JPH02267272A - Thin film forming device - Google Patents

Abstract

PURPOSE:To efficiently apply a gaseous mixture utilized for film formation and to form a thin film at low cost by utilizing both an ungrounded electrode and a grounded electrode which are opposed with each other as the walls of the upper and lower surfaces of a film formation chamber in a plasma CVD method at the atmospheric pressure. CONSTITUTION:A film formation chamber 1 in a plasma CVD method at the atmospheric pressure is constituted of both the upper and lower surface parts which are made of an ungrounded electrode 2 and a grounded electrode 3 which are mutually opposed as a main body and the high resistors electrically insulating both electrodes 2, 3. A base plate A for a sample is placed on the grounded electrode 3 and a high-frequency power source 6 is connected to the ungrounded electrode. The distance (g) between the base plate 4 and the electrode 2 is regulated to 10-0.1mm and the ratio of the flow rate Q of the supplied gaseous mixture to the volume S of the discharge space is regulated to 1-10<2>sec<-1>. In this constitution, when the gaseous mixture wherein a gaseous raw material is diluted by large amounts of gaseous He is supplied to the discharge space through a feed port 5 and discharged through a discharge port 8 and film formation is performed, the gaseous mixture is effectively utilized and a uniform thin film is formed on the base plate A.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Technical field The present invention relates to the production of amorphous silicon (a-Si: amo
rphous 5ilicon) and titanium nitride (TiN
) and other thin film forming apparatuses.

For example, amorphous silicon a-S, which normally contains several at% to several tens of at% (atomic percent) of H in its film.
i# is seen as a promising material for low-cost solar cells. Other uses include image sensors, optical sensors, thin film transistors, and photosensitive materials for copying machines. Single crystal S
It has the advantage that it is cheaper than i and it is easier to obtain one with a large area.

Further, TiN is important as a surface protective film having wear resistance and the like.

As such thin film forming methods, thermal CVD method, plasma C
The VD method and the like are known.

Since the thermal CVD method requires heating the substrate, it can only be used with heat-resistant materials.

On the other hand, the plasma CVD method can form a thin film at a lower temperature than the thermal CVD method.

Therefore, thin films can be formed on low-cost glass substrates, polymer films, etc. with poor heat resistance, and they are widely used.

In the plasma CVD method, excitation energy is provided not in the form of heat but in the form of the kinetic energy of electrons and ions in the plasma, and the chemical energy of neutral radicals. Therefore, the temperature of the substrate can be lowered than in thermal CVD.

- As an example, amorphous silicon a-Si is 5pe
A thin film forming method using glow discharge was invented by AR.
Since it was possible to incorporate an appropriate amount of H into the film and reduce the defect density in the film, it became possible to create products that could withstand device applications such as solar cells and sensors.

W, B, 5pear, P, G, Lecom
ber:5olid Coswum, ILpH
93 (1975) This is a parallel plate type electrode with a frequency of 100 to 13.5 Hz.
An AC voltage of 6M11z is applied to cause glow discharge in a mixed gas such as SiL/L, SiH, -SiF4/Hs, etc. at a low pressure of 0.1 to 2↑orr.

Of course, dopants may also be added. This is PH
This is done by mixing gases such as , /It, , B2H, /H, etc.

(a) Prior Art Since the invention of 5pear, a-Si manufacturing equipment has been improved many times, but basically it performs glow discharge at low pressure.

Glow discharge does not occur unless the pressure is as low as 0.1 to 10 Torr. When the pressure is higher than this, the discharge shifts to a localized arc discharge, making it impossible to form a film on a substrate with poor heat resistance or to form a film uniformly over a large area. So such pressure is chosen.

Therefore, the container required an expensive vacuum chamber and had to be equipped with a vacuum pump.

In particular, in the case of photoelectric conversion materials such as solar cells using a-Si or the like, or surface protective films such as TiN, it is strongly required from a cost standpoint that a large area thin film can be formed all at once.

However, in the plasma CVD method, glow discharge is maintained to keep plasma stable. Glow discharge occurs in vacuum (0,1
~10 Torr).

Films can only be formed in a vacuum, so if you want to make a large-area film, you have to make the entire vacuum container larger.

A high-output vacuum pump is also required. In this case, the equipment becomes extremely expensive.

