JPH0761886A - Production of single crystal and compound semiconductor and production device therefor - Google Patents

Abstract

PURPOSE:To suppress occurrence of lineage defect and to improve yield by using an electric furnace for producing crystal having a specific effective inner diameter. CONSTITUTION:One direction equivalent to <100> direction of single crystal of compound semiconductor having crystal structure of zincblende type is made <=30 deg. based on the longer direction of a boat 2. A reactor 3 having sealed a boat 2 charged with a raw material is arranged in an electric furnace for producing crystal having an effective inner diameter D of <= three times height H of crystal 1 to be grown and the raw material in the boat 2 is melted. The raw material melt in the boat 2 is gradually solidified from one end at a given temperature gradient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for producing a compound semiconductor single crystal by a boat method such as a horizontal Bridgman method (HB method), a zone melt method or a temperature gradient method (GF 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 generally in the <111> direction parallel to the longitudinal direction of the boat, and the wafer surface of the crystal is the (100) plane. As described above, the wafer is cut out obliquely at a predetermined angle with respect to the crystal longitudinal direction (growth direction). 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. As a reported example, Japanese Patent Laid-Open No. 1-
139223, JP-A-2-11165, Japanese Patent Application No. 3-195846 by the present applicant, Japanese Patent Application No. 4-82792.
There are issues, etc.

The <111> direction growth and the <100> direction growth are compared. The crystal growth direction that is conventionally generally
If the direction is equivalent to the 111> direction, (100)
In order to cut out a wafer obliquely with respect to the crystal longitudinal direction, for example, when cutting out a wafer having a diameter of 50 mm, a required crystal height of 35 mm was sufficient. On the other hand, in the case where the crystal growth direction is made equivalent to the <100> direction as in the present invention, the crystal height for cutting the same 50 mmφ wafer is at least 50 mm.
Will be needed. As described above, in the <100> direction growth, it is necessary to increase the height of the crystal.

Further, the cross-sectional shape of the boat perpendicular to the longitudinal direction is generally a semicircular shape or a U-shape which is used in the <111> direction growth. In <100> direction growth, it is necessary to use a boat having a shape close to a circle in order to efficiently cut a circular (100) wafer, and the width near the center of the crystal is made larger than the width at the top of the crystal. Furthermore, it is necessary to reduce the width at the bottom of the crystal.

However, the growth in the <100> direction is <11
Lineage defects, which are crystal defects, are much more likely to occur than in 1> direction growth. In particular, many lineage defects are generated from above the crystal, resulting in a decrease in yield.

As a means for preventing the occurrence of this lineage defect, at least a part of the upper surface (free surface) of the crystal straight body portion to be grown is almost vertical to the longitudinal direction of the boat (11).
1) The appearance of an equivalent crystal habit (facet) on the surface,
Or the upper surface (free surface) of the straight body of the crystal to be grown
Of at least part of the three (11
1) Means for improving the crystal growth interface shape of the crystal horizontal cross-section, which is the cause of lineage defects, by causing the appearance of crystal habits (facets) equivalent to the plane, is also disclosed in Japanese Patent Application No. 5-176232 by the present applicant. Has been proposed by.

Also, there are almost no reports on the effective inner diameter and crystal height of an electric furnace for crystal production (crystal growth furnace). <1
In the case of 11> direction growth, a good crystal can be grown without being significantly affected by the ratio of the effective inner diameter of the crystal growing furnace to the crystal height. In our experiments, the crystal height was about 3
Even if a crystal growing furnace having an effective inner diameter of about twice or about five times is used, a sufficiently good crystal can be obtained.

On the other hand, regarding the <100> direction growth, there is no report on the effective inner diameter of the crystal growth furnace.
Therefore, there is no guideline for designing a crystal growth furnace for <100> direction growth, and the same ratio of effective inner diameter to crystal height of the crystal growth furnace as in <111> direction growth is selected.

[0009]

The object of the present invention is <1.
A crystal growth furnace effective inner diameter and a crystal height required for designing a crystal growth furnace in which lineage defects are less likely to occur in the 00> direction growth are clarified.
It is intended to improve the yield in the> direction growth.

[0010]

The present invention has been made to solve the above-mentioned problems, and in a method for producing a compound semiconductor single crystal having a zinc blende type crystal structure by the boat method, the compound semiconductor It is recommended to use an electric furnace for producing a crystal, in which one direction equivalent to the <100> direction of a single crystal is set within 30 ° with respect to the boat longitudinal direction and which has an effective inner diameter not more than 3 times the height of the crystal to be grown. Provided is a method for producing a characteristic compound semiconductor single crystal.

