JPS61170573A - Photo cvd device - Google Patents

Abstract

PURPOSE:To prevent the sticking of alpha-Si to a window for transmission of high energy light for cracking gaseous raw materials and to form an alpha-Si film on a base at a specified speed by cooling said window in the stage of decomposing the raw materials by the light energy and depositing the amorphous Si(alpha-Si) on the base by a photo CVD method. CONSTITUTION:The base 3 to be treated is placed in a reaction vessel 1 of a photo CVD device and is heated to 50-150 deg.C by a heater 4. The inside of the vessel 1 is evacuated to a reduced pressure by an evacuation pipe 12 and thereafter a gaseous hydrogenated silicon compd. such as SiH4 or Si2H6 is mixed with a carrier gas, gaseous halogen, etc., in a gas 10 from cylinder 6-9 and is supplied into the vessel 1. High energy light 15 from a mercury lamp, etc. 14 is at the same time irradiated through the window 16 for transmission of light excite and decompose the gaseous hydrogenated silicon compd. by which the amorphous Si film is formed on the base 3. The window 16 is cooled with water or other refrigerant to prevent the sticking of the alpha-Si by which the decrease in the forming speed of the alpha-Si film owing to a decrease in the transmission quantity of the high energy light 18 is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a photo-CVD apparatus, and in particular, a means for increasing the formation rate of a deposited film and making it possible to form a deposited film with uniformity and reproducibility. The present invention relates to an optical CVD apparatus equipped with the following.

[Conventional technology]

In recent years, amorphous silicon (hereinafter abbreviated as a-Si) RRTI has come to be used for various purposes, such as optical sensors, solar cells, electrophotographic photoreceptors, etc. using a-9il151. is widely used as it has good performance. As a method for manufacturing an a-Si film, a method using, for example, SiH4 or Si'21(6) as a raw material by a glow discharge method or a thermal energy deposition method is known.

However, in the glow discharge deposition method, under high power, the influence of discharge energy on the a-9i film being deposited is large;
It becomes difficult to control reproducible and stable conditions. This is particularly noticeable when forming a thick deposited film over a wide area.

In addition, the thermal energy deposition method requires high temperatures, which limits the types of supports that can be used, and increases the probability that useful bonded hydrogen atoms in a-Sill will be desorbed due to high temperatures. It is difficult to obtain a deposited film with specific characteristics.

In this way, when forming a deposited film using glow discharge deposition or thermal energy deposition, it is difficult to ensure uniform electrical and optical properties and quality stability, and furthermore, the film surface is disturbed during deposition. At present, there still remain problems such as the tendency for defects to occur in the deposited film.

Therefore, in recent years, in order to solve these problems, a method of depositing an a-Si deposited film using light energy (photo-CVD method) has been proposed and is attracting attention. According to this photo-CVD method, the overfilling problem can be significantly improved due to the advantage that the a-Si deposited film can be produced at a low temperature and by an ion-free reaction.

[Problem that the invention seeks to solve]

However, in the photoCVD method, a-S
A new problem arises in that an i-deposited film is formed, which significantly reduces the transmittance of incident light into the reaction vessel and reduces the rate of formation of the deposited film on the support.

In order to avoid this difficulty, a method of applying vacuum pump oil to the inner surface of the light-transmitting window has generally been adopted. However, bringing organic substances such as oil into the reaction vessel leads to the introduction of impurities such as oil molecules into the deposited film that is formed, impairing the high quality of the film that is a feature of the photoCVD method. There was a problem that

The present inventors investigated the deposition of the a-9i film on the light transmitting window and found that the increase in temperature of the light transmitting window was involved. FIG. 4 is a graph showing the results of an investigation regarding the temperature rise of the light transmitting window when a low pressure mercury lamp is irradiated onto the light transmitting window made of synthetic quartz having a thickness of 15 cm. In this way, even when synthetic quartz that transmits ultraviolet rays is used as the light-transmitting plate of the light-transmitting window, a portion of the light energy is converted into thermal energy, and the temperature of the light-transmitting window increases.

Therefore, the raw material gas near the window, for example, 5iHa or 5i
The absorption wavelength of 286 is shifted to longer wavelengths, and a deposition reaction or adhesion to the light transmission window occurs, similar to the deposition of the a-Si film on the support.