(1) Atmospheric pressure plasma CVD method Large-area film deposition and uniform processing are absolutely necessary to reduce costs, but if equipment costs increase, nothing will be achieved.

However, recently, plasma CVD under atmospheric pressure
An invention was made that made law possible.

For example, i JP-A No. 63-50478 (S, 63°3
．． 3 public).

The present inventors: (1) Japanese Patent Application No. 63-199647 (S, 63.8.
10 applications)■ Patent Application No. 199648 (S, 6
3.8.10 1m) iv Patent application 1986-19964
No. 9 (S, filed on August 10, 1983)■ Patent application 1986-2
No. 25355 (S, filed on September 8, 1989)
Patent Application No. 3-227121 (S, filed on 9/9/63) Patent Application No. 1983-230555 (S, filed on 9/14/63)
輯 Patent Application No. 1983-233130 (S, 63.9.
17 applications) and other inventions.

The second part shows the device indicated by ii, which does not have a high-resistance element between the electrodes.

Inside the film forming chamber 1, electrodes 2.3 facing each other are provided. One end is grounded and is called a ground electrode 3. The other electrode is referred to as the non-grounded electrode 2.

A sample substrate 4 is placed on the electrode 3. A gas inlet 5 and a gas outlet 8 are provided on the sides of the electrodes 2.3 so that gas is supplied to the space between the opposing electrodes. A mixed gas obtained by diluting a large amount of raw material gas with He gas is introduced through the nozzle 5, supplied to the discharge space, and exhausted to the outside of the film forming chamber 1 through the gas exhaust port 8. Here, with respect to the volume S of the discharge space, the flow rate Q of the mixed gas supplied to the discharge space is Q/S, which is 15 ec-'
The reason for setting it to 10'5 ec-' is to effectively perform gas replacement at the center of the plasma and to obtain uniform film formation over a large area.

Here, the distance g between the sample substrate 4 and the electrode 2 is 10 mm to 0
．． Make it 1ms+.

A high frequency power source 6 is connected to the non-grounded electrode 2 .

This can use, for example, a 13.56 MHz RF oscillator and an amplifier.

(1) Problems to be solved by the invention Thin film formation by plasma CVD under atmospheric pressure is an extremely promising method for cost reduction, but it requires effective gas replacement in the center of the plasma to ensure uniform film formation. In order to perform
c-'.

Therefore, in the conventional apparatus, there was a problem in that a large amount of He gas, which is the main component, of the mixed gas to be supplied was required.

Particularly when the distance g between the electrode 2 and the sample substrate 40 shown in FIG. 2 is small, there is a problem that the mixed gas supplied to the film forming chamber is not effectively supplied to the discharge space, making it difficult for the film itself to adhere.

(E) Purpose The purpose of the present invention is to save the amount of mixed gas used for film formation and to efficiently use it for film formation in a thin film formation method using plasma CVD under atmospheric pressure, which is promising for cost reduction. The purpose of the present invention is to provide an apparatus for forming thin films at a lower cost.

(Force) Structure of the Invention In the present invention, in order to save and efficiently utilize the amount of mixed gas used for film formation, mutually opposing electrodes used for plasma formation are arranged as walls facing the film forming chamber.

FIG. 1 shows a specific example of the present invention in which a non-grounded electrode 2 and a grounded electrode 3 constitute the upper and lower surfaces of a film forming chamber 1, respectively.

A film forming chamber 1 has a non-grounded electrode 2 and a grounded electrode 3 facing each other.
It is composed of an upper surface portion and a lower surface portion mainly composed of , and a high resistance body that electrically insulates the electrodes 2.3 facing each other.

A sample substrate 4 is placed on the electrode 3. A mixed gas obtained by diluting a large amount of raw material gas with He gas is introduced from a gas supply port 5 provided on the side of the film forming chamber 1, and is connected to two opposing electrodes 2.
．． 3 and is discharged to the outside of the film forming chamber 1 from a gas discharge port 8 provided on the side opposite to the gas supply port 50.

Here, with respect to the volume S of the discharge space, the flow rate Q of the mixed gas supplied to the discharge space is such that Q/S is 1 sec"" to 10'
The reason for setting it to 5 ec-' is to effectively perform gas replacement at the center of the plasma and to obtain uniform film formation over a large area.

