JP2671367B2 - Vapor phase epitaxial growth equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] A vapor phase epitaxial growth apparatus for a compound semiconductor containing mercury, which aims to realize a vapor phase epitaxial growth apparatus that does not require heating of a carrier gas carrying mercury. And a carrier gas containing epitaxial growth gas are introduced into the reaction tube through a gas introduction tube, and the substrate on the susceptor housed in the reaction tube is heated to contain the carrier gas containing mercury and the epitaxial growth gas. A device for growing an epitaxial crystal of a compound semiconductor containing mercury on a substrate by reacting with a carrier gas, wherein the gas introducing pipe is connected to a cylinder having a heat insulating piston and the gas introducing pipe is connected to an outlet of the cylinder. A heat-insulating pressure vessel equipped with a shutter and containing mercury is attached to the inside of the pressure vessel. Containers mercury formed into particulate droplets by adiabatic expansion due to the operation of the piston and the shutter configured to disperse mixed with the carrier gas.

[Industrial applications]

The present invention relates to a vapor phase epitaxial growth apparatus. A compound semiconductor crystal such as mercury, cadmium, tellurium (Hg _1-X Cd _X Te) having a narrow energy band gap is used as a material for forming a photoelectric conversion element such as an infrared detection element.

To form such a compound semiconductor crystal in a large area and in a thin film state, which is convenient for device formation, a carrier gas is placed on a compound semiconductor substrate such as cadmium tellurium (CdTe) housed in a reaction tube. As a carrier gas and mercury carried on hydrogen gas as dimethyl cadmium,
An epitaxial growth gas such as diethyl tellurium is carried and introduced, the substrate is heated to decompose the epitaxial growth gas, and the decomposed line segment is deposited on the substrate.
The MOCVD (Metal Organic Chemical Vapor Deposition) method is used.

[Conventional technology]

The conventional vapor phase epitaxial growth apparatus will be described.

FIG. 4 is an explanatory view schematically showing a conventional vapor phase epitaxial growth apparatus. As shown in the figure, a graphite susceptor 3 on which a CdTe substrate 2 is arranged is installed in a reaction tube 1 made of quartz, and a reaction is performed. A high frequency induction coil 4 for heating the susceptor 3 is installed around the tube 1.

Further, the gas introduction pipe 5 connected to the reaction pipe 1 is branched in three directions. Hydrogen gas carrying dimethyl cadmium gas from the branched gas introduction pipe 5A, hydrogen gas carrying diethyl tellurium gas from the gas introduction pipe 5B, gas introduction pipe Hydrogen gas carrying mercury from 5 C is introduced into each reaction tube 1.

A cap 6 is provided on the gas outflow side of the reaction tube 1, and a gas exhaust pipe 7 is provided through the cap 6.

Using such a device, mercury, cadmium,
In the case of growing tellurium crystals, after exhausting the inside of the reaction tube 1 once, hydrogen gas carrying dimethyl cadmium gas, hydrogen gas carrying diethyl tellurium gas, and mercury are gasified from the gas introduction tubes 5A, 5B, 5C. The carried hydrogen gas is introduced into the reaction tube 1, and high-frequency power is applied to the high-frequency induction coil 4 to heat the susceptor 3, thereby reacting the gas introduced into the reaction tube 1 and mercury on the substrate 2.・ Forms an epitaxial phase of cadmium tellurium.

[Problems to be solved by the invention]

By the way, the hydrogen gas carrying the gaseous mercury is the reaction tube 1
When the tube walls of the gas and the gas inlet tubes 5 and 5C are cold, mercury vapor is cooled by the cold tube walls and easily condenses, which is necessary for epitaxial growth of mercury, cadmium, and tellurium crystals. A large amount of mercury cannot be transported into the reaction tube 1.

Therefore, as shown in FIG. 4, the heater 8 is provided on the wall of the reaction tube 1 on the gas introduction side of the susceptor 3 and the gas introduction tube 5C of the carrier gas carrying mercury in a gaseous state, and the heater 8 is heated. This prevents mercury vapor from condensing and prevents mercury from adhering to the tube wall.

