JPH04329879A - Formation of diamondlike carbon film - Google Patents

Abstract

PURPOSE:To stably form a diamondlike carbon film having high adhesion to a base plate at the high rate of deposition. CONSTITUTION:When the diamondlike carbon film is formed on the base plate 7 in a reaction chamber 5 by ECR plasma CVD, benzene is used as gaseous hydrocarbon introduced into the chamber 5 and a reaction is allowed to take place in >=1X10<-3>Torr pressure. Microwave power is regulated to <=200W and high-frequency voltage is impressed so that self-bias generated on the base plate 7 is regulated to <=-300V.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for forming a hard carbon film used as a protective film for magnetic disks, magnetic heads, optical components, etc., and particularly relates to an ECR method.
(Electron Cyclotron Reson
ance: Electron Cyclotron Resonance) The present invention relates to a technique for forming a hard carbon film by a plasma CVD method.

0002

[Prior Art] Generally, DLC (Diamond Li
KE Carbon) films have recently attracted attention because they have excellent properties similar to diamond in terms of hardness, insulation, thermal conductivity, optical transparency, and chemical stability. Various methods are used to manufacture this DLC film, such as an ion beam method, a sputtering method, an ion plating method, and a plasma CVD method.

On the other hand, recently, as a type of plasma CVD method, ECR plasma CV, which can form high-quality films at low temperatures, has been developed.
Method D has been developed and is already in practical use. This EC
In the R plasma CVD method, high-density plasma is generated under low gas pressure by exciting electron cyclotron resonance, and this plasma flow is extracted by a divergent magnetic field from an ECR ion source and irradiated onto a sample such as a substrate to form a film. Is going.

0004

[Problems to be Solved by the Invention] When forming a DLC film on a substrate using the above-mentioned formation method, methane gas has conventionally been used as a reactive gas. A high compressive stress of about cm2 remains. Therefore, there is a problem in that the adhesion between the DLC film and the substrate, especially the metal substrate, is poor, and peeling, cracking, etc. occur during the formation of the DLC film.

[0005] In addition, D
When forming an LC film, there is a problem in that the rate of adhesion to the substrate is low.

Furthermore, when attempting to form a DLC film using the ECR plasma CVD method, film forming conditions are very important. In particular, it is greatly affected by the power of the microwave introduced into the plasma chamber, the self-bias generated in the substrate, and the reaction pressure. Among these conditions, the power of the microwave needs to be increased to some extent because it is necessary to decompose the reaction gas. However, if it is made too large, for example when methane gas is used as the reaction gas, the methane gas will be decomposed too much and a large amount of H radicals will be generated, which will be taken into the film and no DLC film will be produced. Furthermore, the self-bias needs to be increased to some extent because it is necessary to increase the acceleration energy of the ions. However, if the size is too large, the film may become graphitized and become graphite-like. Furthermore, the reaction pressure needs to be set to a certain level in order to promote the reaction, and if it is too low, a phenomenon similar to the above-mentioned case of excessive microwave power will occur, resulting in DL
It becomes difficult to generate a C film.

[0007] As described above, depending on the conditions (microwave power, self-bias, reaction pressure), a DLC film may not be formed on the substrate, and a polymer film or a graphite film may be formed.

The object of the present invention is to have high adhesion to the substrate;
The object of the present invention is to provide a method for stably forming a diamond-like carbon film with a high deposition rate.

[0009]

[Means for Solving the Problems] A method for forming a diamond-like carbon film according to the present invention includes introducing hydrocarbon gas into a reaction chamber to maintain a predetermined pressure inside the reaction chamber, and introducing microwaves into the inside of the plasma chamber. Plasma is generated by electron cyclotron resonance, and a predetermined high-frequency voltage is applied to the substrate placed in the reaction chamber.The ions in the plasma are irradiated onto the substrate by the self-bias generated thereby, and diamond carbon is deposited on the substrate. This method forms a film. This method uses benzene as the hydrocarbon gas and the reaction pressure in the reaction chamber is set to 1×10
-3 Torr or higher.

