WO2005083160A1 - COMPOUND SEMICONDUCTOR SINGLE CRYSTAL MANUFACTURING METHOD AND ZnTe SINGLE CRYSTAL - Google Patents

Abstract

A method for manufacturing a compound semiconductor single crystal is provided so as to grow a (110) oriented compound semiconductor single crystal having an excellent crystal quality. In a compound semiconductor single crystal manufacturing method employing a liquid encapsulation Czochralski method, a material melt container composed of a bottomed cylinder-shaped first crucible and a second crucible, which is arranged on the inner side of the first crucible and has holes for communicating with the first crucible, contains a semiconductor material and a sealant, the container is heated to melt a material, a seed crystal is brought into contact with the material melt surface under the condition wherein the material is covered with the sealant, and the crystal is grown by pulling the seed crystal. As the second crucible, a crucible having a plurality of communicating holes is used, and the crystal is grown by pulling the seed crystal in the <110> direction.

Description

 Specification

 Method for producing compound semiconductor single crystal and ZnTe single crystal

 Technical field

 The present invention relates to a method for producing a compound semiconductor single crystal by a liquid-sealed Czochralski (LEC) method and a technique useful for being applied to a ZnTe single crystal.

 Background art

 [0002] At present, a ZnTe-based compound semiconductor single crystal is expected to be a crystal that can be used for a pure green light emitting device.

 As a prior application technique, the present applicant has proposed a method of manufacturing a compound semiconductor single crystal by a liquid-sealed Czochralski method (LEC method) using a double crucible (Japanese Patent Application No. 2002-249963). The above-mentioned prior application is characterized in that the crystal is grown so as to be substantially the same as the inner diameter of the inner crucible while maintaining the surface of the grown crystal covered with the liquid sealant until the crystal growth is completed. . In addition, one communication hole having an inner diameter of 1Z5 or less is provided on the bottom surface of the inner crucible to provide an introduction path for the raw material melt accommodated in the outer crucible, so that the temperature fluctuation of the raw material melt in the inner crucible is small. We are trying to be creative.

[0003] Further, Patent Documents 14 and 14 propose a technique for manufacturing a compound semiconductor single crystal by a LEC method using a double crucible. In Patent Documents 1 and 2, in particular, Patent Documents 1 and 2 disclose multiple techniques near the bottom surface of an inner crucible. A crystal growth apparatus provided with a communication hole is exemplified.

 Patent Document 1: JP-A-61-26590

 Patent Document 2: JP-A-63-195188

 Patent Document 3: JP-A-62-288193

 Patent Document 4: JP-A-60-27693

 Disclosure of the invention

 Problems to be solved by the invention

[0004] While applying force, the inventors of the present invention utilized the above-mentioned prior application technique to grow a ZnTe single crystal by pulling it up in the <110> direction by the LEC method. found. In addition, the obtained ZnTe single crystal did not grow at a uniform rate in the <110> direction. It was a crystal with large distortion.

 [0005] Incidentally, Patent Literature 2 exemplifies a method of growing an InAs single crystal in the <100> direction, and Patent Literature 4 discloses a method of growing a GaAs single crystal in the <100> direction. Is illustrated. Japanese Patent Application No. 2002-249963 exemplifies a method of growing a ZnTe-based compound semiconductor single crystal by pulling it in the <100> direction. On the other hand, Patent Documents 1 and 3 do not specifically describe the crystal orientation of the grown crystal!

 That is, the above-mentioned prior art is suitable for growing a compound semiconductor single crystal having a relatively good symmetry in a (100) orientation, but has a poor symmetry and a compound in a (110) orientation. It cannot be used as it is when growing a semiconductor single crystal.

 An object of the present invention is to provide a method for producing a compound semiconductor single crystal capable of growing a compound semiconductor single crystal having a (110) orientation with excellent crystal quality.

