JPH0251492A - Single crystal pulling-up device - Google Patents

Abstract

PURPOSE:To improve the lessening effect of axial temp. gradient by providing such insulating plates with a distance between each other in the insulating tube covering the pulling-up area that have openings which make small annular gaps between a pulling-up shaft. CONSTITUTION:A top insulating plate 6 having the opening the diameter of which is larger by 6-10mm than that of the pulling-up shaft 12 is provided on the upper end surface of the insulating tube 5 covering the pulling-up area of single crystal, and plural intermediate partition insulating plates 7 having the openings the diameter of which are larger by 6-10mm than that of the single crystal 1 pulled up in the inside of the insulating tube 5 are axially disposed with a distance between each other, and plural annular spaces B and C of large volume are formed between the intermediate partition insulating plates each other and between the top insulating plate 6 and the next intermediate partition insulating plate. By this method, the device is free from the need of multistage heaters and an electric power source as in the case of multi-hot- zone type device, and the structure is simple and its cost is low as well as the maintenance is easy.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a single crystal pulling apparatus for growing a single crystal from a crystal raw material melt by a liquid-sealed pulling method, comprising:
The present invention relates to an apparatus including a heat insulating cylinder surrounding the pulling area above the crucible.

[Conventional technology]

An example of the structure around the crucible in this type of single crystal pulling apparatus is shown in FIG. The crystal raw material and the liquid sealant are placed in the crucible 8 while surrounding the bedistal container 9.
A heater 2 is disposed for melting the inside, and a cylindrical side heat shield 4 is disposed surrounding the heater 2. A ring-shaped heat shield 4a is provided on the upper end surface of the side heat shield 4 to cover the upper end surface of the heater 2 and suppress heat from directly escaping upward. A heat insulating cylinder 5 is placed to surround the pulling area when pulling the single crystal from the wafer.This heat insulating cylinder 5 and a top heat shield 3 covering the upper part of the heat insulating cylinder 5 at a distance maintain the temperature in the axial direction of the single crystal 1. The gradient is made gentle to suppress the generation of distortion due to thermal stress within the single crystal.

[Problem to be solved by the invention]

The problems with the single crystal pulling apparatus having the crucible and its surroundings configured in this way are as follows. That is, in the shape of the heat insulating cylinder as shown in FIG. 2, the crystal raw material melt 10
Because the temperature is high, the inert gas in the atmosphere causes convection, and the heat insulating tube acts just like a smoke tube. According to the inventor's experiments, it was found that it was not very effective in alleviating the temperature gradient. - On the other hand, in order to effectively alleviate the temperature gradient, heaters are arranged in multiple stages in the axial direction within the pulling region of the single crystal, to actively reduce the axial temperature gradient, and to A multi-hot zone method for annealing crystal ingots is known. However, with this method, the structure is complicated because the heaters are in multiple stages, and a power source must be provided for each heater, which is not only expensive economically, but also difficult to maintain and inspect. There was a drawback.

The purpose of the invention is to be economically inexpensive and easy to maintain.

It is an object of the present invention to provide a single-crystal pulling device that is easy to inspect and equipped with a heat-insulating cylinder that has a large effect of alleviating temperature gradients in the axial direction.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, a heat insulating cylinder surrounding a pulling area above a crucible in a single crystal pulling apparatus is configured to have a hole having a size that forms a small ring-shaped gap between it and the pulling shaft. A top heat insulating plate is provided at the upper end, and a middle partition heat insulating plate having a hole large enough to form a small ring-shaped gap between the outer circumferential surface of the single crystal to be pulled and the middle partition heat insulating plate is spaced in the axial direction inside the heat insulating cylinder. It shall be configured as follows.

[Effect]

When the heat insulating tube is configured in this way, the inert atmospheric gas rising from the crucible side passes through the small ring-shaped gap formed between the circumferential surface of the single crystal ingot and the intermediate heat insulating plate, and flows between the middle partition heat insulating plates. Each time the gas is released into the large ring-shaped space formed between them, a vortex is formed, and each time a part of the rising energy is consumed as vortex energy, so the rising speed of the gas is significantly reduced and convection is reduced. temperature gradient is significantly smaller than that of the conventional method.

