TWI568898B - Silicon single crystal manufacturing method - Google Patents

Description

矽Single crystal manufacturing method

The present invention relates to a method for producing a single crystal according to the Czochralski method (hereinafter referred to as CZ method), and more particularly to a method for filling a crucible material in a quartz crucible.

In recent years, most of the single crystals which are the raw materials for germanium wafers are manufactured according to the CZ method. The CZ method is a method in which seed crystals are immersed in the liquid surface of the crucible liquid contained in the quartz crucible, and the seed crystals are slowly pulled up, whereby the monocrystals having the same crystal orientation as the seed crystals are grown.

In recent years, as the diameter of the single crystal is increased, the bubbles are taken into the growing single crystal, and the problem of pinholes or poor rows in the single crystal becomes remarkable. It is considered that the gas is a gas such as argon (Ar) gas dissolved in the ruthenium melt or a gas such as ruthenium oxide (SiO) gas generated by the reaction of the quartz ruthenium and the ruthenium melt to form an inner surface of the quartz crucible. The defect is agglomerated at the starting point, whereby the bubble which is detached from the inner surface of the crucible floats in the crucible melt and is taken into the single crystal. The pinhole system is also called a spherical crystal defect (cavity defect) of an air bag, and most of the system has a size of 300 to 500 μm, but it is also a small one of 150 μm or less or a very large one or more.

In order to prevent the generation of bubbles, Patent Document 1 proposes a method which has a history of filling a crucible raw material in a quartz crucible. The crest of the bottom surface of the inner bottom surface is disposed on the inner bottom surface of the quartz crucible.

[Prior patent documents] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-42968

However, in the conventional method described in Patent Document 1, it is necessary to process the bottom shape of the block along the inner bottom surface of the amount of curvature of the quartz crucible, which is not practical. The shape of the quartz crucible is uneven due to each solid, and it is difficult to process the crucible block in accordance with the unevenness. In the case where the shape of the bottom of the block is inconsistent with the quartz crucible, the fine powder enters the gap between the quartz crucible and the crucible. Due to the fine powder, defects or protrusions are formed on the inner surface of the crucible, and the defect or protrusion may be used as a starting point. Create bubbles. Therefore, according to the method described in Patent Document 1, it is difficult to sufficiently suppress the occurrence or the difference of pinholes in the single crystal.

Accordingly, an object of the present invention is to provide a method for producing a single crystal which prevents bubbles from being taken into a single crystal with low efficiency and higher efficiency, thereby reducing the incidence of pinholes and poor rows.

In order to solve this problem, the method for producing a single crystal of the present invention is to produce a tantalum melt by heating a tantalum raw material in a quartz crucible, and then pulling up the single crystal from the tantalum melt to produce a single crystal according to the CZ method. The method is characterized in that: an elastically deformable germanium wafer having a thickness of less than 1 mm is prepared, and the germanium wafer is placed in the center of the inner bottom surface of the curved portion of the quartz crucible before the germanium raw material is filled in the quartz crucible. Filling the crucible as the raw material of the crucible The quartz crucible of the wafer is elastically deformed along the inner bottom surface of the quartz crucible by the load of the crucible.

According to the present invention, since the germanium wafer placed in the quartz crucible is elastically deformed along the inner bottom surface of the quartz crucible by the load of the crucible block, the inner bottom surface of the quartz crucible can be prevented from being rubbed by the crucible or the fine powder. Contact, and it is possible to prevent defects or protrusions from being formed on the inner bottom surface of the quartz crucible due to the lumps or fine powder. Therefore, it is possible to prevent the bubble from being taken into the single crystal after the bubble is generated starting from the defect or the protrusion, thereby causing the occurrence or the difference of the formation of the particle. Further, according to the present invention, since the inner bottom surface of the quartz crucible is covered by the use of an easily obtainable silicon wafer, it is possible to prevent bubbles from being taken into the single crystal with lower efficiency and higher efficiency.

