JPH06102587B2 - Method of pulling silicon single crystal - Google Patents

Description

The present invention relates to a method for pulling a silicon single crystal by the Czochralski method (CZ method). More specifically, the present invention relates to a method for pulling a surface of a polycrystalline silicon nodule as a raw material. The present invention relates to a technique capable of reducing impurity contamination and eventually improving lifetime.

[Prior Art] With higher integration of devices in recent years, a higher-purity silicon single crystal has been required for manufacturing devices. Therefore, in order to meet such demands, when pulling a silicon single crystal using the CZ method, a silicon polycrystal nodule that is filled and melted in a quartz crucible is wet-cleaned with a chemical solution in advance (surface treatment with fluoronitric acid or the like). Impurities adhering to the surface of the polycrystalline silicon nodules are removed by corrosion (including corrosion). However, since the surface of the nodule of polycrystalline silicon has irregularities and the surface shape is complicated due to cracks caused by the manufacturing or processing steps, only the wet cleaning should be followed by careful rinsing. Also, it is difficult to remove the impurities adhering to the surface of the polycrystalline silicon nodules. On the other hand, the heater in the pulling device,
Quartz crucible filled with silicon polycrystalline nodules for the purpose of cleaning carbon products such as carbon susceptor and heat insulating member, after setting in the chamber of the pulling machine, the chamber was sealed, and the internal atmosphere was replaced with argon gas,
After that, for example, the pressure is reduced (50 Torr), and the inside of the chamber is heated under the reduced pressure at a temperature not higher than the melting point of the silicon polycrystal.

[Problems to be Solved by the Invention] However, even if the chamber is heated under reduced pressure in this manner, contaminants in the silicon polycrystal nodule or the cracks (residual chemical liquid during wet cleaning of the silicon polycrystal) Removal was incomplete.

The reason is that it is usually structurally unsuitable to make the chamber sufficiently airtight, and it is meaningless to make the chamber sufficiently airtight in terms of manufacturing cost. It is often difficult to reduce the degree of decompression in the chamber to 1 Torr or less. Also, there are some problems such as exhaust gas from the above-mentioned carbon products in the chamber and leakage of external atmosphere gas from the sealing part of the chamber, which causes One reason is that it is almost impossible to remove surface contamination.

Furthermore, the inner and outer surfaces of the quartz crucible are cleaned before being set in the chamber, but when holding and moving the quartz crucible, the outer surface of the quartz crucible is contaminated due to contact with the holder or contact with gloves during manual work. However, there is a drawback that the contamination is brought into the chamber.

As a result of the above, in the prior art, the contamination during the pulling of the silicon single crystal was significant and the lifetime could not be improved.

The present invention has been made in view of the above point, and an object thereof is to provide a technique capable of pulling a high-purity silicon single crystal.

[Means for Solving the Problems] In the method for pulling a silicon single crystal according to claim 1, the quartz crucible is filled with a silicon polycrystal nodule, and the quartz crucible is capped, and then the quartz crucible and the lid are separated from each other. While adsorbing under reduced pressure, the silicon polycrystal nodule is heated at a temperature lower than the melting point of the silicon polycrystal to clean the surface of the silicon polycrystal nodule, and then the quartz crucible and the lid are adsorbed under reduced pressure. The crucible was mounted in the chamber of the pulling machine using the attached handle of the lid, and then the lid was removed to melt the silicon polycrystal.

The method for pulling a silicon single crystal according to claim 2 is the method according to claim 1.
In the invention described above, in adsorbing the quartz crucible and the lid under reduced pressure, the upper end surface of the quartz crucible and the corresponding lower surface portion of the lid are highly flat and mirror-finished, and vacuum adsorption is performed without packing. It was something that I was supposed to do.

The method for pulling a silicon single crystal according to claim 3 is the method according to claim 1.
In the invention described, in adsorbing the quartz crucible and the lid under reduced pressure, adsorbed under reduced pressure via a packing made of silicon rubber, in adsorbing the quartz crucible and the lid under reduced pressure, via packing made of silicon rubber. It is designed to be adsorbed under reduced pressure.

In the method for pulling a silicon single crystal according to claim 4, in the invention according to claim 1, 2 or 3, when the lid is removed in the chamber, a clean inert gas heavier than the outside air is introduced into the quartz chamber. It was done.