Moreover, unlike the conventional multi-hot zone method, this configuration does not require multistage heaters or power supplies, making the configuration extremely simple, economically viable, and easy to maintain and inspect. It is possible.

〔Example〕

In the first drawing showing an embodiment of the present invention, the same members as those in FIG.

The upper end surface of the conventional heat insulating cylinder 5, which has a length that sufficiently covers the pulling area of the single crystal, is
A top heat insulating plate 6 having holes with a lot diameter larger is fixedly installed, and inside the heat insulating cylinder 5 there is also an intermediate partition heat insulating plate 7 having holes with a diameter 6 to 10 times larger than the diameter of the single crystal l to be pulled. are arranged at intervals in the axial direction, forming a plurality of large-volume phosphor spaces B and C between the intermediate heat-insulating plates and between the top heat-insulating plate 6 and the next intermediate partition heat-insulating plate. ing.

When pulling a single crystal, inert atmospheric gas flowing upward from the high-temperature crucible 8 side passes through a small ring-shaped gap A with a gap width of 3 to 5 m and enters a large-volume ring-shaped space B.

As a result, a vortex is generated in the ring-shaped space B, and a part of the energy of the upward gas flow is consumed as vortex energy, and in this way, each time it passes through the small ring-shaped gap and enters the next ring-shaped space. Each time, the gas rises while losing upward energy, and finally exits through the ring-shaped small gap D around the pulling shaft 12, which has a smaller one-passage area.

In this embodiment, all the holes in the plurality of intermediate heat-insulating plates 7 are holes with the same size, which is 6 to Lotm larger than the diameter of the single crystal l, but these holes become smaller toward the top of the intermediate heat-insulating plates. It is also possible to do this, and in this case, the heat retention effect and therefore the temperature gradient relaxation effect will be even greater.

(Effects of the Invention) As described above, according to the present invention, the structure of the heat insulating cylinder that surrounds the single crystal pulling region above the crucible and suppresses the generation of strain due to thermal stress within the single crystal is combined with the pulling shaft. A top heat insulating plate having a hole sized to form a small ring-shaped gap between the two is provided at the upper end, and an intermediate partition having a hole sized to form a small ring-shaped gap between the outer circumferential surface of the single crystal to be pulled. Since the heat insulating plates are arranged at intervals in the axial direction inside the heat insulating cylinder, inert atmospheric gas rising from the crucible side is formed between the peripheral surface of the single crystal and the intermediate partition heat insulating plate. Each time the liquid passes through the small ring-shaped gap and is released into the large ring-shaped space formed between the partition plates, it forms a vortex, and each time a part of the rising energy is consumed as the energy of the vortex. As a result, the rising speed of the gas is significantly reduced and convection is suppressed, so the temperature gradient in the axial direction of the single crystal becomes significantly smaller than that of the conventional heat-insulating tube. Unlike the multi-hot zone system, multi-stage heaters and power supplies are not required, the structure is extremely simple, it is economically inexpensive, and maintenance and inspection can be easily performed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the area around the crucible showing an example of the structure of the heat insulating cylinder of the single crystal pulling device according to the present invention, and Fig. 2 is a block diagram of the area around the crucible showing an example of the structure of the heat insulating cylinder of the conventional single crystal pulling device. It is. 1: Single crystal, 5: Heat insulating tube, 6: Top heat insulating plate, 7: Intermediate partition heat insulating plate, 8 Niru pot, 10: Crystal raw material melt, 1
1: Liquid sealant, 12: Pulling shaft. /2P1-L1B °Yuu Right Figure 1 Figure 2

Claims (1)

[Claims] 1) A single crystal pulling apparatus for growing a single crystal from a crystal raw material melt by a liquid-sealed pulling method, which is equipped with a heat-retaining cylinder surrounding a pulling region above a crucible, in which the heat-retaining cylinder is equipped with a top heat insulating plate at the upper end having a hole large enough to form a small ring-shaped gap between it and the pulling shaft, and a top heat-insulating plate large enough to form a small ring-shaped gap between it and the outer peripheral surface of the single crystal to be pulled. A single-crystal pulling apparatus characterized in that intermediate partition heat-insulating plates having holes are provided inside a heat-insulating cylinder at intervals in the axial direction.