JPS6314422A - Plasma chemical vapor desposition method - Google Patents

Abstract

PURPOSE:To perform a plasma cleaning on the ineffective film adhered to the component parts located in a vacuum chamber of a plasma CVD device in an excellent reproducible manner by a method wherein a plasma cleaning operation is performed while the self-biased voltage of the electrode, with which low temperature plasma is generated in the vacuum chamber, is being monitored. CONSTITUTION:When a plasma cleaning is performed on the component parts in the reaction chamber 41 of a plasma CVD device, the plasma cleaning is performed while the self-biased voltage of the electrode 46, with which low- temperature plasma is generated, is being monitored. For example, a silicon nitride film is formed on the surface of a sample 42 using the plasma CVD device, and after the sample 42 has been picked out from the vacuum chamber 41, the vacuum chamber 41 is evacuated, SF6 gas is introduced from a gas flow-rate controlling device 47, and low temperature plasma is generated. Also, while the plasma cleaning is being performed, the self-biased voltage of the electrode 46 is measured by a voltmeter 53 through the intermediary of a filter 52. Then, when the self-biased voltage dropped to the prescribed value, the supply of high frequency power is stopped, and the plasma cleaning operation is finished.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention applies to PRADA? CV D (Chemi ca
The present invention relates to a method for forming a thin film 6 by a vapor deposition method.

In the conventional plasma CVD method, a sample is held in a vacuum container, and while a compound gas containing the constituent elements of the thin film to be formed is supplied, the compound gas is excited and energized by high-frequency energy.
This method forms a thin film on the sample surface by placing the sample surface in the plasma atmosphere. This method utilizes plasma activity, so it is possible to
It has the characteristic that film formation can be performed at a low temperature of about 0°C.

Issues in forming thin films by plasma CVD include control of the quality and thickness distribution of the formed thin film, and problems with film defects such as pinholes and particle adhesion. Another issue in terms of 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 process conditions such as the distribution and stability of low-temperature plasma during thin film formation, sample heating distribution, and sample holding temperature.

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

FIG. 3 shows a conventional plasma vapor phase growth apparatus.

In FIG. 3, 1 is a vacuum container that can maintain a vacuum state, 2 is a sample on which a plasma CVD film is formed, and 3 is a sample 2.
and has an internal heater for heating sample 2.
4 is a heater mounted inside the sample stage 3, 6 is an AC power source for supplying AC power to the heater 4, and 6 is an electrode to which high frequency power of, for example, 50 KHz is supplied. , 7 is a high-frequency power supply with a frequency of 60 KHz, 8 is a vacuum pump for evacuating the pressure inside the vacuum container 1 to a degree of vacuum below atmospheric pressure, and 9 is a vacuum for airtightly connecting the vacuum container 1 and the vacuum pump 8. Exhaust pipe, 1o
11 is a butterfly valve that controls the pressure inside the vacuum vessel 1 by making the resistance inside the tube variable, that is, the effective pumping speed of the vacuum pump 8; and 11 is a gas flow rate controller that introduces compound gas into the vacuum vessel 1. This is a gas nozzle for.

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 pumped with the vacuum pump 8 to 60mTor.
After evacuation to a vacuum level below
1 into the vacuum container 1 while being controlled by a flow rate controller.

Furthermore, the butterfly valve 1o is operated to control the inside of the vacuum vessel 1 to a pressure of 100 to 400 mTorτ, which is the thin film forming condition. In addition, the sample 2 is placed at SOO by the sample stage 3.
Heating is controlled to a temperature of about 1000 ft.
A plasma CVD film is formed on the surface of the sample 2 by exciting the compound gas by supplying high frequency power of 0 KHz and 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, the electrode 6, the sample stage 3, the vacuum vessel 1, etc.
A similar film (ineffective film) is also deposited on internal components. That is, similar armpits accumulate in the components inside the vacuum container 1. This similar film has relatively weak adhesion, and as the film thickness increases, flakes are generated within the vacuum vessel 1. As a result, a large amount of particles adhere to the surface of the sample 2, causing film defects in the plasma CVD film formed on the surface of the sample 2.

