JPH07193003A - Vapor growth device and vapor growth method - Google Patents

Abstract

PURPOSE:To reduce the consumption of a raw material gas, and to obtain a compound semiconductor crystal having a uniform composition. CONSTITUTION:A reaction vessel 1, a periphery of which has a heater 4 and in which a raw material liquid 11 for vapor growth is housed on a bottom, a vessel cover 18 installed on the reaction vessel 1 and mounted on the side face of the reaction vessel 1 at a space section as an exhaust pipe 17, a substrate heating base 3, which is supported by the vessel cover 18 and downwards holds the substrate 2 and can be rotated, gas supply nozzles 5 supplying a raw material gas for vapor growth toward an upper section from the bottom of the vessel 1, and a pipe 14 supplying the liquid 11 with a carrier gas apart from the gas supply nozzles 5 are provided. A large number of pores 22 are formed in a space section among the heating base 3 and the nozzles 5, and a vapor growth device is composed of a gas diffusion member 23 feeding a gas flowed out from the nozzles 5 and the raw material ga;containing the raw material liquid 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase growth apparatus and a vapor phase growth method for a compound semiconductor crystal, particularly a compound semiconductor crystal of mercury cadmium tellurium (Hg _1-x Cd _x Te). The present invention relates to a vapor phase growth apparatus and a vapor phase growth method capable of reducing the consumption amount of the raw material gas to obtain a compound semiconductor crystal having a uniform composition.

[0002]

2. Description of the Related Art In a conventional vapor phase growth apparatus, as shown in FIG. 2 (a), a substrate 2 for vapor phase growth is placed on a substrate heating table 3 in a horizontal reaction vessel 1 and the reaction vessel Hg _1-x Cd _x in the reaction vessel 1 after the reaction vessel 1 is evacuated.
A raw material gas for vapor phase growth composed of hydrogen gas carrying dimethyl cadmium, diisopropyl tellurium and mercury gas for Te crystal growth is introduced, and the substrate 2 is heated by using the heater 4 and the like. There is a vapor phase growth method using a horizontal reaction vessel in which a source gas introduced onto a substrate 2 is decomposed by heating.

Alternatively, separately from this method, as shown in FIG. 2B, a substrate heating table 3 on which a substrate 2 is placed is installed in a vertical reaction vessel 1 and the inside of the reaction vessel 1 is evacuated. After that, substrate 2
There is a vapor phase growth method using a vertical reaction vessel in which the above-mentioned raw material gas is supplied in the vertical direction from above and the raw material gas supplied on the substrate 2 is decomposed by heating.

In any of the above-mentioned conventional methods, the flow rate of gas flowing into the reaction vessel 1 is increased so that the velocity of the gas does not change in the entire area of the substrate 2, that is, the flow of the gas is not disturbed. Is supplied to the substrate 2 in this state, and the substrate 2
Above, the raw material gas is supplied uniformly without any gas turbulence.

[0005]

However, when the source gas is supplied onto the substrate 2 at a high flow rate, the source gas passes through the substrate 2 at a high speed, so that the source gas is thermally decomposed on the substrate 2. There is a problem that the rate of growth as a vapor phase grown crystal, that is, the rate of growth of the crystal layer with respect to the gas supply amount decreases. That is, there is a drawback that the crystal yield, which is represented by the ratio of the number of moles of the supplied source gas to the number of moles of the vapor phase grown crystal layer, is as low as 1%.

Further, a ternary compound semiconductor crystal such as Hg _1-x Cd _x Te crystal is said to be a mixed crystal of HgTe crystal and CdTe crystal, and the formation energy of the above HgTe crystal and CdTe crystal is HgTe. Crystals are larger, and HgTe crystals are Cd at the same temperature.
There is a problem that it is harder to grow than Te crystals.

Therefore, in the case of FIG. 2 (a), a Hg _1-x Cd _x Te crystal containing a large amount of easily generated CdTe components, that is, a high x value, is formed on the gas inflow side of the substrate 2, On the gas outflow side of the substrate 2, Hg _1-x Cd _x Te crystals containing a large amount of HgTe components that are difficult to be generated, that is, having a small x value, tend to be formed, and have a uniform composition in the entire region of the substrate. That is, there is a problem in that Hg _1-x Cd _x Te crystals having a uniform x value are not formed.

