JP2013010646A - Single crystal pulling apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single crystal pulling apparatus capable of restraining both generation of grow-in defects and dislocation of a crystal in manufacturing a silicon single crystal by the Czochralski method.SOLUTION: This apparatus includes a cooling cylinder 7 which is open at the upper side and the under side and installed over a crucible 3 and wrapping and cooling the pulled-up single crystal C. On the inner side of the cooling cylinder 7, there are a plurality of ring-shaped concave parts 7a formed in parallel along the inner circumference. By this construction, radiation heat from the single crystal C is not reflected by the cooling cylinder 7 to the single crystal and effectively absorbed by the plurality of the ring-shaped concave parts 7a, thus the single crystal C can be efficiently cooled.

Description

  The present invention relates to a single crystal pulling apparatus that pulls up a single crystal while growing it by the Czochralski method (hereinafter referred to as “CZ method”).

  The CZ method is widely used for the growth of silicon single crystals. In this method, as shown in FIG. 23, a silicon melt M is formed in the crucible 50 by the heat of the heater 52 in the furnace, the seed crystal P is brought into contact with the surface thereof, the crucible 50 is rotated, By pulling the seed crystal P upward while rotating it in the opposite direction, a single crystal C is formed at the lower end of the seed crystal P.

By the way, when pulling up the single crystal C, solidification of the crystal is delayed unless the radiant heat from the surroundings to the growing single crystal C is cut off and the single crystal C is not cooled below a predetermined temperature. There is a problem that the production efficiency deteriorates due to a decrease in the production rate.
In addition, when the pulling rate decreases, the cooling rate in the intermediate temperature zone (1200 to 1000 ° C.) where the COP defect occurs and the low temperature zone (1050 to 850 ° C.) where the OSF defect occurs (the residence time in that temperature zone). There is a problem that grow-in defects such as the COP defect and the OSF defect are likely to occur.
Therefore, conventionally, a radiation shield 51 is provided to block radiation heat to the outer peripheral surface of the single crystal C to be grown. This radiation shield 51 is provided above the crucible so as to surround the pull-up region of the single crystal C, whereby a certain degree of cooling effect on the grown single crystal C can be obtained.

However, the radiation shield 51 alone is not sufficient in the ability to cut off the radiant heat to the single crystal C. In order to further enhance the ability to cut off the radiant heat, a cylindrical cooling cylinder 53 is arranged inside the shield as shown in the figure. The structure which did is proposed (refer patent document 1).
The cooling cylinder 53 is provided with a water pipe (not shown) spirally so as to surround the single crystal C, for example, and the surface thereof is maintained at a predetermined temperature by continuously supplying cooling water. ing.
By providing such a cooling cylinder 53, it is possible to absorb the radiant heat to the single crystal C more effectively than the configuration of the radiation shield 51 alone.

JP-A-11-92272

However, in the configuration of the cooling cylinder 53 as shown in the figure, the radiant heat emitted from the single crystal C is reflected by the inner peripheral surface of the cooling cylinder 53 and returns to the single crystal C again, so that the cooling effect is insufficient. There was a problem.
On the other hand, when the cooling cylinder 53 is brought close to the melt surface for improving the cooling capacity, the melt M near the crystal periphery may be excessively cooled, causing the problem of causing dislocation of the single crystal C. there were.

  The present invention has been made under the circumstances described above. In a single crystal pulling apparatus that pulls a silicon single crystal from a crucible by the Czochralski method, the single crystal to be grown is effectively cooled, An object of the present invention is to provide a single crystal pulling apparatus capable of suppressing generation of defects and suppressing dislocation formation of crystals.

