JPS5932430B2 - Manufacturing equipment for band-shaped silicon crystals - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing band-shaped silicon crystals.

The first thing to consider when performing crystal pulling is the balance between crystal pulling speed and heater power.

Generally, when pulling a crystal, it is necessary to reduce the heater power as the crystal pulling speed increases.

The purpose of this is to reduce the heat supplied from the heater to the solid-liquid interface by the latent heat generated when the silicon melt crystallizes, and to reduce the positional fluctuation of the solid-liquid interface.

A similar operation is required when pulling a band-shaped silicon crystal.

A solid-liquid interface shape suitable for pulling a band-shaped silicon crystal is such that the meniscus height is low at the ends in the width direction of the band-shaped silicon crystal and high at the center.

If this is reversed, crystal pulling will be difficult.

If the meniscus height at the ends in the crystal width direction is high, it is difficult to expand the crystal width and maintain a constant width, and if the meniscus height is reduced at the ends in the width direction, the meniscus height at the center part in the width direction also decreases. However, the growing band-shaped crystal is stuck to the capillary die.

However, when pulling a band-shaped crystal, although it is better to have a high meniscus height at the center in the width direction, if this becomes too extreme, crystal growth may not occur at the center of the capillary die, or This results in the inconvenience that a crystal having a thin crystal thickness can be obtained in some regions.

Now, when growing a band-shaped silicon crystal, when the crystal pulling speed is increased and the heater power is decreased, the meniscus shape generally changes.

The direction is such that when the meniscus height at the end portions in the crystal width direction is operated to be constant, the meniscus height at the center portion in the width direction increases.

This is a phenomenon that occurs because the temperature of parts other than the solid-liquid interface, which is unrelated to latent heat generation, steadily decreases as the heater power decreases, and the edges in the crystal width direction have better heat dissipation than the central part. .

Therefore, the conditions that determine the meniscus shape at the initial stage of crystal growth, where the crystal is pulled at a low speed, are not favorable under subsequent conditions where the pulling speed is high, and vice versa.

Conventionally, the solution to avoid such inconveniences was to provide electrical or mechanical means that could change the temperature distribution in the width direction of the band-shaped silicon crystal during crystal pulling, but this was extremely difficult. It was complicated.

The present invention provides a method for pulling a band-shaped silicon crystal in a desired shape by eliminating changes in temperature distribution from the initial stage of crystal growth to increasing the pulling speed without using such complicated methods. It is something to do.

In order to achieve this purpose, it is sufficient that the ends of the ribbon crystal in the width direction have large heat dissipation in the initial stage of crystal pulling, and then the heat dissipation decreases.

Therefore, in the present invention, as a seed crystal, an isosceles triangular plate part having an apex in the crystal pulling direction and having an obtuse apex angle, and the isosceles triangular plate part connecting the apex part and the seed crystal support body. The above object is achieved by using a plate-shaped crystal consisting of a parallel plate body having a width of 1/10 or less of the base of the body.

Figure 1a shows the main part of crystal pulling in one embodiment,
The figure shows the planar shape of the seed crystal.

In the figure, 1 is a quartz crucible containing a silicon melt 2, and a capillary die 3 (
3□, 3°) are arranged, and the seed crystal 4 is brought into contact with the melt 2 rising through the slit, and by pulling it up, a band-shaped silicon crystal 5 is obtained.

6 is a seed crystal support.

As shown in FIG. 1, the seed crystal 4 has an isosceles triangular plate portion 4a having an apex in the crystal pulling direction and an obtuse angle at the apex θ, and a portion between the apex portion and the seed crystal support 6. It consists of a parallel flat plate part 4b having a width d2 less than 1/10 of the base d1 of the isosceles triangular plate part 4a to be connected.

Specific experimental data will be listed below to clarify the effects of this invention.

