JPH1088357A - Plasma cvd process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form thin coating having a high density and thermal stability by prescribing the ratio in the flow rate between a rare gas and a gas other than the rare gas and the energy density of electric power. SOLUTION: Af first, the pressure in a coating forming chamber is regulated to 1 to 10mtorr. By regulating the pressure to this range, discharge is made stable, and the reduction of the energy of particles arriving at a substrate is suppressed to obtain homogeneous coating. Next, a gas for forming deposited coating in accordance with the kind of the coating to be formed and a rare gas for generating plasma are introduced therein. As the rare gas, particularly, argon is preferably used. In this place, the value obtd. by dividing the flow rate of the rare gas by the flow rate of the gas other than the rare gas is regulated to 4 to 7. Then, for generating plasma, microwave electric power is introduced therein. In this case, at the time of using a waveguide with slots, the microwave electric power per unit area of a dielectric member can be reduced. The energy density of the microwave electric power to be introduced to the gas other than the rare gas is regulated to >=4500J/cm3 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma CVD method for forming a protective film for a semiconductor element or an electronic device, and more particularly to a plasma CVD method which can be used for manufacturing a protective film for an optical recording medium.

[0002]

2. Description of the Related Art Reduction of manufacturing costs is an important issue in promoting the spread of optical recording media. The manufacturing process of an optical recording medium includes substrate molding, film formation, overcoating, mounting, and the like. Among these, the film formation process is particularly costly.
The film forming step is a step of sequentially forming a protective film, a recording film, a dielectric film, a reflective film, and the like on a substrate by a sputtering process. Among them, it is strongly desired to increase the speed of forming a protective film having a relatively large thickness and a long production time.

In this regard, in recent years, ECR (electron c
The application of plasma CVD such as yclotron resonance) has been actively studied. The film formation by the ECR plasma CVD method is performed, for example, as follows. Figure 2 shows the ECR
It is a figure showing a plasma CVD device. A source gas is introduced into a film forming chamber of this apparatus. On the other hand, microwave power is introduced into the plasma generation chamber, and the magnetic field strength of the electromagnet is increased to a magnetic force at which electron cyclotron resonance occurs, thereby generating plasma. The generated plasma reacts with the source gas in the film formation chamber to form a deposited film on a substrate placed in the film formation chamber. According to this method, there is an advantage that a film can be formed at a higher speed than a normal sputtering method, and a film having excellent denseness and a small internal stress can be obtained.

[0004]

However, even when the above method is used, there is a certain limit in increasing the film forming speed. For example, when the above method was applied to the manufacture of a magneto-optical recording medium, when the gas flow rate was increased to increase the deposition rate, the denseness and thermal stability of the film were reduced, and the resulting magneto-optical medium was It was confirmed that the durability was reduced.

In the above method, in order to increase the deposition rate while maintaining good film quality, the substrate temperature is increased to activate the substrate surface reaction, the microwave power is increased to increase the density of the plasma, For example, the effective film formation area is increased, the number of pieces to be taken is increased, and the production tact is shortened. However, in the method of raising the substrate temperature, glass or the like having a high heat-resistant temperature is expensive and cannot be mixed from the viewpoint of manufacturing cost. There is a practical limit to increasing the microwave power as described above. This is because applying an excessive amount of electric power will destroy the dielectric member. For example, in the case of a high-purity alumina dielectric member, although it depends on the cooling method, about 15 W / cm ² per unit area of the dielectric member, and about 1800 J / cm ^{3 in} terms of energy density for a gas other than the rare gas. Power can only be turned on up to this point. For further methods, the ECR describes 2.
Since a strong magnetic field of 875 gauss is required for a microwave of 45 GHz, a huge magnet is required for enlarging the film formation area, which is not realistic in view of cost. In addition, generation of magnetic force distribution is also a problem.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an EC
It is an object of the present invention to solve the above-mentioned problems in the R plasma CVD method and to provide a method for forming a thin film having high density and high thermal stability at high speed.

