JP4351976B2 - Seed crystal holding device and silicon single crystal pulling method using the same - Google Patents

Description

  The present invention relates to a seed crystal holding device used when pulling up a crystal from a melt by the Czochralski method and a silicon single crystal pulling method using the seed crystal holding device.

  The growth of a silicon single crystal by the Czochralski method (CZ method) is performed by putting polysilicon as a raw material in a quartz crucible, heating and melting it, immersing a seed crystal in the surface of this silicon melt, and then gradually pulling it up. This is done by growing a silicon single crystal.

  At that time, it is important that the seed crystal is in contact with the liquid surface while maintaining an accurate vertical direction on the liquid surface. If the seed crystal is in contact with the liquid surface at an angle, it will be a major factor in reducing the single crystallization rate. Furthermore, the seed crystal under load gradually increases the non-uniformity of stress at the contact portion of the holder, causing an accident that the seed crystal is broken and dropped during the growth process of the silicon single crystal. For this reason, many seed crystal support methods or support devices that solve the above problems have been proposed.

  The seed crystal support method that has been widely used heretofore is a method of supporting a seed crystal by making a hole on the center axis of the seed crystal and inserting it into the hole of the holder and the hole of the seed crystal with a support pin. However, recently, the diameter of single crystals has increased and the weight has increased. As a result, due to the increase in weight due to the growth of the single crystal at the tip of the seed crystal, the stress due to the load concentrates in the hole of the central axis of the seed crystal during the single crystal growth process or the single crystal cooling process, and the seed crystal breaks and falls. There was an accident.

  In order to solve this problem, a seed crystal support device other than the support pin method has been proposed (for example, see Patent Document 1).

  As an example, Patent Document 1 proposes a single crystal pulling apparatus shown in FIG.

As shown in FIG. 3 on page 5, the seed crystal 8 is inserted into the holder 7 fitted with the holding ring 15 having the tapered surface 18 so that the tapered surface 18 and the minimum diameter portion 22 of the seed crystal 8 are in contact with each other. The seed crystal 8 is supported by the holding ring 15. In this way, the stress is dispersed to contact with the tapered surface, and the seed crystal 8 is stably supported at the set position with the large contact surface.
JP-A-10-29892 (page 3, right column, line 26 to column 44)

  By the way, in the seed crystal support device shown in Patent Document 1, in consideration of the practical processing accuracy of the seed crystal and the taper portion on the inner peripheral surface of the holding ring, the adaptability to the seed crystal having various diameters is improved. In order to raise, it is said that it is preferable to form a morning glory taper surface in which the inclination angle of the holding ring inner peripheral surface taper increases upward.

  However, in the case of a morning glory-shaped tapered inner peripheral surface whose inclination angle increases upward, contact with seed crystals having various diameters is improved, but at the same time, the degree of freedom and flexibility are increased. As a result, the frequency at which the seed crystal tilts also increases, and as a result, the stress concentration caused by the tilt of the seed crystal causes the silicon single crystal being grown to fall.

  The present invention has been made to solve the above-described problems, and prevents damage to the seed crystal by dispersing the stress applied to the single crystal support so as to cope with the pulling of a large single crystal. It is an object of the present invention to provide a seed crystal support device in which a central axis of a crystal can be easily set and a silicon single crystal pulling method using the seed crystal support device.

  According to one aspect of the present invention, there is provided a seed crystal holding device for pulling a silicon single crystal formed by forming a tapered portion from a large diameter portion to a small diameter portion, wherein the seed crystal can be inserted, and the seed crystal A cylindrical body whose one end is reduced in diameter so as to come into surface contact with the taper portion of the lower portion, a flange portion is formed on the other end side, and a screw is formed on the outer peripheral portion, and a large diameter portion of the seed crystal is inserted. And a substantially frustoconical ring body placed on the flange portion of the lower holder, and a connecting portion connected to the crystal pulling wire, and a hood body having a substantially cross-sectional C shape connected to the connecting portion. A seed crystal holding device comprising: an upper holder that is in contact with the conical surface of the ring body at an inner peripheral wall of the hood body, and is formed with a screw that is screwed into the lower holder in the vicinity of the edge of the hood body. Is provided.

