JP2005272245A - Silicon single crystal pulling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single crystal pulling device capable of controlling the temperature distribution in a crystal side radial direction in a single crystal silicon with a simple structure and without deteriorating an essential function of a radiation shield and capable of manufacturing a high quality single crystal even if pulling is quickened. <P>SOLUTION: The single crystal pulling device is mounted with a reflection plate consisting of a high reflectivity member and whose section is a concave shape and a ring shape at the inside of the radiation shield used for pulling the single crystal in a Czockralski method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a silicon single crystal pulling apparatus, and more particularly to a silicon single crystal pulling apparatus having an improved radiation shield structure.

  In general, a silicon single crystal is mainly used for a substrate of a semiconductor device. This silicon single crystal is manufactured from polycrystalline silicon by the Czochralski method (hereinafter referred to as CZ method).

  As shown in FIG. 6, in this CZ method, a quartz glass crucible 22 installed in a single crystal pulling apparatus 21 is filled with polysilicon as a raw material, and polysilicon is formed by a heater 23 provided on the outer periphery of the quartz glass crucible 22. The seed crystal attached to the seed chuck is immersed in the melt M, and the seed chuck is pulled up while rotating the seed chuck and the quartz glass crucible 22 in the same direction or in the opposite direction to grow a single crystal Ig. It is.

  The single crystal pulling device 21 is provided with a radiation shield 24 around the single crystal pulling region above the silicon melt. The radiation shield 24 has a lower opening 24d having a diameter larger than that of the upper opening 24u. It has a small frustoconical cylinder. The radiation shield 24 is used for the purpose of controlling the temperature gradient in the vertical direction in the crystal and blocking radiant heat from the melt in order to improve the pulling speed of the single crystal silicon.

  However, in the conventional radiation shield, the temperature distribution in the single crystal has a difference in temperature distribution between the center and the outer periphery as the pulling speed increases. That is, a temperature gradient occurs in which the temperature is high in the center of the crystal and the temperature is low in the outer periphery of the crystal. On the contrary, if the temperature gradient in the radial direction of the single crystal is made uniform, the pulling speed must be suppressed, and it has been difficult to improve both of them without impairing both. In addition, the conventional radiation shield increases the pulling speed by using this, and shortens the passage time by shortening the temperature band width of 1100 ° C. to 1000 ° C. which is the void forming temperature band, but the pulling speed is high. If it is faster, the temperature gradient in the radial direction of the single crystal increases, and the region of the single crystal at 1100 ° C. to 1000 ° C. shifts more to the melt side, making it difficult to shorten the passage time.

  In addition, Patent Document 1 proposes a single crystal pulling apparatus configured to provide a ring-shaped heat insulating material at the lower and upper ends of the radiation shield so as to lower the heat insulating performance in the intermediate portion. By controlling the temperature distribution in the single crystal silicon, the apparatus does not allow an increase in the temperature gradient in the crystal side diameter direction and shorten the pulling time even if the pulling speed is increased.

Further, Patent Document 2 proposes a single crystal pulling apparatus having a radiation shield provided with a metal reflecting member coated with ring-shaped quartz at the lower end. This apparatus is applied to a predetermined part where the temperature is to be controlled. The radiant heat cannot be reflected reliably. Further, Patent Document 3 proposes a single crystal pulling apparatus in which a cooling member is provided inside the radiation shield. This apparatus controls the pulling speed by controlling the temperature distribution in single crystal silicon. Even if it is made faster, the increase in temperature gradient in the crystal side diameter direction is suppressed, and the pulling time cannot be shortened.
Japanese Patent Laid-Open No. 9-202687 (paragraphs [0008] and [0012], FIG. 2) JP 11-236294 A (paragraphs [0018], [0031], FIG. 1) JP 2001-220289 A (paragraph [0034], FIG. 6)

  The present invention has been made in consideration of the above-described circumstances, and can control the temperature distribution in the crystal side radial direction in single crystal silicon without compromising the original function of the radiation shield. An object of the present invention is to provide a silicon single crystal pulling apparatus capable of producing a high quality single crystal even if the upper speed is increased.

  To achieve the above object, according to one aspect of the present invention, a chamber, a quartz glass crucible provided in the chamber and containing raw silicon, a heater for heating the quartz glass crucible from the surroundings, A radiation shield provided above a quartz glass crucible and having an opening through which a silicon single crystal penetrates, a pulling wire penetrating the radiation shield and having a seed chuck attached thereto, and a wire rotating device for raising and lowering the wire A silicon single crystal pulling apparatus is provided, characterized in that a ring-shaped reflecting plate made of a highly reflective member and having a concave cross section is attached to the inside of the radiation shield. As a result, a silicon single crystal pulling apparatus capable of controlling the temperature distribution in the single crystal silicon and producing a high quality single crystal without compromising the original function of the radiation shield is realized. .

  In a preferred example, the radiation shield includes a hollow frustoconical shield main body, a ring-shaped horizontal portion extending inwardly from the shield main body, and an upright portion rising upward from the horizontal portion into a ring shape, The reflector has a ring-shaped attachment portion extending outward from the shield main body, and the reflector is attached to the upright portion.

