JPS61242984A - Crucible for pulling up silicon single crystal - Google Patents

Abstract

PURPOSE:To obtain a crucible having high shape stability, by using a crucible having inner surface layer having high OH concentration and the outer part of the crucible having a specific low OH concentration, thereby moderately controlling the reaction between the molten silicon and the crucible. CONSTITUTION:In the crucible for the pulling-up of a silicon single crystal, the OH-group content in the zone from the inner surface to the depth of >=0.2mm (preferably 0.6-1.5mm thick) is controlled to a high level, i.e. 60-195ppm, preferably 80-170ppm. The zone outside of the above zone and having a thickness of >=0.5mm is adjusted to a low-OH concentration, i.e. having an OH concentration lower than the average concentration in the inner surface layer of 0.3mm thick by >=20ppm. Since SiO2 is soluble easily by the use of the above crucible, the motion of the molten liquid becomes gentle, the desired oxygen concentration can be achieved, and the operation condition can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a crucible used in producing a single crystal by pulling molten silicon.

(Prior Art and Problems) Methods for pulling single crystals for mass production of silicon wafers can be roughly divided into the FZ (a-ting zone) method and the CZ (Czochralski) method. The CZ method involves pulling a single crystal from molten silicon in a quartz glass crucible while solidifying it.
melts into the molten silicon, and as a result, oxygen is included in the single crystal (ref, W, Zuleh
ner and D, Huber ;rcrysta
lsJ Vol, 8”Czockralski-Gr
own 5ilic.

n″p, I Springer-Verlag (19
82) ) *This oxygen is not something to be avoided as an impurity, but plays an important role such as increasing the heat resistance of the wafer. Therefore, when manufacturing single crystals using the C2 method, it is widely practiced to control so-called crystal pulling conditions such as the crucible rotation speed, crystal rotation speed, and atmosphere so that the required concentration of oxygen is introduced into the silicon wafer. It is said (
Id, Zulehner et al, supra)
.

On the other hand, the first characteristic required of a quartz glass crucible is heat resistance, since its operating temperature reaches approximately 1500°C. In quartz glass for the semiconductor industry, the heat resistance can be approximated by a one-to-one correspondence to the OH group concentration in the glass, so creating a crucible with a low OH group content has been a challenge for crucible manufacturers.

Such a crucible with a low OH group content has a high viscosity,
It has good shape stability and slow diffusion of impurities, so it is excellent in keeping the molten silicon in the crucible clean. However, even if the optimum operating conditions are set, high temperatures are required to maintain them. It has the disadvantage that it requires precision control and is extremely difficult to use repeatedly (so-called multiplexing).

On the other hand, if a crucible with a high OH group content is used,
The disadvantage is that high-quality single crystals cannot be obtained due to the diffusion and penetration of impurities from the heater and graphite susceptor.
Therefore, the use of such a crucible with a high OH group content is a past technique in which crucibles with a low OH group content were not available.

(Objective and Structure of the Invention) As a result of various studies to solve the conventional problems with crucibles for pulling silicon single crystals, the inventor of the present invention has found that the concentration of OH groups in the inner surface layer of the crucible is increased and the concentration of OH groups is lowered in the outer surface layer. , O
The present invention was completed based on the finding that when a crucible with a distribution of H group concentration is used, the reaction between molten silicon and the crucible (SiO2) is moderate and easy to control, and shape stability can be obtained.

That is, the present invention provides a high OH concentration region having an OH group content of 60 pp or more and having a thickness of 0.2 layers or more in contact with the inner surface;
A pulled single crystal having a structure in which a low OH concentration region having an OH group content of 20 pp or more less than the average concentration in the inner surface layer with a thickness of 0.3 i + m is present in the part of the 0.5 layer or more thick that does not touch the inner surface. As described above, the crucible of the present invention, which is related to a crucible for use in The reaction with □) can be appropriately controlled, and excellent shape stability can be maintained at the operating temperature of around 1460°C.

Therefore, in the present invention, the range 0.21 mm or more from the inner surface of the crucible is defined as a high concentration region with an OH group content of 60 ppm or more, preferably 60 to 170 PP■, and the optimum thickness of the region is 0.8 mm. It takes ~1.5■■.

Under these conditions, the OH group distribution curve O shown in Figure 1 is A.
It means not passing through part, preferably not passing through part B or C. To explain this specifically with reference to FIG. 1, the following 0 distribution curve 01 is for a normal low OH group concentration crucible, and is for an electric melting crucible called a so-called translucent crucible. In this case, the zero distribution curve 0, which passes through region A and is different from the crucible of the present invention because the inner surface also has a low OH group concentration, is for a transparent natural silica glass crucible. Although it is within the above-mentioned optimum range, it is outside the scope of the present invention because it does not have a low OH region, which is another condition of the present invention that will be described later.

Distribution curve 03 is an example of the present invention, and the most preferred crucible, 0 distribution curve O, is similar to the optimal example of 03, but
Since the thickness of the inner surface layer of 60PP- or more is less than 0.2■■, the effect of the present invention is not sufficient and is not satisfactory.

Simultaneously with the above conditions, in the present invention, a layer with less OH groups by 20 pp or more than the average OH group concentration of 0.3 mm of the inner surface layer,
It is necessary to be outside the high concentration region, and this region may be in contact with the outer surface of the crucible.

As shown in Figure 2, the average OH group concentration C1 of the inner surface layer 0.3 layer and the OH group concentration C2 of the layer 20pp-less than this.
Let the distances from the inner surface to points A and B where and intersect with the OH distribution curve O be XA and X8, respectively.

In the crucible of the present invention, xB-x1≧0.5 (m■) and the chin is the second condition. In this case, if there is no intersection B and all points outside A are lower than C2, point B can be considered to be on the outer surface. Note that C2 is 40pp higher than C.
It is preferable that it be smaller than expected.

It is desirable that XB-XA is 1.5 dragons or more.

A configuration that satisfies the above two conditions occupies 1/4 or more of the inner surface of the entire crucible or 1/3 or more of the inner surface that comes into contact with molten silicon during silicon melting (usually 70% of the inner surface
5% is in contact with molten silicon) is also a necessary condition for the present invention.

As a method for providing a region with a high concentration of OH groups inside the crucible, (i) welding a quartz glass plate 2 containing many OH groups to the inside of a quartz glass crucible 1 molded in a rotary mold (lining), (Fig. 3) ), (ii) When producing a crucible 1 by molding powder in a rotary mold 3 and melting the powder layer with an electric arc, a quartz glass powder 4 containing many OH groups is molded inside to form a double powder. (double powder molding) (Figure 4), (iii) When electrically melting the powder layer in the rotary mold, it contains moisture and maintains the molten state for a long time in the atmosphere (normal atmosphere). However, methods (i) and (ii) are not practical because the manufacturing process is complicated and quartz glass powder is more expensive than quartz powder.

The present inventor conducted an experiment to change the OH group content of the inner layer by changing the conventional melting method using the rotary mold method, and found that the method (iii) results in unexpected results when melting for a long time in normal atmosphere. It was found that the OH group content of the inner layer increases. If the melting time is extended using the conventional method, the crucible will become too thick, but the thickness can be controlled to a predetermined value by changing the cooling conditions.

The crucible of the present invention obtained by the above method has an OH group content of 30 ppm in the conventional crucible, whereas in the optimal example, the OH group content is about 60 ppm on the dough and 110 ppm on the inner surface. The following effects can be mentioned.

(Effects of the invention) (1) Conventionally, 3102 (glass) was difficult to melt into molten silicon, and therefore operating conditions were set such that relatively fast convection occurred.Using the crucible of the present invention, S
Since i 02 (glass) is easily melted, the movement of the molten metal is gentle, and once a predetermined oxygen concentration is reached, the operating conditions are also likely to be stable.

(2) As a result, the number of times the crucible can be used repeatedly (so-called multi-pulling) using the reduced pressure CZ method was limited to 2 to 3 times in the past, but with the present invention it is 6 to 8 times, which reduces the operating rate. The result was a significant increase. At the same time, quality uniformity improved.

First, a crucible according to the present invention and a crucible according to a conventional method were prototyped, and the OH group concentration distribution in the direction perpendicular to the inner surface was compared. FIG. 5 shows the results, and all J crucibles had a diameter of 350 mm.

(2) is a crucible made by the conventional method of molding quartz powder in a rotary mold and heating it from the inside with an arc, and (a) and (2) are crucibles according to the present invention. That is, these methods are respectively (ii) double powder molding, (ifi) long-term melting, and (i) lining.

