JPH10291890A - Production of compound semiconductor single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a compd. semiconductor single crystal having good reproducibility. SOLUTION: A seed crystal 11 having a carrier concn. higher than the concn. of the crystal to be actually produced is used, by which the thermal conductivity of the seed crystal 11 is made better than the thermal conductivity of the crystal when the thermal conductivity is compared (generally, the electrons in the substance of a metal play a role of propagating heat. There is, therefore, a tendency that the thermal conductivity is high if the carrier concn. is high and GaAs is not an exceptional case). Consequently, the heat eventually flows from the side of the lower thermal conductivity toward the side of the higher thermal conductivity, i.e., the heat eventually flows from the crystal toward the seed crystal 11, by which the radiation of the heat from the seed crystal 11 is accelerated. As a result, the hollowing of the solid liquid boundary is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a compound semiconductor single crystal.

[0002]

2. Description of the Related Art FIG. 3A is a conceptual diagram of a manufacturing apparatus to which a conventional method of manufacturing a compound semiconductor single crystal is applied.
FIG. 3B is a diagram showing a furnace temperature distribution of the manufacturing apparatus shown in FIG. The horizontal axis in FIG. 3B indicates the furnace position, and the vertical axis indicates the furnace temperature.

A method for producing a GaAs single crystal by the boat method, particularly, the GF method will be described.

In a quartz ampoule 1 shown in FIG. 3A, a quartz boat 4 in which Ga (solid) 2 and a seed crystal 3 are arranged, and an As (solid) 5 are housed and vacuum sealed. I do.
The vacuum-sealed ampule 1 is set in a single crystal manufacturing furnace 8 including a low temperature furnace 6 and a high temperature furnace 7. A heat radiating hole 9 is provided above the high temperature furnace 7 of the single crystal manufacturing furnace 8 for the purpose of promoting heat radiation of the crystal.

After setting the ampoule 1 in the single crystal production furnace 8, the temperature in the furnace is raised, the high temperature furnace 7 is set at about 1238 ° C., the low temperature furnace 6 is set at about 600 ° C., and Ga 2 and As 5 are reacted. , GaAs is synthesized. After the synthesis of GaAs, the high-temperature furnace 7 is set so as to form a temperature distribution curve 10 having a constant temperature gradient (see FIG. 3B). By gradually raising the temperature of the high-temperature furnace 7 while maintaining this temperature distribution, Ga
The As is melted and seeded. After seeding, the temperature of the high-temperature furnace 7 is gradually lowered to grow a seed crystal. To grow a single crystal, it is desirable that the solid-liquid interface shape during seed crystal growth be flat or convex toward the melt side in order to prevent the propagation of dislocations. In order to achieve such an interface shape, it is necessary to dissipate more heat to the seed crystal than to the side and bottom of the crystal.

On the other hand, in the GaAs single crystal manufacturing method by the boat method, the seed crystal to be used is selectively used depending on the type of crystal conventionally manufactured from the viewpoint of preventing impurity contamination. For example, the undoped or Si-doped seed is used for the Si-doped crystal. The crystal is undoped or Z for Zn-doped
An n-doped seed crystal is used. The carrier concentration and the like other than the above are generally used without any particular definition.

[0007]

However, there is a problem that the solid-liquid interface shape tends to be concave near the boat shoulder, which is the initial growth stage, and the resulting crystal is polycrystalline. As a cause of this, in the growth stage at the boat shoulder, the heat dissipation to the crystal side is difficult to dissipate because the crystal solidified portion only has a seed crystal, and the heat dissipation from the crystal, the crystal side surface through the boat and This is because there is much heat radiation to the bottom.