In the present invention, the surface of the tantalum wafer is preferably mirrored or etched. According to this, the adhesion of the tantalum wafer to the inner bottom surface of the quartz crucible can be improved. Therefore, it is possible to prevent the fine particles from invading between the wafer and the inner bottom surface of the quartz crucible, and the inner bottom surface of the crucible becomes rough, which is likely to cause bubbles.

In the present invention, the diameter of the tantalum wafer is preferably 0.8 times or more and 1.5 times or less the diameter of the single crystal which is pulled up by the tantalum melt. In the case where the diameter of the tantalum wafer is increased by 0.8 times or more of the diameter of the single crystal, it is possible to cover the region on the inner surface of the crucible which is highly likely to be taken into the single crystal. In addition, since the diameter of the quartz crucible used in the drawing of the single crystal is 1.5 times or more the diameter of the single crystal, and the silicon wafer having a diameter of 1.5 times or less the diameter of the single crystal, It is disposed in a quartz crucible. For example, in the case of growing a single crystal having a diameter of 300 mm, a crucible wafer having a diameter of 300 mm or a diameter of 450 mm can be used as a covering material, and the inner bottom surface of the quartz crucible can be covered with a low cost. range.

In the present invention, it is preferable that the peripheral portion of the tantalum wafer is chamfered. Accordingly, it is possible to avoid damage to the inner bottom surface of the quartz crucible by the peripheral portion of the crucible wafer. Therefore, it is possible to prevent the generation of the pinholes in the single crystal caused by the bubbles and the difference in the efficiency of the bubbles generated by the defects formed on the inner bottom surface of the quartz crucible.

In the present invention, it is preferable that the defect of the tantalum wafer having a length of 200 μm or more on the back surface and the end surface of the tantalum wafer is excluded. If there is a defect of 200 μm or more, the critical stress is greatly reduced, and when the germanium material is filled, the defect is used as a starting point, the wafer is cracked, and the inner bottom surface of the quartz crucible may not be completely covered. In addition, when the deformation amount of the defect-free wafer is calculated using a model (simple calculation formula) that supports only the concentrated load at the center of the wafer, the maximum deformation amount of the wafer having a diameter of 200 mm and a thickness of 725 μm is 35 mm. The maximum deformation of a wafer of 300 mm and a thickness of 775 μm is 70 mm, and the maximum deformation of a wafer having a diameter of 450 mm and a thickness of 925 μm is 125 mm. The larger the diameter of the wafer, the more the amount of elastic deformation can be increased. On the other hand, the maximum deformation amount of the germanium wafer having defects of 200 μm or more is 4 mm, 8 mm, and 15 mm, respectively, and the amount of deformation is greatly reduced.

In the present invention, it is preferable to use an unsuitable wafer that does not satisfy a predetermined quality reference as the tantalum wafer. Accordingly, there is almost no increase in the cost of using a germanium wafer as a covering material, and it is possible to avoid treating an unsuitable wafer as a waste material. In addition, examples of wafers that are not suitable for a predetermined quality standard include surface quality defects (LPD, haze, etc.), poor appearance (thickness, diameter, warpage, nanotopography, etc.), and crystallization. Wafers with poor quality (COP, poor group, OSF, BMD, oxygen concentration, etc.).

According to the present invention, it is possible to provide a method for producing a single crystal which can prevent bubbles from being taken into a single crystal with low efficiency and higher efficiency, whereby the generation rate of pinholes and poor rows can be reduced.

1‧‧‧矽Single crystal lifting device

2‧‧‧矽Single crystal

3‧‧‧矽 melt

Room 10‧‧‧

10A‧‧‧Main Room 10A

10B‧‧‧Lift room

11‧‧‧Insulation materials

12‧‧‧Quartz

12a‧‧‧ Straight body of quartz

12b‧‧‧ Corner of Quartz

12c‧‧‧Bottom of quartz crucible

13‧‧‧Base

14‧‧‧Rotating support shaft

15‧‧‧heater

16‧‧‧Hot shield

17‧‧‧ line

18‧‧‧Wire winding mechanism

19A‧‧‧ gas suction port

19B‧‧‧ gas vent

21‧‧‧矽 wafer

22‧‧‧Multiple blocks

Fig. 1 is a schematic cross-sectional view showing the structure of a single crystal pulling device 1.

