JPH0223519B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Application of the Invention) The present invention provides a method for growing a single crystal, which is suitable for use in pulling a single crystal of - group compound semiconductors, particularly GaAs, by the Czyochralski method. Regarding.

(Prior Art) GaAs single crystals have higher electron mobility than Si single crystals when compared at the same level of dimensional accuracy, so demand for them as electronic materials is increasing. The horizontal Bridgeman method is well known as a method for obtaining GaAs single crystals, but there are problems such as impurity contamination from quartz boats and quartz sealed tubes, and the cross-sectional shape of the grown crystals is not circular. Therefore, many attempts have been made recently to cultivate this species using the Czyochralski method.

When using the Czyochralski method, it is possible to obtain a single crystal with higher purity than when using the horizontal Bridziman method, but there is a problem in terms of crystal integrity, and in order to obtain a crystal with a lower dislocation density, Various research and development efforts are ongoing day and night.
It is well known that when this dislocation exists, the electrical and optical properties of semiconductor devices using this material deteriorate or exhibit abnormalities. Although such dislocations may occur during the device manufacturing process, the majority of dislocations already exist in the GaAs single crystal that serves as the substrate. The dislocations that exist in this substrate are mainly caused by thermal strain during the production of the single crystal, but this thermal strain is caused by inert gas that occurs inside the crystal, for example when a high-pressure inert gas atmosphere is placed inside the furnace. Although the cause may be a sharp temperature gradient caused by gas convection, the main cause is that the temperature distribution at the solid-solution interface becomes uneven due to thermal convection occurring in the raw material melt. It is said that Therefore, in order to prevent this heat convection,
A technique has been developed in which a thermal convection prevention plate having a diameter slightly larger than the pulled single crystal is floated below the surface of the raw material melt during single crystal pulling. Although this technology is particularly effective against heat convection from the center to the outside that occurs in the raw material melt, it is not necessarily effective in preventing heat convection from the outside to the center. The drawback was that it was not available.

On the other hand, larger than the diameter of the pulled single crystal,
A convection prevention plate slightly smaller than the inner diameter of the crucible is floated by buoyancy below the surface of the raw material melt, and the raw material melt is poured into the pores provided in the convection prevention plate, or between the outer periphery of the convection prevention plate and the inner periphery of the crucible. There is a technique to guide the raw material melt above the convection prevention plate through the gap between the convection plate, but if the raw material melt is viscous, the raw material melt does not penetrate properly through the pores and gaps, and it takes time to pull it up. Another problem was that if the single crystal was allowed to flow, there would be a shortage of raw material melt in the area from which the single crystal was pulled.

(Technical Problem) Therefore, in this invention, it is possible to completely prevent the thermal convection of the raw material melt from affecting the single crystal pulling portion, that is, the solid solution interface, and also to prevent the outer periphery of the partition plate and the crucible from The technical problem is to ensure that the raw material melt is smoothly fed into the solid solution interface in just the right amount and in excess through the gap 1 provided between the inner wall and the inner wall.

(Technical Means) In order to achieve the above-mentioned technical problem, the present invention aims to create a furnace under a high-pressure gas atmosphere when pulling a single crystal from a raw material melt contained in a crucible by a liquid capsule method. , a partition plate having an outer diameter slightly smaller than the inner diameter of the crucible and having at least one or more liquid cutting blades on the outer periphery is floated at a predetermined position below the surface of the raw material melt so as to be movable up and down. While the crucible is being rotated throughout the crystal pulling process, the raw material melt below the partition plate is guided to the solid solution interface on the top surface of the partition plate through liquid cutting blades, and furthermore, a single crystal is formed between the partition plate and the surface of the raw material melt. The movement is controlled so that a predetermined interval is always maintained throughout the pulling process, and a plurality of heating means are provided coaxially surrounding the crucible, and these heating means are independently controlled.

In the present invention, the movement of the partition plate is controlled while being pressed by a plurality of moving rods that are vertically movably suspended from the upper part of the crucible.

(Function) By configuring this invention as described above, the outer diameter of the partition plate is slightly smaller than the inner diameter of the crucible, so that thermal convection generated in the raw material melt affects the solid solution interface. In addition, even if the distance between the outer periphery of the partition plate and the inner wall of the crucible is small, liquid drainage can be achieved by rotating the crucible. The blades can smoothly guide the raw material melt from the lower surface of the partition plate to the solid solution interface on the upper surface of the partition plate.

