JPH08209349A - Plasma cvd device - Google Patents

Abstract

PURPOSE: To improve the working rate of a plasma CVD device by eliminating the need for the replacement and cleaning of a reacting gas shower plate constituting a part of an upper electrode in the plasma CVD device. CONSTITUTION: This plasma CVD device has vertically opposed electrodes 3 and 4, a reacting gas is supplied, a high-frequency power is impressed on the electrodes to produce plasma, and a thin film is formed on a substrate 13 to be treated. The upper electrode is hollowed, is provided with a shower plate 15 on the lower face of the upper electrode, the shower plate is a porous metallic plate, and the reacting gas introduced into the hollow part 8 of the upper electrode is supplied through the shower plate. The reacting gas is uniformly supplied on the entire surface of the shower plate from the micropore of the porous metallic plate, the gas is never stagnated on the lower face of the upper electrode, homogeneous plasma produced, and further, a film is not deposited on the upper electrode due to self-purification effect of the reacting gas flow. Consequently, homogenous plasma is produced, and a homogeneous thin film is formed on the substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma CVD apparatus for producing a semiconductor element by forming a thin film on a silicon wafer or a glass substrate.

[0002]

2. Description of the Related Art FIG. 3 schematically shows a single-wafer plasma CVD apparatus, in which a cathode electrode 3 is provided on the ceiling side of a vacuum container 1 with an insulator 2 interposed therebetween, and a cathode is provided on the lower surface of the cathode electrode 3. A shower plate 7 forming a part of the electrode 3 is provided. A hollow portion 8 is formed inside the cathode electrode 3, and a reaction gas introducing passage 9 communicates with the hollow portion 8.
As shown in FIG. 3, a large number of dispersion holes 10 are formed in the shower plate 7.

The cathode electrode 3 is provided on the bottom side of the vacuum container 1.
A susceptor 4 also serving as an anode electrode facing the susceptor 4 is provided, the susceptor 4 is provided on a base plate 5, and a heater 6 is embedded in the base plate 5.

A high frequency power source 11 is connected between the cathode electrode 3 and the susceptor 4 via a base plate 5 and the like, and an exhaust pipe 12 is provided at the bottom of the vacuum container 1.

The substrate 13 to be processed is placed on the susceptor 4, exhausted from the exhaust pipe 12, the inside of the vacuum container 1 is evacuated, and then the reaction gas is introduced from the reaction gas introduction passage 9. The reaction gas passes through the hollow portion 8 and the dispersion holes 10 of the shower plate 7
It is more dispersed and flows into the vacuum container 1. A high frequency power is applied to the cathode electrode 3 and the susceptor 4 to ionize the reaction gas to generate plasma between the cathode electrode 3 and the susceptor 4, and the plasma is used to form a thin film on the substrate 13 to be processed. To do.

[0006]

FIG. 4 is an enlarged view of the dispersion hole 10 portion of the shower plate 7 in the above plasma CVD apparatus.
As shown in the above, the distance L between the dispersion holes 10 is large with respect to the diameter of the dispersion holes 10, that is, the flux of the reaction gas, and a stagnation 14 is generated between the dispersion holes 10. The stagnation portion 14 has no self-cleaning action due to the flow of the reaction gas, and the reaction gas in the stagnation portion 14 contacts the plasma to deposit a film on the shower plate 7.

When a film is deposited on the shower plate 7, the deposited film changes the electrode surface potential, which causes a change in plasma intensity and impairs reproducibility of film formation. Furthermore, when the deposited film peels off, it becomes particles and contaminates the substrate 13 to be processed.
It may cause product defects. Therefore, the shower plate 7 must be removed and replaced with a clean shower plate 7 before the deposited film is peeled off, or the shower plate 7 must be cleaned by a means such as dry cleaning.

Plasma CV is used for cleaning the shower plate 7.
Device D must be shut down, which is why plasma CV
The operation rate of the D device is lowered, and the throughput is lowered. Further, in the case of a hot cathode electrode that heats the cathode electrode 3, the operation time is further reduced due to the step of cooling the cathode electrode 3 in order to replace the electrode. Furthermore, the conventional shower plate 7 described above has a problem that it is difficult to uniformly introduce a reaction gas in a large area, and it is difficult to cope with a large-sized substrate accompanying the recent increase in the size of LCD.

In view of the above situation, the present invention is to provide a plasma CVD apparatus which does not require a shower plate replacement and a shower plate dry cleaning.

[0010]

The present invention has upper and lower electrodes facing each other and supplies a reaction gas to apply high frequency power to the upper and lower electrodes to generate plasma to form a thin film on the surface of a substrate to be processed. In the plasma CVD apparatus to be produced, the upper electrode is hollow, the lower electrode is provided with a shower plate on the lower surface, the shower plate is a porous metal plate, and the reaction gas is introduced into the hollow portion of the upper electrode. It is characterized in that the reaction gas is supplied through the shower plate.

