JPH05144850A - Vapor epitaxial growth device and method of growing - Google Patents

Abstract

PURPOSE:To make it possible to form easily the epitaxial crystal of an Hg1-XCdXTe with a stabilized composition or a superlattice structure having steep boundary surfaces by a method wherein the title device is provided with a reaction tube, a substrate heating stage, a preheating plate and a heating means, which are respectively specified, and the like. CONSTITUTION:A vapor epitaxial growth device is provided with a reaction tube 1 for housing a substrate 3 for epitaxial use, a substrate heating stage 2, which is installed in the tube 1 and heats the substrate 3 to be placed thereon, a preheating plate 12, which is provided in the vicinity of the stage 2, is provided with a heating region 11 and a non-heating region 47 and is provided with a moving means for removing selectively the region 11 only, and a heating means (a high-frequency induction coil) 5 for heating the stage 2 and the region 11 of the plate 12. Gases for epitaxial growth use, whose decomposition temperatures are different from each other, are made to flow in the tube 1 in synchronization with the movement of the region 11 of the plate 12 to the position on the gas inflow side of the substrate 3 or a position other than the position on the gas inflow side and the gases for epitaxial growth use are made to pass through over the region 11 or are fed on the substrate 3 in a state of non-passage. The device is constituted in such a way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase epitaxial growth apparatus and a growth method for a compound semiconductor of a group 2-6 containing mercury such as mercury cadmium tellurium (Hg _1-x Cd _x Te).

Such a compound semiconductor such as Hg _1-x Cd _x Te is usually formed as an epitaxial layer on a substrate for epitaxial growth such as gallium arsenide (GaAs).
When forming a semiconductor device such as an infrared detector using this material, the composition of the atoms that make up the Hg _1-x Cd _x Te crystal is uniform in the plane within the epitaxial layer formed on the substrate. Materials are required.

Particularly, when the x value of Hg _1-x Cd _x Te is different, the wavelength of the infrared ray which responds is different depending on the x value. A Hg _1-x Cd _x Te crystal having a uniform x value over the entire area of the epitaxial growth substrate is desired.

[0004]

2. Description of the Related Art Conventionally, when epitaxially growing such an Hg _1-x Cd _x Te crystal, for example, as shown in FIG. 7 (a), epitaxial growth of GaAs or the like is performed on a substrate heating table 2 installed in a reaction tube 1. The substrate 3 is placed and the inside of the reaction tube 1 is evacuated.

Next, a mixed gas of hydrogen gas carrying mercury (Hg), diisopropyl Te and dimethyl Cd is introduced into the reaction tube 1 as a gas for epitaxial growth through the gas introduction tube 4.

Then, the substrate 3 for epitaxial growth is heated by the high frequency induction coil 5 provided around the reaction tube, so that the gas for epitaxial growth reaching the substrate 3 is thermally decomposed and the Hg _1-x Cd _x Te crystal is produced. Is epitaxially grown.

By the way, the above mercury is in an atomic state, and the decomposition temperature of dimethyl Cd is 230 ° C., which is lower than the decomposition temperature of diisopropyl Te of 300 ° C. The energy of formation of a CdTe crystal formed by the reaction of the Cd atom generated by decomposition of dimethyl Cd and the Te atom generated by decomposition of diisopropyl Te is 21 Kcal / mol (enthalpy of formation is −24.6 Kcal / mol) is the value of Te atom and Hg
Of the formation energy of HgTe crystals formed by the reaction of atoms
It is lower than the value of 30 Kcal / mol (enthalpy of formation is -8.1 Kcal / mol).

The above-mentioned Hg _1-x Cd _x Te crystal is CdTe
It is said that it is a mixed crystal of crystals and HgTe crystals, and if the mixing ratio of these crystals is different, the x value of Hg _1-x Cd _x Te will also change, and composition change will occur.

When all the epitaxial growth gases are mixed and supplied onto the epitaxial growth substrate 3 as in the conventional case, as shown in FIG. 7 (b), HgTe crystals having a large generation energy are uniformly formed on the epitaxial growth substrate 3. Cd, which has a small generation energy on the gas inflow side,
The formation rate of Te crystals is high, and CdTe tends to form earlier than HgTe.

Therefore, since the epitaxial growth gas (dimethyl Cd) for CdTe generation is consumed on the gas inflow side of the epitaxial growth substrate, a distribution of the generated amount occurs as shown by the curve a.