Also, a compound semiconductor single crystal having a zinc blende type crystal structure is manufactured by the boat method so that one direction equivalent to the <100> direction is within 30 ° with respect to the longitudinal direction of the boat. An apparatus for producing a compound semiconductor single crystal, characterized in that an effective inner diameter of an electric furnace for producing a crystal is set to 3 times or less of a height of a crystal to be grown.

The structure of the present invention will be described in detail below. As shown in FIG. 1, a method for producing a compound semiconductor single crystal according to the present invention is performed by enclosing a boat 2 containing raw materials in a reaction vessel 3 and placing the reaction vessel 3 in a crystal growth furnace having a predetermined temperature gradient. The raw material melt in the boat is gradually solidified from one end to obtain a single crystal. The electric furnace (crystal growth furnace) for producing a compound semiconductor crystal has an elongated shape that extends in the horizontal direction as a whole to accommodate the reaction tube, and is arranged inside the heat insulating material 6 and has a plurality of zones in which electric power can be independently applied. It is composed of a heater 5 and the like.

Here, an electric furnace for crystal production (crystal growth furnace)
The effective inner diameter of is the inner diameter of the furnace core tube (soaking tube) when the furnace core tube (soaking tube) 4 is arranged inside the heater wire, and is composed of a heater wire and a heat insulating material when the furnace core tube is not used. It is determined by the inner diameter of the space that accommodates the reaction container.

FIG. 1 is a sectional view perpendicular to the longitudinal direction of a crystal growth furnace using a furnace core tube. In the figure, D is the inner diameter of the furnace core tube, H
Indicates the height of the crystal to be grown. In the present invention, the effective inner diameter D of the crystal growing furnace needs to be 3 times or less the height H of the crystal to be grown, and further 2.5 times or less is preferable because the effect is large. Further, it is preferable that the amount is about twice, because the crystal can be grown with good reproducibility.

If the effective inner diameter of the crystal-growing furnace is made too small with respect to the height of the crystal to be grown, the reaction vessel may not be inserted or the reaction vessel may be deformed at a high temperature during crystal production to grow the crystal. There are inconveniences such as the inability to remove the reaction vessel from the furnace. Therefore, the effective inner diameter of the crystal growth furnace is preferably larger than the outer diameter of the reaction vessel by 10 mm or more.

The seed crystal orientation is selected so that one direction equivalent to the <100> direction, which is the crystal growth direction, and the <110> direction, which is perpendicular to the crystal growth direction, is substantially vertically upward, and the crystal straight body portion to be grown. On at least a part of the upper surface (free surface) of the crystal, a crystal habit (facet) equivalent to a (111) plane close to the vertical direction of the boat and two other (111) planes not parallel to the facet are equivalent to Crystal habit (facet)
It is preferable that the presence of is effective in further reducing lineage defects.

Further, as the orientation of the seed crystal, when viewed from the crystal growth direction (tail side), the orientation of the seed crystal is <100.
> Four (1) adjacent to the (100) equivalent plane perpendicular to the direction
11) Among the equivalent planes, if the crystal to be grown is a group 3-5 compound semiconductor, the group 5 element plane should be selected upward, and if it is a group 2-6 compound semiconductor, the group 6 element plane should be selected upward. It is preferable because it has a stable appearance and is effective in suppressing lineage defects.

This seed crystal orientation is GaA of a Group 3-5 crystal.
Taking the case of the s crystal as an example, the pit shape generated when a wafer cut out perpendicularly to the <100> direction of the seed crystal is etched by molten KOH is as shown in FIG. Then, the orientation of the seed crystal exhibits a horizontally long shape (a) and a vertically long shape (b) on the tail side surface.

Further, in the crystal growth interface shape on both sides in contact with the boat in the crystal horizontal cross section within at least 10 mm in the depth direction from the free surface of the crystal to be grown, it grows with the boat as shown in FIG. The angle θ formed by the interface is preferably 60 ° or more from the seed crystal side.

Further, in the cross-sectional shape perpendicular to the longitudinal direction of the crystal, the shape of the growth interface in the horizontal direction of the crystal is above the portion where the width is largest, that is, in the portion where the normal direction of the crystal surface is above the horizontal direction. The above is more effective and preferable for suppressing lineage defects. Further, it is more preferable that the shape of the growth interface in the horizontal direction is entirely convex (convex toward the tail side of the boat) over the entire crystal.

