JP2022010815A - Radiation shield - Google Patents

Abstract

To provide a radiation shield by constituting detachably an inner diameter adjustment ring to a radiation shield body provided in a silicon single crystal pulling-up device.SOLUTION: In a radiation shield provided in a silicon single crystal pulling-up device, and comprising a radiation shield body and an inner diameter adjustment ring, the inner diameter adjustment ring comprises an inverted cone-shaped upper side tip, and a cylindrical lower side trunk to be fitted to the radiation shield, and the inner diameter adjustment ring is detachably attached to the radiation shield body.SELECTED DRAWING: Figure 1

Description

The present invention relates to a radiation shield, and more particularly to a radiation shield used in a silicon single crystal pulling device by the Czochralski method.

The Czochralski method (CZ method) is known as a method for producing a silicon single crystal. In the CZ method, granular polycrystalline silicon as a raw material is put into a crucible, and the polycrystalline silicon is heated and melted by a heater surrounding the crucible. When the silicon melt is formed in the crucible, the seed crystal held on the crucible is lowered while rotating the crucible in a certain direction, and is brought into contact with the surface of the silicon melt in the crucible. When the seed crystal is raised while rotating in a predetermined direction, a columnar silicon single crystal grows below the seed crystal. In the growth of silicon single crystal ingots, the seed crystal is first pulled up and elongated crystals are grown to form the neck part, and the crystals grow from the neck part in the radial direction to form the shoulder part, and the straight body part that becomes the product part. Is formed. After the straight body is formed, the diameter is gradually reduced to form the bottom of the ingot.

In such a method for growing a silicon single crystal, when the tip of the seed crystal is brought into contact with the silicon melt, the contact portion rapidly rises at the surface temperature of the silicon melt, resulting in a thermal shock or a sudden temperature at the seed crystal. A gradient is generated and slip dislocations occur. The dislocations generated at the contact site between the seed crystal and the silicon melt are propagated to the lower part of the ingot during crystal growth, and dislocations occur in the silicon single crystal.

For this reason, in the silicon single crystal pulling device, a radiation shield is provided on the upper side of the rutsubo so as to surround the silicon single crystal pulling region to block the radiant heat from the surface of the silicon melt, and the ingot being pulled. The temperature is made uniform over the entire length to suppress dislocations, and the silicon single crystal is not deformed, normal solidification is promoted, the pulling speed is increased, and productivity is improved.

By the way, the dimensions of the silicon wafer are standardized, and the diameter φ of the silicon single crystal to be pulled up is, for example, about 305 mm (φ300 ± 0.2; see JEIDA EM-3602). In order to pull up a silicon single crystal with a diameter of 305 mm, it is necessary to use a radiation shield with an inner diameter that matches its thickness. Therefore, a radiation shield for a silicon single crystal with a diameter of 305 mm cannot be used to pull up a silicon single crystal with a different diameter. Therefore, in order to manufacture silicon single crystals having different diameters, it is necessary to prepare a radiation shield dedicated to the silicon single crystals, which poses a problem in terms of cost.

As a method for solving such a problem, in the radiation shield arranged above the rutsubo, the radiation shield is curved inward from the cylindrical straight body portion and the lower end of the straight body portion to form the lower end opening. A radiation shield having a shoulder and a heat-shielding inner member having a heat-shielding inner member that protrudes in the radial direction with a predetermined width and has a predetermined thickness in the height direction at a predetermined position in the circumferential direction at the peripheral edge of the lower end opening. Is disclosed (Patent Document 1). In Patent Document 1, by making the heat shield inner member movable along the circumferential direction at the peripheral edge of the lower end opening of the radiation shield, the heat shield is appropriately obtained as the silicon melt decreases during the growth of the single crystal. By adjusting the position of the inner member, it is possible to suppress the silicon melt from being excessively cooled while keeping the single crystal warm more effectively, and to prevent dislocation due to deformation of the crystal.

In Patent Document 2, a radiation shield, an annular separation inner member provided so as to be engaged with the lower end opening of the radiation shield, and the separation inner member are moved up and down toward the lower end opening of the radiation shield. A device for pulling up a silicon single crystal in which the lower end opening of the radiation shield is reduced by engaging the separation inner member lowered by the raising / lowering means to the lower end opening of the radiation shield is disclosed. Has been done.

In both Patent Documents 1 and 2, in addition to the radiation shield, a heat shield inner member or a separate inner member is provided to adjust the distance between the radiation shield and the outer peripheral surface of the silicon single crystal, thereby causing crystal defects in the ingot. It is disclosed that it is possible to suppress the problem and that it leads to an improvement in the pulling speed.