If the flow velocity of the gas is increased in order to suppress the gas consumption, the heating of the epitaxial growth gas becomes insufficient, and it tends to be difficult to generate HgTe crystals having a large generation energy.

Therefore, even if the gas flow velocity is increased or decreased, Hg _{1- x} Cd _x Te crystals having a nonuniform composition (x) value tend to grow. In order to prevent such nonuniformity of the composition, as a first method, for example, the CdTe crystal is formed at a gas flow rate and an epitaxial growth temperature at which the CdTe crystal is uniformly generated on the entire surface of the substrate. Also, at a gas flow rate and epitaxial growth temperature at which HgTe is uniformly generated on the entire surface of the substrate.
Form HgTe. Then, there is a method in which the CdTe crystal and the HgTe crystal are alternately grown and laminated, and the Hg _1-x Cd _x Te crystal having a uniform composition is epitaxially grown on the substrate by mutual diffusion of the both.

As a second method, for example, by heating diisopropyl Te having a low decomposition temperature in advance to facilitate decomposition, the production rate of Te atoms is increased, and this is reacted with Hg gas. , HgTe, whose generation rate is slower than that of CdTe
There is a method of increasing the production rate of CdTe crystal and HgTe crystal on the substrate to increase the production rate of CdTe.

This second method is a method previously proposed by the applicant in Japanese Patent Application No. 3-52339.

[0015]

By the way, the conventional first
In this method, the flow rate and pressure of dimethyl Cd gas or diisopropyl Te gas must be changed each time the stacked CdTe crystal and HgTe crystal grow, and the gas flow rate and the gas flow must be adjusted when the pressure is adjusted. There is a problem of becoming stable.

Due to the above problems, CdTe crystal and HgTe
There is a problem that the composition of the crystal is not formed uniformly on the substrate, and in the formation of the superlattice structure, the composition does not abruptly change at the boundary surface of the crystals having different compositions.

In the second method, the gas flow for epitaxial growth does not become unstable.
When HgTe crystals and CdTe crystals are alternately formed, there is a problem that the temperature of the preheating section must be raised or lowered, temperature control takes time, and growth cannot be continuously performed.

Therefore, there is a problem that the surface of the crystal formed when switching to a crystal having a different composition is rough or a superlattice structure having a steep boundary surface cannot be realized. The present invention solves the above-mentioned problems, and provides a vapor phase epitaxial growth apparatus and a growth method therefor capable of obtaining an epitaxial crystal of Hg _1-x Cd _x Te having a uniform composition over the entire region of a substrate. To aim.

[0019]

The vapor phase epitaxial growth apparatus of the present invention, as set forth in claim 1, supplies epitaxial growth gases having different decomposition temperatures onto an epitaxial growth substrate contained in a reaction tube, In an apparatus for forming epitaxial layers having different generated energies on the substrate, a reaction tube accommodating the substrate for epitaxial growth, a reaction tube installed in the reaction tube, the substrate for epitaxial growth is placed, and the substrate is heated. The substrate heating table to be, and provided in the vicinity of the substrate heating table, comprising a heating region and a non-heating region, the gas inflow side of the epitaxial growth gas flowing into the reaction tube, or at a position other than the gas inflow side, Independently of the substrate heating table, a preheating plate provided with a moving means for selectively moving only the heating region,
A heating means for heating the heating region of the substrate heating table and the preheating plate, and moving the heating region of the preheating plate to a gas inflow side of the epitaxial growth substrate or a position other than the gas inflow side. In synchronism, the epitaxial growth gases having different decomposition temperatures are flown into the reaction tube, and the epitaxial growth gas is supplied onto the substrate while passing through the heating region or not passing therethrough. Characterize.

According to a second aspect of the present invention, the preheating plate having the non-heating region and the heating region according to the first aspect is formed into a donut shape and is concentrically arranged on a side surface of a disk-shaped substrate heating table. The preheating plate is rotationally moved independently of the rotation of the substrate heating table so that the heating region of the preheating plate can be moved to a gas inflow side of the substrate or a region other than the gas inflow side of the substrate. Is characterized by.

According to a third aspect of the present invention, the heating region of the preheating plate is formed of a material that easily absorbs electromagnetic waves, and the non-heating region of the preheating plate is formed of a material that hardly absorbs electromagnetic waves. The heating area of the preheating plate is heated by the heating means of the substrate heating table.

