JPS62183851A - Light irradiating window - Google Patents

Abstract

PURPOSE:To reduce the accumulation of a film onto the surface of a window material by reducing the adsorption of reactive gas, by bonding a group such as a hydrocarbon group, a halogenated hydrocarbon group or a carbon halide group to the surface of the light irradiating window material for optical CVD reaction. CONSTITUTION:When the surface of a window material comprising SiO2 is immersed in an aqueous solution of R-Si(OH)3 or an alcohol solution thereof and subsequently heat-treated, the surface from which R is issued as shown by a drawing is obtained. By using a hydrocarbon, halogenated hydrocarbon or carbon halide group having a relatively large MW as R, the dipole moment of the surface is markedly lowered and the surface becomes hard to adhere a gas molecule. By this method, the accumulation of a film onto the surface of the window material can be reduced and the washing or replacing cycle of the window material can be extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a light irradiation window for photo-CVD reactions.

[Conventional technology]

Introducing a reactive gas onto the substrate surface, such as in photo-CVD,
In an apparatus in which a reactive gas is reacted in the gas phase or on the surface of a substrate by irradiating it with light, a light-transmitting window is required between the light source and the container into which the reactive gas is introduced. At this time, if the introduced center-of-center gas diffuses into the container, reacts and decomposes near the surface of the window on the container side, decomposed products adhere to the window, resulting in poor light transmittance. In the conventional method, in order to avoid this, a non-reactive gas such as He is flowed near the surface of the window on the container side to prevent the reactive gas from diffusing near the surface of the window.

For example, as shown in FIG. 6, a light-transmitting window 2 is attached to a container 1 into which a reactive gas is introduced, and an inlet 3 for a non-reactive gas is provided near the window, and a gas supply source 4 is connected. I'll leave it there. When the inside of the container L is made into an atmosphere containing a reactive gas, and light is irradiated from the light source 6 through the window 2 toward the vicinity of the sample 5 to decompose the reactive gas in the gas phase or on the sample surface, it is possible to decompose the reactive gas near the inner surface of the window. The decomposed chemical species will adhere to the inside of the window. To avoid this,
When a non-reactive gas is flowed toward the inner surface of the window from the gas inlet 3, the gas flow makes it difficult for the reactive gas to approach the inner surface of the window, thereby reducing the adhesion of decomposed chemical species to the window. Become.

[Problem that the invention seeks to solve]

However, with this conventional method, it is difficult to completely prevent diffusion and the adhesion of decomposed chemical species to the window cannot be completely prevented. Furthermore, if an attempt is made to utilize a photoreaction in a reduced pressure atmosphere using a vacuum evacuation device, the introduction of non-reactive gas will place a burden on the evacuation device.

On the other hand, one possible method is to select a window material that prevents the decomposition species of the reactive gas from selectively adhering to the surface of the window. For example, considering that GeH4 is used as a reactive gas and a reaction is caused at an appropriate temperature, a phenomenon occurs in which Ge is not deposited on 5in2 when Sin is used as a window material. However, if 5iHn is used as the reactive gas,
Si is deposited on top of Sin.

As described above, there are systems in which windows are difficult to adhere to due to the combination of special window materials and reactive gases, but such cases are extremely rare. Especially the commonly used 5i02. A! too+
There are few reactive gases that do not deposit on window materials such as Sin,
The case of GeH4 can be said to be an exception.

[Means for Solving the Problems] In order to solve these problems, the present invention combines chemical species containing carbon and hydrogen or carbon and halogen on the surface of a window material for light irradiation. This is how it was done.

[Effect]

Decomposed chemical species are difficult to adhere to the surface of the window material for light irradiation of the present invention.

〔Example〕

The present invention can be applied to a window material for light irradiation such as Sin or A7! z O
The main feature is that the surface of the 's etc. is covered with a chemical species having a structure that prevents adsorption of gas and its decomposed chemical species. This point differs from conventional methods in which the window material is used exposed.

First, a first example will be described. Materials for light irradiation windows for normal light CVD, etc., include SiOz (including Pyrex, lead glass, etc.), Aj2203°MgO, etc.
Oxides such as are used. When such an oxide surface is treated with, for example, an aqueous or alcoholic solution of R-3t(OH)s, a structure as shown in FIG. 1 is obtained. Here R is an organic species. For example, when the surface 7 of a window material such as SiO
) i is adsorbed.

When this is taken out of the solution and heat treated at several tens to hundreds of degrees Celsius, a dehydration reaction occurs and a surface with R is obtained. This R-3i (OH), I is R-5i (OC
It can be easily obtained by hydrolyzing trialkoxysilanes such as R3)I and R-S i (OCzHs)s. Trialkoxysilanes that are relatively easily available include C+5)(at (OCgHs)3°CbHs
There are S 1 (OCzHs)z, etc. When a relatively large hydrocarbon is used as R to create a structure as shown in Figure 1 (C), the dipole moment of the surface decreases significantly and the surface energy decreases, causing gas molecules to form on the surface. Difficult to adhere to.