Preferably, as other conditions, the microwave power is set to 200 W or less, and the high frequency voltage is applied so that the self-bias generated in the substrate is -300 V or less.

[0011]

[Operation] In the method for forming a diamond-like carbon film according to the present invention, plasma is generated in a plasma chamber by electron cyclotron resonance, and this plasma stream is irradiated onto a substrate. At this time, since benzene is used as the hydrocarbon, the deposition rate is approximately 10 times faster than the conventional method using methane gas, and the compressive stress after film formation is approximately 1/1
It has decreased to 0.

On the other hand, when the microwave power is set to 200 W or less and the reaction pressure is set to 1 x 10-3 Torr or more,
Generation of a large amount of H radicals due to excessive decomposition of benzene is prevented. In addition, the self-bias generated in the substrate is -300
When a high frequency voltage is applied to the voltage below V, graphitization of the film is prevented.

[0013]

[Example] First, an ECR to which an embodiment of the present invention is applied
A plasma CVD apparatus will be explained. Figure 1 shows the ECR
FIG. 1 is a cross-sectional configuration diagram of a plasma CVD apparatus. In the figure,
The plasma chamber 1 receives microwaves (frequency 2.4
5 GHz), and is a cylindrical chamber with a diameter of 20 cm and a height of 20 cm, for example. A waveguide 3 having a rectangular cross section is connected to the plasma chamber 1 for introducing microwaves through a microwave introduction window 2 made of quartz or the like. Further, around the plasma chamber 1, electromagnetic coils 4a and 4b are arranged as a magnetic circuit for generating plasma. Electromagnetic coil 4
The strength of the magnetic fields a and 4b is determined so that the conditions for electron cyclotron resonance due to microwaves are established inside the plasma chamber 1. A diverging magnetic field that diverges downward is formed by the electromagnetic coils 4a and 4b.

00
14] Below the plasma chamber 1, a reaction chamber 5 is provided. At the bottom of the reaction chamber 5, a substrate holder 8 holds a substrate 7, which is irradiated with a plasma flow M extracted from the plasma chamber 1. The substrate holder 8 is attached to a support shaft 9. Further, a high frequency power source (eg, frequency 13.56 MHz) 11 is connected to the substrate holder 8 via a support shaft 9, so that a predetermined high frequency voltage is applied to the substrate 7. . In addition, high frequency power supply 1
1 is designed so that the applied voltage can be changed.

A shutter 12 that can be opened and closed is provided above the substrate holder 8. By adjusting the opening degree of the shutter 12, the irradiation of the plasma flow M onto the substrate 7 can be adjusted. Furthermore, a benzene gas inlet 5a is formed in the upper side surface of the reaction chamber 5. An exhaust port 5b is formed in the lower part of the reaction chamber 5.
is connected to an exhaust system (not shown). In addition, reaction chamber 5
The vacuum pressure and reaction pressure inside are measured by a vacuum gauge (not shown).

Next, a method for forming a diamond-like carbon film will be explained while explaining the function of the present apparatus. First, the substrate 7 on which a film is to be formed is held by the substrate holder 8 . Next, the plasma chamber 1 and the reaction chamber 5 are removed by an exhaust system (not shown).
into a vacuum state. Then, benzene (C6 H6) gas is introduced into the reaction chamber 5 from the benzene gas inlet 5a. Next, the electromagnetic coil 4 provided around the plasma chamber 1
A and 4b are energized so that the magnetic flux density at a predetermined position in the plasma chamber 1 becomes 875 Gauss. Further, at this time, no high frequency voltage is applied to the substrate 7. From this state, microwaves with a frequency of 2.45 GHz are introduced into the plasma chamber 1 via the waveguide 3 to generate plasma within the plasma chamber 1. The power of the microwave at this time should be 200W or less.