  According to another aspect of the present invention, there is provided a seed crystal holding device for pulling a silicon single crystal formed by forming a tapered portion from a large diameter portion to a small diameter portion, and the seed crystal can be inserted. The cylindrical body is composed of a large-diameter portion, a first reduced-diameter portion, a small-diameter portion, and a second reduced-diameter portion. A screw is formed on the inner periphery of one end of the large-diameter portion, and the second reduced-diameter portion. And a lower holder that is in surface contact with the tapered portion of the seed crystal, and a substantially frustoconical shape that is formed so as to pass through the large-diameter portion of the seed crystal and to be positioned and in contact with the first reduced diameter portion of the lower holder. A ring body and a bottomed cylindrical body into which the large-diameter portion of the seed crystal can be inserted, and having a flange portion for pressing the conical surface of the ring body against the first reduced diameter portion at one end; A screw that is screwed to the lower holder is formed on the outer periphery spaced from the upper holder, and a connecting portion that is connected to the crystal pulling wire is formed. Seed crystal holding device, characterized in that it consists of and da, is provided.

  Further, according to another aspect of the present invention, the seed crystal holding device for pulling silicon crystal formed by forming a tapered portion from the large diameter portion to the small diameter portion, the seed crystal can be inserted, A cylindrical body whose one end is reduced in diameter so as to come into surface contact with the tapered portion of the seed crystal, a flange portion is formed on the other end side, and a screw is formed on the outer periphery, and a large diameter of the seed crystal A substantially frustoconical ring body that is inserted in the flange portion of the lower holder and a connecting portion that is connected to the crystal pulling wire, and a hood body that has a substantially cross-sectional shape and is connected to the connecting portion. And an upper holder that is in contact with the conical surface of the ring body at the inner peripheral wall of the hood body and is formed with a screw that is screwed into the lower holder in the vicinity of the edge of the hood body. , Grow a silicon single crystal by bringing a seed crystal into contact with the silicon melt Pulling a silicon single crystal wherein the door is provided.

  According to the seed crystal holding device of the present invention, the stress applied to the single crystal support is dispersed, the seed crystal is prevented from being damaged, and the center crystal tilt deviation of the seed crystal can be corrected. It can handle pulling and can improve the yield of single crystals.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same portions are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic cross-sectional view showing a configuration of a seed crystal holding device according to an embodiment of the present invention. In the seed crystal held by the seed crystal holding device according to the embodiment of the present invention, a tapered portion 5 is formed from a large diameter portion having a large diameter to a small diameter portion having a small diameter. In FIG. 1, the seed crystal holding device is roughly divided into an upper holder 1 and a lower holder 2. Both the upper holder 1 and the lower holder 2 have a substantially cylindrical shape, and can be fitted by screw connection. The lower holder 2 can be inserted with the seed crystal 3 described above, and has one end reduced in diameter so as to come into surface contact with the taper portion 5 of the seed crystal 3 and has a narrowed shape. A flange portion 2a is formed on the other end side of the lower holder 2 (upper side in FIG. 1). A screw 2 b is formed on the outer peripheral portion of the lower holder 2. Further, the upper portion of the upper holder 1 has a tapered shape and has a connecting portion 1 a that is connected to the crystal pulling wire 7. The upper holder 1 forms a hood body 1b having a substantially cross-sectional shape that is continuous with the connecting portion 1a. The inner peripheral wall of the hood body 1b has an inclined surface as shown in FIG. Further, the screw 1c described above is formed in the vicinity of the edge of the hood body 1b. The seed crystal holding device is provided with a holding ring 6 for guiding the central axis of the seed crystal 3 in the vertical direction. The holding ring 6 is inserted through the large-diameter portion of the seed crystal 3 and is placed on the flange portion 2a of the lower holder 2, and has a substantially truncated cone shape. As shown in FIG. 1 (d), the retaining ring 6 is divided into three small pieces. The number of small pieces is not limited to 3, but may be 2 or more. The outer peripheral inclined surface of the holding ring 6 and the upper inner peripheral inclined surface of the upper holder 1 have substantially the same inclination angle. With this configuration, as the upper holder 1 and the lower holder 2 are fitted, the outer peripheral inclined surface of the holding ring 6 is pressure-bonded to the upper inner peripheral inclined surface of the upper holder 1, and the seed crystal 3 The central axis of is guided vertically. The retaining ring 6 is preferably a divided body because it can provide a degree of freedom with respect to some variation in the seed crystal diameter, and it can be easily moved during crimping. In addition, it is preferable to join the upper holder 1 and the lower holder 2 by screw connection because it is easy to adjust the degree of pressure bonding, but it goes without saying that other joining methods can be used.