Further, as shown in FIG. 2 (b), in the case where the vertical reaction vessel 1 is used for growth, if the number of the gas supply nozzles 5 is one, the temperature of the center of the substrate 2 is slightly higher than that of the periphery. Since it is high, Hg _1-x Cd _x Te crystals with a large amount of CdTe components, which are easily generated, grow, and Hg _1-x Cd _{x with} a large amount of HgTe components in the peripheral portion of the substrate 2.
Since the Te crystal grows, it is necessary to dispose many gas supply nozzles 5 for the source gas.

There is also a method in which HgTe crystals and CdTe crystals are alternately grown and the HgTe crystals and CdTe crystals are mutually diffused at the vapor growth temperature of both crystals. The above-mentioned crystal yield has a drawback that it is only as low as 1%.

The present invention solves the above-mentioned problems of the prior art. It requires only a small amount of raw material gas supply, a high crystal yield, and a uniform composition on the substrate, that is, the x value of the substrate is small. An object of the present invention is to provide a vapor phase growth apparatus and a vapor phase growth method capable of obtaining Hg _1-x Cd _x Te crystals that are uniform in the entire range.

[0011]

According to a first aspect of the present invention, there is provided a vapor phase growth apparatus, a reaction vessel having a heating means in the periphery thereof, and a bottom portion containing a raw material liquid for vapor phase growth, and the reaction vessel. It is installed on the upper part of the container, and is installed with a space portion serving as an exhaust pipe with respect to the upper side surface of the reaction container, and is supported by the container lid of the reaction container provided with a heating means, and the container lid of the reaction container, A substrate heating table that holds a substrate downward, a rotatable substrate heating table, a gas supply nozzle that faces the direction of the substrate above the bottom of the reaction vessel, and that discharges the source gas for vapor phase growth, and the gas. A carrier gas supply pipe for supplying a carrier gas to the raw material liquid for vapor phase growth separately from a supply nozzle, and having a large number of pores in the space between the substrate heating base and the gas supply nozzle, More outflow gas and the raw material liquid More comprising feed gas and loaded with a carrier gas a scan, the gas diffusion member that supplies by diffusing moved toward the substrate, is characterized in that disposed on the multilayer structure.

Further, as described in claim 2, the gas diffusion member is provided with means for enabling temperature control of the gas diffusion member. Further, as described in claim 3, the substrate is any one of cadmium tellurium, cadmium-zinc-tellurium, gallium arsenide, sapphire, and silicon, the raw material liquid is mercury, and the vapor-grown crystal on the substrate is 3 It is characterized by being a 2-6 group compound semiconductor containing mercury in a mixed crystal of one or more elements.

Further, as described in claim 4, the raw material liquid mercury is contained in a mercury reservoir provided at the bottom of the reaction vessel,
It is characterized in that a lid having pores is placed on the upper part of the mercury reservoir, and a carrier gas flowing out from a carrier gas pipe is blown onto the surface of the mercury.

According to a fifth aspect of the present invention, the cross-sectional area of the exhaust space between the substrate heating table and the inner wall of the reaction chamber is maintained at 1/5 or less of the area of the substrate heating table, and the inside of the reaction chamber is maintained. It is characterized in that the flow rates of the carrier gas and the raw material gas introduced into the tank are kept at 1 liter / min or less.

[0015]

In the vapor phase growth apparatus and vapor phase growth method of the present invention, the cross-sectional area of the exhaust space between the substrate heating table and the inner wall of the reaction vessel is reduced to 1/5 or less of the area of the substrate heating table. Keep
The flow rates of the carrier gas and the raw material gas introduced into the reaction vessel are kept at a low flow rate of 1 liter / minute or less.

Further, a large number of pores are provided between the substrate and the gas supply nozzle for the source gas, and a plurality of fluid or gas diffusion members whose temperature can be controlled by a heater are laminated in a structure. In this way, the supply flow rate of the source gas is made sufficiently small,
In addition, by arranging the gas diffusion members having pores between the substrate and the gas supply nozzle in a multi-layered structure, the source gas is supplied onto the substrate at an extremely gradual speed of about the diffusion movement of gas molecules. By doing so, the gas flow is supplied onto the substrate without any turbulence, so that the crystal yield of crystal growth is improved.

