JP2000264798A - Method of growing II-VI compound semiconductor crystal - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To grow a II-VI group compound semiconductor crystal on a seed crystal by a sublimation method or a halogen chemical transport method and to cool the crystal by a difference in thermal expansion coefficient between the support member and the seed crystal in a cooling process. It is an object of the present invention to provide a method for growing a group II-VI compound semiconductor crystal having excellent crystallinity by suppressing a stress generated from the support member to a seed crystal. SOLUTION: In a method of disposing a source polycrystal in a growth chamber and growing a group II-VI compound semiconductor crystal on a seed crystal by a sublimation method or a halogen chemical transport method, the seed is cooled in a cooling process after the crystal growth. A method for growing a II-VI compound semiconductor crystal, characterized in that a buffer film that does not adhere to a crystal support member is interposed between the seed crystal and the seed crystal support member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of sublimation or halogen chemical transport on ZnSe, ZnS, CdT on a seed crystal.
e, a method for growing a II-VI compound semiconductor crystal such as CdS.

[0002]

2. Description of the Related Art II-VI group compound semiconductor crystal growth methods are broadly classified into four types: melt growth method, solid phase growth method, solution growth method, and vapor phase growth method. Among them, the vapor phase growth method includes a sublimation method (PVT method and Physical Vapor Transport method) in which a crystal is grown by utilizing the sublimation and condensation of a raw material, and a method in which a halogen is reacted with a raw material to generate a halide and the halogen is formed. Chemical transport method (CVT, Chemical Vapor
Transport method).

[0003] For example, in J. Crystal Growth 94 (1989)
On pages 1 to 5, 5 g of ZnSe powder raw material was placed at one end of a quartz ampoule, and a ZnSe single crystal seed crystal was placed at the other end, and the ampule was sealed. The ampoule was heated and the temperature of the ZnSe powder raw material side was increased. To about 1080 ° C and the temperature on the seed crystal side to about 1
It is reported that by setting the temperature to 070 ° C., a ZnSe crystal was grown on a seed crystal.

In the case of a growth method in which a crystal of a II-VI compound semiconductor is grown on a seed crystal by a sublimation method or a halogen chemical transport method, the seed crystal must be held in some form by a container wall or a support member. No. At this time, if there is a portion at a lower temperature than the seed crystal, chemical transport from the seed crystal to the low temperature portion occurs, causing deterioration of crystallinity of the seed crystal, generation of voids, or in some cases, complete polycrystallization. .

[0005] The decrease in the crystallinity of the seed crystal is inherited by the crystal grown thereon, and lowers the crystallinity of the grown crystal. Therefore, in vapor phase growth, it is necessary to position the seed crystal at the lowest temperature part to prevent the seed crystal itself from being transported.
However, in this case, during the crystal growth, the seed crystal is fixed to the supporting member in the lowest temperature part, and the raw material and the grown crystal are also transported to the lowest temperature part. Not only deposits on the container walls, but also partially adheres to the container wall or the like.

When the crystal is cooled from such a fixed state, since the coefficient of thermal expansion and the temperature dependence generally differ depending on the material, the seed crystal or the grown crystal fixed to the support member or the vessel wall is fixed in the cooling process. The surface experiences tensile or compressive stress. The stress increases the dislocation density of the seed crystal and the grown crystal. In extreme cases, the crystallinity is deteriorated due to cracks and the like.

In order to avoid this problem, conventionally, as a material of the seed crystal supporting member, a material having a thermal expansion coefficient close to that of the grown crystal, a material to which the seed crystal is not easily fixed, or a seed crystal supporting member is selected. There has been proposed a method of coating the surface of the film with a film which is not easily peeled off by the seed crystal. However, the above method was not enough to completely eliminate the stress on the seed crystal and the grown crystal.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and has been known in the course of growing a II-VI compound semiconductor crystal on a seed crystal by a sublimation method or a halogen chemical transport method and cooling the same. An object of the present invention is to provide a crystal growth method for a II-VI group compound semiconductor crystal having excellent crystallinity by suppressing stress from the support member to a seed crystal caused by a difference in thermal expansion coefficient between the support member and the seed crystal. It is.

