JP2007022901A - Apparatus and method for manufacturing silicon single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for manufacturing a silicon single crystal, with which the silicon single crystal can be pulled at a high speed while keeping the oxygen concentration in the radial direction of the silicon single crystal uniform by controlling the oxygen concentration in the single crystal by appropriately controlling the temperature gradients of the surface and the inside of a silicon melt and the speed distribution in the melt. <P>SOLUTION: The apparatus for manufacturing the silicon single crystal is equipped with a heater for heating a quartz crucible 4a from the periphery of the crucible 4a, a radiation heat shielding body 13 for preventing heating of the silicon single crystal 12 by radiation heat, and a rotating magnetic field device for applying a plurality of rotating magnetic fields MF having at least different rotation frequencies in the rotation direction, the rotation frequency and the magnetic field intensity in the plane vertical to the pulling direction of the silicon single crystal 12 to a silicon melt 15 in the quartz crucible 4a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a silicon single crystal manufacturing technique by the Czochralski method (hereinafter referred to as CZ method), and in particular, a silicon single crystal manufacturing apparatus that performs crystal growth by a magnetic field pulling method (hereinafter referred to as MCZ method). And a manufacturing method.

  The MCZ method is a method for growing a crystal in a state where the kinematic viscosity of the silicon melt is increased by applying a magnetic field. According to the MCZ method, since the convection of the melt is controlled by the action of a magnetic field, stable crystal growth can be performed. In addition, the MCZ method is an effective method for controlling the oxygen concentration in the silicon single crystal because the flow of the melt containing oxygen generated from the crucible can be controlled.

As a conventional silicon single crystal manufacturing technique using the MCZ method, convection in the silicon melt, especially the surface, is applied to the crucible by applying a rotating magnetic field from the outside in the opposite direction or the same direction as the rotating direction. There is known a method for controlling the oxygen concentration in a silicon single crystal to be grown by controlling the flow of melt in (Patent Document 1, Patent Document 2).
JP 59-73491 A Japanese Patent Publication No. 63-53157

  However, just by changing the rotation direction and strength of the rotating magnetic field applied to the silicon melt as in the conventional silicon single crystal manufacturing technology described above, the direction and speed of the crucible center region and the outer region can be adjusted. Since the silicon melt cannot be moved differently, the temperature gradient and velocity distribution in the surface and inside of the silicon melt cannot be appropriately controlled.

  The problem to be solved by the present invention is to control the oxygen concentration of the grown silicon single crystal and keep it uniform in the radial direction by appropriately controlling the temperature gradient and velocity distribution inside and inside the silicon melt. Meanwhile, an object of the present invention is to provide a silicon single crystal manufacturing apparatus capable of pulling up a silicon single crystal at high speed.

  In order to solve the above problems, a manufacturing apparatus of the present invention prevents a crucible containing a silicon melt, a heater for heating the crucible from the surroundings, and heating of the silicon single crystal due to radiant heat from the heater and the crucible. A radiant heat shield provided to the surface, and a rotation direction, a rotation frequency, and a magnetic field strength in a plane perpendicular to the pulling direction of the silicon single crystal, and at least a plurality of rotating magnetic fields having different rotation frequencies in the crucible And a rotating magnetic field device applied to the silicon melt.

  According to the manufacturing apparatus configured as described above, at least a plurality of rotating magnetic fields having different rotation frequencies among the rotation direction, the rotation frequency, and the magnetic field strength in a plane perpendicular to the pulling direction of the silicon single crystal are crucible. By applying to the inner silicon melt, the silicon melt can be moved in different directions and speeds in the central region and the outer region of the crucible. In addition, by appropriately controlling the velocity distribution, the silicon single crystal can be pulled at a high speed while controlling the oxygen concentration of the grown silicon single crystal and keeping it uniform in the radial direction.

  In this manufacturing apparatus, the rotating magnetic field device reduces a temperature gradient in the vertical direction of the silicon melt in a region immediately below the silicon single crystal, and has a diameter on the surface of the silicon melt near the outer periphery of the silicon single crystal. In order to increase the temperature gradient in the direction, it is desirable to generate the plurality of rotating magnetic fields.