Further, as shown in FIG. 5, mercury 9 is accommodated, a carrier gas of hydrogen gas is introduced to bubble the mercury 9 in the container, and the mercury is gasified and mixed with the carrier gas into the reaction tube 1. A heater 11 is also provided around the evaporator 10 to be introduced.

However, the heater 8 around the gas introduction pipe 5C as shown in FIG. 4 and the heater 8 provided on the gas introduction side of the susceptor 3 of the reaction tube 1 are heated at a temperature of about 250 ° C. Therefore, this heater is used. There is a fear that the epitaxial growth gas such as dimethylcadmium gas or diethyl tellurium gas introduced into the gas introduction pipe 5 and the reaction pipe 1 not branched by the heating of 8 may be decomposed before reaching the substrate 2. There is a problem that an epitaxial layer having a desired composition cannot be formed on the substrate 2.

An object of the present invention is to solve the above problems and provide a vapor phase epitaxial growth apparatus that does not require heating of a reaction tube or a gas introduction tube.

[Means for solving the problem]

In the vapor phase epitaxial growth apparatus of the present invention to achieve the above object, a carrier gas containing mercury and a carrier gas containing an epitaxial growth gas are introduced into a reaction tube through a gas introduction tube, and a substrate on a susceptor housed in the reaction tube. Is an apparatus for growing an epitaxial crystal of a compound semiconductor containing mercury on a substrate by heating a carrier gas containing mercury and a carrier gas containing an epitaxial growth gas by heating the gas introducing pipe, A cylinder having a piston and a shutter connected to a gas introduction pipe at the exit of the cylinder are attached, and a heat-insulating pressurized container containing mercury is attached, and the mercury contained in the pressurized container is insulated by operating the piston and the shutter. By expansion, fine droplets are formed and dispersed and mixed in the carrier gas.

Further, a means for applying an electric charge to the mercury dispersed in the carrier gas as the fine particle droplets is provided, and a gas introduction pipe through which the carrier gas containing the mercury flows and a reaction pipe on the gas inflow side of the susceptor Is provided with an electrode for charging the inner wall of the battery with the same polarity as the charge applied to the mercury.

(Operation)

Gaseous mercury, which has been bubbled by introducing a carrier gas such as hydrogen gas into an evaporator that contains mercury, condenses and liquefies when it comes into contact with the low-temperature gas introduction pipe or the wall surface of the low-temperature region in the reaction pipe. The partial pressure of mercury in the carrier gas at this time becomes equal to the saturated vapor pressure of mercury determined by the temperature of the wall surface.
Since this pressure is considerably lower than the partial pressure of the initially gasified mercury, it is not possible to transport a predetermined amount of mercury.

However, when mercury is dispersed in a carrier gas in the form of droplets by adiabatic expansion and transported, even if the droplets come into contact with a low temperature wall surface such as a gas inlet pipe or a reaction pipe, There is no change in the mercury partial pressure of the gas. Since the temperature of the carrier gas and the temperature of the wall surface are equal, the mercury partial pressure is equal to the saturated vapor pressure at these temperatures, and since mercury is already present in the carrier gas in the form of droplets, this state remains.

Therefore, a large amount of mercury droplets are present in the carrier gas, and the required amount of mercury can be transported.

Further, by negatively charging the mercury droplets formed into fine particles, and by keeping the inner wall of the gas introduction tube or the reaction tube at the same potential as the charging potential, the droplets are allowed to adhere to the inner wall. It can be prevented from completely adhering.

That is, when the liquid droplets try to approach the inner wall surface of the gas introduction tube or the reaction tube, the liquid droplets cannot reach the inner wall surface due to the repulsion action due to the electromagnetic force, and a predetermined amount of mercury is placed on the susceptor. It can be reliably transported onto the substrate, and an epitaxial layer having a desired composition can be obtained.

