JPH085745B2 - Compound semiconductor lifting device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulling apparatus for producing a compound semiconductor single crystal such as GaAs and, more particularly, to an improvement in preventing impurities from entering from a sealing material interposed on a dividing surface of an airtight container. .

[0002]

2. Description of the Related Art When a compound semiconductor single crystal such as GaAs containing a volatile component and easily decomposed is manufactured by the CZ method, the crucible is placed in an airtight container filled with a high-pressure inert gas, and the crucible Molten glass (B ₂ O ₃ ) on the molten metal
The so-called LEC method of floating a single crystal and pulling a single crystal while preventing evaporation of volatile components from the molten metal has been widely used.

However, in this LEC method, it is difficult to realize a gradual temperature gradient at the solidification interface of the single crystal, and it is impossible to control the composition of the molten metal after the start of the work, resulting in dislocations due to thermal strain or non-stoichiometry. There was a problem of high density.

Therefore, recently, instead of covering the molten metal with molten B ₂ O ₃ , the volatile element (in this case A
A method was proposed in which the above problem was solved by filling the steam of s) and controlling the steam pressure.

An example of a device therefor is shown in FIG. This device is described in Japanese Patent Application Laid-Open No. 60-255692, and reference numerals 1 and 2 in the drawing denote a container upper part and a container lower part which form an airtight container 3, and are fixed to a lower shaft 4 inside these. The crucible 5 is arranged, and the container 6 is heated to about 650 to 1300 ° C. with the heater 6 arranged outside. Further, a vapor pressure control furnace 7 is provided in the upper part 1 of the vessel, and by controlling the temperature of the inner wall of the control furnace 7, the vapor pressure of the volatile components condensed in this part is adjusted and the single crystal is pulled from the molten metal Y. It has become. 8 is an optical window,
Reference numeral 9 is a rotary seal.

As shown in FIG. 9, a convex portion 1A is formed on the lower end of the container upper portion 1 over the entire circumference, and a concave groove 2A into which the convex portion 1A is fitted is formed on the upper end of the container lower portion 2. Direction, and the sealing material 10 such as molten B ₂ O ₃ is put therein. Further, the lower part of the container is a biasing means 1 such as a spring.
1, the convex portion 1A and the concave portion 2A are in pressure contact with each other.

In the above publication, as an example of using a solid sealing material, as shown in FIG. 10, a solid sealing material 12 such as a graphite sheet is sandwiched between the container upper part 1 and the container lower part 2 and pressed. Is also described.

[0008]

However, when B ₂ O ₃ is used as the sealing material as shown in FIG. 9, the sealing material 10 is solidified after being pulled up, and the container upper part 1 and the container lower part 2
There is a drawback that the container 3 cannot be opened at room temperature by bonding and. Further, when the solid sealing material 12 such as a graphite sheet is used as shown in FIG. 10, although the openability of the container 3 is excellent, the produced single crystal is contaminated by impurities and is usable. There was a problem that a single crystal could not be obtained.

Therefore, the present inventors have conducted a detailed examination on the presence or absence of generation of impurities in a graphite sheet having excellent characteristics as a sealing material by a precise measurement. The impurity contamination is trace amount of impurities ( It was found that the cause was the invasion of S etc.).

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a solid sealing material such as a graphite sheet is provided over the entire circumference at the joint between container members constituting an airtight container. This solid while interposing in a compressed state
On the inner side of the sealing material, connect the ends of the plurality of container members to each other.
Impurity diffusion prevention part with a gap between these ends in close proximity
Formed, and the gap between the voids is 0.5 mm or less, and
The shortest length of the void from the inside of the container to the side of the solid sealing material is 0.5 mm or more.

[0011]

With the above structure, the diffusion rate of impurities generated from the solid sealing material is extremely reduced, and contamination of the single crystal due to the intrusion of impurities is prevented.

[0012]

1 and 2 show an embodiment of the compound semiconductor pulling apparatus according to the present invention. The same parts as those in FIGS. 8 and 9 are designated by the same reference numerals and the description thereof will be omitted.

In this device, a ring-shaped thin solid sealing material 22 is placed on the outer peripheral side of the horizontal upper end surface of the container lower part 21, and a rectangular cross section that projects vertically upward is provided on the other inner peripheral side. 21A is formed over the entire circumference. Further, the sealing material 2 is provided on the lower end surface of the container upper portion 20.
A minute sealing convex portion 20B having an arcuate or edge-shaped cross section is formed over the entire circumference at a position corresponding to the central portion of 2, and the step portion 21A of the lower portion 21 of the container is a recess into which the concave portion 21A fits without a gap. The groove 20A is formed, and the step portion 21 is formed.
An impurity diffusion preventing portion is constituted by A and the groove 20A.