Therefore, as a solution to the polycrystallization, measures were taken to make the temperature gradient of the seed crystal portion steep. However, due to problems such as the ability of the heater and the set temperature at the time of seeding, a concave surface of the interface shape was formed. Until the problem is solved, the temperature gradient cannot be set rapidly and the solution has not been reached. In addition, heat radiation from the crystal solidification part (heat radiation to the seed crystal side) remains the same, and heat radiation from the heat radiation hole is increased, so that heat radiation to the top of the crystal becomes more dominant to the side and bottom of the crystal. In order to improve the shape of the interface at the boat shoulder, the solid-liquid interface beyond the shoulder of the boat is overly sluggish, and the solid-liquid interface and the wafer sampling surface become inconsistent. A new problem has arisen in that the divergence increases and the in-plane characteristics of the wafer vary greatly.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a method for producing a compound semiconductor single crystal with good reproducibility.

[0010]

In order to achieve the above object, a method of manufacturing a compound semiconductor single crystal according to the present invention is a method of manufacturing a compound semiconductor single crystal by a boat method, comprising: A compound semiconductor single crystal is manufactured using a seed crystal having a carrier concentration higher than the carrier concentration.

In addition to the above constitution, in the method for producing a compound semiconductor single crystal of the present invention, it is preferable that the thermal conductivity of the seed crystal is larger than that of the compound semiconductor single crystal.

According to the present invention, by using a seed crystal having a higher carrier concentration than that of an actually manufactured crystal, when the thermal conductivity is compared, the seed crystal can improve the thermal conductivity more than the crystal. (In general, in a metal, electrons in a substance play a role in transmitting heat. Therefore, when the carrier concentration is high, the thermal conductivity tends to be high, and GaAs is also used in this example. No leakage.) For this reason, heat flows from the lower thermal conductivity to the higher thermal conductivity, that is, from the crystal side to the seed crystal side, so that heat radiation from the seed crystal can be promoted. As a result, the solid-liquid interface is prevented from being concave.

[0013]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1A is a view showing an embodiment of a manufacturing apparatus to which the method for manufacturing a compound semiconductor single crystal of the present invention is applied, and FIG. 1B is a view showing the manufacturing method shown in FIG. It is a figure which shows the furnace temperature distribution of an apparatus. The horizontal axis in FIG. 1 (b) indicates the furnace position, and the vertical axis indicates the furnace temperature. The same members as those in the conventional example shown in FIG.

In FIG. 1A, a seed crystal 11 having a carrier concentration higher than the carrier concentration of a compound semiconductor single crystal to be manufactured is provided on a shoulder of a boat 4 made of quartz. The main body of the boat 4 contains Ga (solid) 2. The boat 4 is housed on one side (the right side in the figure) of a quartz ampoule 1 partitioned left and right by a partition wall 12 with a capillary, and As (solid) 5 on the other side (the left side in the figure).
Is housed.

The ampoule 1 is accommodated in a single crystal manufacturing furnace 8 comprising a low-temperature furnace 6 and a high-temperature furnace 7. The ampule 5 is positioned on the low-temperature furnace 6 side, and the boat 4 is positioned on the high-temperature furnace 7 side. doing. The high-temperature furnace 7 has a heat radiating hole 9 formed therein.

When a compound semiconductor single crystal is manufactured using such an apparatus, the thermal conductivity is compared by using a seed crystal 11 having a higher carrier concentration than the crystal actually obtained (crystal obtained in the boat 4). In this case, the heat conductivity of the seed crystal 11 can be better than that of the crystal. Therefore, heat flows from the lower thermal conductivity to the higher thermal conductivity, that is, from the crystal side to the seed crystal 11 side (to the left in the figure), and the heat radiation from the seed crystal 11 can be promoted. As a result, the solid-liquid interface is prevented from being concave.

[0018]

EXAMPLE Using such an apparatus, a prototype was produced by changing the carrier concentration of the seed crystal 11 by boat crystal growth by the GF method. Hereinafter, the details will be described with specific numerical values, but the present invention is not limited thereto.

The temperature distribution in the furnace has a temperature gradient of about 600 ° C. in the low-temperature furnace 6 and a temperature gradient of about 1238 ° C. in the high-temperature furnace 7 as shown by a curve 10 in FIG.