 Means for solving the problem

[0008] In order to solve the above-mentioned problems, the present inventors have repeatedly studied a method for producing a (110) oriented ZnTe single crystal based on the above-mentioned prior art (Japanese Patent Application No. 2002-249963). As a result, it was concluded that there was almost no difference between the center temperature of the material melt surface in the inner crucible and the surrounding temperature. This is because, in the crystal growth apparatus of the prior application, the raw material melt in the inner crucible is heated by the heat conduction of the crucible itself, and the melt of the outer crucible introduced from the communication hole provided at the center of the bottom surface of the inner crucible. It was considered that the material was heated by radiant heat from the raw material melt. Therefore, it was thought that by shifting the position of the communication hole provided in the inner crucible to the center force of the bottom surface, the center temperature of the surface of the raw material melt in the inner crucible can be lowered as compared with the surroundings.

The present invention has been completed based on the above findings, and has a first crucible having a bottomed cylindrical shape and a communication hole provided inside the first crucible and communicating with the first crucible. (2) A semiconductor material and a sealant are accommodated in a material melt accommodating portion composed of a crucible, and the material accommodating portion is heated to melt the material, and the material melt is covered with the sealant. A method for producing a compound semiconductor single crystal by a liquid-sealed Czochralski method in which a seed crystal is brought into contact with a surface to grow the seed crystal while pulling the seed crystal, wherein the second crucible has a plurality of communication holes. And grow the crystal while pulling the seed crystal in the <110> direction. It is characterized by that.

 [0010] Preferably, a plurality of communication holes are formed along the outer periphery of the bottom surface of the second crucible off the center, and the total area of the plurality of communication holes is 1Z10 or less of the bottom area of the second crucible. For example, the plurality of communication holes are provided at equal intervals along a circumference at a fixed distance from the center of the bottom surface of the second crucible.

 [0011] Thus, the temperature fluctuation in the raw material melt in the second crucible can be reduced, and the crystal can be grown at a uniform rate in the <110> direction. The single crystallization ratio of the crystal can be improved.

 [0012] Further, a ZnTe single crystal having a plane orientation of (110) and a light transmittance of 20% or less can be obtained by the above-described manufacturing method. As shown in FIG. 3, the light transmittance here means that the first polarizing plate 22, the ZnTe single crystal substrate 23, and the second polarizing plate 24 are respectively placed on the optical path connecting the light source 21 and the photodiode 25. When the light receiving surface is arranged perpendicular to the optical path and the polarization directions A and B of the two polarizers 22 and 24 are adjusted to be perpendicular, based on the amount of transmitted light measured by the photodiode 25, It is calculated. Specifically, when the ZnTe single crystal substrate 23 is not arranged and the polarization directions A and B of the two polarizing plates 22 and 24 are adjusted to be parallel, the amount of light received by the photodiode 25 is reduced by 100%. Is calculated as the light transmittance.

 [0013] In other words, by arranging the ZnTe single crystal substrate 23, the polarization direction of light changes, and light that should not be measured by the photodiode 25 should be received. According to the calculated light transmittance, the crystal distortion of the ZnTe single crystal substrate 23 disposed between the two polarizing plates 22 and 24 is specified by a numerical value. In other words, it can be said that the smaller the light transmittance, the smaller the crystal distortion and the better the crystal quality.

 The invention's effect

According to the present invention, a raw material melt comprising a bottomed cylindrical first crucible and a second crucible disposed inside the first crucible and provided with a communication hole with the first crucible. A semiconductor material and a sealing material are housed in a housing part, the material housing part is heated to melt the raw material, and a seed crystal is brought into contact with the surface of the raw material melt in a state of being covered with the sealing material. A method for producing a compound semiconductor single crystal by a liquid-sealed Czochralski method of growing a seed crystal by pulling the seed crystal, wherein a crucible having a plurality of communication holes is used as the second crucible. Since the crystal is grown while pulling the seed crystal in the direction, the temperature fluctuation in the raw material melt contained in the second crucible can be suppressed. As a result, it is possible to prevent the generation of twin crystal and polycrystal and to increase the single crystallization ratio, and to produce an effect of producing a semiconductor compound single crystal with a high yield.

[0015] Further, a ZnTe single crystal having a plane orientation of (110) and a light transmittance of 20% or less obtained by the above-described manufacturing method has extremely small distortion and excellent crystallinity, and thus is suitable as a semiconductor device such as a light emitting element. It is.

 Brief Description of Drawings

FIG. 1 is a schematic configuration diagram of a crystal growth apparatus used in an embodiment of the present invention.