  According to this manufacturing apparatus, by reducing the vertical temperature gradient of the silicon melt in the region immediately below the silicon single crystal, heat transfer from the silicon melt to the silicon single crystal being pulled can be suppressed, By increasing the temperature gradient in the radial direction on the surface of the silicon melt near the outer periphery of the silicon single crystal, it is possible to prevent deformation of the silicon single crystal that is pulled up.

  In the rotating magnetic field apparatus, the silicon single crystal has a position where the flow of the surface of the silicon melt flowing from the center of the crucible to the outside and the flow of the surface of the silicon melt flowing from the outside to the inside collide with each other. It is desirable to generate the plurality of rotating magnetic fields so as to be outside.

  According to this manufacturing apparatus, not only the oxygen concentration of the grown silicon single crystal can be controlled but also the in-plane oxygen concentration distribution can be improved.

  Moreover, it is desirable that the rotating magnetic field device controls the plurality of rotating magnetic fields so that the rotation frequency is 1 Hz or more and 1000 Hz or less. If the frequency of the rotating magnetic field is less than 1 Hz, it will be difficult to obtain a sufficient output from the rotating magnetic field device (particularly an inexpensive device), and if it exceeds 1000 Hz, it will be difficult for the magnetic field to penetrate into the silicon melt and rotate the silicon melt. Insufficient power to be obtained.

  Moreover, it is desirable that the rotating magnetic field device controls the plurality of rotating magnetic fields so that a maximum rotation speed of the silicon melt is 1 rpm or more and 200 rpm or less. If the rotation speed of the silicon melt is less than 1 rpm, the effect of rotation by the rotating magnetic field is too small compared to the flow caused by the heat convection or the rotation of the crucible or silicon single crystal. As a result, the rise of the hot water level in the area becomes large, which hinders the pulling of crystals.

  The manufacturing method of the present invention includes a crucible containing a silicon melt, a heater for heating the crucible from the surroundings, and a radiant heat shield provided to prevent heating of the silicon single crystal due to radiant heat from the heater and the crucible. And a rotating magnetic field that applies to the silicon melt in the crucible at least a plurality of rotating magnetic fields having different rotating frequencies among rotation directions, rotation frequencies, and magnetic field strengths in a plane perpendicular to the pulling direction of the silicon single crystal. A silicon single crystal is produced by the Czochralski method using a production apparatus comprising a device, wherein the rotary magnetic field device is used to shield the radiant heat from the heater and the crucible with a radiant heat shield, By applying a rotating magnetic field to the silicon melt, the direction and speed of the central region of the crucible and the region outside the crucible are made different. While moving the NTorueki is characterized by performing the pulling of the silicon single crystal.

  According to this manufacturing method, by appropriately controlling the temperature gradient and velocity distribution inside and inside the silicon melt, the oxygen concentration of the grown silicon single crystal is controlled and kept uniform in the radial direction. A single crystal can be pulled up at high speed.

  In the manufacturing method of the present invention, the rotation frequency of the rotating magnetic field is 10 Hz or more and 200 Hz or less, the rotation direction of the rotating magnetic field is opposite to the rotation direction of the crucible, and the rotation direction of the rotating magnetic field is the rotation direction. It is preferable that the rotation speed of the silicon single crystal is opposite to the rotation direction of the silicon single crystal, the rotation speed of the crucible is 1 rpm to 12 rpm, and the rotation speed of the silicon single crystal is 0.1 rpm to 20 rpm.

  According to the present invention, the silicon single crystal can be pulled at a high speed while controlling the oxygen concentration of the grown silicon single crystal and keeping it uniform in the radial direction.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 is a schematic cross-sectional view showing an example of a manufacturing apparatus according to the present invention.

