JPH06100394A - Method for feeding raw material for producing single crystal and apparatus therefor - Google Patents

Abstract

PURPOSE:To provide a method for feeding a raw material for production of single crystal capable of feeding a granular silicon raw material sufficiently heated to a raw material melting part in a furnace for growing a silicon single crystal and distributing to, the stabilization of growth of silicon single crystal and an apparatus therefor. CONSTITUTION:An apparatus for feeding a raw material for production of a single crystal capable of continuously feeding a granular silicon raw material 16 to a furnace for growing a silicon single crystal is provided with a storage vessel 18 for storing the granular silicon raw material 16 and a feeder 21 for feeding the granular silicon raw material discharged from the storage vessel 18 to the furnace for growing the silicon single crystal, a flow path 24 for leading the granular silicon raw material 16 from the feeder 21 to the furnace for growing silicon single crystal and a heating mechanism 23 for heating the granular silicon raw material 16 discharged from the storage vessel by directly irradiating the granular silicon raw material 16 with heat energy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a raw material supply method and apparatus for producing a single crystal, which continuously supplies a granular silicon raw material to a silicon single crystal growing furnace for pulling a single crystal by the Czochralski method.

[0002]

2. Description of the Related Art A method for producing a silicon single crystal by the Czochralski method while continuously supplying raw materials (hereinafter, referred to as
The continuous feeding CZ method) is based on Japanese Patent Publication No. 40-10.
It is well known since ancient times, as seen in Japanese Patent No. 184.

In the conventional Czochralski method (hereinafter referred to as the CZ method) for producing a silicon single crystal, the silicon melt is reduced as the silicon single crystal is pulled up. Therefore, the dopant concentration and the oxygen concentration vary in the longitudinal direction of the crystal. In the case of strict specifications, the yield of usable silicon wafers may be 50% or less. On the other hand, in the above-mentioned continuous supply CZ method, since the amount of silicon melt can be kept constant, the production yield of silicon single crystals can be increased as compared with the CZ method.

A silicon single crystal growth furnace using the continuous feed CZ method generally has a structure shown in FIG. 6, as can be seen in Japanese Patent Publication No. 40-10184. In FIG. 6, reference numeral 3 is a quartz glass crucible in which the silicon melt 2 is stored. The quartz glass crucible 3 has a partition 4 provided concentrically with the outer wall thereof, the inside of the partition 4 is a single crystal growth portion (inner chamber) 3a, and the outside thereof is a raw material melting portion (outer chamber). It is 3b. Outside room 3b
A raw material supply pipe 7 is inserted in this, and the granular silicon raw material 6 is continuously supplied through this supply pipe 7. The partition 4 has a small hole 5 through which the silicon melt 2 is supplied from the raw material melting part 3b to the single crystal growing part 3a. Then, the silicon single crystal 1 is pulled upward from the upper portion of the single crystal growth portion 3a. The reference numeral 8 indicates the crucible 3
It is a resistance heater for melting the silicon raw material 6 supplied therein.

In such a single crystal growing furnace, a granular silicon raw material having a weight equal to the weight of the silicon single crystal grown in the single crystal growing portion 3a is supplied to the raw material melting portion 3b outside the partition 4 to make the quartz glass. The amount of silicon melt in the crucible 3 can be kept constant.

However, when the single crystal diameter is as large as 6 inches or more and when the single crystal growth rate is high, the supply amount of the granular silicon raw material also increases. Therefore, (1) the granular silicon raw material supplied to the raw material melting portion may become unmelted and may cover the surface of the silicon melt in the raw material melting portion, (2) the granular silicon raw material supplied may be at a low temperature (room temperature). ), The fluctuation of the temperature of the silicon melt becomes large, which promotes dislocation of the silicon single crystal and deterioration of the crystal quality. (3) Due to the temperature difference between the granular silicon raw material and the silicon melt at the time of supplying the raw material Due to the generated thermal stress, the frequency of crushing and scattering of the granular silicon raw material increases, and if it adheres to the growing silicon single crystal, it causes dislocation. Also, contamination in the furnace due to scattering of crushed granular silicon raw material or unmelted granular silicon raw material,
If it adheres to a member such as a heat insulating material in the furnace, the problem of accelerating deterioration occurs. As techniques for preventing such a problem, for example, the following techniques a) to d) are known.