Further, as described in claim 4, when the heating region of the preheating plate is moved to the gas inflow side of the epitaxial growth substrate, mercury gas and epitaxial growth gas having a high decomposition temperature are flown into the reaction tube. While growing an epitaxial crystal with large production energy, when the heating region is moved to a region other than the gas inflow side, mercury gas, an epitaxial growth gas with a high decomposition temperature and an epitaxial growth gas with a low decomposition temperature are introduced into the reaction tube. Then, an epitaxial crystal having a small generation energy is grown, and a compound semiconductor crystal containing mercury is grown on the substrate by mutual diffusion of both formed epitaxial crystals.

Further, as described in claim 5, when the heating region of the preheating plate is moved to the gas inflow side of the epitaxial growth substrate, the mercury gas and the epitaxial growth gas having a high decomposition temperature are flown into the reaction tube, It is characterized in that a compound semiconductor crystal having a high generation energy is grown on the substrate.

Further, as described in claim 6, when the heating region of the preheating plate is moved to the gas inflow side of the epitaxial growth substrate, mercury gas, an epitaxial growth gas having a low decomposition temperature and an epitaxial growth gas having a high decomposition temperature are used. Gas is introduced into the reaction tube and either a crystal with a large production energy and an epitaxial crystal with a low production energy is mixed on the substrate, or mercury gas and an epitaxial growth gas with a high decomposition temperature are introduced into the reaction tube to produce the gas. While growing an epitaxial crystal with large energy, when the heating region of the preheating plate is moved to a position other than the gas inflow side of the substrate, mercury gas, an epitaxial growth gas with a low decomposition temperature, and a high decomposition temperature The gas for epitaxial growth is introduced into the reaction tube and generated on the substrate. Growing energy small epitaxial crystal, characterized in that the generated energy and the crystal layer, and sequentially stacked superlattice structure generate energy small epitaxial crystal alternating containing most of the epitaxial crystals.

[0025]

[Function] In Hg _1-x Cd _x Te crystals, the HgTe formation energy is higher than the CdTe formation energy between the CdTe crystal and the HgTe crystal in the mixed crystal, so the HgTe formation rate becomes slower. .. Therefore, all the source gases, that is, Hg gas, diisopropyl Te gas, and dimethyl Cd, without preheating the Hg gas as the Hg source material and the diisopropyl Te gas as the Te source material.
When the gases are mixed and flowed in the reaction tube at the same time, as shown in Fig. 6 (a), when the gas flow rate is high, HgTe is not sufficiently produced, and the amount of HgTe produced is seen from the gas inflow side of the substrate. This is the rear, which causes nonuniform composition. In the figure, a is the CdTe generation curve, b
Is the HgTe generation curve, 3 is the substrate for epitaxial growth, the vertical axis is the amount of CdTe or HgTe generated, and the horizontal axis is the position of the reaction tube as seen from the gas moving direction.

On the other hand, when the gas flow velocity is low, CdTe crystals are almost generated in front of the substrate as shown in FIG. 6 (b), which also causes nonuniform composition. In the figure, a is the CdTe generation curve, b
Is the HgTe generation curve, 3 is the substrate for epitaxial growth, the vertical axis is the amount of CdTe or HgTe generated, and the horizontal axis is the position of the reaction tube as seen from the gas moving direction.

Therefore, in the present invention, as shown in FIG. 1, by providing only the heating region 11 of the preheating plate 12 having the heating region 11 and the non-heating region 47 in the vicinity of the epitaxial growth substrate 3, Hg gas can be obtained. , Diisopropyl Te gas was previously heated to give energy, and Hg
Allow Te generation to occur.

At this time, the heating region 11 of the preheating plate 12 can be moved from the gas inflow side of the epitaxial growth substrate to a position other than the gas inflow side, so that the flow rate of the epitaxial growth gas, the epitaxial growth temperature, etc. With the growth conditions kept constant, HgTe is generated on the substrate or HgTe is not generated depending on the presence or absence of the heating region 11 of the preheating plate 12.

That is, according to the present invention, the following growth is possible. (1) Gases of Hg, dimethyl Cd, and diisopropyl Te were flown into the reaction tube 1 at a gas flow rate of 10 liter / min, and the preheating plate 12
The heating region 11 is installed on the gas inflow side of the epitaxial growth substrate 3.