  The manufacturing apparatus 1 includes a pulling furnace 2, a crucible support shaft 3 provided through the center of the bottom of the pulling furnace 2, a graphite crucible 4 b held at the upper end of the crucible support shaft 3, and a graphite crucible The quartz crucible 4a loaded in 4b, the heater 5 disposed in the pulling furnace 2 to heat the crucibles 4a, 4b and their surroundings from the surroundings, and the crucibles 4a, 4b and the heater 5 are concentrically surrounded. A rotating magnetic field device 6 provided outside the pulling furnace 2, a crucible support shaft drive mechanism 7 that moves the crucible support shaft 3 up and down, a seed chuck 9 that holds a seed crystal 8, and a seed chuck 9 that supports the seed chuck 9. Pull-up wire 10, wire winding mechanism 11, reverse cone-shaped radiant heat shield 13 provided to prevent heating of silicon single crystal 12 by radiant heat from heater 5 and crucibles 4 a and 4 b, and control device 14 and . The control device 14 controls operations of the rotating magnetic field device 6, the crucible support shaft drive mechanism 7, the wire winding function 11, a heater power source (not shown), and a gas supply / discharge mechanism.

  FIG. 2A is a perspective view conceptually showing the positional relationship and structure of the quartz crucible 4a, the rotating magnetic field device 6, and the radiant heat shield 13 in the manufacturing apparatus 1 shown in FIG.

  The rotating magnetic field device 6 is arranged concentrically so as to surround the crucible 4. As shown in FIG. 3, the rotating magnetic field device 6 has a substantially cylindrical electromagnet core 21, and 24 slots radially extending toward the outer circumferential surface are formed at equal pitches on the inner circumferential surface of the core 21. Has been. The core 21 is formed by laminating thin electromagnetic steel plates having a flat ring shape with internal teeth. A substantially ring-shaped copper winding core 22 having a vertical “U” shape is attached to the outer peripheral edge of the core 21, and the electric coils C <b> 1 to C <b> 24 are guided to the slots of the core 21 and further wound. The outer surface of the core 22 is wound around and wound around the core 21. (Coil No. is from C1 to C24 in the clockwise direction.) The core 21, the winding core 22, and the electric coils C1 to C24 are covered with a stainless steel cover 23. The teeth between the slots of the core 21 are magnetic poles, and the end faces thereof are opposed to the outer peripheral surface of the quartz crucible 4a through the furnace wall and the graphite crucible 4b.

  Of the electric coils C1 to C24, half (first group) electric coils C1, C2, C5, C6, C9, C10, C13, C14, C17, C18, C21, and C22 include power supply terminals TUa to A high frequency power supply circuit 25A (hereinafter referred to as power supply circuit 25A) that generates a high-frequency (design value: 10 Hz) three-phase AC voltage is connected via TWa, and the other half of each of the electric coils C1 to C24 (first Two groups of electric coils C3, C4, C7, C8, C11, C12, C15, C16, C19, C20, C23, and C24 have a low frequency (design value: 5 Hz) 3 through power supply terminals TUb to TWb. A low frequency power supply circuit 25B (hereinafter referred to as power supply circuit 25B) that generates a phase alternating voltage is connected.

  The power supply circuit 25A and the power supply circuit 25B are connected to the control circuit 26. The control circuit 26 gives a frequency command value FH corresponding to the high frequency instruction value fh input from the control device 14 and a coil voltage command value VdcA corresponding to the instruction current value iA to the power supply circuit 25A, and corresponds to the low frequency instruction value fL. The coil voltage command value VdcB corresponding to the frequency command value FL and the command current value iB is supplied to the power supply circuit 25B. The power supply circuit 25A uses the first frequency of the electric coils C1 to C24 via the power supply terminals TUa to TWa at a voltage value corresponding to the coil voltage command value VdcA with the high-frequency three-phase AC voltage indicated by the frequency command value FH. Apply to the group's electrical coil. In addition, the power supply circuit 25B uses a low-frequency three-phase AC voltage indicated by the frequency command value FL as a voltage value corresponding to the coil voltage command value VdcB through the power supply terminals TUb to TWb. Apply to the remaining second group of electrical coils.

  According to this manufacturing apparatus 1, the rotating magnetic field device 6 is controlled so that at least the rotational frequency, the rotational frequency, and the magnetic field strength in the plane perpendicular to the pulling direction of the silicon single crystal 12 are different. Is applied to the silicon melt 15 in the quartz crucible 4a, so that the speed is different between the central region of the quartz crucible 4a and the region outside thereof, as shown in FIG. 2 (c) and FIG. The silicon melt 15 can be moved. In addition, as shown in FIG. 5, the silicon melt 15 can be moved in different directions between the central region of the quartz crucible 4a and the outer region.