In this way, 3LO□ with a surface as shown in Figure 1(C)
, A° C., O, , MgO, etc., for the window material will reduce the amount of film deposited on the surface and will not prevent light irradiation.

What is important here is to completely cover the surface with relatively large hydrocarbon groups, and next we will discuss how to achieve this. For example, C1[lH3? -(OCzHs)
CtsHstS i (OH)3, which is obtained by hydrolyzing a, is
As shown in FIG. 2, it is divided into a hydrophilic silanol 8 and a hydrophobic alkyl group 9. For example, by putting this in water,
-Blodgett) [, as shown in Figure 3, it is possible to obtain a structure in which silanol groups 10 are attached to the surface 7 of the window material and alkyl groups 11 are oriented almost perpendicularly to the surface 7 of the window material. It will be done. When this is heat treated at tens to hundreds of degrees Celsius, R in Figure 1 becomes CI a H3? And completely cover the surface with C16H3? A structure covered with base can be realized.

Next, Langmuir Project (Langmutr-
A method that does not use the (Blodgett) method will be described.

When a window material substrate is immersed in an aqueous or alcoholic solution after being hydrolyzed into silanol using a substance having a chemical structure as shown in FIG. 4, it is adsorbed onto the surface of the substrate. This substrate is taken out and heat treated to react the silanol groups, resulting in a structure with long alkyl groups exposed on the surface as shown in FIG. 1(e).

Note that the R group exposed on the surface in Figure 1 (C1) does not necessarily have to be a saturated hydrocarbon and may have an unsaturated bond. It does not have to be only hydrocarbons, and may also contain nitrogen (N), oxygen (0), etc., as shown in the example in Figure 4.However, in this case,
The R group has a structure in which groups containing N and O do not appear on the surface side,
For example, as in the example in FIG. 4, -Cls Hs ?
It is better to have a structure in which large alkyl groups such as those bonded together can reduce the dipole moment effect of groups containing N, 0, etc., and is more effective in suppressing gas adsorption.

Next, a second embodiment will be described. In the first example, a case was shown in which a group mainly composed of hydrocarbons was used as the R group in FIG. Dipole moment can be reduced. At this time, it is better to use a single halogen or hydrogen rather than a mixture of various halogens or hydrogen groups. For example, as an R group -c+5)(st
The use of a group or the like is particularly effective because the dipole moment can be made small. As mentioned above, R in Fig. 1 [0)
Various chemical species can be used as the group, but it is necessary that the R group itself does not absorb the irradiated light and is not decomposed by absorbing the irradiated light. Therefore, the R group may be selected in consideration of the wavelength of the irradiated light.

Next, a method of using the light irradiation window material shown in Examples 1 and 2 will be explained. Groups such as hydrocarbons, halogenated hydrocarbons, and halogenated carbons as described in Examples 1 and 2 decompose when heated to several hundred degrees Celsius. Therefore, it may be necessary to take care not to increase the temperature of the inner surface of the window too much. To do this, for example, as shown in Figure 5, the window should have a two-layer structure,
A gap is opened between the inner window material 13 and the outer window material 14 of the reaction vessel 12, and a cooling fluid introduction pipe 15 is inserted into the gap.
and a discharge pipe 16 to allow cooling fluid 17 to flow into the gap. By configuring like this,
It becomes possible to prevent the inner surface of the inner window material 13 from becoming high temperature. However, in this case, it is necessary to select the fluid material depending on the wavelength of the light so that light absorption by the cooling fluid is reduced.

〔Effect of the invention〕

As explained above, the present invention can reduce the adsorption of reactive gases by bonding chemical species containing carbon and hydrogen or carbon and halogen to the surface of the window material for light irradiation. This reduces the amount of film deposited on the surface of the window material and lengthens the window cleaning or replacement cycle.
The effect is that it can be done.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the surface modification method using organic silanol used in the present invention, FIG. 2 is a structural diagram showing the chemical formula of octadecylsilanol used in the first embodiment of the present invention, and FIG.
The figure shows the Langmuir project.
Fig. 4 is a block diagram showing the structure of organic silanol adsorbed onto the surface of the window material by the method (Blodgett), and Fig. 4 is a block diagram showing the chemical formula of dimethyloctadecylaminopropyltriethoxysilane used in the first embodiment of the present invention. , 5th
The figure is an explanatory diagram for explaining an example of the method of using the window material for light irradiation according to the present invention, and FIG. 6 is an explanatory diagram for explaining the method of using the conventional window material for light irradiation. 7...! Window material surface, 8... Silanol group, 9...
...Alkyl group, 1o...Lyophilic group, 11...
Hydrophobic group, 12...Reaction vessel, 13...Inner window material, 14...Outer window material, 15...Cooling fluid introduction pipe, 16...Cooling fluid drainage pipe, 17.
...cooling fluid.

Claims (1)

[Claims] A window for light irradiation, characterized in that a chemical species containing carbon and hydrogen or carbon and halogen is bonded to the surface of the window material for light irradiation.