JPH059516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to deposited films containing silicon, particularly amorphous silicon (hereinafter abbreviated as a-Si), which is useful as a photoconductive film, a semiconductor film, or an insulating film. The present invention relates to a deposited film forming apparatus suitable for forming a deposited film of polycrystalline silicon or the like.

[Conventional technology]

Conventionally, glow discharge deposition and thermal energy deposition have been known as methods for forming deposited films using silicon hydride compounds such as SiH ₄ and Si ₂ H ₆ as raw materials. These deposition methods are methods in which a silicon hydride compound or the like is excited and decomposed using electrical energy or thermal energy to form a deposited film of a-Si on a support. The deposited film thus obtained is used for various purposes.

However, in the glow discharge deposition method, under high output, the influence of discharge energy on the a-Si film being deposited is large, making it difficult to control conditions reproducibly and stably. 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 the a-Si film will be desorbed due to high temperatures. It is difficult to obtain a deposited film with these 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 deposition method of a-Si deposited film using optical energy (optical
CVD method) has been proposed and is attracting attention. According to this optical CVD method, the above-mentioned problems can be significantly improved due to the advantage that the a-Si deposited film can be produced at low temperature and by an ion-free reaction.

[Problem that the invention seeks to solve]

However, in the optical CVD method, an a-Si deposited film is also formed on the light transmitting window of the deposited film forming device, which greatly reduces the transmittance of incident light into the reaction vessel and prevents the deposition on the support. A new problem has arisen which is to reduce the rate of film formation.

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 may lead to the contamination of the deposited film with impurities such as oil molecules.
There was a problem that the high quality of the film, which is a characteristic of the photo-CVD method, was impaired.

The present invention has been made to solve the above-mentioned problems in the optical CVD method.

An object of the present invention is to provide a deposition method for optical CVD that can produce high-quality silicon films while keeping the film deposition rate constant on a support by preventing deposition on a light-transmitting window. An object of the present invention is to provide a film forming apparatus.

[Means for solving problems]

That is, the deposited film forming apparatus of the present invention includes a reaction vessel, a means for introducing a raw material gas into the reaction vessel, and a high-energy light applied to the raw material gas through a light transmission window provided in the reaction vessel. In a deposited film forming apparatus for decomposing the source gas using a photochemical reaction and forming a deposited film on a support carried into the reaction vessel,
The method is characterized in that an electron gun and a counter electrode are disposed near the light transmission window inside the reaction vessel.

〔Example〕

Hereinafter, the deposited film forming apparatus of the present invention will be explained in detail with reference to the drawings.

As shown in FIG. 1, the deposited film forming apparatus of the present invention basically includes a reaction vessel 1, means for introducing source gas, and a high-energy light generating 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 any conductive, semiconductive or electrically insulating support, for example,
As electrically insulating supports, films or sheets of synthetic resins such as polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, glass, ceramic, paper, etc. are usually used. Ru. 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 lower part of the support base 2, and is supplied with electricity via a conductive wire 5 to generate heat. The 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 shown in 6 to 9, and when using liquid silicon hydride compounds,
Equip with appropriate vaporization equipment. The vaporizer may be of any type, such as a type that utilizes heating and boiling, or a type that allows a carrier gas to pass through during liquid measurement. The number of gas supply sources is not limited to four, and the type of silicon hydride compound used as the raw material gas,
Alternatively, in the case of using a halogen gas, carrier gas, diluent gas, catalyst gas, etc., it is selected as appropriate depending on whether or not it is premixed with the silicon hydride compound that is the raw material gas. Raw material gas supply source 6~
To the reference numeral 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.

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 . 11 is a pressure gauge for measuring the pressure of gas introduced into the reaction vessel 1. Further, 12 is a gas exhaust pipe, which is connected via a valve 13 to an exhaust device (not shown) for reducing the pressure inside the reaction vessel 1 and forcibly exhausting raw material gas and the like.

When forming a deposited film by the optical CVD method using the deposited film forming apparatus of the present invention, the inside of the reaction vessel 1 is
Although it is preferable to use the method under reduced pressure, the deposited film can also be formed under normal pressure or increased pressure.

When forming a deposited film by optical CVD under reduced pressure, the reaction vessel 1 must be
The inside of the reaction vessel 1 is evacuated, and the atmospheric pressure inside the reaction vessel 1 is preferably 5×10 ^-5 Torr or less, more preferably 1×
It is assumed to be below 10 ^-6 Torr. Further, the pressure inside the reaction vessel 1 when the raw material gas etc. is introduced is preferably 1
×10 ^-2 ~100Torr, more preferably 1×10 ^-2 ~
It is 1 Torr.

