JPS5938199B2 - Compound semiconductor crystal growth equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compound semiconductor crystal growth apparatus used in a compound semiconductor solution growth method.

The conventional device of this type is r3 Crystais Gro.
wtjProperties Association and Application
ions III-VSemi-conduct
ors * Springer-Verlag 1
980J is introduced in detail.

Figure 1 shows a 5SD (Synthesis * 5olute s D), which is representative of this type of device.
This is a device used for the 1 ffusion method.

As is clear from FIG. 1, this conventional apparatus basically consists of a high temperature furnace 1 and a low temperature furnace 2, which are spaced apart from each other.

A soaking tube 3 is provided through the high-temperature furnace 1 and the low-temperature furnace 2. A semiconductor compound raw material 4 is stored in the bottom of the soaking tube 3, and a crucible 6 containing a raw material solution 5 is placed at the high temperature. A synthesis ampoule 7 housed in the furnace 1 section is provided.

This configuration has the following drawbacks.

Most of these drawbacks are due to temperature distribution.

That is, as the crystals 8 grow on the bottom of the crucible 6 containing the solution 5, the solid-liquid interface moves upward.

At this time, since the crucible 6 is in a temperature gradient, the solid-liquid interface moves to a higher temperature from the initial temperature T1 to T2 (>T1) and to a lower temperature gradient region.

Changes in solid-liquid interface temperature impair crystal composition uniformity, and a decrease in temperature gradient leads to a decrease in growth rate.

Furthermore, since the temperature gradient at the lower end of the high temperature furnace 1 can only be adjusted by the gap between the high temperature furnace 1 and the low temperature furnace 2, there are problems in that it is difficult to obtain a large temperature gradient and it is easily influenced by the ambient temperature.

In particular, fluctuations in the temperature at the solid-liquid interface due to a decrease in the temperature gradient and fluctuations in the ambient temperature generate a large number of crystal nuclei at the solid-liquid interface, causing the growth of small polycrystalline aggregates as shown in FIG.

In such polycrystalline aggregates, impurities are trapped at grain boundaries,
This had the disadvantage of reducing purity (see Figure 1).

As we have seen above, the SS in which the synthetic ampoule 7 is fixed
Device D had drawbacks such as non-uniform crystal composition, reduced growth rate, and reduced purity due to polycrystallization.

To improve these drawbacks, synthetic ampoule 1
Some devices have a pull-down synthesizer that pulls down the crystal at approximately the growth rate of the crystal 8.

As shown in FIG. 3, the cross-sectional view of the crystal grown by this device is an aggregate of spindle-shaped crystals extending in the pulling direction.

However, in this type of pull-down synthesis apparatus, it is difficult to control the irregular generation of crystal nuclei at the solid-liquid interface, and it has not been possible to obtain large-sized single crystals.
H-Iwasaki's J-Cryst 5Gro
-Wth, 46, 289 (1979)).

The cause of this is the non-uniformity of temperature distribution at the solid-liquid interface.
One example is the fluctuation in temperature here.

FIG. 4 shows a device that makes it possible to use seed crystals, which is another representative of this type of device.

In the figure, 9 is a seed crystal, 10 is a graphite cylinder,
11 is a high frequency coil.

This configuration has the following drawbacks.

One is the liquid dissolution of the seed crystal 9.

This phenomenon occurs when the seed crystal 9 and the graphite cylinder 10 are not in uniform contact or when the solution 5 on the seed crystal 9 is unsaturated.

Another disadvantage is the reduction in purity of the grown crystal 8 due to the use of the graphite cylinder 10.

This is caused by impurities volatilized from graphite exposed to high temperatures and impurity contamination due to contact between the solution and graphite.

In order to eliminate these drawbacks, the present invention provides a heater dedicated to setting a temperature gradient at the lower end of the high temperature, and further provides a mechanism for pulling down the synthesis ampoule while rotating, thereby stabilizing the crystal growth temperature at a constant level and maintaining the temperature at the solid-liquid interface. This makes it possible to obtain high-purity, large-sized single crystals without the use of seed crystals.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 5 shows an embodiment of the present invention, in which 1 is a high-temperature furnace, 2 is a low-temperature furnace, 3 is a soaking tube, 4 is a group V element raw material, 5 is a raw material solution, 6
1 is a melting pot, 7 is a synthesis ampoule, 8 is a growing crystal, 12 is a heater dedicated for setting a temperature gradient, 13 is a heat shield plate, 14 is a hanging rod, and 15 is a rotational pull-down mechanism.