When epitaxial growth is performed under these conditions, CdTe and HgTe have the same generation rate on the substrate 3, so that Hg _1-x Cd _x Te crystals having a uniform composition can be obtained on the entire surface of the substrate. This state is shown in the curve a of FIG. In the figure, the horizontal axis represents the position of the reaction tube, and the vertical axis represents the amount of CdTe or HgTe produced. (2) Gases of Hg, dimethyl Cd, and diisopropyl Te are made to flow into the reaction tube 1, and the heating region 11 of the preheating plate 12 is located at a position other than the gas inflow side of the epitaxial growth substrate 3 (position opposite to the gas inflow side). ), And it is installed on the gas outflow side of the epitaxial growth substrate 3.

Under this condition, when the gas flow rate is increased to 10 liters / min and epitaxial growth is performed, CdTe crystals having a uniform thickness grow on the entire surface of the substrate 3. Curve b in the figure
Shows this state. In the figure, the horizontal axis is the position of the reaction tube and the vertical axis is Cd.
Indicates the amount of Te or HgTe produced. (3) Hg and diisopropyl Te gas are caused to flow in the reaction tube 1 at a gas flow rate of 10 l / min, and the heating region 11 of the preheating plate 12 is installed on the gas inflow side of the epitaxial growth substrate 3.

When epitaxial growth is performed under these conditions, HgTe crystals having a uniform thickness grow on the entire surface of the substrate. This is shown in the curve c in the figure. In the figure, the horizontal axis represents the position of the reaction tube, and the vertical axis represents the amount of CdTe or HgTe produced.

Curve d in FIG. 5 shows that Hg, dimethyl Cd, and diisopropyl Te are introduced into the reaction tube at a gas flow rate of 10 liter / min.
FIG. 3 shows a HgTe generation curve when the heating region is moved to the opposite side from the gas introduction side of the substrate by flowing at.

The above-mentioned states (1), (2) and (3) correspond to the state of supply of the epitaxial growth gas to the reaction tube 1 and the gas for the epitaxial growth substrate 3 in the heating region 11 of the preheating plate 12. Since it can be freely adjusted by selecting either the inflow side or the gas outflow side, it is possible to continuously form a stack of crystals having different composition ratios while the gas flow is stabilized.

Even when the heating region 11 of the preheating plate 12 is fixed to the gas inflow side of the epitaxial growth substrate 3, if only the source gases of dimethyl Cd and diisopropyl Te are flown,
A CdTe crystal with a uniform thickness can be obtained.However, in this way, high-temperature diisopropyl Te and high-temperature dimethyl Cd react with each other, and the reaction in the gas phase becomes abrupt to form a CdTe crystal. Since there is a problem that the surface of is rough, the condition of (2) above is adopted.

Further, the piping for flowing the Hg gas needs to be kept at a high temperature in order to prevent the solidification of Hg, and there is a problem in the reliability and durability of the switching valve for the gas used. It is better not to switch between inflow and non-inflow.

When the supply of Hg to the substrate is stopped, the dissociation pressure of Hg is high, so that Hg vacancies are likely to occur in the Hg _1-x Cd _x Te crystal and a superlattice structure is formed. , Hg _1-x
When continuously growing CdTe from Cd _x Te, the lower layer of HgT
e, The surface of Hg _1-x Cd _x Te is rough, and the surface of the formed CdTe layer is also rough.HgTe, Hg _1-x Cd _x Te and CdTe are alternately stacked in a multilayer structure to form a superlattice. To form the structure,
It is advisable to carry out continuous growth by changing the position of the heating region while continuously supplying Hg without switching the Hg valve as in the present invention.

As described above, according to the present invention, Hg _1-x having a uniform composition can be formed on a large-area substrate while maintaining a stable gas flow.
Cd _x Te crystals can grow with this x value arbitrarily changed. In addition, since composition switching can be performed stably and rapidly, superlattices formed by alternating layers of Hg _1-x Cd _x Te composed of mixed crystals with different composition ratios or alternating layers of CdTe layers and Hg _1-x Cd _x Te The structure is obtained with a sharp composition variation at the boundary surface of the stacked crystals.

The above is summarized in Table 1.