  As described above, the silicon melt 15 can be moved while changing the speed and direction between the central region of the quartz crucible 4a and the region outside thereof, so that the temperature gradient and velocity distribution in the surface and inside of the silicon melt 15 are obtained. The silicon single crystal 12 can be pulled up while appropriately controlling the above. Specifically, the temperature gradient in the vertical direction of the silicon melt 15 in the region immediately below the silicon single crystal 12 is made smaller than the temperature gradient under the crystal pulling condition by a normal CZ method without a rotating magnetic field, and the silicon single crystal The silicon single crystal 12 can be pulled up in a state where the temperature gradient in the radial direction on the surface of the silicon melt near the outer periphery of the silicon is larger than the temperature gradient under the crystal pulling condition by a normal CZ method without a rotating magnetic field. it can. By reducing the temperature gradient in the vertical direction of the silicon melt 15 in the region immediately below the silicon single crystal 12, heat transfer from the silicon melt 15 to the silicon single crystal 12 being pulled can be suppressed. By increasing the radial temperature gradient on the surface of the silicon melt 15 in the vicinity of the outer periphery of the silicon single crystal 12, it is possible to prevent deformation of the silicon single crystal 12 that is pulled up. At that time, since the radiant heat from the heater 5 and the quartz crucible 4a is blocked by the radiant heat shield 13, the heating of the silicon single crystal 12 due to the radiant heat is suppressed, so that the silicon single crystal 12 can be pulled up more quickly. Can be.

  Further, as shown in FIG. 6, the position P where the flow f1 of the surface of the silicon melt 15 from the center of the quartz crucible 4a to the outside and the flow f2 of the surface of the silicon melt 15 from the outside to the inside collide with each other. By controlling the generation of the rotating magnetic field MF so as to be located outside the silicon single crystal 12, not only the oxygen concentration of the grown silicon single crystal 12 but also the in-plane oxygen concentration distribution can be improved. .

  As described above, according to the manufacturing apparatus 1 of this embodiment, the radiant heat from the heater 5 and the crucibles 4a and 4b is shielded by the radiant heat shield 13, and the silicon melt 15 in the region immediately below the silicon single crystal 12 is shielded. The temperature gradient in the vertical direction is made smaller than the temperature gradient under the crystal pulling condition by the normal CZ method without a rotating magnetic field, and the temperature gradient in the radial direction on the surface of the silicon melt 15 near the outer periphery of the silicon single crystal 12 is rotated. Since the silicon single crystal 12 can be pulled up in a state where the temperature gradient is larger than the temperature gradient under the crystal pulling condition by the normal CZ method without the magnetic field MF, the oxygen concentration of the grown silicon single crystal 12 is controlled and It is possible to pull up the high-quality silicon single crystal 12 with little deformation at a high speed while keeping it uniform in the radial direction.

  On the other hand, the temperature gradient in the vertical direction of the silicon melt 15 in the region immediately below the silicon single crystal 12 is changed only by changing the rotation direction and strength of the rotating magnetic field MF applied to the silicon melt 15 as in the conventional MCZ method. Is made smaller than the temperature gradient under the crystal pulling condition by the normal CZ method without a rotating magnetic field, and the radial temperature gradient on the surface of the silicon melt 15 near the outer periphery of the silicon single crystal 12 is changed to the normal without the rotating magnetic field MF. Since it is impossible to make the temperature gradient larger than the temperature gradient under the crystal pulling condition of the CZ method, and the radiation heat shielding effect by the radiation heat shield 13 cannot be obtained, the oxygen concentration as in the manufacturing apparatus 1 of this embodiment It is impossible to pull up the high-quality silicon single crystal 12 with little deformation at a high speed while maintaining the same in the radial direction.

  In the above description, one control device 14 controls all the operations of the rotating magnetic field device 6, the crucible support shaft drive mechanism 7, the wire winding function 11, the heater power supply, and the gas supply / discharge mechanism. However, it goes without saying that a control device may be provided for each control target.