On the other hand, as a technique for growing a large-diameter silicon single crystal without forming a neck portion, in Patent Document 3, as a heat insulating means arranged on the upper side of the crucible, a hole through which the grown ingot can pass and a hole size thereof. A silicon single crystal pulling device including an upper heat shield including a hole size adjusting unit capable of adjusting the hole size and a driving unit for driving the hole size adjusting unit is disclosed. In Patent Document 3, a hole size adjusting portion is mounted inside the upper heat shield to minimize the thermal shock generated when the seed crystal is immersed in the silicon melt, thereby increasing the diameter of the neck portion. ..

In all of Patent Documents 1 to 3, the distance between the silicon single crystal or seed crystal being pulled up and the heat shield is adjusted to adjust the radiant heat of the silicon melt transmitted to the outer peripheral surface of the ingot to adjust the radiant heat of the silicon ingot. It improves quality and productivity. However, the means for adjusting the distance between the silicon single crystal and the heat shield is a hole for lowering and engaging with the elevating means provided in the apparatus or for adjusting the size of the hole inside the heat shield. The device is complicated because a size adjusting unit is provided and a driving unit that controls the hole size adjusting unit is arranged.

Japanese Unexamined Patent Publication No. 2013-75785 Japanese Unexamined Patent Publication No. 2013-199387 Special Table 2016-529198

Therefore, an object of the present invention is to provide a radiation shield by detachably configuring an inner diameter adjusting ring with respect to the radiation shield main body provided in the silicon single crystal pulling device.

The radiation shield of the present invention comprises a radiation shield main body and an inner diameter adjusting ring detachably fitted to the radiation shield main body, and the inner diameter adjusting ring has an inverted truncated cone-shaped upper tip portion and a cylindrical lower portion. It is characterized in that the side body is integrally formed.
By providing the above configuration, the distance between the silicon single crystal and the radiation shield can be easily adjusted, and the silicon single crystal having a desired diameter is formed by crystal deformation caused by radiant heat from a graphite heater or a silicon melt. It is possible to suppress the formation of dislocations, improve the yield and improve the pulling speed.

It is preferable that the inner diameter adjusting ring includes a plurality of inner diameter adjusting rings having different inner diameters, and the inner diameter adjusting ring corresponding to the diameter of the silicon single crystal to be pulled up is fitted to the radiation shield main body.
With the above configuration, the distance between the silicon single crystal and the radiation shield can be easily adjusted, so that the silicon single crystal having various diameters can be pulled up.

The inner diameter adjusting ring is preferably made of a carbon material or a carbon fiber material.
With the above configuration, the temperature of the silicon single crystal being pulled up can be made uniform over the entire length, crystal deformation can be suppressed, and dislocation can be suppressed.

The inner diameter adjusting ring comprises an inverted truncated cone-shaped upper tip portion and a tapered lower body portion for fitting to the radiation shield, and the lower body portion and the inner peripheral surface of the radiation shield main body. Is preferably fitted on a tapered surface.
Since the lower body portion of the inner diameter adjusting ring has a tapered shape, it is preferable because the fitting with the radiation shield is easy and the fitting is hard to come off.

According to the present invention, the inner diameter of the inner diameter adjusting ring and the outer surface of the silicon single crystal ingot are formed by fitting one or more inner diameter adjusting rings to the radiation shield main body according to the diameter of the silicon single crystal to be pulled up. The distance t to and from can be easily adjusted, dislocations due to crystal deformation of the silicon single crystal ingot can be suppressed, and the yield and the pulling speed can be improved.

FIG. 1 is a schematic vertical sectional view showing a state in which an inner diameter adjusting ring is fitted to a radiation shield main body and a silicon single crystal ingot is pulled up in the silicon single crystal pulling device according to the present invention. FIG. 2 is a diagram showing an inverted truncated cone-shaped upper tip portion and a cylindrical lower trunk portion in the inner diameter adjusting ring. FIG. 3 is a diagram showing an inner diameter adjusting ring having a tapered lower body portion for fitting to the radiation shield main body as another embodiment of the present invention. FIG. 4 is a diagram in which two inner diameter adjusting rings having different inner diameters are fitted to the radiation shield main body.

Hereinafter, the radiation shield of the present invention will be described with reference to the drawings.
FIG. 1 shows a state in which a silicon single crystal is pulled up in a part of the silicon single crystal pulling device 100 according to the present invention.
In the silicon single crystal pulling device 100, a quartz crucible 3 in which a silicon melt 2 is housed and a graphite crucible 4 for supporting the quartz crucible 3 on the outside are arranged inside a main chamber (not shown), and graphite is used. At the lower part of the crucible 4, a support structure 9 and a support base 10 for supporting the load of the silicon melt 2 and the crucible (quartz crucible 3 and the graphite crucible 4) are arranged.

