JPH05279165A - Apparatus for producing compound semiconductor single crystal - Google Patents

Abstract

PURPOSE:To enable prevention of generation of twin defects and improvement of the yield and the throughput, in producing a compound semiconductor single crystal by the boat method. CONSTITUTION:In the seed crystal-setting part of a boat 3, a seed crystal is put at a position projecting by 5mm toward the shoulder part side from the inflection point from the seed crystal-setting part of the boat 3 to the shoulder part. The crystal growth side end part of the seed crystal 1 is an upward inclined plane formed by cutting one edge of a rectangular parallelepiped. The angle between the above-mentioned inclined plane and the horizontal plane is about 35 deg..

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 the boat method.

[0002]

2. Description of the Related Art In recent years, in the field of electronics industry, various researches have been conducted on various methods for inexpensively producing a compound semiconductor single crystal such as GaAs, InP, InAs having few crystal defects.

As a method for producing a compound semiconductor single crystal,
The boat method and pulling method are well known. Among them, the boat method produces a single crystal with few crystal defects because the temperature gradient is smaller than the pulling method and stoichiometry control is easy. There is an advantage that can be.

The boat method includes the horizontal Bridgman method (HB
Method) and the temperature gradient method (GF method). In both cases, the raw material melt is put in a long boat having a seed crystal at one end, and the boat is sealed in an ampoule tube, and the ampoule tube is placed in the longitudinal direction. This is a method of producing a single crystal by placing it in a horizontal furnace provided with a temperature gradient and solidifying the crystal from the seed crystal side.

When the compound semiconductor single crystal is manufactured by the boat method, it is about 20 to 30% or less of the area of a cross section of the compound semiconductor single crystal to be manufactured which is perpendicular to the longitudinal direction of the straight body part. Generally, a seed crystal having an area cross section is used, and a shoulder portion for gradually increasing the crystal diameter from the seed crystal to reach the target diameter of the straight body portion of the single crystal is provided. At this time, twin defects are likely to occur in the neck portion of the crystal from the seeding surface of the seed crystal to the shoulder portion, resulting in an increase in the number of meltback operations and a reduction in throughput and yield.

FIG. 2 shows a side sectional view of a conventional boat during the growth of a conventional crystal. Since a neck portion of a crystal having a diameter substantially the same as the diameter of the seed crystal 2 is present in the seed crystal 2 from the end on the crystal growth side of the conventional seed crystal 2 to the shoulder portion, the seed crystal 2 has The seeding step of contacting the raw material melt was performed stably. After performing the seeding step in this way, a single crystal was manufactured by a method of increasing the crystal diameter at the shoulder. Figure 2
In FIG. 3, reference numeral 3 indicates a boat, and 4 indicates a raw material melt.

[0007]

As described above, in the case of producing a conventional single crystal, a neck portion having substantially the same diameter as that of the seed crystal is formed from the seed crystal, and then the crystal diameter is gradually increased to form a straight portion of the single crystal. It was common to bring the torso to the target diameter. However, there has been a problem that twin defects, which are serious crystal defects, are likely to occur at the time of forming the neck portion, and when twin defects are generated, the yield and the throughput are significantly reduced.
In particular, when one direction equivalent to the <100> direction of the seed crystal is made substantially parallel to the boat longitudinal direction, twin defects from this neck frequently occur, which is a serious problem.

Table 1 below shows the occurrence frequency of twins in the neck, shoulders, and straight body when the crystal was grown 10 times in the longitudinal direction of the boat in the seed crystal orientation <100>. As can be seen from Table 1, twin defects are concentrated in the neck. Further, a sketch of a typical crystal after etching of a vertical cross section in the longitudinal direction from the neck to the shoulder is shown in FIG. From this figure, it can be seen that crystal habits (facets) 5 having a different crystal growth mechanism from the other parts are concentrated in the neck. Since this facet is likely to be a starting point of twin defects, it can be inferred that twin defects frequently occur from the neck.