(A) In Japanese Patent Laid-Open No. 1-1119592, a granular silicon raw material is heated by sucking a high-temperature atmosphere gas near the crucible from a supply pipe for supplying the granular silicon raw material. Also, (b) Japanese Patent Laid-Open No. 1-1195.
No. 94 and C) Japanese Patent Laid-Open No. 3-8790 discloses that granular silicon raw material is supplied by radiant heat from a heat source heating the entire silicon melt by prolonging the passage time of the granular silicon raw material in the supply pipe. It is heated in the supply pipe. Further, d) Japanese Patent Application Laid-Open No. 2-243587 discloses a method in which a new heat source is added to heat a granular silicon raw material on the melt outside the partition.

[0008]

However, in the invention disclosed in JP-A-1-119592, the silicon oxide and the impurities contained in the high temperature atmosphere gas are sucked simultaneously with the high temperature atmosphere gas. However, there is a problem that the entire raw material supply device is contaminated. Further, in the inventions disclosed in (b) Japanese Patent Application Laid-Open No. 1-1119594 and (c) Japanese Patent Application Laid-Open No. 3-8790, the moving speed of the granular silicon raw material in the supply pipe is reduced in order to sufficiently heat the granular silicon raw material. There is a need to. However, if the granular silicon raw material is slowed down too much, the granular silicon raw material will sinter on the inner wall of the supply pipe and eventually block the supply pipe. Therefore, there is a problem that the granular silicon raw material cannot be stably supplied. Further, d) the invention disclosed in Japanese Patent Application Laid-Open No. 2-243587 has a problem that when the granular silicon raw material is supplied to the silicon melt of the raw material melting portion, the granular silicon raw material is crushed and the temperature of the silicon melt is fluctuated. Not resolved.

The present invention has been made in view of such circumstances, and it is possible to supply a sufficiently heated granular silicon raw material to a raw material melting portion in a silicon single crystal growth furnace,
An object of the present invention is to provide a raw material supply method and apparatus for producing a single crystal, which can contribute to stabilization of growth of a silicon single crystal.

[0010]

In order to solve the above problems, the present invention is, firstly, to provide a raw material supply method for producing a single crystal for continuously supplying a granular silicon raw material to a silicon single crystal growing furnace. That is, the step of continuously discharging the granular silicon raw material stored in the storage container, the step of directly irradiating the discharged granular silicon raw material with thermal energy to heat the granular silicon continuously, and the heated granular silicon raw material. And a step of continuously supplying a silicon raw material to a silicon single crystal growing furnace, to provide a raw material supply method for producing a single crystal.

Secondly, there is provided a raw material supply device for producing a single crystal, which continuously supplies the granular silicon raw material to the silicon single crystal growing furnace, and a storage container for storing the granular silicon raw material and a discharge from this storage container. A feeder for supplying the granular silicon raw material toward the silicon single crystal growing furnace, a channel for guiding the granular silicon raw material from the feeder to the silicon single crystal growing furnace, and the granular silicon discharged from the storage container. A raw material supply device for producing a single crystal, comprising: a heating means for directly irradiating and heating the raw material with thermal energy.

In this case, it is preferable that the heating means has a light source for emitting a laser or infrared rays, and irradiates the granular silicon raw material with laser or infrared rays. Further, it is preferable to further provide a second heating means for heating the granular silicon raw material in the vicinity of the flow path.

