JP6485286B2 - Method for producing silicon single crystal - Google Patents

Description

  The present invention relates to a method and apparatus for producing a silicon single crystal by the Czochralski method (hereinafter referred to as “CZ method”), and in particular, MCZ (Magnetic field applied) for pulling up a single crystal while applying a magnetic field to a silicon melt. CZ) law.

  The MCZ method is known as a method for producing a silicon single crystal by the CZ method. In the MCZ method, the melt convection is suppressed by applying a magnetic field to the silicon melt in the quartz crucible, and the elution of oxygen from the quartz crucible is suppressed. There are various methods for applying a magnetic field, but the HMCZ (Horizontal MCZ) method for pulling up a single crystal while applying a horizontal magnetic field has been put into practical use.

  For example, Patent Document 1 describes an HMCZ method in which a horizontal magnetic field center line is set in the vicinity of a melt surface within 5 cm from the melt surface during the entire process of growing a silicon single crystal. According to this method, convection near the melt surface is suppressed, and heat convection below the melt surface is strengthened, so heat transfer to the solid-liquid interface is enhanced, and the temperature between the crucible and the solid-liquid interface is increased. The difference can be reduced. Further, since the melt sufficiently stirred below the melt surface is supplied to the solid-liquid interface, a single crystal with more uniform characteristics can be obtained, and cracking of the quartz crucible due to thermal stress can be prevented. In Patent Document 2, in order to prevent a rapid increase in crystal diameter and deterioration of in-plane distribution of oxygen concentration, the position in the height direction of the center of the horizontal magnetic field is set at a position 100 mm or more away from the melt surface. An HMCZ method for carrying out the pulling process is also described.

JP-A-8-231294 JP 2004-182560 A

  However, the conventional magnetic field application method in which the magnetic field center line is set in the vicinity of the melt surface has a problem that the melt surface is solidified during the single crystal tail-drawing process and crystal precipitation occurs on the melt surface. When the thin crystal film deposited on the melt surface is integrated with the growing single crystal, the crystal film that protrudes from the side surface of the single crystal interferes with in-furnace members such as a heat shield, so the single crystal is pulled upward. Can not be. Therefore, when crystal precipitation occurs, the pulling process must be interrupted immediately, and the single crystal must be immediately separated from the melt surface. At this time, the single crystal causes dislocation and the product yield decreases. There is a fear.

  Such crystal precipitation is likely to occur at the end of the pulling process when the pulling rate of a silicon single crystal having a diameter of about 300 mm is 90% or more, particularly when the amount of silicon remaining in the quartz crucible is 25 kg or less. Easy to get up. Further, when the silicon residual liquid amount is small, an attempt to suppress the crystal precipitation by increasing the power of the heater is limited, and it is difficult to suppress the crystal precipitation.

  Therefore, an object of the present invention is to prevent the occurrence of crystal precipitation on the melt surface at the end of the pulling process of the silicon single crystal by the HMCZ method, thereby suppressing the decrease in product yield of the single crystal. The object is to provide a method and an apparatus for producing a single crystal.

  In order to solve the above-mentioned problems, a method for producing a silicon single crystal according to the first aspect of the present invention pulls up the silicon single crystal from the silicon melt while applying a horizontal magnetic field to the silicon melt contained in the quartz crucible. A method for manufacturing a silicon single crystal, wherein a first magnetic field applying step of applying a horizontal magnetic field by setting a height position of a magnetic field center near a melt surface, and a height position of the magnetic field center being a melt surface A second magnetic field application step for setting the horizontal magnetic field to be set lower than the vicinity, wherein the first magnetic field application step is performed at least during the step of growing the product acquisition region of the silicon single crystal, The second magnetic field application step is performed after completion of the product acquisition region growing step.

  In addition, the method for producing a silicon single crystal according to the second aspect of the present invention provides a method for producing a silicon single crystal by pulling up the silicon single crystal from the silicon melt while applying a horizontal magnetic field to the silicon melt contained in the quartz crucible. A silicon melt generating step of heating a silicon raw material in the quartz crucible to generate a silicon melt; a landing step of depositing a seed crystal in the silicon melt; and a crystal diameter gradually A shoulder part growing process for growing the increased shoulder part, a body part growing process for growing a body part whose crystal diameter is kept constant, and a tail part growing process for growing a tail part where the crystal diameter gradually decreases. And the height of the center position of the horizontal magnetic field in the tail portion growing step is lower than the height of the center position of the horizontal magnetic field in the body portion growing step. To.

