JPH03146494A - Production of compound semiconductor crystal - Google Patents

Abstract

PURPOSE:To prevent the occurrence of strain due to solidification and to reduce defects by keeping the temp. of a range close to the interface between a seed crystal and a melt of a compd. semiconductor higher than the m.p. of the semiconductor when a crystal is grown by the Bridgman method or other method while moving a boat for crystal growth. CONSTITUTION:A semiconductor seed crystal 6 is set at one end of a boat 3 for crystal growth and a polycrystal of a compd. semiconductor to be grown and/or the constituent elements of the semiconductor are housed in the boat 3 in contact with the seed crystal 6. The boat 3 is heated to form a melt 5 of the semiconductor and this melt 5 is successively cooled from the seed crystal side to grow a single crystal. In this boat growth method, the temp. of a range close to the interface between the seed crystal 6 and the melt 5 is kept higher than the temp. of the remaining part of the melt 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing compound semiconductor crystals, particularly Ga
The present invention relates to a method for manufacturing compound semiconductor crystals in which one element has a high dissociation vapor pressure, such as m-v group compounds such as As, InAs, GaP, and InP, and ■-■ group compounds such as Zn-5 and Zn-5e.

[Conventional technology]

Compound semiconductor crystal growth is broadly classified into bulk crystal growth and epitaxy. In particular, bulk crystals are grown by cooling and solidifying a melt consisting of the constituent elements of a compound semiconductor.

Figures 2 and 2 show such bulk crystal growth methods, respectively.
Horizontal Brldgma shown in FIGS. 3 and 4, respectively.
n (Bridgeman) method, Gradient Free
ze (grady end freeze) method and 2one Me
The lting (zone melting) method is mainly known.

In the horizontal Bridgman method, a boat containing a polycrystalline compound semiconductor or at least one of its constituent elements and a furnace for heating the boat to form a melt of the compound semiconductor are moved relative to each other. The day-end freeze method is a boat growth method in which crystals are grown by lowering the temperature while maintaining a temperature gradient. The zone melting method is a method in which only a portion of a compound semiconductor polycrystal serving as a raw material is melted and the melted portion is moved to grow the crystal.

The Bridgman method and other methods are mainly used in horizontal and vertical types as shown in the figure.

Also, what is important when growing these compounds is that
These include solid-liquid interface control and extraction cooling process control to obtain good crystals, control of impurities mixed in from the container, and control of the synthesis process so that crystals can be synthesized from each raw material and grown.

Each of these will be explained by taking the above-mentioned crystal growth method as an example.

First, the Bridgman method shown in FIG. 2 will be explained.

In FIG. 2, a low-temperature side reactor 1 and a high-temperature side reactor 2 are communicated via a diffusion barrier, and a crystal growth boat (hereinafter simply referred to as a boat) 3 is arranged in the high-temperature reactor 2. A compound melt 5 is accommodated in the boat 3, and a seed crystal 6 is provided at the tip in the direction of movement, and a seed crystal 6 is provided at the tip in the low-temperature side reactor 1 to contain elements that are easily dissociated among the compound elements. (For example, in GaAs, ^S
) are provided.

The solid line IO shown above each reactor 1.2 shows the temperature distribution, and TX shows the melting point of the compound.

[Problem to be solved by the invention]

This Bridgman method produces T near the seed crystal. Temperature above 7
Crystal growth is performed in a state where there is a steep temperature gradient below M.

This rapid cooling of the growing crystal causes B, P, D, (etch pit density: Btch
Pit Density) or dislocation density becomes high, and the temperature difference between the melting point and the melt cannot be that large, making it difficult to control the solid-liquid interface.Also, when a quartz container is used, oxidation is required to control impurities that enter the container. It was also impossible to control gases.

In the gradient-end freeze method shown in FIG. 3, the temperature distribution in the high-temperature side reactor 2 has a temperature gradient that gradually decreases. Therefore, the temperature gradient near the solid-liquid interface during crystal elongation is small, and even if there is a small disturbance, such as a temperature difference of about 1°C in the direction perpendicular to the crystal growth direction within the free surface of the crystal, the solid-liquid interface will close immediately. A problem occurred that caused confusion.

In addition, in the zone melting method shown in Fig. 4, -
It was necessary to synthesize the carbon compound in advance, which caused problems in productivity.

Therefore, an object of the present invention is to provide a more stable method for crystallizing a compound semiconductor with less solidification strain at the solid-liquid interface.

[Means to solve the problem]

According to the present invention, the above-mentioned problem can be solved by heating a crystal growth boat which has a semiconductor seed crystal at one end and houses a polycrystal or at least one constituent element of a compound semiconductor to be grown in contact with the seed crystal. A method for manufacturing a compound semiconductor crystal by a boat growth method, in which a melt of a compound semiconductor to be grown is formed, and then a single crystal continuous to the seed crystal is grown by sequentially cooling the melt from the side in contact with the seed crystal. The problem is solved by a method for manufacturing a compound semiconductor crystal, characterized in that the temperature distribution is such that the temperature in the vicinity of the interface between the seed crystal and the compound melt to be grown is maintained at a higher temperature than in the rear part of the vicinity of the interface.

