JPH05254978A - Method and apparatus for producing compound semiconductor single crystal - Google Patents

Abstract

PURPOSE:To suppress the generation of twin defects and to improve the yield of the AB type compd. semiconductor single crystal having a crystal structure of a sphalerite type by controlling the shape of the shoulder part of the crystal to a specific shape at the time of producing the above-mentioned single crystal by a boat method. CONSTITUTION:After a raw material melt is formed in a boat, a seed crystal is brought into contact with the raw material melt and is then cooled to gradually lower the temp. of the melt, by which the AB type compd. semiconductor single crystal having the crystal structure of the sphalerite type is grown. The crystal is grown by designating the angle of the shoulder part in a horizontal direction for the plane perpendicular to longitudinal direction of the crystal 1 as thetah and the angle of the shoulder part in a perpendicular direction for the plane perpendicular to the longitudinal direction of the crystal 1 as thetav and setting these angles at 75 deg.>theta>thetav>30 deg. relating to the shoulder part of the crystal 1 which is an increased diameter part from the seed crystal 2 to the straight cylindrical part of the AB type compd. semiconductor single crystal to be grown at this time. As a result, the generation frequencies of the twin defects is lessened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a compound semiconductor single crystal by a boat method such as a horizontal Bridgman method (HB method) or a temperature gradient method (GF method), a vertical Bridgman method or a colacle method. It relates to the manufacturing method.

[0002]

2. Description of the Related Art Conventionally, in growing a compound semiconductor single crystal by the boat method, the growth direction of the single crystal is set in the <111> direction parallel to the longitudinal direction of the boat so that the wafer surface of the crystal becomes the (100) plane. , Crystal longitudinal direction (growth direction)
The wafer was cut out obliquely at a predetermined angle.
Further, from the viewpoint of productivity, a method of growing in the <100> direction is partially performed so that the wafer can be cut out perpendicularly to the crystal growth direction. However, the growth in the <100> direction is
Twin defects, which are crystal defects, are more likely to occur than in the 111> direction growth, and the yield is reduced.

In the conventional liquid-sealed vertical Bridgman method and colacle method, the cross-sectional shape perpendicular to the growth direction of the crystal to be grown has a rotationally symmetric shape with the growth direction as a rotation axis, and is generally a circular cross-sectional shape. Are doing When growing such a crystal, twin defects, which are crystal defects, tend to occur from the shoulder portion of the crystal, which is the increased diameter portion from the seed crystal to the straight body portion, and the yield is significantly reduced. ..

Further, in the conventional boat method and liquid-sealed vertical Bridgman method, the shape of the shoulder portion of a crystal in which twin defects are likely to occur is approximately a semi-conical shape or a conical shape (a surface perpendicular to the crystal growth direction). The shape was almost semi-circular or circular when viewed at.

[0005]

DISCLOSURE OF THE INVENTION The object of the present invention is that the above-mentioned problems of the prior art, that is, <100> direction growth is more likely to cause twin defects than <111> direction growth,
The problem that the yield was reduced, and when growing a crystal with a circular cross-sectional shape by the conventional liquid-sealed vertical Bridgman method or oracle method, the diameter increase from the seed crystal to the straight body part It is intended to solve the problem that twin defects are apt to be generated from the shoulder portion of the crystal, which is a portion, and the yield is remarkably reduced.

[0006]

The present invention has been made to solve the above-mentioned problems, and as a first invention,
In a method for producing an AB type compound semiconductor single crystal having a zinc blende type crystal structure using a boat method, a crystal that is an increased diameter portion from a seed crystal of an AB type compound semiconductor single crystal to be grown to a straight body portion The angle of the shoulder with respect to the plane perpendicular to the longitudinal direction of the crystal is θh,
A method for producing a compound semiconductor single crystal is characterized in that the crystal is grown at 75 °>θh>θv> 30 °, where θv is the angle of the shoulder in the vertical direction with respect to the plane perpendicular to the longitudinal direction of the crystal. provide.