Fig. 2 (a) to (c) are cross-sectional views for explaining a filling step and a melting step of the crucible raw material in the quartz crucible 12.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 is a schematic cross-sectional view showing the structure of a single crystal pulling device 1.

As shown in Fig. 1, the single crystal pulling device 1 includes a chamber 10, a heat insulating material 11 disposed inside the chamber 10, and a base 13 supporting the quartz crucible 12 housed in the chamber 10; The support shaft 14 supports the base 13 so as to be movable up and down; the heater 15 is disposed to surround the periphery of the base 13; and the substantially inverted conical heat shield 16 is disposed above the base 13; The crystal pulling wire 17 is disposed above the susceptor 13 and disposed coaxially with the rotation support shaft 14; and the wire winding mechanism 18 is disposed above the chamber 10.

The chamber 10 is composed of a main chamber 10A and an elongated cylindrical pulling chamber 10B coupled to an upper opening of the main chamber 10A, the quartz crucible 12, the base 13, the rotating support shaft 14, the heater 15, and the heat. The shielding body 16 is disposed in the main chamber 10A.

The heat shield 16 is provided to surround the single crystal 2 grown in the upper side of the tantalum melt 3. The wire winding mechanism 18 is disposed above the drawing chamber 10B, and the wire 17 passes from the wire winding mechanism 18 through the inside of the drawing chamber 10B and extends downward, and the leading end of the wire 17 reaches the internal space of the main chamber 10A. In the first drawing, the state in which the single crystal 2 is suspended by the line 17 during the growth is shown.

In the step of pulling up the single crystal, first, the quartz crucible 12 is set in the susceptor 13, and the crucible material is filled in the quartz crucible 12, and the seed crystal is attached to the end of the wire 17. Next, the crucible raw material is heated by the heater 15, and the crucible melt 3 is generated, and the seed crystal is depressurized and expanded to be focused on the crucible melt 3. Then, by rotating the seed crystal and the quartz crucible 12, the seed crystal is gradually raised, and the substantially cylindrical single crystal 2 is grown.

In the single crystal pulling, the chamber 10 is maintained in a fixed step-down state. Argon gas is supplied from a gas intake port 19A provided at an upper portion of the lift chamber 10B, and argon gas is exhausted from a gas exhaust port 19B provided at a lower portion of the main chamber 10A, whereby a dotted arrow is generated in the chamber 10. The flow of argon shown.

The diameter of the single crystal 2 is controlled by controlling its pulling speed or the electric power of the heater 15. After the growth of the single crystal 2, after forming the neck having a reduced crystal diameter, the crystal diameter is gradually enlarged to form a shoulder. When the single crystal grows to a predetermined diameter, the diameter is continuously pulled up to form a main body portion, and when the drawing is completed, the diameter is reduced to form a tail portion, and finally the liquid surface is cut. According to the above, the single crystal ingot is completed.

The following is an outline of the single crystal pulling device 1 and the lifting method. Next, the filling step of the crucible raw material in the quartz crucible 12 will be described in detail with reference to Fig. 2 .

In the filling step of the crucible material, first, as shown in Fig. 2(a), a disk-shaped crucible wafer 21 is placed on the inner bottom surface of the empty quartz crucible 12. The quartz crucible 12 is a container made of quartz glass having a round bottom, and has a cylindrical straight body portion 12a having an opening at the upper end, a corner portion 12b formed at a lower end of the straight body portion 12a, and a corner portion 12b via the corner portion 12b. The bottom portion 12c of the straight body portion 12a is connected. Generally, in the 300mm wafer ingot is pulled up, using a diameter of about 800mm, 32 inches, and in the 400mm wafer, the ingot is pulled up, using a diameter of about 1000mm 40 inches. The thickness of 32 inches is preferably 10 mm or more, and the thickness of 40 inches is preferably 13 mm or more.