[0040]

[Table 1]

[0041]

Embodiments of the present invention will be described in detail below with reference to the drawings. As shown in FIG. 1 (a), the vapor phase epitaxial growth apparatus of the present invention includes a reaction tube 1 for accommodating a substrate 3 for epitaxial growth, a substrate 3 placed in the reaction tube 1, and the substrate 3 placed thereon. The substrate heating table 2 has a disk shape.

Further, as shown in FIG. 1 (b), a heating region 11 composed of graphite partially rotates around the substrate heating table 2 independently of the rotation of the epitaxial growth substrate 3. Then, a quartz preheating plate 12 having a non-heating region 47 in the other part is arranged, and a high frequency induction for heating the substrate heating table 2 and the heating region 11 of the preheating plate 12 is provided around the reaction tube 1. The coil 5 is installed.

A partition plate 13 for horizontally dividing the reaction tube 3 is provided on the gas inflow side of the preheating plate 12 of the reaction tube 1.
The dimethyl Cd gas having a low decomposition temperature is introduced into the upper portion of the partition plate 13, and the diisopropyl Te gas having a high decomposition temperature is introduced into the lower portion of the partition plate 13.

The reaction tube 1 is branched from the preheating plate 12 of the reaction tube 1 to the gas inflow side, and Hg is branched from the branch tube 14.
The gas flows into the reaction tube 1. An appropriate heat insulating material 15 is wound around the branch tube 14 through which the mercury gas passes and the reaction tube 1 in order to prevent the mercury gas from solidifying, and a heat insulating heater is embedded in the inside thereof.

Further, as shown in FIG. 2, the substrate heating table 2 is
It is installed on a support 16 having a disk shape and provided with protrusions 21B on the periphery, and a part of the protrusion of this support 16 is hollowed out to install a shaft 18A having a gear 17A made of quartz. Are led out to the outside of the reaction tube 1. The screw 19A formed on the bottom of the substrate heating table 2 and the gear 17A are fitted together. Then, the protrusion 21A provided at the center of the support base 16 and the bottom portion of the substrate heating base 2 are fitted to each other, and the shaft 18A is rotated, so that the substrate heating base 2 is rotated independently of the preheating plate 12. To do.

Further, the preheating plate 12 is provided with a quartz gear 17B and a shaft 18B so as to be independently rotatable independently of the substrate heating table 2, and the shaft 18B is provided in the reaction tube 1 in the same manner as described above. It is led out. The screw 19B formed on the bottom of the preheating plate 12 and the gear 17B are fitted together.

A case where an Hg _1-x Cd _x Te crystal is epitaxially grown on a GaAs substrate by using such a vapor phase epitaxial growth apparatus of the present invention will be described. As shown in FIG. 1 (a), a substrate 3 for epitaxial growth made of GaAs is placed on the substrate heating table 2 of the reaction tube 1, the inside of the reaction tube 1 is evacuated, and then the substrate heating table 2 is heated to 600 ° C. To clean the surface of the substrate by hydrogen treatment, and then the temperature of the substrate heating table 2 is lowered to the epitaxial growth temperature of 350 ° C.

Then, the temperature of the mercury vaporizer 43 for accommodating Hg connected to the branch pipe 14 is set to 250 ° C., and a heat insulation heater (not shown) embedded in the heat insulating material 15 is used to prevent solidification of mercury gas. Insulate by heating to a temperature of 250 ° C.

Next, the shaft 18B is rotated to move the heating region 11 of the preheating plate 12 to the gas outflow side of the substrate 3 for epitaxial growth, and in this state, the valve 44 is opened and the hydrogen gas in the dimethyl Cd evaporator 41 is not supplied. Flow rate controller 50A, 51A so that the partial pressure of dimethyl Cd becomes 5 × 10 ^-5 atm.
Adjust. Also, open the valve 45 and use diisopropyl
Hydrogen gas was introduced into the Te evaporator 42 and the diisopropyl Te
The partial pressure of such a 5 × 10 ^-4 atm, a flow rate controller 50B, 51
Adjust B. The valve 46 is closed to prevent hydrogen gas from flowing into the mercury vaporizer 43.

Then, the total flow rate of hydrogen gas, diisopropyl Te and dimethyl Cd is 10 liters / min, hydrogen gas and dimethyl Cd
Fig. 4 shows the total pressure of Cd and diisopropyl Te as 300 torr.
On the GaAs epitaxial growth substrate 3 as shown in
A buffer layer 31 of CdTe is grown to a thickness of 5 μm.