 FIG. 2 is an enlarged view of a raw material accommodating portion of the crystal growth apparatus of FIG. 1, wherein (a) is a cross-sectional view and (b) is a top view.

FIG. 3 is a schematic view of a measuring device for measuring a light reception amount for calculating a light transmittance of a ZnTe single crystal wafer.

 Explanation of symbols

 1 Pressurized container

 2 Insulation

 3 Heater

 4 Crucible rotation axis

 5 Outer crucible (first crucible)

 6 Inner crucible (second crucible)

 6a Communication hole

 7 Rotating shaft

 8 seed crystal holder

 9 seed crystal

 10 Growing crystal

 11 Sealant

 12 Raw material melt

13 Susceptor 100 crystal growth equipment

 BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

 FIG. 1 is a schematic configuration diagram of a crystal growth apparatus according to the present embodiment. The crystal growth apparatus 100 of the present embodiment includes a high-pressure vessel 1, a heat insulating material 2 and a heater 3 arranged concentrically with the high-pressure vessel, and a rotating shaft vertically arranged at the center of the high-pressure vessel 1. 4, a susceptor 13 arranged at the upper end of the rotating shaft 4, an outer crucible (first crucible) 5 made of pBN having a bottomed cylindrical shape fitted to the susceptor, and an inner crucible 5. A second crucible 6 made of pBN and a rotary pull-up shaft 7 provided with a seed crystal holder 8 vertically provided above the inner crucible 6 and fixed at a lower end to fix a seed crystal 9. You.

 The inner crucible 6 has a communication hole 6 a on the bottom surface communicating with the outer crucible 5, and the raw material melt 12 can be moved from the outer crucible 5 to the inner crucible 6 via this communication hole. . In the present embodiment, as shown in FIG. 2, four communication holes 6a are provided on the bottom surface of the inner crucible 6 at equal intervals along a circumference at a fixed distance from the center of the bottom surface. The inner crucible 6 is fixed to the outer crucible 5 or another jig by a suitable holder (not shown).

 [0020] Also, since the inner crucible 6 has a tapered structure in which the inner diameter at the bottom is smaller than the inner diameter at the top, the diameter of the grown crystal that has been pulled up is smaller than the inner diameter at the corresponding position of the second crucible. And the grown crystal no longer contacts the crucible wall except at the growth interface

[0021] The rotary pulling shaft 7 is connected to a driving unit (not shown) arranged outside the high-pressure vessel to constitute a rotary pulling mechanism. The rotating shaft 4 is connected to a driving unit (not shown) arranged outside the high-pressure vessel to constitute a crucible rotating mechanism and constitute a susceptor elevating mechanism. The movements of the rotation and lifting shaft 7 and the crucible rotation shaft 4 and the movement of the elevating movement are set and controlled independently of each other.

According to the above-described crystal growth apparatus, since the plurality of communication holes 6a are provided at positions off the center of the bottom surface of the inner crucible 6, temperature fluctuation in the raw material melt accommodated in the inner crucible 6 is suppressed. The crystal can be grown at a uniform speed in the <110> direction. That As a result, it is possible to prevent twins and polycrystals from being generated, to increase the single crystallization ratio, and to produce a single crystal with a high yield.

 Example 1

 Using a crystal growth apparatus 100, a (110) oriented ZnTe single crystal was produced as an example of a compound semiconductor.

 In the present embodiment, a crucible made of ρΒΝ having an inner diameter of 100 mm φ × 100 mm height × lmm thickness is used as the outer crucible 5, and a taper structure having an inner diameter of 54 mm φ—56 mm φ × 100 mm height × lmm thickness lmm is used as the inner knurling 6. A crucible made of pBN was used.

 Further, the bottom surface of the inner crucible 6 is provided with four communication holes 6a at positions that are rotated by 90 ° from each other on a circle having a diameter of 50 mm and concentric with the bottom surface. The diameter of the communication hole 6a was 4 mm. The size of the communication hole 6a is not limited to 4 mm, and it is sufficient that the total area of the communication hole 6a is not more than 1Z10 of the bottom area of the inner crucible 6.