[0011]

The reaction gas is uniformly supplied from the fine holes of the porous metal plate over the entire surface of the shower plate, and the gas does not accumulate on the lower surface of the upper electrode. Therefore, a uniform plasma is generated, and further, a film is not deposited on the upper electrode due to the self-cleaning action of the reaction gas flow, a uniform thin film can be generated on the substrate to be processed, and the plasma CVD apparatus required for cleaning the upper electrode is stopped. Is avoided and the operating rate is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the same parts as those shown in FIG. 3 are designated by the same reference numerals.

A cathode electrode 3 is provided on the ceiling side of the vacuum container 1 via an insulator 2, and a shower plate 15 forming a part of the cathode electrode 3 is provided on the lower surface of the cathode electrode 3. A reaction gas introducing passage 9 is communicated with the hollow portion 8 of the cathode electrode 3. As shown in FIG. 2, the shower plate 15 is made of a porous material formed by sintering stainless particles.

A susceptor 4 also serving as an anode electrode facing the cathode electrode 3 is provided on the bottom surface side of the vacuum container 1. The susceptor 4 is provided on a base plate 5, and a heater 6 is mounted on the base plate 5. It is buried. A base plate 5 is provided between the cathode electrode 3 and the susceptor 4.
A high-frequency power source 11 is connected via the, and an exhaust pipe 12 is provided at the bottom of the vacuum container 1.

The heater 6 allows the required temperature (250 to
The substrate 1 to be processed is placed on the susceptor 4 heated to 350 ° C.
3 is placed, the exhaust pipe 12 is evacuated, the inside of the vacuum container 1 is evacuated, and then the reaction gas is introduced through the reaction gas introduction passage 9. The reaction gas uniformly flows into the vacuum container 1 through the hollow portion 8 through the entire pores of the shower plate 15. After supplying the reaction gas, the inside of the vacuum chamber 1 is maintained at 0.2 to 0.5 Torr to apply high-frequency power to the cathode electrode 3 and the susceptor 4 to generate plasma between the cathode electrode 3 and the susceptor 4 and generate the plasma. A thin film (amorphous silicon film) is formed on the substrate to be processed 13 by utilizing the above.

The shower plate 15 is an aggregate of fine holes, and pores are dispersed over the entire surface of the shower plate 15. Since the pores are very close to each other, the entire surface of the shower plate 15 is small. There is a self-cleaning action by the gas flow of the reaction gas over, and the retention of the reaction gas on the lower surface of the shower plate 15 is suppressed.

Thus, a gas having a uniform gas concentration can be easily obtained, and in the case of transport-controlled as in plasma CVD, a highly uniform film can be formed in-plane.

Here, the shower plate 15 is set to 500 μm.
When sintered with the following particles, the formed amorphous silicon film has a film thickness uniformity of ± 3% or less, and the shower plate 15 is hardly soiled.

Next, as another example of film formation, film formation of silicon nitride will be described.

A mixed gas of monosilane SiH ₄ and ammonia NH ₃ is used as a reaction gas, and after the supply, the pressure is 0.2 to
A silicon nitride film can be formed on the glass substrate 2 by setting 1.2 Torr and applying high frequency power. In this case, the silicon nitride film has a film thickness uniformity of ± 3%.
Within the range, the shower plate 15 is hardly soiled.

In addition to stainless particles, nickel particles and the like can be used as the sintering material. Further, as the porous plate, fine mesh nets may be laminated in a multilayer and integrated. Further, although the above-mentioned embodiment has explained the glass substrate, it goes without saying that the same can be applied to the case of forming a thin film on a wafer.

[0023]

As described above, according to the present invention, it is not necessary to replace or clean the cathode electrode, or the frequency thereof is significantly reduced, so that the operating rate of the plasma CVD apparatus is improved and high throughput can be realized. Moreover, the film thickness uniformity can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a partially enlarged view of the shower plate according to the embodiment.

FIG. 3 is a cross-sectional view showing a conventional example.

FIG. 4 is a partially enlarged view of the conventional shower plate.

[Explanation of symbols]

 1 Vacuum container 3 Cathode electrode 4 Shower plate 8 Hollow part 11 High frequency power supply 15 Shower plate

Claims (2)

[Claims] 1. A plasma CVD apparatus having upper and lower electrodes facing each other and applying a high-frequency power to the upper and lower electrodes while supplying a reaction gas to generate plasma to form a thin film on the surface of a substrate to be processed. The upper electrode is hollow, the upper electrode is provided with a shower plate on the lower surface, the shower plate is a porous metal plate, and the reaction gas introduced into the hollow portion of the upper electrode is supplied to the shower plate. A plasma CVD apparatus characterized by being configured to be supplied via. 2. The plasma CVD apparatus according to claim 1, wherein the porous metal plate is obtained by sintering stainless particles.