[0009]

[Table 1]

Therefore, for example, as an example of a technique for reducing twin defects, a neck portion of a crystal having substantially the same width as that of the seed crystal does not exist between the seed crystal and the shoulder.
It is conceivable that the end of the seed crystal on the side in contact with the raw material melt may be further projected to the shoulder side beyond the inflection point from the seed crystal installation portion to the shoulder.

However, as shown in FIG. 2, the conventional seed crystal has a substantially rectangular cross section (the overall shape is a substantially rectangular parallelepiped or a semi-cylindrical shape). The boundary between the seed crystal and the seed crystal (hereinafter referred to as the S / L interface of the seed crystal) became very difficult to see, and it was very difficult to adjust the temperature at the S / L interface of the seed crystal. Therefore, it often happens that the seed crystal is largely melted. In the boat method, the temperature gradient is generally as small as 5 ° C / cm or less, and therefore the end of the seed crystal that comes into contact with the raw material melt during seeding (when starting the crystal growth by bringing the raw material melt into contact with the seed crystal). It is common for the part to melt for several to 10 mm, and the seed crystal melted more than usual due to the subtleties of temperature adjustment.

Therefore, the neck portion of the crystal is regenerated or becomes longer, the crystal grows in the neck portion, and twin defects are likely to occur, resulting in a decrease in yield and throughput.

The present invention has been made in view of the above problems, and an object thereof is to provide an apparatus for producing a compound semiconductor single crystal for reducing the frequency of occurrence of twin defects, which significantly lowers the yield and the throughput. is there.

[0014]

In order to achieve the above object, the present invention is characterized in that, in an apparatus for producing a compound semiconductor single crystal by a boat method, a crystal growth side end of a seed crystal is an upward slope. An apparatus for producing a compound semiconductor single crystal is provided.

The present invention will be described in more detail below. In the present invention, for example, a compound semiconductor single crystal such as GaAs, InP, or InAs is manufactured by a known boat method. The boat method is to put the raw material melt in a long boat with a seed crystal at one end, to enclose the boat in an ampoule tube, and to put this ampoule tube in a horizontal furnace with a temperature gradient in the longitudinal direction. This is a method of producing a single crystal by solidifying the crystal from the crystal side. As described above, the boat method includes the horizontal Bridgman method (HB method) and the temperature gradient method (GF method), but any method may be used. Also, the ampoule tube used,
As the horizontal furnace, the raw material melt, and the like, those used in the conventional method can be used as they are.

In the present invention, the end on the crystal growth side is set to 20.
By installing a seed crystal having an inclined surface with an angle of ≧ ° in the seed crystal installation part having a diameter substantially the same as the seed crystal outer diameter of the crystal growth boat, the S / L interface part of the seed crystal at the time of seeding Is easier to see. As a result, the temperature can be easily adjusted while observing the dissolution of the seed crystal in the raw material melt.

Further, if the length of the neck portion of the crystal from the seed crystal to the shoulder portion of the crystal is set to 5 mm or less, it is possible to suppress the generation of twin defects which are likely to occur in the neck portion.
More preferable. Furthermore, in order to eliminate the neck, when installing the seed crystal in the seed crystal installation part of the boat, the position of the end part of the seed crystal on the crystal growth side should be adjusted from the inflection point existing between the seed crystal installation part and the shoulder part to the shoulder part. It is more preferable to install it so as to protrude to the side, because the neck portion of the crystal that is regenerated by melting the seed crystal becomes shorter and twin defects are less likely to enter.

Here, when the position of the end portion of the seed crystal on the crystal growth side is on the seed crystal installation portion side with respect to the inflection point and the distance L between the inflection points is represented by +, the crystal growth of the seed crystal is shown. If the position of the side end is projected toward the shoulder side from the inflection point and the distance L between the inflection points is represented by −, L is −15.
The range of ≦ L ≦ + 5 is preferable. When L is larger than +5, the neck portion becomes long and twin defects are likely to occur, which is inconvenient, and when L is smaller than -15 (protruding toward the shoulder side), the seeding step becomes difficult, which is preferable. Absent.