As the material of the upper part 20 and the lower part 21 of the container, ceramics such as silicon carbide, silicon nitride, sialon, boron nitride, aluminum nitride, alumina, zirconia, titanium carbide, titanium nitride, molybdenum, molybdenum alloy, tungsten are used. , Tungsten alloy, niobium,
A refractory metal material such as a niobium alloy, a refractory metal material, or a carbon material coated with the above ceramics is preferable.

The solid sealing material 22 has a thickness of 0.
A graphite sheet of about 2 to 1.0 mm is suitable. If the thickness is less than 0.2 mm, sufficient sealing performance cannot be obtained. On the other hand, if the thickness is greater than 1.0 mm, it is difficult to accurately set the void thickness of each part due to a change in the thickness of the sealing material 22, and the sealing performance becomes poor. descend. The graphite sheet is a commercially available product obtained by subjecting graphite to foaming treatment and press sintering, and it is desirable that the content of impurities is 500 ppm or less.

The upper part 20 and the lower part 2 of the container
In the case of No. 1, the lower part 21 of the container is raised at a constant pressure by the urging means 9 and brought into pressure contact with each other, and the pulling temperature (1300 ° C)
With the temperature raised to 0, the sealing projection 20B presses the sealing material 22 to obtain perfect airtightness, and the step 21
At least one of the gaps C1, C2, C3 between A and the groove 20A is 0.5 mm or less, and
The shortest length from the inner side of the container to the sealing material 22 side (L
1, L2, L3) is set to 0.5 mm or more.

AllThe space between the voids C1, C2, C3 is
0.5 mm or more, orOf the voidShortest length L1, L2
When L3 is less than 0.5 mm, the above conditions are
Impurities from the sealing material 22 as compared with the case where it is filled
Intrusion increases rapidly. In addition,The narrower the gap, the better,processing
Although accuracy is required, the inner surfaces of the stepped portion 21A and the concave groove 20A are
Contact is desirable. Suitable pressure for the sealing material 22
While applying forceThe gap C2Over the entire circumference of the joint
In order to set 0 (that is, the state of being pressed), the convex portion
Reduce the height of 20B to a value that is less than the thickness of the sealing material.
Good to do. Processing accuracy is not sufficient,Voids C1, C2
C3 spacingIs not constant in the circumferential direction of the joint
HasMaximum gap spacingandShortest lengthSatisfies the above conditions
Should be set as

According to the compound semiconductor pulling apparatus having the above-described structure, the sealing material 22 keeps the container completely airtight, and the step portion 21A and the concave groove 20A provided inside the sealing material 22 are combined with each other. Since the voids are narrow, the diffusion rate of the impurity atoms can be remarkably reduced, the invasion of impurities into the container can be prevented, and a high-purity and homogeneous single crystal can be manufactured.

Further, since a graphite sheet is used as the sealing material 22, the container upper part 2 is kept in the cooled state.
0 and the lower portion 21 are not adhered to each other, so that the container can be opened and closed easily. The present invention is not limited to the above-described embodiment, and modifications such as those shown in FIGS. 3 to 7 are also possible.

In FIG. 3, the convex step portion 30A formed on the inner peripheral side of the lower end surface of the container upper portion 30 and the upper end surface of the container lower portion 31 constitute an impurity diffusion preventing portion. 31C is a step portion for positioning the sealing material 22. This example is suitable when the wall thickness of the container is relatively large, and has an advantage that the cross-sectional shape is simpler and the manufacturing is easier than that of the above-described embodiment.

Since the sealing convex portion 30B has an edge-shaped cross section and the edge height is lower than the height of the convex step portion 30A, the gap C4 is spaced from the upper portion 30 of the container when the processing accuracy of the apparatus is good. It can be made extremely small by pressing the lower part 31 of the container.

Next, FIG. 4 is similar to that of FIG.
Complementary inclined surfaces 40A, 41A are formed on the inner sides of the container upper portion 40 and the lower portion 41, and these inclined surfaces 40A, 41A
The gap between 41A is set in the above range. In this example, there are advantages that the inclined surfaces 40A and 41A prevent impurities from being diffused and that the upper container 40 and the lower container 41 can be aligned at the same time.

Next, in FIG. 5, a pair of concave grooves 50A and convex portions 51A having complementary shapes are formed in the upper part 50 and the lower part 51 of the container, respectively, to further enhance the effect of preventing impurity diffusion. Further, as shown in FIG. 6, a convex portion 60A and a concave groove 61A may be formed on the container upper portion 60, or narrow gaps 72 on both sides of the sealing material 22 as shown in FIG.
May be provided.