First, a total of 1.5 kg of Zn having a purity of 6N and Te of 6N as raw materials are put into the outer crucible 5 and the inner crucible so that Zn and Te have an equimolar ratio, and 400 g is sealed thereon. Agent (BO) 11

 It was covered with 23 so that the thickness of the sealant layer was 35 mm. The inner crucible 6 was fixed with a holder so that the raw material was melted by the heating heater 2 and then immersed at a depth of 20 mm from the liquid surface of the raw material melt. Although the raw material melt gradually decreases with the crystal growth, the immersion state of the inner crucible 6 was controlled by raising and lowering the susceptor 13 (the outer crucible 5) by driving the rotating shaft 4 up and down. For example, the inner crucible 6 was kept immersed in a range of 10 mm to 40 mm from the liquid level of the raw material melt.

Next, the outer crucible 5 and the inner crucible 6 were arranged on the susceptor 13, and the inside of the high-pressure vessel 1 was filled with an inert gas (for example, Ar) and adjusted to a predetermined pressure. Then, heating was performed at a predetermined temperature using a heater 2 while suppressing the surface of the raw material with a sealing agent, and Zn and Te were melted and directly synthesized.

[0026] Thereafter, after keeping the raw material in a molten state for a certain period of time, the seed crystal 9 was brought into contact with the surface of the raw material melt. Here, a seed crystal having a crystal orientation of (110) was used as the seed crystal. Further, in order to prevent the seed crystal 9 from being decomposed, the seed crystal was covered with a cover (not shown) made of molybdenum. Then, the pulling rotation shaft 7 was rotated at a rotation speed of 11 to 12 rpm, and a shoulder portion of a crystal was formed while pulling at a speed of 2.5 mmZh. Subsequently, after the shoulders were formed, the crucible rotation shaft was rotated at 115 rpm, and the body was formed while pulling up at a speed of 2.5 mmZh.

 At this time, since the gap between the growing crystal 11 and the inner crucible 6 is small, the amount of the sealant 11 on the upper part of the crystal wrapping around the gap is small, and the crystal surface is always kept covered with the sealant 11. As a result, the constituent elements of the grown crystal 10 were prevented from evaporating, and the temperature gradient in the sealant could be made very small. In addition, it was possible to grow single crystals even when the temperature gradient in the raw material melt during crystal growth was 5 ° CZcm or less. The temperature fluctuation in the raw material melt in the inner crucible 6 was about 0.5 ° C, and the temperature fluctuation in the raw material melt between the inner crucible 6 and the outer crucible 5 was 1 ° C.

 As described above, the crystal was grown by the LEC method, and after the crystal growth, the grown crystal 10 was separated from the encapsulant 11 to obtain a crack-free ZnTe single crystal. The obtained crystal was a very good single crystal having a (110) orientation without polycrystals or twins. The size of the grown crystal was 54 mm in diameter and 40 mm in length of the straight body. Similarly, when a ZnTe single crystal was repeatedly grown, seven out of ten single crystals became single crystals, and the single crystallization ratio was 70% .o

Further, a single-crystal wafer was prepared by slicing the obtained (110) -oriented ZnTe single crystal to a thickness of 1000 m, and the light transmittance of the single-crystal wafer was measured by a measuring apparatus shown in FIG. Specifically, first, the polarization directions A and B of the two polarizing plates 22 and 24 were adjusted so as to be parallel, and the amount of received light at this time was measured by the photodiode 25. Next, the polarization directions A and B of the two polarizing plates 22 and 24 were adjusted to be vertical, and it was confirmed that the amount of received light was 0 at this time. Then, the two polarizers 22, 24 are held in this state, and the ZnTe single crystal wafer 23 produced between them is moved so that the (110) planes of the polarizers 22, 24 and the ZnTe single crystal wafer 23 are parallel. The light receiving amount (transmitted light amount) at this time was measured. Then, assuming that the amount of received light when the polarization directions A and B of the two polarizing plates 22 and 24 are adjusted to be parallel is 100, and the amount of received light when the ZnTe single crystal wafer 23 is disposed is also the light transmittance ( %) Was calculated. The light source used was 800 nm laser light. As a result, the light transmittance is 6% or less, and It helped to be a crystal.