Also, the distance g between the sample substrate 4 and the electrode 2 is 10IIlff
i~0.1mm.

A high frequency power source 6 is connected to the non-grounded electrode 2 .

This can use, for example, a 13.56 MHz RF oscillator and an amplifier.

As shown in FIG. 1, in the present invention, the electrode for plasma formation is used as the wall of the film forming chamber. Therefore, the mixed gas supplied to the film forming chamber effectively contributes to the discharge without going around to areas other than the discharge space, so the Q /
No extra mixed gas is required to maintain S=1 to 10'5ac-', and the amount of mixed gas can be saved.

This effect is particularly large when the distance g between the electrode 2 and the sample substrate 4 is small (it was difficult to perform gas replacement in the discharge space with conventional devices, but this method performs forced gas replacement). be able to.

Furthermore, since the electrodes form the outer wall of the film-forming chamber, the apparatus itself can be made very compact, and the apparatus cost can be reduced.

Example Using the apparatus shown in FIGS. 1 and 2, an a-Si film was formed by changing the distance g between the electrode 2 and the sample substrate 4 between the apparatus of the present invention and the conventional apparatus, At that time, the film formation speed was compared.

The film forming conditions are shown in Table 1, and the results are shown in Table 2.

Table 1 Film forming conditions Raw material gas flow rate 5 sccm He gas flow rate 2500 scca Substrate temperature 250°C Film forming pressure Atmospheric pressure Electrode area 40X 40as' RF frequency 13.56M7 RF power 30W Distance between electrode and substrate Mg 10am. 5a+a, law
Substrate quartz glass (4011*X 40m5
) In the apparatus of the present invention, all the mixed gas introduced into the gas supply port 5 can be supplied to the discharge space between the electrode 2 and the sample substrate 40, so the film formation speed is faster than in the conventional example, and the mixed gas can be used efficiently. can do.

The effect of the present invention is particularly great when g is small.

This is because in the conventional example, the mixed gas introduced from the gas supply port 5 is less likely to enter the discharge space than in the present invention.

Furthermore, it is clear that the apparatus of the present invention is more compact than the conventional apparatus, and the cost of the apparatus can be reduced.

(G) Effects of the Invention According to the apparatus of the present invention, in the atmospheric pressure plasma CVD method, which is expected to reduce equipment costs, the mixed gas used for film formation can be used efficiently, so thin films can be formed at lower costs. can be formed.

Furthermore, since the film forming apparatus itself can be made compact, costs can be further reduced.

It is particularly effective when used in the production of solar cells, TPT for thin film displays, etc., which require film formation over a wide area.

Note that the volume S of the discharge space is the product of the area of the electrode and the distance g between the electrode 2 and the sample substrate 4. In other words, S=A-g.

[Brief explanation of drawings]

FIG. 1 is an example of a schematic cross-sectional view of the thin film forming apparatus of the present invention. Figure 2 is a schematic cross-sectional view of an apparatus used in the thin film forming method disclosed in Japanese Patent Application No. 199647/1980, which has been modified based on the thin film forming method disclosed in Japanese Patent Application No. 63/230555. . 1...Film forming chamber 2...Non-grounded electrode 3...Grounded electrode 4...Sample substrate 5...Gas inlet 6...'f7 F power source 7... ...Heater 8...Gas exhaust port

Claims (1)

[Claims] (1) A sample substrate is installed on at least one of the opposing surfaces of two electrodes facing each other, and the distance between the sample substrate and the electrode facing the sample substrate or the distance between the sample substrate and the electrode facing the sample substrate is determined. The distance between the sample substrate and another sample substrate is 10 mm or less and 0.1 mm or more, and the film forming gas and H
Gas flow rate Q that supplies the mixed gas consisting of e to the discharge space
The value Q/S divided by the volume S of the discharge space is 1 to 10^2 s
ec^-^1 between the sample substrate and the electrode facing the sample substrate by supplying it to the discharge space on the sample substrate and applying a high-frequency voltage to the counter electrode under pressure near atmospheric pressure. Alternatively, in a thin film forming apparatus that forms a thin film on a sample substrate by causing glow discharge between a sample substrate and another sample substrate facing the sample substrate, the electrodes are used as opposing walls of a film forming chamber. A thin film forming apparatus characterized by: