JPH02215135A - Vapor phase epitaxy device - Google Patents

Abstract

PURPOSE:To prevent any evaporated gas of an easily evaporative raw liquid from being led in a reaction tube without fixing a valve by a method wherein a raw gas liquefying means is provided to flow back the liquefied raw gas to the liquefying means. CONSTITUTION:A cooling apparatus such as Peltier element or Joule Thomson type cooler (cooling liquefying means) 12 is provided between a raw liquid evaporating means 111 such as a mercury evaporator, etc., and a reaction tube 3 to that mercury of a carrier gas containing mercury may be cooled down and liquefied to be flowed back from a mercury reservoir 13 to the means 11. Through these procedures, any evaporated gas of the material solution such as easily evaporative mercury solution, etc., can be prevented from being led in the reaction tube 3 without fixing a valve at all and after forming a epitaxial layer such as Hg1-xCdx Te, etc., on a substrate, the epitaxial layers, etc., containing no mercury can be continuously formed laminatedly.

Description

[Detailed Description of the Invention] [Summary] Regarding a vapor phase epitaxial growth apparatus, an apparatus that can easily obtain an epitaxial layer in which an epitaxial layer containing easily evaporable mercury and an epitaxial layer not containing mercury are laminated is provided. For the purpose, a susceptor with a substrate for epitaxial growth installed is installed in a reaction tube, a source gas obtained by vaporizing the source liquid of the epitaxial growth gas is introduced onto the substrate, the substrate is heated, the source gas is thermally decomposed, and the source gas is thermally decomposed onto the substrate. In an apparatus for forming an epitaxial layer on a liquid, the vaporized raw material gas is cooled and liquefied between a means for vaporizing the raw material liquid and a reaction tube, and the liquefied gas is used for gasifying the raw material liquid. A means for refluxing the evaporator is provided.

[Industrial application field]

The present invention relates to a vapor phase epitaxial growth apparatus.

Mercury, cadmium, tellurium (Hgl-x c
A compound semiconductor crystal made of TiXTe) is used.

When epitaxially growing such a crystal of Hgt-y cct
A raw material gas such as dimethyl cadmium (Cd(CIj)z) or diethyltellurium (Te(CtHs)z) is introduced together with hydrogen gas as a carrier gas, and the susceptor on which the substrate is installed is heated to form a gas in the reaction tube. The introduced raw material gas is decomposed and Hgt-x Cdg Te is deposited on the substrate.
A method of epitaxially growing crystals has been adopted.

This type of vapor phase growth method is called MOCVD method (MetalO
rganic Chemical Vapor Dep
position: metalorganic vapor phase growth method).

[Conventional technology]

Such a conventional vapor phase epitaxial growth apparatus will be explained with reference to FIG.

As shown in the figure, a gas introduction pipe 4 connected to a reaction tube 3 containing a susceptor 2 on which a substrate 1 for epitaxial growth such as CdTe is installed is branched, and one gas introduction pipe 4A is connected to a mercury evaporator 6 containing mercury 4. The other connected and branched gas introduction pipe 4B is connected to an evaporator containing dimethyl cadmium and diethyl tellurium (not shown).

Then, hydrogen gas Ob) as a carrier gas is introduced into these mercury evaporator 6, dimethyl cadmium evaporator, and diethyl tellurium evaporator, hydrogen gas carrying mercury, hydrogen gas carrying diethyl tellurium, and dimethyl Hydrogen gas carrying cadmium is introduced into the reaction tube 3 through the gas introduction tubes 4A and 4B, and the susceptor 2 is heated by energizing the high frequency induction coil 6 around the reaction tube 3. The substrate 1 is heated and epitaxial growth gases such as mercury gas, dimethyl cadmium gas, and diethyl tellurium gas that have reached the substrate 1 are thermally decomposed to form an epitaxial layer of t1g+-x CdxTe on the substrate, and to participate in this epitaxial growth. The gas consisting of is discharged to the outside through the flange 10 of the reaction tube.

[Problems to be Solved by the Invention] By the way, in order to make the composition of the epitaxial layer formed uniform in the reaction tube, it is necessary to introduce a carrier gas with a certain concentration of raw material gas, for example, mercury. A hydrogen carrier gas is introduced into the evaporator 6, the mercury is bubbled with the hydrogen gas, the space 6A of the evaporator 6 is filled with saturated mercury vapor, and the saturated mercury is used as a carrier. Gaseous hydrogen is introduced into the reaction tube.

In order to obtain such saturated mercury vapor, the mercury must be
Mercury is heated to 50°C to have a saturated vapor pressure,
Therefore, a heater 8 is installed around the mercury evaporator 6 to maintain the temperature of mercury at 250°C, and a heater 8 is installed around the gas inlet pipe 4A connected to the mercury evaporator 6 and the gas inlet side of the reaction tube. A heater 9 is installed to raise the temperature of the gas introduction tube wall of the gas introduction tube 4A and the reaction tube 3 so that the introduced mercury vapor does not solidify and adhere to the tube wall.

By the way, using the above-mentioned apparatus, Hg was deposited on a CdTe substrate.
The need to stack an epitaxial layer of t-x Cdx Te and an epitaxial layer of mercury-free CdTe may arise depending on the type of sensing element to be formed.

