JPH01167211A - Diamond-like carbon film and production thereof - Google Patents

Abstract

PURPOSE:To lower the film stress and improve the surface-smoothness of a diamond-like carbon film, by constituting the diamond-like carbon film with a layer containing large amount of amorphous carbon and a layer having low amorphous carbon content. CONSTITUTION:The diamond-like film is composed of (A) a diamond-like carbon layer having high amorphous carbon content and (B) a diamond-like carbon layer having low amorphous carbon content. Although the layer A has excellent surface smoothness, it has poor hardness, light-transmittance and electrical resistivity compared with the layer B. On the contrary, the layer B has high internal stress and rough surface, however, it has excellent hardness, light- transmittance and electrical resistivity compared with the layer A. When the layers A and B are alternately deposited in layers placing the layer A at the top, the internal stress in the layer B is absorbed by the layer A and the surface smoothness can be improved. The carbon film can be produced by periodically varying the reaction pressure in the vapor-phase synthesis of carbon film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a diamond-like carbon film and a method for producing the same, particularly having low internal stress and light transmittance.

This article relates to a carbon film with excellent surface smoothness and its manufacturing method.

[Conventional technology]

Diamond has excellent properties such as hardness, thermal conductivity, electrical insulation, transparency in the ultraviolet to infrared region, and chemical stability. The high-pressure method has been established as a method for synthesizing diamond, but it is not possible to synthesize diamond in the form of a thin film. Thin film diamond is used as a coating material for optical equipment lenses and windows.

Passivation film for semiconductor devices, heat dissipation substrate.

It has many uses, including diaphragms for audio equipment and carbide coatings for tools. As a conventional technique for forming a thin film diamond, as shown in Jikai 60-86096, plasma is generated by applying electromagnetic wave energy such as high frequency or microwave to a mixed gas of hydrocarbon such as methane and hydrogen. silicon wafers etc. whose surfaces have been polished
The second method is to precipitate diamonds. According to the prior art described above, it is possible to form a diamond thin film at a growth rate of 1 to several μm/h.

[Problem that the invention seeks to solve]

However, the above-mentioned conventional technology does not take into account film stress or film surface smoothness, and substrates with a slightly large surface area are prone to cracking, and the surfaces used for coating lenses and windows are rough. Therefore, the reflectance increases and the transmittance decreases, and since the surface of the protective film for the magnetic disk is rough, there are problems such as the inability to achieve a low flying height of the head.

An object of the present invention is to provide a diamond-like carbon film that has low film stress and excellent surface smoothness without deteriorating the properties of diamond or diamond-like carbon, and a method for synthesizing the same.

[Means for solving problems]

The above object is achieved by a film in which a diamond-like carbon film containing a large amount of amorphous carbon and a carbon film containing a small amount of amorphous carbon are deposited in alternating layers.

[Effect]

Diamond-like carbon films with a large amount of amorphous carbon have low internal stress and excellent surface smoothness, but have lower hardness, light transmittance, and electrical resistivity than diamond-like carbon films with a small amount of amorphous carbon. Relatively bad. On the other hand, a diamond-like carbon film containing a small amount of amorphous carbon has a large internal stress and a rough surface, but has relatively good hardness, light transmittance, and electrical resistivity. The two types of films are deposited alternately in layers, and the two most layers are diamond-like carbon films containing a large amount of amorphous carbon. With a layered structure, the stress in the layer with less amorphous carbon component is absorbed and reduced by the layer with more amorphous carbon component, and since the top layer is the layer with more amorphous carbon component, smoothness is improved. gets better. The diamond-like carbon film with the layered structure can be produced by a method of periodically changing the temperature of the substrate, a method of periodically changing the electromagnetic wave energy such as microwave or high frequency, a method of periodically changing the concentration of the carbon source, and a method of changing the reaction pressure. It is easily formed by a periodic method. In other words, when the substrate temperature and electromagnetic energy density are high and the carbon source gas concentration and reaction pressure are low, the hydrocarbon decomposition reaction progresses more easily, and the amount of hydrogen incorporated into the film is reduced, resulting in a diamond with less amorphous carbon content. A carbon-like film can be formed. On the other hand, when the substrate temperature and electromagnetic energy density are low and the carbon source gas concentration and reaction pressure are high, the hydrocarbon decomposition reaction does not progress, and the amount of hydrogen incorporated into the film increases, resulting in a diamond-like film with a high amorphous carbon content. A carbon film is formed. Therefore, by periodically changing the operating conditions, it is possible to form a diamond-like carbon film consisting of a layer with a high content of amorphous carbon and a layer with a low content of amorphous carbon.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

Methane 1 and hydrogen 2 are metered by flowmeters 3 and 4 and then supplied to plasma reactor 5. The pressure of the plasma reactor 5 is reduced by a vacuum pump 6. A microwave of 2.450 Ha is oscillated from the microwave oscillator 7, and the isolator 8. The power is applied to the plasma reactor 3 via a tuner 9 and a power monitor 10. The supplied gas is decomposed by the microwaves, producing radicals and ionic species. A silicon substrate 11 is placed on a substrate holder 12'' and exposed to plasma. The substrate is heated to 400~5o by microwave.
Although it is heated to O'C, it can be heated to a higher temperature by the heater 13.

