JPH0334538A - Optical pumping reaction apparatus - Google Patents

Abstract

PURPOSE:To deposit a sufficiently thick and uniformly thick film on the surface of a specimen by a method wherein a light-transmitting window is cooled uniformly so that a film formation operation can be controlled in any position on the surface of the light-transmitting window. CONSTITUTION:A glass substrate as a specimen 20 is housed inside a reaction container 1; a pressure inside the reaction container 1 is reduced by using an evacuation pump 5; a temperature of the specimen 20 is raised up to 250 deg.C by using a heater 3. On the other hand, nitrogen gas which is used as a coolant is cooled by using a cooling apparatus 16 and is supplied to a space between a first light-transmitting window and a second light-transmitting window 6, 8 through a coolant supply pipe 14. While the gas is circulated to the cooling apparatus 16 through a coolant discharge pipe 15, it cools the first light-transmitting window 6 down to-10 deg.C. The space between the first light-transmitting window 6 and the second light-transmitting window 8 is divided into a plurality of spaces by a plurality of partition walls 13 which have been installed in parallel along an incident direction (vertical direction) of light from a low-pressure mercury pump 10; the coolant supply pipe 14 and the discharge pipe 15 are connected respectively in such a way that a flow direction of the coolant becomes a reverse direction in mutually adjacent spaces.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an improvement in a photoexcitation reaction device that forms a thin film using a photochemical reaction.

(Prior Art) In recent years, a method has been developed in which a chemical reaction using light energy is used to decompose a compound gas and form a thin film on the surface of a sample such as a semiconductor wafer or glass. This method is optical CV
This method is called D and has features such as being able to form a film at a lower temperature than normal thin film forming methods and being free from damage caused by charged particles. For this reason, photo-CVD is attracting attention as a technology that will play an important role in future thin film formation technology.

However, the photo-CVD method has problems due to film formation on the surface of the light-transmitting window. In other words, except for some insulating films,
The desired film is opaque to the wavelength of the light used. Therefore, as the light irradiation time increases, the thickness of the film formed on the surface of the light transmission window increases, and the intensity of the light entering the reaction chamber decreases, resulting in the deposition of a thick film. The problem is that it becomes difficult.

In order to solve this problem, the following methods have been proposed conventionally.

For example, a method has been proposed in which a light-transmitting window is coated with an oil that has a low vapor pressure and is transparent to the wavelength of the light used to prevent the film from adhering to the window. However, with this method, there is a risk that oil components may be incorporated into the membrane as impurities.

A method of spraying an inert gas onto a light-transmitting window has also been proposed. However, this method has a problem in that the pressure inside the reaction chamber increases and the source gas is diluted, resulting in a decrease in the rate of film deposition on the sample surface.

In addition, a method has been proposed in which the light-transmitting windows are doubled and cooling is performed by flowing a refrigerant into the space between the light-transmitting windows (Japanese Unexamined Patent Publication No. 81-1
Publication No. 39022). With this method, film formation on the surface of the light-transmitting window can be suppressed by cooling the light-transmitting window without causing the above-mentioned problems, and a thick film can be easily deposited on the sample surface. Become. However, with this method, a temperature difference occurs in the refrigerant between the entrance and exit sides of the space between the double light-transmitting windows, and therefore a temperature difference also occurs in the light-transmitting window, and the surface of the light-transmitting window There is a possibility that the state of the film formation will be different (that is, on the surface of the light-transmitting window, the film is thinner on the refrigerant inlet side and thicker on the outlet side). in this case,
The intensity of the light irradiated from the light source differs depending on the position on the sample surface, and the deposition rate of the film varies, resulting in variations in the thickness of the film deposited on the sample surface. This trend is
As the size of the light transmission window increases as the sample size increases,
It's becoming more and more noticeable.

(Problems to be Solved by the Invention) The present invention attempts to solve the above-mentioned conventional problems, and is intended to prevent or prevent the deposition of a film on the surface of a light-transmitting window without introducing impurities into the film. By reducing
The object of the present invention is to provide a photoexcitation reaction device that can deposit a thick and uniform film on the surface of a sample.

[Structure of the Invention] (Means for Solving the Problems) The photoexcitation reaction apparatus of the present invention accommodates a sample in a reaction chamber, introduces a raw material gas, and allows light to enter the reaction chamber from a light source through a light transmission window. , a photoexcitation reaction device for photoexcited decomposition of the source gas to form a film on the surface of the sample, including a plurality of light transmission windows provided at intervals between the reaction chamber and the light source; A partition wall provided along the incident direction of light and dividing the space between the light transmission windows into a plurality of spaces, and a cooling means for supplying a coolant to each of the plurality of spaces between the light transmission windows divided by the partition wall. It is characterized by the following:

The photoexcitation reaction device of the present invention is preferably provided with a supply means such that the flow direction of the refrigerant supplied to the plurality of spaces between the light transmission windows divided by the partition walls is reversed in the adjacent spaces.

