JP2974023B1 - Method of growing II-VI compound semiconductor crystal - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide a seed crystal by sublimation or halogen chemical transport
When growing a II-VI compound semiconductor crystal, the stress applied to the seed crystal from the support member is suppressed, and a crystal growth method of a II-VI compound semiconductor crystal having excellent crystallinity is provided. is there. SOLUTION: In a method of arranging a raw material 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, a back surface of the seed crystal is previously smoothed in advance. In addition, the seed crystal support member is made of a material that is substantially transparent to visible light and / or infrared light, and at least one end of the support member is finished to a smooth surface, and visible light and / or red light passing through the smooth surface. The supporting member is configured such that the effective transmittance of external light is high in the central portion and low in the peripheral portion, and crystal growth is performed by closely contacting the smooth surface of the seed crystal on the smooth surface of the supporting member. II-VI characterized by
This is a method for growing a group III compound semiconductor crystal.

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 group compound semiconductor crystal such as CdS.

[0002]

2. Description of the Related Art II-VI 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, Physical Vapor Transport method) in which crystal growth is performed by utilizing the sublimation and coagulation of the raw material, and a method in which a halogen is produced by reacting a halogen with the raw material. Halogen chemical transport method (CVT method, Chemical method) for transporting halides onto seed crystals to decompose and grow crystals
VaporTransport method).

[0003] For example, J. Crystal Growth 94 (1989) p.
1 to 5, a quartz ampoule was filled with 5 g of ZnSe powder raw material at one end and a ZnSe single crystal seed crystal was placed at the other end, the ampule was sealed, and the ampule was heated to raise the temperature of the ZnSe powder side to about 1080 ° C. The temperature on the seed crystal side is about 1070 ° C
It has been reported that a ZnSe crystal was grown on a seed crystal by setting to.

Incidentally, in a crystal growth method for growing a II-VI compound semiconductor crystal on a seed crystal by a sublimation method or a halogen chemical transport method, the seed crystal or the grown crystal adheres to surrounding members when the grown crystal is cooled. However, a stress is applied to the grown crystal due to the difference in the coefficient of thermal expansion between the grown crystal and the member, and the crystallinity deteriorates.

[0005] In the vapor phase growth method, if there is a portion around the seed crystal at a temperature lower than that of the seed crystal, the seed crystal itself is transported to the low temperature portion, thereby deteriorating the crystallinity of the seed crystal and generating voids. I do. In some cases, it causes polycrystallization.
The decrease in the crystallinity of the seed crystal is inherited by the crystal growing thereon, thereby reducing its crystallinity. Therefore, it is necessary to protect the seed crystal in the vapor phase growth, and it is important to prevent the component transport of the seed crystal itself by installing the seed crystal at least in the local lowest temperature part in the growth chamber.

Further, the grown crystal usually grows in contact with the wall of the growth vessel.
Stress caused by the difference in the thermal expansion coefficient between the grown crystal and the growth vessel, and between the grown crystal and the seed crystal supporting member is applied to the crystal at the contact surface, causing deterioration in crystallinity such as an increase in dislocation density.

In order to solve these problems, a method has been proposed in which a seed crystal is mounted on a rod-shaped seed crystal supporting member made of a transparent material to grow the crystal (J. Crystal Gr.).
owth, Vol. 161, (1996), p. 51-59; Yu. V. Korostelin). FIG. 3 is a conceptual diagram of an apparatus for performing the above method. In this method, only the seed crystal is locally cooled and held on the surrounding vessel wall by radiant cooling through the transparent seed crystal support member to the lower temperature part. For this reason, the seed crystal can be located at a thermally stable position, the transport of the component of the seed crystal to the surroundings can be prevented, and the seed crystal can be held without deterioration.

Further, according to this method, since the vessel wall can be maintained at a sufficiently high temperature, the grown crystal can be grown without contact with the surrounding vessel wall. Then, in this growth method, the stress applied to the crystal is considerably reduced as compared with the case where the grown crystal is in contact with the container wall since the grown crystal is only in contact with another material via the back surface of the seed crystal.

However, since the entire back surface of the seed crystal is in close contact with the supporting member, a stress due to the difference in the coefficient of thermal expansion between the two is applied to the seed crystal during the cooling of the grown crystal. Due to this stress, the dislocation density increases in the seed crystal portion, and the dislocation propagates to the grown crystal. In the vapor phase growth, since the aspect ratio (crystal length / crystal diameter) of the crystal shape is usually small and the crystal length is short, dislocations from the seed crystal portion propagate to a considerable portion of the grown crystal, and the crystallinity is reduced. In addition, depending on the growth conditions, the crystal grows so as to embrace the seed crystal supporting member, and receives a large stress at the embraced portion.