Therefore, it is necessary to periodically remove the ineffective film adhering to the components inside the vacuum vessel 1. Plasma cleaning is used as a means for this purpose. This involves introducing halogen gas into the vacuum chamber 1 through the gas nozzle 11, maintaining it at a predetermined pressure, and then supplying high-frequency power to the electrode 6 to generate low-temperature plasma within the vacuum chamber 1. The activated species of this method dry-etch the ineffective film. 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 may be sulfur hexafluoride (SF6) or a mixed gas of carbon tetrafluoride (CF4) and oxygen (O2). used.

In addition, in order to stabilize the film deposition rate and film quality after plasma cleaning, before depositing the film on the sample 2, the film is usually deposited on the components inside the vacuum vessel 1 without the sample 2 (hereinafter referred to as This operation is called pre-deposition.)

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

That is, since plasma cleaning is managed and controlled by the generation time of low-temperature plasma, it is difficult to perform plasma cleaning with good reproducibility. Therefore, if plasma cleaning is insufficient, plasma CV
D causes film defects in the film. Furthermore, since the plasma cleaning state cannot be detected, there is a problem in that predeposition conditions cannot be clearly set.

In view of the above-mentioned problems, the present invention provides a plasma CVD method capable of plasma cleaning an ineffective film attached to a component inside a vacuum chamber of a plasma CVD apparatus with good reproducibility.

Means for Solving the Problems In order to solve the above problems, the plasma CVD of the present invention
The method involves plasma cleaning the internal components of a reaction vessel of a plasma CVD apparatus by applying high frequency power and monitoring the self-bias voltage of an electrode that generates low-temperature plasma within the vacuum vessel. It's a method.

Effect of the Invention With the above-described configuration, the present invention allows plasma cleaning to be performed while monitoring the self-bias voltage of the electrode when performing plasma cleaning of the internal components of the reaction vessel of a plasma CVD apparatus within the reaction vessel. Plasma cleaning can be performed with good reproducibility by stopping the supply of high frequency power and terminating plasma cleaning when the amount increases to .

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

FIG. 1 shows a schematic cross-sectional view of a plasma vapor phase growth apparatus used in an embodiment of the present invention.

In FIG. 1, 41 is a vacuum container (reaction container) that can maintain a vacuum state, 42 is a sample as a workpiece on which a plasma CVD film is formed, and 43 is a container that holds sample 42 and heats the inside. a sample stand as a grounded workpiece holding means that has a device and is capable of heating the sample 42;
44 is a heating device mounted inside the sample stage 43, 46 is an AC power source, 46 is an electrode to which high frequency power with a frequency of 60 KHz is supplied, 47 is a gas flow rate control device, and 48 is a frequency 5
0 KHz high frequency power supply; 49, a vacuum pump as evacuation means for reducing the pressure inside the vacuum container 41 to a degree of vacuum below atmospheric pressure; 60, an airtight connection between the vacuum container 41 and the vacuum pump 49; A pipe for evacuation, 61 is a pressure control device for controlling the pressure inside the vacuum container 41, 62
is a filter for removing high frequency components, and 63 is a voltmeter.

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

First, the vacuum pump 49 pumps the inside of the vacuum container 41 for 30 minutes.
After evacuation to a vacuum level of mTorr or less, sample 42
Compound gas containing the constituent elements of the thin film to be formed on the surface, i.e., monosilane (S I H4) t ammonia (
NH3) and nitrogen (N2) mixed gas at 13 SCCM each.
, 31 SCCM, and 142 SCCM are introduced into the vacuum vessel 41 from the gas flow rate controller 47,
In addition, the pressure inside the vacuum container 41 is maintained at 260 mTorr by operating the pressure control device 61.

Further, the sample 42 is heated and controlled to a temperature of 300° C. by the sample stage 43. Next, by supplying high frequency power with a frequency of 50 KHz to the electrode 46 from the high frequency power supply 48, low temperature plasma is generated in the space containing the sample 42. As a result, the refractive index is 1.998±0.02 on the sample 42,
A silicon nitride film with a film thickness distribution of ±3 inches could be formed.