Under these conditions, in the plasma chamber 1, the frequency of the electrons rotated by the 875 Gauss magnetic field matches the microwave frequency of 2.45 GHz, causing electron cyclotron resonance. As a result, electrons efficiently absorb energy from microwaves and accelerate. The accelerated electrons collide with gas molecules and ionize the gas molecules, thereby generating high-density plasma in the low-pressure gas. At this time, increase the power of the microwave to 200W.
As the following is done, excessive decomposition of the reaction gas is suppressed,
Large amounts of H radicals are prevented from being generated. This plasma chamber 1
The plasma generated inside is drawn out along the lines of magnetic force of the diverging magnetic field formed by the electromagnetic coils 4a and 4b.

Next, a high frequency (13.56 MHz) is applied to the substrate 7 from the high frequency power supply 11. Then, the shutter 12 is opened. Then, the plasma flow drawn out from the plasma chamber 1 is irradiated onto the substrate 7, and a diamond carbon film is formed on the substrate 7. At this time, the high frequency power is adjusted so that the self-bias generated in the substrate 7 is -300V or less. By setting the self-bias generated in the substrate 7 within the above range, reactions on the film surface and in the film are promoted, and at the same time, graphitization of the film formed on the substrate is prevented. During film formation, benzene gas is introduced so that the reaction pressure within the reaction chamber 5 is maintained at 1×10 −3 Torr or higher. Therefore, excessive decomposition of benzene gas is suppressed and generation of a large amount of H radicals is prevented.

Example 1 Using the above apparatus, benzene gas was supplied at 100 sccm (s
standard cubic per minute
), the microwave power was 150 W, the self-bias generated on the substrate was -400 V, and the reaction pressure was 3
×10 −3 Torr. Also, as a substrate, a diameter of 3
An inch silicon wafer was used.

As a result, after 5 minutes, a thickness of approximately 55 mm was formed on the entire surface of the substrate.
A film of 0.00 angstroms was deposited. The hardness of the film is H
k (Knoop hardness)≈1500 kg/mm2, and the refractive index was about 2.4. From these results and Raman spectroscopy,
It was determined that a DLC film was formed. The compressive stress of this film was approximately 8×10 9 dyne/cm 2 .

Example 2 Using the apparatus of Example 1, benzene gas was heated for 100 seconds.
ccm flow rate and microwave power of 150W
, substrate self-bias at -400V, reaction pressure at 8.5
×10 −3 Torr. Also, as in Example 1, a silicon wafer with a diameter of about 3 inches was used as the substrate.

As a result, after 5 minutes, approximately 500
A film of 0 angstroms was deposited. The hardness of the film is Hk
The weight was ≒200 kg/mm2, and the refractive index was 2.2. From these results and Raman spectroscopy, it was determined that a diamond-like carbon film was formed. Note that the compressive stress of this film was approximately 5×10 9 dyne/cm 2 .

[0023]

Effects of the Invention According to the method for forming a diamond-like carbon film according to the present invention, the adhesion speed is increased by using benzene as a reactive gas, and compressive stress can be reduced, so that the diamond-like carbon film can be tightly adhered to the substrate. The degree increases.

[0024] Further, in the preferred method for forming a diamond-like carbon film according to the present invention, a diamond-like carbon film is produced under predetermined conditions of microwave power, self-bias of the substrate, and reaction pressure of the reaction chamber. Therefore, a diamond-like carbon film can be stably formed.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional configuration diagram of a diamond-like carbon film forming apparatus to which the present invention is applied.

[Explanation of symbols]

1 Plasma chamber 5 Reaction chamber 7 Board

Claims (1)

[Claims] Claim 1: Hydrocarbon gas is introduced into a reaction chamber to maintain a predetermined pressure inside the reaction chamber, microwaves are introduced into the plasma chamber to generate plasma by electron cyclotron resonance, and a A method for forming a diamond-like carbon film in which a predetermined high-frequency voltage is applied to a substrate, and ions in a plasma are irradiated onto the substrate by the self-bias generated thereby, thereby forming a diamond-like carbon film on the substrate. A method for forming a diamond-like carbon film, wherein benzene is used as the hydrocarbon gas, and the reaction pressure in the reaction chamber is set to 1 x 10-3 Torr or more.