[0024]

[Experimental Example] Next, the effect of the present invention will be demonstrated with reference to an experimental example. (Experimental example) In the device shown in FIGS.
A ppm graphite sheet was set as a sealant. In this state, the gap between the impurity diffusion preventing portions is about 0.
It was 2 mm and its shortest length was about 5 mm. Then, in the crucible, Ga: 964 g (purity 6N) and As: 108.
After melting 4g (purity 6N), while controlling the As vapor pressure in the airtight container, diameter: 55mm, weight: 800g of G
The aAs single crystal was pulled up. This single crystal had a carrier concentration of 4 × 10 ⁷ cm ⁻³ , a resistivity of 2 × 10 ⁷ Ωcm and a sulfur impurity concentration of less than 5 × 10 ¹⁴ cm ⁻³ .

(Comparative Example) The same graphite sheet as that described above was set in a conventional apparatus having a structure of the airtight container having the structure shown in FIGS. 8 and 10. Size GaAs single crystals were produced. This single crystal had a carrier concentration of 2 × 10 ¹⁵ cm ⁻³ and a resistivity of 5.
5 × 10 ^-1 Ωcm and sulfur impurity concentration 2 × 10 ¹⁵ cm ^-3
Became. As described above, in the experimental example in which the impurity diffusion preventing portion was provided on the inner side of the graphite sheet, a high-purity and semi-insulating single crystal that could be used for manufacturing a semiconductor element was obtained.

[0026]

The compound semiconductor pulling apparatus of the present invention is
The solid sealing material of the graphite sheet or the like is interposed in pressed state over the entire circumference at the junction of the container members together, the solid sea
The ends of the container members close to each other on the inner side of the lumber
To form an impurity diffusion prevention part with a gap between these ends
However, the gap between the voids should be 0.5 mm or less, and
Since the minimum length of the gap from the inside of the container to the side of the solid sealing material is set to 0.5 mm or more, the diffusion rate of the atoms of impurities generated from the solid sealing material is extremely reduced by the impurity diffusion preventing portion, Impurities can be prevented from entering the inside, and a highly pure and homogeneous single crystal can be manufactured.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an example of a compound semiconductor pulling apparatus according to the present invention.

FIG. 2 is a vertical cross-sectional view showing a container joint portion of the same device.

FIG. 3 is a vertical cross-sectional view of a container joining portion showing another embodiment of the present invention.

FIG. 4 is a vertical cross-sectional view of a container joining portion showing another embodiment of the present invention.

FIG. 5 is a vertical cross-sectional view of a container joining portion showing another embodiment of the present invention.

FIG. 6 is a vertical cross-sectional view of a container joining portion showing another embodiment of the present invention.

FIG. 7 is a vertical cross-sectional view of a container joining portion showing another embodiment of the present invention.

FIG. 8 is a vertical sectional view showing a conventional compound semiconductor pulling apparatus.

FIG. 9 is a vertical cross-sectional view of a container joint portion of the device.

FIG. 10 is a vertical cross-sectional view of a container joint portion of the same device.

[Explanation of reference numerals] 20,30,40,50,60,70 Upper part of container (container member) 21,31,41,51,61,71 Lower part of container (container member) 22 Graphite sheet (solid sealing material) 20A ・ 21A , 30A, 31A, 40A, 41A, 50A
51A, 60A, 61A, 72 Impurity diffusion prevention part 20B, 30B, 40B, 50B, 60B, 70B Sealing convex part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Sasa 1-297 Kitabukuro-cho, Omiya-shi, Saitama 1-297, Compound Semiconductor Center, Mitsubishi Materials Corporation (56) References JP-A-60-255692 (JP, A)

Claims (2)

[Claims] 1. A crucible for holding a melt of a compound semiconductor is disposed inside an airtight container composed of a plurality of container members,
In a compound semiconductor pulling apparatus for pulling a single crystal from the molten metal in the crucible, a solid sealing material is interposed in a pressed state over the entire circumference at the joint portion of the container member, and the inside of the solid sealing material is
On the side, the end portions of the plurality of container members are brought close to each other.
An impurity diffusion prevention part with a gap between the ends is formed to
The gap is 0.5 mm or less, and the shortest length from the inner side of the container to the solid sealing material side is 0.5 mm.
A compound semiconductor pulling apparatus characterized by the above. 2. The compound semiconductor pulling apparatus according to claim 1, wherein the sealing material is a graphite sheet.