[0013]

In the present invention, since the granular silicon raw material discharged from the storage container is directly irradiated with thermal energy to continuously heat the granular silicon raw material, the granular silicon raw material is effectively heated and the temperature is sufficiently higher than room temperature. Supplied in a crucible. Therefore, the silicon melt does not solidify at the time of supplying the granular silicon raw material, the temperature fluctuation of the silicon melt, the crushing and scattering of the granular silicon raw material can be reduced, and the single crystal can be pulled up without dislocation. Further, it is possible to suppress the occurrence of crystal defects due to the temperature fluctuation of the silicon melt.
In addition, since the heating area can be made extremely narrow,
Only the silicon raw material can be effectively heated, and the peripheral members are not unnecessarily heated.

In this case, if a laser or infrared rays is used as the heat source of the heating means, sufficient heat energy can be supplied to the raw material, so that the heating efficiency can be increased. Further, by providing the heating means also in the flow path of the raw material reaching the single crystal growth furnace, it is possible to prevent the temperature of the raw material from lowering and reduce the adverse effect on the silicon melt.

The idea of heating the granular silicon raw material with a heater before it is supplied to the single crystal growth furnace is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-83887. However, in this publication, since heating is performed from the outside of the raw material storage container, the heating efficiency is inevitably low. On the other hand, in the present invention, as described above, the raw material discharged from the storage container is directly irradiated with thermal energy, so that the raw material can be heated with extremely high efficiency.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing a raw material supply apparatus for producing a single crystal according to an embodiment of the present invention. This supply device 10 is provided with a raw material supply chamber 17 connected to a silicon single crystal growth furnace, which will be described later, and a hopper 18 which is arranged in the upper part of the chamber 17 and stores the granular silicon raw material 16.
And a rotary feeder 21 which is disposed immediately below the hopper 18 and continuously supplies the granular silicon raw material discharged from the discharge port 18a at the bottom of the hopper 18 to the downstream side, and a granular feeder cut out from the hopper 18 by the feeder 21. Flow path 24 for introducing silicon raw material into a silicon single crystal growth furnace
And an infrared irradiation heating device 23 for directly irradiating infrared rays to the granular silicon raw material 16 discharged from the discharge port 18a and temporarily staying on the rotary feeder 21 to heat it. A funnel-shaped receiving portion 22 that receives the raw material from the feeder 21 is provided on the upper portion of the flow path 24.

In the raw material supply apparatus for producing a single crystal thus constructed, the rotary feeder 21 is rotated around the shaft 20 at a predetermined speed, and the granular silicon raw material 16 discharged from the hopper 18 is driven at a constant speed. Supply continuously to the single crystal growth furnace. The raw material from the feeder 21 is introduced into the single crystal growth furnace through the flow path 24.

At this time, the granular silicon raw material discharged from the discharge port 18a and temporarily retained on the rotary feeder 21 is irradiated with infrared rays from the infrared irradiation heating device 23. In this case, since the raw material is heated directly, the heating efficiency can be increased. Moreover, since the heating region is very narrow, only the granular silicon raw material can be effectively heated. Furthermore, since the peripheral members are not unnecessarily heated, it is easy to take thermal measures.

As shown in FIG. 2, a heater 25 is provided around the flow path 24 to heat the raw material flowing through the flow path 24, whereby the temperature of the raw material can be prevented from lowering and the single crystal can be prevented. The adverse effect on the silicon melt in the growth furnace can be further reduced.

Next, the single crystal pulling apparatus 30 of the continuous feeding CZ apparatus using the above-mentioned raw material feeding apparatus 10 will be described with reference to FIG. In this single crystal pulling apparatus 30, a silica glass crucible 33 charged with a silicon melt 32 is set in a graphite crucible 39, and its outer diameter is, for example, 20 inches. Quartz glass crucible 33
Inside the partition member 34 is provided concentrically with the outer wall.
The inside of the partition 34 is a single crystal growth portion (inner chamber) 33a, and the outside thereof is a raw material melting portion (outer chamber) 33b. The partition member 34 is made of quartz glass and has an outer diameter of 16 inches. The partition member 34 has a small hole 35.
Is provided, and the silicon melt 32 is supplied from the raw material dissolving part 33b to the single crystal growing part 33a through this.
Then, the silicon single crystal 31 grown in a columnar shape is pulled from the melt 32 in the single crystal growing portion 33a. The graphite crucible 39 is supported by the pedestal 40 and can move up and down and rotate. Reference number 3
Reference numeral 8 is a resistance heater surrounding the graphite crucible, 41 is a heat retaining member surrounding the resistance heater 38, and all of them are housed in the pulling furnace chamber 44.
The above configuration is basically the same as that of the silicon single crystal manufacturing apparatus using the CZ method.