Embodiment 1 According to the drawings, in FIG. 1, 1 is, for example, an electric furnace body, and 2 is a heating element 2a, 2 divided into four parts in the axial direction.
The heating means consists of b, 2c, and 2d. A crucible 4 is housed in the center of the heating means 2 and is mounted and fixed on a crucible support rod 3 which is inserted in a confidential manner into the furnace body 1 so as to be rotatable and movable up and down. This crucible 4 consists of an outer crucible 4a made of, for example, graphite and an inner crucible 4b made of quartz, and a raw material melt 5 of, for example, GaAs is stored therein. this
A liquid sealant 6 such as B ₂ O ₃ is floated on the upper surface of the GaAs raw material melt depending on its specific gravity. A single-crystal pulling rod 7 is suspended from the top of the crucible 4, penetrating the furnace body 1 in a confidential manner and configured to rotate and move up and down freely. A single crystal immersed in the raw material melt 5 via the inhibitor 6 is being grown.

At a predetermined position below the upper surface of the raw material melt 5, a partition plate 9 is inserted from above through the furnace body 1 in a confidential manner, and movable rods 11 and 1 made of, for example, (BN) are inserted.
1 and 11, it is floating.

This partition plate 9 is made of, for example, Al ₂ O ₃ (alumina),
It is made of Si ₃ N ₄ (silicon nitride), BN (boron nitride), or PBN (pyrolytic boron nitride), has an outer diameter slightly smaller than the inner crucible 4b, and is oriented upward from its outer periphery. A liquid cutting blade 9a consisting of a plurality of concave and convex portions exhibiting a wavy shape.
A small gap 10 is provided between the outer periphery on which the liquid cutting blades 9a are provided and the inner wall of the inner crucible 4b.
is provided.

Therefore, the heat convection that occurs in the raw material melt 5 below the partition plate 9 during single crystal pulling is not only directed outward from the center (indicated by the dotted line in FIG. 1), but also directed toward the outside. Even if it is directed toward the center (indicated by a solid line in FIG. 1), it is blocked by the partition plate 9 and does not affect the solid-solution interface region above the partition plate 9. Figure 3 shows this partition plate 9.
This figure schematically shows the temperature fluctuation of the GaAs raw material melt in the crucible 4 when using
℃ and the temperature of the heating element 2d is 1200℃,
When this partition plate 9 is present, the temperature gradient can be maintained approximately 30°C higher at the inner bottom of the crucible 4 than when it is not present.
On the other hand, the surface of the raw material melt 5 could be maintained 30°C lower, and the upper surface of the liquid sealant could be maintained even lower by about 40°C.

In particular, the single crystal growth region at the solid solution interface showed a flat and stable temperature distribution with almost no temperature fluctuations, as shown in the enlarged view (view A).

On the other hand, liquid cutting blades 9a provided above the outer circumference of the partition plate 9 guide the raw material melt below the partition plate 9 to the upper surface of the partition plate 9 through a gap 10 formed on the outer circumference as the crucible 4 rotates.
Furthermore, it serves to guide the raw material melt, which has a slightly higher temperature, from the periphery to the central single crystal growth region, so that the raw material melt can always be replenished to the single crystal growth region in just the right amount without any special operational measures. Along with
It has been found that the temperature of the raw material melt decreases slightly while it is being guided to the center, and that disturbance of the temperature distribution in the single crystal growth region can be suppressed as much as possible.

This invention uses a partition plate 9 floating with a slight gap 10 between it and the inner wall of the inner crucible 4b of the crucible 4 containing the raw material melt to generate heat in a region below the partition plate 9. Since convection can have no effect on the solid solution interface region during crystal growth, temperature fluctuations in this solid solution interface region can be kept to an extremely small level. The temperature gradient is also larger than in the conventional case, which means that radiant heat through the liquid sealant 6 is reduced, making it possible to prevent dislocations from occurring from this surface as much as possible.

Furthermore, the present invention provides an arrangement between the outer periphery of the partition plate 9 and the crucible 4.
Even if the gap 10 between the inner wall and the inner wall is small, the raw material melt 12 can be cut by the rotation of the partition plate 9 or the crucible 4 and the uneven liquid cutting blades 9a provided in a wavy manner on the outer circumference of the partition plate 9. Since the lower raw material melt can be smoothly guided to the upper solid solution interface region, the raw material melt can be immersed through the pores provided in the partition plate 9 or the simple gap provided between the partition plate and the inner wall of the crucible. Moreover, it does not take much time to pull up the material, and there is no fear that the raw material melt will run out on the upper surface of the partition plate 9.

The liquid cutting blade 9a may be provided with a through hole instead of the recess, and may be provided in the radial direction of the outer periphery other than in the upper surface direction of the outer periphery of the partition plate. In addition, if a blade is provided on the edge of the uneven part or through-hole, the liquid cutting effect will be further increased, and depending on the shape and structure of the liquid cutting blade, the effect of stirring the raw material melt to promote the growth of single crystals can be produced. It's something that comes.

Example 2 Using the apparatus shown in FIGS. 1 and 2,
GaAs single crystal was pulled.

First, 1.700 g of GaAs polycrystal was placed in a crucible 4 having an inner diameter of 90 m/m and a depth of 100 m/m, and then
300 g of B ₂ O ₃ was added, and a partition plate 9 was placed on top of it. The partition plate 9 was made of BN.

