JP3011214B1 - Method of growing II-VI compound semiconductor crystal - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide a seed crystal by a sublimation method or a halogen chemical transport method.
It is an object of the present invention to provide a crystal growth method capable of stably growing a crystal having excellent crystallinity with good reproducibility when growing a II-VI compound semiconductor crystal. SOLUTION: A columnar seed crystal support member is fixed to one end of a growth chamber, and the growth chamber and the support member are made of a material that is stable under a crystal growth environment and transparent to visible light and / or infrared light. An end surface opposite to the fixed end of the support member is formed as a smooth plane, a seed crystal is held thereon, and a gap between the support member and the growth chamber wall is closed at an intermediate portion of the support member to form an airtight portion, Gas in the growth chamber is prevented from flowing toward the fixed end of the support member, and the temperature Te of the fixed end of the support member is reduced to the temperature Td of the hermetic portion.
This is a method for growing a II-VI group compound semiconductor crystal, characterized in that the crystal is grown while keeping the temperature lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method of sublimation or halogen chemical transport on ZnSe, ZnS, CdT on a seed crystal.
The present invention relates to a method for growing a II-VI group compound semiconductor crystal such as e, CdS or the like.

[0002]

2. Description of the Related Art II-VI compound semiconductor crystal growth methods are roughly divided into melt growth method, solid phase growth method, solution growth method,
It is classified into four types of vapor phase growth methods. Among them, the vapor phase growth method includes a sublimation method (PVT method, Physical Vapor Transport method) in which a material is sublimated and crystallized to grow a crystal,
And halogen react with the raw material to produce the raw material halide, and use the chemical transport method (CVT method, Ch
emical Vapor Transport method).

[0003] For example, J. Crystal Growth 94 (1989) p.
1-5, the raw material ZnSe powder 5
g, a ZnSe single crystal is placed at the other end as a seed crystal of a grown crystal, and sealed to produce an ampule. This ampoule is heated and the temperature of the ZnSe raw material powder side is set to about 1080
By setting the temperature on the seed crystal side to 1070 ° C., the raw material is transported to the seed crystal side, and the ZnSe crystal is grown on the seed crystal.

[0004] In the vapor phase growth method, when a portion at a lower temperature than the seed crystal is present in the ampoule, a part of the seed crystal is sublimated, transported to the low temperature portion and deposited. As a result, the seed crystal is deteriorated or voids are generated, and in some cases, complete polycrystallization is caused. Such a decrease in the crystallinity of the seed crystal is inherited by the crystal grown thereon, and reduces the crystallinity of the grown crystal. Therefore, in the vapor phase growth method, in order to protect the seed crystal, it is important to prevent the sublimation of the seed crystal by locating the seed crystal at least at the local lowest temperature part in the ampoule.

As a method for solving this problem, there has been proposed a method of growing a crystal while holding a seed crystal on a rod-shaped support member made of a transparent material (J. Crystal Growth, V.
ol. 161, (1996), 51-59; Yu. V. Korostelin). FIG. 2 is a schematic diagram for explaining the method. Even if the seed crystal support member is arranged by providing a slight gap with the inner wall of the ampoule and radiatively cooled down the ampoule through the transparent seed crystal support member, even if the wall surface of the ampoule is kept at a high temperature,
The seed crystal on the support member can be locally cooled and held. As a result, the seed crystal can be located at a thermally stable position, and sublimation deterioration of the seed crystal can be prevented. Further, since the temperature of the ampoule wall surface can be made sufficiently high, the grown crystal can be grown without coming into contact with the ampoule wall surface. The gaseous raw material that has passed through the gap between the seed crystal support member and the inner wall of the ampoule crystallizes in the lowest temperature portion below the ampoule. As described above, since the grown crystal only comes into contact with the support member on the back surface of the seed crystal, the stress applied to the crystal is greatly reduced compared to the method in which the grown crystal comes into contact with the growth vessel wall, and a crystal with excellent crystallinity is obtained. It is possible to grow.

The present inventor has proposed that in the above method, as a method for stably maintaining the seed crystal and preventing the deterioration of crystallinity, control is performed so as to satisfy the following equation (Japanese Patent Application No. 9-1997).
No. 314978). (Ps−Pd) / (L ₁ + L ₂ ) ≧ (Pc−Pd) / L ₂ (1) where Ps, Pc, and Pd are polycrystalline material positions, seed crystal positions, and crystal growth at the lowest temperature part, respectively. It is the equilibrium partial pressure of the component that controls the speed, and L ₁ and L ₂ are the distance between the polycrystalline raw material and the seed crystal and the distance between the seed crystal and the lowest temperature part, respectively. When the relationship of Expression (1) is satisfied, the partial pressure gradient between the raw material and the lowest temperature part becomes larger than the partial pressure gradient between the seed crystal and the lowest temperature part. Therefore, the substance transported to the lowest temperature part is substantially supplied from the raw material, and transport or sublimation from the seed crystal and the growing crystal does not occur while the raw material remains, and the seed crystal and The grown crystal can be held stably. In other words, it is possible to prevent the seed crystal from deteriorating in crystallinity and to prevent voids from entering the inside of the crystal, and to grow a crystal having good crystallinity.