  Another embodiment of the present invention will be described with reference to FIG. As shown in FIG. 2, the seed crystal holding device is roughly divided into an upper holder 1 and a lower holder 2. Both the upper holder 1 and the lower holder 2 have a cylindrical shape and can be fitted by screw connection. The lower holder 2 is a cylindrical body through which the seed crystal 3 can be inserted, and is composed of a large diameter portion 2a, a first reduced diameter portion 2b, a small diameter portion 2c, and a second reduced diameter portion 2d, and the large diameter portion 2a. A screw 2e is formed on the inner periphery of the one end of the first and second surfaces of the seed crystal 3 so as to come into surface contact with the second reduced diameter portion 2d. The upper holder 1 is a bottomed cylindrical body into which the large-diameter portion of the seed crystal 3 can be inserted, and a flange portion for pressing a conical surface of a holding ring 6 (described later) against the first reduced-diameter portion 2b at one end portion. A screw 1c that is screwed into the lower holder 2 is formed on the outer periphery that has 1b and is spaced from the flange portion 1b, and a connecting portion 1a that is connected to the crystal pulling wire 7 is formed. The holding ring 6 is formed in a substantially truncated cone shape so as to pass through the large-diameter portion of the seed crystal 3 and to be positioned and in contact with the first reduced-diameter portion 2 b of the lower holder 2.

  The inclination of the outer peripheral portion of the holding ring 6 and the inner peripheral inclination of the first reduced diameter portion 2b of the lower holder 2 have substantially the same inclination angle. With this configuration, as the upper holder 1 and the lower holder 2 are fitted together, the outer peripheral inclined surface of the holding ring 6 is pressure-bonded to the upper end tapered surface of the lower holder 2, and the center of the seed crystal 3 is Guide the shaft vertically. The retaining ring 6 is preferably a divided body because it can provide a degree of freedom with respect to some variation in the seed crystal diameter, and it can be easily moved during crimping.

  Furthermore, another embodiment of the present invention will be described with reference to FIG. As shown in FIG. 3, a cushioning material 8 is interposed around a large diameter portion of the seed crystal 3 surrounded by the holding ring 6 and the upper and lower holders. Since the holding ring 6 and the seed crystal 3 are not in direct contact with each other, the seed crystal 3 can be prevented from being damaged due to thermal expansion at a high temperature, and the outer peripheral inclined surface of the holding ring 6 is pressure-bonded to the upper end tapered surface of the upper holder 1. At this time, it is easy to guide the central axis of the seed crystal 3 in the vertical direction.

  Next, a method for setting a seed crystal holding device according to an embodiment of the present invention will be described in detail with reference to FIGS.

  First, the seed crystal 3 is inserted into the cylindrical lower holder 2. At this time, the seed crystal 3 is held by the contact between the seed crystal taper portion 5 and the taper portion 4 of the lower holder 2, but the central axis of the seed crystal 3 tends to be inclined. Next, the holding ring 6 is installed on the upper end of the lower holder 2 so that the diameter details are upward. When the lower holder 2 is screwed into the upper holder 1 with a screw groove in this state, the outer peripheral inclined portion of the holding ring 6 comes into contact with the upper inner peripheral surface of the upper holder 1 so that the holding ring 6 is pushed inward. As the holding ring 6 and the seed crystal 3 come into contact with each other, the deviation of the central axis of the seed crystal 3 is gradually corrected.

