JP2658213B2 - Vapor phase epitaxial growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Regarding a vapor phase epitaxial growth method, a plurality of epitaxial growth gases having different decomposition temperatures introduced into a reaction vessel are surely decomposed on a substrate to cause composition fluctuations and crystal defects. A rotatable susceptor on which a substrate for epitaxial growth is mounted, a plurality of heating means for individually heating a plurality of portions of the susceptor to different temperatures, and a susceptor And a partition plate for vertically partitioning a space on the susceptor corresponding to the plurality of heating means.Epitaxial growth gases having different compositions are respectively supplied to respective spaces on the susceptor partitioned by the partition plate. A vapor phase epitaxial growth apparatus comprising a reaction vessel provided with an individual gas introduction pipe at the top. Wherein the first epitaxial growth gas introduced from one of the gas introduction pipes is thermally decomposed by one of the plurality of heating means by the first heating means. The first epitaxial crystal layer grown on the substrate and the second epitaxial growth gas introduced from the other second gas introduction pipe of the gas introduction pipe can be set to a temperature different from that of the first heating means. The second layer grown on the substrate by thermal decomposition by the second heating means
While alternately stacking the epitaxial crystal layers with the substrate by continuously rotating the substrate at a constant speed,
By diffusing each other, a vapor phase epitaxial growth layer having a uniform composition composed of the first epitaxial crystal layer and the second epitaxial crystal layer is grown.

[Industrial applications]

The present invention relates to a vapor phase epitaxial growth method, and in particular, introduces a plurality of types of epitaxial growth gases having different decomposition temperatures into a reaction tube so that the gas can be decomposed on a substrate, and can form an epitaxial layer free from composition fluctuation and crystal defects. The present invention relates to an epitaxial growth method.

A compound semiconductor crystal of mercury / cadmium / tellurium (Hg _1-X Cd _X Te) is used as a material for the infrared detecting element. In order to obtain such a crystal in a thin layer state and in a large area, a vapor phase epitaxial growth method is used. Is used.

[Conventional technology]

As shown in FIG. 3, in a conventional vapor phase epitaxial growth apparatus, a susceptor 2 made of graphite and having a rotating shaft 2A is installed in a reaction vessel 1 made of quartz, and cadmium tellurium (epitaxial growth) is placed on the susceptor 2 for epitaxial growth. CdT
e) The substrate 3 is set. The inside of the reaction vessel 1 is evacuated by an exhaust pump (not shown) connected to the exhaust pipe 4 until a predetermined degree of vacuum is reached, and then the gas is introduced from a gas introduction pipe 5 above the vessel 1 by a gas mixer (not shown). As a carrier gas, mercury gas supported on hydrogen gas, dimethylcadmium [(CH ₃ ) ₂ Cd] gas supported on hydrogen gas, and diethyl tellurium [(C ₂ H ₅ ) ₂ supported on hydrogen gas as carrier gases Te] gas or the like is introduced into the reaction vessel 1.

The high-frequency induction coil 6 provided around the reaction vessel 1
The susceptor 2 is heated by applying high-frequency power to the substrate 3, the substrate 3 is heated to a temperature of about 400 ° C., the epitaxial growth gas introduced on the substrate 3 is decomposed, and Hg is deposited on the substrate.
_1-X Cd _X Te epitaxial layers are grown.

[Problems to be solved by the invention]

Such Hg _1-X Cd _X Te crystals are formed by the decomposition of diethyl tellurium, the mixed crystal of mercury telluride (HgTe) formed by the bond between Te and Hg, and the decomposition of dimethylcadmium. A mixed crystal of cadmium telluride (CdTe) formed by Cd and Te formed by the decomposition of diethyl tellurium is formed first, and the elements constituting each mixed crystal diffuse into each other to form Hg _1-X Cd It is believed that _X Te crystals are formed.

By the way, among the above-mentioned gases for epitaxial growth,
Mercury is already in the state of a single element, and the decomposition temperature of dimethylcadmium is 260 ° C., and the decomposition temperature of diethyl tellurium is 380 ° C., which is the most difficult to decompose among the above three types of gases for epitaxial growth.