In addition, the HgTe crystal growth raw material gas (mercury gas and diisopropyl Te gas) and the CdTe crystal growth raw material gas (dimethyl Cd gas and diisopropyl Te gas) are simultaneously applied over the entire area of the substrate without any time lag. Will be supplied,
HgTe crystals and CdTe crystals having different generation energies grow in the same manner, and Hg _1-x Cd _x Te crystals having a uniform x value without composition fluctuation can be grown.

By arranging the diffusion member having a large number of pores in a multilayer structure, the number of gas supply nozzles can be reduced,
The source gas can be supplied uniformly to all areas of the substrate, and by keeping the distance between the gas diffusion plate and the gas supply nozzle 30 mm or less, the source gas becomes unstable between the substrate and the gas supply nozzle. It is also possible to prevent the occurrence of convection.

Further, in the conventional vertical vapor phase growth apparatus, the arrangement relationship between the substrate and the gas supply nozzle is reversed.
By providing the substrate in the upper part and the gas supply nozzle in the lower part, the raw material gas was supplied in the convection state on the substrate in the conventional apparatus, but the raw material gas is supplied in the diffused state. Since the supply state of the source gas to the substrate is stable, the composition of the crystals formed is stable.

Further, since the cross-sectional area of the exhaust space between the substrate heating table and the inner wall of the reaction vessel is kept to be 1/5 or less of the area of the substrate heating table, the amount of the supplied gas is reduced. It is possible to prevent the phenomenon that the composition of the crystals formed becomes unstable due to the increase in the amount.

The structure of the vapor phase growth apparatus equipped with the above diffusion plate is disclosed in Japanese Patent Laid-Open No. 62-92311. This diffusion plate prevents dust from falling on the surface of the vapor phase growth wafer. The purpose of this is to provide no pores.

Further, Japanese Patent Laid-Open No. 63-119229 also discloses a structure of a vapor phase growth apparatus equipped with a diffusion plate. This structure has a hollow interior between opposed substrate installation tables, A diffuser plate with an opening is placed so as to face the substrate installed on the installation table, and the mixed gas is flowed at a high speed inside the hollow diffuser plate so that the gas is sufficiently mixed inside the diffuser plate. It corresponds to the structure in which the substrate 2 is installed by further sandwiching the diffusion plate on the substrate 2 of the device having the structure of FIG. 2 (a), and there is no function of the diffusion plate as in the present application. .

[0023]

Embodiments of the present invention will be described in detail below with reference to the drawings. As shown in FIG. 1 (a), a heater 4 is provided around the periphery, and the bottom of a reaction vessel 1 made of cylindrical quartz with a narrowed bottom and an inner diameter of 100 mm is placed at the bottom of a source liquid mercury for vapor phase growth.
A mercury reservoir 12 containing 11 is provided, and a quartz lid 13 having pores is provided on the mercury reservoir 12.

Kyria gas supply pipe for spraying hydrogen gas as a carrier gas onto the mercury 11 contained in the mercury reservoir 12
14 is arranged so as to penetrate the bottom of the reaction vessel 1 and weld to the reaction vessel 1 to maintain an airtight structure and direct the supply port on the mercury 11.

A raw material gas supply pipe 15 for supplying a raw material gas composed of dimethylcadmium gas supported on hydrogen gas and diisopropyl tellurium gas in parallel with the carrier gas supply pipe 14 penetrates the bottom of the reaction vessel 1. Then, it is introduced into the reaction container 1, and its tip part is branched into a plurality of
The gas supply nozzle 5 is arranged toward the upper side of the reaction vessel 1.

A container lid 18 of the reaction container provided with a heater 4 is provided above the reaction container 1 with a space in which an exhaust pipe 17 for exhausting the gas after vapor phase growth can be formed toward the side surface. And a rotatable shaft 19 is installed on the container lid 18, and a rotatable substrate heating base 3 made of carbon and having a diameter of 90 mm is installed on the shaft 19.