〔Example〕

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

FIG. 1 is the first of the vapor phase epitaxial growth apparatus of the present invention.
It is explanatory drawing of an Example and the same code | symbol is attached | subjected to the part which has a function equivalent to FIG.

In the present embodiment, as shown in the figure, in the middle of the gas introduction pipe 5C through which a carrier gas composed of hydrogen gas carrying mercury is circulated, a heat insulating property for accommodating the mercury 35 provided with a shutter 33 in a portion connected to the gas introduction pipe 5C is provided. The pressure vessel 31 is provided.

The pressurizing container 31 is provided with a piston 32 that is vertically movable with the container 31 as a cylinder. The piston 32 and the shutter 33 that can be opened and closed with respect to the gas introduction pipe 5C are heat insulating members. Has been formed.

Then, the piston 32 is pushed down to introduce the mercury 35 into the pressure vessel 31 through the mercury supply port 34 of the pressure vessel 31, the piston 32 is pushed up to pressurize the mercury 35 to a predetermined pressure, and then the shutter is released. By opening 33, fine particles of mercury 35 are formed by adiabatic expansion that occurs at that time and pop out, dispersed in a carrier gas consisting of hydrogen gas flowing in the gas introduction pipe 5C, and the dispersed fine particles of mercury. The droplets are introduced into the reaction tube 1 together with the mixed carrier gas.

Incidentally, in order to make mercury 35 into fine droplets, after pushing up the piston 32 in the pressure vessel 31, the piston 32 is lowered and adiabatically expanded to form fine droplets of mercury 35, and Alternatively, the shutter 33 may be opened.

The amount of fine particles of mercury dispersed in the carrier gas is
When mercury is completely gasified, the pressure is adjusted to 2 × 10 ^-2 atm and introduced into the reaction tube 1. Also, the reaction tube 1
From inside the other branched gas inlet pipe 5A, dimethyl cadmium supported on hydrogen gas was supplied at 3 × 10 ^-5 atm.
From 5B, 2x10 of diethyl tellurium supported on hydrogen gas was used.
^The epitaxial crystal layer made of Hg _0.8 Cd _0.3 Te can be grown on the substrate 2 by introducing it at a partial pressure of ⁻⁴ atm and heating the susceptor 3 so that the temperature of the substrate 2 becomes 400 ° C.

In such a method, mercury that has become a fine particle droplet due to adiabatic expansion and is dispersed in the carrier gas is
The required amount of mercury can be transported onto the susceptor 3 without adhering to the inner walls of the 5C and the reaction tube 1 without preheating them, and the flow rate of the carrier gas in which fine particles of mercury are dispersed is controlled. Thus, mercury having a desired partial pressure can be introduced into the reaction tube 1.

Further, FIG. 2 is an explanatory view of a second embodiment of the vapor phase epitaxial growth apparatus of the present invention, and the parts having the same functions as those in FIG. 1 are designated by the same reference numerals.

This embodiment is different from the first embodiment shown in FIG. 1 in that the positive electrode is provided in the space between the shutter 33 in the pressure vessel 31 and the portion connected to the gas introducing pipe 5C as shown in the figure. A metal wire 41 is provided, and a DC voltage is applied by using a DC power supply 42 so that the metal wire 41 serves as a positive electrode and the pressure vessel 31 serves as a negative electrode, and mercury is formed into fine particles by adiabatic expansion. Is configured to be charged with a negative charge opposite to the charged wire net 41, and the branched gas introduction pipes 5C and 5 and the susceptor 3 are provided.
An electrode 43 made of a metal plate or the like is provided on the outer wall surface of the reaction tube 1 on the gas introduction side with respect to the position where is stored, and a DC voltage is applied by using a DC power supply 44 so that the electrode 43 becomes negative. It is that.

