JPH0797557B2 - Plasma CVD method - Google Patents

Description

TECHNICAL FIELD The present invention relates to plasma CVD (Chemical Vapor Deposition).
The present invention relates to a method for forming a thin film by a method.

2. Description of the Related Art The plasma CVD method holds a sample in a vacuum container, supplies a compound gas containing a composition element of a thin film to be formed, excites the compound gas by high-frequency energy, and causes the sample surface to be exposed to the plasma atmosphere. It is a method of forming a thin film on the surface of the sample by disposing the thin film on the sample surface. This method utilizes the activity of plasma, so
There is a feature that the film can be formed at a low temperature of up to about ° C.

The problem in forming a thin film by the plasma CVD method is the problem of film defects such as control of film quality and film thickness distribution of the formed thin film and adhesion of pinholes and particles. Also, the issue in terms of production is to improve the deposition rate.

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

An example of the above-described conventional plasma vapor deposition apparatus will be described below with reference to the drawings.

FIG. 3 shows a conventional plasma vapor deposition apparatus. In FIG. 3, 1 is a vacuum container capable of maintaining a vacuum state, 2 is a sample on which a plasma CVD film is formed, 3 holds sample 2,
Further, a sample table 5 having a heater 4 for heating inside and capable of heating the sample 2 is an AC power source for supplying an AC power to the heater 4, and 6 is a high frequency power of 50 kHz, for example. An electrode, 7 is a high frequency power source with a frequency of 50 kHz, 8 is a vacuum pump for evacuating the pressure in the vacuum container 1 to a vacuum degree of atmospheric pressure or less, 9 is an airtight connection between the vacuum container 1 and the vacuum pump A vacuum exhaust pipe, 10 is a butterfly valve for controlling the pressure inside the vacuum container 1 by varying the pipe resistance, that is, the effective pumping speed of the vacuum pump 8 is controlled, and 11 is a compound gas through a gas flow controller. The gas nozzle 12 for introducing the gas into the vacuum container 1 is a pressure gauge capable of measuring the pressure inside the vacuum container 1, and 13 is a pressure control device for giving a control signal to the butterfly valve 10 in accordance with the output of the pressure gauge 12.

The operation of the plasma vapor deposition apparatus configured as described above will be described below.

First, the inside of the vacuum container 1 is evacuated by the vacuum pump 8 to a vacuum degree of 50 mTorr or less, and then the compound gas containing the composition element of the thin film to be formed on the surface of the sample 2 is controlled from the gas nozzle 11 by the flow rate control device. Install within 1.

Further, the butterfly valve 10 is operated to control the inside of the vacuum container 1 to a pressure which is a thin film forming condition, that is, 100 to 400 mTorr. The sample 2 is heated and controlled to a temperature of about 300 ° C. by the sample table 3. Next, the compound gas is excited by supplying high frequency power having a frequency of 50 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.

By the way, when forming a plasma CVD film on the surface of the sample 2, a similar film (ineffective film) is deposited on the components inside the vacuum container 1, such as the electrode 6, the sample stage 3, and the vacuum container 1. That is, similar films accumulate on the components inside the vacuum container 1. This similar film has relatively weak adhesion, and as its thickness increases,
Flake is generated in the vacuum container 1. As a result, sample 2
A large amount of particles adhere to the surface, causing film defects in the plasma CVD film formed on the surface of the sample 2. Therefore, it is necessary to regularly remove the ineffective film attached to the components inside the vacuum container 1. Plasma cleaning is used as the means. This is a gas nozzle 11 inside the vacuum container 1.
After introducing more halogen gas and holding it at a predetermined pressure,
By supplying high-frequency power to the electrode 6, low temperature plasma is generated in the vacuum chamber 1 and the ineffective film is dry-etched by the active species in the low temperature plasma. For example, in the case of a plasma CVD apparatus that deposits a silicon nitride film on the surface of the sample 2, the halogen gas contains sulfur hexafluoride (SF ₆ ) or carbon tetrafluoride (CF ₄ ) and oxygen (O ₂ ). A mixed gas is used.

In addition, after plasma cleaning, in order to stabilize the film deposition rate, film quality, etc., film deposition is performed on the components inside the vacuum container 1 in advance in the state where the sample 2 is not inserted before the film deposition on the normal sample 2 (hereinafter This operation is called predeposition.)

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

That is, since the plasma cleaning is managed and controlled by the generation time of the low temperature plasma, it is difficult to perform the plasma cleaning with good reproducibility. Therefore,
Insufficient plasma cleaning causes film defects in the plasma CVD film. In addition, since the plasma cleaning state cannot be detected, the predeposition condition cannot be set clearly.

In view of the above problems, the present invention provides a plasma CVD method capable of reproducibly plasma cleaning an ineffective film attached to a component inside a vacuum container of a plasma CVD apparatus.

Means for Solving the Problems In order to solve the above problems, the plasma CVD method of the present invention uses the output of the pressure control means when plasma cleaning the components inside the reaction vessel of the plasma CVD apparatus in the reaction vessel. The feature is that plasma cleaning is performed while monitoring.

Effect The present invention can perform plasma cleaning with good reproducibility by the above configuration. That is, in plasma cleaning, the film attached to the components inside the vacuum container is
Since it reacts with the halogen gas in the plasma state and is etched into a gas, the number of gas particles increases during the etching. That is, the pressure becomes higher during the etching than when the halogen gas is in the plasma state. Actually, the change in pressure is immediately sent to the pressure control device by the pressure gauge and fed back to the opening and closing of the butterfly valve, so the pressure remains constant,
By monitoring the signal from the pressure control device controlling the butterfly valve to the butterfly valve, the end point of etching can be detected, and the plasma cleaning can be appropriately controlled based on this.