The inside of the raw material supply device 10 and the inside of the single crystal pulling device 30 are kept in the same atmosphere and are evacuated by a vacuum pump (not shown) and kept under reduced pressure, or an inert gas supply source (not shown). An inert gas is introduced from the above to maintain the atmosphere in the inert gas atmosphere.

The granular silicon raw material 16 from the above-described raw material supply device 10 is continuously supplied to the raw material melting portion 33b of the quartz glass crucible 33 through the supply pipe 37, and is continuously melted there. As a result, continuous pulling of the single crystal is realized.

In this case, since the granular silicon raw material is sufficiently heated, the silicon melt does not solidify when the granular silicon raw material is supplied, and the temperature fluctuation of the silicon melt, the crushing and scattering of the granular silicon raw material are reduced. Therefore, the single crystal can be pulled without dislocation. Further, it is possible to suppress the occurrence of crystal defects due to the temperature fluctuation of the silicon melt. Next, specific examples of the present invention will be described.

Granules heat-treated under the following conditions using a continuous supply CZ apparatus equipped with the raw material supply apparatus configured as shown in FIG. 1 and the single crystal pulling apparatus configured as shown in FIG. A silicon single crystal pull-up test was performed using a silicon raw material. In the raw material supply device of FIG. 1, as described above, when the granular silicon raw material 16 that has descended from the granular silicon raw material storage hopper 18 is temporarily retained on the rotary feeder 21 that is the quantitative cutout unit. Then, the infrared irradiation device 23 locally heats and raises the temperature. The heating area of the infrared irradiation device 23 is 20 mm and the maximum output is 2 kW, and the heating temperature of the granular silicon raw material can be appropriately set by adjusting the output.
For example, the supply rate of the granular silicon raw material is 50 g / min
When set to, the granular silicon raw material is the rotary feeder 21.
It stays above for about 15 seconds and is heated at that time. In addition,
At this time, the inside of the raw material supply device 10 and the inside of the single crystal pulling device 30 are maintained in a reduced pressure atmosphere of argon, and the internal pressure of the furnace is 15 to 3
It was 0 Torr.

In this embodiment, the output of the infrared irradiating device is 0.10 kW (case 2), 0.16 kW (case 3), 0.24 kW (case 4), 0.33 kW (case 5), 0.50 kW (case 5). Case 6), 0.67 kW (case 7), 0.85 kW (case 8), 0.95 kW
When the heat treatment is performed by setting (Case 9), and when the infrared irradiation device is not used, that is, when 0 kW (granular silicon raw material temperature is room temperature (25 ° C.), Case 1), the total of 9 cases The silicon single crystal pull-up test was carried out 10 times in each case using the granular silicon raw material of No. 1. The granular silicon raw material used had an average particle diameter of 1 mm and a particle diameter range of 0.1 mm to 3 mm, and the raw material supply rate was 50 g / min. Further, the elapsed time until the heated granular silicon raw material dropped from the rotary feeder and was supplied to the raw material melting portion in the crucible was about 3 sec.

A silicon single crystal having a diameter of 6 inches was pulled at a pulling rate of 1.
It was pulled up under the condition of 1 mm / min. At this time, a silicon single crystal whose straight body portion was pulled up by 1 m or more without dislocation was regarded as good. The temperature of the granular silicon raw material at the time of being supplied to the raw material melting portion after heating was measured by a thermocouple by performing a preliminary test. The results of the silicon single crystal pull-up test and the dislocation-free probability in the above 9 cases are shown in Table 1 and FIG.