The present invention was made to solve the above-mentioned problems in the photo-CVD method.The purpose of the present invention is to maintain a constant film deposition rate on the support by preventing deposition on the light-transmitting window. An object of the present invention is to provide a photo-CVD apparatus that can produce a high-quality silicon film while maintaining The reactor is equipped with a means for introducing a raw material gas into a container, and a means for irradiating the raw material gas with high-energy light through a light transmission window provided in the reaction container, and is capable of producing a In an optical CVD apparatus for decomposing a raw material gas and forming a deposited film on a support installed in the reaction vessel, a cooling means for cooling the light transmission window is disposed in the reaction vessel. It is characterized by being done.

Embodiment C] Hereinafter, the photo-CVD apparatus of the present invention will be described in detail according to the drawings.

As shown in FIG. 1, the optical CVD apparatus of the present invention basically includes a reaction vessel 1, means for introducing raw material gas, and a high-energy light generation device 14.

A desired support 3 on which a deposited film is to be formed is carried into the reaction vessel 1 and placed on a support table 2 . The support 3 may be conductive, semiconductive, or electrically insulating. For example, electrically insulating supports include polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, and polyvinyl chloride. Films or sheets of synthetic resins such as vinylidene chloride, polystyrene, polyamide, glass, ceramics, paper, etc. are commonly used. Moreover, an electrode layer, another silicon layer, etc. may be laminated on the support 3 in advance.

A heater 4 for heating the support is disposed at the bottom of the support base 2, and is supplied with power through a conductor 5 to generate heat.0 Temperature of the support when forming a deposited film using the apparatus of the present invention is not particularly limited, but is preferably 50 to 150°C, more preferably 100 to 150°C.

The raw material gas supply sources are indicated by 6 to 9, and when a liquid silicon hydride compound is used, an appropriate vaporizer is provided. There are two types of vaporizers, such as a type that uses heating and boiling, and a type that allows a carrier gas to pass through during liquid measurement, and any of them may be used. The number of gas supply sources is not limited to four, and the type of silicon hydride compound used as the raw material gas.

When using alkaline or halogen gas, carrier gas, diluent gas, catalyst gas, etc., they are appropriately selected depending on whether or not they are premixed with the silicon hydride compound that is the raw material gas. For the raw material gas supply sources 6 to 9, the suffix a indicates a branch pipe, the suffix b indicates a flow meter, and the suffix C indicates a valve for opening/closing each gas flow and adjusting the flow rate. be.

Raw material gases and the like supplied from each gas supply source are mixed in the middle of the gas introduction pipe 10 and introduced into the reaction vessel 1 . 1
1 is a pressure gauge for measuring the pressure of gas introduced into the reaction vessel 1. Further, 12 is a gas exhaust pipe,
It is connected via a valve 13 to an exhaust device (not shown) for reducing the pressure inside the reaction vessel 1 and forcibly exhausting introduced gas.

When forming a deposited film by the photo-CVD method using the photo-CVD apparatus of the present invention, it is preferable that the inside of the reaction vessel 1 be placed under reduced pressure, but the deposited film may also be formed under normal pressure or pressurization. I can do it.

When forming a deposited film by photo-CVD under reduced pressure,
Before introducing raw material gas, etc., the inside of the reaction vessel 1 is evacuated, and the atmospheric pressure inside the reaction vessel 1 is preferably 5 x 10' To
rr or less, more preferably I x 10-' Torr
The following shall apply. Further, the pressure inside the reaction vessel 1 when the raw material gas etc. is introduced is preferably lXl0' to 100 To
rr, more preferably 1×10°” to I Torr.

As the high-energy light generating device 14, for example, a mercury lamp, a xeno lamp, a carbon dioxide laser, an argon ion laser, a nitrogen laser, an excimer laser, etc. are used. Note that the light energy used in the present invention is not limited to ultraviolet rays, but can be used to excite and decompose raw material gas,
The wavelength range does not matter as long as the decomposition products can be deposited on the support.In addition, the light energy is absorbed by the raw material gas or the support and converted into thermal energy, and the thermal energy , the source gas is excited 1
The light 15 directed from the high-energy light generating device 14 to the support 3, which does not exclude the case where it is decomposed to form a deposited film, is transmitted through the light-transmitting window 1B provided in the reaction vessel 1.
is irradiated with the raw material gas etc. flowing in the direction of the arrow 17, the raw material gas etc. are excited and decomposed, and a deposited film of a-3i is formed on the entire surface or a desired portion of the support 3. If a suitable optical system is attached to the high-energy light generating device 14, it is possible to irradiate the entire surface of the support 3 to form a deposited film, or selectively and controllably irradiate only the desired portion. A deposited film can also be formed. The photo-CVD method also has the convenience of being able to form a deposited film by irradiating only a predetermined graphical portion using a resist or the like.