[0009]

The present invention has succeeded in solving the above problems by employing the following constitution. (1) A method in which a raw material polycrystal is placed in a growth chamber and a II-VI compound semiconductor crystal is grown on the seed crystal by a sublimation method or a halogen chemical transport method. A method of growing a II-VI compound semiconductor crystal, comprising interposing a buffer film that does not adhere to the supporting member of the above (1) between the seed crystal and the seed crystal supporting member. (2) In addition to the seed crystal and the seed crystal support member, also on the surface of the contact portion of the member that contacts the growth crystal, a buffer film that does not adhere to the contact portion of the member during the cooling process after crystal growth. A method for growing a II-VI group compound semiconductor crystal, wherein the crystal is interposed.

(3) The buffer film is made of a material that does not decompose, melt, or sublime in a crystal growth environment, does not react with the seed crystal and the seed crystal supporting member, and does not react with halogen. The method for growing a group II-VI compound semiconductor crystal according to the above (1) or (2), wherein (4) The buffer film is made of carbon, carbide such as silicon carbide, nitride such as silicon nitride, aluminum nitride, boron nitride, oxide such as aluminum oxide, zinc oxide, or platinum, iridium, tungsten, or the like. II- described in the above item (3), characterized in that it is made of one of metals or a combination of two or more of the above materials.
A method for growing a group VI compound semiconductor crystal. (5) Any one of the above (1) to (4), wherein a portion of the seed crystal supporting member that contacts the seed crystal and a surface of the seed crystal on the seed crystal supporting member side are smooth planes. A method for growing a group II-VI compound semiconductor crystal according to any one of the first to third aspects.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method for growing a II-VI compound semiconductor crystal on a seed crystal by a sublimation method or a halogen chemical transport method. In addition, by interposing a buffer film that can be freely laterally displaced with respect to the seed crystal support member or easily peels between the seed crystal and the seed crystal support member, the stress from the seed crystal support member is greatly reduced. This makes it possible to eliminate the deterioration of the crystallinity of the seed crystal and the grown crystal.

In the present invention, during the cooling process, the buffer film can be freely shifted laterally without adhering to the seed crystal supporting member. Therefore, the stress caused by the difference in thermal expansion coefficient between the seed crystal and the seed crystal supporting member and the difference in its temperature dependency can be eliminated by the relative lateral displacement between the buffer film and the seed crystal supporting member. However, there is a little stress from the buffer film to the seed crystal, but the buffer film is thin enough,
For example, if the thickness is set to 100 μm or less, the stress is practically negligible.

[0013] The buffer film may be prepared by coating the buffer film on the seed crystal support member under conditions that allow it to be peeled off very easily by thermal cycling, or by forming a separately prepared film on the seed crystal and the seed crystal support member. It may be sandwiched between.

When the grown crystal does not come into contact with the growth vessel wall or the like, it is only necessary to provide a buffer film between the seed crystal and the seed crystal support member as described above, but the grown crystal comes into contact with the growth vessel wall or the like. In such a case, the stress on the crystal can be effectively reduced by interposing a similar buffer film also at a portion that comes into contact with the growth vessel wall or the like.

The material of the buffer film is such that it does not decompose, melt or sublime in the crystal growth environment, does not react with the seed crystal and the seed crystal supporting member, and reacts with the halogen in the halogenated transport method. It is necessary to select a material that does not. Specifically, carbide such as carbon and silicon carbide, nitride such as silicon nitride, aluminum nitride, and boron nitride, oxide such as aluminum oxide and zinc oxide, or metal such as platinum, iridium, and tungsten is used. Can be.

Further, if there is a gap between the back surface of the seed crystal and the buffer film, the seed crystal component is sublimated between them and chemically transported to deteriorate the crystallinity of the seed crystal and the grown crystal. It is necessary to process the portion of the seed crystal supporting member that contacts the seed crystal and the back surface of the seed crystal into a smooth plane so that the seed crystal can be contacted without any gap.