Further, crystal growth is performed with the <100> direction of the orientation of the seed crystal substantially parallel to the longitudinal direction (growth direction) of the crystal.
0) Since the wafer can be cut out, cost merit is increased, which is preferable. The shape of the seed crystal is a substantially rectangular parallelepiped shape, a semicylindrical shape or the like having a substantially rectangular cross section, and is formed such that the end surface on the crystal growth side is an upward slope.

[0020]

As shown in Table 1, twin defects are likely to occur in the crystal neck. It is considered that this is because many crystal habits (facets) 5, which can be the origin of twin defects, are generated in the neck portion as shown in FIG. The reason why a lot of facets are generated in the neck is considered as follows. The amount of high-temperature melt that is in contact with the growing crystal during neck growth is extremely smaller than during growth of other parts. Therefore, it is considered that the facet is likely to occur because the temperature gradient in the vicinity of the solid-liquid interface is smaller than that in the growth of other portions and the supercooling is large.

In the present invention, twin crystal defects are generated by shortening the neck portion of the crystal in which twin defects are likely to occur as described above, or by directly growing the shoulder portion from the seed crystal without forming the neck portion. Can be suppressed. Further, the state of the melted seed crystal can be clearly observed through the viewing window of the single crystal growth furnace, and the melted amount of the seed crystal can be easily controlled. Further, since the neck portion of the crystal in which twin defects are likely to occur can be shortened or eliminated, the occurrence of twin defects can be suppressed.

[0022]

【Example】

(Example) An example of growing a GaAs single crystal will be described below. In FIG. 1, a boat 3 has a seed crystal 1
And the raw material melt 4 are put in and the state immediately after the seeding step is shown. The position where the seed crystal is installed in the seed crystal installation part of the boat 3 for growing a crystal, which has a diameter substantially the same as the outer diameter of the seed crystal,
As shown in the figure, the position was set to be 5 mm closer to the shoulder side than the inflection point from the seed crystal installation portion of the boat to the shoulder portion which is the increased diameter portion. The crystal growth side end of the seed crystal 1 has a shape in which one end of a rectangular parallelepiped is cut out to form an upward slope. The angle of the slope with respect to the horizontal plane is about 35 °.

The angle of the inclined surface with respect to the horizontal plane is preferably in the range of about 20 ° to 70 ° so that the S / L interface of the seed crystal can be clearly observed from the observation window of the single crystal growing furnace. If it is less than 20 °, it is easy to observe the S / L interface position, but it is inconvenient in that the length of the inclined surface becomes long and the seed crystal becomes unnecessarily long.
It is not preferable because it is difficult to observe the position of the / L interface.

The GaAs seed crystal 1 was set so that the <100> direction and the boat longitudinal direction were substantially parallel to each other. Ga2100g is put in the boat 3, and As is added to the other end of the reaction vessel.
Put 300 g and depressurize the inside of the reaction vessel to a vacuum state and seal. Next, put the reaction vessel in the crystal growth furnace and
s is heated to 600 ° C. and the vapor pressure of As in the reaction vessel is set to 1 at
m, keep the boat in the reaction vessel at 1200 ° C, and
GaAs is synthesized by reacting a and As vapor. afterwards,
The temperature of the seed crystal was further raised to 1238 ° C., the temperature gradient in the GaAs melt was set to about 0.5 ° C./cm, and the seed crystal and GaA were changed.
s Contact the melt.

At this time, by adopting a seeding method of bringing the melt into contact with a seed crystal having an upward slope on the crystal growth side end, while observing the S / L interface portion of the seed crystal from the sight window, the seed crystal is observed. The temperature could be adjusted so that the crystals did not melt into the raw material melt. As a result, the crystal growth could be started without the crystal neck. Then, the temperature of the melt is gradually lowered and cooled to grow a crystal without a neck.
After completely solidifying, the temperature was further lowered to room temperature and the crystals were taken out to obtain 4150 g of GaAs single crystal. A twin crystal defect did not occur, and a crystal could be stably obtained.