[Operation] According to the above means, since the quartz crucible filled with the polycrystalline silicon agglomerates is directly covered, when heating the polycrystalline silicon agglomerates below the melting point, it is necessary to clean the pressure inside the quartz crucible. The pressure can be easily reduced to a certain degree. As a result, the removal of contaminants in the polycrystalline silicon nodules or cracks is facilitated.

The inner volume of the quartz crucible is relatively small, and the contact portion between the quartz crucible and the lid is, for example, heat resistant, and can be hermetically sealed by an elastic body packing that does not generate abnormal gas at high temperature. Instead of, the upper end of the quartz crucible is mirror-finished with a perfectly flat surface, and the corresponding part of this lid is also finished, so that a high degree of airtightness is possible without packing. In the latter case, it is not necessary to consider the packing material, which is most suitable for this purpose.

Here, the upper end surface of the quartz crucible and the lower surface portion of the lid in contact with the quartz crucible can be achieved by grinding, abrasive grain processing and mirror surface processing in which chemical action is added thereto. This surface roughness is the maximum height display, and if it is 500 Å or less, the purpose is sufficiently achieved.

In addition, since the handle attached to the lid is used to move the quartz crucible, contact between the holder and the quartz crucible and contact between the gloves and the quartz crucible during manual work are avoided, and the outer surface of the quartz crucible is completely free of contamination. You will not have the opportunity.

Therefore, according to the above silicon single crystal pulling method, a high-purity silicon single crystal can be obtained, and the lifetime can be improved.

In addition, since the nodule of the polycrystalline silicon set in the quartz crucible is shielded from the external atmosphere by the lid, impurities are not contaminated from the external atmosphere even when the quartz crucible is mounted in the chamber. Furthermore, after mounting the quartz crucible in the chamber of the puller, after filling the quartz crucible with an inert gas such as argon gas, the lid can be removed.
No exchange occurs between the atmosphere inside the quartz crucible filled with an inert gas such as argon gas and the atmosphere outside, and it is possible to reduce contamination from the atmosphere on the polycrystalline silicon surface.

[Example] An example of a method for pulling a silicon single crystal will be described below.

First, the silicon single crystal pulling machine will be described. This pulling machine comprises a lower chamber 41 and an upper chamber 42 as shown in FIG. Where the lower chamber
41 is a graphite crucible 43 for mounting the quartz crucible 2.
And a heater 44 for heating the quartz crucible 2. The upper chamber 42 is a chamber for pulling up and taking out a crystal, and a wire winding portion for pulling up the crystal and a rotating portion for rotating the seed crystal are formed at the upper end thereof.

Next, the vacuum suction device used in the examples will be described.

As shown in FIG. 1, this vacuum suction device 10 is provided with a lid 11 that is brought into close contact with the upper end of the quartz crucible 1 by vacuum suction.

That is, a flange 11a is formed on the edge of the lid 11, and a packing 12 made of, for example, silicone rubber is attached to the flange 11a with a screw 13 in order to improve adsorption. The edge of the lid 11 and the edge of the quartz crucible 2 are abutted against each other via the packing 12.

In addition, the eyebolt that forms the attached handle is on the front side of the lid 11.
A lid 14 is attached to the eyebolt 14, and a lifting machine (not shown) is connected to the eyebolt 14 so that the lid 11 can be lifted and transported.

The lid 11 is made of, for example, stainless steel, and the inner surface of the lid 11 is coated with Teflon to prevent contamination.

Further, the lid 11 has a gas supply / discharge pipe 21 connected to a gas supply / discharge device.
Are connected. The gas supply and exhaust pipe 21 is on the way to the gas exhaust pipe 21.
It is branched into a and a gas supply pipe 21b, the gas exhaust pipe 21a is connected to a vacuum exhaust device 30, and the gas supply pipe 21b is connected to a gas supply device (not shown). The gas exhaust pipe
A valve 22 and a leak valve 23 are provided in the middle of 21b. In addition, the gas exhaust pipe 21b is configured to be separable by the joint 31 at an intermediate portion thereof (a portion between the valve 22 and the leak valve 23). On the other hand, the filter 24 is provided with a valve 25 in the middle of the gas supply pipe 21b.

A pressure gauge 26 is provided in the middle of the gas supply / discharge pipe 21.

Next, the method of the embodiment performed using the vacuum suction device will be specifically described.

For example, the silicon polycrystal nodule 1 is filled in the quartz crucible 2 in a local clean room or a clean bench provided outside the pulling room. Next, the lid 11 is placed on the quartz crucible 2 via the eyebolt 14 by the lifting machine. At this time, the packing 12 of the lid 11 is brought into contact with the edge of the quartz crucible 2.