A single crystal pulling apparatus according to the present invention, which has been made to solve the above problems, forms a silicon melt in a crucible by heating a heater, and pulls the silicon single crystal from the crucible by the Czochralski method. A pulling device, provided above the crucible, having an upper portion and a lower portion with an opening, surrounding a single crystal to be pulled up, and having a cooling cylinder for cooling the single crystal, the cooling cylinder On the inner peripheral surface side, a plurality of annular recesses are formed in parallel along the circumferential direction.
In addition, as for the said annular recessed part, it is desirable for the cross-sectional bottom part to be formed in the parabolic shape or the circular arc shape.
Moreover, it is desirable that the annular recesses adjacent to each other in the vertical direction are adjacent to each other without a gap, and the adjacent portions have a pointed shape.
Further, in the annular recess in which the bottom of the cross section is formed in a parabolic shape or an arc shape, the width dimension of the opening in the single crystal pulling axial direction is h, and the midpoint of the opening in the width direction and the annular recess The width dimension h is 1 to 100 mm, and the line segment length t is t, where t is the length of the line connecting the bottom vertices and α is the intersection angle between the extended line and the single crystal pulling axis. Is preferably 10 mm or more, and the crossing angle α is preferably defined within a range of 10 ° to 170 °.
Further, it is desirable that the cooling cylinder is formed so as to reduce the diameter downward.

With this configuration, in the step of pulling up the single crystal from the crucible along the pulling-up axis, radiant heat from the single crystal is not reflected toward the single crystal by the cooling cylinder, and a plurality of annular recesses Is effectively absorbed.
Thereby, the single crystal can be efficiently cooled, and the single crystal can be grown while maintaining a predetermined pulling speed. As a result, the transit time (stay time) in the medium and low temperature zone where glow-in defects such as COP and OSF are generated can be greatly reduced, and the generation thereof can be suppressed.
In addition, since the single crystal can be pulled up at a higher speed while the distance between the cooling cylinder and the melt surface is kept constant, the occurrence of dislocation of the crystal is suppressed by suppressing the supercooling of the melt. Can be suppressed and productivity can be improved.

  According to the present invention, in a single crystal pulling apparatus that pulls a silicon single crystal from a crucible by the Czochralski method, the single crystal to be grown is effectively cooled, the occurrence of glow-in defects is suppressed, and the dislocations of the crystal A single crystal pulling apparatus capable of suppressing the conversion can be obtained.

FIG. 1 is a cross-sectional view showing a main part configuration of a single crystal pulling apparatus according to the present invention. FIG. 2 is a partially enlarged cross-sectional view of a cooling cylinder provided in the single crystal pulling apparatus of FIG. FIG. 3 is a diagram showing a cross-sectional shape of an annular recess included in the cooling cylinder of FIG. 4 is a cross-sectional view showing a modification of the cross-sectional shape of the annular recess of the cooling cylinder of FIG. FIG. 5 is a graph of the crystal temperature distribution showing the results of Experiment 1 in the example according to the present invention. FIG. 6 is a graph of the crystal temperature distribution showing the results of Experiment 1 in the example according to the present invention. FIG. 7 is a graph showing the results of Experiment 1 in the example according to the present invention, and showing the temperature gradient in the crystal axis direction. FIG. 8 is a graph showing the result of Experiment 1 in the embodiment according to the present invention, and is a graph showing the COP generation region passage time. FIG. 9 is a graph showing the results of Experiment 1 in the embodiment according to the present invention, and is a graph showing the OSF generation region passage time. FIG. 10 is a cross-sectional view showing the shape of the cooling cylinder used in Experiment 2 in the embodiment according to the present invention. FIG. 11 is a graph showing the results of Experiment 2 in the example according to the present invention and showing the temperature gradient in the crystal axis direction. FIG. 12 is a graph showing the result of Experiment 2 in the embodiment according to the present invention, and is a graph showing the COP generation region passage time. FIG. 13 is a graph showing the results of Experiment 2 in the embodiment according to the present invention, and is a graph showing the OSF generation region passage time. FIG. 14 is a graph showing the results of Experiment 3 in the example according to the present invention and showing the temperature gradient in the crystal axis direction. FIG. 15 is a graph showing the results of Experiment 3 in the example according to the present invention, and is a graph showing the COP generation region passage time. FIG. 16 is a graph showing the results of Experiment 3 in the example according to the present invention, and is a graph showing the OSF generation region passage time. FIG. 17 is a graph showing the results of Experiment 4 in the example according to the present invention, and showing the temperature gradient in the crystal axis direction. FIG. 18 is a graph showing the results of Experiment 4 in the embodiment according to the present invention, and is a graph showing the COP generation region passage time. FIG. 19 is a graph showing the results of Experiment 4 in the embodiment according to the present invention and is a graph showing the OSF generation region passage time. FIG. 20 is a graph showing the results of Experiment 5 in the example according to the present invention and showing the temperature gradient in the crystal axis direction. FIG. 21 is a graph showing the results of Experiment 5 in the example according to the present invention, and is a graph showing the COP generation region passage time. FIG. 22 is a graph showing the results of Experiment 5 in the example according to the present invention, and is a graph showing the OSF generation region passage time. It is sectional drawing for demonstrating the conventional single crystal pulling apparatus.