With such a configuration of the embodiment, the DC power source 44 is generated by adiabatic expansion from the inside of the heat-insulating pressure vessel 31.
The mercury in the form of fine particles that fly out through the wire net 41 to which a DC voltage is applied is dispersed in the carrier gas flowing in the gas introduction pipe 5C in a negatively charged state, and this is dispersed. The carrier gas mixed with the negatively charged particulate mercury droplets is introduced into the reaction tube 1 together with the carrier gas containing the epitaxial growth gas from the other gas introduction tubes 5A and 5B.

At this time, by applying a DC voltage from the DC power supply 44 so that the electrode 43 made of a metal plate or the like provided on the outer wall surface of the gas introduction tubes 5C and 5 and the reaction tube 1 on the gas introduction side becomes negative, When the mercury composed of negatively charged fine particle droplets contained in the carrier gas approaches the inner wall surfaces of the gas introduction tubes 5C and 5 and the reaction tube 1 on the gas introduction side, it repels the negative electrode 43. Works and is carried onto the substrate 2 in a state of not adhering to the inner wall surfaces thereof, so that an apparatus capable of realizing more reliable vapor phase epitaxial growth as compared with the first embodiment can be obtained.

FIG. 3 is an explanatory view of the third embodiment of the present invention, and the parts having the same functions as those in FIG. 2 are designated by the same reference numerals.

This embodiment is different from the second embodiment shown in FIG. 2 in that it is described in the second embodiment in the middle of the gas introducing pipe 5C through which a carrier gas composed of hydrogen gas carrying mercury is circulated. Contains mercury 23 instead of a heat-insulating pressurized container,
A mercury container 22 made of, for example, titanium provided with an ultrasonic oscillator 22 that disperses mercury 23 into fine particles by ultrasonic vibration is provided, and a minute space is formed on the mercury 23 in the container 21 from the surface of the mercury 23. Separately, a wire net 41, which serves as a positive electrode for charging negative charge to mercury dispersed in a carrier gas in the form of fine particles, and repels negatively charged fine particles of mercury on the outer wall of the reaction tube 1 on the gas introduction side. That is, the negative electrode 43 made of a metal plate is provided.

According to the configuration of such an embodiment, the vibration of the ultrasonic transducer 22 causes the mercury from the liquid surface of the mercury 23 in the mercury storage container 21.
23 will be ejected as fine particles having a diameter of approximately 0.01 to 0.1 μm. At this time, since a DC voltage is applied to the negative electrode of the container 21 and the positive electrode of the wire net 41 by the DC power source 42, the particulate mercury that jumped out was introduced from the gas introduction pipe 5C in a negatively charged state. It is dispersed in hydrogen gas as a carrier gas, and the dispersed droplets of mercury in the form of fine particles are introduced into the reaction tube 1 together with the carrier gas.

Also at this time, the electrode 43 made of a metal plate provided on the outer wall of the reaction tube 1 on the gas introduction side from the position where the gas introduction pipe 5C and the gas introduction pipe 5 and the susceptor 3 are accommodated By applying a direct current voltage from the direct current power source 44 so that the negative charge potential is equivalent to the negative charge potential charged, the fine particles of mercury introduced together with the negatively charged carrier gas described above to the electrode 43. On the other hand, since the repulsion occurs, the fine particles of mercury do not adhere to the inner walls of the gas introduction pipe 5C and the gas introduction pipe 5 and the reaction pipe 1 on the gas introduction side, and a required amount of mercury is introduced onto the substrate 1. can do.
Therefore, it is possible to obtain an apparatus capable of realizing highly reliable vapor phase epitaxial growth as in the second embodiment.

As described above, according to the present invention, gaseous mercury that easily adheres to the reaction tube 1 and the gas introduction tubes 5 and 5C becomes fine particle droplets or negatively charged fine particle droplets. Introduced into the reaction tube 1 through the gas introduction pipes 5 and 5C in a state of being dispersed in the carrier gas, or the gas introduction pipe 5 having a negative charging potential,
Since it is introduced into the reaction tube 1 through 5C, the gas introduction tube 5,
Even if the 5C and the tube wall of the reaction tube 1 are not heated, there is no risk of mercury adhering to the tube wall, and an inconvenient phenomenon in which another epitaxial growth gas is decomposed before being introduced onto the susceptor 3. Can be resolved.