Next, by opening the valve 22, the inside of the quartz crucible 2 is evacuated, or after opening the valve 25 while evacuating, a clean inert gas such as argon gas in the quartz crucible 2 is introduced. The internal atmosphere pressure is, for example, 1T
The silicon polycrystal inside is heated to as high a temperature as possible while maintaining the temperature below orr. It is necessary to provide a heating source for this purpose at the bottom or on the side of the bottom, and at least prevent the lower surface of the lid 11 of the present adsorption device from exceeding the heat resistant temperature. For this reason, the lid 11 is effectively cooled by a water cooling jacket. When the lower surface of the lid 11 is coated with Teflon, the surface temperature is limited to 250 ° C. However, it is possible to heat the silicon polycrystal to 500 ° C. or higher by various means. At this time, it is necessary to maintain the pressure of the internal atmosphere at a pressure that does not hinder the close contact between the lid 11 and the quartz crucible 2.

As a result, the impurities attached to the silicon polycrystalline nodule 1 are released into the atmosphere, and the silicon polycrystalline nodule 1 is removed.
The surface is cleaned.

When the surface of the polycrystalline silicon nodule 1 is cleaned in this manner, the valve 25 is closed, while the valve 22 is left open, and the quartz crucible 2 is further evacuated (for example, about 500 Torr or less), and then the valve 22 is closed. And open the leak valve 23. As a result, the pressure inside the pipe after the valve 22 is returned to atmospheric pressure, and then the gas exhaust pipe 21a is separated at the joint 31 portion. As a result, the lid 11 and the vacuum exhaust device 30 are separated.

Pressure P (Torr) in the quartz crucible required for suction lifting
Is the sum of the weight of the filled silicon polycrystal and the weight of the quartz crucible, W (kg), and the cross-sectional area of the quartz crucible, A (cm ² ).
Then, since there is a relation of the following formula, Now suppose W = 71kg, A = 1500cm ² (when diameter is 44cm).
In addition, the pressure P required for suction lifting is 725 Torr, but it is preferable to select half the pressure P from the operating conditions. That is, the safety factor α = 10.

Then, with the lid 11 and the quartz crucible 2 being integrated, the quartz crucible 2 is transferred to the pulling chamber using the eyebolt 14 of the lid 11 by the lifting machine, and is installed there. It is mounted in the chamber 41.

Then, the quartz crucible 2 is filled with a clean inert gas such as argon gas to increase the pressure in the quartz crucible 2 to release the reduced pressure adsorption state, remove the lid 11, and close the upper chamber with 42.

Then, after the chamber is evacuated, the chamber is filled with an inert gas such as argon gas to reduce the pressure (50To
rr) Melting the nodule 1 of polycrystalline silicon.

According to the above silicon single crystal pulling method, since the quartz crucible 2 filled with the silicon polycrystal nodules 1 is directly covered with the lid 11, when heating the silicon polycrystal nodules 1 below the melting point, the inside of the quartz crucible 2 is heated. The pressure can be sufficiently reduced to the level required for cleaning. As a result, silicon polycrystalline nodules 1
Alternatively, removal of contamination in the crack is promoted.

Moreover, since the heat treatment of the silicon polycrystalline nodule 1 is not performed in the chamber of the pulling machine, contamination due to various structures in the chamber does not occur.

Further, since the eyebolt 14 of the lid 11 is used to move the quartz crucible 2, contact between the holder and the quartz crucible 2 and contact between the gloves and the quartz crucible 2 in the case of manual work are avoided, and the quartz crucible 2 outside The surface will have no chance of contamination.

Therefore, according to the above silicon single crystal pulling method, a high-purity silicon single crystal can be obtained, and the lifetime can be improved.

The experimental results are shown in FIG. Of these, the white circles represent the ingot lifetime of the silicon single crystal pulled by the conventional method, while the black circles represent the ingot lifetime of the silicon single crystal pulled by the method of the example.

It can be seen from FIG. 3 that the method of the embodiment improves the silicon single crystal lifetime as compared with the conventional method.