As a second invention, an AB type compound semiconductor to be grown in a method of growing an AB type compound semiconductor single crystal having a zinc blende type crystal structure in a substantially vertical direction such as a vertical Bridgman method. When the shoulder portion of the crystal that is the increased diameter portion from the seed crystal of the single crystal to the straight body portion is viewed in two cross sections that are parallel to the crystal longitudinal direction and are orthogonal to the central axis of the crystal longitudinal direction, The angles θa and θb formed by the shoulder with respect to the plane perpendicular to the crystal longitudinal direction are θa ≠ θb.
A method for producing a compound semiconductor single crystal is provided.

As a third invention, in an apparatus for producing an AB type compound semiconductor single crystal having a zinc blende type crystal structure by using a boat method, a straight body is formed from a seed crystal of the AB type compound semiconductor single crystal to be grown. As to the shoulder of the crystal which is the increased diameter portion to the part, the angle of the shoulder in the horizontal direction with respect to the plane perpendicular to the longitudinal direction of the crystal is θh, and the shoulder in the direction perpendicular to the plane perpendicular to the longitudinal direction of the crystal is Provided is an apparatus for producing a compound semiconductor single crystal, wherein an inner surface of a boat corresponding to the shoulder is formed so that when the angle is θv, 75 °>θh>θv> 30 °.

As a fourth invention, an AB type compound semiconductor to be grown in an apparatus for growing an AB type compound semiconductor single crystal having a zinc blende type crystal structure in a substantially vertical direction such as the vertical Bridgman method. When the shoulder portion of the crystal that is the increased diameter portion from the seed crystal of the single crystal to the straight body portion is viewed in two cross sections that are parallel to the crystal longitudinal direction and are orthogonal to the central axis of the crystal longitudinal direction, The angles θa and θb formed by the shoulder with respect to the plane perpendicular to the crystal longitudinal direction are θa ≠ θb.
An inner surface of a boat corresponding to the shoulder is formed so that the compound semiconductor single crystal manufacturing apparatus is provided.

The structure of the present invention will be described in detail below. When manufacturing a compound semiconductor single crystal by the boat method, a side view of an AB-type compound semiconductor single crystal to be grown in a horizontal direction and a top view in a vertical direction are shown in FIGS. 1 and 2, respectively. Here, θh and θv respectively indicate the angles of the crystal shoulders in the horizontal direction and the vertical direction (which substantially coincide with the vertical direction). More specifically, θv is the angle of the vertical shoulder portion in the plane perpendicular to the width direction of the crystal including the central axis in the crystal longitudinal direction (growth direction) with respect to the plane perpendicular to the crystal longitudinal direction.

In FIG. 1, the length in the crystal longitudinal direction of the crystal shoulder, which is the increased diameter portion from the seed crystal 2 to the straight body portion, is Lh.
And Assuming that the distance in the vertical direction increased from the seed crystal 2 to the straight body portion is H, the angle θv of the crystal shoulder portion in the vertical direction is
Can be expressed as arctan (Lh / H). Further, in FIG. 2 which is a top view of the crystal to be grown viewed from above vertically, the length in the crystal longitudinal direction of the crystal shoulder, which is the increased diameter portion, is Lr.
If the half of the length obtained by subtracting the horizontal diameter perpendicular to the crystal longitudinal direction of the seed crystal from the horizontal diameter perpendicular to the crystal longitudinal direction of the straight body is R, the angle of the horizontal crystal shoulder θh Can be represented as arctan (Lr / R).

Here, it is assumed that 75 degrees>θh>θv> 30 degrees. At this time, it is more preferable that the angle difference between θh and θv is large, and the difference is preferably 10 degrees or more, and more preferably 20 degrees or more. Further, it is preferable that θh is 55 degrees or more and θv is 55 degrees or less because the effect of further suppressing the occurrence frequency of twin defects is increased.

(10) of the AB type compound semiconductor single crystal
In order to cut out a (100) wafer perpendicular to the crystal longitudinal direction by making one plane equivalent to the (0) plane substantially parallel to a plane perpendicular to the crystal growth direction which is the crystal longitudinal direction, It has a large cost advantage and is preferable.