When a hydrogen silicon compound as a raw material gas introduced into the reaction vessel 1 is excited and decomposed to form an a-9i deposited film, gaseous hydrogen and halogen compounds (
For example, F2 gas, C12 gas, gasified Br2,
12, etc.). By introducing these, a radical generation reaction occurs between Si, H, and halogen atoms, and the formation of a deposited film is promoted.
It is expected that halogen atoms will be incorporated into the deposited film to reduce structural defects and also act as terminators to bond with Si dangling bonds, forming a high-quality silicon film. The halogen to be introduced may be radicalized in advance, and two or more types of silicon hydride compounds may be used in combination, but in this case, the expected film properties of each compound should be averaged. ,
Or synergistically improved properties can be obtained.

In this way, a desired a-Si deposited film is formed on the support 3, but as described above, during the deposition, the light transmitting window IB
An a-Si deposited film similar to that on the surface of the support 3 is also deposited on the wall surface of the reaction chamber, which lowers the transmittance of the light 15 of the light transmission window 1B and reduces the rate of formation of the deposited film on the support 3. . Therefore, in the photoCVD apparatus of the present invention, in the reaction vessel,
A cooling means 18 for cooling the light transmission window 1B is provided in the reaction vessel 1. In this example, the cooling means 18 is configured as a window frame of a light transmitting window 1B through which a refrigerant can flow. As the refrigerant flowing into the window frame, various fluids such as water, dry ice-methanol solvent, liquid nitrogen, etc. can be used.

21 is a refrigerant inlet, and 22 is a refrigerant outlet. In this way, by suppressing the temperature rise of the light transmission window IB by the cooling means 18, the a-Si to the light transmission window IB is suppressed.
Film deposition can be effectively prevented.

FIGS. 2 and 3 are schematic partial cross-sectional views showing other embodiments of the cooling means 18 in the optical CVD apparatus of the present invention. In the case of the second cause, the light transmitting window 16 is directly processed,
A refrigerant flow path is provided within the light-transmitting plate that constitutes the light-transmitting window 1B. In the case of FIG. 3, the light transmitting window 1B is formed by two light transmitting plates, and the coolant is allowed to flow between these light transmitting plates.

In this case, the coolant flowing between the light-transmitting plates must be one that transmits the light 15 emitted from the high-energy light generator 14.

〔Effect of the invention〕

As explained above, the photoCVD apparatus of the present invention prevents film deposition on the light transmission window by suppressing the temperature rise of the light transmission window, and maintains a constant film deposition rate on the support. This enables the production of high quality a-9i deposited films.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of the optical CVD apparatus of the present invention. FIGS. 2 and 3 are schematic partial cross-sectional views showing other embodiments of the cooling means in the optical CvD apparatus of the present invention. FIG. 4 is a graph showing the temperature rise of the light transmitting window made of synthetic quartz when high energy light is irradiated onto the light transmitting window. 1-m-reaction container 2-m-support stand 3--support body 4-11 heater 5--conductor wires 6 to 9-m-gas supply source 10-m-gas introduction pipe 11-m-pressure gauge 12--
-Gas exhaust pipe 13-m-Bulb 14--High energy light generator 15--Ikko 1B---Light transmission window
17--Flow of raw material gas 18--1 Cooling means
19-11 Refrigerant introduction 20--- Refrigerant outlet! A2 figure 3

Claims (1)

[Claims] 1) Comprising a reaction vessel, a means for introducing a raw material gas into the reaction vessel, and a means for irradiating the raw material gas with high-energy light through a light transmission window provided in the reaction vessel. In a photo-CVD apparatus for decomposing the raw material gas using a photochemical reaction and forming a deposited film on a support installed in the reaction vessel, the light transmission window is cooled in the reaction vessel. 1. An optical CVD apparatus characterized in that a cooling means is provided for the purpose of cooling.