Therefore, an attempt was made to provide a pulp between the mercury evaporator 6 and the gas introduction tube 4A and close this pulp to form a device that would prevent the mercury 5 in the mercury evaporator 6 from being introduced into the reaction tube. Since the gas introduction pipe 4A is heated by the heater 9, there is no resin pulp that can withstand this high temperature, and if metal pulp is used, the mercury flowing through the gas introduction pipe and the metal will chemically react. This is not preferred because mercury amalgam is formed and its components are introduced into the reaction tube.

The present invention solves the above-mentioned problems and aims to provide a vapor phase epitaxial growth apparatus which does not use the above-mentioned pulp and prevents the vaporized gas of the easily evaporable raw material liquid from being introduced into the reaction tube.

[Means to solve the problem]

As shown in FIG. 1, the vapor phase epitaxial growth apparatus of the present invention is provided with means 12 for cooling and liquefying the vaporized raw material gas between a means IT for vaporizing the raw material liquid and a reaction tube 3. It is constructed by providing means for refluxing the gas to the vaporizing means 11 for the raw material liquid.

(Function) In the apparatus of the present invention, a cooling device 12 such as a Bertier element or a Joule-Thomson type cooler is installed in the middle of a passage through which a carrier gas carrying easily evaporable mercury is introduced into a reaction tube, and the mercury is The mercury contained in the carrier gas is cooled and liquefied by this device, and a mercury reservoir 13 is provided to store the liquefied mercury, and the mercury collected from this mercury reservoir 13 is returned to the inside of the mercury evaporator 11 of the raw material liquid vaporization means. let

In this way, it is possible to easily stop the introduction of mercury vapor into the reaction tube without using resin or metal valves that have poor heat resistance or easily form mercury amalgam. , Hg+-x C on the substrate
After forming the epitaxial layer of dXTe, it becomes possible to continuously form an epitaxial layer of CdTe that does not contain mercury thereon.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing the main parts of the epitaxial growth apparatus of the present invention, and FIG. 2 is a detailed view of the main parts of FIG. 1.

As shown in FIGS. 1 and 2, in the apparatus of the present invention, a Vertier element or a Joule-Thomson type cooling element 12 is provided in the gas introduction tube 4A in the path between the mercury evaporator 11 and the reaction tube 3. The opposing portions of this element are filled with a heat insulating material 14, and between the heat insulating material 140, a serpentine pipe 4C structure is formed in order to improve the heat transfer of the gas introduction pipe 4A. Mercury reservoir 13 that temporarily stores mercury
will be established.

A case will be described in which an epitaxial layer of gl-x Cdx To is formed on a CdTe epitaxial growth substrate using such an apparatus, and then a CdTe epitaxial layer is formed thereon.

First, set the gas flow rate to the mercury evaporator to 0.31/lll1.
By setting the heating temperature of the mercury evaporator 11 to 270'C, the mercury partial pressure in the carrier gas derived from the mercury evaporator becomes 0.16 at-, and in this state, the above-mentioned dimethyl cadmium and diethyl tellurium Hg+-x is introduced into the reaction tube 3 together with hydrogen gas supporting Hg+-x
Form an epitaxial layer of CdxTe.

Next, actuate the cooling element such as the Bertier element 12,
The temperature inside the corrugated pipe 4C near the cooling element is maintained at -35°C.

Then, since the melting point of mercury is -38°C, most of the mercury gas becomes a liquid, and the mercury partial pressure in the carrier gas in this case becomes 5.8 XIO"'atn+, which can block mercury. The Vertier element 12 liquefies the mercury-containing gas rising along the flexible tube 4C, and prevents the mercury-containing gas from being introduced into the reaction tube 3.

In this state, only dimethyl tellurium and hydrogen gas carrying dimethyl cadmium are introduced into the reaction tube, so a mercury-free CdTe epitaxial layer is formed on the Hg+-x CdXTe epitaxial layer. Ru.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to obtain a vapor phase epitaxial growth apparatus in which epitaxial layers of Hg+-m Cdx To and CdTe are easily laminated and formed on a substrate. It is highly effective when used in the production of forming materials.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the essential parts of an embodiment of the apparatus of the present invention, FIG. 2 is a detailed diagram of the essential parts of FIG. 1, and FIG. 3 is an explanatory diagram of a conventional vapor phase growth apparatus. In the figure, 3 is a reaction tube, 4A is a gas introduction tube, 4C is a flexible tube, 11 is a raw material liquid vaporization means (mercury evaporator), 12 is a cooling liquefaction means (Peltier element), 13 is a mercury reservoir, and 14 is a heat insulating material. . Diagram Ortoki mark. Sugi 4th figure 2m

Claims (1)

[Claims] A susceptor (
2) is installed in a reaction tube (3), and a raw material gas obtained by vaporizing a raw material liquid of an epitaxial growth gas is introduced onto the substrate,
In the apparatus for forming an epitaxial layer on the substrate by heating the substrate and thermally decomposing the raw material gas, the vaporized raw material gas is disposed between the raw material liquid vaporization means (11) and the reaction tube (3). Means for cooling and liquefying (12
), and the liquefied gas is transferred to the raw material liquid vaporization means (
11) A vapor phase epitaxial growth apparatus characterized in that the reflux is performed.