JPS5850957B2 - Single crystal growth equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved single crystal growth apparatus for use in pulling single crystals.

Traditionally, the pulling method (Chochra Isk i method)
has been widely used for growing silicon and germanium single crystals as a means suitable for obtaining relatively large-volume single crystals.

In recent years, it has been desired to be further applied to the growth of IV group compound semiconductors.

These include gallium phosphorus (GaP) and gallium arsenide (GaP), whose compositions include elements with high vapor pressure such as phosphorus and arsenic.
This is because an effective technology has been obtained to solve the problem of phosphorus and arsenic dissociating from the melt and changing the composition ratio of the single crystal when pulling GaAs), and the problem of controllability of the pulled crystal diameter.

One possible solution for the former is the melt capsule method, and for the latter, a technique applying the melt capsule method described in JP-A-51-64482 is cited as a solution.

According to this publication, as shown in FIG. 1, a crucible 12 is built in a high-pressure container 11 filled with high-pressure inert gas, and inside this crucible 12 is CaP, which is a melt of a crystal raw material.
A melt 13, a plate member 15 made of silicon nitride having an opening provided above the GaP melt 13 and having a protrusion below the liquid surface, and a boron oxide (capsule material) covering the plate member. B2 os ) melt is provided.

The plate member 15 is completely covered with the B2O3 melt, and therefore the B2O3 melt is located between the GaP and the silicon nitride plate.

In the GaP single crystal pulling apparatus configured in this way, G is
By raising the aP single crystal 16, the crystal diameter changes slowly with respect to temperature fluctuations near the solid-liquid interface, making it possible to easily control the crystal diameter.

However, the inventors have discovered that there are still problems that need to be solved even with such a device.

One of these is that the crystallinity of the grown crystal is extremely poor and non-uniform, and furthermore, the single crystallinity of the ingot is low.

More specifically, when we assembled the apparatus described in JP-A-51-64482 and pulled a GaP single crystal with a diameter of approximately 45 mm, we found that the number of dislocation densities was large, and the distribution of the cross-section of the ingot was shown in curve a in Figure 2. The distribution showed a V-shaped distribution, which worsened as it approached the periphery of the ingot and was extremely non-uniform.

For example, if a wafer is cut from such an ingot and used as the basis for a light emitting device, the device characteristics will deteriorate and large variations will occur from chip to chip.

This leads to a similar situation regarding the problem of the single crystallization rate.

Therefore, the present inventors investigated various causes of such results and found that the GaP melt and the plate member were not sufficiently isolated near the solid-liquid interface during single crystal pulling, resulting in a so-called wet state. considered to be sufficient.

Therefore, it is thought that the above defects are caused by mechanical strain being introduced from the plate-like member near the solid-liquid interface, impurities in the plate-like member, or temperature variations. It will be done.

That is, in the above-mentioned Japanese Unexamined Patent Publication No. 51-64482, silicon nitride, silicon oxide, silicon nitride, silicon carbide, etc. are used as the plate-like member, and further studies on such compositions are required. It became necessary to add.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to obtain a stable and high-quality single crystal by configuring the plate-like member to be sufficiently isolated from the melt of the crystal raw material at least near the solid-liquid interface. The purpose of this invention is to provide a single crystal growth apparatus that can perform the following steps.

That is, the device of the present invention is a device in which a plate-like member having an opening is provided, an encapsulant is provided to cover at least the plate-like member, and crystals are pulled up through the opening of the plate-like member. A single crystal growth apparatus characterized in that the shaped member is made of a composition containing at least one of boron nitride, silicon nitride, and aluminum nitride, and at least one of silicon oxide, magnesium oxide, boron phosphate, silicon phosphate, and aluminum phosphate. It is.

The apparatus of the present invention will be described in detail below based on embodiments and with reference to the drawings.