[0010]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and has been disclosed in which a seed crystal is supported by a transparent support member, and II-VI is applied on the seed crystal by sublimation or halogen chemical transport.
When growing a group III compound semiconductor crystal, the stress applied to the seed crystal from the support member is suppressed, and excellent crystallinity II
It is intended to provide a method for growing a group VI compound semiconductor crystal.

[0011]

The present invention has succeeded in solving the above problems by employing the following constitution. (1) placing a source polycrystal in a growth chamber, in a method of growing a II-VI group compound semiconductor crystal on a seed crystal by sublimation or halogen chemical transport method, the back surface of the seed crystal is previously finished to be smooth. The seed crystal support member is made of a material that is substantially transparent to visible light and / or infrared light, and at least one end of the support member is finished to have a smooth surface, and visible light and / or infrared light passing through the smooth surface. The support member is configured such that the effective transmittance of light is high in the central portion and low in the peripheral portion,
A method for growing a II-VI compound semiconductor crystal, wherein crystal growth is performed by bringing a smooth surface of the seed crystal into close contact with a smooth surface of the support member.

(2) The support member according to (1), wherein the support member is provided with a circumferential groove-shaped cut in a side surface thereof to form a distribution of the effective transmittance of the light. -A method of growing a group VI compound semiconductor crystal. (3) The supporting member has a rod having the relatively high transmittance inserted into a thick pipe having a relatively low transmittance of visible light and / or infrared light, and the transmission member having smooth both surfaces at an upper end thereof. A II-VI group compound semiconductor crystal according to (1), wherein a disk having a relatively high ratio is placed on the disk, and the smooth surface of the seed crystal is brought into close contact with the disk to grow the crystal. Growth method. (4) The II- according to any one of (1) to (3), wherein an adhesion preventing coating film is interposed on a contact surface between the support member or the disc and the seed crystal. A method for growing a group VI compound semiconductor crystal.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is directed to a seed crystal supporting member, in which the effective transmittance of visible light and / or infrared light of the seed crystal supporting member viewed from the seed crystal is high at the center and low at the periphery. By configuring the support member, the above problem was successfully solved.
FIG. 1 shows an embodiment of the present invention, in which a seed crystal supporting member is polished by making a notch in a lower part of a polishing surface on which a seed crystal is placed so as to have a constriction. At the center of the surface, high transmittance of visible light and / or infrared light is maintained, and at the periphery, the transmittance is reduced by being scattered by a constricted portion. By employing the above configuration, the cooling of the seed crystal supporting member due to radiation to the lower low-temperature portion is strong at the central portion of the seed crystal and weak at the peripheral portion, and the peripheral portion of the crystal has a relatively high temperature. As a result, of the portion in contact with the seed crystal supporting member, the peripheral portion of the crystal sublimates and disappears, and the seed crystal comes into contact with the seed crystal supporting member substantially only at the center of the back surface, and the contact area is reduced. Thereby, the stress at the time of cooling is reduced, and the crystallinity of the grown crystal can be improved.

The material of the seed crystal supporting member is a material that does not decompose, melt, or sublime in a crystal growth environment, does not react with the seed crystal, and does not react with halogen in the halogen chemical transport method. In addition, it must be made of a material that is substantially transparent to visible light and / or infrared light. Specifically, it can be made of quartz glass, magnesia, quartz, sapphire, or the like.

The shape of the seed crystal supporting member should be axially symmetric with respect to a straight line passing through the center of the smooth surface and intersecting perpendicularly to the smooth surface from the viewpoint of maintaining the symmetry of the thermal environment. Is desirable. Further, in order to alleviate the adhesion of the seed crystal to the support member, it is also effective to coat the surface of the seed crystal support member with a relaxation film. This coating film reduces the adhesion strength of the seed crystal and, at the same time, separates from the seed crystal support member during cooling, so that an effect of stress relaxation is expected. Like the seed crystal support member, the coating film is also made of a material that does not decompose, melt, or sublime in the crystal growth environment, does not react with the seed crystal, and does not react with halogen in the halogen chemical transport method. Must be chosen. As such a coating film, carbides such as carbon and silicon carbide, nitrides such as silicon nitride, aluminum nitride and boron nitride, and oxides such as aluminum oxide and zinc oxide can be used.