A substrate 2 of gallium arsenide or the like for vapor phase growth is installed on the substrate heating table 3 so as to be embedded in a downward direction. And by keeping the distance d between the substrate heating table 3 and the inner wall of the reaction vessel 1 to 5 mm or less,
The ratio of the cross-sectional area of the exhaust space between the inner wall of the reaction vessel 1 and the substrate heating table 3 to the circular area of the upper surface of the substrate heating table 3 is set to be within 1/5 or less. By doing so, the source gas supplied from the gas supply nozzle 5 and the gas carrying mercury among the gases in the carrier gas supply pipe 14 move toward the substrate heating table 3 at a slow speed.

In the space between the substrate heating table 3 and the plurality of gas supply nozzles 5, a large number of pores 22 are provided, and dimethyl Cd and diisopropyl Te flowing out from the gas supply nozzle 5 are discharged.
The gas diffusion member 23 for diffusing and supplying the raw material gas and the carrier gas carrying the raw material liquid mercury gas to the substrate 2 side is provided in a multilayer structure.

As shown in FIG. 1 (b), the structure of the gas diffusion member 23 is made of quartz and is a gas pipe through which heated nitrogen gas whose temperature can be controlled or liquid nitrogen gas for cooling can flow. A large number of 24 are provided, and the periphery of this gas pipe 24
A structure surrounded by a quartz plate 25 having is adopted. This pore
The diameter of 22 is 5 mm or less, and the intervals of the pores 22 are 10 mm or less.

The distance between the substrate 2 and the uppermost gas diffusion member 23 is 10 mm, and the distance between the quartz plates 25 is 10 mm. According to such a vapor phase growth apparatus of the present invention, the total flow rate of gas is 1 from the gas supply nozzle 5 and the carrier gas supply pipe 14.
Introduced into the reaction vessel 1 at a minute flow rate of less than 1 liter / minute, the distance d between the substrate heating table 3 and the inner wall of the reaction vessel 1
Is maintained at 5 mm or less so that the ratio of the cross-sectional area of the exhaust space between the inner wall of the reaction vessel 1 and the substrate heating table 3 to the circular area of the upper surface of the substrate heating table 3 is 1/5 or less. The raw material gas introduced into the reaction vessel reaches the substrate 2 at a slow speed because it is set within the range.

A gas diffusion member 23 having pores 22 is arranged in a multi-layer structure between the substrate 2 and the gas supply nozzle 5, and the gas diffusion member 23 keeps the gas diffusion speed at a predetermined speed. Therefore, the source gas introduced into the reaction vessel 1 flows on the substrate 2 at a slow speed, and reaches the substrate 2 in a state where gas diffusion is more dominant than the gas flow.

Using such a vapor phase growth apparatus of the present invention,
The method for vapor phase growth of Hg _1-x Cd _x Te crystal on GaAs substrate is described. The GaAs substrate 2 having a diameter of 3 inches is placed on the substrate heating table 3, the inside of the reaction vessel 1 is sufficiently replaced with hydrogen gas, and then the partial pressures of dimethyl Cd gas and diisopropyl Te gas in the hydrogen gas are each 10 ^−4. 0.5 liter of the raw material gas supported so as to reach atmospheric pressure is fed into the reaction vessel 1 through the raw material gas supply pipe 15.
Flow at a gas flow rate of / min.

Then, the GaAs substrate 2 is heated to a temperature of 410 ° C., the substrate 2 is rotated at a rate of 6 revolutions / minute, and a CdTe layer is formed on the substrate 2 as a buffer layer having a thickness of 3 μm. Form a film.

Next, the GaAs substrate 2 is lowered to a temperature of 360 ° C., the substrate 2 is rotated at a rate of 6 revolutions / minute, and a partial pressure of dimethyl Cd gas and diisopropyl Te gas is added to hydrogen gas from a source gas supply pipe 15. Of the source gas supported so that each becomes 10 ^-4 atm, and the hydrogen gas sprayed on the mercury 11 from the carrier gas supply pipe 14 so that the mercury partial pressure becomes 1 × 10 ^-2 atm. The gas is introduced into the reaction vessel 1 so that the total flow rate is 0.5 liter / min.

The heater 4 provided on the reaction vessel 1 and the vessel lid 18 heats to a temperature of 220 ° C., and the temperature of the gas diffusion member 23 is also kept at 220 ° C. The total of the value obtained by converting the crystal layer of the Hg _1-x Cd _x Te crystal formed on the GaAs substrate 2 into the number of moles and the raw material gas in which dimethyl Cd gas, diisopropyl Te gas and mercury used were mixed Calculating the ratio of the average number of moles and examining the yield of Hg _1-x Cd _x Te crystals with respect to the consumed raw material gas, a value of about 30% was obtained, which is significantly higher than that of conventional equipment. Yield improved.