(Comparative Example) A conventional neck forming method,
The case of growing a crystal will be described. FIG. 2 shows a state during crystal growth. Regarding the reference numerals in the figure, the same constituents as those in FIG. 1 are designated by the same reference numerals. 2 is a substantially rectangular parallelepiped seed crystal, 3 is a boat, and 4 is a raw material melt. As shown in FIG.
As described above, the position was 30 mm from the inflection point from the seed crystal installation portion of the boat to the shoulder portion that is the increased diameter portion. Hereinafter, the raw material was synthesized in the same manner as in the example, and when the raw material melt was brought into contact with the seed crystal, seeding was performed by pouring the raw material melt into the neck having the same diameter as the seed crystal. Crystal growth was performed in the same manner as in the example.

Since twin defects were generated from the neck during the crystal growth in the comparative example, meltback was performed 5 times by melting the crystals and growing again during the growing process, but single crystals without twin defects were obtained. I couldn't get it.

In the case where crystal growth was carried out in the longitudinal direction of the boat with a seed crystal orientation <100>, when a conventional seed crystal having a neck portion of 30 mm and a substantially rectangular parallelepiped shape was used, the frequency of occurrence of twin defects was 10 times. Twin generation occurred frequently, with the number of occurrence being 33 during 9 times of crystal growth. On the other hand, generation of twin defects when the same growth is performed using a seed crystal having a neck length of 5 mm or less and an end on the crystal growth side having an upward slope in the present invention It was confirmed that the present invention had a great effect on the suppression of twin defect generation, with the frequency being once in 15 times and the number of occurrence being 2.

[0029]

As described above, according to the present invention,
The frequency of occurrence of twin defects, which are fatal defects in single crystal growth, can be greatly reduced. This makes it possible to improve yield and throughput. Further, since the appearance of the S / L interface portion of the seed crystal after seeding can be clearly observed, it becomes easy to control the temperature during seeding,
The crystal neck can be shortened or eliminated.
When the compound semiconductor to be grown is an AB type compound semiconductor having a zinc blende type crystal structure and one direction equivalent to the <100> direction of the seed crystal is substantially parallel to the boat longitudinal direction, Although twin defects are very likely to occur in the neck, the present invention is particularly effective when growing in this growth direction.

[Brief description of drawings]

FIG. 1 shows an embodiment of an apparatus for producing a compound semiconductor single crystal according to the present invention, in which a raw material melt is brought into contact with a seed crystal having an upwardly inclined end on the crystal growth side, and immediately after the seeding, the boat side FIG.

FIG. 2 is a side sectional view of a boat during the growth of crystals by a conventional apparatus.

FIG. 3 is a sketch after etching a cross section in the crystal longitudinal direction from a seed crystal to a shoulder of a crystal grown by a conventional apparatus.

[Explanation of symbols]

 1: Seed crystal 2: Conventional seed crystal 3: Boat 4: Raw material melt 5: Crystal habit (facet) in crystal 6: Growth stripe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoyuki Ishihara 1150 Hazawa-machi, Kanagawa-ku, Yokohama-shi, Kanagawa Asahi Glass Co., Ltd. Central Research Laboratory

Claims (3)

[Claims] 1. An apparatus for producing a compound semiconductor single crystal by a boat method, wherein an end of a seed crystal on a crystal growth side is an upward slope, and the apparatus for producing a compound semiconductor single crystal. 2. In an apparatus for producing a compound semiconductor single crystal by the boat method, the position of the crystal growth side end of the seed crystal is
The distance L between the position and the inflection point in the case of being on the seed crystal installation part side from the inflection point from the seed crystal installation part to the shoulder part of the boat is represented by +, and the position is the shoulder part side as seen from the inflection point. The compound semiconductor single crystal according to claim 1, wherein the seed crystal is installed so that the distance L between the position and the point of inflection when protruding to the side is represented by −, and −15 mm ≦ L ≦ + 5 mm. apparatus. 3. A compound semiconductor single crystal to be grown is an AB type compound semiconductor single crystal having a zinc blende type crystal structure, and one direction equivalent to the <100> direction of the seed crystal is set in the boat longitudinal direction. The apparatus for producing a compound semiconductor single crystal according to claim 1 or 2, wherein seed crystals are installed substantially parallel to each other.