Embodiments of a single crystal pulling apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a main part configuration of a single crystal pulling apparatus according to the present invention.
This single crystal pulling apparatus 1 is loaded on a furnace body 2 formed by superposing a pull chamber 2b on a cylindrical main chamber 2a, a crucible 3 provided in the furnace body 2, and an inner surface of the crucible 3. A resistance heater 4 (hereinafter simply referred to as a heater) that melts a semiconductor raw material (raw material polysilicon) to form a silicon melt M, and a pulling mechanism for pulling up a single crystal C to be grown by a pulling wire 5 (see FIG. Not shown).

The heater 4 is provided with a cylindrical slit portion 4 a as a heat generating portion so as to surround the crucible 3.
The crucible 3 has a double structure, and the inner side is constituted by a quartz glass crucible 3a and the outer side is constituted by a graphite crucible 3b. The crucible 3 is controlled to rotate around a pulling shaft by a rotary motor (not shown), and can be raised in the main chamber 2a by a lifting device (not shown) as the single crystal C is pulled (grown). Has been made.
A seed crystal P is attached to the tip of the pulling wire 5 pulled up by the pulling mechanism.

In the main chamber 2a, a radiation shield 6 surrounding the periphery of the single crystal C is disposed above and in the vicinity of the crucible 3. The radiation shield 6 has an opening at the top and bottom, has a cylindrical shape, shields excess radiation heat from the heater 4 and the like to the growing single crystal C, and rectifies the gas flow in the furnace. Is.
Although the radiation shield 6 is fixed in position in the furnace body 2, the distance dimension (gap) between the lower end of the radiation shield 6 and the molten liquid surface increases the crucible 3 with the growth of the single crystal C. Thus, the predetermined distance is controlled.

  In the present embodiment, a cylindrical cooling cylinder 7 is provided inside the radiation shield 6. The cooling cylinder 7 has an upper portion and a lower portion that open so as to surround the single crystal C, and the diameter of the cooling tube 7 is reduced downward. Thus, the diameter of the cooling cylinder 7 is reduced downward, so that the distance from the single crystal C becomes shorter at the lower part, and the lower part of the single crystal C that has just solidified is effectively cooled. be able to.

  A plurality of annular recesses 7 a (grooves) are formed in parallel along the circumferential direction on the inner peripheral surface side of the cooling cylinder 7. As shown in FIG. 1, the cross-section of each annular recess 7a has a bottom formed in a parabolic shape. Further, the annular recesses 7a adjacent to each other in the vertical direction are adjacent to each other without a gap, and the adjacent portions are pointed. For this reason, as shown in the drawing, the cross section on the inner peripheral surface side of the cooling cylinder 7 has a sawtooth shape.

  Further, for example, a water pipe (not shown) is provided in the internal space 7b of the cooling cylinder 7 shown in FIG. 2, and the surface temperature of the cooling cylinder 7 is set to a predetermined value by circulating cooling water at a predetermined temperature through the water pipe. The temperature is maintained at 30 ° C. In the cooling cylinder 7, the surface of the cooling cylinder 7 may be maintained at a predetermined temperature by directly circulating the cooling water in the internal space 7b without providing a water pipe.