Next, the shaft 18B is rotated to rotate the gear 17B.
The heating area 11 is moved to the gas introduction side of the substrate 3 by rotating the, the valve 46 leading to the Hg evaporator 43 is opened, the flow rate controllers 50C and 51C are adjusted, and the partial pressure of the Hg gas is adjusted to 1.0. × 10 ^-2
Atmospheric pressure, the valve 44 connected to the dimethyl Cd evaporator 41 is closed, the partial pressure of dimethyl Cd is set to zero, and the flow controllers 50B and 51B are adjusted to set the partial pressure of diisopropyl Te to 1 × 10 ⁻³ atm, and the total gas pressure is adjusted. Fig. 4 with 300torr and total gas flow rate of 10 liters / min
As shown in, a HgTe layer 32 is grown to a thickness of 0.6 μm on the substrate.

Then, the shaft 18B is rotated to rotate the gear 17
By rotating B, the heating region 11 is moved to the gas outflow side, and the valve 46 connected to the Hg evaporator 43 is opened as it is, the partial pressure of mercury gas is 1.0 × 10 ^-2 atm, and the dimethyl Cd evaporator is used.
Open the valve 44 connected to 41 to adjust the partial pressure of dimethyl Cd to 5 × 10
^-5 bar, adjust flow regulator 50B, 51B to adjust to diisopropyl
The total gas pressure is 300 torr with Te partial pressure of 5 × 10 ^-4 atm.
CdTe layer 33 is grown to a thickness of 0.2 .mu.m on the substrate as shown in FIG. 4 with a total gas flow rate of 10 l / min.

When forming the CdTe layer 33 described above, a gas is formed so that the CdTe layer can be formed even if Hg gas is flowing over the entire surface of the substrate while the heating region 11 is moved to the gas outflow side of the substrate. When the growth is performed with the total flow rate increased to 10 liters / min, HgTe is simply moved by stopping the supply of dimethyl Cd by moving the heating region 11 to the gas inflow side of the substrate at the same total gas flow rate.
Layers can be formed.

CdTe is formed under the condition that the HgTe layer 32 is formed.
An HgTe layer 32 is further formed on the layer 33, and the CdTe layer is further formed thereon.
Under the condition that the layer 33 was grown, a CdTe layer 33 was further formed, and the Hg
After 10 layers each of Te layer 32 and CdTe layer 33 are grown,
The CdTe layer 33 is formed to a thickness of 0.2 μm.

By alternately stacking the HgTe layers and the CdTe layers in this way and maintaining the substrate heating temperature at 350 ° C., the HgTe layers and the CdTe layers were formed.
Inter-diffusion between layers causes the thickness of 8 μm ± 0.5 μm on the substrate 3 for epitaxial growth with a diameter of 3 inches, and x
High quality Hg _1-x Cd _x Te (x
= 0.25) was obtained.

Table 2 shows the growth conditions described above.

[0057]

[Table 2]

[0058] Further kept at a low temperature of another embodiment interdiffusion does not occur epitaxial temperature of the growth substrate as 300 ° C. of the present invention, 1.0 × 10 ^-2 atm Hg gas onto the substrate, the dimethyl Cd 5 × 10 ^{- 5} atm, diisopropyl Te partial pressure 5 × 10
^-4 atm., And the heating region 11 is moved to the gas opposite side of the epitaxial growth substrate 3 to form a CdTe layer.

Then, the gas supplied onto the substrate is left as it is, and the heating region 11 is moved to the gas inflow side of the epitaxial growth substrate 3 to form a Hg _1-x Cd _x Te layer, and Cd
A superlattice structure consisting of multiple Te layers and Hg _1-x Cd _x Te layers makes the composition variation at the crystal layer interface steep and without opening and closing the mercury valve connected to the Hg evaporator. It can be easily formed.

As another embodiment of the present invention, the temperature of the epitaxial growth substrate is set to 300 ° C. at which mutual diffusion does not occur.
Kept at a low temperature of 1.0 × 10 ^-2 atm of Hg gas, 5 × 10 ^-5 atm of dimethyl Cd and 5 × 10 ^-5 atm of diisopropyl Te on the substrate.
Introduced as 10 ⁻⁴ atmosphere, the heating region 11 is moved to the gas opposite side of the epitaxial growth substrate 3 to form a CdTe layer.