[0017]

EXAMPLE Comparative Example 1 A ZnSe single crystal was grown using the apparatus shown in FIG. Seed crystal is 20mm in diameter and 1m in thickness
A (111) B-plane ZnSe single crystal wafer whose surface was mirror-polished and the back surface was lapped and polished with m was used. The dislocation density of the seed crystal measured beforehand by etching with NaOH was 5 × 10 ⁴ cm ^{−2 to} 1.5 × 10 ⁵ cm ⁻² .
Then, on the bottom surface of a vertical quartz ampoule having an inner diameter of 22 mm, a quartz columnar seed crystal support member having a diameter of 20 mm and a length of 60 mm and having an end surface polished smoothly was placed, and the seed crystal was placed on the smooth end surface. 30 mm above the seed crystal
, A mesh for holding a raw material was arranged, and 20 g of ZnSe polycrystal was mounted thereon as a raw material. Then, the ampule was evacuated to 1 × 10 ⁻⁷ Torr, and then argon gas was introduced at 20 Torr, and the ampule was sealed with a sealing lid.

The ampoule was inserted into a vertical tube furnace, and the temperature of the polycrystalline raw material was set to 1100 ° C. and the temperature of the seed crystal was set to 1080.
And the temperature at the lower end of the ampoule to 1000 ° C.
Crystal growth was performed for days. In this crystal growth, the seed crystal is locally cooled by radiant cooling through the quartz cylinder, and the crystal can grow on the seed crystal without contacting the ampoule wall, which has become relatively hot. Therefore, in the crystal cooling process, no external stress is applied to the grown crystal from a portion other than the rear surface of the seed crystal. The obtained crystal had a weight of 17.2 g and did not contain voids, but the dislocation density of the seed crystal was 4 × 1.
0 ⁵ cm ^{−2 to} 6 × 10 ⁵ cm ⁻² , and the dislocation density of the grown crystal is also 1 × 10 ⁵ cm ⁻² to 4 × 10 ⁵ c due to the influence.
It showed a high value of m ^-2 . This is considered to be because the seed crystal was strongly attached to the quartz seed crystal supporting member, and thus stress was applied to the seed crystal during the cooling process.

Comparative Example 2 Using the apparatus of FIG.
A single crystal was grown. The seed crystal has a diameter of 20 mm and a thickness of 1
A (111) B-plane ZnSe single crystal wafer whose front surface was mirror-polished and its back surface was lapped and polished in mm. The dislocation density of the seed crystal measured beforehand by etching with NaOH was 5 × 10 ⁴ cm ^{−2 to} 1.5 × 10 ⁵ cm ⁻² .
On a surface of a cylindrical columnar seed crystal support member made of quartz having a diameter of 20 mm, a length of 60 mm and a smooth end face, a carbon film having a thickness of 1000 mm was formed in advance at 1100 ° C. by a thermal CVD method using benzene as a raw material. The seed crystal was placed thereon.

The quartz columnar seed crystal supporting member was placed on the bottom surface of a quartz ampoule having an inner diameter of 22 mm which was vertically arranged, and the seed crystal was placed on the smooth end face. Further, a mesh for holding a raw material was arranged at a position 30 mm above the seed crystal, and 20 g of ZnSe polycrystal was placed thereon as a raw material. Then, the ampule was evacuated to 1 × 10 ⁻⁷ Torr, and then argon gas was introduced at 20 Torr, and the ampule was sealed with a sealing lid.