Further, the quartz crystal crucible 12-series double-layer structure for 矽 single crystal pulling includes an opaque layer provided on the outer surface side and containing a plurality of minute bubbles; and a transparent layer is provided on the inner surface side and substantially No bubbles. Since the inner surface of the crucible is a transparent layer containing no bubbles, the inner surface of the crucible is a smooth surface. The opaque layer serves to uniformly transmit the radiant heat of the heater 15 disposed outside the crucible to the crucible. Further, the transparent layer functions to prevent the quartz pieces from the inner surface of the crucible from being peeled off by the bubbles in the quartz glass and to be taken into the single crystal.

The germanium wafer 21 protects the underlying material of the inner surface of the quartz crucible 12 and is a part of the raw material. As the tantalum wafer 21, a single crystal germanium wafer is preferable, but a polycrystalline germanium wafer may be used. Since the single crystal ruthenium wafer system can be produced by processing the ruthenium single crystal produced by the method for producing ruthenium single crystal according to the present embodiment, it can be easily obtained. Therefore, a part of the germanium wafer cut out from the single crystal ingot can be used as a covering material after the next batch.

矽 Wafer 21 is centered on the center axis of the quartz crucible 12 A uniform manner is disposed in the center of the bottom surface of the quartz crucible 12. By disposing in this manner, the projection area of the single crystal 2 of the inner bottom surface of the quartz crucible 12 can be made as wide as possible, and covered by the wafer 21 without eccentricity. Further, the center of the germanium wafer 21 is preferably aligned with the central axis Zo of the quartz crucible 12. However, the present invention is not limited thereto, and may be disposed at the center of the quartz crucible 12 as far as possible.

The diameter R ₁ of the tantalum wafer 21 is preferably 0.8 times or more and 1.5 times or less the diameter R ₂ of the single crystal 2 to be pulled up. This is because when the diameter R ₁ of the tantalum wafer 21 is less than 0.8 times the diameter R ₂ of the single crystal 2, it is impossible to sufficiently cover the inner bottom surface of the quartz crucible 12 by the wafer 21 to be taken in. A region with high probability in single crystals. It is set to be not more than 1.0 times but 0.8 times or more, and it is considered that the bubble which floats in the 矽 melt 3 and reaches the outer periphery of the 矽 single crystal 2 flows to the outside of the 矽 single crystal 2, and is taken in 矽The possibility of single crystal 2 is very low.

The diameter of the single crystal ingot is greater than the diameter of the wafer of the final product by several mm to several tens of mm. This is because the ruthenium wafer is manufactured by applying a peripheral grinding or chamfering to a single crystal ingot. Therefore, for example, in the case of using a silicon wafer having a diameter of 300 mm, it is impossible to cover the entire surface of a projection area for obtaining a single crystal ingot having a diameter of 300 mm. However, if the diameter of the germanium wafer is smaller than that of the single crystal as described above, it is possible to cover a region where the bubble is likely to be taken into the single crystal. Therefore, a tantalum wafer manufactured from a single crystal ingot can be used as a covering material for the quartz crucible when the single crystal ingot is produced.

Further, in the case where the diameter of the tantalum wafer 21 exceeds 1.5 times the diameter of the single crystal, this is because the diameter of the tantalum crucible 12 is larger than that of the quartz crucible 12, so The method is set in the quartz crucible 12, or even if it is configurable, the setting operation is difficult. On the other hand, it is considered that since the rising velocity of the bubble in the crucible melt is much larger than the convection velocity of the crucible melt, the bubble generated in the crucible melt is not washed away by the convection, but in the crucible melt Rise roughly vertically. Therefore, the bubble generated from the defect of the quartz crucible formed on the inner wall surface of the straight body portion or the corner portion does not cause pinholes or misalignment.

It is also possible to use wafers of a larger generation and lower generation as a covering material for quartz crucibles when manufacturing wafers of the previous generation. For example, when a single crystal having a diameter of 300 mm is pulled up, a silicon wafer having a diameter of 450 mm can be used as a covering material for the quartz crucible. Accordingly, a wider range than the inner bottom surface of the quartz crucible 12 can be covered.