Regarding the orientation of the seed crystal, one angle equivalent to the <100> direction forms an angle with the longitudinal direction of the boat within 30 °, and preferably within 30 ° in the vertical direction, so that the solid-liquid interface can be formed. It is preferable that the facets are easily symmetrical. Further, by making the <100> direction parallel to the longitudinal direction of the boat, it is easy to cut out a (100) equivalent plane wafer, which is preferable.

Further, the projection vector of the <110> equivalent direction vector perpendicular to the <100> equivalent direction of the seed crystal orientation to the cross section perpendicular to the boat longitudinal direction is directly related to the boat on the surface of the crystal to be grown. By making it coincide with one of the normal directions to the non-contact surface, facets on the free surface are likely to occur, which is preferable. Furthermore, it is more preferable that the <110> direction is directed vertically upward, since the facet shape is likely to be bilaterally symmetric and three types of non-parallel facets are likely to occur.

In the case of a GaAs crystal of a Group 3-5 crystal, a pit shape generated when a wafer cut out perpendicularly to the <100> direction of the seed crystal is etched by molten KOH is as follows. The seed crystal has a laterally long shape (FIG. 4A) on the seed side surface of the wafer and a vertically long shape (FIG. 4B) on the tail side surface, that is, when viewed from the crystal growth direction (tail side). Of four (11) adjacent to the (100) equivalent plane perpendicular to the <100> direction of
1) Of the equivalent planes, when the crystal to be grown is a group 3-5 compound semiconductor, the group 5 element plane is selected upward, and when the crystal is a group 2-6 compound semiconductor, the group 6 element plane is selected upward, so that It is preferable because it can appear stably.

As a cross-sectional shape perpendicular to the longitudinal direction of the boat, a shape in which the width of the bottom is narrow, the width of the center is wide, and the width of the top is narrow again is small in the circularization loss of the sliced wafer. Therefore, it is preferable that it is an arc or an elliptical arc. Quartz glass, PBN, AlN and the like are suitable as the boat material.

The compound semiconductor single crystal having a zinc blende type crystal structure in the present invention corresponds to a Group 3-5 compound semiconductor single crystal such as GaAs and InP and a Group 2-6 compound semiconductor single crystal such as ZnSe. .

[0026]

It has been experimentally clarified that the effective inner diameter of the crystal-growing furnace has a great influence on the crystal defects, which has never been paid attention to in the <100> direction growth, and the effectiveness of the crystal-growing furnace like that of the present invention is improved. It was found that the range of inner diameters was optimal. The reason for this is not always clear, but the reasons presumed to be the experimental results by the present inventors are summarized below.

When a boat having a semicircular cross section is used to grow in the <111> direction, the effective inner diameter of the crystal growing furnace generally used is D / H (D is the effective inner diameter of the crystal growing furnace,
H is the crystal height to be grown) is 3 or more, and although the conventional upper limit is not clear, a sufficiently good crystal can be obtained even when D / H = 5. Therefore, even with <100> growth, D / H =
As 3.5, a growth experiment was conducted using a boat having a circular cross section. However, lineage defects were likely to occur on both sides of the grown crystal, and it was not possible to obtain a good crystal with good yield.

Therefore, the ratio D / H of the effective inner diameter D of the crystal growing furnace and the crystal height H to be grown is 4, 2.5, 2, 1.7.
The experiment was conducted with four types. As a result of the experiment, in the case of D / H = 4, lineage defects were likely to occur on both sides of the crystal as in the case of 3.5, which was not preferable. On the other hand, D
When /H=2.5, 2, 1.7, good crystals could be obtained without generation of lineage defects.

Schematic plan views of the growth interface shape on the crystal free surface during crystal growth when D / H = 2 and 2.5 are shown in FIGS. 2 (a) and 3 (a), respectively. The results of observation of the growth interface by etching of the horizontal section of 10 mm below the free surface of the crystal thus obtained are shown in FIGS. 2B and 3B, respectively.

FIG. 4 is a schematic plan view of the growth interface shape on the crystal free surface during crystal growth when D / H = 4.
FIG. 4 shows the observation result of the growth interface by etching of the horizontal section of 10 mm below the free surface of the grown crystal in (a).
They are shown in (b).

These experiments were conducted under temperature conditions in which facets were easily generated on the crystal free surface so that lineage defects were less likely to occur.