  Furthermore, a silicon single crystal manufacturing apparatus according to the present invention includes a quartz crucible that supports a silicon melt, a magnetic field application device that applies a horizontal magnetic field to the silicon melt, and a pulling mechanism that pulls up the silicon single crystal from the silicon melt. The magnetic field application device includes a control unit that controls a position in the height direction of the horizontal magnetic field, and the control unit is configured to maintain a magnetic field center until a step of growing the product acquisition region of the silicon single crystal is completed. The horizontal position is set near the melt surface, the horizontal magnetic field is applied, and the height of the magnetic field center is set below the melt surface after the product acquisition region is grown. Then, the horizontal magnetic field is applied.

  In the present invention, the product acquisition region refers to a portion of the entire body portion that can be a semiconductor wafer as a final product, and the electrical resistivity and oxygen concentration determined according to the specifications of the final product wafer. It is an area that satisfies the necessary quality. According to the present invention, the height position of the magnetic field center is moved downward from the vicinity of the melt surface after completion of the growing process of the single crystal product acquisition region. Convection can be activated. Therefore, it is possible to ensure the crystal quality of the product acquisition region and to prevent the melt surface from solidifying during the tail drawing in the HMCZ method and to cause crystal precipitation, thereby suppressing the decrease in the product yield of the single crystal. Can do.

  In the present invention, the first magnetic field application step is performed from the start of the silicon single crystal pulling step until the pulling rate of the silicon single crystal reaches 90%, and the second magnetic field applying step includes: It is preferable that this is performed between the time when the pulling rate of the silicon single crystal reaches 90% and the end of the pulling step. Thus, the problem of crystal precipitation on the melt surface can be solved by lowering the height position of the magnetic field center when the pulling rate of the single crystal reaches 90%.

  In the present invention, the first magnetic field applying step is performed at least during a body portion growing step for growing a body portion in which the crystal diameter is maintained constant, and the second magnetic field applying step is performed by gradually increasing the crystal diameter. It is preferable to be performed during the tail part growing step of growing the reduced tail part. By performing the first magnetic field application step in the body growing step of the silicon single crystal, the quality of the product acquisition region of the single crystal can be ensured. Also, by performing the second magnetic field application process in the tail growing process, it is possible to prevent the melt surface from solidifying during the tail drawing and to prevent crystal precipitation, and to suppress a decrease in product yield of the single crystal. can do.

  In the second magnetic field application step, the distance from the magnetic field center position to the melt surface is preferably 150 mm or more. When the center position of the horizontal magnetic field is lowered by 150 mm or more from the melt surface in the second magnetic field application step, convection near the melt surface can be sufficiently activated. Therefore, it is possible to prevent the product yield from being lowered due to crystal precipitation on the melt surface at the end of the pulling process.

  According to the present invention, it is possible to prevent crystal precipitation from occurring on the melt surface at the end of the pulling process of the silicon single crystal by the HMCZ method, and thereby to suppress a decrease in product yield of the single crystal. The manufacturing method and apparatus can be provided.

It is a longitudinal cross-sectional view which shows the structure of the silicon single crystal manufacturing apparatus by embodiment of this invention. It is a flowchart explaining the manufacturing method of the silicon single crystal by the 1st Embodiment of this invention. It is a schematic sectional drawing which shows the shape of a silicon single crystal ingot. It is a longitudinal cross-sectional view which shows the state which pulled down the magnetic field center position in the silicon single crystal manufacturing apparatus shown in FIG. It is a flowchart explaining the manufacturing method of the silicon single crystal by the 2nd Embodiment of this invention. It is a flowchart explaining the manufacturing method of the silicon single crystal by the 3rd Embodiment of this invention.

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

  FIG. 1 is a longitudinal sectional view showing a configuration of a silicon single crystal manufacturing apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the silicon single crystal manufacturing apparatus 1 includes a chamber 10, a heat insulating material 11 disposed along the inner surface of the chamber 10, a quartz crucible 12 disposed in the center of the chamber 10, and a quartz crucible. The susceptor 13 that supports the susceptor 13, the rotation support shaft 14 that supports the susceptor 13 so as to be movable up and down, the heater 15 that is disposed around the susceptor 13, and the substantially inverted truncated conical heat shield that is disposed above the susceptor 13 A body 16, a single crystal pulling wire 17 disposed above the susceptor 13 and coaxially with the rotation support shaft 14, a wire winding mechanism 18 disposed above the chamber 10, and the outside of the chamber 10. And a magnetic field application device 30 provided.