In the conventional crucible (2), OH groups are distributed almost uniformly at 30 to 40 ppm throughout the fabric and inner layer of the crucible.
■~■ are distributions with extremely high concentration regions reaching 190 ppm on the inner surface, ■ are 60~70 ppm.
The fabric was in the pm range, and in this case, the average value of the 0.3 mm inner surface layer was 110 ppm. ■ The lining method takes a lot of man-hours and is not suitable for mass production, but what percentage of the inner surface is OH?
Since this is a good sample for determining whether it is necessary to have a base distribution structure, in addition to sample (2) with a lining rate of 30%, sample 5 with a lining rate of 15% was prototyped. Furthermore, we added sample 8 of double powder molding with an inner layer of synthetic quartz glass and sample 7 of a fully transparent quartz glass crucible made with glasswork, and examined the actual use of these crucibles to improve the number of multiple pulls and ease of use. compared. The table below shows the results.

From the above results, it is clear that No. 3, the long-time melting type OH-based fabric, is the most desirable. No again,
The inner layer region with higher OH group concentration than No. 4 and No. 5 is No. 25.
It is also estimated that it will not be effective unless it exceeds %. No,
In example 7, although the OH group content on the inner surface was appropriate at 170 ppm, the result was poor because there was no fabric in the low OH group content area, so the molten silicon was contaminated in a short time. It is presumed that it will become unusable after that.

[Brief explanation of the drawing]