What is characteristic here is that as the D / H increases, the width of the (111) equivalent facet 8a, which appears in the growth interface of the free surface and is perpendicular to the growth direction, tends to increase. In particular, in FIG. 4A where D / H> 3, it can be seen that the facets are generated over the entire crystal width and the growth interface is flat. On the other hand, in FIG. 2A and FIG. 3A where D / H <3, (111) equivalent facets 8b and 8c with different angles are provided on both sides of the facet that appears perpendicular to the growth direction. Appeared,
The growth interface shape on the free surface is convex with respect to the melt as a whole.

When D / H> 3, lineage defects are likely to occur. When the growth interface shape on the free surface becomes flat due to facets as shown in FIG. 4A, the growth interface shape below the free surface becomes It is considered that it is W-shaped as shown in FIG. 4B, and portions that are concave with respect to the melt are generated on both sides, and dislocation defects are concentrated in these portions, and lineage defects are likely to occur.

On the other hand, when D / H <3, the shape of the growth interface on the free surface is three types of non-parallel facets 8
It is composed of a, 8b, and 8c and is convex with respect to the melt. The growth interface shape under the free surface is also perfectly convex (Fig. 3
(B)), it is considered that lineage defects are unlikely to occur.

The cause of the difference in the growth interface shape of the free surface depending on D / H is considered as follows. In the upper part of the crystal growth furnace, a radiation window for monitoring (Fig.
7) is attached. This radiating window not only has the effect of giving a temperature difference in the vertical direction by cooling the upper direction in the furnace core tube, but also has the effect of lowering the central portion of the temperature distribution in the horizontal radial direction in the furnace core tube and lowering both sides. is there.

By reducing the effective inner diameter (inner diameter of the furnace core tube) of the crystal growing furnace for the crystal, the free surface position of the crystal is relatively positioned in the upper part of the furnace core tube, and the growth is attached to the upper part of the furnace core tube. The distance from the heat radiation window (monitoring window) near the interface becomes shorter. As a result, the temperature difference between the upper center of the crystal and both sides is substantially increased, and the shape of the growth interface is considered to be convex with respect to the melt as shown in FIG.

From these facts, it is considered that lineage defects in <100> growth do not occur by setting D / H to 3 or less.

Further, the reason why lineage defects are apt to occur in the <100> direction growth with D / H> 3 and the lineage defects do not occur in the <111> direction growth is not always clear. The difference in the crystallographic growth direction and the difference in the boat shape used by each of the two growth directions are considered.

The difference between the boat shapes generally used in the two growth directions is that, when the crystal growth direction that has been generally used in the past is equivalent to the <111> direction as described above, the boat shape is in the longitudinal direction of the boat. The vertical cross-sectional shape is generally semicircular or U-shaped, but in <100> direction growth, in order to efficiently cut a circular wafer perpendicular to the crystal longitudinal direction,
It is necessary to use a boat having a shape close to a circle in which the width near the center of the crystal is larger than the width of the top of the crystal and the width is smaller at the bottom of the crystal.

In order to clarify the difference in the occurrence of lineage defects due to the difference in crystallographic growth direction, the inventors of the present invention have boats of the same shape with a semicircular cross section and the same crystal growth furnace (D / H = 3.5), using the same furnace temperature distribution,
Comparative growth experiments were carried out for two types of growth, i.e., 111> direction and <100> direction. As a result, a good crystal could be obtained in the <111> direction growth, but a good product could not be obtained in the <100> direction growth because lineage defects occurred. From this, the difference in crystallographic growth direction is
It is considered that the generation of lineage defects is promoted in the <100> direction growth for some reason.

Further, as described above, the difference in the temperature distribution of the crystal and the convection of the raw material melt also appears due to the difference in the boat shape that is generally used, which also promotes the generation of lineage defects by the <100> direction growth. It is highly possible that

[0042]

EXAMPLES Examples for producing a GaAs single crystal will be described below. A boat having a circular cross-sectional shape of approximately 80% perpendicular to the longitudinal direction of the crystal-growing boat was used, and the crystal to be grown was <10 parallel to the boat longitudinal direction.
The seed crystal was installed so that one direction equivalent to the <110> direction, which is orthogonal to one direction equivalent to the 0> direction, is substantially vertical.

The height of the crystal to be grown was set to 52 mm so that a wafer having a diameter of 50 mmφ could be cut out. As shown in FIG. 6, 4000 g of Ga (reference numeral 11) was put in the boat 2 and 4350 g of As (reference numeral 13) was added to the other end of the reaction vessel 3.
Then, the inside of the reaction vessel 3 is depressurized to a vacuum state and sealed. Next, the reaction vessel 3 is put into a crystal growth furnace having an inner diameter of the furnace core tube of 104 mm, As in the reaction vessel 3 is heated to 600 ° C., and As vapor pressure in the reaction vessel 3 is maintained at 1 atm. The boat in the reaction vessel 3 is further heated to react Ga with As vapor to synthesize GaAs. Then, the seed crystal 12 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.