  In another preferred example, the reflector is attached to the upright portion of the radiation shield, and a ring-shaped heat insulating material is attached to a space between the shield main body, the horizontal portion, and the upright portion.

  Hereinafter, an embodiment of a silicon single crystal pulling apparatus according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a conceptual diagram of an embodiment of a single crystal pulling apparatus according to the present invention.

  As shown in FIG. 1, a single crystal pulling apparatus 1 according to the present invention holds a chamber 2, a quartz glass crucible 3 installed in the chamber 2 and filled with a semiconductor raw material, and the quartz glass crucible 3. A graphite crucible 4, a heater 5 surrounding the graphite crucible 4 and heating the semiconductor raw material of the quartz glass crucible 3 to melt M, and attached to the graphite crucible 4 through the bottom 6 of the chamber 2 and passing through a motor ( And a crucible rotating shaft 7 which is connected to and rotated by a lifting device (not shown).

  Further, in the single crystal pulling apparatus 1, a pulling wire 10 to which a seed chuck 9 for holding a single crystal pulling seed 8 is attached is provided above the quartz glass crucible 3. Is provided outside the chamber 2 and is driven by a motor (not shown) and is attached to a wire rotating device so as to be wound or released, and the wire 10 can be moved up and down.

Furthermore, it has a radiation shield 11 installed so as to surround the pulling region above the quartz glass crucible 3 and rectifying the flow of the inert gas G and provided with an opening 11a ₁ through which the single crystal Ig passes. Further, an inert gas supply port 12 is provided above the chamber 2, and an inert gas discharge port 13 is provided at the bottom 6 of the chamber 2.

As shown in FIG. 2, the radiation shield 11 is made of a graphite base material having low thermal conductivity and excellent heat insulation, and the surface thereof is covered with silicon carbide so as to maintain a clean atmosphere. 11a ₁ is provided so as to surround the single crystal Ig and is a hollow cylindrical shape, for example, a hollow truncated conical shield main body 11a, a ring-shaped horizontal portion 11b extending inwardly from the shield main body 11a, and the horizontal It has a raised portion 11c that rises in a ring shape upward along the single crystal from the portion 11b, and a ring-shaped attachment portion 11d that extends outward from the shield main body 11a.

  The radiation shield 11 is provided with a reflection plate 13 on the inner side near the lower portion thereof, that is, on the upper side in the vicinity of the horizontal portion 11b. As shown in FIG. Has a concave shape of a curved surface having a predetermined curvature, and has a ring shape, for example, a bottomless bowl shape.

  The reflection plate 13 is provided with, for example, six attachment members 13a. As shown in FIGS. 2 and 4, the reflection plate 13 is attached to the radiation shield 11 by fitting the attachment member 13a into the upright portion 11c. A ring-shaped air passage 13b through which a part of the inert gas passes is formed between the mounting member 13a and the upright portion 11c so that the inert gas flows without stagnation. It has become.

  The radiation shield 11 has the structure as described above, has a simple structure, and can be easily controlled in temperature distribution in single crystal silicon by being attached to an existing radiation shield. Since attachment and detachment are easy, cleaning work etc. can be performed easily.

  Next, a single crystal pulling method using the single crystal pulling apparatus according to the present invention will be described.

  As shown in FIG. 1, raw material polysilicon is filled in a quartz glass crucible 3, an inert gas G is caused to flow into the chamber 2 from an inert gas supply port 12 above the chamber 2, and the heater 5 is energized. Then, the quartz glass crucible 3 is heated, the crucible rotating motor is energized, and the quartz glass crucible 3 is rotated by the crucible rotating shaft 7 coupled to the motor.

  After a certain time has elapsed, the wire rotating device is rotated to lower the pulling wire 10, the seed chuck 9 is lowered, the seed 8 is brought into contact with the silicon melt M, the crystal is grown, and the single crystal Ig is pulled up. .

  In such a silicon single crystal pulling step, the inert gas G supplied from the inert gas supply port 12 above the chamber 2 is rectified by the upright portion 11c and radiated with the reflector 13 attached thereto. Passing between the shield 11 and the single crystal Ig, heat from the melt surface to the single crystal Ig is blocked by the presence of the horizontal portion 11b, and the inert gas G reaches the surface of the melt M. The oxide that evaporates from the surface of the melt M is captured by the inert gas G that flows on the melt surface. The inert gas G containing oxide passes between the outside of the radiation shield 11 and the quartz glass crucible 3 and is discharged from the inert gas discharge port 13 to the outside of the chamber 2. Thus, the radiation shield 11 performs its original function without impairing its original function.