Further, it is preferable that the photoexcitation reaction device of the present invention is provided with a drive mechanism that swings the light source in a plane parallel to the light transmission window.

(Function) When the photoexcitation reaction device of the present invention is used, a plurality of light transmission windows are provided at intervals between a reaction chamber and a light source, and the space between the light transmission windows is divided into a plurality of spaces by a partition wall. Since refrigerant is supplied to each of the multiple spaces between the divided light transmission windows,
By cooling the light-transmitting window, it is possible to suppress film formation on the surface of the light-transmitting window, and since the light-transmitting window can be cooled more uniformly than before, it is possible to create a thick and uniform film on the sample surface. Films can be deposited. This is particularly effective when the film to be deposited on the sample surface is deposited at high temperatures but not at low temperatures or at a low deposition rate.

Furthermore, if the refrigerant is supplied to a plurality of spaces between the light-transmitting windows divided by partition walls so that the flow direction of the refrigerant is opposite in the adjacent spaces, the light-transmitting windows can be evenly distributed. This is effective in making the thickness of the film deposited on the sample surface uniform. Furthermore, if the light source is oscillated in a plane parallel to the light transmission window, the intensity of the light emitted from the light source can be made uniform regardless of the position of the sample surface, thereby reducing the amount of deposits on the sample surface. This is effective in making the film thickness uniform.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a schematic configuration diagram of an optical CVD apparatus according to the present invention, and FIG. 2 is a plan view showing a partition wall provided in a space between light transmission windows of the optical CVD apparatus.

In FIG. 1, the interior of a reaction vessel 1 serves as a reaction chamber, and a sample stage 2 is provided at the bottom of the reaction vessel 1, and a sample 20 made of, for example, a glass substrate is placed on this sample stage 2. Inside the sample stage 2 is a heater 3 that heats the sample 20.
is provided. A raw material gas containing a compound gas is introduced into the reaction vessel 1 from the gas supply section 4 , and the gas within the reaction vessel 1 is exhausted by the exhaust pump 5 . A first light transmitting window 6 is attached to the upper surface of the reaction vessel 1 at a position corresponding to the sample stage 2 . A lamp house 7 is provided in the upper part of the reaction vessel 1, and a second light transmitting window 8 is attached to the lower surface of the lamp house 7 parallel to the first light transmitting window 6 and spaced apart from each other by a predetermined distance. There is.

A low-pressure mercury lamp lO is provided in the lamp house 7 in the vicinity of the second light-transmitting window 8 via a reflector plate 9 that reflects ultraviolet light. Inert gas is inert gas supply pipe 11
is supplied into the lamp house 7 through the lamp house 7.
The interior of the lamp house 7 is purged, and the inert gas is discharged from the inside of the lamp house 7 through an inert gas exhaust pipe 12.

As shown in FIG. 2, the space between the first light transmission window 6 and the second light transmission window 8 is provided in parallel along the incident direction (vertical direction) of light from the low-pressure mercury lamp IO. It is divided into a plurality of spaces by a plurality of partition walls 13. These partition walls i3 are made of the same material as the light transmitting window. A refrigerant supply pipe 14 and a discharge pipe 15 are respectively connected to the plurality of spaces divided by the partition wall 13 so that the flow direction of the refrigerant is opposite in mutually adjacent spaces. A refrigerant (for example, nitrogen gas) is supplied from the cooling device 16 through the supply pipe 14 to the space between the first and second light transmitting windows 6.8, and is supplied to the space adjacent to each other as indicated by the arrows in FIG. It flows in the opposite direction and is circulated through the refrigerant discharge pipe 15 to the cooling device 16.

A case will now be described in which an amorphous silicon film is formed on the surface of the sample 20 using a CVD apparatus.

A glass substrate is housed as a sample 20 in the reaction vessel 1, the pressure inside the reaction vessel 1 is reduced by the exhaust pump 5, and the temperature of the sample 20 is raised to 250° C. by the heater 3. On the other hand, nitrogen gas used as a refrigerant is cooled by a cooling device 16,
The first and second light transmitting windows 6.
By supplying the refrigerant to the space between the first light transmitting windows 6 and 8 and circulating it to the cooling device 16 through the refrigerant discharge pipe 15, the first light transmitting window 6 is
Cool to 0°C.

