JP2646582B2 - Plasma CVD equipment - Google Patents

Description

The present invention relates to a plasma CVD (Chemical Vapor Depositio).
The present invention relates to a method for forming a thin film by the method n).

2. Description of the Related Art In a plasma CVD method, a sample gas is excited by high-frequency energy while a sample is held in a vacuum chamber and a compound gas containing a composition element of a thin film to be formed is supplied to the sample surface. This is a method of forming a thin film on the sample surface by disposing the thin film on the sample surface. Since this method utilizes the activity of plasma, it is 400
It is characterized in that the film can be formed at a low temperature of about ° C.

The problems in forming a thin film by the plasma CVD method are the control of the film quality and the film thickness distribution of the formed thin film, and the problems of film defects such as pinholes and adhesion of particles. Another problem in production is improving the deposition rate.

Therefore, in order to uniformly form a high-quality plasma CVD film on the sample surface, it is necessary to devise the process conditions such as the distribution and stability of the low-temperature plasma when forming the thin film, the sample heating distribution, and the sample holding temperature.

The conventional plasma CV described above with reference to the drawings below.
An example of the D device will be described.

FIG. 2 shows a conventional plasma CVD apparatus. In FIG. 2, 1 is a vacuum vessel capable of maintaining a vacuum state, 2 is a sample on which a plasma CVD film is formed, 3 is a sample which holds a sample 2 and has a heater for heating inside, 4 is a heater mounted inside the sample table 3, 5 is an AC power supply for supplying AC power to the heater 4, and 6 is an electrode to which high frequency power of, for example, 400 KHz is supplied. ,
7 is a high-frequency power supply having a frequency of 400 KHz, 8 is a vacuum pump for evacuating the pressure in the vacuum vessel 1 to a degree of vacuum lower than the atmospheric pressure, 9 is a vacuum exhaust for hermetically connecting the vacuum vessel 1 and the vacuum pump 8. 10 is a butterfly valve for controlling the pressure in the vacuum vessel 1 by changing the resistance in the pipe, that is, by making the effective pumping speed of the vacuum pump 8 variable, and 11 is a vacuum vessel for controlling the compound gas through the gas flow control device. 1 is a gas nozzle to be introduced into the inside.

About the plasma CVD apparatus configured as described above,
The operation will be described below.

First, the inside of the vacuum vessel 1 is evacuated to a degree of vacuum of 50 mTorr or less by a vacuum pump 8, and then a compound gas containing a composition element of a thin film to be formed on the surface of the sample 2 is controlled from a gas nozzle 11 by a flow rate control device. Introduce into 1.
Further, the inside of the vacuum vessel 1 is controlled to a pressure which is a thin film forming condition, that is, 100 to 400 mTorr by operating the butterfly valve 10. The sample 2 is controlled to be heated to about 300 ° C. by the sample stage 3. Next, the compound gas is excited by supplying a high-frequency power having a frequency of 400 KHz to the electrode 6,
A plasma CVD film is formed on the surface of the sample 2 by exposing the surface of the sample 2 to the plasma atmosphere.

Problems to be Solved by the Invention However, the above configuration has the following problems.

That is, when plasma is generated, abnormal discharge is likely to occur in a portion of the gas nozzle 11 where gas is emitted, and as a result, a large number of spherical particles adhere to the surface of the sample 2.

In view of the above problems, the present invention provides a plasma CVD apparatus capable of preventing abnormal discharge from occurring in a gas introduction portion of a gas nozzle 11 at the time of plasma generation and preventing spherical particles from adhering to a sample surface. To provide.

Means for Solving the Problems In order to solve the above problems, the plasma CVD of the present invention
The apparatus is characterized in that a gas supply port for introducing a raw material gas into the reaction vessel is electrically insulated from the reaction vessel.

Effect The present invention can prevent the injection of electrons or ions into the gas blowout portion of the gas nozzle by electrically insulating the gas supply port and the reaction vessel, which are the configuration of the plasma CVD apparatus, by the above-described configuration. Therefore, it is possible to prevent discharge at the gas blowing portion. as a result,
Generation and adhesion of spherical particles to the sample surface can be prevented.

Embodiment Hereinafter, a plasma CVD apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view of a plasma CVD apparatus used in an embodiment of the present invention.

In FIG. 1, 31 is a vacuum vessel (reaction vessel) capable of maintaining a vacuum state, 32 is a sample as a workpiece on which a plasma CVD film is formed, 33 is a sample that holds the sample 32, and is heated inside. A sample stage as a means for holding a grounded work piece having an apparatus and capable of heating the sample 32, 34 is a sample stage
33 is a heating device mounted inside, 35 is an AC power supply, 36 is an electrode to which high-frequency power of a frequency of 400 KHz is supplied, 37 is a gas flow control device, 38 is a high-frequency power supply of a frequency of 400 KHz, and 39 is a vacuum vessel 31 A vacuum pump as a vacuum pumping means for reducing the pressure of the air to a degree of vacuum equal to or lower than the atmospheric pressure, a vacuum pumping pipe 40 for hermetically connecting the vacuum vessel 31 and the vacuum pump 39,
41 is a pressure control device for controlling the pressure in the vacuum vessel 31, 42 is a gas nozzle made of aluminum for introducing the source gas into the reaction vessel 31, and 43 is an insulator.