The tantalum wafer 21 has a shape suitable for SEMI specifications, for example, a wafer having a diameter of 300 mm is produced by using a single crystal, and a wafer having a diameter of 300 mm or a diameter of 450 mm is preferably used. Further, it is preferable to use a silicon wafer having a diameter of 450 mm for the production of a single crystal of a wafer having a diameter of 450 mm. This is because these germanium wafers can be easily obtained without special processing, and are also suitable as a covering material, and have sufficient high quality as a raw material for tantalum.

As the tantalum wafer 21, it is also possible to use an unsuitable wafer that does not satisfy the predetermined quality standard. Accordingly, there is almost no increase in the cost of using the germanium wafer 21 as a covering material, and it is possible to avoid treating an unsuitable wafer as a waste material. In addition, as a wafer which is not suitable for a predetermined quality standard, a crystalline unsuitable product may not include a COP (Crystal Originated Particle), an OCR (Oxidation Induced Stacking Fault), or a BMD (Bulk Micro Defect). Wafers of the required specifications for oxygen concentration, or those that are not suitable for shape, may be listed as not satisfying the thickness, chamfering shape, warpage, and surface A wafer of a required specification of nanotopography or a surface quality unsuitable product may be a wafer that does not satisfy the requirements of LPD (Light Point Defect), haze, or the like.

It is preferable that the thickness of the germanium wafer 21 is less than 1 mm. This is because the rigidity is large at 1 mm or more, and it is difficult to elastically deform when loaded, and the wafer may be cracked. In addition, the thickness of the 300 mm 矽 wafer on the SEMI specification is 775 μm, and the thickness of the 450 mm 矽 wafer is 925 μm. In this way, the thickness of the wafer that satisfies the SEMI specification is less than 1 mm and can be elastically deformed.

It is preferable that the germanium wafer 21 is an undoped germanium wafer. In the case where the germanium wafer 21 does not contain a dopant, the doping amount in the germanium melt can be easily controlled. It is also possible to use a germanium wafer containing a dopant, but in this case, it is necessary to determine the doping amount for the entire germanium raw material in consideration of the doping amount in the germanium wafer.

The tantalum wafer 21 is preferably manufactured by a general processing step such as milling, chamfering, polishing, etching, mirror polishing, and washing, and is preferably a polished wafer to which mirror processing is applied. When the surface of the germanium wafer 21 is mirror-finished, the adhesion to the inner bottom surface of the quartz crucible 12 can be improved, and the gap between the inner bottom surface and the germanium wafer 21 can be substantially eliminated. The double-sided mirror surface of the tantalum wafer 21 is preferred, but only one side of the mirror surface may be used. However, in this case, it is necessary to make the side of the mirror surface face the inner bottom surface of the quartz crucible 12. The surface of the wafer 21 may be etched. If it is an etched surface, since it has sufficient smoothness, the adhesiveness with the inner surface of the quartz crucible 12 can be ensured.

The outer circumference of the crucible wafer 21 is preferably chamfered. Further, the notch or the orientation flat may be formed on the tantalum wafer 21 or may not be formed. The chamfering process of the wafer can also be mirror polishing, or isotropic, anisotropic etching. surface. When the outer circumference of the crucible wafer 21 is chamfered, it is possible to prevent the inner surface of the crucible from being scratched due to the outer circumference of the crucible wafer being in contact with the crucible surface.

Next, as shown in FIG. 2(b), the tantalum raw material is filled in the quartz crucible 12 on which the wafer 21 has been deposited. Generally, as the raw material of the crucible, a plurality of blocks 22 are used. The filling method of the plurality of blocks 22 is not particularly limited. For example, the plurality of blocks 22 are placed along the outer peripheral portion of the tantalum wafer 21, and first, the circumference is fixed so that the position of the tantalum wafer 21 is not shifted. Then, the manifold 22 is spread over the central portion of the silicon wafer 21. In this manner, after the plurality of blocks 22 are spread over the entire surface of the silicon wafer 21, the plurality of blocks 22 are gradually deposited thereon, and an appropriate amount of the plurality of blocks 22 are filled into the quartz crucible 12.