Example 1 Boron nitride (BN) powder and silicon oxide (SiO2) were prepared in advance.
The powder was thermoformed with some organic material as a binder so that the effective specific gravity was between 1.9 and 4.2 and S102 was contained at 8% by weight. A plate-like member 21 having a circular opening 21a having a diameter of, for example, about 47 mm as shown in FIG.

On the other hand, as shown in FIG. 4, a quartz crucible 23 is housed in a high-pressure container 22 filled with inert gas, and a carbon susceptor 24 and a heater 25 are arranged to surround this crucible. .

In addition, solid gallium phosphorus (GaP) as a crystal raw material and solid boron oxide (B203) as an encapsulant are placed in the crucible 23, and the forest member 21 is placed on top of it. The whole thing was heated to over 1000 degrees.

When the temperature rises to over 100 degrees, the solid B2O3 and GaP melt to form a GaP melt 26, a plate member 21, and a B2O3 melt 27 from the bottom as shown in FIG.

This is because the specific gravity of the plate member 21 is set between 1.9 and 4.2, so the specific gravity of the B2O3 melt is 1.8, and the GaP
This is because it has an intermediate value compared to the specific gravity of the melt, which is 4.3.

Further, the B2O3 melt 27 becomes wet with the plate-like member 21, so that the surface of the plate-like member 21 is completely covered.

A rotating shaft 28 is held vertically to the surface of the melt.
A GaP seed crystal 29 that would yield a crystal growth plane with a desired crystal orientation, such as (111), was attached to the tip and a predetermined pulling operation was performed.

That is, the seed crystal is lowered into the opening of the plate-shaped member 21 and brought into contact with the GaP melt 26, and then pulled vertically upward while rotating the rotating shaft 28 at a very slow speed.
9 continuous GaP single crystals 30 were grown.

The crystal pulling operation was carried out while maintaining an appropriate distance from the plate member 21 by controlling the pulling speed and the thermal conditions near the solid-liquid interface in the melt.

G of approximately 45mrfLφ raised in this way
The aP ingot was cut into disks with a thickness of 350 μm and etched, and etch pits on the surface were observed.

As shown in the curve in Figure 2, the dislocation density is almost uniform near the periphery, and the value is less than 5 x 10' pieces/d, which is a good result, and furthermore, no polycrystalline formation is observed. Met.

This is partly because the B2O3 melt 27 and the plate member 21 are in a good wet state, and the solid-liquid interface 27a can reduce the influence of the plate member 21 even during operation. It is believed that there is.

Example 2 Nitrogen silicon (813N4) powder and magnesium oxide (Mg
O) Powder is thermoformed with a binder so that its specific gravity is between 1.9 and 4.2 and MgO is contained at 1% by weight to form a plate-like member 3 as shown in FIGS. 5a and 5b.
1 was created.

The plate-like member 31 in this embodiment has an opening 31a in the center having an inclined cross section and protruding downward by about 15 mm, and the diameter of the lower side of this opening 31a is 42 mm and the diameter of the upper side is 52 mm.
It was formed to have a diameter of φ.

The crystal pulling operation was carried out in the same manner as in Example 1.

The GaP single crystal obtained in this manner was able to achieve uniformly low dislocation density and single crystallization at a high yield, as in Example 1.

Even with such a shape, the plate-like member 31 is a B2O3 melt 27
It is in a good moist state, and the opening is sloped and G
By protruding into the aP melt 26, the crystal diameter can be easily controlled.

Example 3 A plate having the same shape as in Example 1 was prepared by combining aluminum nitride (AAN) powder and aluminum phosphate powder with a binder such that the specific gravity was 1.9 to 4.2 and aluminum phosphate was contained in an amount of 5.0% by weight. A shaped member was created and a predetermined pulling operation was performed.

As a result, we were able to obtain uniform single crystals with low dislocation density in high yield.

Among the other compositions of the plate member of Example 2, Si3N
If 4 is replaced with BN or A7N, or Mg
Even when O was replaced with Si02, boron phosphate, silicon phosphate, or aluminum phosphate, the structure inside the heated crucible was the same as in Example 2, and the same effects were obtained.