Next, the heating region 11 is formed for epitaxial growth.
A valve that moves to the gas inlet side of the substrate 3 and connects to the Hg evaporator
46, valve 44 connected to dimethyl Cd evaporator 41, diisopro
Adjust the flow controllers 50B and 51B connected to the Pill Te evaporator 42
Therefore, Hg with varying x value _1-xCd_xTe layer on CdTe layer
CdTe layer and Hg with controlled x value
_1-xCd_xTe layers can grow alternately in a superlattice structure.

As described above, when the flow rate controller connected to the evaporator is adjusted in synchronization with the heating region 11 being installed at the gas inflow side of the epitaxial growth substrate or at a position other than the gas inflow side, Hg _{1 of the} desired composition is adjusted. _-x Cd _x Te is obtained.

FIG. 3 shows another embodiment of the apparatus of the present invention.
As shown in the plan view of (a) and the side view of FIG. 3 (b), the cross-sectional area of the reaction tube 1 in the vicinity of the region where the epitaxial growth substrate 3 is installed is laterally enlarged, and the preheating plate 12 is covered with carbon. Made into a plate so as to have a heating region 11 made of quartz and a non-heating region 47 made of quartz, a screw is provided on the bottom of this preheating plate 11, and a shaft 18 having a gear 17 fitted to this screw is used. , The heating area of the preheating plate 12 by rotating this shaft 18.
A structure in which 11 is located on the gas introduction side of the substrate may be adopted.

As shown in the plan view of FIG. 3 (a) and the side view of FIG. 3 (b), a screw is provided on the bottom of the substrate heating table 2, and a shaft 18 having a gear 17 fitted to the screw 18 is provided. The substrate heating table 2 may be moved laterally so that the heating region 11 is located on the gas inflow side of the epitaxial growth substrate 3.

As described above, the heating region 11 and the non-heating region 47 are arranged side by side so that the substrate 3 is moved when the heating region 11 is moved.
By arranging the non-heated region 47 on the gas inflow side, the turbulence of the gas flow on the gas inflow side of the substrate 3 is prevented.

The heating region of the preheating plate may have a structure in which it moves vertically with respect to the surface of the epitaxial growth substrate. Further, the concentric preheating plate 12 or the heating region 11 of the plate-shaped preheating plate 12 may be heated by electromagnetic induction of the high frequency induction coil 5 as in this embodiment, or the substrate may be heated. Separately from the heating of No. 3, a heating heater for selectively heating only the heating region 11 may be provided.

[0067]

As described above, according to the apparatus and method of the present invention, the heating region of the preheating plate is moved to the gas introduction side of the epitaxial growth substrate or at a position other than that, in synchronization with the time. By supplying different types of epitaxial growth gas onto the substrate, or by moving only the heating region while supplying the same type of epitaxial growth gas, the composition of the gas can be kept stable while keeping the gas flow rate conditions constant. Epitaxial crystals of Hg _1-x Cd _x Te or superlattice structure of CdTe and Hg _1-x Cd _x Te can be easily formed, and high quality infrared detectors can be obtained by using these crystals as element forming materials. effective.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a device of the present invention.

FIG. 2 is an explanatory diagram of a preheating plate according to the present invention.

FIG. 3 is an explanatory view of another embodiment of the device of the present invention.

FIG. 4 is a cross-sectional view of a crystal grown by the method of the present invention.

FIG. 5 is an explanatory diagram of the principle of the method of the present invention.

FIG. 6 is an inconvenient state diagram in the conventional method.

FIG. 7 is an explanatory diagram of a conventional device and an inconvenient state diagram.

[Explanation of symbols]

 1 Reaction tube 2 Substrate heating table 3 Epitaxial growth substrate 5 High frequency induction coil 11 Heating area 12 Preheating plate 13 Partition plate 14 Branch pipe 15 Insulation material 16 Support 17,17A, 17B Gear 18,18A, 18B Shaft 19A, 19B Screw 21A, 21B Projection 31 Buffer layer 32 HgTe layer 33 CdTe layer 41 Dimethyl Cd evaporator 42 Diisopropyl Te evaporator 43 Mercury evaporator 44,45,46,47,48,49 Valve 50A, 50B, 50C, 51A, 51B, 511C flow controller

Claims (6)