The ampoule was inserted into a vertical tube furnace, and the temperature of the polycrystalline raw material was set to 1100 ° C. and the temperature of the seed crystal was set to 1080.
And the temperature at the lower end of the ampoule to 1000 ° C.
Crystal growth was performed for days. Even after cooling, the carbon film was in close contact with the quartz cylinder, and no peeled portion was seen. The grown crystal weighed 18.5 g and did not contain voids, but the dislocation density of the seed crystal was 2 × 10 ⁵ cm ^{−2 to} 5 × 10 ⁵ c.
m ^-2 is increased, resulting in a high dislocation density ^{1 × 10 5 cm -2 ~2.5 ×} 10 5 cm -2 in the growing crystal at the impact. Compared with Comparative Example 1 in which a seed crystal is directly mounted on quartz, the adhesion strength of the seed crystal to the carbon film is low, but it is considered that the stress cannot be completely suppressed.

[Embodiment 1] Using the apparatus shown in FIG.
A single crystal was grown. The seed crystal has a diameter of 20 mm and a thickness of 1
A (111) B-plane ZnSe single crystal wafer whose front surface was mirror-polished and its back surface was lapped and polished in mm. The dislocation density of the seed crystal measured beforehand by etching with NaOH was 5 × 10 ⁴ cm ^{−2 to} 1.5 × 10 ⁵ cm ⁻² .
900 ° C. on the surface of a quartz columnar seed crystal supporting member having the same shape as that of Comparative Example 2 by a thermal CVD method using benzene in advance.
To form a carbon film having a thickness of 4000 °, and the seed crystal was mounted thereon.

The seed crystal supporting member was placed on the bottom surface of a vertically arranged quartz ampoule having an inner diameter of 22 mm, and the seed crystal was placed on its smooth end face. Further above the seed crystal 30
A raw material holding mesh was placed at a position of mm, and 20 g of ZnSe polycrystal was placed thereon as a raw material. After evacuating the ampoule to 1 × 10 ⁻⁷ Torr,
Argon gas was introduced at 20 Torr, and sealing was performed at the sealing lid.

The ampoule was inserted into a vertical tube furnace, and the temperature of the polycrystalline raw material was set to 1100 ° C. and the temperature of the seed crystal was set to 1080.
And the temperature at the lower end of the ampoule to 1000 ° C.
Crystal growth was performed for days. After cooling, the carbon film had many cracks, and peeled off like a wrinkle from the quartz cylinder. Unlike the film forming conditions of Comparative Example 2, the film was formed at a low film forming temperature, so that the bonding strength of carbon to quartz was weak, and the film was thick and easily affected by a difference in coefficient of thermal expansion. It is thought that it was done. The grown crystal weighed 17.5 g and did not contain voids, and the dislocation density of the seed crystal was 5 × 10 ⁴ cm ^{−2 to} 1.5 × 1.
0 ⁵ cm ^-2 and the crystal growth before the state was maintained. It is considered that the dislocation did not multiply because the seed crystal almost became stress-free due to the carbon film peeling from the quartz during cooling. As a result, the dislocation density of the grown crystal becomes 1
It was able to be reduced to × 10 ⁴ cm ⁻² to 8 × 10 ⁴ cm ⁻² . The thickness of the carbon film formed on the seed crystal supporting member at the time of film formation is 2,000 to 15,000, preferably 300 to 5,000.
Within the range of 0 ° to 8000 °, there was no peeling immediately after film formation, and the carbon film was easily peeled from quartz during the cooling process after crystal growth, and the dislocation density of the grown crystal was low, and the same effect was obtained. .

[Embodiment 2] Using the apparatus of FIG.
A single crystal was grown. The seed crystal has a diameter of 10 mm and a thickness of 1
A (111) B-plane ZnSe single crystal wafer whose front surface was mirror-polished and its back surface was lapped and polished in mm. The dislocation density of the seed crystal measured beforehand by etching with NaOH was 5 × 10 ⁴ cm ^{−2 to} 1.5 × 10 ⁵ cm ⁻² .
An outer diameter of 12 mm is placed on the bottom of a quartz ampoule with an inner diameter of 12 mm.
After installing a pBN member formed in a cup shape having a thickness of 5 mm, a length of 40 mm, and a thickness of 5 μm, the seed crystal was placed on the bottom surface of the cup member. Further, a mesh for holding a raw material was placed at a position 60 mm above the seed crystal, and 10 g of ZnSe polycrystal was mounted thereon as a raw material. Then, the ampule was evacuated to 1 × 10 ⁻⁷ Torr, and then argon gas was introduced at 20 Torr, and the ampule was sealed with a sealing lid.