Figures 1 and tsz are diagrams showing the distribution of the amount of OH groups in the depth direction from the inner surface of the crucible, Figures 3 and 4 are illustrations of crucible manufacturing, and Figure 5 is a diagram showing various types of crucibles. It is a curve diagram showing the OH group content distribution in the depth direction from the inner surface. 1... Crucible, 2... Glass plate. Patent applicant Shin-Etsu Quartz Co., Ltd., TL) First cause J111 OH group (ρpm) Procedural amendment (own ship June 7, 1985 Patent application No. 84218 2, 1985, title of invention For silicon single crystal pulling Crucible 3, Relationship with the case of the person making the amendment Patent applicant name Shin-Etsu Quartz Co., Ltd. 46 Agent 5, Specification subject to amendment 6, Contents of amendment 1) r60pph on page 4, line 11 of the specification
ppg1 or more” Correct. ``Therefore, the molten silicon in the crucible and the melt in the crucible'' on page 4, line 18 is corrected to ``therefore, the melt in the crucible.'' 3) ``1.'' on page 5, line 7 of the specification. 5■ Change “I’ll take it” to “1
The distance is 511 m.'' 4) Amend "C2 is from C" on page 7, line 7 of the specification to r (. is from C8.) 5) Amend "atmosphere containing moisture" on page 8, line 9 of the specification to "
"An atmosphere containing moisture". 6) Amend "to be together" on page 9, line 13 of the specification to read "as well as". Correct "6 and" in the third line of page 11 of the side number to "6 and". The above procedural amendment (Shirogumi February 1, 1985, 1°) Indication of the 1985 Patent Application No. 84218 3, Relationship with the person making the amendment Name of patent applicant Shin-Etsu Quartz Co., Ltd. Name Shin-Etsu Semiconductor Co., Ltd. 4. Agent address: 4-9-61, Nihonbashi Honmachi, Chuo-ku, Tokyo 103
．． 2.12 6. Contents of amendment 1) The lining rate is 15% for r on page 11, line 1 to page 13, last line of the specification as per the attached sheet. 2) Add Figure 6 of the drawing as attached. (Attachment) A sample ■ with a lining rate of 15% was prototyped. Furthermore, we added a sample of double powder molding with an inner layer of synthetic quartz glass■ and a sample of a fully transparent quartz glass crucible made with glasswork■, and examined the actual use of these crucibles to improve the number of multiple pulls and ease of use. compared. The experimental method will be explained below. For this experiment, various types of quartz crucibles were prototyped with a diameter of 25 mm.
A cs x height 203 was set as shown in Fig. 6, and about 20 kg of high-purity polycrystalline silicon was filled and melted.
Argon gas was introduced from the inlet 5 at a flow rate of 30,417 w1n, and a silicon single crystal 7 having a diameter of 110 .phi. was pulled while maintaining the pressure in the pulling chamber 6 at 101b. The other parts in FIG. 6 are made up of a pulling shaft 9 that rotates upward and rises via a seed crystal 8 at the upper end of the silicon single crystal 7 to be pulled, a quartz crucible, and a carbon material inscribed therein. The crucible protector 10 heats and melts the high-purity polycrystalline silicon block filled in the quartz crucible 1 using a heater 11 surrounding the protector, and after melting, the heater 11 surrounding the protector , AC or DC power supply and control equipment (not shown) to provide adequate heating energy.
is included. 12 is a high-purity silicon melt;
Reference numeral 3 denotes an outlet from the drawing chamber 6 for the inflowing gas. When the single silicon 7 is pulled up from the silicon melt 12, it is necessary to appropriately control the rotation speed of the seed crystal 8 and the rotation speed of the quartz crucible 1 depending on the crucible used.
When a conventional quartz crucible is used, the rotating directions are opposite to each other, and the first seed crystal is 15 rpm, and the quartz crucible is 2 rpm. However, when using long-term melting products or lined products. Alternatively, when a double molded product is used, the rotational speed of the seed crystal can be reduced to 10 to 5 rpm, and as a result, the stirring of the silicon melt becomes gentle, resulting in deterioration of the inner wall of the crucible or damage to the crucible wall that occurs as a result. It is possible to significantly prevent single crystal parts from being bent due to contact of quartz particles peeled off from the silicon single crystal growth interface. In the process of pulling a silicon single crystal, the silicon is melted in a quartz crucible 1 in order to control the concentration of phosphorus or boron, which is intentionally added to the silicon single crystal to control the conductivity type and resistivity, within a certain range. It is rare that the entire amount of silicon is turned into a single crystal in one lifting process, and after a certain amount, for example, half of the total amount of silicon, or 10 kg, is pulled up, it is
0 kg is added and the second lifting process is performed. Theoretically, it is preferable that the pulling process be performed infinitely, but as the number of pulling processes increases, impurities remaining in the silicon melt accumulate, so it is believed that the maximum number of drawing processes is 10 times. The results of these experiments are shown in the table below. From the above results, the long-melting type OH of sample ■
The base fabric is clearly the most desirable. It is also estimated that the inner layer region having a higher OH group concentration than Samples ① and ② must be 25% or more to be effective. Even though the OH groups on the inner surface of sample (■) are appropriate at 17OPP (■), the reason for the poor results is that there is no fabric in the low OH group content region. It is estimated that the molten silicon becomes contaminated within a short time and becomes unusable thereafter. 4. Brief explanation of the drawings Figures 1 and 2 are diagrams showing the distribution of OH group content in the depth direction from the inner surface of the crucible, Figures 3 and 4 are illustrations for explaining the production of the crucible, Figure 5 shows the distribution of OH group content in the depth direction from the inner surface of various types of crucibles.