As a sectional shape perpendicular to the longitudinal direction of the boat, an arc, an elliptic arc, a polygon such as a pentagon or a hexagon, and a shape such as an ellipse whose central portion is wider than the upper portion and the bottom portion are used. It is preferable to design the boat so as to reduce the processing loss of the crystal from the crystal growth orientation and the wafer shape created by slicing the crystal. Further, the boat cross-section upper portion is opened, and the width of the opening is 10 to 10 times the maximum width of the central portion.
Providing an opening of 90% is preferable because it makes it easy to charge the boat with the raw material and allows observation of crystals during growth.

Here, H / R is 1.3 ≦ H / R ≦ 2.5
By doing so, a larger circular (100) wafer can be cut without waste at an angle close to a plane perpendicular to the boat longitudinal direction. Further, it is preferable that H / R is closer to 2 because it has more cost merit.

A case of a crystal manufacturing method in which a crystal is grown in the vertical direction will be described with an example of the vertical Bridgman method. FIG. 3 shows a sectional view perpendicular to the growth direction of the crystal shoulder to be grown. Here, FIGS. 4 and 5 are cross-sectional views in the crystal growth direction in the aa1 and b-b1 cross sections (two cross sections parallel to the crystal longitudinal direction and orthogonal to the central axis of the crystal longitudinal direction). The angles θa and θb of the crystal shoulders shown in the cross-sectional views of FIGS. 4 and 5 are different, and they are set to 30 degrees or more and 75 degrees or less.

Further, when the angle θa of the shoulder portion is 55 degrees or more and θb is 55 degrees or less, generation of twin defects can be further suppressed. Further, it is more preferable that the angle difference between θa and θb at this time is large, and it is desired that the difference be 10 degrees or more, preferably 20 degrees or more. In this case, the shoulder portion of the crystal has an elliptical shape, a rhombic shape, or the like in which θa and θb are different when viewed in a cross section perpendicular to the longitudinal direction, but the main body (straight body portion) of the crystal may be circular. Alternatively, it may be oval. However, in order to obtain a circular wafer by slicing and cutting the crystal body (straight body portion), it is preferable that the cross section is circular.

When the AB type compound semiconductor single crystal is manufactured by the boat method or the vertical Bridgman method, one plane equivalent to the (100) plane of the seed crystal is perpendicular to the crystal growth direction which is the crystal longitudinal direction. The angle formed with the plane is within 30 degrees, and further, one plane equivalent to the (100) plane of the seed crystal is substantially aligned with the plane perpendicular to the crystal growth direction, which is the crystal longitudinal direction ( The two <100> equivalent directions are assumed to be substantially parallel to the crystal longitudinal direction).
It is more preferable because the wafer can be cut out perpendicularly to the growth direction.

The AB type compound semiconductor single crystal having a zinc blende type crystal structure according to the present invention includes GaAs and I.
Group 3-5 compound semiconductor single crystal such as nP, 2 such as ZnSe
A Group-6 compound semiconductor single crystal is used.

[0020]

In the present invention, it has been experimentally confirmed that, when a crystal is grown by the boat method, twin defects are reduced and the crystal yield is improved by selecting the crystal shape as described above. However, its mechanism of action is not clear in detail.

As an example of a compound semiconductor single crystal, GaAs
An attempt was made to grow a single crystal. In the experiment, boats in which θh and θv were changed were created, and each experiment was carried out once. The seed crystal orientation was <100> as the crystal longitudinal direction (growth direction). In this experiment, when twin defects were observed during growth, meltback was performed, growth was performed several times until the twin defects disappeared, and the number of observed twin defects was examined.

As a result, when θh = θv, the frequency of occurrence of twin defects was particularly high, and meltback was carried out 8 times or more, but crystals without twin defects were not obtained. Also, θh
When> θv, the frequency of occurrence of twin defects is low.
In particular, θh> 55 degrees> θv, θh = 60 degrees, θv = 5
Twin defects did not occur at 0 degree.