Raw material gases include metals, saturated hydrocarbons such as ethane, propane, and butane, unsaturated hydrocarbons such as ethylene, propylene, and acetylene, alcohols such as methanol and ethanol, and acetone.

Ketones such as methyl-ethyl ketone, methyl ether,
Ethers such as ethyl ether can be used,
It may be mixed into water or a gas such as argon, if necessary.

As means for decomposing the raw material gas, in addition to microwaves, high frequency waves, radio waves, direct current plasma, etc. are used. Also,
A high temperature heat source such as a hot filament can be used.

The substrate is made of copper, gold, iron, and nickel in addition to silicon.

Metals such as tungsten, glass, and SiC.

Ceramics such as can be used.

In the present invention, a layer with a low content of amorphous carbon means a film in which a diffraction image based on diamond can be seen in at least X-ray diffraction, and a layer with a high content of amorphous carbon means a film that shows a diamond-based diffraction image in X-ray diffraction. It means a film with an electrical resistivity of 108 Ω·mark or more even if the original diffraction pattern is unclear.

The present invention will be explained below using specific examples.

[Example 1] Using the apparatus shown in FIG. 1, a diamond film was formed under the conditions shown below, and its physical properties were evaluated.

Reactor: Inner diameter 40nwnφ 100OW reaction time = 4n The obtained film shows diamond (111) by X-ray diffraction.
Only the diffraction patterns based on the (220) (311,) planes were clearly seen. Table 1 shows the measured physical property values. Hardness 2
Although the light transmittance of the inner film excluding the reflectance at the surface is excellent, the surface roughness and internal stress of the film are large.

Table 1 [Example 2] Using the apparatus shown in FIG. 1, a diamond film was formed under the conditions shown below, and its physical properties were evaluated.

Raw material gas: Methane concentration 10-30vo ]% Substrate: Silicon wafer (20mmφ) Pressure: 2O-60Ton Substrate temperature: 400-700°C Microwave output crab 300-600W Reaction time: 4n The obtained film was analyzed by X-ray diffraction So, Diamond's (111)
, (220) and (311) planes were observed, and others were unclear. This is thought to be due to the relatively large content of amorphous carbon components. However, the electrical resistivity was 10 8 Ω·0 or more, which was close to that of an insulator, unlike graphite and pyrolyzed amorphous carbon.

Table 2 shows the physical property values. Compared to the films shown in Table 1, the hardness and light transmittance are inferior, but the internal stress and surface smoothness are superior.

Table 2 [Example 3] Using the apparatus shown in FIG. 1, a diamond film was formed under the conditions shown below, and its physical properties were evaluated.

Raw material gas: Methane concentration 10vo1% Substrate: Silicon wafer (2011wnφ) Micro pumping crab 600W Reaction time = 4n fixed, pressure 20ton constant condition, substrate temperature varied in the range of 400 to 800°C (Case A
), the substrate temperature was kept constant at 70°C, and the pressure was 1 to 40 Torr.
An experiment was conducted for the case where the temperature was varied within the r range (Case B), and the physical properties of the obtained film were evaluated. The results are shown in Table 3.

Table 3 As a result, if a film with a layered structure consisting of a layer with a low amorphous carbon content and a layer with a high amorphous carbon content is formed, the defects of both layers can be compensated for, the internal stress is small, the surface smoothness is improved, and the optical It is clear that a membrane with excellent permeability can be formed.

〔Effect of the invention〕

According to the present invention, it is possible to form a diamond-like carbon film that has less internal stress than conventional ones and has excellent surface smoothness and light transmittance.

(II)

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention. 1... Methane, 2... Hydrogen, 5... Plasma reactor, 7... Microwave oscillator, 1]-Silicon substrate.

Claims (1)

[Claims] 1. A diamond-like carbon film comprising a diamond-like carbon layer with a high content of amorphous carbon and a diamond-like carbon layer with a low content of amorphous carbon. 2. A method for manufacturing a diamond-like carbon film consisting of a diamond-like carbon layer with a high content of amorphous carbon and a diamond-like carbon layer with a low content of amorphous carbon. A method for producing a diamond-like carbon film characterized by synchronously changing the 3. The method for producing a diamond-like carbon film as described in Figure 2, which is characterized in that the temperature of the substrate is periodically changed in the synthesis method from the gas phase. 4. The method for producing a diamond-like carbon film according to item 2, characterized in that in the gas phase synthesis method, the energy of electromagnetic waves such as microwaves and high frequency waves applied to the raw material gas is periodically changed. 5. The method for producing a diamond-like carbon film according to item 2, characterized in that the concentration of the carbon film is periodically changed in the synthesis method from the gas phase.