The filling amount of the plurality of blocks 22 is different according to the size of the quartz crucible 12, and can be filled with a diameter of 32 to 500 kg in the case of a 32-inch-diameter quartz crucible used for pulling a 300 mm-diameter wafer ingot. Block 22. Further, in the case of a 40-inch quartz crucible for a 450 mm wafer, a multi-turn block 22 of about 800 to 900 kg can be filled.

Since the shape of the wafer 21 is flat without any stress, the silicon wafer 21 is not matched with the curved inner bottom surface of the quartz crucible 12, but the load increases as the filling amount of the crucible material increases, due to elastic deformation. It gradually bends and finally fits along the inner bottom surface of the quartz crucible 12. Since the calculation can produce about 7 cm in a 300 mm diameter wafer and about 12 cm in a 450 mm diameter wafer, it is possible to make the surface of the tantalum wafer 21 along the shape of the crucible.

The multi-tanning block 22 which is a raw material of a single crystal is produced by purifying a high-purity metal crucible and then crushing it and granulating it. When the corner is in contact with the surface of the crucible and is pressed, the surface of the crucible may be damaged. Further, since the multi-clams 22 are rubbed against each other to produce fine powder, this may make the inner surface of the crucible rough.

However, in the present embodiment, since the crucible wafer 21 is placed and the inner bottom surface of the quartz crucible 12 is placed before the multi-turn block 22 is filled, the inner bottom surface of the quartz crucible 12 is not damaged by the sharp corners of the crucible. Further, since the tantalum wafer 21 is subjected to the load of the plurality of the blocks 22 and is elastically deformed along the curved inner bottom surface of the quartz crucible 12, there is no room for the flawless fine powder to enter the gap between the two. The inner surface of the crucible becomes a rough thing due to the influence of the fine powder.

Next, as shown in Fig. 2(c), the multi-turn block 22 in the quartz crucible 12 is heated to generate the crucible melt 3. As the heating of the plurality of blocks 22 progresses, the tantalum wafer 21 is also softened, and since the adhesion to the quartz crucible 12 is increased, the inner surface of the crucible can be surely protected. The heating progresses further, and the crucible wafer 21 starts to melt, but since the melting of the multi-tanning block 22 also progresses, the sharp corners also become rounded, so that the inner surface of the crucible can be prevented from being damaged. Finally, the tantalum wafer 21 is completely melted together with the manifold 22 as part of the tantalum melt.

Then, the seed crystal is immersed in the liquid surface of the cerium melt, and the seed crystal is pulled up to grow the singular crystal. According to the above, the single crystal is completed.

As described above, the method for producing the single crystal of the present embodiment is to cover the inner bottom surface of the quartz crucible 12 by using the tantalum wafer 21 which is elastically deformed to be in close contact with the inner bottom surface of the curved portion of the quartz crucible 12, and then filled. Since the raw material is ruthenium, it is possible to prevent defects or protrusions from being formed on the inner surface of the crucible due to contact with the crucible material. Therefore, it is possible to prevent a bubble generated by a defect or a protrusion which has been formed on the inner surface of the crucible as a starting point from being taken into a single crystal to form a pinhole or a poor row.

Further, according to the present embodiment, since the elastically deformable silicon wafer 21 is used as a covering material for the inner bottom surface of the quartz crucible 12, it is not necessary to process the curved shape of the inner bottom surface of the quartz crucible 12 as in the conventional crucible. The shape of the bottom surface reduces the time and cost required for processing.

Further, according to the present embodiment, since the surface of the tantalum wafer 21 is smoothed by mirror polishing or etching, the adhesion to the inner bottom surface of the quartz crucible 12 can be improved, and the inner bottom surface and the twin crystal can be substantially eliminated. The gap between the circles 21. Therefore, it is possible to prevent the defect or the protrusion from being formed on the inner surface of the crucible due to the intrusion of the fine powder into the gap between the crucible 21 and the inner surface of the crucible.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit and scope of the invention. This is a matter of course.