Further, since the silicon polycrystalline nodules 1 filled in the quartz crucible 2 are shielded from the external atmosphere by the lid 11, they are not contaminated with impurities from the external atmosphere even when mounted in the chamber. In addition, the quartz crucible 2 in the chamber of the puller.
After mounting, place an inert gas such as argon gas in the quartz crucible 2
Since the lid 11 is removed after filling the inside of the quartz crucible 2, the atmosphere inside the quartz crucible 2 filled with an inert gas such as argon gas does not exchange with the outside atmosphere. (1) Reduction of pollution from the atmosphere on the surface and, in turn, improvement of life time.

In the present embodiment, the silicon polycrystal nodule 1 is filled in the quartz crucible 2 in a clean room or a clean bench. Therefore, also in this respect, the contamination by the external atmosphere can be prevented.

Furthermore, since it is not necessary to clean the polycrystalline silicon nodules 1 in the chamber, the operating rate of the pulling machine can be improved.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments and various modifications can be made without departing from the scope of the invention. Nor.

[Effects of the Invention] The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.

A quartz crucible is filled with a polycrystalline silicon agglomerate, the quartz crucible is covered with a lid, the quartz crucible and the lid are adsorbed under reduced pressure, and the polycrystalline silicon agglomerate of silicon at a temperature lower than the melting point of the polycrystalline silicon under reduced pressure. To clean the surface of the polycrystalline silicon agglomerate, and then mount the quartz crucible in the chamber of the puller through the attached handle of the lid while the quartz crucible and the lid are adsorbed under reduced pressure. After that, the lid was taken out to melt the silicon polycrystal, so that the pressure inside the quartz crucible can be reduced to a level necessary for cleaning when the silicon polycrystal nodule is heated below the melting point. As a result, the removal of contaminants in the polycrystalline silicon nodules or cracks is facilitated.

In addition, since the handle attached to the lid is used to move the quartz crucible, the contact between the holder and the quartz crucible and the quartz crucible of the gloves during manual work is avoided, and the quartz crucible surface is completely contaminated. Will not have.

Therefore, according to the above silicon single crystal pulling method, a high-purity silicon single crystal can be obtained, and the lifetime can be improved.

Further, since the nodule of silicon polycrystal set in the quartz crucible is shielded from the external atmosphere by the lid, it is not contaminated with impurities from the external atmosphere even when it is mounted. Furthermore, after mounting the quartz crucible on the puller, after filling the inert gas such as argon gas into the quartz crucible and removing the lid, the inside of the quartz crucible filled with the inert gas such as argon gas can be removed. The atmosphere is not exchanged with the external atmosphere, and the contamination from the atmosphere of the silicon polycrystal surface can be reduced also there.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a vacuum adsorption device used in the method of the present embodiment, FIG. 2 is a schematic vertical sectional view of a pulling machine, and FIG. 3 is a diagram for comparing the effects of the present invention and the prior art. It is a comparison diagram of lifetime. 1 ... Silicon polycrystalline nodule, 2 ... Quartz crucible, 14 ... Handle,
41 ... Lower chamber, 42 ... Upper chamber.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-83887 (JP, A) JP-A-2-296788 (JP, A) JP-A-2-221183 (JP, A) JP-A-2- 22200 (JP, A) JP 59-102899 (JP, A) JP 63-285191 (JP, A)

Claims (4)

[Claims] 1. A quartz crucible is filled with a silicon polycrystal nodule, the quartz crucible is covered with a lid, and the quartz crucible and the lid are adsorbed under reduced pressure while the silicon polycrystal is melted at a temperature lower than the melting point of the silicon polycrystal. The crystal nodule is heated to clean the surface of the silicon polycrystal nodule, and then the quartz crucible and the lid are kept adsorbed under reduced pressure, and the quartz crucible is attached to the inside of the chamber of the puller using the attached handle of the lid. A method for pulling a high-purity silicon single crystal, characterized in that the silicon polycrystal is melted by mounting the lid on the substrate and then removing the lid. 2. When vacuum-adsorbing the quartz crucible and the lid under reduced pressure, the upper end surface of the quartz crucible and the corresponding lid portion are highly flatly mirror-finished to perform vacuum adsorption without using packing. The method for pulling a high-purity silicon single crystal according to claim 1, characterized in that. 3. The method for pulling a high-purity silicon single crystal according to claim 1, wherein the quartz crucible and the lid are adsorbed under reduced pressure through a packing made of silicon rubber. 4. The high-purity silicon unit according to claim 1, 2 or 3, wherein when the lid is removed in the chamber, a clean inert gas heavier than the outside air is introduced into the quartz chamber. Crystal pulling method.