 [0031] As described above, the (110) oriented ZnTe single crystal obtained by the above-described manufacturing method has a light transmittance of 20% or less, extremely small crystal distortion, and excellent crystallinity. It is suitable as.

 Comparative Example 1

 As Comparative Example 1, a (110) oriented ZnTe single crystal was manufactured using the crystal growth apparatus proposed by the present applicant in Japanese Patent Application No. 2002-249963. The crystal growth apparatus according to the prior application differs from the crystal growth apparatus according to the above embodiment in that only one communication hole is provided at the center of the bottom surface of the inner crucible. The crystal growth was performed in exactly the same manner as the other conditions.

 [0033] As a result, only one of the ten crystals became a single crystal, and the single crystallization ratio was 10%. Further, when the obtained grown crystal was observed, it was found that a single crystal region of about half was obtained by dendrite (榭 branch-like crystal) growth, and the whole was polycrystalline. In addition, even when a single crystal region is formed large by dendrite growth, there is a problem in the uniformity when a (110) oriented substrate is cut out from a grown crystal in the (110) plane crystal growth.

 On the other hand, when the same crystal growth apparatus was used to increase the temperature gradient during crystal growth and grow the crystal at 30 ° CZcm, a single crystal could be grown. However, the light transmittance of the obtained ZnTe single crystal wafer was about 25%, which was a component of the fact that it was a single crystal with large crystal distortion. In other words, it is considered that if the temperature gradient is too large, the thermal stress applied to the grown crystal increases, and the crystal distortion increases.

 Comparative Example 2

 [0035] As Comparative Example 2, a single crystal growth rate higher than that of the LEC method, in which the temperature gradient during crystal growth is relatively low, and the use of the LEK (liquid-sealed chiroporous) method for ZnTe single-crystal (110) orientation Crystals were produced. The crystal growth apparatus of the LEK method is publicly known as disclosed, for example, in Japanese Patent Application Laid-Open No. 2003-112993, and therefore its description is omitted.

 [0036] As a result, seven of the ten crystals became single crystals, and the single crystallization ratio was 70%, which was the same as in the above embodiment. While applying force, the light transmittance of the obtained ZnTe single crystal wafer was 50%, and the crystal distortion was larger than in Comparative Example 1.

[0037] The invention specifically described based on the embodiments made by the inventor has been described. The description is not limited to the above embodiment.

 In the above embodiment, the formation pattern and the number of the force communication holes in which the four communication holes 6a are provided on the bottom surface of the inner crucible along the circumference at a fixed distance from the center of the bottom surface are not limited to this.

 It goes without saying that the present invention can be applied not only to the growth of the (110) orientation but also to the growth of the (100) and (111) orientations. By applying the present invention also to the production of a compound semiconductor single crystal, a large and high-quality compound semiconductor single crystal can be obtained.

Claims

The scope of the claims  [1] A semiconductor raw material is stored in a raw material melt accommodating portion composed of a bottomed cylindrical first crucible and a second crucible disposed inside the first crucible and provided with a communication hole with the first crucible. And a sealant, and the raw material storage section is heated to melt the raw material, and a seed crystal is brought into contact with the surface of the raw material melt in a state covered with the sealant, while pulling up the seed crystal. A method for producing a compound semiconductor single crystal by a liquid-sealed Czochralski method for growing a crystal, comprising using a crucible having a plurality of communication holes as the second crucible and pulling up a seed crystal in a <110> direction. Method for producing compound semiconductor single crystal characterized by growing [2] The plurality of communication holes are provided along the outer periphery of the bottom surface of the second crucible off center, and the total area of the plurality of communication holes is 1Z10 or less of the bottom area of the second crucible. 2. The method for producing a compound semiconductor single crystal according to claim 1, wherein:  [3] A crystal produced by the method according to any one of [1] and [2], wherein a ZnTe single crystal substrate having a plane orientation of (110) is disposed between two polarizing plates arranged so that polarization directions are orthogonal to each other. In the sandwiched state, when a predetermined light is incident from the outside of the one polarizing plate, the light transmittance transmitted to the outside of the other polarizing plate is 20% or less, wherein the ZnTe single crystal is