the production of silicon carbide, which has extremely excellent physical properties, on a substrate in the form of a thin film, the inventors of the present invention discovered that silicon carbide with a thickness of several microns or less can be produced at a relatively low temperature using a method using glow discharge. He invented a method for obtaining thin films.

That is, by glow discharge, alkylsilane or silane or alkylsilane and alkyl hydrocarbon are used as raw materials, and the raw materials are directly placed on a substrate that is electrically suspended in the plasma region of the glow discharge. A method for manufacturing a silicon carbide thin film, which is characterized by organically reactive growth, has been invented.

To briefly explain the glow discharge in the present invention,
This is a so-called glow discharge by polar discharge, and the inside of the container 1 is heated to about 1O-5 Torr using a device like the one shown in the figure.
After creating a vacuum state, the raw material gas is sucked in through the raw material suction port 4, and while adjusting the pressure to about 0.1 to 3 Torr, a high frequency current is applied to both electrodes 2 at a voltage of several hundred volts, and an electric discharge occurs. occurs between both electrodes 2.

The state in which this discharge reaches a steady state of continuation is called glow discharge.

In this glow discharge, the part 8 in the figure is a light emitting region commonly called a positive column, which is in a plasma state.

The present invention takes advantage of the fact that this plasma state has low energy macroscopically but very high energy microscopically, and gives sufficient activation energy to the introduced raw material to convert silicon carbide. It is intended to produce a reaction.

The present invention will be explained in detail with reference to the drawings. Substrates 7 to which a thin film of silicon carbide is to be attached are arranged in an electrically floating state as shown in the drawings in a portion 8 in an airtight container 1 that can be in a plasma state. The air inside the container 1 is removed using a vacuum pump 6 to create a vacuum of about 1 O-5 Torr.

Then, from raw material number 4, alkylsilane, silane and alkyl hydrocarbon, or alkylsilane and alkyl hydrocarbon are placed in a container.

1 and adjust the pressure to 0.1-3 Torr.

Then, when a high frequency current of several hundred volts is applied between the electrodes 2 at both ends of the container, a glow discharge state is created.

The temperature inside the container 1 is adjusted to a constant temperature of 200 to 400°C, and the electron energy in the plasma is set to 1 to 10 eV.

The source gas is activated and deposited on the floating substrate, where carbon and silicon are combined in a three-dimensional lattice to form silicon carbide crystal lattice macromolecules on the substrate surface and adhere as a thin film.

On the other hand, the hydrogen atoms become hydrogen gas and are exhausted from the exhaust outlet 5.
Served.

The reaction raw materials are supplied into the container 1 from the raw material inlet 4 while maintaining a constant pressure.

In this way, the silicon carbide thin film grows with the reaction, and when a thin film of an appropriate thickness is obtained, the power supply 3 is turned off, the reaction is stopped, and the substrate processed with the silicon carbide thin film is taken out.

Note that the high-frequency current in the present invention is an alternating current having a frequency of IK to 100 and a cycle of 7 seconds.

The raw material used in the present invention is alkylsilane alone,
It is a mixture of silane or alkylsilane and alkyl hydrocarbon, where alkylsilane is tetramethylsilane, tetraethylsilane, tetrapropylsilane,
Dimethyldiethylsilane, monomethyltriethylsilane, etc. have a total of 4 same or different alkyl groups on the silicon atom.
It refers to 3 pieces combined together.

There is no need to limit the number of carbon atoms in this alkyl group, but at least the alkylsilane is 0.1 to 3 Torr.
It is necessary to gasify the alkyl group at a pressure of 400° C. or lower, and the number of carbon atoms in the alkyl group is naturally limited.

3 In the present invention, alkylsilane alone may be used as the raw material, but as mentioned above, the same purpose can be achieved even if silane and alkyl hydrocarbon or alkylsilane and alkyl hydrocarbon are used as raw materials. Examples of the hydrocarbon 4 include methane, ethane, furopane, methane, pentane, etc., and the number of carbon atoms does not need to be particularly limited, but it must be able to be gasified under the reaction conditions.

In the present invention, the alkylsilane ions, silane ions and alkyl hydrocarbon ions, or alkylsilane ions and alkyl hydrocarbon ions, or their neutral gases that constitute the plasma chemically react by any mechanism to produce a thin film of silicon carbide. Although it is not clear whether the surface of the floating substrate immersed in the plasma is constantly irradiated with ultraviolet rays or soft X-rays with an energy of several eV to several tens of eV emitted from the plasma, It is assumed that the source gas molecules can be easily excited to activation energy and can sufficiently contribute to the progress of the reaction.