[0007]

According to the plasma CVD method of the present invention for solving the above-mentioned problems, the value obtained by dividing the flow rate of the rare gas by the flow rate of the gas other than the rare gas is 4 or more and 7 or less. The value of the energy density obtained by dividing the value by the flow rate of the gas other than the rare gas is 4500 J / cm ³ or more.
000 J / cm ³ or less.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a microwave plasma CV using an annular waveguide with a slot.
It is sectional drawing of D apparatus. The apparatus includes an exhaust unit (not shown), a pressure gauge, and the like.

First, the substrate 3 is placed on the support 4 in the film forming chamber 1. As the material of the substrate, polyethylene, polyester, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride,
Organic resins such as polystyrene and polyamide are exemplified.

Next, the film formation chamber is sufficiently evacuated by exhaust means (not shown), gas is introduced, and the pressure is adjusted to a desired pressure by a conductance valve (not shown) provided on the exhaust side. Microwave plasma C by the plasma CVD method of the present invention
The pressure of the film forming chamber 1 in the VD apparatus is 0.1 mtorr or more and 1
It is preferably set to 0 mtorr or less. By setting the pressure in such a range, the discharge becomes stable, and a decrease in energy of particles reaching the substrate due to an increase in collision frequency between radicals and ion species in plasma can be suppressed. A membrane can be obtained. In consideration of the evacuation capacity of the apparatus, the stability of discharge, and the like, the pressure is more preferably 2 mtorr or more and 10 mtorr or less.

Next, a gas for forming a deposited film and a rare gas for generating plasma are introduced through a first source gas introducing pipe 6, a second source gas introducing pipe 7, and a third source gas introducing pipe 8. As the gas for forming a deposited film, a generally known gas can be used. It is desirable that a gas which is easily decomposed by the action of plasma and can be deposited alone can be introduced into the film formation chamber. This is because a composition having a stoichiometric ratio is easily realized, and film deposition in the plasma generation chamber is prevented. Further, it is desirable to introduce a gas that is not easily decomposed by the action of the plasma and that is difficult to be deposited alone by itself into the plasma generation chamber.

A gas selected according to the type of a film to be formed is introduced from a source gas introduction pipe. For example, when forming a Si-based semiconductor film such as a-Si, poly-Si, SiC, etc.
Inorganic silanes such as H ₄ and Si ₂ H ₆ , organic silanes such as tetraethyl silane (TES), tetramethyl silane (TMS) and dimethyl silane (DMS); SiF ₄ and Si ₂ F
₆ , SiHF ₃ , SiH ₂ F ₂ , SiCl ₄ , Si ₂ Cl ₆ ,
SiHCl ₃ , SiH ₂ Cl ₂ , SiH ₃ Cl, SiCl ₂
Halosilanes such as F _{2 and the} like which are in a gaseous state at normal temperature and normal pressure or those which can be easily gasified are used.

When a thin film of a Si compound such as Si ₃ N ₄ or SiO ₂ is formed, inorganic silanes such as SiH ₄ , Si ₂ H ₆ , etc. Tetraethoxysilane (TEOS), Tetramethoxysilane (TMOS), Octamethylcyclotetrasilane (OM
Organic silanes such as CTS), SiF ₄ , Si ₂ F ₆ , Si
HF ₃ , SiH ₂ F ₂ , SiCl ₄ , Si ₂ Cl ₆ , SiHC
_{l 3, SiH 2 Cl 2,} SiH 3 Cl, SiCl 2 F 2 halosilanes such _{as, H 2 S, SO 2,} SP 4, SF 6, Zn (CH
₃ ) ₂ , Zn (C ₂ H ₅ ) _2, etc. which are in a gaseous state at normal temperature and normal pressure or which can be easily gasified are used. In this case, the raw materials introduced through the second raw material gas introduction pipe 7 include H ₂ , N ₂ , NH ₃ , N ₂ H ₄ , hexamethyldisilazane (HMDS), O ₂ , O ₃ , H ₂ O, N
O, N ₂ O, NO _{2 and the} like are used.

