JPS6150149B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for depositing photochemical reaction products onto a substrate.

Recently, research has been conducted into methods of forming vapor deposited films of amorphous silicon used in photosensitive drums of electronic copying machines, solar cells, and the like. On the other hand, vapor deposition methods are also used to form various insulating films and protective films.
Various vapor deposition methods have been proposed depending on the application, but among these, the photochemical vapor deposition method that uses photochemical reactions has the advantage of being extremely fast in film formation and being able to form a uniform film even on large areas. have,
It has been attracting particular attention recently.

The conventional equipment used for this photochemical vapor deposition method is to place the substrate in a reaction vessel with an ultraviolet-transmissive window, flow a photoreactive gas under reduced pressure, and use an ultraviolet lamp outside the reaction vessel to cause a photochemical reaction. The product is adapted to be deposited onto the substrate. The ultraviolet ray transmitting window is made of a material that easily transmits ultraviolet rays, such as quartz glass, lithium fluoride, and magnesium fluoride.

By the way, as described above, this photochemical vapor deposition method has the property of being able to form a uniform film even over a large area, so there is a strong tendency in recent years to take advantage of this property to increase the area of the substrate. For this purpose, the device first uses a plurality of tubular ultraviolet lamps arranged side by side to uniformly irradiate ultraviolet rays to form a surface light source, and of course the area of the ultraviolet transmitting window is also expanded. The pressure inside the reaction vessel is reduced to several Torr, so a pressure difference between the atmospheric pressure and the atmospheric pressure is applied to the ultraviolet transmission window, but as this area increases, the load increases proportionally, so the thickness of the quartz glass plate used is must be made larger. For example, if the UV-transmitting window is circular with a diameter of about 160 mm, the thickness of the quartz glass needs to be nearly 10 mm, which not only increases cost but also makes the glass board thicker even though it is a material that easily transmits UV rays. In this case, a problem arose in that permeation was inhibited and efficiency was reduced.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a photochemical vapor deposition apparatus capable of efficiently depositing a uniform film even on a large-area substrate. This device is characterized by arranging a plurality of ultraviolet lamps in parallel on the ultraviolet transmitting window of the device, making the potential difference between adjacent lamp lead-in lines below the discharge breakdown voltage, and reducing the pressure inside the lamp body. In other words, by reducing the pressure inside the lamp body, the pressure difference between the pressure inside the reaction vessel and the inside of the reaction vessel can be reduced, thereby making it possible to reduce the thickness of the transparent window.On the other hand, reducing the pressure inside the lamp body causes the problem of discharge breakdown. This is prevented by keeping the potential difference between adjacent lamp lead-in lines below the discharge breakdown voltage.

Embodiments of the present invention will be specifically described below with reference to the drawings.

The reaction vessel 1 has a photoreactive gas introduction hole 11,
An exhaust hole 12 connected to a pressure reducing device is provided, and a substrate support stand 13 made of quartz glass is provided at the center of the interior. A UV transmitting window 14 made of quartz glass is provided on the top surface, and a lamp body 2 is integrally installed on the top of the window 14, and a plurality of UV lamps 3 are arranged in a row on the ceiling of the window 14 through a reflective member 21. An exhaust hole 22 for reducing the pressure inside the lamp body 2 is provided in the side wall.

Here, the ultraviolet lamp 3 is an alternating current lighting low-pressure mercury lamp with a tube diameter of 30 mm, a lighting start voltage of 250 V, a lighting voltage of 45 V, and a current of 5 A, and the shortest distance between adjacent lamp lead-in lines is 2 cm. And the number inside the light body 2 is
When the pressure is reduced to Torr, the discharge breakdown voltage will be approximately 300V under these conditions.If the lead-in wires of the ultraviolet lamp 3 are randomly connected and the phases of adjacent lead-in wires are shifted, resulting in opposite potentials, there will be a maximum A voltage of 700V is applied, easily causing discharge damage. Therefore, in order to prevent this, the ultraviolet lamps 3 are connected in such a way that the phases of the ultraviolet lamps 3 are aligned and the potential difference between the lead-in lines is below the discharge breakdown voltage.

The temperature of the substrate 4 supported by the substrate support stand 13 is approximately 150°C.
It is a circular alumina plate with an outer diameter of 152 mm. The photoreactive gas introduced from the introduction hole 11 has a partial pressure of 5 mm as a carrier gas.
Argon of Hg, partial pressure 3×10 ^-3 mm as photosensitizer
It is a mixed gas consisting of mercury of Hg and silicon tetrahydride with a partial pressure of 0.3 mmHg as a decomposition vapor deposition gas. When the above-mentioned low-pressure mercury lamp is turned on and irradiated with ultraviolet rays, silicon tetrahydride is photodecomposed and amorphous silicon is formed. It is deposited on the substrate 4. At this time, the inside of reaction vessel 1 is also several Torr.
However, since the pressure inside the lamp body 2 is also reduced, there is almost no pressure difference between the two sides of the quartz glass of the ultraviolet transmitting window 14. Even if the plate thickness is 2
mm is sufficient, and the amount of ultraviolet rays absorbed by this is small and can be irradiated efficiently.

As explained above, in the present invention, multiple ultraviolet lamps are installed in parallel, so even a large substrate can be uniformly irradiated with ultraviolet rays, and since the inside of the lamp is depressurized in the same way as the inside of the reaction vessel, a large amount of ultraviolet rays can pass through. The thickness of windows can be thin, and the transmission of ultraviolet rays is not obstructed. Furthermore, the problem of discharge breakdown caused by reducing the pressure inside the lamp body has been solved by aligning the phases and reducing the potential difference, so that the present invention provides a photochemical vapor deposition apparatus that can uniformly and efficiently deposit even large-area substrates. I can do it.

[Brief explanation of the drawing]

The drawings are cross-sectional views showing embodiments of the present invention. 1... Reaction container, 2... Lamp body, 3... Ultraviolet lamp,
4...Substrate, 14...UV transmitting window.

Claims (1)

[Claims] 1 Place the substrate in a reaction vessel under reduced pressure that has a window for transmitting ultraviolet light, flow a photoreactive gas, cause the gas to undergo a photochemical reaction using an ultraviolet lamp outside the reaction vessel, and deposit the reaction product on the substrate. 1. A photochemical vapor deposition device, characterized in that a plurality of the ultraviolet lamps are arranged in parallel inside a lamp body, the potential difference between adjacent lamp lead-in lines is made equal to or less than a discharge breakdown voltage, and the pressure inside the lamp body is reduced.