At this time, the growth interface shape of the free surface had facets as shown in FIG. After completely solidifying, the temperature was further lowered to room temperature, and a GaAs single crystal could be obtained.

The obtained crystals were of good quality without lineage defects. When the growth interface shape of a horizontal section of 10 mm below the free surface of this crystal was observed by etching, the angle θ between the growth interface 9 and the boat was about 140 ° as shown in FIG.

When a (100) plane circular wafer is prepared from the obtained crystal, the cross section of the obtained crystal in the (100) plane direction can be formed into a shape close to a circle. Due to the boat shape, when obtaining a (100) circular wafer from a single crystal, a shape close to a circular wafer can be obtained by slicing vertically to the crystal longitudinal direction. Therefore, it is possible to reduce the loss due to cutting.

[0047]

As described above, the present invention has the following excellent effects.

(1) When the seed crystal orientation is grown to <100>, the generation of lineage is suppressed and the yield is improved by optimizing the effective inner diameter of the crystal growth furnace.

(2) By setting the effective inner diameter of the crystal growing furnace to 3 times or less of the crystal height, the crystal growing furnace can be downsized and the manufacturing cost of the crystal growing furnace can be reduced. (3) Compared with the case where the seed crystal orientation is <111>,
When a (100) wafer is cut out from a crystal, it can be cut out in a direction close to a direction perpendicular to the longitudinal direction of the crystal. For this reason,
Processing loss can be reduced, and the number of wafers that can be cut out from one crystal increases.

[Brief description of drawings]

FIG. 1 is a cross-sectional view perpendicular to the longitudinal direction of a crystal growth furnace and a boat according to the present invention.

FIG. 2 shows an embodiment of the present invention, which is a crystal growth interface shape when D / H = 2, (a) is a plan view of a free surface growth interface shape during crystal growth, and (b) is a crystal growth interface. Plan view of the growth interface shape of the crystal horizontal section of 10 mm in the depth direction from the free surface of

FIG. 3 shows an embodiment of the present invention, which is a crystal growth interface shape when D / H = 2.5, (a) is a plan view of a free surface growth interface shape during crystal growth, and (b) is a crystal. Plan view of the growth interface shape of a crystal horizontal section of 10 mm in the depth direction from the free surface during growth

FIG. 4 shows a conventional example, which is a crystal growth interface shape when D / H = 4, (a) is a plan view of a free surface growth interface shape during crystal growth, and (b) is a free surface during crystal growth. Plane view of the growth interface shape of the crystal horizontal section of 10 mm in the depth direction

FIG. 5 shows an example of a pit shape obtained by etching a wafer cut out from a GaAs crystal grown by the present invention with molten KOH. (A) is a front view of the pit shape on the seed side surface of the wafer, (b) is a wafer Front view of the pit shape on the side of the tail

FIG. 6 is a side cross-sectional view of the inside of a reaction container when a crystal is produced by the boat method.

[Explanation of symbols]

1: Crystal 2: Boat 3: Reaction vessel 4: Furnace core tube 5: Heater wire 6: Heat insulating material 7: Radiating window 8a: Non-parallel crystal habit (facet) equivalent to three kinds of (111) 8b: Non-parallel 3 Equivalent crystal habit (facet) 8c: Not parallel 3 crystal habits (facet) equivalent to (111) 9: Convex growth interface 10: W-type growth interface 11: Ga 12: Seed crystal 13: As

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // H01L 21/208 T

Claims (2)

[Claims] 1. A method for producing a compound semiconductor single crystal having a zinc blende type crystal structure by a boat method, wherein one direction equivalent to the <100> direction of the compound semiconductor single crystal is 30 with respect to the boat longitudinal direction. A method for producing a compound semiconductor single crystal, characterized in that an electric furnace for producing a crystal having an effective inner diameter within 3 ° and a height of a crystal to be grown is 3 times or less is used. 2. A manufacturing method of manufacturing a compound semiconductor single crystal having a zinc blende type crystal structure by a boat method such that one direction equivalent to the <100> direction is within 30 ° with respect to the longitudinal direction of the boat. An apparatus for producing a compound semiconductor single crystal, characterized in that the effective inner diameter of an electric furnace for producing a crystal is not more than 3 times the height of the crystal to be grown.