JPS6210274A - Method and device for vapor phase synthesis - Google Patents

Abstract

PURPOSE:To prevent the generation of a crack of spherical crystal by separating a substrate from the synthesized crystal before the cooling of a furnace wherein the vapor phase synthesis has been finished. CONSTITUTION:Crystal such as ZnS is synthesized on the surfaces of an outer frame part 1d of a substrate and the spherical substrates 1a-1c by introducing H2S or the like through a nozzle 6 and introducing vapor of Zn or the like through a nozzle 7. At a point of time wherein this synthesis has been finished, the spherical substrates 1a-1c are drawn out to a heater 3 side by operating a substrate drawing-out rods 2a-2c. Thereby the spherical substrates 1a-1c and the synthesized crystal 9 are separated before the cooling of a furnace 4. In such a way, the formation of a crack and the generation of a crazing of synthesized crystal 9 can be prevented in a spherical relief part of the substrate concentrated with the stress by separating both the synthesized crystal 9 and the spherical substrates 1a-1c which are different in the thermal expansion coefficient.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for vapor phase synthesis of polycrystalline materials (Chemical V
apour Deposition Method,
Regarding the CVD method and the apparatus, in particular, polycrystalline materials having a spherical shape, such as Zn5e, Zn8, Z
n131-XSe, , CaS, CaTe.

The present invention relates to a novel method and apparatus for stably synthesizing ZnTe, 81, GaAs, etc. without causing cracks or the like.

(Prior art) Polycrystals such as Zn5e and ZnS are used as window materials for lasers or detectors, and there is no problem when the shape is a flat plate, but when it is spherical, that is, has a curved shape of 4R0 and a depth h'2. CVD is the most excellent method in terms of raw material yield and control of crystal grain size.In this method, the entire substrate with a shape of curvature R9 depth h as shown in FIG. 10 is prepared (relief), and a target substance is deposited on the substrate by vapor phase synthesis.

(Problems to be Solved by the Invention) However, when a spherical polycrystalline body is produced by the CVD method, RK is produced at an inappropriate location on the entire spherical relief substrate. When a spherical surface is reliefed onto a single substrate, cranks tend to occur in the synthesized spherical polycrystalline material.

This is thought to be due to the thermal stress caused by the difference in thermal expansion coefficient between the substrate and the synthesized crystal during cooling of the furnace, and stress concentration occurs in a certain part of the crystal. Further, stress concentration occurs in the area indicated by the arrow in FIG. 4 mainly due to the shape of the substrate.

An object of the present invention is to provide a novel vapor phase synthesis method and apparatus that does not cause cracks in spherical crystals.

(Means for solving the problem) Thermal stress and stress concentration that cause cracks occur during cooling of the furnace, as described above. Therefore, as a result of research based on the idea that thermal stress and stress concentration can be prevented by separating the substrate and the synthetic crystal before cooling the furnace, the present invention has been arrived at.

That is, the present invention provides a method for vapor phase synthesis of crystals by supplying raw material gas onto a spherical substrate, which is characterized in that the substrate is separated from the synthesized crystals after completion of synthesis and before cooling of the furnace. A first invention relating to a method, and an outer frame for supporting a plurality of spherical substrates in a vapor phase synthesis apparatus comprising a means for supplying raw material waste onto a spherical substrate and a means for maintaining all synthesis reaction conditions as an apparatus used in the method. The second invention comprises a vapor phase synthesis apparatus characterized by a substrate, a means for moving the spherical substrate to the rear of the entire outer frame substrate in order to separate the spherical substrate from the crystal, and a tV.

(Operation) The method and apparatus of the present invention will be specifically explained below with reference to the drawings.