Next, the crucible 4 is placed in the heating means 2, the inside of the furnace body 1 is evacuated, the furnace body 1 is pressurized to 100 atmospheres with an inert gas such as arurgone, and the heating element 2 is heated.
A, 2b, and 2c were heated to 1400°C, and the heating element 2d was heated to 1200°C to melt GaAs. Then, first, B ₂ O ₃ melts, then the GaAs polycrystal melts, and the partition plate 9 has a thickness of about 11 m/m due to its specific gravity.It flows under the B ₂ O ₃ and onto the raw material melt 5. I was in a floating state. This state is observed through a viewing glass (not shown) to confirm melting, and then the moving rod is suspended from above to bury the partition plate 9 in the raw material melt 5, and the partition plate 9 below the surface thereof is immersed in the raw material melt 5. top surface and
It was sunk to a position where the distance between it and the bottom surface of B ₂ O ₃ was approximately 17 m/m.

Next, the single crystal pulling rod 7 is lowered, and the seed crystal 8 attached to the tip thereof is immersed in the raw material melt 5 through B ₂ O ₃ , and it is rotated at about 8 rpm to blend, and the crucible is turned upside down. Same 8rpm in direction
It was rotated at a speed of approximately 15 mm/Hr and pulled in the <111> direction.

During this pulling up, the diaphragm 9 is moved by the moving rod 11,
11, 11, and was kept at a constant distance from the surface of the raw material melt.

The obtained GaAs single crystal has a diameter of 50 m and a length of 250 m.
m/, and the etchibit density is 1.2 x 10 ⁴ cm ^-2 at 10 m/m from the outer periphery and 4.2 x 10 ³ cm at 15 m/m from the outer periphery.
^-2 , and furthermore, it was 6.7×10 ^4-2 cm at 20 m/m from the outer circumference. This shows that the single crystal growth method according to the present invention has extremely fewer defects such as dislocations than those grown by the horizontal Bridgeman method, and it has been found that the single crystal growth method according to the present invention is extremely superior.

In addition, although the above-mentioned embodiment explained the case of pulling a GaAs single crystal, the method of the present invention can be similarly implemented for pulling a single crystal of other compound semiconductors, such as Si, Ge, GaP, IaP, etc. Of course.

In addition, there are those in which the partition plate is held down from above by a moving bar, and those in which the moving bar and the partition plate are fixed together. The former has the advantage that the diaphragm is stored in the crucible in advance, so the view is not obstructed by the mounting position of the viewing glasses. Since it solidifies with the liquid, it has the disadvantage that each manufacturing process is wasted. The latter method requires the separation plate to be pulled up outside the crucible before melting, which has the disadvantage of obstructing the view depending on the mounting position of the viewing glasses. The advantage is that the diaphragm can be used many times since it can be pulled up.

In addition, it has been found that if there is only one moving rod, the partition plate becomes unstable, so it is desirable to have a plurality of moving rods.

(Effect) This invention can prevent the occurrence of thermal strain during single crystal pulling as much as possible, suppressing dislocations caused by this, and
In addition to being able to obtain a single crystal with fewer lattice defects, the material melt can be smoothly guided to the top surface of the partition plate even when using a partition plate that almost reaches the inner diameter of the crucible, and the material melt can also be stirred. This has the effect that no extra time is required for pulling the single crystal.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram schematically showing the present invention, Fig. 2 is a perspective view of a partition plate, and Fig. 3 is a schematic diagram for explaining temperature fluctuations when the partition plate is used and when it is not used. It is. DESCRIPTION OF SYMBOLS 1... Electric furnace body, 2... Heating means, 3... Crucible support rod, 4... Crucible, 5... Raw material melt, 6... Liquid sealant, 7... Single crystal pulling rod, 8... Seed crystal, 9... Interval board,
9a...Liquid cutting blade.

Claims (1)

[Claims] 1. When pulling a single crystal from a raw material melt contained in a crucible by the liquid capsule method, the furnace body is placed in a high-pressure gas atmosphere, and the single crystal is placed at a predetermined position below the surface of the raw material melt. A diaphragm having an outer diameter slightly smaller than the inner diameter of the crucible and having at least one or more liquid cutting blades on its outer periphery is floated so as to be able to move up and down, and the crucible is rotated while the single crystal is being pulled. The raw material melt below the diaphragm is guided to the solid solution interface on the top surface of the diaphragm through the cutting blades, and the diaphragm and the surface of the raw material melt are moved so that a predetermined distance is always maintained throughout the single crystal pulling process. 1. A method for growing a single crystal, the method comprising controlling the crucible, providing a plurality of heating means coaxially surrounding a crucible, and controlling the heating means independently. 2. The method for growing a single crystal according to claim 1, wherein the partition plate is pressed and controlled by a plurality of moving rods that are vertically movably suspended from the top of the crucible.