[0028]

[Table 1]

In case 1, dislocation-free single crystals were grown in 3 out of 10 pulling tests. On the other hand, in cases 2 to 8 in which the raw material is heated, case 1
It was confirmed that the probability of growing dislocation-free single crystals was higher than that of, and that the probability increased as the temperature of the granular silicon raw material during supply increased.

In these cases 2 to 8, at the same time, the crushing and scattering of the granular silicon raw material was reduced, the contamination in the furnace and the adhesion of the granular silicon raw material to other members were also reduced. After the tests of Cases 1, 3, 5 and 7 were completed, based on the number of fragments of the granular silicon raw material recovered from the inside of the silicon single crystal pulling apparatus and the total weight of the granular silicon raw material supplied to the raw material melting section in the experiment,
The number of residual granular silicon raw material fragments per 1 kg of the raw material was calculated. The results are shown in Table 2.

[0031]

[Table 2]

From Table 2, it is confirmed that as the temperature of the granular silicon raw material during the supply of the raw material melting portion increases, the number of residual granular silicon raw material fragments per 1 kg of the raw material decreases. This indicates that the heating of the granular silicon raw material made it difficult for the raw material to be crushed and scattered, and as a result, the frequency of inhibiting the growth of the single crystal was significantly reduced. It was also confirmed that the adhesion to the members in the furnace was reduced and the life of these members was extended.

It was also confirmed that by heating the granular silicon raw material to raise its temperature, the probability of solidification of the silicon melt when the granular silicon raw material was supplied to the raw material melting section in the crucible was reduced.

The experiment at this time will be described. The temperature of the granular silicon raw material when supplied to the raw material melting part is 25 ° C.
(Case 10), 180 ° C (Case 11), 350 ° C
(Case 12), 580 ° C (Case 13), 800 ° C
Under heating conditions such as (Case 14), the supply rate of the granular silicon raw material is set to 35, 40, 45, 50, 55, 60.
The silicon single crystal was grown at g / min.
The pulling rate of the single crystal was changed according to the supply rate of the granular silicon raw material so that the amount of silicon melt was constant.

At this time, the solidification state of the silicon melt in the raw material melting portion was observed by carrying out a silicon single crystal pulling test (30 cases in total) having a diameter of 6 inches 10 times for each case. In the above test, the output of the infrared irradiation device was changed to maintain the desired granular silicon raw material temperature. Further, it was determined that the silicon melt was solidified when the supplied granular silicon raw material became in an unmelted state in the raw material melting section and the predetermined granular silicon raw material supply rate could not be maintained. The experimental results are shown in Table 3 and FIG.

[0036]

[Table 3]

When the temperature of the granular silicon raw material when it is supplied to the raw material melting portion is 25 ° C. (case 10) and the supply rate of the granular silicon raw material exceeds 50 g / min, the silicon melt in the raw material melting portion solidifies, It became impossible to continue the growth of the silicon single crystal. On the other hand, as the temperature of the granular silicon raw material increased, the solidification probability of the silicon melt in the raw material melting portion was greatly reduced. Further, the temperature fluctuation of the silicon melt due to the supply of the granular silicon raw material is reduced,
It was confirmed that the generation of crystal defects due to the temperature fluctuation of the melt was suppressed.

However, as shown in Case 9 in Table 1, even when the granular silicon raw material is heated, if the temperature is too high at 800 ° C., stable raw material supply may not be possible. This is because the silicon raw material having a small particle size or powder is sintered on the pipe wall at the lower end of the supply pipe 37 installed immediately above the silicon melt, and finally the phenomenon of clogging occurs. Further, in the case 9, even on the rotary feeder, the small particle size or powdery silicon raw material may be sintered due to heating, and stable raw material supply may not be possible. At this time, the temperature of the granular silicon raw material on the rotary feeder was measured by a thermocouple, and it was 1100 ° C.

Further, in the case 9, the temperatures of the silicon melt, the quartz glass crucible, and the quartz glass partition member in the raw material melting portion become too high as compared with those in the case 1, which accelerates the deterioration of the quartz glass member. It was confirmed that the probability of dislocation-free sintering being grown was further deteriorated.