[Function] That is, in the present invention, when crystal growth of a compound semiconductor such as GaAs is performed by the boat growth method, the temperature in the vicinity of the interface at the end of the seed crystal on the melt side is set to a temperature higher than the melting point of the compound semiconductor (first temperature). The set temperature is increased to a temperature slightly higher than the melting point (preferably 15 to 30°C higher), and then the temperature is lowered to a temperature slightly higher than the melting point.

2 (preferably a temperature 5 to 15° C. higher), and uses a temperature distribution in which the melt side is maintained at that temperature than near the interface.

The reason why it is preferable to set the first set temperature to 15 to 30 degrees Celsius higher than the melting point is because if it is less than 15 degrees Celsius, it will be difficult to produce an effect due to the temperature gradient, whereas if it exceeds 30 degrees Celsius, the melt will dissociate. It is from.

Further, if the second set temperature is less than 5° C., if a temperature distribution occurs in the furnace, that portion will solidify and form polycrystals. Furthermore, if the temperature exceeds 15°C, the reaction with the boat will become more intense.

In addition, in the present invention, the salt is cooled rapidly after the crystal has solidified, in the direction of reaction progress in the reactor from the seed crystal placement position, in the vicinity of the placement position of the component with high dissociation pressure (As component in the case of GaAs) in the melt. In order to prevent this, the temperature is set to about 1000 to 1200℃, and then the temperature is set to about 620℃ to reduce the amount of As (
dissociation pressure).

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic diagram for explaining the present invention in detail.

The embodiment shown in FIG. 1 is a horizontal boat growth method for GaAs, and a quartz boat was used as the crystal growth boat.

The equipment used in this method may be the same as the equipment used in the conventional method; in this example, a semicircular boat 3 with a width of 75 mm and a length of 550 mm was used to directly synthesize Ga and As, and a 6000 g
GaAs crystals were manufactured with the temperature distribution shown. A reactor is set in a furnace (not shown), and the melting point (TX) is gradually raised from 1238°C in a range of about 100 au from the end of the seed crystal 6 in the boat 3 (solid-liquid interface control zone).
The temperature was set to about 25° C. higher than the humidity temperature, and then the temperature was gradually lowered to a temperature of about 10° C. higher than the humidity temperature, and that temperature was maintained in the subsequent high temperature zone for holding the melt. On the other hand, the temperature in front of the seed crystal 6 is first set at about 1050°C at the longitudinal center of the seed crystal, and maintained until the afterheater zone and the rapid cooling prevention zone;
The temperature was lowered to 620° C. over a length of 0.00 mm and maintained at that temperature before that. In this example, the reactor was moved to the left relative to the furnace as crystal growth progressed from the state shown in the figure. The speed is 2mm/hour ~ 4fflff
It was about 1/hour.

Regarding the GaAs single crystal produced in this way, B at the 100u position on the seed crystal side (solidification rate (g) = O, 15),
P, D, (etch pit density) is 3.6 xio”
/am! , while the tail side 450mm position (assimilation rate (
B, P, D of g) = 0.8) are 4.3 XIO'
/crl was ε, P, D, l;! This was carried out using a KOH melt.

As a comparative example, the same size as this example, width 75 mm and length 5 was used.
Ga and As were directly synthesized using a 50 mm boat, and 6000 g of crystals were produced using the gradient-endofreeze method (3rd phase).
Figure). The second half of the obtained GaAs crystal became polycrystalline with defects and did not become a perfect single crystal.

〔Effect of the invention〕

As explained above, according to the present invention, it was possible to produce a compound semiconductor, particularly a single crystal of GaAs, which is more stable than the conventional method and has fewer defects.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining the present invention in detail. FIGS. 2 to 4 are schematic diagrams for explaining the prior art. In particular, FIG. 2 shows the Horizontal Bridgman method, and FIG. 3 shows the Gradient Freeze method. , FIG. 4C shows the Zone Melting method. l...low temperature side reactor, 2...high temperature side reactor, 3
... Boat for crystal growth, -4... Diffusion barrier, 5... Compound melt, 6... Seed crystal, 7... Substance that dissociates among compounds, Tw... Compound Melting point of 1o...
·Temperature distribution. Fig. 1 Conventional example Fig. 2 Conventional example! Figure 43 Conventional example Atsushi Figure 4

Claims (1)

[Claims] 1. A semiconductor seed crystal is arranged at one end and in contact with the seed crystal,
After heating a crystal growth boat containing at least one of the polycrystals or constituent elements of the compound semiconductor to be grown and forming a melt of the compound semiconductor to be grown, the melt is poured from the side in contact with the seed crystal. In a method for producing a compound semiconductor crystal by a boat growth method in which a continuous single crystal is grown on the seed crystal by sequential cooling, the temperature in a range near the interface between the seed crystal and the compound melt to be grown is adjusted to a temperature behind the range near the interface. A method for manufacturing a compound semiconductor crystal, characterized in that the temperature distribution is maintained at a higher temperature. 2. The method according to claim 1, wherein the crystal growth is performed by moving a boat or a furnace. 3. The method according to claim 1, wherein crystal growth is performed by moving the temperature distribution from the seed crystal side toward the rear end of the boat.