JPH0558770A - Production of n type silicon single crystal - Google Patents

Abstract

PURPOSE:To pull an N type silicon single crystal in a high yield by using a synthetic quartz glass crucible as a crucible for pulling when a silicon single crystal is grown by a pulling method. CONSTITUTION:A silicon single crystal is pulled from a synthetic quartz glass crucible. The defect density of the resulting silicon wafer is <=3 per 1cm<2>. The synthetic quartz glass crucible is formed from an amorphous sintered body of colloidal silica obtd. by hydrolyzing and polycondensing alkoxysilane and contains <=100ppb each of Al and Fe, <=50ppb each of Ni and Cr and <=10ppb each of B and P as impurities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an N-type silicon single crystal, and particularly to a silicon wafer capable of pulling an N-type silicon single crystal with a good yield and having microscopic defects of 3 / cm ² or less. The present invention relates to a method for producing an N-type silicon single crystal that gives

[0002]

2. Description of the Related Art In the production of silicon single crystals, high-purity polycrystalline silicon, which is a raw material for pulling, is charged into a crucible, which is melted under atmospheric pressure in an argon gas atmosphere, and a silicon seed crystal is added to this melt. This is done by immersing it and pulling it up, but this crucible is usually made of natural quartz glass because it withstands the high temperature of 1,414 ° C which is the melting point of silicon.

However, since this natural quartz glass contains a considerably large amount of various metals as impurities, and thus the obtained silicon single crystal contains impurities, the impurities are removed from this crucible. Various items have been proposed. That is, as shown in Table 1, transition metals and B have a low level [abbreviated as crucible A] (see Japanese Patent Publication No. 58-49519), and Na, K, and Li are 0.2 ppm or less. , Cu to 0.02 ppm or less to suppress wafer quality and generation of minute defects [abbreviated as crucible B] (see Japanese Patent Publication No. 1-6158).
Not only, P, A _s also those with low levels [abbreviated as crucible C] (see JP-A-62-96388), Al, Fe, N
It has been proposed that a, K, and Ca are 0.1 ppm or less [abbreviated as crucible D] (see US Pat. No. 4,979,973).

[0004]

[Table 1]

[0005]

However, the trend toward higher integration of silicon semiconductor devices is gradually accelerated, and 64M,
It has been advanced from 256M to 1G, and the minimum line width of these is said to be 0.2 μm. Even at 64M, if the defect density is 3 defects / cm ² or less, the yield does not improve and the bit cost increases.
It is expected to exceed 16M. In particular, the trend toward higher integration, higher speed, and faster memory of MPUs demands for epitaxial wafers, N-type wafers of CMOS and Bi-CMOS types. However, since the yield of N-type single crystal is lower than that of P-type, it is strongly desired to improve the yield and reduce defects.

The N-type silicon single crystal is manufactured by doping a pentavalent element. The pentavalent element is easily combined with the trivalent element to form a compound. As can be seen from Table 2, trivalent elements such as Al and B are dissolved from the crucible, but these condense with pentavalent doped elements such as P and Sb, causing the resistance value to change and the yield to be extremely high. It gets worse. Further, this compound causes the generation of microdefects, and the microdefects increase with time or by heat treatment. In addition, transition metals such as Fe, Ni, and Cr also act as elements that cause microdefects, and this is also supposed to be based on the similar principle.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for producing an N-type silicon single crystal which has solved such disadvantages, and is characterized in that the silicon single crystal is pulled up from a synthetic quartz glass crucible. To do.

That is, the present inventors have conducted various studies on a method for producing an N-type silicon single crystal with high yield. As a result, the crucible for pulling up this silicon single crystal is made of synthetic quartz glass. However, the N-type silicon, which has a poor yield in the past, can be pulled up with a good yield, and the silicon wafer obtained from the N-type silicon single crystal thus obtained has extremely few crystal defects. The present invention was completed by finding out that the number of particles per cm ² or less was obtained, and conducting research on the synthetic quartz glass crucible used here. This will be described in more detail below.

[0009]

The present invention relates to a method for producing an N-type silicon single crystal, in which the N-type silicon single crystal is pulled up by a crucible made of synthetic quartz glass.