In more detail, the single crystallization rate, dislocation density, and durability of the plate-like member were examined by varying the composition of the plate-like member.

Figure 6 shows the single crystallization rate, and shows the single crystallization rate of 10 GaP
The ratio was calculated based on the number of ingots, all of which could be obtained as single crystals.

When the additive component is in the range of 1.0 to 10 weight percent, a single crystallization rate of 80% or more is exhibited regardless of the additive component used, especially when the main component is Si3N4. A, /, N, B
Figure 7 shows the ratio of dislocation density regions of 1 x 105 dislocations/d or less in the wafer cut out from the ingot. .0 to 10% by weight, accounting for more than 80% of the ratio of B N , A
, tN, and S t 3N4.

Figure 8 shows that the inner diameter of the lower side of the plate member used in Example 2 is 42 mm.
The durability is shown by the number of times the component is eluted from mmφ and reaches 45mmφ, and if any added component is 1.0 to 10% by weight, it is A.
tN, Si3N4. It was good in order of BN.

As detailed above, S i02゜M contained in the forest member
gO1 Additional components such as boron phosphate, silicon phosphate, and aluminum phosphate are preferably 1 to 10% by weight.

This is thought to be because if it is too small, wetting with the B2O3 melt will be reduced, while if it is too large, the reaction with B2O3 will be promoted and the B2O3 melt and GaP melt will be contaminated.

Moreover, the reason why no difference was observed even when the added components were changed is considered to be because the amount added was small.

The main components are BN, 5i3N4. Two or more types of AtN may be used.

For example, an ingot containing BN and Si3N4 as main components and having a moderately good ratio of single crystallization and dislocation density can be obtained.

Further, the specific gravity of the plate-shaped member may not be set to 1.9 to 4.2, and the buoyancy of the plate-shaped member may be adjusted by an external force such as a floating ring or a spring.

Further, as described above, the composition of the plate-like member may include some binder such as magnesia (MgO) or silica (S102).

The crystal material may be not only GaP but also other IV group compound semiconductors, or may be used when doping Si or Ge melt with impurities with high vapor pressure such as phosphorus or arsenic to form a single crystal. .

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a conventional device, Fig. 2 is a diagram showing the dislocation density of ingots obtained by the conventional device and the device of the present invention, and Fig. 3 a and b are plates of an embodiment of the device of the present invention. 4 is a sectional view of a single crystal growth apparatus for explaining one embodiment of the present invention, and FIGS. 5a and 5b are plan and sectional views of a plate-shaped member of another embodiment of the apparatus of the present invention. Plan and cross-sectional views of
Figure 6 shows the single crystallization rate when the material of the plate member of the device of the present invention is changed, and Figure 7 shows the growing single crystal dislocation density when the material of the plate member of the device of the present invention is changed. The figure shown in FIG. 8 is a curve diagram in which the number of service life of the plate-like member of the device of the present invention was investigated when the material of the plate-like member was changed. In Fig. 4, 21... plate-like member, 22...
...High pressure container, 23... Crucible, 24...
... Susceptor, 25 ... Heater, 26.
...GaP melt, 27 ... B2O3 melt, 28 ... Rotating shaft, 29 ... Seed crystal,
30...GaP single crystal.

Claims (1)

[Scope of Claims] 1. A single crystal growth apparatus in which a plate member having an opening is provided above the melt, an encapsulant is provided to cover the plate member, and a single crystal is pulled through the opening of the plate member. The plate member has a composition containing at least one of boron nitride, silicon nitride, and aluminum nitride, and 1 to 10 weight percent of one or more of silicon oxide, magnesium oxide, boron phosphate, silicon phosphate, and aluminum phosphate. A single-crystal growth device characterized in that it is made of a material. 2. The single crystal growth apparatus according to claim 1, wherein the specific gravity of the plate member is set between the specific gravity of the melt and the specific gravity of the capsule material.