This decomposition temperature is, for example, in the case of dimethyl cadmium,
And atoms of cadmium (Cd) forming the compound of dimethyl cadmium [Cd (CH _{3) 2],} a methyl group (CH ₃₎ -
In degraded by temperature, the compound in the case of diethyl tellurium, the atomic tellurium (Te) which forms a diethyl tellurium [Te (C ₂ H _{5) 2]],} ethyl (H ₂ H ₅₎ to - Is the temperature at which it is decomposed into

The growth temperature of HgTe is 410 ° C, and the growth temperature of CdTe is 390 ° C.
Therefore, if the temperature of the substrate for epitaxial growth is kept constant at 400 ° C. as in the conventional apparatus, there is a problem that the growth of either HgTe or CdTe crystals is hindered.

As described above, when an epitaxial growth gas having a different decomposition temperature is introduced onto a substrate having a constant temperature of, for example, 400 ° C., the degree of decomposition of the gas varies depending on each epitaxial growth gas, so that an epitaxial layer having a desired composition is formed on the substrate. There is a problem that cannot be obtained.

In addition, if insufficiently decomposed epitaxial growth gas components adhere to the substrate, unreacted Cd atoms that do not become CdTe crystals and unreacted Te atoms that do not become HgTe crystals remain on the substrate, and these atoms remain. Then, there is a problem that crystal defects of the epitaxial crystal occur.

The present invention solves the above-described problems, reliably forms a mixed crystal of HgTe having a different growth temperature, and a mixed crystal of CdTe, and further diffuses the mixed crystal of HgTe and the mixed crystal of CdTe mutually. Accordingly, it is an object of the present invention to provide a vapor phase epitaxial growth method for growing a uniform vapor phase epitaxial layer of HgCdTe composed of these mixed crystals.

[Means for solving the problem]

A rotatable susceptor on which a substrate for epitaxial growth is mounted, a plurality of heating means for individually heating a plurality of portions of the susceptor to different temperatures, and a housing for accommodating the susceptor. A gas introduction pipe is provided at an upper part of the susceptor, which is provided with a partition plate which vertically partitions in correspondence with the heating means, and which individually introduces epitaxial growth gases having different compositions into respective spaces on the susceptor partitioned by the partition plate. A vapor phase epitaxial growth method using a vapor phase epitaxial growth apparatus comprising a reaction vessel, wherein the first epitaxial growth gas introduced from one of the gas introduction pipes is supplied to one of the plurality of heating means. A first epitaxial crystal layer grown on the substrate by thermal decomposition by first heating means; The second epitaxial growth gas introduced from the second gas introduction tube of the other gas introduction tube is grown on the substrate by thermal decomposition by the second heating means which can be set to a temperature different from that of the first heating means. The second
While alternately stacking the epitaxial crystal layers with the substrate by continuously rotating the substrate at a constant speed,
By diffusing each other, a vapor phase epitaxial growth layer having a uniform composition composed of the first epitaxial crystal layer and the second epitaxial crystal layer is grown.

(Operation)

In the vapor phase epitaxial growth method of the present invention, a plurality of portions of a rotatable susceptor on which a substrate for epitaxial growth is mounted are individually heated to different temperatures by a plurality of heating means, respectively, in a reaction vessel containing the susceptor. A partition plate for vertically partitioning the space on the susceptor corresponding to the plurality of heating means is provided. At the upper part of the reaction vessel, each space on the susceptor partitioned by the partition plate has a different composition. Gas introduction pipes for individually introducing the epitaxial growth gases of the above are provided, and the respective temperatures of these heating means are set to different temperatures optimal for decomposing the respective epitaxial growth gases supplied to the space partitioned by the partition plate. can do.

Since the plurality of heating means can be heated to different temperatures and the substrate can be continuously rotated at a constant speed, a plurality of epitaxial crystal layers having an accurate composition are alternately stacked and diffused mutually. By doing so, it is possible to grow a vapor phase epitaxial growth layer having a uniform composition composed of the plurality of epitaxial crystal layers.

〔Example〕

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

FIG. 1 is a sectional view of an apparatus used in the vapor phase epitaxial growth method of the present invention, and FIG. 2 is a plan view of a main part of FIG.

As shown in FIGS. 1 and 2, a substrate 13 for epitaxial growth of CdTe is placed on a disc-shaped carbon susceptor 12 having a rotating shaft 11 rotatable by a motor (not shown). . At the bottom of this susceptor 12,
A heating heater 14A consisting of an infrared lamp heated to a set temperature of 390 ° C. and a heater 14B consisting of an infrared lamp heated to a set temperature of 410 ° C. are respectively rotated about a disk-shaped susceptor so as to substantially bisect the susceptor. It is provided on the left and right with 11 as the center.