[0016]

EXAMPLE Comparative Example A ZnSe single crystal was grown using the apparatus shown in FIG. Seed crystal is 20mm in diameter and 1mm in thickness
The surface was mirror polished and the back was lap polished (11
1) A ZnSe single crystal wafer on the B side was used. NaO in advance
The dislocation density of the seed crystal measured by etching with H is 5 ×
It was 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. 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. The obtained crystal has a bottom diameter of 2
Although it was 0 mm, weighed 17.2 g, and did not contain voids, it grew by partially embracing the seed crystal support member.
As a result, the dislocation density of the seed crystal is 4 × 10 ⁵ cm ^{−2 to} 6 ×
Has increased to 10 ⁵ cm ^-2, was high dislocation density ^{1 × 10 5 cm -2 ~4 ×} 10 5 cm -2 in the growing crystal at the impact. This is considered to be because the seed crystal was strongly attached to the quartz seed crystal supporting member and the seed crystal was embraced, so that stress was applied to the seed crystal during the cooling process.

[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
mm, the front surface was mirror-polished and the back surface was lapped.
A (111) B plane ZnSe single crystal wafer was used. Na in advance
The dislocation density of the seed crystal measured by etching with OH 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, the end face was polished smoothly with a diameter of 20 mm and a length of 60 mm, and a circumferential cut was made at a position 5 mm from the polished surface so that the diameter became 8 mm. A columnar seed crystal support member was provided, 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. The obtained crystals had a weight of 15.5.
g, containing no voids, and the bottom surface in contact with the seed crystal support member had a diameter of about 12 mm, and the diameter increased as it grew to a maximum of about 20 mm. The dislocation density of the seed crystal is 1 × 10 ⁵ cm ^{−2 to} 3 × 10 ⁵
cm ⁻² , but the dislocation density of the grown crystal was 2 × 1
0 ⁴ was reduced to ^{cm -2 ~1 × 10 5 cm -2} . . This is because the attachment area between the quartz seed crystal support member and the seed crystal is small, and there was no hiding of the seed crystal support member,
It is considered that the stress applied to the seed crystal during the cooling process was low. In addition, since the crystal diameter increases from the seed crystal to the grown crystal, it is considered that the increase in the dislocation density of the grown crystal was suppressed even if the dislocation propagated from the seed crystal.

[Embodiment 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
mm, the front surface was mirror-polished and the back surface was lapped.
A (111) B plane ZnSe single crystal wafer was used. Na in advance
The dislocation density of the seed crystal measured by etching with OH was 5
× 10 ⁴ cm ^{-2 to} 1.5 × 10 ⁵ cm ^-2 . On the surface of a cylindrical columnar seed crystal support member made of quartz having the same shape as in Example 1, a thickness of 300 was previously formed by a thermal CVD method using benzene as a raw material.
A 0 ° carbon film was formed, and the seed crystal was mounted thereon. The seed crystal support 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 thereon. Further, a mesh for holding the raw material is arranged at a position 30 mm above the seed crystal, and Zn is placed thereon as a raw material.
20 g of Se polycrystal was placed. And this ampule is 1
After evacuation to × 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. The obtained crystals had a weight of 16.3.
g, containing no voids, and the bottom surface in contact with the seed crystal support member had a diameter of about 12 mm, and the diameter increased as it grew to a maximum of about 20 mm. The dislocation density of the seed crystal is 5 × 10 ⁴ cm ^{−2 to} 1.5 × 1
There was almost no increase at 0 ⁵ cm ^-2 , and the dislocation density of the grown crystal was reduced to 1 x 10 ⁴ cm ^{-2 to} 5 x 10 ⁴ cm ^-2 . . This is because the adhesion area between the seed crystal support member made of quartz and the seed crystal is small, the adhesion strength is reduced by the carbon film, and the seed crystal support member is not entangled, so that the stress applied to the seed crystal in the cooling process is low. It is thought that it was. In addition, since the crystal diameter increases from the seed crystal to the grown crystal, it is considered that the increase in the dislocation density of the grown crystal was suppressed even if the dislocation propagated from the seed crystal.