For example, in the above-described embodiment, a bulky ruthenium is used for the ruthenium raw material, but a single crystal ruthenium may be used. In this case, all of the lumps may be replaced by single crystal ruthenium, or a part of the ruthenium block may be replaced by a single crystal ruthenium.

[Examples]

A tantalum wafer having a diameter of 300 mm and a thickness of 775 μm was placed in the center of the inner bottom surface of a quartz crucible having a diameter of 800 mm provided in a chamber of a single crystal pulling device.矽 Wafers are polished wafers produced by general processing steps such as milling, chamfering, polishing, etching, mirror polishing, and cleaning, using those that are not damaged by processing or metal.

Then, after filling 300 kg of the mass in the quartz crucible, It is heated by a heater to produce a crucible melt. Then, the pulling up of a single crystal having a diameter of 310 mm was performed. Next, after the thickness of the wafer was cut out from the obtained single crystal block, the presence or absence of the difference and the pinhole were examined.

In the inspection of the difference row, in the case where the crystal wall line existing on the side of the single crystal is to the bottom, the 1 mm thick germanium wafer sliced from the bottom position is selectively etched, and it is checked whether or not the difference is observed. The pit caused. The difference rate is defined by the value of the weight of the ruthenium crystal after the position where the difference is arranged, in addition to the weight of the ruthenium material filled by the quartz crucible.

Further, in the pinhole inspection, each of the wafers obtained by slicing the single crystal block was measured in the area counter mode of the particle counter, and the wafer containing the pinhole was confirmed. The pinhole generation rate is a value obtained by dividing the total number of pinholes contained in a plurality of wafers obtained from one single crystal ingot by the number of wafers.

As a result, the difference rate was 10% or less, and the pinhole generation rate was 0%.

(Comparative example)

On the other hand, when the single crystal is pulled up without wafer under the inner surface of the crucible, the difference ratio is 20%, and the pinhole generation rate is 1%.

From the above results, it was found that the spread ratio and the pinhole generation rate were lowered by laying the tantalum wafer on the inner bottom surface of the quartz crucible.

2‧‧‧矽Single crystal

3‧‧‧矽 melt

12‧‧‧Quartz

12a‧‧‧ Straight body of quartz

12b‧‧‧ Corner of Quartz

12c‧‧‧Bottom of quartz crucible

13‧‧‧Base

14‧‧‧Rotating support shaft

21‧‧‧矽 wafer

22‧‧‧Multiple blocks

The central axis of Zo‧‧‧Quartz

R ₁ ‧‧‧矽 wafer diameter

R ₂ ‧‧‧矽 diameter of single crystal

Claims (6)

The invention relates to a method for producing a single crystal, which is a method for producing a single crystal according to the CZ method, which is obtained by heating a crucible material in a quartz crucible to generate a crucible melt, and then pulling up the crucible single crystal from the crucible melt. Preparing an elastically deformable 300-450 mm diameter silicon wafer having a thickness of less than 1 mm, and placing the germanium wafer in the center of the inner bottom surface of the curved portion of the quartz crucible before filling the germanium material into the quartz crucible; Filling the crucible as the crucible material in the quartz crucible on which the crucible wafer is placed, and causing the crucible wafer to elastically deform along the inner bottom surface of the quartz crucible by the load of the crucible The surface of the germanium wafer is along the shape of the inner bottom surface of the quartz crucible. The method for manufacturing a single crystal according to the first aspect of the patent application, wherein the surface of the germanium wafer is a mirror surface or an etched surface. The method for producing a single crystal according to claim 1 or 2, wherein the diameter of the tantalum wafer is 0.8 times or more and 1.5 times or less the diameter of the single crystal which is pulled up from the tantalum melt. A method for producing a single crystal of the first or second aspect of the patent application, wherein the peripheral portion of the tantalum wafer is chamfered. The method for producing a single crystal according to the first or second aspect of the patent application, wherein the tantalum wafer is excluded from defects having a length of 200 μm or more on the front and back surfaces. A method of manufacturing a single crystal according to claim 1 or 2, wherein an unsuitable wafer that does not satisfy a predetermined quality standard is used as the tantalum wafer.