From the above results, when both θh and θv are 75 degrees or less and 30 degrees or more, the generation of twin defects is suppressed. Further, it is preferable that θh be larger than θv, because the effect becomes large. In addition, θh is 55 degrees or more, and θv is 5
It was found that the effect of suppressing the occurrence frequency of twin defects is further increased by setting the angle to 5 degrees or less.

Next, as an example of a crystal manufacturing method for growing a crystal in the vertical direction, an experiment for growing a GaAs single crystal by the vertical Bridgman method was tried.

In the experiment, crucibles having different θa and θb were prepared, and the growing experiment was conducted four times each. The seed crystal orientation was <100> as the crystal longitudinal direction (growth direction). In this experiment, the number of crystal growth times in which twin defects were generated and the number of twin defects in which crystals were generated were examined.

As a result, as compared with the case where the crystal shape is rotationally symmetric with respect to the growth axis where θa and θb are equal to each other, the frequency of twinning is smaller in the asymmetrical shape which is not rotationally symmetric, and the angle of the shoulder portion is smaller. It was found that the twinning occurrence frequency was reduced when the angle was 30 degrees or more and 75 degrees or less, and the twinning defect frequency was particularly low when θa> 55 degrees> θb.

From the above results, the angles θa and θ of the crystal shoulder are
b is different, and is set to 30 degrees or more and 75 degrees or less, and the shoulder angle θa is 55 degrees or more and θb is 55 degrees.
It was found that the occurrence of twin defects can be further suppressed by setting the ratio to be less than 100 degrees.

[0028]

EXAMPLES Examples for producing a GaAs single crystal will be described below.

(Example 1) FIGS. 1 and 2 are a side view and a top view of a crystal to be grown when the crystal is grown by the boat method. FIG. 6 shows a front view seen from the seed crystal side. FIG. 7 shows a side cross-sectional view in the longitudinal direction of the reaction container when growing. In the figure, 2 is a seed crystal, 3 is a boat, 4 is Ga, 5 is a reaction vessel, and 6 is As.

In the crystal growth experiment, eight kinds of boats having different θh and θv were prepared and the growth experiment was conducted once. For the seed crystal orientation, the <100> equivalent direction was taken as the longitudinal direction (growth direction) of the crystal.

As shown in FIG. 7, 21 Ga 4 is placed in the boat 2.
00g is put, and 2300g of As6 is added to the other end of the reaction vessel 5.
Then, the inside of the reaction vessel 5 is depressurized to a vacuum state and sealed. Next, the reaction vessel 5 is put into a crystal growth furnace, As in the reaction vessel 5 is heated to 600 ° C., and As vapor pressure in the reaction vessel 5 is set to 1 at.
m, maintaining the boat section in the reaction vessel 5 at 1200 ° C.,
Ga and As vapor react to synthesize GaAs.

Thereafter, the temperature is further raised to set the seed crystal temperature to 123.
At 8 ° C., the temperature gradient in the GaAs melt is set to about 0.5 ° C./cm, and the seed crystal and the GaAs melt are brought into contact with each other. Then, the temperature of the melt is gradually lowered and cooled to grow crystals. After completely solidifying, the temperature was further lowered to room temperature, and crystals were taken out. In this experiment, when twins were observed during growth, meltback was performed, growth was performed several times until twin defects disappeared, and the number of observed twin defects was examined. Table 1 summarizes the number of twinning occurrences observed during the growth in each boat shape.

[0033]

[Table 1]

As can be seen from Table 1, when θh = θv, the frequency of occurrence of twin defects is particularly high at 80 ° and 20 °, and melt-back was performed 8 times or more, but crystals without twin defects were obtained. It didn't reach. Further, when θh> θv, the frequency of occurrence of twin defects is low. Especially θh> 5
Twin defects did not occur at θh = 60 ° and θv = 50 ° where 5 °> θv. In this boat with θh = 60 degrees and θv = 50 degrees, the crystal growth experiment was performed 10 times to confirm the reproducibility. As a result, the frequency of occurrence of twin defects was 1 in 10 times.
It was once. Further, even during the crystal growth when the twin defects were generated, it was possible to obtain a crystal without twin defects by performing the meltback once.