Monosilane (SiH4) containing mercury is supplied as a reaction gas from the gas supply section 4 at a flow rate of 105c and a pressure of 0.3.
It is introduced into the reaction vessel 1 at Torr. Low pressure mercury lamp I
Ultraviolet rays with wavelengths of 254 nm and 185 nm are applied to the second
The sample 20 housed in the reaction vessel 1 is irradiated through the light transmission window 8 and the first light transmission window 6 . As a result, sample 2
An amorphous silicon film is deposited on the 0 surface. Note that nitrogen gas used as a refrigerant has wavelengths of 254 cm and 1
It hardly absorbs ultraviolet rays of 85 r+m.

Under these conditions, even if the amorphous silicon film is deposited on the surface of the sample 20 to a thickness of tog, the first light transmitting window 6
Almost no film deposition occurred on the surface. The variation in film thickness of the amorphous silicon film deposited on the surface of sample 20 was ±10%.

In addition to the above-mentioned configuration, a photo-CVD apparatus equipped with a drive mechanism (not shown) for swinging the low-pressure mercury lamp 10 in a plane parallel to the light transmission window was used to coat the sample surface under the same conditions as above. When an amorphous silicon film was deposited, the film thickness variation was ±5%.

On the other hand, when an amorphous silicon film is deposited on the sample surface under the same conditions as above using a conventional photo-CVD device that has only one light transmission window and does not cool the light transmission window, The variation in film thickness was ±15%.

Note that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the gist thereof.

For example, the film to be deposited on the sample surface is not limited to an amorphous silicon film, but may be any film that does not deposit at low substrate temperatures or has a low deposition rate. Furthermore, when the target film is an amorphous silicon film, the raw material gas is not limited to monosilane, but may also be disilane (S12H6), etc. Furthermore, diborane (
82H6) Phosphine (PH3), Acetylene (C2H
2) etc. may be mixed. Alternatively, the raw material gas may not contain mercury and the reaction may be caused by direct excitation.

Reaction conditions, such as pressure inside the reaction vessel, flow rate of raw material gas,
The substrate temperature, the cooling temperature of the light transmission window, etc. can be appropriately set depending on the intended film.

The light source is not limited to a low-pressure mercury lamp, but may also be a deuterium lamp, a light source using microwave discharge of rare gas, or the like. The heater is not limited to a resistance heater, but may also be a halogen lamp or the like. The refrigerant is not limited to nitrogen gas; it may be a gas or liquid as long as it absorbs little light emitted from the light source.
As the gas, for example, an inert gas such as helium, argon, or xenon, or hydrogen can be used, and as the liquid, for example, perfluoropolyether can be used. Furthermore, although the refrigerant was circulated in the above embodiment, if a relatively inexpensive gas such as nitrogen gas is used as the refrigerant, it is not necessarily necessary to circulate it and it is not necessary to release it into the atmosphere and recover it.

〔Effect of the invention〕

As detailed above, by using the photoexcitation reaction device of the present invention, it is possible to uniformly cool the light transmission window and suppress film formation at any position on the surface of the light transmission window. A film with uniform thickness can be deposited.

[Brief explanation of drawings]

FIG. 1 is a schematic structural diagram of an optical CVD apparatus according to the present invention, and FIG. 2 is a plan view showing a partition wall provided in a space between light transmission windows of the optical CVD apparatus. DESCRIPTION OF SYMBOLS 1... Reaction container, 2... Sample stand, 3... Heater 4... Gas supply part, 5... Exhaust pump, 6... First light transmission window, 7... Lamp House, 8... Second light transmitting window, 9... Reflector, 10... Low pressure mercury lamp, 11... Inert gas supply piping, 12... Inert gas discharge piping, 13. ... Partition wall, 14 ... Refrigerant supply pipe, 15 ... Refrigerant discharge pipe, 16 ... Cooling device, 20
···sample.

Claims (3)

[Claims] (1) A sample is housed in a reaction chamber, a raw material gas is introduced, and light is incident from a light source into the reaction chamber through a light transmission window to decompose the raw material gas through photoexcitation, thereby forming a film on the surface of the sample. In the photoexcitation reaction device, a plurality of light transmitting windows are provided at intervals between the reaction chamber and the light source, and a plurality of light transmission windows are provided along the incident direction of light from the light source,
A photoexcitation reaction device comprising a partition wall that divides the space between the light transmission windows into a plurality of spaces, and a cooling means that supplies a coolant to each of the plurality of spaces between the light transmission windows divided by the partition wall. . (2) Claim (1) characterized in that a supply means is provided such that the flow direction of the refrigerant supplied to the plurality of spaces between the light transmitting windows divided by the partition walls is reversed in the adjacent spaces. ) The photoexcitation reaction device described in . (3) The photoexcitation reaction device according to claim (1), further comprising a drive mechanism for swinging the light source in a plane parallel to the light transmission window.