However, in the conventional ampoule structure, it is quite difficult to actually realize the temperature distribution as shown in the equation (1), the variation due to the individual difference of the crystal growth furnace is large, and the same furnace and the same condition are used. However, reproducibility was not sufficient even if the crystal was grown by using the method described above. As a result, the seed crystal was sometimes degraded or the grown crystal sometimes contained voids.

[0008]

Accordingly, the present invention solves the above-mentioned problems and provides a method for growing a group II-VI compound semiconductor crystal on a seed crystal by a sublimation method or a halogen chemical transport method.
An object of the present invention is to provide a crystal growth method which enables stable and reproducible growth of a crystal having excellent crystallinity.

[0009]

The present invention has succeeded in solving the above problems by employing the following constitution. (1) A method in which a source polycrystal and a seed crystal are arranged in a growth chamber, and a group II-VI compound semiconductor crystal is grown on the seed crystal by a sublimation method or a halogen chemical transport method. The growth chamber and the support member are made of a material that is stable under a crystal growth environment and is transparent to visible light and / or infrared light, and the fixed end of the support member is fixed. The opposite end face is a smooth plane, holds the seed crystal thereon, closes the gap between the support member and the inner wall of the growth chamber at an intermediate portion of the support member to form an airtight section, and Is prevented from flowing toward the fixed end of the support member, and the temperature T at the fixed end of the support member is prevented.
A method for growing a group II-VI compound semiconductor crystal, comprising: growing a crystal while maintaining e at a temperature lower than the temperature Td of the hermetic portion. (2) An effective temperature (effective temperature of a seed crystal portion) Tc ^* of a smooth plane of the support member is controlled by adjusting a temperature Te of a fixed end of the support member.
(1) The method for growing a group II-VI compound semiconductor crystal according to (1). (3) the method characterized in that a coating film for preventing seed crystal sticking is interposed between the seed crystal and the support member.
The method for growing a group II-VI compound semiconductor crystal according to (1) or (2).

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is intended to prevent sublimation from the surface of a seed crystal when growing a II-VI compound semiconductor crystal on the seed crystal by a sublimation method or a halogen chemical transport method. It is an object of the present invention to provide a crystal growth method for growing a group II-VI compound semiconductor crystal having excellent crystallinity by preventing the crystal growth. Here, in the present invention, the “seed crystal surface” does not mean “front surface” with respect to “back surface”,
“Outer layer” means “inside the crystal”.

In the ampoule having the conventional structure shown in FIG. 2, if the temperature distribution in the furnace shown in FIG. 2 is directly reflected in the temperature distribution in the ampoule, the temperature of the seed crystal portion becomes too high, and the relationship of the equation (1) is lost. Cannot be satisfied. In the ampoule of FIG. 2, the seed crystal is locally cooled by radiation cooling to a lower low-temperature portion through a transparent seed crystal support member, and the effective temperature Tc ^* of the seed crystal portion is set to the furnace temperature near the seed crystal portion. The temperature is kept lower than Tc. Since the equilibrium partial pressure Pc of the crystal component at the seed crystal position is determined by Tc ^* , an equilibrium partial pressure distribution satisfying the expression (1) can be realized inside the ampoule.
Although it is difficult to directly measure the effective temperature Tc ^* of the seed crystal part, it is actually Tc ^* <Tc from the ratio of the raw material transport amount on the seed crystal and the raw material transport amount to the lowest temperature part. Can be confirmed.

Therefore, the effective temperature Tc ^* of the seed crystal portion
Is determined by the temperature Td at the lower end of the seed crystal support member, but since the lower end of the seed crystal support member is also the lowest temperature part in the ampule, Td is simultaneously Pd (equilibrium partial pressure of the lowest temperature part).
Has also been determined. That is, since the adjustment of the furnace temperature distribution changes Pc (equilibrium partial pressure at the seed crystal position) and Pd, the equation (1) is used.
Affect the left side and the right side at the same time, and the left side and the right side cannot be controlled independently. Therefore, the setting range of the furnace temperature distribution condition that can stabilize crystal growth is narrowed,
There was a problem that good crystals could not be grown with good reproducibility.