  The chamber 10 includes a main chamber 10A and an elongated cylindrical pull chamber 10B connected to the upper opening of the main chamber 10A. The quartz crucible 12, the susceptor 13, the rotation support shaft 14, the heater 15, The heat shield 16 is provided in the main chamber 10A.

  The heater 15 is used for melting a silicon raw material filled in the quartz crucible 12 to generate a silicon melt. The heater 15 is a carbon resistance heating heater, and is provided so as to surround the quartz crucible 12 in the susceptor 13. The heat shield 16 is provided above the silicon melt 3 so as to surround the silicon single crystal 2 being grown.

  The wire 17 and the wire winding mechanism 18 constitute a pulling mechanism for pulling up the single crystal. The wire winding mechanism 18 is disposed above the pull chamber 10B, the wire 17 extends downward from the wire winding mechanism 18 through the pull chamber 10B, and the tip of the wire 17 is located inside the main chamber 10A. The space has been reached. FIG. 1 shows a state in which the silicon single crystal 2 being grown is suspended from the wire 17.

  A gas inlet 19A for introducing argon gas into the chamber 10 is provided at the top of the pull chamber 10B, and gas exhaust for exhausting the argon gas in the chamber 10 is provided at the bottom of the main chamber 10A. A mouth 19B is provided. Argon gas is introduced into the chamber 10 from the gas inlet 19A, and the amount of introduction is controlled by the valve 20A. Further, since the argon gas in the sealed chamber 10 is exhausted from the gas exhaust port 19B to the outside of the chamber, it is possible to collect the SiO gas and CO gas in the chamber 10 to keep the inside of the chamber 10 clean. . A valve 20B and a vacuum pump 21 are installed in the middle of the pipe connected to the gas exhaust port 19B, and the flow rate is controlled by the valve 20B while suctioning the argon gas in the chamber 10 by the vacuum pump 21. The inside of 10 is kept at a constant reduced pressure state.

  The magnetic field application device 30 includes a pair of electromagnet coils 31A and 31B arranged opposite to each other across the main chamber 10A, a support base 32 that supports the electromagnet coils 31A and 31B, a lifting mechanism 33 of the support base 32, and the electromagnet coil. 31A, 31B and a control unit 34 for controlling the lifting mechanism 33. The electromagnet coils 31A and 31B and the elevating mechanism 33 operate according to instructions from the control unit 34, and the magnetic field strength and the position of the electromagnet coils 31A and 31B in the height direction are controlled. The center position (magnetic field center position C) of the horizontal magnetic field generated by the magnetic field application device 30 can be moved in the vertical direction. The magnetic field center position C refers to a position in the height direction of a horizontal line (magnetic field center line) connecting the centers of the electromagnet coils 31A and 31B arranged opposite to each other. According to the horizontal magnetic field method, convection of the silicon melt 3 can be effectively suppressed.

  In the above configuration, in the manufacture of the silicon single crystal, the quartz crucible 12 filled with the silicon raw material is set in the susceptor 13 and a seed crystal is attached to the tip of the wire 17. Next, the silicon raw material in the quartz crucible 12 is heated by the heater 15 to generate the silicon melt 3.

  In the step of pulling up the silicon single crystal, the seed crystal is lowered and immersed in the silicon melt 3, and then the seed crystal and the quartz crucible 12 are respectively rotated while slowly raising the seed crystal so as to form a substantially circular shape below the seed crystal. A columnar silicon single crystal 2 is grown. At that time, the diameter of the silicon single crystal 2 is controlled by controlling the pulling speed and the power of the heater 15. Further, by applying a horizontal magnetic field to the silicon melt 3, melt convection in a direction perpendicular to the magnetic field lines can be suppressed.

  FIG. 2 is a flowchart illustrating a method for manufacturing a silicon single crystal according to the first embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing the shape of a silicon single crystal ingot. Further, FIG. 4 is a longitudinal sectional view showing a state where the magnetic field center position C is lowered in the silicon single crystal manufacturing apparatus 1 shown in FIG.

  As shown in FIGS. 2 and 3, in the production of the silicon single crystal 2, the silicon raw material in the quartz crucible 12 is heated to generate the silicon melt 3, the silicon melt generation step S 11, and the seed crystal is converted into the silicon melt 3. A liquid landing step S12 for landing the liquid, a necking step S13 for forming the neck portion 2a with a narrowed crystal diameter, a shoulder portion growing step S14 for forming the shoulder portion 2b by expanding the crystal diameter in a conical shape, When the single crystal grows to a diameter of 5 mm, the body part growing step S15 continues to be pulled up with a constant diameter to form the body part 2c, and the tail part is squeezed at the end of the pulling, and finally the tail part is separated from the liquid surface. Step S16 is performed in order. Thus, the silicon single crystal ingot 2 having the neck portion 2a, the shoulder portion 2b, the body portion 2c, and the tail portion 2d is completed.