First, as a capillary die 3, high-purity graphite with a specific gravity of 1.8 was cut into a piece with a width of 100 mm, a height of 40 m, 1 L, and a thickness of 3 rran.The tip was ground diagonally at a 30 degree angle, and a screw made of the same quality graphite was used to cut it through a spacer. It was configured to have slits with an interval of 0.3 nm.

These two capillary dies 3 were placed in a quartz glass crucible 1 with an inner diameter of 150 mmφ.

In the quartz glass crucible 1 other than the capillary die 3, 1001 high-purity raw material silicon grains with a resistivity of 50Ω are placed.
10 μgr of boron for doping was added.

Next, the crucible was set in a pulling furnace, and the temperature inside the furnace was raised.

After about 1 hour, the temperature inside the furnace rose to 1450°C, and the high purity silicon and doping boron were melted to form a melt 2.

When the temperature inside the furnace is further increased to 1500°C, the melt 2 begins to rise between the slits of the capillary die 3, and
After minutes the slit opening was filled.

When heating is slightly suppressed to create the temperature conditions necessary for growth,
The temperature at the end near the central axis was already high.

In this state, a seed crystal 4 having an isosceles triangular plate portion 4a with an apex angle θ of 120 degrees was struck into the melt 2 at the opening of the capillary die 3.

Hold it for a certain period of time, then 1 minute every minute. Pulling was started at a pulling speed of mm, and the heating conditions of the furnace were changed to lower the input power.

The width of the grown band-shaped crystal 5 was equal to the width d1 of the base of the isosceles triangular plate portion 4a, and the thickness at the center was not thin.

Next, we will show data that makes it clear that the shape of the seed crystal 4, especially the apex angle, is a decisive factor in determining the quality of the band-shaped crystal.

Specifically, after pulling a 1-meter belt-shaped crystal using the apex angle θ as a parameter, use the desired width of the crystal as a guideline, and determine that the thickness is thinner in the center as the desired thickness. A comparison was made to determine the defective rate.

In Figures 2 and 3, the apex angle θ of the seed crystal 4 is 20.40,5.
The defect rate was determined by selecting 0.80° ioo and 120°.

Note that the width d2 was set to 1/10 or less of the width d1 as in the example.

When the apex angle θ is as large as 120 degrees for both width and thickness, the defective rate is drastically reduced.

It can be seen that in a range where the apex angle θ is greater than 90 degrees, the defective rate is sufficiently small for practical use.

In terms of quality, it was confirmed that the larger the apex angle θ, the fewer accidents caused by band crystal breakage.

Furthermore, if the width d2 of the parallel plate portion 4b of the seed crystal 4 is not 1/10 or less of the width d1 of the base of the isosceles triangular plate portion 4a, the heat transfer to the seed crystal side will be too large and the solid-liquid interface will It was also confirmed that good quality band-shaped silicon crystals could not be pulled up due to poor thermal balance.

As described above, according to the present invention, by selecting the shape of the seed crystal, it is possible to stably pull a band-shaped silicon crystal in a desired shape without requiring complicated external temperature control.

[Brief Description of the Drawings] Figures 1a and 1b are explanatory diagrams of a growth method according to an embodiment of the present invention;
FIGS. 2 and 3 are diagrams showing the effects of the present invention. 1...Quartz glass crucible, 2...Silicon melt, 3□, 32...Capillary die, 4...Seed crystal, 4a... ...Isosceles triangular plate body part, 4b...Parallel plate body part, 5...
... Band-shaped silicon crystal, 6... Seed crystal support.

Claims (1)

[Claims] 1. A capillary die having a slit is arranged in a crucible containing silicon melt, a seed crystal is brought into contact with the melt rising through the slit, and the band-shaped silicon crystal is pulled up by pulling up the seed crystal. , as the seed crystal, an isosceles triangular plate part having an apex in the crystal pulling direction and having an obtuse apex angle, and an isosceles triangular plate part connecting the apex part and the seed crystal support. 1. A method for producing a band-shaped silicon crystal, characterized in that a plate-shaped crystal consisting of parallel plate portions having a width of 1/10 or less of the base is used.