Helium, neon, argon, krypton, xenon, and radon are used as the rare gas used as the plasma generating gas. Preferred are helium, neon, argon and xenon, with argon being particularly preferred. Here, the value obtained by dividing the flow rate of the rare gas by the flow rate of the gas other than the rare gas is set to 4 or more and 7 or less. If this value is less than 4, the resulting film has insufficient denseness and thermal stability, and if it exceeds 7, the concentration of high-energy particles becomes too high and the gas may be excessively excited. Although there are many unclear points about the action of the rare gas, it is considered that increasing the rare gas has a kind of plasma cooling effect. This is because, when the energy density of microwave power is increased above a certain value,
Although problems such as melting of the polycarbonate substrate occur, such problems can be avoided by increasing the flow rate of the rare gas.

Next, microwave power for generating plasma is introduced into the plasma generation chamber 2. The frequency of the microwave power supply is preferably from 500 MHz to 50 GHz. Known waveguides are used. While slotted waveguides are preferably used, slotted annular waveguides are more preferably used. Slotted waveguides are slots (holes) for leaking microwaves into the plasma chamber.
It has. The slots are arranged at equal pitch in the direction perpendicular to the plane of polarization. By setting the pitch to an integral multiple of 波長 of the wavelength of the microwave in the waveguide, it is possible to eliminate the phase cancellation in a ring-shaped closed shape (annular shape). By using a slotted waveguide, microwaves can be introduced into the plasma generation chamber in a dispersed manner from many slots. For this reason, the microwave power per unit area of the dielectric member can be reduced as compared with the case where microwaves are introduced from one place like ECR plasma. Therefore,
It is possible to dramatically increase the energy density. The microwave power to be introduced is set so that the energy density of a gas other than the rare gas is 4500 J / cm ³ or more. This is because if it is less than 4500 J / cm ³ , the resulting film is inferior in denseness and thermal stability.

As described above, plasma is generated by the microwave, the gas for film formation reacts, and 10 to 3
A deposited film of about 00 nm is formed.

[0017]

The present invention will be described in detail with reference to the following examples. The scope of application of the present invention is not limited to the optical recording media described in these embodiments. (Embodiment 1) An example of a method for manufacturing a magneto-optical disk using the plasma CVD method of the present invention will be described with reference to FIG. In this embodiment, the plasma CVD method of the present invention is applied to a process of forming a protective film made of silicon nitride.
Here, the protective film refers to a film that plays a role of improving the signal-to-noise ratio (CN ratio) by increasing the Kerr rotation angle and a role of protecting the recording film.

First, a substrate having a diameter of 86 mm and a thickness of 1.
A 2 mm pregrooved polycarbonate substrate was prepared. Next, the substrate 3 was placed on the support 4 and the inside of the film forming chamber 1 was evacuated by an exhaust system (not shown) to reduce the pressure to 10 ^-6 torr. Next, SiH _{4 is} supplied from the first raw material gas introduction pipe 6.
At a flow rate of 10 sccm from the second source gas introduction pipe 7 to N _2.
Is introduced into the plasma generation chamber 1 at a flow rate of 5 sccm, Ar is introduced into the plasma generation chamber through the third source gas introduction pipe 8 at a flow rate of 105 sccm, and a conductance valve (not shown) provided on the exhaust pipe 5 side is provided. ) To maintain a pressure of 8 mtorr. Further, 1125 W power oscillated from a 2.45 GHz microwave power supply (not shown) was introduced into the plasma generation chamber via the slotted waveguide 9 and the dielectric member 10 to generate plasma. As a result, the N ₂ gas was excited and decomposed in the plasma generation chamber to become active species, diffused and transported in the direction of the substrate 3, reacted with the SiH ₄ gas, and a protective film made of a silicon nitride film was formed on the substrate. The film thickness was 75 nm. After the formation of the protective film, a recording film, a dielectric film, and a metal reflection film were formed using a general parallel plate type magnetron sputtering device (not shown). The recording film is a magnetic film,
For the film formation, a TbFeCo ternary target made of a ferrimagnetic material having a high transition metal composition ratio was used. The film thickness is 20
nm. The dielectric film is made of silicon nitride. Using a silicon target, N ₂ gas was introduced into the film formation space to form a film by reactive sputtering. The film thickness was 30 nm. The metal reflective film is made of aluminum and has a thickness of 50
nm.