[Claims] 1. An epitaxial layer having different decomposition energies is supplied onto an epitaxial growth substrate (3) housed in a reaction tube (1) to generate different epitaxial energies on the substrate (3). In an apparatus for forming a film, a reaction tube containing the epitaxial growth substrate (3).
(1), a substrate heating table (2) installed in the reaction tube (1), on which the epitaxial growth substrate (3) is placed, and which heats the substrate (3), and the substrate heating table (2 ) Provided with a heating region (11) and a non-heating region (47), the gas for the epitaxial growth gas flowing into the reaction tube (1) is located on the gas inflow side or at a position other than the gas inflow side. A preheating plate (12) provided with a moving means for selectively moving only the heating region (11) independently of the substrate heating table (2); the substrate heating table (2) and the preheating plate; Heating area of (12) (1
A heating means (5) for heating 1) is provided, and the heating region (11) of the preheating plate (12) is moved to the gas inflow side of the epitaxial growth substrate (3) or a position other than the gas inflow side. In synchronism with the above, the epitaxial growth gases having different decomposition temperatures are flown into the reaction tube (1), and the epitaxial growth gas is supplied onto the substrate while passing through the heating region or not passing through the heating region. A vapor phase epitaxial growth apparatus characterized by the above. 2. The doughnut-shaped preheating plate (12) having the non-heating region (47) and the heating region (11) according to claim 1,
Arranged concentrically on the side surface of the disk-shaped substrate heating table (2), the preheating plate (12) is rotated independently of the rotation of the substrate heating table (2), and the preheating plate ( Heating area (12) (11)
However, the vapor phase epitaxial growth apparatus is characterized in that it can be moved to a gas inflow side of the substrate (3) or a region other than the gas inflow side of the substrate (3). 3. The preheating plate (12) according to claim 1 or 2, wherein the heating region (11) is formed of a material that easily absorbs electromagnetic waves, and the preheating plate (12) is not heated. A vapor phase epitaxial growth apparatus, characterized in that (47) is formed of a material that does not easily absorb electromagnetic waves, and the heating region (11) of the preheating plate (12) is heated by the heating means of the substrate heating table (2). 4. The epitaxial growth substrate (3) is provided with a heating region (11) of the preheating plate (12) according to claim 1, 2, or 3.
When the gas moves to the gas inflow side, the mercury gas and the epitaxial growth gas with a high decomposition temperature are flown into the reaction tube (1) to grow an epitaxial crystal with large production energy, and the heating region (11) is flown into the gas. At the time of moving to a region other than the side, a mercury gas, an epitaxial growth gas with a high decomposition temperature and an epitaxial growth gas with a low decomposition temperature are introduced into the reaction tube (1) to grow an epitaxial crystal with a small production energy, A vapor phase epitaxial growth method characterized in that a compound semiconductor crystal containing mercury is grown on a substrate (3) by mutual diffusion of both formed epitaxial crystals. 5. The epitaxial growth substrate (3) is provided with a heating region (11) of the preheating plate (12) according to claim 1, 2, or 3.
When the gas has moved to the gas inflow side, the mercury gas and the gas for epitaxial growth with a high decomposition temperature are allowed to flow into the reaction tube (1) to grow a compound semiconductor crystal with high production energy on the substrate (3). Characteristic vapor phase epitaxial growth method. 6. The substrate (3) for epitaxial growth is provided with the heating region (11) of the preheating plate (12) according to claim 1, 2, or 3.
When it moves to the gas inflow side of the substrate, mercury gas, an epitaxial growth gas with a low decomposition temperature and an epitaxial growth gas with a high decomposition temperature flow into the reaction tube (1) and the substrate (3)
A mixture of an epitaxial crystal with a large production energy and an epitaxial crystal with a small production energy, or a mercury gas and an epitaxial growth gas with a high decomposition temperature are introduced into the reaction tube (1) to produce an epitaxial crystal with a large production energy. While growing, the heating region (11) of the preheating plate (12), when moved to a position other than the gas inflow side of the substrate (3), the mercury gas and the epitaxial growth gas of low decomposition temperature, decomposition A high temperature epitaxial growth gas is introduced into the reaction tube (1) and the substrate
(3) An epitaxial crystal with a small generation energy is grown on the above, and a crystal layer containing an epitaxial crystal with a large generation energy, and an epitaxial crystal with a small generation energy are alternately laminated to form a superlattice structure. Vapor phase epitaxial growth method.