Example First, an example of a plasma CVD apparatus used in the method of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view of the plasma vapor phase growth apparatus.

In FIG. 1, 41 is a vacuum container capable of maintaining a vacuum state, 42 is a sample as a workpiece on which a plasma CVD film is formed, 43 holds the sample 42, and has a heating device 44 inside. A sample stand as a grounded workpiece holding means capable of heating the sample 42, 45 is an AC power supply, 46 is an electrode to which high frequency power having a frequency of 50 kHz is supplied, 47 is a nozzle, and 48 is a frequency of 50 kHz. Of the high frequency power source, 49 is a vacuum pump as a vacuum exhaust means for making the pressure in the vacuum container 41 to be a degree of vacuum equal to or lower than atmospheric pressure, and 50 is a vacuum exhaust for airtightly connecting the vacuum container 41 and the vacuum pump 49. Vibrate, 51 is a butterfly valve for controlling the pressure inside the vacuum container 41, 52 is a pressure gauge that can measure the pressure inside the vacuum container 41, and 53 is a pressure gauge.
A pressure control device that gives a control signal to the butterfly valve 51 according to the output of 52, and a voltmeter 54 that reads the control signal of the pressure control device 53.

A plasma CVD method using the plasma CVD apparatus configured as above will be described.

First, the inside of the vacuum container 41 is set to 30 mTorr by the vacuum pump 49.
After evacuation to the following vacuum degree, a compound gas containing the composition elements of the thin film to be formed on the surface of the sample 42, that is, a mixed gas of monosilane (SiH ₄ ), ammonia (NH ₃ ), and nitrogen (N ₂ ) is At a gas flow rate of 13 SCCM, 31 SCCM, 142 SCCM, the gas is introduced into the vacuum container 41 from the nozzle 47, and the pressure in the vacuum container 41 is maintained at 260 mTorr by operating the pressure control device 53.

The sample 42 is controlled to be heated to a temperature of 300 ° C. by the sample table 43. Next, a frequency of 50kH is applied to the electrode 46 from a high frequency power source 48.
By supplying high frequency power of z, low temperature plasma is generated in the space containing the sample 42. As a result, sample 42
A silicon nitride film having a refractive index of 1.998 ± 0.02 and a thin film distribution of ± 3% could be formed on top.

Next, the operation when performing plasma cleaning will be described.

First, the sample 42 is taken out of the vacuum container 41, and then the vacuum container 41 is evacuated to a vacuum degree of 30 mTorr or less by a vacuum pump 49, and then sulfur hexafluoride (S ₆ ) gas is added to 200 SCC.
At a gas flow rate of M, introduced into the vacuum container 41 from the nozzle 47,
In addition, the pressure inside the vacuum container 41 is maintained at 300 mTorr by operating the pressure control device 53. Next, a high frequency power source 48 is applied to the electrode 46.
A low-temperature plasma is generated by supplying high-frequency power with a frequency of 50 kHz.

During plasma cleaning, the voltmeter 54 measures the control signal of the pressure control device 53. The measurement results are shown in FIG. As is clear from FIG. 2, the control signal increases at the same time when the plasma cleaning is started and gradually decreases after a certain period of time. A certain value of the control signal is determined, and when it reaches that value, the supply of high frequency power is stopped and the plasma cleaning is terminated.

Next, after plasma cleaning, pre-deposition was performed with a film thickness of about 1 μm under a constant condition, and then the film deposition rate of the silicon nitride film was examined, and it was confirmed that reproducibility was good. That is, it indicates that the plasma cleaning was performed with good reproducibility.

As described above, according to the present embodiment, during the plasma cleaning, when the control signal of the pressure control device reaches a certain value,
The plasma cleaning can be performed with good reproducibility by stopping the supply of the high frequency power and ending the plasma cleaning.

As described above, the present invention, in the plasma CVD method, when performing plasma cleaning in vacuum chamber components of the plasma CVD apparatus in the vacuum vessel, by performing plasma cleaning while monitoring the output of the pressure control device, Plasma cleaning can be performed with good reproducibility.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example of a plasma CVD apparatus used for carrying out the method of the present invention, FIG. 2 is a graph showing a time change of a control signal of a pressure control apparatus during plasma cleaning, and FIG. 3 is a conventional plasma CVD apparatus. FIG. 41 …… Vacuum container, 42 …… Sample, 43 …… Sample stand, 44 …… Heating device, 45 …… AC power supply, 46 …… Electrode, 47 …… Nozzle,
48 …… high frequency power supply, 49 …… vacuum pump, 50 …… pipe,
51 …… Butterfly valve, 52 …… Pressure gauge, 53 …… Pressure control device, 54 …… Voltmeter.

Claims (2)

[Claims] 1. A vacuum vessel capable of maintaining a vacuum state, an evacuation means for reducing the pressure inside the vacuum vessel, and a plasma.
Sample holding means for holding a sample for depositing a CVD film on at least one surface, heating means for heating and controlling the sample, gas supply means for introducing a raw material gas into the vacuum container, and Plasma CVD comprising pressure control means for maintaining a predetermined pressure, electrodes for generating low temperature plasma in a space containing at least a sample, and plasma generation means for supplying high frequency power to the electrodes to generate low temperature plasma In the plasma CVD method using the device,
A plasma CVD method for performing plasma cleaning of components inside a vacuum container of a plasma CVD device in a reaction container while monitoring output of a pressure control means. 2. A method of performing plasma cleaning while monitoring the output of the pressure control means when plasma-cleaning the components in the vacuum vessel of the plasma CVD apparatus in the reaction vessel, the output of the pressure control means is set to a predetermined value. The plasma CVD according to claim 1, wherein a method of terminating the plasma cleaning when it reaches
Method.