Examples of the high-energy light generator 14 include a mercury lamp, a xeno lamp, a carbon dioxide laser,
Argon ion laser, nitrogen laser, excimer laser, etc. are used. Note that the light energy used in the present invention is not limited to ultraviolet light, but may be any wavelength range as long as it can excite and decompose the raw material gas and deposit the decomposition products on the support. isn't it. Furthermore, the present invention does not exclude cases in which light energy is absorbed by the source gas or the support and converted into thermal energy, and the source gas is excited and decomposed by the thermal energy to form a deposited film. Light 15 directed from the high-energy light generator 14 to the support 3 is irradiated onto the raw material gas etc. flowing in the direction of the arrow 17 through the light transmission window 16 provided in the reaction vessel 1. A deposited film of a-Si is formed on the entire surface or a desired portion of the support 3 by exciting and decomposing the gas.
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 control and irradiate only the desired portion to form a partial film. A deposited film can also be formed. The optical CVD method also has the convenience of being able to form a deposited film by irradiating only a predetermined graphical area 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-Si deposited film, gaseous hydrogen and halogen compounds (e.g. F ₂ gas, Cl ₂ gas,
It is desirable to introduce gasified Br ₂ , I _{2 ,} etc.). By introducing these, a radical generation reaction occurs between Si, H, and halogen atoms, promoting the formation of a deposited film, and halogen atoms are incorporated into the formed deposited film, reducing structural defects. It is also expected to act as a terminator that combines with Si dangling bonds, forming a high-quality silicon film. The halogen to be introduced may be radicalized in advance. In addition, two or more types of silicon hydride compounds may be used in combination, but
In this case, properties that are the average of the film properties expected from each compound, or properties that are synergistically improved can be obtained.

In this way, the desired a-Si deposited film is formed on the support 3. However, as mentioned above, during the deposition, the same a-Si deposited film as on the surface of the support 3 is also deposited on the wall surface of the reaction chamber of the light transmission window 16. -Si deposited film is deposited, which reduces the transmittance of the light 15 of the light transmission window 16 and reduces the rate of formation of the deposited film on the support 3. Therefore, in the deposited film forming apparatus of the present invention, the electron gun 18 and its counter electrode 19 are arranged in the vicinity of the light transmission window 16 in the reaction vessel 1 . It is preferable that the electron gun 18 and the counter electrode 19 be arranged in a plane substantially parallel to the light transmission window 16. Normally, the source gas etc. flows in the direction of the arrow 14, but some of it also exists near the light transmission window 16, is excited and decomposed by the light 15, and a deposited film is also deposited on the light transmission window 16. . However, when the electron beam 20 is emitted from the electron gun 15 toward the counter electrode 16, complex reactions occur due to electron impact, electron adhesion, etc., including the generation of weakly ionized plasma, the formation of electron clouds, and recombination. A reaction process occurs near the emission part of the electron beam 20. Under such conditions, reactions such as excitation, decomposition, and deposition of the source gas by the light 15 are slowed down, so that the deposited film on the light transmission window 16 located near the emission part of the electron beam 20 is reduced. The deposition is suppressed and only the deposition of the a-Si film on the support 3 is achieved.

The coil 21 is for generating a magnetic field within the reaction vessel 1 in a direction substantially perpendicular to the direction of the electron beam 20 . When an alternating current is passed through the coil 21, the direction of the generated magnetic field changes depending on the direction of the current. FIG. 2 is a diagram showing how the electron beam 20 emitted from the electron gun 15 is bent by the Lorentz force due to magnetic fields 22 and 23 in different directions. In this way, by applying an alternating current to the coil 21 and changing the direction of the magnetic field, it is possible to cause the electron beam to vibrate and scan in a fan shape in a plane substantially parallel to the light transmission window 16. By scanning the electron beam in this manner, it is possible to prevent most of the film from being deposited on the light transmission window 16 even by disposing a single electron gun 15.

〔Effect of the invention〕

As explained above, the deposited film forming apparatus of the present invention prevents the deposition of a film on the light transmission window by emitting an electron beam near the light transmission window of the reaction vessel, and prevents the film from being deposited on the support. This makes it possible to produce a high quality a-Si deposited film while keeping the speed constant.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a deposited film forming apparatus of the present invention. FIG. 2 is a diagram showing the emission direction of an electron beam when a magnetic field is applied to the deposited film forming apparatus of the present invention. 1... Reaction container, 2... Support base, 3...
Support, 4...Heater, 5...Conducting wire, 6-9...
... Gas supply source, 10 ... Gas introduction pipe, 11 ... Pressure gauge, 12 ... Gas exhaust pipe, 13 ... Valve, 1
4... High energy light generator, 15... Light, 1
6... Light transmission window, 17... Flow of source gas, 18
...Electron gun, 23...Counter electrode, 20...Electron beam, 21...Coil, 22...Magnetic field (direction perpendicular to the paper and toward the back surface), 23...Magnetic field (direction perpendicular to the paper surface and toward the surface) ).

Claims (1)

[Scope of Claims] 1. 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 deposited film forming apparatus for decomposing the raw material gas using a photochemical reaction and forming a deposited film on a support carried into the reaction container, Near the light transmission window,
A deposited film forming apparatus comprising an electron gun and an opposing electrode. 2. The deposition according to claim 1, wherein a magnetic field generating means for generating a magnetic field in a direction substantially perpendicular to the direction of the electron beam emitted from the electron gun toward the counter electrode is attached to the reaction vessel. Film forming device.