The shape of each annular recess 7a formed in the cooling cylinder 7 is defined as shown in FIGS.
That is, as shown in FIG. 3, in the annular recess 7a, the width dimension h of the opening in the single crystal pulling axial direction is defined within the range of 1 to 100 mm, more preferably 5 to 50 mm.
Further, the length dimension t of the line segment connecting the midpoint Pt1 in the width direction of the opening and the bottom vertex Pt2 of the annular recess 7a is defined within a range of 10 mm or more. The length dimension t is preferably in the range of 10 mm to 50 mm.
As shown in FIGS. 2 and 3, the crossing angle α between the extension line L1 of the line segment and the single crystal pulling up axis L2 is in the range of 10 ° to 170 °, more preferably 30 ° to 120 °. It is prescribed.
By defining the shape of the annular recess 7a in this way, even if the radiant heat emitted from the single crystal C is reflected on the inner peripheral surface side of the cooling cylinder 7, it is difficult to return to the single crystal C again. it can.

According to the single crystal pulling apparatus 1 including the cooling cylinder 7 configured as described above, in the step of pulling up the single crystal C from the crucible 3 by the wire 5, the radiant heat from the single crystal C is converted into the single crystal C by the cooling cylinder 7. It is not reflected toward and is effectively absorbed by the plurality of annular recesses 7a.
Thereby, the single crystal C can be efficiently cooled, and the single crystal C can be grown while maintaining a predetermined pulling speed. As a result, the transit time (stay time) in the medium and low temperature zone where glow-in defects such as COP and OSF are generated can be greatly reduced, and the generation thereof can be suppressed.
In addition, since the single crystal C can be pulled up at a higher speed while the distance between the cooling cylinder 7 and the melt surface M1 is kept constant, the supercooling of the melt M can be suppressed and the presence of crystals can be suppressed. The occurrence of dislocation can be suppressed and productivity can be improved.

In addition, in the said embodiment, although the bottom cross section of the cyclic | annular recessed part 7a was shown in the example formed in the parabola shape, it is not limited to it.
For example, the bottom section of the annular recess 7a may be arcuate, or may be triangular as shown in FIG. 4 (a), or rectangular as shown in 4 (b).
Further, the bottom section may be configured by combining a parabolic or arc-shaped annular recess and a triangular or rectangular annular recess.
Moreover, in the said embodiment, although the cooling cylinder 7 was made into the shape which diameter-reduces toward the downward direction, it may be formed in the shape of a straight cylinder with a constant diameter.

The single crystal pulling apparatus according to the present invention will be further described based on examples.
[Experiment 1]
In Experiment 1, the effect of the single crystal pulling apparatus according to the present invention was verified.
Specifically, single crystal pulling was performed under the conditions shown in Table 1 based on the embodiment shown in FIGS.
In Table 1, the intersection angle α, the width dimension h, and the depth dimension t are parameters shown in FIG. Moreover, 100 silicon single crystals having a diameter of 310 mm were grown under all conditions. The inner diameter of the crucible is 788 mm, and the height of the heater heating portion arranged on the side of the crucible is 450 mm.

The graph of FIG. 5 shows the crystal temperature distribution in Example 1 and Comparative Example 1 symmetrically compared (left side is Comparative Example 1 and right side is Example 1), and FIG. 6 shows Example 2 and Comparative Example 1. The crystal temperature distribution is shown symmetrically in comparison with the left and right sides (Comparative Example 1 on the left side and Example 2 on the right side).
As shown in the crystal temperature distribution of FIGS. 5 and 6, the cooling effect of the single crystal was clearly greater in both Example 1 and Example 2 than in Comparative Example 1, and the effect of the present invention was confirmed.