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

First, after taking out the sample 42 from inside the vacuum container 41, the inside of the vacuum container 41 is heated to 30 mTor by the vacuum pump 49.
After evacuation to a vacuum degree of r or less, sulfur hexafluoride (S
F6) Gas is introduced into the vacuum container 41 from the gas flow rate controller 47 at a gas flow rate of 200 SCCM, and the pressure inside the vacuum container 41 is controlled to 300 SCCM by operating the pressure controller 61.
Hold at m Torr. Next, low-temperature plasma is generated by supplying high-frequency power with a frequency of 50 KHz from the high-frequency power source 48 to the electrode 46 .

Still during plasma cleaning, the self-bias voltage of the electrode 46 is measured with a voltmeter 63 via a filter 52.

The measurement results are shown in FIG. Point A in FIG. 2 shows the self-bias voltage when low temperature plasma is generated. As is clear from FIG. 2, as plasma cleaning progresses, the self-bias voltage decreases over a certain period of time. A certain value after this increase is determined, and when that value is reached (-141V in this example), the supply of high frequency power is stopped,
Finish plasma cleaning.

After plasma cleaning and pre-deposition with a film thickness of approximately 1 μm under certain conditions, we investigated the film deposition rate of the silicon nitride film and found that it was almost the same as shown in Table 1. The value was obtained (6 experiments were conducted from Tomi 1 to Hibi 6). In other words, this shows that plasma cleaning was performed with good reproducibility.

Table 1 As described above, according to this embodiment, during plasma cleaning, high-frequency power is applied, and the self-bias voltage of the electrode 46 that generates low-temperature plasma in the vacuum container 41 is monitored with the voltmeter 63, When the value decreased to a predetermined value, the supply of high frequency power was stopped and plasma cleaning was completed, thereby making it possible to perform plasma cleaning with good reproducibility.

Effects of the Invention According to the present invention, when performing plasma cleaning of the internal components of a reaction vessel of a plasma CVD apparatus in the reaction vessel, high frequency power is applied and the self-bias voltage of the electrode that generates low-temperature plasma in the vacuum vessel is monitored. Plasma cleaning can be performed with high reproducibility by, for example, being able to stop plasma cleaning when the self-bias voltage decreases to a predetermined value.

[Brief explanation of drawings]

Fig. 1 is a schematic cross-sectional view of a plasma CVD apparatus according to an embodiment of the present invention, Fig. 2 is a view monitoring the self-bias voltage of an electrode during plasma cleaning, and Fig. 3 is a schematic cross-sectional view of a conventional plasma CVD apparatus. be. 41... Vacuum container, 42... Sample, 4
3... Sample stand, 44... Heating device, 4
6... AC power supply, 46 electrodes, 47...
Gas flow rate control device, 48...High frequency power supply, 49
...Vacuum pump, 6o...Pipe, 6
1...Pressure control device, 62...Filter, 63...Voltmeter.

Claims (2)

[Claims] (1) A reaction vessel capable of maintaining a vacuum state, an exhaust means for creating a reduced pressure atmosphere inside the reaction vessel, and plasma CVD
A sample holding means for holding a sample on which a film is to be deposited on at least one surface, a heating means for controlling heating of the sample, a gas supply means for introducing raw material gas into the reaction vessel, and a sample holding means for holding a sample on which a film is to be deposited on at least one surface; A plasma CVD apparatus comprising: a pressure control means for maintaining the pressure at a pressure of A plasma CVD method using a plasma CVD method in which plasma cleaning is performed while monitoring the self-bias voltage of an electrode when plasma cleaning components inside a reaction vessel of a plasma CVD apparatus in the reaction vessel. (2) When the internal components of the reaction vessel of the plasma CVD apparatus are plasma cleaned in the reaction vessel, the plasma cleaning is terminated when the self-bias voltage of the electrode decreases to a predetermined value. Plasma CVD method.