The reaction vessel 15 containing the susceptor 12 and the heaters 14A and 14B has a cylindrical shape having a gas inlet pipe 16 with a narrowed upper portion and a gas outlet pipe 17 at the bottom. On the center of the substrate 13, that is, on the rotating shaft 11, there is provided a quartz partition plate 18 that bisects the space inside the container on the substrate 13 in the vertical direction. 16A and 1
Divided into 6B.

After the inside of the reaction vessel 15 is evacuated to a degree of vacuum of 10 ^-7 torr using an exhaust pump (not shown) connected to the discharge pipe 17, hydrogen gas is supplied from the gas introduction pipe 16 at 4 / min.
The substrate 13 is rotated at a rotation speed of 10 rpm. Then, dimethyl cadmium and diethyl tellurium are supported and introduced in a hydrogen gas as a carrier gas from the gas introduction pipe 16A side to a partial pressure of 2 × 10 ⁻⁵ atm and diethyl tellurium at a partial pressure of 1 × 10 ⁻⁴ atm. Adjust so that the flow rate is 2 / min.

Also, 2 × 10 ^{-4 of} diethyl tellurium was introduced from the gas introduction pipe 16B
Atmospheric pressure and mercury are introduced while being supported on hydrogen gas as a carrier gas so as to have a partial pressure of 2 × 10 ^-2 atm, and the total gas flow rate is adjusted to 2 / min.

In this way, mercury and diethyl tellurium gas having a high decomposition temperature are introduced into the high-temperature heating region 13B side of the substrate shown in FIG. The gas is introduced from the gas introduction tube 16A to the low-temperature heating region 13A of the substrate by the partition plate 18. And since those gases are surely decomposed on the substrate, HgTe with stable composition is placed on the high temperature region side of the substrate.
CdTe is formed with a stable composition on the low-temperature side of the substrate, and by rotating this substrate, these HgTe and CdTe diffuse into each other, forming an epitaxial layer of Hg _1-X Cd _X Te .

Although the present embodiment has been described with reference to the example of forming the Hg _1-X Cd _X Te epitaxial layer, the present invention is also applicable to the case where the epitaxial layer is formed on the substrate using an epitaxial growth gas having a different decomposition temperature. However, the device of the present invention is applicable.

Further, the number of the partition plates and the number of heaters may be set to an appropriate number according to the type of the epitaxial growth gas.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, since the epitaxial growth gas can be reliably decomposed, there is an effect that a high-quality epitaxial crystal can be obtained without causing a composition variation and without generating crystal defects.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an apparatus used in the vapor phase epitaxial growth method of the present invention, FIG. 2 is a plan view of a main part of FIG. 1, and FIG. It is sectional drawing. In the figure, 11 is a rotation axis, 12 is a susceptor, 13 is a substrate for epitaxial growth, 13A is a high-temperature heating area, 13B is a low-temperature heating area, 14A and 14
B indicates a heater, 15 indicates a reaction vessel, 16, 16A and 16B indicate gas introduction tubes, 17 indicates a gas discharge tube, and 18 indicates a partition plate.

Claims (1)

(57) [Claims] A rotatable susceptor on which a substrate for epitaxial growth is mounted; a plurality of heating means for individually heating a plurality of portions of the susceptor to different temperatures; A partition plate for vertically partitioning the space corresponding to the plurality of heating means,
Vapor phase epitaxial growth using a vapor phase epitaxial growth apparatus comprising a reaction vessel provided at the top with a gas introduction pipe for separately introducing epitaxial growth gases of different compositions into respective spaces on the susceptor partitioned by the partition plate A method comprising: growing a first epitaxial growth gas introduced from one of the gas introduction pipes on the substrate by thermal decomposition by one of the plurality of heating means. A first epitaxial crystal layer and a second heating means capable of setting a second epitaxial growth gas introduced from the other second gas introduction pipe of the gas introduction pipe to a temperature different from that of the first heating means. The substrate is continuously rotated at a constant speed with the second epitaxial crystal layer grown on the substrate by thermal decomposition. The first epitaxial crystal layer and the second epitaxial layer are alternately stacked by diffusing each crystal layer.
A vapor phase epitaxial growth method characterized by growing a vapor phase epitaxial growth layer having a uniform composition consisting of the following epitaxial crystal layer.