FIG. ii and FIG. 6 are cross-sectional views of a single crystal pulling apparatus using the CZ method. DESCRIPTION OF SYMBOLS 1... Crucible, 2... Glass plate, 3... Rotating mold, 4... Glass powder with high OH group content, 5... Inlet, 6... Pulling chamber, 7. ... Single crystal, 8... Seed crystal, 9... Pulling shaft, 10... Crucible protector, 11 River heater, 12...
Molten body, 13...exit. Procedural amendment (self-imposed patent application No. 84218 of 1985 2, title of invention: Crucible for pulling silicon single crystals 3, relationship with the case of the person making the amendments) Name of patent applicant: Shin-Etsu Quartz Co., Ltd. Jjiang Shin-Etsu Semiconductor Co., Ltd. 4 , Agent 6, Contents of amendment 1) Amend the entire specification as per the attached amended specification. 2) Replace No. 1 with Fig. 1 of the attached sheet - Amended specification 1, title of invention: crucible 2 for pulling silicon single crystals, claim 1, a crucible with a thickness of 0.2 s + m or more in contact with the inner surface. , the OH group content is 60 ppm or more. ”Artificial high OH
a concentration region and a low OH concentration region where the OH group content is 20 ppm or more lower than the average concentration in the inner surface layer with a thickness of 0 to 3 m in a portion of 0.5 layers or more thick that does not contact the inner surface. A crucible for pulling single crystals. 2. The unit according to claim 1, wherein the structure occupies one quarter or more of the inner surface of the entire crucible, or one third or more of the inner surface that comes into contact with the melt when melting the raw material. Crucible for crystal pulling. 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a crucible used when producing a single crystal by pulling molten silicon. (Prior Art and Problems) Methods for pulling single crystals for mass-producing silicon wafers can be roughly divided into the FZ (blooting zone) method and the CZ (Czochralski) method. The CZ method involves pulling a single crystal from molten silicon in a quartz glass crucible while solidifying it. At this time, 1-quartz glass (SiO2) melts into the molten silicon, and as a result, oxygen is included in the single crystal. (ref
%W, Zulehner and D, Huber
;rcrlstalsJ Vol, 8'''Czockr
a1gki-Grown 5ilicon”p+I
Springer-Verlag (1182)) *
This oxygen is not an impurity that should be avoided; it plays an important role, such as increasing the heat resistance of the wafer. Therefore, when manufacturing single crystals using the CZ method, it is widely practiced to control so-called crystal pulling conditions such as the crucible rotation speed, crystal rotation speed, and atmosphere so that oxygen at the required concentration is introduced into the silicon wafer. (L Zule)
hner et al, supra). On the other hand, the first characteristic required of a quartz glass crucible is heat resistance, since its operating temperature reaches approximately 1500°C. In quartz glass for the semiconductor industry, heat resistance can be approximated by corresponding to the OH group concentration in the glass on a ratio of 1 to 1, so creating a crucible with a low OH group content has been a challenge for crucible manufacturers. Such a crucible with a low OH group content has a high viscosity,
It has good shape stability and slow diffusion of impurities, so it is excellent in keeping the molten silicon in the crucible clean. However, even if the optimum operating conditions are set, high temperatures are required to maintain them. It has the disadvantage that it requires precision control and is extremely difficult to use repeatedly (so-called multiplexing). On the other hand, if a crucible with a high OH group content is used,
The disadvantage is that high-quality single crystals cannot be obtained due to the diffusion and penetration of impurities from the heater and graphite susceptor.
Therefore, the use of such a crucible with a high OH group content is a past technique in which crucibles with a low OH group content were not available. (Objective and Structure of the Invention) The present inventors have conducted various studies to solve the conventional problems with crucibles for pulling silicon single crystals, and as a result, the inventors have developed a method to increase the OH group concentration in the inner surface layer of the crucible. It was discovered that by using a crucible with a lower outside surface and a distribution of OH group concentration, the reaction between molten silicon and the crucible (SiO2) is moderate and easy to control, and shape stability can be obtained. completed. In other words, the present invention has a high OH concentration region having an OH group content of 60 ppm or more and 195 ppm or less, which is in contact with the inner surface and has a thickness of 0.2 mm or more, and a 0.5 mm thick intestinal layer that is not in contact with the inner surface. The present invention relates to a crucible for pulling a single crystal having a structure in which the above portion has a low OH concentration region where the OH group content is 20 ppm or more lower than the average concentration in the inner layer with a thickness of 0.3 mm. As mentioned above, by providing a region with a high concentration of OR groups inside the crucible, the crucible makes it easy to moderately control the reaction between the molten silicon in the crucible and the crucible wall (S s O2), and also reduces the operating temperature. is 1