The production of the N-type silicon single crystal according to the present invention involves pulling up the silicon single crystal from a crucible made of synthetic quartz glass, and the crucible made of synthetic quartz glass uses an alkoxysilane such as methyl silicate for ammonia. It is said that it is made of synthetic quartz glass obtained by so-called sol-gel in which it is hydrolyzed and polycondensed by using, and after drying, it is closed and vitrified. It is an amorphous material that is composed of aggregates.

The N-type silicon single crystal according to the present invention can be obtained by making synthetic quartz crucible into fine silica particles by flame hydrolysis of silicon tetrachloride in an oxyhydrogen flame, and melting the fine silica particles from quartz glass. Quartz glass has an OH group content of 1,000 ppm
Because of the above, the viscosity at low temperature is low, and it has the disadvantages of being deformed and foamed at a high temperature in vacuum, which cannot be used in the present invention, and even when the above-mentioned sol-gel is used, this silica is a gel. If so, since the pores are small and will be closed at a low temperature and will contain gas and water, degassing and dehydration will be carried out by crystallization. Is mixed, so it is not good. However, if this silica is colloidal silica, it has large pores and can be easily degassed and dehydrated by heating, so it does not require crystallization and does not contain impurities. If the alkoxysilane as a raw material is sufficiently purified, the amount of impurities contained in the synthetic quartz glass crucible is 100 ppb or less for Al and Fe, and 50 for Ni and Cr.
ppb or less, B, P can be 10 ppb or less,
Furthermore, the advantage that the viscosity value at 1,400 ° C. can be 10 ¹⁰ poise or more is given.

The synthetic quartz glass crucible used in the present invention is prepared by supplying synthetic quartz glass powder, which is a non-sintered colloidal silica sintered body obtained by the sol-gel method, into a molding die. It may be manufactured by forming a powder layer in the mold and melting it by arc discharge to form a transparent layer made of synthetic quartz glass in the mold.

In the production of the N-type silicon single crystal according to the present invention, high purity polycrystal silicon is charged into the synthetic quartz glass crucible thus produced, and the crucible is melted by external heating. This may be carried out by a conventionally known method of immersing an N-type silicon seed crystal in this melt and pulling it up. According to this method, the synthetic quartz glass forming this synthetic quartz glass crucible has 1,400 Since the viscosity value at 10 ° C is 10 ¹⁰ poise or more, it is not deformed during this process, and the silicon single crystal can be easily pulled up, and in this case there is little melting loss. Therefore, the N-type silicon single crystal can be manufactured with a good yield, and further, the amount of metallic impurities contained in the synthetic quartz glass is very small as described above. Slicing the N-type silicon single crystal obtained by further wafer obtained through a heat treatment process - advantages are given that the minute defects is 3 / cm ² or less.

[0014]

EXAMPLES Next, examples of the present invention and comparative examples will be given. Example 1) Production of crucible made of synthetic quartz glass In a reactor in which the inner surface of a 5 liter SUS round continuous flask was coated with tetrafluoroethylene resin, 27 liters / hour of ammonia water and 24.5 liters / hour of methyl silicate were placed. Was added dropwise to form colloidal silica, and the silica was dehydrated with a centrifugal dehydrator and then washed with ultrapure water four times.

Then, this silica was put in a quartz crucible and heated from room temperature in an electric furnace to 300 ° C. for 3 hours, 800 ° C. for 3 hours, 1,000 ° C. for 3 hours, and the temperature rising time to each temperature was 0.
After heating in air for 5 or 4 or 2 hours, put it in a carbon mold and warm it to room temperature under reduced pressure for 1,20
The temperature was raised to 0 ° C. for 2 hours, 1,500 ° C. for 3 hours, 1,750 ° C. for 1 hour, and the heating time to each temperature was set to 2, 2 and 2 hours to obtain synthetic quartz glass. After washing with HF for 1 hour, drying, crushing with a jaw crusher and a desk mill, sieving to prepare 45-60 mesh, acid-washing with 20 wt. HCl, and flotation with pine oil, 5 wt. It was washed with HF for 15 minutes, heat-treated at 1,050 ° C, and subjected to a magnetic separator to obtain synthetic quartz glass powder.

Next, this synthetic quartz glass powder is fed into a rotating molding die to form a powder layer having a thickness of 14 mm.
It is melted from the inside by electric discharge, and after 15 minutes, synthetic quartz glass is further fed into this mold to form a transparent layer with a thickness of 1 mm on the inner surface to form a crucible. A crucible made of synthetic quartz glass was made to have the same height, and the analysis results of each metal in this crucible are as shown in Table 2.