FIG. 1 shows one embodiment of the method and apparatus of the invention, comprising:
Reference numeral 14 denotes an outer frame portion of the substrate 1, and nine spherical relief substrates ta, 1b, and I are fitted into the outer frame portion 1dK.
c can be individually pulled out to the heater s side using substrate pull-out rods 2a, 2b, and 2c. Note that the M2 figure is a cross-sectional view of the board part, and the fjlc6 figure is a front view. In FIG. 4, the spherical substrate 1ei is integrated and can be separated from the substrate outer frame portion 1d at one time. This is a modification of Fig. 2. 4
5 is a furnace body, 5a, b, c are 7 lunges, 6 and 7 are reactive gas introduction nozzles, 8 is a substrate pedestal, for example, nozzle 6
Zn vapor is introduced from the H2S i nozzle 7, and ZnS is applied to the outer frame portion 1d of the substrate and the surfaces of the spherical substrates ta, 1b, and 1c.
Complete crystal synthesis. When the synthesis is completed, the spherical substrate 1a,
Ib and 1c are pulled out to the heater 3 side, and the spherical substrate 1a is
, 1b, 1c and the synthetic crystal 9 fixed to the outer frame of the substrate are separated before the furnace 4 is cooled. In order to separate the synthesized crystal 9 from the spherical substrates 1a, 1b, 10 having different thermal expansion coefficients in the spherical relief portion of the substrate 1 where stress is thought to be concentrated on these L points, the synthesized crystal 9 is separated. Cracks can be prevented from forming.

(Example) It has the structure shown in Figures 2 and 6, and the length of the spherical part is 80 mm.
Using a substrate having a hemispherical relief with w and h of 80ffil+, the configuration shown in Fig. 1 was fabricated, and a spherical ZnS crystal i
It was synthesized using the CVD method. Note that carbon was used as the spherical substrate material.

The temperature of the furnace was kept at 750℃, and the raw material mixed gas was 2.4 N.
t/min, carrier gas f 1.6 Nt/min
Then, crystal synthesis was carried out for 250 to 300 hours.

Next, immediately after the reaction when the furnace temperature was 750° C. to 700° C., the iIs was pulled out and separated automatically or manually to obtain crystalline gold with a thickness of 10 days or more.

There are no cracks or breaks in the crystal.

The thermal expansion coefficients of ZnS and carbon are as follows.

ZnS 7.85 x 10-'/℃ Carbon 1.8-5 x 10''/1: For comparison, when crystal synthesis is performed under similar conditions using the conventional substrate shown in A crack occurred across the center of the crystals deposited on the spherical surface.

(Effects of the Invention) In the method of the present invention, after the completion of the gas phase synthesis reaction, the crystal produced under the pre-cooling pressure of the furnace is separated from the spherical substrate. This has the effect of preventing cracks and cracks caused by the position and shape of the relief on the substrate. However, the apparatus of the present invention is an apparatus that can stably produce crack-free substrates because the above-mentioned crystal and spherical substrate can be easily separated by simply operating the pull-out rod from outside the furnace. The method and apparatus of the present invention include:
It is particularly advantageous in vapor phase synthesis of crystals on spherical substrates having spherical relief.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining an embodiment of the method and apparatus of the present invention, FIGS. 2 and 3 show embodiments of the substrate in the present invention, FIG. 2 is a cross-sectional view, and FIG. 3 is a front view. , FIG. 4 is a modified view of the integrated spherical substrate of FIG. 2, and FIG. 5 is a cross-sectional view of the conventional substrate.

Claims (2)

[Claims] (1) A method for vapor phase synthesis of crystals by supplying raw material gas onto a spherical substrate, characterized in that the substrate is separated from the synthesized crystals after completion of synthesis and before cooling of the furnace. . (2) In a gas phase synthesis apparatus comprising means for supplying raw material gas onto a spherical substrate and means for maintaining synthesis reaction conditions,
A vapor phase synthesis apparatus comprising: an outer frame substrate supporting a plurality of spherical substrates; and means for moving the spherical substrates to the rear of the outer frame substrate in order to separate the spherical substrates from the crystal.