It is well known that the mechanism by which source gas molecules are deposited on the floating substrate 7 is due to the so-called plasma ion sheath phenomenon.

That is, in the plasma, the temperature of the electrons is two to three orders of magnitude higher than the temperature of the ions, so the electrons fly at a high speed, so the floating substrate is negatively charged by the collision and has a more negative potential than the plasma.

The vicinity of the substrate will then be surrounded by ions.

These ions reach the substrate surface, combine with electrons, and deposit.

As described above, the method of the present invention enables extremely uniform production of a thin film of several microns or less of silicon carbide on a substrate at a relatively low temperature of around 300 degrees Celsius, making it possible to produce a thin film of silicon carbide that was previously considered impossible. This is what made it possible.

This can be said to be particularly excellent in that there are few restrictions on the heat resistance of the substrate used.

As is well known, silicon carbide has extremely high hardness and excellent wear resistance, so by forming a thin film on the surface of various substrates, it can be applied in all fields as a wear-resistant protective film. Yes, the effect is enormous.

Furthermore, since the present invention does not contain harmful substances such as chlorine in its raw materials, it is possible to produce a silicon carbide thin film that is extremely suitable for use in electronic devices, so it can also be used as a thin film heating element by taking advantage of its semiconducting properties. Therefore, it can be applied as a particularly preferable material for other semiconductor electronic devices.

Example 1 A substrate for forming a silicon carbide thin film is electrically suspended in a glow discharge device as shown in the figure having a capacity of 4EM, and the inside of the container 1 is heated to 10-' Torr using a vacuum pump.
It was made into a vacuum.

Then 0.4 Torr of tetramethylsilane and 0.0 Torr of methane
．． A mixed gas having a partial pressure of 2 Torr was drawn into the vessel and the total pressure was adjusted to 0.6 Torr.

Immediately after inhaling this raw material gas, glow discharge was generated.

The conditions were a high frequency current with a frequency of 5 and a cycle of 7 seconds, a discharge voltage of IKV, and a current density in the cross section within the plasma region of 0.5 mAA.

Further, the reaction temperature was adjusted to 300°C. . As a result of reacting in this manner for 30 minutes, a thin film of silicon carbide having a thickness of about 300 OA was formed on the substrate.

The thin film was identified as silicon carbide by infrared and far-infrared spectroscopy.

Example 2 A substrate for forming a silicon carbide thin film was electrically suspended in the same apparatus as in Example 1, and the inside of the reaction vessel was evacuated to 10''-3 Torr using a vacuum pump.

Then, a mixed gas having a partial pressure of 0.4 Torr of tetramethylsilane and argon as an inert carrier gas was drawn into the vessel and the total pressure was adjusted to 0.6 Torr.

Immediately after inhaling this raw material gas, glow discharge was generated.

The conditions were a high frequency current with a frequency of 5 and a cycle of 7 seconds, a discharge voltage of 1000 V, and a current density in the cross section of the plasma region of 0.5 mA/i.

Further, the reaction temperature was adjusted to 300°C. In this way 3
As a result of the reaction for 0 minutes, a thin film of silicon carbide having a thickness of about 300 OA was formed on the substrate.

This thin film was identified as silicon carbide by infrared and far-infrared spectroscopy.

Application Example A thin film of silicon carbide having a thickness of about 500 OA was formed on the substrate under the same conditions as in the example, except that the reaction time was 60 minutes.

When this material was used as an abrasion-resistant film for a thin-film thermal printhead, it showed at least five times the abrasion resistance compared to thin films made of silicon dioxide, silicon monoxide, or the like.

[Brief explanation of drawings]

The figure is an example of an apparatus for carrying out the present invention. 1 is an airtight container, 2 is an electrode, 3 is a high frequency power source, 4 is a raw material inlet, 5 is an exhaust outlet, 6 is a vacuum pump, 7 is an electrically floating substrate, and 8 is a plasma region.

Claims (1)

[Claims] 1. By glow discharge, an alkylsilane, or an alkylsilane, or an alkylsilane and an alkyl hydrocarbon are used as raw materials, and on a substrate disposed in an electrically floating state within the plasma region of the glow discharge, A method for producing a silicon carbide thin film, which comprises directly reacting and growing the raw material.