(Embodiment 2) FIG. 3 shows a sectional view of a shoulder portion of a crystal to be grown by the vertical Bridgman method, which is perpendicular to the crystal growth direction. Here, a- where the shoulder angle is the largest
4 and 5 are cross-sectional views in the crystal growth direction in the a1 cross section and the bb1 cross section in which the angle of the shoulder portion is the smallest.
FIG. 8 shows GaA by the conventional liquid-sealed vertical Bridgman method.
The typical side view in the furnace for s crystal growth is shown. In the figure, 1 is a crystal, 2 is a seed crystal, 7 is a liquid sealing material, 8 is a crucible, 9 is a heater, and 10 is a high-pressure container.

In the experiment, crucibles having different θa and θb were prepared, and the growing experiment was conducted four times each. Seed crystal orientation is the <100> direction in the crystal longitudinal direction (growth direction)
And In this experiment, the number of crystal growth times (number of crystals) in which twin defects were generated and the number of twin defects in which crystals were generated were examined.

Seed crystal 2 was placed at the bottom of crucible 8. Next, about 2000 g of raw GaAs crystal and about 260 g
The liquid sealing material 7 (B2 O3) is filled. After that, heating was performed in a normal vertical Bridgman furnace to soften the liquid encapsulant, melt the raw material crystals from above, and perform seeding to grow crystals. After that, the crystal was gradually solidified from the lower part to complete the crystal growth. Table 2 summarizes the number of twinning occurrences observed during the growth in each crucible shape.

[0038]

[Table 2]

As a result, the twinning frequency is lower in the asymmetrical shape that is not rotationally symmetric than in the case where the crystal shape is rotationally symmetric with respect to the growth axis where θa and θb are equal. Further, when the angle of the shoulder portion is 30 degrees or more and 75 degrees or less, the twinning occurrence frequency decreases. It was also found that the twin defect occurrence frequency was particularly small when θa> 55 °> θb. This θa = 6
With a crucible of 0 ° and θb = 50 °, reproducibility was confirmed by conducting five crystal growth experiments. As a result, the frequency of occurrence of twin defects was 1 in 5.

From the above results, the angles θa and θ of the crystal shoulder are
b are different, and they are 30 degrees or more and 75 degrees or less, and the angle θa of the shoulder is 55 degrees or more and θb
It was found that when the value is 55 degrees or less, the generation of twin defects can be further suppressed.

[0041]

As described above, the present invention has the following excellent effects. (1) The frequency of occurrence of twin defects is reduced, and the yield and throughput are significantly improved.

(2) Compared with the case where the seed crystal orientation is grown with <111>, the (100) wafer can be cut out from the crystal in a direction (plane) close to the plane perpendicular to the longitudinal direction of the crystal. Therefore, the processing loss can be reduced, and 1
The number of wafers that can be cut from one crystal also increases.

(3) The cross-sectional shape perpendicular to the longitudinal direction of the boat should be such that the width of the lower portion is narrow, the width of the central portion is wide, and the width of the upper portion is narrow again, especially a shape close to a circle. As a result, the cross-sectional shape of the obtained crystal in the (100) plane direction is close to a circle. Therefore, when obtaining a circular wafer having a (100) plane from a crystal, the crystal can be sliced to obtain a shape similar to the circular wafer as it is, so that the loss due to cutting can be reduced.

[Brief description of drawings]

FIG. 1 is a side view of a crystal to be grown by a boat method.

FIG. 2 is a top view of a crystal to be grown by the boat method.

FIG. 3 is a sectional view of a shoulder portion of a crystal to be grown by the vertical Bridgman method, which is perpendicular to the crystal growth direction.

FIG. 4 is a cross-sectional view taken along the line aa1 of FIG. 3, where the crystal shoulder has the largest angle.