Therefore, the present invention has solved the above-mentioned problem by employing the ampoule configuration and the temperature distribution shown in FIG. The difference from the conventional method shown in FIG. 2 is that the ampule is sealed at the intermediate portion of the seed crystal supporting member to make it airtight. As for the airtightness method, the ampule may be squeezed as shown in FIG. 1, the columnar support member may be enlarged only at that portion, or an airtight annular member may be inserted. According to this method, the lowest temperature in the growth chamber that determines the equilibrium partial pressure Pd immediately above the hermetic portion is given by the temperature Td of the hermetic portion. On the other hand, the low-temperature portion temperature for determining Tc ^* (effective temperature of the seed crystal portion) by radiant cooling is given by the seed crystal support member lower end portion temperature Te as in the conventional structure. Therefore, Td which determines Pd
In addition, it is easy to separate and control Te that affects Pc, the degree of freedom in setting the temperature is increased, and the controllability of the effective temperature distribution can be greatly improved. That is,
By setting Te <Td, it is possible to lower Tc ^* independently of Td, and to reduce Pc (equilibrium partial pressure at the seed crystal position) without lowering Pd (equilibrium partial pressure immediately above the hermetic portion). It becomes possible. Therefore, the difference between the right side and the left side of the equation (1) can be increased as compared with the conventional ampoule structure, and it becomes easy to realize a crystal growth condition satisfying the equation (1). That is, since the seed crystal and the grown crystal can be locally held at stable positions, it becomes possible to stably grow a crystal having excellent crystallinity. Since this effect is achieved if Te <Td is satisfied, the temperature can be freely set within the range according to each crystal growth condition.

The material of the seed crystal supporting member is such that it does not decompose, melt or sublime in a crystal growth environment, does not react with the seed crystal, does not react with halogen in the halogenated transport method, and does not emit visible light or light. It is necessary to select from materials that are transparent to infrared light. As such a material, quartz glass, magnesia, quartz, sapphire and the like can be used.

In the structure shown in FIG. 1, when the seed crystal adheres to the support member, a stress is generated between the seed crystal and the grown crystal during cooling due to the difference in the coefficient of thermal expansion between the two. Since this stress deteriorates the crystallinity of the seed crystal, it is also important to avoid the above-mentioned sticking. For this purpose, as the material of the seed crystal supporting member, a material that is hardly fixed to the material of the growing crystal can be selected, or a method of applying a coating film for preventing adhesion to the surface of the seed crystal supporting member can be adopted. Similarly to the seed crystal supporting member, the coating film does not decompose or melt under the crystal growth environment, does not sublime, and does not react with the seed crystal and the seed crystal supporting member, and does not react with halogen in the halogenated transport method. You have to choose from. As such a coating film, a carbide such as carbon and silicon carbide, a nitride such as silicon nitride, aluminum nitride, and boron nitride, or an oxide such as aluminum oxide and zinc oxide can be used.

[0016]

EXAMPLES (Comparative Example 1) ZnSe crystals were grown using the apparatus shown in FIG. A quartz rod having a diameter of 21 mm, a length of 100 mm, and both ends polished as a seed crystal support member was set on the bottom surface of a quartz ampoule shaped into a flat bottom with an inner diameter of 22 mm and a length of 220 mm. The seed crystal was a ZnSe single crystal wafer having a diameter of 20 mm, a thickness of 1 mm, a mirror-polished front surface and a lapping-polished back surface, and was placed on the upper surface of a quartz load. And 40mm above the seed crystal
Was provided with a raw material holding mesh, and a total of about 40 g of ZnSe polycrystal of about 5 mm square was placed thereon as a raw material. Next, the ampoule was evacuated to 1 × 10 ⁻⁷ Torr, and then argon gas was introduced at 20 Torr to seal the sealing lid.

The ampoule was placed in a vertical tube furnace, and the temperature of the polycrystalline raw material was set at 1100 ° C. and the temperature of the seed crystal was set at 1080.
C. and the temperature at the lower end of the ampoule was heated to 1000.degree. The obtained crystal has a diameter of 20 at the bottom.
mm, the crystal length was 13 mm, and the weight was 18.2 g, and the crystal growth rate was about 0.65 mm / day. Crystal growth was carried out four times under the same conditions. Of the two times, good crystals containing no voids were obtained, but the remaining two times were crystals containing a large amount of voids and low crystallinity.