Embodiment 3 Using the apparatus of FIG.
A single crystal was grown. The seed crystal has a diameter of 20 mm and a thickness of 1
mm, the front surface was mirror-polished and the back surface was lapped.
A (111) B plane ZnSe single crystal wafer was used. Na in advance
The dislocation density of the seed crystal measured by etching with OH was 5
× 10 ⁴ cm ^{-2 to} 1.5 × 10 ⁵ cm ^-2 . Then, in a quartz pipe having an outer diameter of 20 mm, an inner diameter of 7.5 mm, a length of 60 mm and a smooth end face, a diameter of 7 mm,
A sapphire rod having a length of 60 mm and an end face polished smoothly is inserted, and a sapphire disc polished on both sides with a diameter of 20 mm and a thickness of 5 mm on both sides is used as a seed crystal support member. It was set on the bottom surface of the placed quartz ampoule having an inner diameter of 22 mm. Since the transmittance of infrared light of sapphire is higher than that of quartz, the light transmittance of the central portion of the seed crystal supporting member is higher than that of the peripheral portion. Then, in order to prevent the attachment of the seed crystal, a carbon film having a thickness of 1500 ° was formed on a sapphire disk by a thermal CVD method using benzene as a raw material, and the seed crystal was mounted thereon. The seed crystal supporting member was set on the bottom surface of a vertically arranged quartz ampoule having an inner diameter of 22 mm. Further, at a position 30 mm above the seed crystal,
A mesh for holding the raw material is arranged, and Z
20 g of nSe polycrystal was loaded. 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. The obtained crystals had a weight of 15.3.
g, containing no voids, and the bottom surface in contact with the seed crystal support member had a diameter of about 10 mm, and the diameter increased with growth to a maximum of about 20 mm. The dislocation density of the seed crystal is 5 × 10 ⁴ cm ^{−2 to} 1.5 × 1
There was almost no increase at 0 ⁵ cm ^-2 , and the dislocation density of the grown crystal was reduced to 1 x 10 ⁴ cm ^-2 to 4 x 10 ⁴ cm ^-2 . This is because the adhesion area between the seed crystal support member made of quartz and the seed crystal is small, the adhesion strength is reduced by the carbon film, and the seed crystal support member is not entangled, so that the stress applied to the seed crystal in the cooling process is low. It is thought that it was. In addition, since the crystal diameter increases from the seed crystal to the grown crystal, it is considered that the increase in the dislocation density of the grown crystal was suppressed even if the dislocation propagated from the seed crystal.

[0024]

According to the present invention, by adopting the above structure, the sublimation method and / or the halogen chemical transport method can be used.
In the process of growing a group-VI compound semiconductor crystal on a seed crystal and cooling it, external stress can be reduced, and a group II-VI compound semiconductor crystal having excellent crystallinity can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a crystal growth ampule used in Examples 1 and 2.

FIG. 2 is a schematic sectional view of a crystal growth ampule used in Example 3.

FIG. 3 is a schematic sectional view of a crystal growth ampule used in a comparative example.

──────────────────────────────────────────────────続 き Continued on the front page (56) References Yu. V. Korostein et al. , "Vapour growth and characteristics of bulk ZnSe single crystals," Journal of Crystal Growth, Vol. 161, 1996, pp. 51-59 (58) Field surveyed (Int. Cl. ⁶ , DB name) C30B 1/00-35/00 H01L 21/363

Claims (4)

(57) [Claims] 1. 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, wherein a back surface of the seed crystal is smoothed in advance. Finished, the seed crystal support member is made of a material that is substantially transparent to visible light and / or infrared light, and at least one end of the support member is finished to a smooth surface, and visible light and / or The support member is configured such that the effective transmittance of infrared light is high in the center portion and low in the peripheral portion, and crystal growth is performed by closely contacting the smooth surface of the seed crystal on the smooth surface of the support member. II-VI characterized by the following:
A method for growing a group III compound semiconductor crystal. 2. The II-VI according to claim 1, wherein said support member is provided with a circumferential groove-shaped notch on a side surface thereof to form a distribution of an effective transmittance of said light. A method for growing a group III compound semiconductor crystal. 3. The supporting member has a rod having the relatively high transmittance inserted into a thick pipe having a relatively low transmittance of visible light and / or infrared light, and has a smooth upper surface at both ends. The II-VI group compound semiconductor according to claim 1, wherein the disk having the relatively high transmittance is mounted thereon, and crystal growth is performed by bringing a smooth surface of the seed crystal into close contact with the disk. Crystal growth method. 4. The II according to claim 1, wherein an adhesion preventing coating film is interposed on a contact surface between the support member or the disk and the seed crystal.
-A method of growing a group VI compound semiconductor crystal.