Further, the variation of the x value of the Hg _1-x Cd _x Te crystal formed on the GaAs substrate is Δx <0.005, which is significantly larger than the variation of the x value in the conventional device of Δx = 0.02. It was found that the x values were uniform.

Although the GaAs substrate is used as the substrate in the above-described embodiments, a semiconductor substrate such as Si, CdT, etc. may be used in addition to the GaAs substrate.
A compound semiconductor substrate such as e or CdZnTe substrate or an insulating substrate such as sapphire may be used.

Further, the compound semiconductor crystal that grows in the vapor phase is Hg.
Besides the _1-x Cd _x Te crystal, a ternary or higher compound semiconductor crystal such as a CdZnTe crystal may be used.

[0039]

As described above, according to the vapor phase growth apparatus and the vapor phase growth method of the present invention, even a compound semiconductor crystal of a mixed crystal having different generation energies has a uniform composition and a large area. Crystals can be obtained and the consumption of raw material gas can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a vapor phase growth apparatus of the present invention and a cross-sectional view of a main part of the apparatus.

FIG. 2 is an explanatory diagram of a conventional vapor phase growth apparatus.

[Explanation of symbols] 1 Reaction container 2 Substrate 3 Substrate heating base 4 Heater 5 Gas supply nozzle 11 Raw material liquid (mercury) 12 Mercury reservoir 13 Quartz lid 14 Carrier gas supply pipe 15 Raw material gas supply pipe 17 Exhaust pipe 18 Vessel lid 19 Shaft 22 Pores 23 Gas diffusion member 24 Gas pipe 25 Quartz plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Okamoto 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (5)

[Claims] 1. A reaction vessel (1) having a heating means (4) on the periphery thereof and containing a raw material liquid (11) for vapor phase growth at the bottom, and the reaction vessel (1) installed at the top of the reaction vessel (1), A container lid (18) for the reaction container (1), which is installed on the upper side surface of the reaction container (1) with a space serving as an exhaust pipe (17), and is equipped with heating means (4).
A substrate heating table (3) that is supported by the container lid (18) and holds the substrate (2) downward, and is rotatable, and a substrate (2) above the bottom of the reaction container (1). A gas supply nozzle (5) for supplying a source gas for vapor phase growth facing each other in the direction of, and a carrier for supplying a carrier gas to the source liquid for vapor phase growth separately from the gas supply nozzle (5) A gas supply pipe (14), a large number of pores (22) in the space between the substrate heating table (3) and the gas supply nozzle (5), and flow out from the gas supply nozzle (5). The gas diffusion member (23) is arranged in a multi-layered structure in which the gas to be supplied and the source gas made of a carrier gas carrying the source liquid (11) are diffused and moved to the substrate (2) side. Vapor growth equipment. 2. A temperature control means for enabling the temperature control of the gas diffusion member (23) according to claim 1.
A vapor phase growth apparatus characterized in that (24) is provided. 3. The substrate (2) according to claim 1, which is any one of cadmium tellurium, cadmium-zinc-tellurium, gallium arsenide, sapphire, and silicon, and the raw material liquid is mercury. A vapor phase growth apparatus, wherein the crystal to be phase-grown is a mixed crystal of three or more elements and is a 2-6 group compound semiconductor containing mercury. 4. The raw material liquid (11) according to claim 1 is mercury, and the mercury reservoir (1) is provided at the bottom of the reaction vessel (1) or at the bottom.
2), and a lid (1
3. A vapor phase growth apparatus having a structure in which 3) is arranged and a carrier gas flowing out from a carrier gas supply pipe (14) is blown onto the surface of the raw material liquid (11). 5. The cross-sectional area of the exhaust space between the substrate heating table (3) according to claim 1 and the inner wall of the reaction vessel (1) is set to 1/5 or less of the area of the substrate heating table (3). A vapor phase growth method characterized in that the flow rate of the raw material gas introduced into the reaction vessel (1) is maintained at 1 liter / min or less.