It is designed to maintain excellent shape stability at around 460°C. Therefore, in the present invention, 0.2 m11 from the inner surface of the crucible
The above range is OH group content of 60 ppm or more and 195 ppm.
■Hereafter, the high concentration region is preferably 60 to 170 pp, and the optimal thickness of the region is 0.8 to ! , 5 servings. Under these conditions, the OH group distribution curve 0 shown in Figure 1 is A.
It means not passing through part, preferably not passing through part B or C. To explain this specifically with reference to FIG. 1, the following 0 distribution curve 01 is for a normal low OH group concentration crucible, and is for an electric melting crucible called a so-called translucent crucible. In this case, the zero distribution curve 0, which passes through region A and is different from the crucible of the present invention because the inner surface also has a low OH group concentration, is for a transparent natural silica glass crucible. Although it is within the above-mentioned optimum range, it is outside the scope of the present invention because it does not have a low OH region, which is another condition of the present invention that will be described later. Mu I & t I + b Zeng / Nj ↓ Shimada Koga - 11 Masa is also a favorable turbo, 0 distribution curve O is similar to the optimal example of 03, but when the thickness of the interior layer of 60 PP■ or more is 0.21 fat Because of the following, the effects of the present invention are not sufficient and are not satisfactory. Simultaneously with the above conditions, in the present invention, the interior layer 0. It is necessary that a layer containing 20 pp- or more less OH groups than the average OH group concentration of :b+m is located outside the high concentration region, and this region may be in contact with the outer surface of the crucible. As shown in Figure 2, the average OH group concentration C1 of the interior layer 0.3 mm and the OH group concentration C2 of the layer 20 pp less than this.
Let the distances from the inner surface to points A and B, where and intersect with the OB distribution dbtlQ, be XA and X, respectively. In the crucible of the present invention, the second condition is XB-XA≧0.5 (■S) and the chin. In this case, if there is no intersection B and all points outside A are lower than C2, point B can be considered to be on the outer surface. Note that C2 is 40pp higher than C1.
Preferably smaller than a garden. It is desirable that xB-xA is 1.5 layers or more. A configuration that satisfies the above two conditions occupies 1/4 or more of the inner surface of the entire crucible or 1/3 or more of the inner surface that comes into contact with molten silicon during silicon melting (usually 70% of the inner surface
5% is in contact with molten silicon) is also a necessary condition for the present invention. A method of providing a high concentration region of OH groups inside the crucible is as follows: (i) Welding a quartz glass plate 2 with a large number of OH groups (01) to the inside of a quartz glass crucible 1 molded in a rotary mold.
(lining), (Figure 3), (ii) When manufacturing the crucible 1 by molding the powder in the rotary mold 3 and melting the powder layer with an electric arc, quartz glass powder with a large number of OH groups is added to the inside. 4 to form a double powder layer (double powder molding) (Figure 4), (iii) When electrically melting the powder layer in the rotary mold, an atmosphere containing moisture (normal atmosphere) is used. Remains molten for a long time. However, methods (i) and (ii) are not practical because the manufacturing process is complicated and quartz glass powder is more expensive than quartz powder. The present inventors conducted an experiment to change the OH group content of the inner layer by changing the conventional melting method using the rotary mold method. In particular, it was found that the OH group content of the inner layer increased. If the melting time is extended using the conventional method, the crucible will become too thick, but the thickness can be controlled to a predetermined value by changing the cooling conditions. The crucible of the present invention obtained by the above method has an OH group content of about 60 ppm on the dough and 110 ppm on the inner surface in the optimal example, whereas a conventional crucible has an OH group content of 30 ppm. The following effects can be mentioned. (Effects of the Invention) (1) Conventionally, Si02 (glass) was difficult to melt into molten silicon, and therefore operating conditions were set such that relatively fast convection occurred.Using the crucible of the present invention, S i02 ( Glass) is easily melted. The movement of the molten metal is gentle, allowing the specified oxygen concentration to be achieved and the operating conditions to be stable. (2) As a result, the number of times the crucible can be used repeatedly (so-called multi-pulling) using the reduced pressure CZ method was limited to 2 to 3 times in the past, but with the present invention it is 6 to 8 times, which reduces the operating rate. The result was a significant increase. At the same time, quality uniformity improved. Next, a crucible according to the present invention and a crucible according to a conventional method were prototyped, and the OH group concentration distribution in the direction perpendicular to the inner surface was compared. FIG. 5 shows the results, and all crucibles had a diameter of 25 cm and a height of 20 cm. (2) is a crucible made by the conventional method of molding quartz powder in a rotary mold and heating it from the inside with an arc, and Q, (2) and (2) are crucibles according to the present invention. That is, these methods are respectively (ii) double powder molding, (iii) long-term melting, and (i) lining. In the conventional crucible (2), the OH groups are distributed almost uniformly at 30 to 40 pp (2) throughout the fabric and inner layer of the crucible, but 1