As is clear from FIG. 5, one embodiment of the compound semiconductor crystal growth apparatus according to the present invention has a high temperature furnace 1 and a low temperature furnace 2, and these high temperature furnace 1 and low temperature furnace 2 are spaced apart from each other. A heat soaking tube 3 is inserted throughout the interior thereof.

The soaking tube 3 stores the V group element 4 at the bottom, and further contains the high temperature furnace 1.
A crucible 6 containing a raw material solution 5 is provided near a portion corresponding to the bottom.

Further, a dedicated heater 12 for setting a temperature gradient is provided at the lower end of the high temperature furnace 1 to set and control a temperature gradient so that a large temperature gradient can be obtained. A heat shield plate 13 is provided to prevent the heat shield 12 from being affected by the surroundings.

In addition, the synthetic ampoule 7 is connected to a hanging rod 14, which is connected to a rotating and lowering mechanism 15, allowing the synthetic ampoule 1 to be moved up and down.

To operate this, follow the temperature-time characteristic curve shown in FIG.

First step: The ampoule 1 is set at a position such that the lower end of the crucible 6 is at To, and the temperature of the furnace 1 is raised.

After reaching the set temperature, the ampoule 7 is kept at the initial ampoule setting position while being rotated for the time necessary for crystal 8 to grow at the bottom of the crucible 6.

Second stage: Reduction is performed at a growth rate determined by the temperature and temperature gradient at the lower end of the crucible 6.

The pulling time is determined by the total amount of crystals. Ru.

After cooling is completed, the temperature decreases to room temperature at a constant rate. I'll get back to it.

Specifically, in the case of InP crystal, ln=200g.

Using P = 65 g, To = 950 ° C, the temperature gradient there was set to 50 ° C, / cm, 4 rpm and 10 wn.
/day, it was possible to obtain a single crystal with a diameter of 35 mm and a length of 70 mm.

In addition, in this crystal, since there is no capture of impurities at the grain boundaries,
As shown in FIG. 7, the carrier concentration and uniformity of mobility at the lower and upper ends of the crucible were significantly improved.

In FIG. 1, curves a and b indicate crystals produced according to the present invention;
Curves c and d show the electrical characteristics of a crystal produced by a conventional SSD device.

As explained above, by providing a heater dedicated to setting the temperature gradient and pulling down the synthesis ampoule while rotating, (a) the temperature gradient can be increased, thereby increasing the growth rate.

(0) Due to stable temperature gradient and rotation of synthesis ampoule,
The uniformity of the temperature distribution at the solid-liquid interface increases, making single crystal growth easier.

e→ With a pulling rate equal to the growth rate, the solid-liquid interface temperature can be kept constant, thereby promoting crystal composition uniformity and single crystal growth.

(2) It is possible to easily obtain large single crystals without using seed crystals, and ((e) High purity is achieved because there is no possibility of introducing contaminants such as graphite into the ampoule. This has the advantage of allowing crystal growth.

As is clear from the above, the present invention can be widely applied as a single crystal growth apparatus using the solution growth method, and in addition to InP, GaP s G aA s *G
It is also possible to grow single crystals such as aSb and InAs5InSb.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a conventional SSD device, Fig. 2 is a cross-sectional view of a crystal produced by an SSD device, Fig. 3 is a cross-sectional view of a crystal produced by a device having a pull-down device, and Fig. 4 is a sectional view of a manufacturing device using seed crystals. 5 is a sectional view of an embodiment of the device according to the present invention, FIG. 6 is a temperature-time characteristic curve when using the device according to the present invention, and FIG. 7 is a composite of the SSD device and the device according to the present invention. This is a comparison of the electrical properties of the synthesized crystals. 1... High temperature furnace, 2... Low temperature furnace, 3... Soaking tube, 4
... Raw material for semiconductor, 5... Raw material solution, 6... Crucible, 1... Synthesis ampoule, 8... Growing crystal, 9...
・Seed crystal, 10... Craphite cylinder, 11
... High frequency coil, 12 ... Heater for temperature gradient setting, 13 ... Heat shielding plate, 14 ... Hanging rod, 15
...Rotation/pull down mechanism.

Claims (1)

[Claims] 1. In a compound semiconductor growth apparatus equipped with a synthesis ampoule capable of storing raw materials and raw material solutions for compound semiconductor production inside a vertical two-heating furnace having a high temperature section above and a low temperature section below, A compound semiconductor crystal growth apparatus characterized by having a heater dedicated to setting a gradient, and a mechanism for pulling down a synthesis ampoule while rotating it.