  Further, the structure of the rotating magnetic field device 6, the number of slots, the number of coils, the way of dividing the coils, the control method, etc. are arbitrary. For example, as another method of generating the plurality of rotating magnetic fields MF, there is a method of supplying a current superimposed with multi-frequency components formed by a computer and an inverter to the electric coils C1 to C24 of the rotating magnetic field device 6. it can.

Example 1
The silicon crystal having a diameter of 75 mm was pulled using the apparatus shown in FIG. A quartz crucible 4a having a diameter of 155 mm was used, and two types of rotating magnetic fields having different rotation frequencies were applied. The rotational frequency of the first rotating magnetic field is 50 Hz, and the rotating frequency of the second rotating magnetic field is 200 Hz. FIG. 7 shows the Lorentz force generated by the rotating magnetic field in the silicon melt 15 when both rotating magnetic fields are applied simultaneously. The rotation direction of the crucible 4a was 8 rpm in the direction opposite to the rotation direction of the rotating magnetic field, and the rotation speed of the silicon single crystal 12 was 10 rpm in the same direction as the crucible 4a.

  The average pulling speed of the straight body portion of the silicon single crystal 12 was 1.5 mm / min. On the other hand, the average pulling speed when using a similar pulling condition without using a rotating magnetic field was 0.8 mm / min. Further, when the rotation of the silicon single crystal 12 was 10 rpm in the direction opposite to the rotation direction of the crucible 4a without using a rotating magnetic field, the speed was 1.0 mm / min. In either case, only a lower pulling speed was obtained than when a rotating magnetic field was used.

Example 2
The effect of the present invention when pulling up a crystal having a diameter of 300 mm was confirmed by numerical simulation. The diameter of the crucible 4a was 711 mm (28 inches). The applied rotating magnetic field is that of FIG. 8, the frequency of the first rotating magnetic field is 25 Hz, and the frequency of the second rotating magnetic field is 50 Hz. The silicon single crystal 12 and the crucible 4a were rotated at 6 rpm and 3 rpm, respectively, in the direction opposite to the rotating direction of the rotating magnetic field. 9 and 10 show the flow of the silicon melt 15 in the crucible 4a at this time. FIG. 9 shows the flow in the vicinity of the surface of the silicon melt 15 and the flow immediately below the silicon single crystal 12, but the silicon melt 15 is transferred to the crucible 4 a and the crystal by a rotating magnetic field where the silicon single crystal 12 is not in contact. It turns out that it is rotating in the opposite direction to 12. FIG. 10 shows the flow inside the melt 15. The vector in the figure indicates the flow of the melt, and the shade indicates the temperature distribution. The flow generated by the rotating magnetic field dominates the flow of the entire melt, and the hot melt in contact with the crucible is carried near the crystal near the surface of the melt, steepening the horizontal temperature gradient near the crystal. . As a result, an estimated pulling speed of 1.3 mm / min was obtained.

  As a comparison, a simulation was also performed under the condition where no rotating magnetic field was applied. As conditions, the rotational speed of the crucible 4a, which was one of the fastest pulling speeds obtained by experiments, was 6 rpm, and the crystal rotation of the silicon single crystal 12 was −10 rpm in the reverse direction. The simulation results are shown in FIGS. 11 and 12, and the flow of the silicon melt 15 is divided into a flow by the crucible 4 a and a flow by the crystal 12. As a result, the flow is complicated, and the temperature gradient in the horizontal direction in the vicinity of the crystal 12 is smaller than that when a rotating magnetic field is used, as shown in FIG. The estimated pulling speed by simulation is 1.0 mm / min, which is in good agreement with the experimental results, but is 20% or more lower than when a rotating magnetic field is used.