  When the lower holder 2 is screwed into the upper holder 1 until it cannot be screwed, the holding ring 6 and the upper inner peripheral surface of the upper holder 1 and the seed crystal 3 are almost in contact at this point, whereby the seed crystal The center axis misalignment of 3 has been corrected.

  For a seed crystal having a large diameter portion of φ30 mm, a small diameter portion of φ20 mm, and an inclined portion length of 30 mm, the seed crystal support jig according to the conventional taper surface contact support method and the seed crystal support device according to the embodiment of the present invention are used. Compared.

  As a comparative example, when supporting only with an inclined portion having a curvature, the seed crystal center of 2 ° at the maximum with respect to the center axis of the seed crystal support jig, although there are individual differences in the processing state of the seed crystal and differences in the degree of attachment. Axial misalignment was observed.

  On the other hand, in the seed crystal support device according to the embodiment of the present invention, the maximum tilt was 0.4 °.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

It is a schematic sectional drawing which shows the structure of the seed crystal holding | maintenance apparatus which concerns on one Embodiment of this invention. It is a schematic sectional drawing which shows the structure of the seed crystal holding | maintenance apparatus which concerns on other embodiment of this invention. It is a schematic sectional drawing which shows the structure of the seed crystal holding | maintenance apparatus which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Upper holder, 2 ... Lower holder, 3 ... Seed crystal, 4 ... Tapered part,
5 ... Tapered portion, 6 ... Retaining ring, 7 ... Pull-up wire, 8 ... Buffer material.

Claims (5)

A seed crystal holding device for pulling a silicon single crystal formed by forming a tapered portion from a large diameter portion to a small diameter portion,
A lower holder in which the seed crystal can be inserted, a cylindrical body whose one end is reduced in diameter so as to come into surface contact with the tapered portion of the seed crystal, a flange is formed on the other end, and a screw is formed on the outer periphery When,
A substantially frustoconical ring body that is inserted through the large diameter portion of the seed crystal and placed on the flange portion of the lower holder;
A hood body having a substantially cross-sectional C-shape that is connected to the crystal pulling wire, and is in contact with the conical surface of the ring body at the inner peripheral wall of the hood body; A seed crystal holding device comprising: an upper holder formed with a screw to be screwed into the lower holder in the vicinity thereof. A seed crystal holding device for pulling a silicon single crystal formed by forming a tapered portion from a large diameter portion to a small diameter portion,
A cylindrical body through which the seed crystal can be inserted, comprising a large-diameter portion, a first reduced-diameter portion, a small-diameter portion, and a second reduced-diameter portion, and a screw is formed on the inner periphery of one end portion of the large-diameter portion. A lower holder in surface contact with the tapered portion of the seed crystal at the second reduced diameter portion;
A substantially frustoconical ring body formed so as to pass through the large-diameter portion of the seed crystal and to be positioned and in contact with the first reduced-diameter portion of the lower holder;
A bottomed cylindrical body into which the large-diameter portion of the seed crystal can be inserted, an outer periphery having a flange portion for pressing the conical surface of the ring body against the first reduced-diameter portion at one end portion and spaced from the flange portion A seed crystal holding device comprising: an upper holder formed with a screw to be screwed to the lower holder, and an upper holder formed with a connecting portion connected to a crystal pulling wire.   The seed crystal holding device according to claim 1 or 2, wherein the ring body is formed by being divided into two or more small pieces.   The seed crystal holding device according to claim 1, further comprising a buffer material that covers an outer periphery of a large-diameter portion of the seed crystal.   5. A silicon single crystal pulling method comprising growing a silicon single crystal by bringing a seed crystal into contact with a silicon melt using the seed crystal holding device according to claim 1.

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