The operation of the plasma CVD apparatus configured as described above will be described.

First, the inside of the vacuum vessel 31 is evacuated to a vacuum of 30 mTorr or less by a vacuum pump 39, and then a compound gas containing a composition element of a thin film to be formed on the surface of the sample 32, that is, monosilane (SiH ₄ ), ammonia (NH ₃ ) And a mixed gas of nitrogen (N ₂ ) at a gas flow rate of 400 SCCM, 500 SCCM, and 1600 SCCM, respectively, through a gas flow control device 37 and a gas nozzle 42 through a vacuum vessel 31.
And the pressure in the vacuum vessel 31 is controlled by the pressure control device 41.
To keep it at 300 mTorr.

The sample 32 is controlled to be heated to a temperature of 300 ° C. by the sample stage 33.

Next, high-frequency power having a frequency of 400 KHz is supplied to the electrode 36 from the high-frequency power supply 38 to generate low-temperature plasma in the space including the sample 32.

As a result, a silicon nitride film having a refractive index of 1.997 ± 0.03 and a thickness variation of within ± 4% can be formed on the sample 32, and the number of particles having a particle diameter of 0.5 μm or more adhering on the sample 32 is 200 / It could be within 6 ″ wafer.

By the way, in order to clarify the effect of the present invention, the following experiment was performed. That is, when the gas nozzle 42 is electrically insulated from the reaction vessel 31, when the gas nozzle 42 is grounded, and when a DC voltage is supplied to the gas nozzle 42,
Visual results of abnormal discharge at the gas blowing hole of the gas nozzle 42, the number of particles of 0.5 μm or more adhering to the surface of the sample 32 measured by a laser surface inspection device, and the like were examined.

 Table 1 shows the experimental results.

As is evident from Table 1, only when the gas nozzle 42 is maintained at the float potential, no abnormal discharge is observed in the gas blowing portion, and the number of particles can be significantly suppressed as compared with the others.

FIG. 3 shows that the gas nozzle 42 is electrically insulated from the reaction vessel, a silicon nitride film is deposited about 8000 mm, and the surface is
Observed by SEM. No spherical particles are seen.

On the other hand, FIG. 4 is a view in which the gas nozzle 42 is grounded to ground, a silicon nitride film is deposited under the same process conditions, a silicon nitride film is deposited at about 8000 °, and the surface is observed by SEM. In this case, many particles having a particle size of 2 to 5 μm could be observed.

In addition, some particles are found to be buried in the silicon nitride film, and it is considered that the particles adhered during plasma CVD, that is, during generation of plasma, and formed the particle size. In other words, it is speculated that the abnormal discharge generated at the gas blowing portion of the gas nozzle 42 creates a nucleus that is a source of particles, increases its spherical shape by vapor phase growth, and adheres to the surface of the sample 32 during plasma CVD. .

As described above, according to the present embodiment, the gas nozzle 42 for introducing the raw material gas into the reaction vessel 31 is electrically insulated from the reaction vessel, thereby preventing the occurrence of abnormal discharge in the gas blowing portion. Plasma CV with very few film defects
D film can be obtained.

According to the present invention, a gas nozzle for introducing a source gas into the reaction vessel 31 is electrically insulated from the reaction vessel, thereby preventing an abnormal discharge from being generated in a gas blowing portion of the gas nozzle. As a result, a plasma CVD film with very few film defects can be obtained by preventing spherical particles from adhering to the sample surface during plasma CVD.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a plasma CVD apparatus in one embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a conventional plasma CVD apparatus, and FIG. 3 is a sample surface using a gas nozzle in one embodiment of the present invention. FIG. 4 is an electron micrograph showing a crystal structure when a silicon nitride film is formed on the sample, and FIG. 4 is an electron micrograph showing a crystal structure when a silicon nitride film is formed on the sample surface using a grounded gas nozzle. 31 ... Vacuum container, 33 ... Sample table, 34 ... Heating device, 35 ...
... AC power supply, 36 ... Electrode, 37 ... Gas flow control device, 38
…… High frequency power supply, 39 …… Vacuum pump, 40 …… Pipe, 41
…… Pressure control device, 42 …… Gas nozzle.

Claims (1)

(57) [Claims] 1. A metal reaction vessel capable of maintaining a vacuum state, a gas supply port for introducing a raw material gas into the reaction vessel, and an exhaust means for reducing the pressure inside the reaction vessel to a reduced pressure. A sample holding means for holding a sample for depositing a plasma CVD film on at least one surface, a heating means for thermally controlling the sample, and a pressure control means for holding the inside of the reaction vessel at a predetermined pressure, An electrode for generating low-temperature plasma at least in a space containing the sample; and a plasma generating means for supplying high-frequency power to the electrode to generate low-temperature plasma, wherein the gas supply port and the reaction vessel are electrically connected. Plasma CVD equipment with insulation.