Moreover, since a desired amount of mercury is introduced into the reaction tube 1 only by adjusting the flow rate of the carrier gas that supports mercury, an epitaxial crystal having a stable composition can be easily obtained.

Furthermore, since the phenomenon that mercury adheres to the gas introduction tube and the wall of the reaction tube can be removed, wasteful consumption of raw materials is avoided, and the inside of the reaction tube is kept clean due to the absence of mercury adhesion and a high-quality epitaxial crystal is obtained. Is obtained.

〔The invention's effect〕

As is clear from the above description, the vapor phase epitaxial growth apparatus of the present invention has an effect of easily obtaining a high-quality epitaxial crystal of a compound semiconductor having a stable composition.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the first embodiment of the apparatus of the present invention. FIG. 2 is an illustration of a second embodiment of the device of the present invention. FIG. 3 is an explanatory diagram of the third embodiment of the present invention. FIG. 4 is an explanatory view of a conventional vapor phase epitaxial growth apparatus. FIG. 5 is an explanatory diagram of a main part of a conventional vapor phase epitaxial growth apparatus. In the figure, 1 is a reaction tube, 2 is a substrate, 3 is a susceptor, 5,5A, 5B and 5C are gas introduction tubes, 21 is a mercury container, 22 is an ultrasonic transducer, and 23,3
5 is mercury, 31 is a pressurized container, 32 is a piston, 33 is a shutter, 34 is a mercury supply port, 41 is a wire mesh, 42 and 44 are DC power supplies, 43
Indicates an electrode.

Claims (3)

(57) [Claims] 1. A carrier gas containing mercury and a carrier gas containing an epitaxial growth gas are introduced into a reaction tube through a gas introduction tube, and the substrate on the susceptor housed in the reaction tube is heated to contain the carrier containing the mercury. A device for growing an epitaxial crystal of a compound semiconductor containing mercury on a substrate by reacting a gas with a carrier gas containing an epitaxial growth gas, wherein the gas introduction pipe has a cylinder having a heat insulating piston and an outlet of the cylinder. Is equipped with a shutter connected to the gas introduction pipe, and is equipped with a heat-insulating pressurized container for containing mercury,
A vapor phase epitaxial growth apparatus characterized in that mercury contained in the pressure vessel is formed into fine droplets by adiabatic expansion by the operation of a piston and a shutter and dispersed and mixed in a carrier gas. 2. A means for imparting an electric charge to mercury dispersed into a carrier gas in the form of fine particles, and
2. The vapor phase epitaxial growth according to claim 1, wherein a gas introduction tube through which the carrier gas containing mercury flows and an electrode for charging the inner wall of the reaction tube to the same polarity as the electric charge applied to the mercury are provided. apparatus. 3. A container for accommodating mercury, in which mercury is made into fine particles by ultrasonic vibration and dispersed and mixed in a carrier gas is attached to a gas introduction pipe, and a carrier gas containing mercury and a carrier gas containing epitaxial growth gas are provided. A compound containing mercury on the substrate, which is introduced into the reaction tube through the gas introduction tube, and which heats the substrate on the susceptor housed in the reaction tube to react the carrier gas containing mercury with the carrier gas containing epitaxial growth gas. An apparatus for growing an epitaxial crystal of a semiconductor, comprising a means for applying an electric charge to the mercury dispersed in the carrier gas in a region where the mercury is made into fine particles and dispersed in the carrier gas, and a carrier gas containing the mercury. An electrode for charging the inner walls of the gas introduction tube and the reaction tube through which the mercury flows to the same polarity as the electric charge applied to the mercury is provided. A vapor phase epitaxial growth apparatus characterized in that