2) Production of Silicon Single Crystal 20 kg of high-purity polycrystalline silicon as a raw material for pulling a silicon single crystal was charged into an 18-inch synthetic quartz glass crucible obtained as described above, and an argon gas atmosphere was introduced. After melting the polycrystalline recon under normal pressure, 20 mg of fine-grained antimony was added and left for 30 minutes. Then, the crucible and the seed crystal were rotated in opposite directions, and the seed crystal was brought into contact with the melt of the polycrystalline recon to start pulling the silicon single crystal.

Then, when the silicon single crystal reaches the target diameter, the pulling rate is 2.0 mm / min and the argon gas flow rate is
50 l / min, the argon gas pressure was set to 20 mmHg, and the silicon single crystal rod grown in this way was removed.
When sliced to a thickness of 0.5 mm and finished to a mirror surface to prepare a silicon wafer having a diameter of 6 inches and examining the metal components of this wafer, the results shown in Table 2 were obtained.

The wafer was held in a nitrogen gas atmosphere at 650 ° C. for 30 minutes and 1,350 ° C. for 15 hours and then cooled to room temperature, and the oxide film on the wafer surface was removed with hydrofluoric acid. When etching was performed for 15 minutes in an etching solution (HF-C _r O ₃ -H ₂ O solution) while stirring, and microscopic defects were observed with an optical microscope, it was found to be 0.03 / cm ² at the best and 2.5 / at the worst. It was cm ² , and the average was 1.2 pieces / cm ² .

Comparative Example An N-type silicon single crystal was prepared in the same manner as in the example except that the synthetic quartz glass crucible used in the example was replaced with a natural quartz glass crucible having a metal content shown in Table 2. Was carried out, and a silicon wafer having a diameter of 6 inches was sliced to examine the metal components of this wafer. The results are shown in Table 2. The microdefects on this wafer were the same as those in the example. According to the method, this is 4.8 pieces / cm ² at the best and 8.5 pieces / cm at the worst.
² , which was 5.2 pieces / cm ² on average.

[0021]

[Table 2]

[0022]

The present invention relates to a method for producing an N-type silicon single crystal, which is characterized by pulling a silicon single crystal from a synthetic quartz glass crucible as described above. Quartz glass crucibles are amorphous colloidal silica sinters obtained by hydrolytic polycondensation of alkoxysilanes.The surface and synthetic layers have impurity contents of Al, Fe of 100 ppm or less, Ni and Cr of 50 pp.
Below b, B and P are supposed to be below 10 ppb.
According to this, the N-type silicon single crystal can be pulled with good yield, and a wafer obtained from this single crystal can be obtained.
It is possible to provide the advantage that the number of micro defects of 3 can be 3 / cm ² or less.

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[Procedure amendment]

[Submission date] November 22, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

In the production of the N-type silicon single crystal according to the present invention, high purity polycrystal silicon is charged into the synthetic quartz glass crucible thus produced, and the crucible is melted by external heating. the immersing the N-type silicon seed crystal into the melt, which may be performed by a conventionally known method of Ru pulling up, but this according Invite synthetic quartz glass forming the synthetic quartz glass crucible Has a viscosity value of 10 ¹⁰ poise or more at 1,400 ° C., so that it does not deform during this step, and the silicon single crystal can be easily pulled up. In this case, N-type silicon single crystal can be produced with good yield because of little melting loss, and the amount of metal impurities contained in this synthetic quartz glass is very small as described above. Gives an advantage that the wafer obtained by slicing the N-type silicon single crystal thus obtained and further subjected to the heat treatment step has 3 or less fine defects / cm ² .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

Next, this silica was put into a quartz crucible and heated from room temperature in an electric furnace to 300 ° C. for 3 hours and 800 ° C. for 3 hours.
Time, 1,000 ° C. for 3 hours, heating time to each temperature for 0.5, 4 and 2 hours, respectively, and after heating in the air for heating, put this in a carbon mold and raise the temperature from room temperature under reduced pressure. Heat to 1,200 ° C for 2 hours, 1,500 ° C for 3 hours, 1,
750 ° C. for 1 hour, heating time to each temperature 2,
The temperature was raised for 2 to 2 hours to form synthetic quartz glass by heating and the obtained ingot was washed with 20% by weight of HF for 1 hour,
After drying, crushing with a jaw crusher and a desk mill, sieving to prepare 45 to 60 mesh, acid washing with 20 % by weight HCl, floating separation with pine oil, and washing with 5% by weight HF for 15 minutes, Heat treatment was carried out at 1,050 ° C., and a synthetic quartz glass powder was obtained by applying a magnetic separator.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