5 is a cross-sectional view taken along the line bb1 of FIG. 3 where the angle of the crystal shoulder is the smallest.

FIG. 6 is a front view of a crystal to be grown by the boat method as seen from the seed crystal side.

FIG. 7 is a side cross-sectional view in the longitudinal direction of a reaction container when a crystal is grown by the boat method.

FIG. 8 is a schematic side view of the inside of a furnace for growing a GaAs crystal by the liquid-sealed vertical Bridgman method.

[Explanation of symbols]

 1: Crystal 2: Seed crystal 3: Boat 4: Ga 5: Reaction vessel 6: As 7: Liquid sealing material 8: Crucible 9: Heater 10: High pressure vessel

Claims (8)

[Claims] 1. A method for producing an AB type compound semiconductor single crystal having a zinc blende type crystal structure using a boat method, wherein the AB type compound semiconductor single crystal to be grown is grown from a seed crystal to a straight body. Regarding the shoulder of the crystal that is the diameter portion, the angle of the shoulder in the horizontal direction with respect to the plane perpendicular to the longitudinal direction of the crystal is θh, and the angle of the shoulder in the vertical direction with respect to the plane perpendicular to the longitudinal direction of the crystal is θv. When it does, 75 degrees>θh>
A method for producing a compound semiconductor single crystal, which comprises growing the crystal with θv> 30 degrees. 2. The shoulder angles θh and θv are 75 degrees> θh
The method for producing a compound semiconductor single crystal according to claim 1, wherein> 55 °>θv> 30 °. 3. A seed of an AB-type compound semiconductor single crystal to be grown in a method of growing an AB-type compound semiconductor single crystal having a zinc blende type crystal structure in a substantially vertical direction such as a vertical Bridgman method. When the shoulder portion of the crystal, which is the increased diameter portion from the crystal to the straight body portion, is viewed in two cross sections which are parallel to the crystal longitudinal direction and orthogonal to the central axis in the crystal longitudinal direction, the shoulder portion in the two cross sections is A method for producing a compound semiconductor single crystal, wherein angles θa and θb formed with a plane perpendicular to the crystal longitudinal direction are θa ≠ θb. 4. The shoulder angles θa and θb are 75 degrees> θa.
The method for producing a compound semiconductor single crystal according to claim 3, wherein>θb> 30 degrees. 5. The angles θa and θb of the shoulders are 75 degrees> θa
The method for producing a compound semiconductor single crystal according to claim 4, wherein> 55 degrees>θb> 30 degrees. 6. The method for producing a compound semiconductor single crystal according to claim 1, wherein one <100> equivalent direction of the seed crystal is substantially parallel to the crystal longitudinal direction. 7. An apparatus for producing an AB type compound semiconductor single crystal having a zinc blende type crystal structure by using a boat method, wherein the AB type compound semiconductor single crystal to be grown is increased from a seed crystal to a straight body part. Regarding the shoulder of the crystal that is the diameter portion, the angle of the shoulder in the horizontal direction with respect to the plane perpendicular to the longitudinal direction of the crystal is θh, and the angle of the shoulder in the vertical direction with respect to the plane perpendicular to the longitudinal direction of the crystal is θv. When it does, 75 degrees>θh>
An apparatus for producing a compound semiconductor single crystal, wherein a boat inner surface corresponding to the shoulder is formed so that θv> 30 degrees. 8. A seed of an AB type compound semiconductor single crystal to be grown in an apparatus for growing an AB type compound semiconductor single crystal having a zinc blende type crystal structure in a substantially vertical direction, such as a vertical Bridgman method. When the shoulder portion of the crystal, which is the increased diameter portion from the crystal to the straight body portion, is viewed in two cross sections which are parallel to the crystal longitudinal direction and orthogonal to the central axis in the crystal longitudinal direction, the shoulder portion in the two cross sections is 1. An apparatus for producing a compound semiconductor single crystal, wherein a boat inner surface corresponding to the shoulder is formed so that angles θa and θb formed with a plane perpendicular to the crystal longitudinal direction are θa ≠ θb.