  In the silicon single crystal pulling step, as shown in FIG. 5, the curvature radius (focal length of the reflecting plate) of the concave curved surface of the reflecting plate 13 is the focal point of the reflecting plate at a portion where the temperature of the silicon single crystal Ig is to be controlled. Therefore, the radiation shield 11 cuts off the radiant heat applied to the silicon single crystal Ig from the heater 5 and the melt M, and the radiant heat emitted from the silicon single crystal Ig is reflected by the reflecting plate 13 having a concave cross section. The crystal Ig is reflected to the part where the temperature is desired to be controlled. As a result, the temperature distribution in the radial direction in the single crystal silicon can be controlled, and the presence of the reflecting plate 13 reflects and concentrates the radiant heat generated from the silicon single crystal Ig. While the outer periphery is heated to control the temperature, the temperature region of 1100 ° C. to 1000 ° C. existing in the upper part of the reflector 13 can be shifted upward. Shifting upward moves away from the melt, so that the cooling effect is increased, and as a result, the passage time can be reduced.

  Further, it is more preferable to spread a heat insulating material in a space 11e surrounded by the shield main body 11a, the horizontal portion 11b, and the upright portion 11c to improve the heat insulating effect of the radiation shield 11. By laying the heat insulating material in the space 11e in this way, the radiant heat from the melt can be further blocked, so that the temperature region passage time of 1100 ° C. to 1000 ° C. existing above the reflector 13 can be further reduced.

  The silicon single crystal pulling apparatus can control the temperature gradient in the crystal diameter direction in single crystal silicon by providing a concave ring-shaped reflector inside the conventional radiation shield. Even if the upper speed is increased, a highly crystalline single crystal can be produced.

  Note that the silicon single crystal pulling apparatus of the present invention is not limited to the above-described embodiment, and for example, a separate attachment portion may be provided on the radiation shield, and the reflection plate may be attached so as to be engaged therewith.

  As described above, according to the silicon single crystal pulling apparatus of the present embodiment, the temperature distribution in the radial direction in the single crystal silicon can be controlled without damaging the original function of the radiation shield with a simple structure, Even if the pulling speed is increased, a high-quality single crystal can be produced.

  Using the silicon single crystal pulling apparatus of the present invention as shown in FIG. 1, the silicon single crystal was pulled under the conditions shown in Table 1. Next, the pulled silicon single crystal ingot is sliced, lapped, etched, and polished to produce a single-sided mirror wafer having a thickness of 725 μm, and the LSTD (Laser Scattering Tomography Defect) density of the mirror surface is determined from the wafer center and the wafer outer periphery. Example 1 (measurement point 4, outer peripheral bevel part 5 mm).

  Next, in the silicon single crystal pulling apparatus of the present invention, the reflector is fitted into the upright portion in a state where a circular heat insulating material is spread in the space of the radiation shield (reference numeral 11e in FIG. 1), and the same as in the first embodiment. The silicon single crystal was pulled under the conditions described above, and LSTD was evaluated by the same method (Example 2).

Further, as Comparative Example 1, the silicon single crystal was pulled up without installing the reflector shown in FIG. 1 and evaluated under the same conditions as in Example 1.

  As can be seen from Table 2, in Example 1, the LSTD density is decreased as compared with Comparative Example 1, and the difference between the central portion and the outer peripheral portion is also reduced, and the in-plane uniformity is improved. I was able to confirm. Moreover, in Example 2, it has confirmed that the reduction effect of the LSTD density was acquired rather than Example 1 by providing a heat insulating material.

The conceptual diagram of one Embodiment of the single crystal pulling apparatus which concerns on this invention. The conceptual diagram which shows a part of radiation shield and reflector which are used for the single crystal pulling apparatus which concerns on this invention. The perspective view of the reflecting plate used for the single crystal pulling apparatus which concerns on this invention. Sectional drawing which shows the removal state of the reflecting plate used for the single crystal pulling apparatus which concerns on this invention. The conceptual diagram which shows the use condition of one Embodiment of the single crystal pulling apparatus which concerns on this invention. The conceptual diagram of the conventional single crystal pulling apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Single crystal pulling apparatus 2 Chamber 3 Quartz glass crucible 4 Graphite crucible 5 Heater 10 Pulling wire 11 Radiation shield 11a Shield main body 11b Horizontal portion 11c Upright portion 11d Mounting portion 11e Space 13 Reflecting plate 13a Mounting member 13b Air passage

Claims (3)

A chamber, a quartz glass crucible provided in the chamber and containing raw silicon, a heater for heating the quartz glass crucible from the periphery, and an opening provided above the quartz glass crucible and through which the silicon single crystal passes are formed. A radiation wire, a pulling wire that penetrates the radiation shield and has a seed chuck attached thereto, and a wire rotating device that raises and lowers the wire. The radiation shield is made of a highly reflective member. A silicon single crystal pulling apparatus, characterized in that a ring-shaped reflector is attached with a concave cross section. The radiation shield includes a hollow frustoconical shield main body, a ring-shaped horizontal portion extending inwardly from the shield main body, an upright portion rising upward from the horizontal portion into a ring shape, and an outer portion from the shield main body. The silicon single crystal pulling apparatus according to claim 1, further comprising a ring-shaped attachment portion extending in the direction, wherein the reflector is attached to the upright portion. The said reflecting plate is attached to the said upright part of the said radiation shield, The ring-shaped heat insulating material was attached to the space of a shield main body, a horizontal part, and an upright part, The Claim 1 or 2 characterized by the above-mentioned. Silicon single crystal pulling device.

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