2) Manufacture of silicon single crystal 20 kg of high-purity polycrystalline silicon as a raw material for pulling a silicon single crystal was charged into an 18-inch synthetic quartz glass crucible obtained as described above, and an argon gas atmosphere was introduced. After melting the polycrystalline divorced atmospheric pressure of, antimony fine granular were left 20mg added 30 minutes. Thereafter, while rotating in the opposite direction to the crucible and the seed crystal from each other by contacting a seed crystal with a melt of polycrystalline divorced by starting the pulling of the silicon single crystal.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

Then, when the silicon single crystal reached the target diameter, the pulling rate was set to 2.0 mm / min, the argon gas flow rate was set to 50 l / min, and the argon gas pressure was set to 20 mmHg. Remove the crystal bar, which was sliced into 0.5mm thick, mirror-finished to create the silicon down wafer 6 inches in diameter, was examined metal components of the wafer, the results of as shown in Table 2 Was obtained.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

Comparative Example An N-type silicon single crystal was prepared in the same manner as in the example except that the synthetic quartz glass crucible used in the example was replaced with a natural quartz glass crucible having a metal content shown in Table 2. performs pulling, was investigated metal components of the wafer by slicing a silicon down <br/> wafer now a 6 inch diameter, which is as shown in Table 2, implementing the micro-defects of this wafer When examined in the same manner as in the example, the best value was 4.8 / cm ² , and the worst value was 8.
The number was 5 / cm ² , and the average was 5.2 / cm ² .

[Procedure Amendment 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

[0022]

The present invention relates to a method for producing an N-type silicon single crystal, which is characterized by pulling a silicon single crystal from a synthetic quartz glass crucible as described above. quartz glass crucible at the sintering of the amorphous colloidal silica obtained by hydrolytic polycondensation of an alkoxysilane, the impurity content in the surface and synthetic layer is Al, Fe is 100Pp b less, N
i and Cr are set to 50 ppb or less and B and P are set to 10 ppb or less. According to this, the N-type silicon single crystal can be pulled with high yield, and a wafer obtained from this single crystal. It is possible to provide the advantage that the number of micro defects of 3 can be 3 / cm ² or less.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Watanabe, Inventor Hiroyuki Watanabe 1 at 28, Nishi-Fukushima, Chugiki-mura, Nakakubiki-gun, Niigata Prefecture Synthetic Technology Laboratory, Shin-Etsu Chemical Co., Ltd. (72) Masatoshi Takita, Kubiki-mura, Nakakubiki-gun, Niigata Prefecture 1 at 28 Fukushima Nishi Fukushima Shin-Etsu Chemical Co., Ltd. Synthetic Technology Laboratory (72) Inventor Mitsuo Matsumura 2-13-60 Kitafu, Takefu-shi, Fukui Prefecture Shin-Etsuishi Hideshi Takefu Factory (72) Inventor Hiroshi Matsui 2-13-60 Kitafu, Takefu City, Fukui Prefecture Shin-Etsu Ishihide Takefu Factory Co., Ltd. (72) Inventor Shinichi Furuse 150 Odaira, Odakura, Saigo-mura, Nishishirakawa-gun, Fukushima Shin-Etsu Semiconductor Co., Ltd. Shirakawa Factory

Claims (3)

[Claims] 1. A method for producing an N-type silicon single crystal, which comprises pulling up a silicon single crystal from a synthetic quartz glass crucible. 2. The defect density of the silicon wafer is 3 defects / cm ^2.
The method for producing an N-type silicon single crystal according to claim 1, which is as follows. 3. A synthetic quartz glass crucible is a sintered product of amorphous colloidal silica obtained by hydrolytic polycondensation of an alkoxysilane. Impurity contents of Al and Fe on the surface and in the synthetic layer are 100 ppb or less. The method for producing an N-type silicon single crystal according to claim 1, wherein each of Ni, Cr and Cr is 50 ppb or less and B and P are 10 ppb or less.