From the above results, it was confirmed that the temperature of the granular silicon raw material at the time of supplying the raw material melting portion is preferably in the range of 350 ° C to 700 ° C. Further, in order to stably supply the raw material without sintering the granular silicon raw material on the rotary feeder, the temperature of the granular silicon raw material on the rotary feeder needs to be lower than 1100 ° C. confirmed.

On the rotary feeder, 110
Since the granular silicon raw material having a temperature of less than 0 ° C. maintains the temperature of 350 ° C. to 700 ° C. at the time of feeding the raw material melting portion, the granular silicon raw material is fed from the rotary feeder for 3 seconds.
It is desirable to supply the raw material to the raw material melting section within that time. further,
In order to provide a stable supply of granular silicon raw materials without clogging,
The distribution channel must have an angle of 25 degrees or more from the horizontal plane. Therefore, the rotary feeder is 2
It is necessary to install the granular silicon raw material at a position where the granular silicon raw material can pass through and reach the raw material melting portion within 3 seconds through a flow path having an angle of 5 degrees or more.

In the above embodiment, the case where the granular silicon raw material is heated by the infrared irradiation heating device has been described, but the present invention is not limited to this, and for example, laser irradiation in which a heating region can be selected by scanning a beam. A heating device can also be used. Further, although the example in which the granular silicon raw material is supplied by the rotary feeder has been shown, the present invention is not limited to the rotary feeder, and a vibrating feeder may be used, for example.

[0043]

According to the present invention, the sufficiently heated granular silicon raw material can be supplied to the raw material melting portion in the silicon single crystal growth furnace, and the single silicon crystal growth can be stabilized. A method and an apparatus for supplying a raw material for crystal production are provided.

[Brief description of drawings]

FIG. 1 is a sectional view showing a raw material supply apparatus for producing a single crystal according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a raw material supply apparatus for producing a single crystal according to another embodiment of the present invention.

3 is a cross-sectional view showing a pulling device of a continuous CZ device to which the raw material supply device of FIG. 1 is applied.

FIG. 4 is a diagram showing a relationship between the temperature of the granular silicon raw material when the crucible is supplied and the dislocation-free probability of the pulled single crystal.

FIG. 5 is a diagram showing a relationship between a raw material supply rate and a solidification probability of a silicon melt.

FIG. 6 is a conceptual diagram showing a conventional continuous CZ device.

[Explanation of symbols]

10; Raw material supply device, 16; Granular silicon raw material, 17;
Raw material supply chamber, 18; hopper, 20; rotating shaft,
21: rotary feeder, 22: receiving part, 23: infrared irradiation heating device, 24: flow path, 25: heater.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinobu Shima 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (4)

[Claims] 1. A raw material supply method for producing a single crystal, which continuously supplies a granular silicon raw material to a silicon single crystal growth furnace, comprising a step of continuously discharging the granular silicon raw material stored in a storage container, and discharging. Characterized by comprising a step of continuously heating the granular silicon raw material by directly radiating thermal energy to the granular silicon raw material, and a step of continuously supplying the heated granular silicon raw material to the silicon single crystal growth furnace. A method of supplying a raw material for producing a single crystal. 2. A raw material supply device for producing a single crystal, which continuously supplies a granular silicon raw material to a silicon single crystal growth furnace, and a storage container for storing the granular silicon raw material, and granular silicon discharged from the storage container. A feeder for supplying the raw material toward the silicon single crystal growing furnace, a flow path for guiding the granular silicon raw material from the feeder to the silicon single crystal growing furnace, and a direct heat to the granular silicon raw material discharged from the storage container. A raw material supply device for producing a single crystal, comprising: a heating means for irradiating energy and heating. 3. The raw material supply apparatus for producing a single crystal according to claim 2, wherein the heating means has a light source for emitting a laser or infrared rays, and irradiates the granular silicon raw material with laser or infrared rays. . 4. The raw material supply apparatus for producing a single crystal according to claim 2, further comprising a second heating unit which is provided in the vicinity of the flow path and which heats the granular silicon raw material.