(Embodiment 1) Using the apparatus of FIG.
A crystal was grown. A quartz rod having a diameter of 21 mm, a length of 100 mm, and both ends polished as a seed crystal support member was set on the bottom surface of a quartz ampoule shaped into a flat bottom with an inner diameter of 22 mm and a length of 220 mm. The seed crystal is 20mm in diameter,
A (111) B-plane ZnSe single-crystal wafer having a thickness of 1 mm and a mirror-polished front surface and a lapping-polished back surface was used and placed on the upper surface of a quartz rod. The dislocation density of the seed crystal evaluated in advance was 3 × 10 ⁴ to 1 × 10 ⁵ cm ⁻² . Further, a mesh for holding the raw material is placed at a position of 40 mm above the seed crystal, and ZnSe of about 5 mm square is formed thereon as a raw material.
40 g of polycrystal was placed. Next, add the ampoule to 1 × 10 ^-7 To
After evacuating to rr, argon gas was pumped to 20 Torr.
It was introduced and sealed with the lid. Thereafter, a quartz ampule having a height of 40 mm below the quartz rod upper surface was heated and deformed by a burner, and the quartz rod and the quartz ampule were brought into close contact with each other.

This ampule was placed in a vertical tube furnace, and
In the temperature profile as shown in FIG.
The crystal growth was performed for 20 days by heating the contact portion between the quartz rod and the quartz ampule to 1060 ° C and the lowest temperature portion at the lower end of the quartz rod to 960 ° C. As a result, the bottom diameter was 20 mm, the crystal length was 16 mm, and the weight was 2
1.2 g of grown crystals were obtained. The crystal growth rate is about 0.5.
It was 80 mm / day. Under the same conditions,
No voids were found inside the crystal for all four times.
It had a good appearance without polycrystallization or cracks. The crystal was attached to the upper surface of the quartz rod, and the dislocation density of the crystal was 8 × 10 ^{4 to} 3 × 10 ⁵ cm ⁻² . It is considered that the dislocation increased due to the stress at the time of cooling due to the adhesion to the quartz rod.

Example 2 The basic structure is the same as that of Example 1, but a quartz rod having a surface coated with a carbon thin film by a thermal CVD method was used as a seed crystal supporting member. Crystal growth was performed for 20 days under the same conditions as in Example 1 except for the above conditions. As a result, a grown crystal having a weight of 19.5 g was obtained. After cooling, the crystals easily detach from the quartz rod,
No adhesion to the quartz rod was observed. The grown crystal had a good appearance without any voids and no cracks inside the crystal. The dislocation density of the crystal is 2
× 10 ⁴ to 1 × 10 ⁵ cm ⁻² , and it was confirmed that the crystallinity was also good.

In the above embodiment, only the growth of ZnSe crystal by sublimation in an argon gas atmosphere has been described. However, the same applies to the growth of other II-VI group compound semiconductor crystals by sublimation. The invention is applicable not only to a growth atmosphere in an inert gas atmosphere such as argon but also to a growth in a gas atmosphere of a group II or group VI element using a reservoir. Similarly, the present invention is applicable not only to the sublimation method but also to the halogen chemical transport method.

[0022]

According to the present invention, by adopting the above structure, when a II-VI compound semiconductor crystal is grown on a seed crystal by a sublimation method and / or a halogen chemical transport method, voids and cracks are reduced. Generation can be prevented, and a II-VI group compound semiconductor crystal having excellent crystallinity can be produced.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an ampoule structure used in Example 1 of the present invention and a schematic diagram of a temperature distribution in a furnace.

FIG. 2 is a schematic cross-sectional view of a conventional ampoule structure used in Comparative Example 1 and a schematic diagram of a furnace temperature distribution.

──────────────────────────────────────────────────続 き Continued on the front page (56) References Yu. V. Korostein et al. , "Vapour growth and characterization of bulk Zn Sessle crystals,", Journal of Crystal growth, Vol. 161, 1996, p. 51-59 (58) Field surveyed (Int. Cl. ⁷ , DB name) C30B 1/00-35/00

Claims (3)

(57) [Claims] 1. A raw material polycrystal and a seed crystal are placed in a growth chamber, and II is placed on the seed crystal by a sublimation method or a halogen chemical transport method.
In the method for growing a group-VI compound semiconductor crystal, a columnar seed crystal support member is fixed to one end of the growth chamber, and the growth chamber and the support member are stable under a crystal growth environment and are exposed to visible light and / or light. Constructed of a material transparent to infrared light, the end face opposite to the fixed end of the support member is formed as a smooth plane, the seed crystal is held thereon, and the support member and the growth chamber wall are The gap is closed at an intermediate portion of the support member to form an airtight portion, and gas in the growth chamber is prevented from flowing toward the fixed end of the support member, and the temperature Te at the fixed end of the support member is reduced to the airtight portion. A method for growing a II-VI group compound semiconductor crystal, wherein the crystal is grown while maintaining the temperature below Td. 2. The II-V according to claim 1, wherein an effective temperature Tc ^* of a smooth plane of said support member is controlled by adjusting a temperature Te of a fixed end of said support member.
A method for growing a group I compound semiconductor crystal. 3. The method of growing a II-VI compound semiconductor crystal according to claim 1, wherein a coating film for preventing seed crystal adhesion is interposed between said seed crystal and said support member.