For the purpose of evaluating the thermal stability of the obtained magneto-optical disk, a recording / reproduction durability test was performed on the same track. The magneto-optical disk was rotated at a rotation speed of 3000 rpm, a position having a radius of 24 mm was irradiated with a light beam having a wavelength of 780 nm, and 2T pattern recording was repeated 10 ⁵ times under the condition of a recording magnetic field of 315 Oe. The reproducing power was 1 mW, the erasing power was 5 mW, and the bottom power was 1 mW. Table 1 shows the results of the evaluation performed as described above. The decrease in CN ratio was 0.3 dB. This is a level equivalent to that when a protective film is formed by a sputtering method, and it has been shown that the protective film obtained by the present invention has sufficient denseness and thermal stability. That is, the plasma CVD of the present invention
It has been shown that by using the method, good film performance can be realized while speeding up the film formation. (Example 2) An example of a method for manufacturing a magneto-optical disk using the plasma CVD method of the present invention will be described. In this embodiment, the plasma CV of the present invention is used in the process of forming the protective film made of silicon carbide.
The method D is applied. Si as the first source gas
H ₄ was supplied at a flow rate of 10 sccm, and C ₂ H ₂ was used as the second source gas.
At a flow rate of 15 sccm and Ar as a third source gas at 12 sccm.
A protective film made of silicon carbide was formed at a flow rate of 0 sccm at a pressure of 10 mtorr and a microwave power of 2.0 kW. Other conditions were the same as in Example 1 to produce a magneto-optical disk. Table 1 shows the results of the recording durability test performed in the same manner as in Example 1. The decrease in the CN ratio was 0.4 dB, indicating that the protective film obtained by the present invention had sufficient denseness and thermal stability. (Embodiment 3) An example of a method of manufacturing a magneto-optical disk using the plasma CVD method of the present invention will be described. In this embodiment, the plasma CV of the present invention is used in the process of forming the protective film made of silicon oxide.
The method D is applied. Si as the first source gas
H ₄ at a flow rate of 10 sccm and O ₂ as 1
At a flow rate of 0 sccm, 100 sc of He is used as the third source gas.
cm flow, pressure 8 mtorr, microwave power 1.
At 5 kW, a protective film made of silicon oxide was formed. Other conditions were the same as in Example 1 to produce a magneto-optical disk. Table 1 shows the results of the recording durability test performed in the same manner as in Example 1. The decrease in CN ratio is 0.5 dB,
It was shown that the protective film obtained according to the present invention had sufficient compactness and thermal stability. Comparative Example 1 A magneto-optical disk was produced in the same manner as in Example 1 except that a protective film for the magneto-optical disk was formed by a conventional plasma CVD method (low microwave power). A recording durability test was performed on the obtained disk in the same manner as in Example 1. Table 1 shows the results. The fluctuation of the CN ratio before and after the test was large, indicating that the denseness and thermal stability of the protective film were insufficient. Comparative Example 2 A magneto-optical disk was produced in the same manner as in Example 2, except that a protective film for the magneto-optical disk was formed by a conventional plasma CVD method (low microwave power). A recording durability test was performed on the obtained disk in the same manner as in Example 1. Table 1 shows the results. The fluctuation of the CN ratio before and after the test was large, indicating that the denseness and thermal stability of the protective film were insufficient. Comparative Example 3 A magneto-optical disk was produced in the same manner as in Example 3, except that a protective film for the magneto-optical disk was formed by a conventional plasma CVD method (low microwave power). A recording durability test was performed on the obtained disk in the same manner as in Example 1. Table 1 shows the results. The fluctuation of the CN ratio before and after the test was large, indicating that the denseness and thermal stability of the protective film were insufficient. (Comparative Examples 4 and 5) A protective film made of silicon nitride was formed and a magneto-optical disk was manufactured in the same manner as in Example 1 except that the flow rate of the source gas was changed. As in the first embodiment, the first
SiH ₄ , N ₂ from the second source gas inlet 7, and Ar from the third source gas inlet 8 were introduced. Table 2 shows the flow rate of each gas. A recording durability test was performed on the obtained disk in the same manner as in Example 1. Table 1 shows the results. The fluctuation of the CN ratio before and after the test was large, indicating that the denseness and thermal stability of the protective film were insufficient. (Comparative Examples 6 and 7) A protective film made of silicon nitride was formed in the same manner as in Example 1 except that the pressure in the film forming chamber was changed, and a magneto-optical disk was manufactured. A recording durability test was performed on the obtained disk in the same manner as in Example 1. Table 1 shows the results
Shown in In Example 6, the change in the CN ratio before and after the test was large, and in Example 7, the CN ratio was already poor at the initial stage, indicating that the denseness and thermal stability of the protective film were all insufficient. Was.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