FIG. 7 is a graph showing the temperature gradient in the crystal axis direction under each condition, FIG. 8 is a graph showing the COP generation region passage time under each condition, and FIG. 9 is the OSF generation region passage time under each condition. Incidentally, as Comparative Example 1, a condition was added in which an uneven portion is not formed in the cross-sectional shape on the inner surface side of the cooling cylinder as shown in FIG. In the graph of FIG. 7, the vertical axis represents the temperature gradient (K / mm), and the horizontal axis represents the position in the crystal axis direction (mm). 8 and 9, the vertical axis represents time (min) and the horizontal axis represents the position (mm) in the crystal axis direction.
Moreover, based on the results of FIGS. 7 to 9, the effect (improvement rate) of Example 1 with respect to Comparative Example 1 (conventional configuration) is shown in Table 2, and the effect of Example 2 with respect to Comparative Example 1 (conventional configuration) ( Table 3 shows the improvement rate.

As a result of Experiment 1, in Examples 1 and 2, the temperature gradient along the crystal axis direction was larger than that in Comparative Example 1, and as a result, the pulling speed in Example 1 was about 3% as compared with Comparative Example 1. In Example 2, the pulling speed increased about 5% compared to Comparative Example 1.
In Examples 1 and 2, the increase in pulling speed shortens the residence time (passing time) in the COP generation temperature region and the OSF generation temperature region, and greatly reduces both the COP defect density and the OSF defect density. I was able to.

[Experiment 2]
In Experiment 2, the uneven shape to be formed on the inner peripheral surface side of the cooling cylinder was verified. Specifically, conditions (Comparative Example 2) in which a plurality of annular protrusions 7c (circular arc shape) are formed on the inner peripheral surface side of the cooling cylinder 7 shown in FIG. 1 as shown in FIG. A condition (Example 3) in which a plurality of annular recesses 7a (circular arc shape) are formed as shown in FIG. 10B, and an annular recess 7a (circular arc shape) and an annular convex portion as shown in FIG. 10C. Each of the conditions (Comparative Example 3) in which 7c (circular arc shape) was alternately formed was verified.
FIG. 11 is a graph showing the temperature gradient in the crystal axis direction under each condition, FIG. 12 is a graph showing the COP generation region passage time under each condition, and FIG. 13 is a graph showing the OSF generation region passage time under each condition. In addition, as shown in FIG. 23, the conditions (comparative example 1) which the uneven | corrugated | grooved part is not formed in the cross-sectional shape of the inner surface side of a cooling cylinder were added.

As shown in FIG. 11, the temperature gradient was the largest in Example 3 in which a plurality of annular recesses 7a were formed on the inner peripheral surface side of the cooling cylinder. Therefore, the pulling-up speed increased most compared with the conventional cooling cylinder configuration (Comparative Example 1).
In addition, as shown in FIGS. 12 and 13, the stay time (passing time) in the COP generation temperature region and the OSF generation temperature region is shortened in Example 3, and both the COP defect density and the OSF defect density are reduced. I was able to.
From the results of Experiment 2, it was confirmed that it is preferable to form a plurality of annular recesses on the inner peripheral surface side of the cooling cylinder as in Example 3. However, the conditions under which the annular convex portions were alternately formed had a low effect.

[Experiment 3]
In Experiment 3, the preferred cross-sectional shape when an annular recess was formed on the inner peripheral surface side of the cooling cylinder was verified.
Specifically, a condition (Example 4) in which the cross-sectional shape of the recess 7a on the inner peripheral surface side of the cooling cylinder 7 shown in FIG. 1 is formed in a triangular shape as shown in FIG. The conditions (Example 5) formed in a rectangular shape as shown in FIG. 4B and the conditions (Example 6) formed in a parabolic shape as shown in FIG. 1 were verified.
FIG. 14 is a graph showing the temperature gradient in the crystal axis direction under each condition, FIG. 15 is a graph showing the COP generation region passage time under each condition, and FIG. 16 is a graph showing the OSF generation region passage time under each condition. In addition, as shown in FIG. 23, the conditions (comparative example 1) which the uneven | corrugated | grooved part is not formed in the cross-sectional shape of the inner surface side of a cooling cylinder were added.