Crystal growth was performed using a φ-inch Si-doped GaAs crystal having a carrier concentration of 2.0 × 10 ¹⁷ (pieces / cm ³ ) at a solidification rate of 0.1. The carrier concentrations of the seed crystals 11a to 11e are as follows: (1) to (5)
As expected.

(1) 2.0 × 10 ¹⁷ (pieces / cm ³ ) (2) 5.0 × 10 ¹⁷ (pieces / cm ³ ) (3) 1.0 × 10 ¹⁸ (pieces / cm ³ ) (4) 2.0 × 10 ¹⁸ (pieces / cm ³ ) (5) 3.0 × 10 ¹⁸ (pieces / cm ³ ) Next, crystal growth using the apparatus shown in FIG. 1 will be described.

In the ampoule 1 shown in FIG.
a, As5 and the seed crystal 11 are charged and vacuum sealed. The vacuum-sealed ampoule 1 is set in a single crystal production furnace 8, and the temperature is raised and the reaction is performed.
Set to eg / cm. After seeding under the temperature distribution conditions, the temperature of the high-temperature furnace 7 is lowered at a rate of 0.1 ° C./hr to perform single crystal growth.

FIGS. 2A and 2B are schematic diagrams of striations (growth fringes) at the shoulder of the boat with seed crystals having different carrier concentrations. FIG. 2A corresponds to the condition (1),
FIG. 2B shows the condition (2), and FIG. 2C shows the condition (3).
(D) corresponds to the condition (4), and FIG. 2 (e) corresponds to the condition (5). 2 (a) and 2 (b), the seed crystals 11a to 11e are shown.
It can be observed that as the difference in carrier concentration between the crystal and the crystals 13a to 13e is widened, the degree of striation is reduced.

As described above, according to the present invention, it is possible to prevent the crystal-solid interface, particularly the solid-liquid interface at the shoulder of the boat, from being concave, to effectively eliminate polycrystallization, and to obtain a single crystal with good reproducibility. Obtainable.

The method for producing a compound semiconductor single crystal of the present invention is applicable to all compound semiconductor single crystals (G
aP, InAs, InP, etc.). Also,
The present invention is also applicable to all compound semiconductor single crystal production (GaP, InAs, InP, etc.) by the HB method, the VB method, and the VGF method.

[0026]

In summary, according to the present invention, the following excellent effects are exhibited.

By producing a compound semiconductor single crystal using a seed crystal having a carrier concentration higher than the carrier concentration of the compound semiconductor single crystal to be produced, heat flows from the crystal side to the seed crystal side. This promotes heat dissipation, prevents the solid-liquid interface from being concave, and provides a crystal with good reproducibility.

[Brief description of the drawings]

FIG. 1A is a diagram showing an embodiment of a manufacturing apparatus to which a method for manufacturing a compound semiconductor single crystal of the present invention is applied,
(B) is a figure which shows the furnace temperature distribution of the manufacturing apparatus shown to (a).

FIGS. 2A and 2B are schematic diagrams of striation of a shoulder portion of a boat with seed crystals having different carrier concentrations.

3A is a conceptual diagram of a manufacturing apparatus to which a conventional method of manufacturing a compound semiconductor single crystal is applied, and FIG. 3B is a diagram showing a furnace temperature distribution of the manufacturing apparatus shown in FIG. .

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 ampoule 2 Ga 4 boat 5 As 6 low-temperature furnace 7 high-temperature furnace 8 single-crystal manufacturing furnace 11 seed crystal

Claims (2)

[Claims] 1. A manufacturing method for manufacturing a compound semiconductor single crystal by a boat method, wherein the compound semiconductor single crystal is manufactured using a seed crystal having a carrier concentration higher than the carrier concentration of the compound semiconductor single crystal to be manufactured. Of producing a compound semiconductor single crystal. 2. The method according to claim 1, wherein the thermal conductivity of the seed crystal is higher than the thermal conductivity of the compound semiconductor single crystal.