Schematic sectional view showing an example of a manufacturing apparatus according to the present invention (A) is a principal part perspective view of the manufacturing apparatus concerning this invention. (B) is a transition diagram which shows the change of a rotating magnetic field. (C) is a perspective sectional view which illustrates the flow rate distribution control state of the silicon melt by a rotating magnetic field. Configuration diagram illustrating structure of rotating magnetic field device Plan view illustrating flow velocity distribution control state of silicon melt by rotating magnetic field Plan view illustrating flow velocity distribution control state of silicon melt by rotating magnetic field (A) Plan view illustrating flow control state of silicon melt by rotating magnetic field (b) Cross-sectional view illustrating flow control state of silicon melt by rotating magnetic field The figure which shows the relationship between the driving force (Lorentz force) given to a melt by the rotating magnetic field used in Example 1, and the distance from the crucible center. The figure which shows the relationship between the driving force (Lorentz force) given to a melt by the rotating magnetic field used in Example 2, and the distance from the crucible center. The top view which shows the flow of the silicon melt in Example 2. Sectional drawing which shows the flow of the silicon melt in Example 2 The top view which shows the flow of the silicon melt in a comparative example Sectional drawing which shows the flow flow of the silicon melt in a comparative example The figure which shows the temperature gradient of the horizontal direction in the melt surface vicinity of Example 2 and each comparative example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 2 Pulling furnace 3 Crucible support shaft 4a Quartz crucible 4b Graphite crucible 5 Heater 6 Rotary magnetic field apparatus 7 Crucible support shaft drive mechanism 8 Seed crystal 9 Seed chuck 10 Pulling wire 11 Wire winding mechanism 12 Silicon single crystal 13 Radiation heat Shield 14 Control device 15 Silicon melt MF Rotating magnetic field f1 Flow from inside to outside f2 Flow from outside to inside

Claims (7)

In an apparatus for producing a silicon single crystal by the Czochralski method,
A crucible containing a silicon melt;
A heater for heating the crucible from the surroundings;
A radiant heat shield provided to prevent heating of the silicon single crystal due to radiant heat from the heater and the crucible;
A rotating magnetic field apparatus for applying a plurality of rotating magnetic fields having different rotating frequencies among the rotating direction, rotating frequency and magnetic field strength in a plane perpendicular to the pulling direction of the silicon single crystal to the silicon melt in the crucible; ,
An apparatus for producing a silicon single crystal, comprising: The rotating magnetic field device includes:
In order to reduce the vertical temperature gradient of the silicon melt in the region immediately below the silicon single crystal, and to increase the radial temperature gradient on the surface of the silicon melt near the outer periphery of the silicon single crystal. The manufacturing apparatus according to claim 1, wherein the rotating magnetic field is generated. The rotating magnetic field device includes:
The plurality of positions are such that the position where the flow of the silicon melt surface from the center of the crucible toward the outside and the flow of the silicon melt surface from the outside to the inside collide with each other are outside the silicon single crystal. The manufacturing apparatus according to claim 1, wherein the rotating magnetic field is generated. The rotating magnetic field device includes:
The manufacturing apparatus according to claim 1, wherein the plurality of rotating magnetic fields are controlled so that the rotation frequency is 1 Hz or more and 1000 Hz or less. The rotating magnetic field device includes:
5. The manufacturing apparatus according to claim 1, wherein the plurality of rotating magnetic fields are controlled so that a maximum rotation speed of the silicon melt is 1 rpm or more and 200 rpm or less. A crucible containing a silicon melt;
A heater for heating the crucible from the surroundings;
A radiant heat shield provided to prevent heating of the silicon single crystal due to radiant heat from the heater and the crucible;
A rotating magnetic field apparatus for applying a plurality of rotating magnetic fields having different rotating frequencies among the rotating direction, rotating frequency and magnetic field strength in a plane perpendicular to the pulling direction of the silicon single crystal to the silicon melt in the crucible; A method for producing a silicon single crystal by the Czochralski method using a production apparatus comprising:
While the radiant heat from the heater and the crucible is shielded by a radiant heat shield, the rotating magnetic field device applies a rotating magnetic field to the silicon melt in the crucible so that the direction of the center region of the crucible and the region outside the crucible A method for producing a silicon single crystal, wherein the silicon single crystal is pulled up while moving the silicon melt at different speeds. The rotational frequency of the rotating magnetic field is 10 Hz or more and 200 Hz or less,
The direction of rotation of the rotating magnetic field is opposite to the direction of rotation of the crucible,
The direction of rotation of the rotating magnetic field is opposite to the direction of rotation of the silicon single crystal;
The rotational speed of the crucible is 1 rpm or more and 12 rpm or less,
The method for producing a silicon single crystal according to claim 6, wherein the rotation speed of the silicon single crystal is 0.1 rpm or more and 20 rpm or less.