As shown in FIG. 14, the temperature gradient was the largest in Example 6 in which the concave section on the inner peripheral surface side of the cooling cylinder had a parabolic shape. Therefore, the pulling-up speed increased most compared with the conventional cooling cylinder configuration (Comparative Example 1).
Further, as shown in FIGS. 15 and 16, in Example 6, the stay time (passing time) in the COP generation temperature region and the OSF generation temperature region is the shortest, and both the COP defect density and the OSF defect density are reduced. I was able to.
From the result of Experiment 3, it was confirmed that the recess cross-sectional shape on the inner peripheral surface side of the cooling cylinder is most preferably a parabolic shape.

[Experiment 4]
In Experiment 4, when an annular recess having a parabolic cross section was provided on the inner peripheral surface side of the cooling cylinder, the depth t of the recess 7a defined in FIG.

The temperature gradient in the crystal axis direction under each condition (Examples 7 to 11) is shown in FIG. 17, the passage time in the COP generation temperature region is shown in FIG. 18, and the passage time in the OSF generation temperature region is shown in FIG.
As shown in FIG. 17, the temperature gradient increases as the depth dimension t increases, and the temperature gradient increases remarkably when the depth dimension t is 10 mm or more. Further, as shown in FIGS. 18 and 19, the residence time (passing time) in the COP generation temperature region and the OSF generation temperature region is shorter as the depth dimension t is larger.
From these results, it is considered that the depth dimension t is preferably 10 mm or more.
[Experiment 5]
In Experiment 5, the crossing angle α defined in FIG. 3 was verified based on the conditions in Table 5.

The temperature gradient in the crystal axis direction under each condition (Examples 12 to 16) is shown in FIG. 20, the passage time in the COP generation temperature region is shown in FIG. 21, and the passage time in the OSF generation temperature region is shown in FIG.
As shown in FIG. 20, the temperature gradient became the largest when the crossing angle α was around 50 °. Further, as shown in FIGS. 21 and 22, it was confirmed that the stay time (passing time) in the COP generation temperature region and the OSF generation temperature region was the shortest when the crossing angle α was around 50 °, which was more preferable.

  From the results of the above examples, according to the single crystal pulling apparatus according to the present invention, it is possible to effectively cool the single crystal to be grown, suppress the occurrence of glow-in defects, and dislocations of the crystal It was confirmed that crystallization could be suppressed.

DESCRIPTION OF SYMBOLS 1 Single crystal pulling apparatus 2 Furnace body 3 Crucible 4 Heater 4a Slit part 5 Wire 6 Radiation shield 7 Cooling cylinder 7a Annular recessed part C Single crystal M Silicon melt P Seed crystal

Claims (5)

A single crystal pulling apparatus for forming a silicon melt in the crucible by heating a heater and pulling up the silicon single crystal from the crucible by the Czochralski method,
Provided above the crucible, the upper and lower portions are formed as openings to surround the single crystal to be pulled up, and includes a cooling cylinder for cooling the single crystal,
A single crystal pulling apparatus characterized in that a plurality of annular recesses are formed in parallel along the circumferential direction on the inner peripheral surface side of the cooling cylinder.   The single crystal pulling apparatus according to claim 1, wherein the annular recess has a bottom section in a parabolic shape or an arc shape.   The single crystal pulling apparatus according to claim 2, wherein the annular recesses adjacent to each other in the vertical direction are adjacent to each other without a gap, and the adjacent portions have a pointed shape. In the annular recess in which the bottom of the cross section is formed in a parabolic shape or an arc shape, the width dimension in the single crystal pulling axial direction of the opening is h, and the center point in the width direction of the opening and the apex of the bottom of the annular recess Where t is the length of the line connecting the two and the α is the intersection angle between the extension of the line and the single crystal pulling axis.
The width dimension h is 5 to 50 mm, the line segment length t is 10 mm or more, and the crossing angle α is defined within a range of 30 ° to 120 °, respectively. The single crystal pulling apparatus described in 1.   The single crystal pulling apparatus according to any one of claims 1 to 4, wherein the cooling cylinder is formed so as to reduce in diameter downward.

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