The ampoule was inserted into a vertical tube furnace, and the temperature of the polycrystalline raw material was set to 1100 ° C. and the temperature of the seed crystal was set to 1080.
The crystal was grown by heating to 10 ° C for 10 days. As a result, a grown crystal having a weight of 13.2 g was obtained. After cooling, the pBN member and the quartz ampule were not fixed, and smooth lubricity was maintained. Although some voids were included inside the crystal, the dislocation density was 5 × for both the seed crystal and the grown crystal.
10 ⁴ cm ^{−2 to} 1.5 × 10 ⁵ cm ⁻² , and no increase from the dislocation density level before growth was observed. The pBN
When the thickness of the manufactured member is in the range of 2 μm or more and 100 μm or less, preferably 3 μm or more and 50 μm or less, the stress on the seed crystal and the grown crystal is practically negligible, and the same effect is obtained.

In the above embodiment, the growth of ZnSe crystals in an argon gas atmosphere by sublimation has been described, but the present invention is not limited to this. Other II-
The same applies to the growth of a group VI compound semiconductor crystal by the sublimation method. The growth atmosphere is not only an inert gas atmosphere such as an argon gas, but also a group II or V using a reservoir.
It is easily adaptable to growth in a Group I atmosphere.

[0028]

According to the present invention, by adopting the above-described constitution, II-
In the process of growing the group VI compound semiconductor crystal on the seed crystal and cooling the same, external stress can be reduced, and a II-VI group compound semiconductor crystal having excellent crystallinity can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an ampoule for crystal growth used in Example 1 and Comparative Example 2.

FIG. 2 is a schematic sectional view of an ampoule for crystal growth used in Example 2.

FIG. 3 is a schematic cross-sectional view of a crystal growth ampule used in Comparative Example 1.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G077 AA02 BE22 BE25 BE26 DA18 DA19 ED06 5F045 AA03 AB06 AB07 AB09 AB22 AB23 AB33 AD13 AD15 AF06 AF12 AF13 DA69 DQ01 DQ08 5F103 AA10 DD21 DD23 GG01 HH03 RR06

Claims (5)

[Claims] In a method of arranging a source polycrystal in a growth chamber and growing a II-VI compound semiconductor crystal on a seed crystal by a sublimation method or a halogen chemical transport method, the method comprises the steps of: A method of growing a II-VI compound semiconductor crystal, wherein a buffer film that does not adhere to a seed crystal support member is interposed between the seed crystal and the seed crystal support member. 2. In addition to the space between the seed crystal and the seed crystal support member, the surface of the contact portion of the member that comes into contact with the grown crystal,
II-VI characterized by interposing a buffer film which does not adhere to the contact portion of the member in a cooling process after crystal growth.
A method for growing a group III compound semiconductor crystal. 3. The buffer film is made of a material that does not decompose, melt, or sublime in a crystal growth environment, does not react with the seed crystal and the seed crystal support member, and does not react with halogen. The method for growing a II-VI compound semiconductor crystal according to claim 1, wherein: 4. The buffer film is made of a carbide such as carbon and silicon carbide, a nitride such as silicon nitride, aluminum nitride and boron nitride, an oxide such as aluminum oxide and zinc oxide, or platinum, iridium and tungsten. 4. The method for growing a II-VI compound semiconductor crystal according to claim 3, wherein the method comprises a metal selected from the group consisting of any one of the above metals and a combination of two or more of the above materials. 5. The seed crystal supporting member according to claim 1, wherein a portion of the seed crystal supporting member in contact with the seed crystal and a surface of the seed crystal on the side of the seed crystal supporting member are smooth planes. 2. The method for growing a II-VI group compound semiconductor crystal according to item 1.