  Also, as shown in FIG. 2, during the period from the start of the liquid deposition step S12 to the end of the body part growing step S15, the first magnetic field application step of pulling up the single crystal by setting the magnetic field center position C near the melt surface. Perform H1. Here, “near the melt surface” means within a range of ± 50 mm from the liquid surface of the silicon melt. If the magnetic field center position C is within this range, the same effect as when the magnetic field center position C matches the melt surface can be obtained, and convection of the melt surface can be suppressed.

  As the growth of the single crystal progresses and the melt is consumed, the melt surface gradually decreases, but the quartz crucible 12 is raised in accordance with the decrease in the melt surface, so that the absolute height of the melt surface is constant. Therefore, during the pulling of the single crystal, the magnetic field center position C can be fixed near the melt surface.

  Thus, by setting the magnetic field center position C in the vicinity of the melt surface of the silicon melt 3 in the single crystal body part growing step, thermal convection in the vicinity of the melt surface is suppressed and lower than the vicinity of the melt surface. Therefore, the heat transfer to the solid-liquid interface is enhanced, and the temperature difference between the crucible and the solid-liquid interface can be reduced. In addition, since the melt sufficiently stirred below the melt surface is supplied to the solid-liquid interface, a single crystal with more uniform characteristics can be obtained, and cracking of the quartz crucible 12 due to thermal stress can be prevented.

  On the other hand, as shown in FIG. 4, between the start and end of the tail portion growing step S16, the pair of electromagnet coils 31A and 31B of the magnetic field applying device 30 are lowered to lower the magnetic field center position C below the melt surface. And a second magnetic field application step H2 for pulling up the single crystal is performed. Thus, by setting the magnetic field center position C below the melt surface at the end of the pulling process, convection in the vicinity of the melt surface can be actively generated and crystal precipitation on the melt surface can be suppressed. . In this case, the distance h from the magnetic field center position C to the melt surface is preferably 150 mm or more. Thus, by lowering the magnetic field center position C by 150 mm or more from the melt surface, the convection near the melt surface can be sufficiently activated, and the effect of suppressing crystal precipitation on the melt surface can be enhanced.

  In general, the tail portion 2d of the single crystal is a portion that is not used as a product, and the product acquisition region is the body portion 2c. Therefore, it is not necessary to control the unit quality by applying a horizontal magnetic field in the tail portion growing step S16. . In the tail portion growing step S16, it is important to quickly separate from the melt so as not to deteriorate the quality of the single crystal that has been grown so far. The lowering of the magnetic field center position C in the tail portion growing step S16 is the tail portion growing step. This is performed so that the quality of the single crystal does not deteriorate during S16.

  As described above, the silicon single crystal manufacturing method according to the present embodiment lowers the magnetic field center position C below the melt surface after the body part growing process, so that the melt surface is solidified at the end of the pulling process. Thus, the occurrence of crystal precipitation can be prevented, thereby suppressing the decrease in product yield.

  FIG. 5 is a flowchart illustrating a method for manufacturing a silicon single crystal according to the second embodiment of the present invention.

  As shown in FIG. 5, the silicon single crystal manufacturing method according to the present embodiment has a single crystal pulling rate of 90% after the body portion growing step S15 is completed and the tail portion growing step S16 is started. The second magnetic field applying step H2 is performed in which the magnetic field center position C is lowered below the melt surface at the time of reaching the point. That is, the lowering of the magnetic field center position C starts slightly later than in the first embodiment. Others are the same as in the first embodiment.

  The pulling rate of the single crystal means the weight ratio of the single crystal to the raw material. Crystal precipitation on the melt surface tends to occur frequently when the pulling rate of the single crystal is 90% or more. Therefore, the problem of crystal precipitation on the melt surface can be solved if the magnetic field center position C is lowered when the pulling rate reaches 90% without being pulled down immediately after the body part growing step S15. There can be obtained the same effect as the first embodiment.

  FIG. 6 is a flowchart for explaining a method of manufacturing a silicon single crystal according to the third embodiment of the present invention.