．． ■～(This is a distribution with an extremely high concentration area reaching up to 190 pa■ on the 3xt inner surface.
The area of 7opp■ became the dough, but in this case, 0.3
The average value of the inner surface layer of m■ was 110 ppm. The lining method (①) requires a lot of man-hours and is not suitable for mass production, but it is a good sample for knowing what percentage of the inner surface needs to have an OH group distribution structure, so in addition to the sample (①) with a lining ratio of 30%. A sample (■) with a lining rate of 15% was produced. Furthermore, we added a sample of double powder molding with an inner layer of synthetic quartz glass■ and a sample of a fully transparent quartz glass crucible made with glasswork■, and examined the actual use of these crucibles to improve the number of multiple pulls and ease of use. compared. The experimental method will be explained below. Various quartz crucibles with a diameter of 25 cm were prototyped for this experiment.
m x height 20c+w is set as shown in Fig. 6, about 20 kg of high-purity polycrystalline silicon is filled and melted, argon gas is introduced from the inlet 5 at a flow rate of 30 Jl/win, and the inside of the pulling chamber 6 is diameter 1 while keeping the pressure at 10mb.
A silicon single crystal 7 with a diameter of 10 mm was pulled. The other parts in FIG. 6 are made up of a pulling shaft 9 that rotates upward and rises via a seed crystal 8 at the upper end of the silicon single crystal 7 to be pulled, a quartz crucible, and a carbon material inscribed therein. The crucible protector 10 heats and melts the high-purity polycrystalline silicon block filled in the quartz crucible 1 using a heater 11 surrounding the protector, and after melting, the heater 11 surrounding the protector , AC or DC power supply and control equipment (not shown) to provide adequate heating energy.
is included. 12 is a high-purity silicon melt;
Reference numeral 3 denotes an outlet from the drawing chamber 6 for the inflowing gas. When the single crystal silicon 7 is pulled from the silicon melt 12, it is necessary to appropriately control the rotation speed of the seed crystal 8 and the rotation speed of the quartz crucible 1 depending on the crucible used.
When using a conventional quartz crucible, the directions of one rotation are opposite to each other, and the seed crystal is used at 15 rpm and the quartz crucible at 2 rpm. However, when using a long-time melting product, a lined product, or a double molded product, the rotation speed of the seed crystal can be reduced to 10 to 5 rpm.
As a result, the agitation of the silicon melt becomes gentle, and it is possible to significantly prevent single crystal disturbance due to deterioration of the inner wall of the crucible or contact of quartz pieces peeled off from the crucible wall to the silicon single crystal growth interface. In the process of pulling a silicon single crystal, the silicon is melted in a quartz crucible 1 in order to control the concentration of phosphorus or poron, which is intentionally added to control the conductivity type and resistivity, within a certain range. It is rare that the entire amount of silicon is turned into a single crystal in one pulling process, and after a certain amount, for example, half of the total amount of silicon, or 10 kg, has been pulled up, it is then pulled up again to a maximum of 1 kg.
0 kg is added and the second lifting stroke is performed. Theoretically, it is preferable that the pulling process be carried out infinitely, but as the number of pulling processes increases, impurities remaining in the silicon melt accumulate, so it is believed that the maximum number of pulling processes is 10 times. The results of these experiments are shown in the table below. From the above results, the long-melting type OH of sample ■
The base fabric is clearly the most desirable. It is also estimated that the inner layer region with a higher OH group concentration than Sample (2) and Sample (2) must be 25% or more to be effective. In sample ①, even though the OH group on the inner surface is 170 ppm, which is appropriate, the result is poor because there is no fabric in the low OH group content area, so the molten silicon becomes contaminated in a short time. It is presumed that the product will become unusable after that. , Brief description of the drawings Figures 1 and 2 are diagrams showing the distribution of OH group content in the depth direction from the inner surface of the crucible, Figures 3 and 4 are illustrations for explaining the production of the crucible, FIG. 5 is a curve diagram showing the OH group content distribution in the depth direction from the inner surface of various types of crucibles, and FIG. 6 is a sectional view of a single crystal pulling apparatus using the CZ method. 1. Fist/crucible, 2. e-glass plate. 3...Rotary mold, 4...Glass powder with high OH group content. 5...Entrance, 6.Fist/pulling chamber, 7...-Single crystal, 8...Seed crystal. 9. φ. Pulling shaft, 10... Crucible protector. 11... Heater, 12... Molten body, 13. Fist-exit.

Claims (1)

[Claims] 1. A high OH concentration region with an OH group content of 60 ppm or more that is in contact with the inner surface and has a thickness of 0.2 mm or more, and a region that is not in contact with the inner surface and has a thickness of 0.5 mm or more. A crucible for pulling single crystals having a structure having a low OH concentration region in which the OH group content is 20 ppm or more lower than the average concentration in the inner surface layer with a thickness of 0.3 mm. 2. The unit according to claim 1, wherein the structure occupies one quarter or more of the inner surface of the entire crucible, or one third or more of the inner surface that comes into contact with the melt when melting the raw material. Crucible for crystal pulling.