According to the present invention, good film characteristics are realized while taking advantage of the feature of plasma CVD that high-speed film formation is possible at a low temperature. When used in the manufacture of an optical recording medium, it is possible to reduce the manufacturing cost by increasing the speed of film formation and to provide an optical recording medium having excellent long-term reliability.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a microwave plasma CVD apparatus using a slotted annular waveguide used in the present invention.

FIG. 2 is a schematic sectional view showing an example of a conventional ECR plasma CVD apparatus.

[Description of Signs] 1 Film forming chamber 2 Plasma generating chamber 3 Base 4 Support 5 Exhaust pipe 6 First source gas inlet pipe 7 Second source gas inlet pipe 8 Third source gas inlet pipe 9 Microwave waveguide 10 Dielectric member 11 Electromagnet

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI // H01L 21/318 H01L 21/318 B

Claims (7)

[Claims] An evacuation means for depressurizing a plasma generation chamber and a film formation chamber communicating with the plasma generation chamber, and supplying a rare gas and a gas other than a rare gas to the plasma generation chamber or the film formation chamber; Supply microwave power to the generation chamber,
In a plasma CVD method for depositing a thin film on a substrate disposed in the film forming chamber, a value obtained by dividing the flow rate of the rare gas by the flow rate of a gas other than the rare gas is 4 or more and 7 or less, and A plasma CVD method, wherein the value of the energy density obtained by dividing the value by the flow rate of a gas other than the rare gas is 4500 J / cm ³ or more and 12000 J / cm ³ or less. 2. The plasma CVD method according to claim 1, wherein the pressure in the film forming chamber is 0.1 mtorr or more and 10 mtorr or less. 3. The plasma CVD method according to claim 1, wherein the microwave power is introduced by a slotted waveguide. 4. The method according to claim 1, wherein the thin film is a silicon nitride film, a silicon oxide film, a tantalum oxide film, a titanium oxide film, a titanium nitride film, an aluminum oxide film, an aluminum nitride film, or a magnesium fluoride film. The plasma CVD method according to any one of the above. 5. The plasma CVD according to claim 1, wherein the thin film is an amorphous silicon film, a polysilicon film, a silicon carbide film, or a gallium arsenide film.
Law. 6. The plasma CVD method according to claim 1, wherein the rare gas is helium, neon, argon, or xenon. 7. A method for manufacturing an optical recording medium having a protective film on a substrate, wherein the protective film is formed by the plasma CVD method according to claim 1. Method.