  As shown in FIG. 6, in the method for manufacturing a silicon single crystal according to the present embodiment, the magnetic field center position C is set at the melt surface when the growth of the single crystal product acquisition region is completed in the middle of the body part growing step S15. The second magnetic field applying step H2 is performed by pulling it downward. That is, the lowering of the magnetic field center position C is started a little earlier than in the first embodiment. Others are the same as in the first embodiment.

  The single crystal product acquisition area does not necessarily extend over the entire body part. For example, the lower part of the body part 2c does not become the product acquisition area because the impurity concentration, electrical resistivity, oxygen concentration, etc. do not satisfy the requirements. There is a case. In this case, the magnetic field center position C is set in the vicinity of the melt surface only during the process of growing the product acquisition area, and then the magnetic field center position C is lowered to ensure the crystal quality of the product acquisition area, while out of the product acquisition area. It is possible to reliably suppress crystal precipitation on the melt surface. Therefore, according to the present embodiment, the same effect as that of the first embodiment can be obtained.

  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 can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

  For example, in the above-described embodiment, the first magnetic field application process H1 for setting the magnetic field center position C near the melt surface is started from the liquid deposition work S12. However, the start timing of the first magnetic field application process H1 is The magnetic field application may be started from, for example, the silicon melt generation step S11, the magnetic field application may be started from the necking step S13 or the shoulder portion growing step S14, and the magnetic field application is started from the body portion growing step S15. You may start. That is, the first magnetic field applying step H1 may be performed at least during the growing step of the single crystal product acquisition region.

DESCRIPTION OF SYMBOLS 1 Silicon single crystal manufacturing apparatus 2 Silicon single crystal 2a Neck part 2b Shoulder part 2c Body part 2d Tail part 3 Silicon melt 10 Chamber 10A Main chamber 10B Pull chamber 11 Heat insulating material 12 Quartz crucible 13 Susceptor 14 Rotation support shaft 15 Heater 16 Heat Shield 17 Wire for pulling up single crystal 18 Wire winding mechanism 19A Gas inlet 19B Gas exhaust 20A Valve 20B Valve 21 Vacuum pump 30 Magnetic field applying device 31A, 31B Electromagnetic coil 32 Support base 33 Lifting mechanism 34 Control unit

Claims (4)

A silicon single crystal manufacturing method for pulling up a silicon single crystal from the silicon melt while applying a horizontal magnetic field to the silicon melt contained in a quartz crucible,
A first magnetic field application step of setting the height position of the magnetic field center near the melt surface and applying the horizontal magnetic field;
A second magnetic field application step of applying the horizontal magnetic field by setting the height position of the magnetic field center at least 150 mm below the melt surface ,
The first magnetic field application step is performed at least during a body portion growing step for growing a body portion in which a crystal diameter of the silicon single crystal is maintained constant,
The method for producing a silicon single crystal, wherein the second magnetic field applying step is performed during a tail portion growing step for growing a tail portion in which a crystal diameter of the silicon single crystal is gradually reduced . The first magnetic field application step is performed between the start of the silicon single crystal pulling step and the middle of the tail portion growing step in which the pulling rate of the silicon single crystal reaches 90%.
2. The method for producing a silicon single crystal according to claim 1, wherein the second magnetic field application step is performed after the pulling rate of the silicon single crystal reaches 90% until the end of the pulling step. A silicon single crystal manufacturing method for pulling up a silicon single crystal from the silicon melt while applying a horizontal magnetic field to the silicon melt contained in a quartz crucible,
A silicon melt generating step of generating a silicon melt by heating the silicon raw material in the quartz crucible;
A liquid deposition step of depositing a seed crystal on the silicon melt;
A shoulder portion growing step for growing a shoulder portion having a gradually increased crystal diameter;
A body part growing process for growing a body part in which the crystal diameter is kept constant;
A tail portion growing step for growing a tail portion in which the crystal diameter gradually decreases,
The height of the center position of the horizontal magnetic field in the body part growing step is near the melt surface,
The method for producing a silicon single crystal, wherein a height of a central position of the horizontal magnetic field in the tail portion growing step is 150 mm or more below the melt surface . The height of the central position of the horizontal magnetic field in the period from the start of the pulling process of the silicon single crystal to the middle of the tail growing process where the pulling rate of the silicon single crystal reaches 90% is near the melt surface,
The height of the center position of the horizontal magnetic field in a period from when the pulling rate of the silicon single crystal reaches 90% to the end of the pulling step is 150 mm or more below the melt surface. A method for producing a silicon single crystal.

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