Further, on the upper side of the quartz crucible 3, a radiation shield main body 7 that blocks heat released from the silicon melt 2 when the silicon single crystal 1 is pulled up from the silicon melt 2 is provided.

The feature of the present invention is that a removable inner diameter adjusting ring 8 is provided on the peripheral edge of the lower end opening of the radiation shield main body 7 so that the outer surface of the silicon single crystal 1 and the inner diameter of the radiation shield 70 are kept at a predetermined distance. To prepare for. As shown in FIG. 2, the inner diameter adjusting ring 8 is integrally formed with an inverted truncated cone-shaped upper tip portion 8a and a cylindrical lower body portion 8b having a substantially constant diameter.

The inner diameter adjusting ring 8 has a size or shape that can be attached and detached without a gap in the opening at the lower end of the radiation shield main body 7. The outer diameter of the lower body portion 8b of the inner diameter adjusting ring 8 may be a size that can be fitted to the lower end opening of the radiation shield main body 7, and is usually 400 to 600 mm. The upper tip portion 8a of the inner diameter adjusting ring 8 has an inverted truncated cone shape inclined outward by 20 to 80 °, specifically 55 to 65 ° with respect to the lower body portion 8b. The height of the inverted cone portion is 20 to 100 mm, preferably 50 to 70 mm. By having this inclination and height, it can be easily fitted to the radiation shield main body 7 without using a fixing jig such as a screw. On the other hand, the height of the lower body portion 8b may be about the thickness of the radiation shield main body 7, and is usually 20 to 60 mm, preferably 35 to 45 mm.

The lower body portion of the inner diameter adjusting ring 8 may have a tapered shape as shown in FIG. Since the lower body portion 8b of the inner diameter adjusting ring 8 has a tapered shape, it fits better in the radiation shield main body 7 than in the case of a cylindrical shape, and it is unlikely that the fitting will be disengaged such as falling.

In one specific embodiment, the main portion of the radiation shield main body 7 has an inner diameter suitable for the maximum diameter of the silicon single crystal 1, and the inner diameter adjusting ring 8 has an inner diameter suitable for the minimum diameter thereof. The shape of the main portion of the radiation shield main body 7 is not limited as long as it can correspond to various diameters of the silicon single crystal 1 as long as the silicon single crystal 1 does not come into contact with the cylindrical portion.

The distance t between the outer peripheral surface of the silicon single crystal 1 and the inner diameter of the inner diameter adjusting ring 8 may be adjusted by the thickness of the lower body portion 8b of the inner diameter adjusting ring 8. The thickness of the lower body portion 8b is usually 10 to 30 mm, and is adjusted according to the diameter of the silicon single crystal 1.

Alternatively, the lower body portion 8b of the inner diameter adjusting ring 8 may be mounted by being fastened to a support inner member (not shown) provided on the inner peripheral surface side edge portion of the lower end opening of the radiation shield main body 7. good. Specifically, a groove is provided on the upper surface side of the support inner member, and a hook fixed with a screw is hooked on the upper portion of the lower body portion of the inner diameter adjusting ring 8 to stop the groove.

The inner diameter adjusting ring 8 fitted to the radiation shield main body 7 may be one, or two or more inner diameter adjusting rings 8 may be stacked depending on the diameter of the silicon single crystal 1 to be pulled up. FIG. 4 is a vertical cross-sectional view in which two inner diameter adjusting rings 8 are fitted to the radiation shield main body 7. By providing one or two or more inner diameter adjusting rings 8 according to the diameter of the silicon single crystal 1 on the radiation shield main body 7, the distance between the inner diameter of the inner diameter adjusting ring 8 and the outer peripheral surface of the silicon single crystal 1 Can be adjusted.

The inner diameter adjusting ring 8 is provided so that the distance t between the inner peripheral surface of the inner diameter adjusting ring 8 and the outer peripheral surface of the silicon single crystal 1 is at least about 20 mm, preferably 10 to 30 mm. Thereby, even if the diameters of the silicon single crystals 1 to be pulled up are different, each silicon single crystal 1 can have the same growing environment, and the silicon single crystals 1 having various diameters can be produced.

The inner diameter adjusting ring 8 may be made of the same material as the radiation shield main body 7, such as a carbon material or a carbon fiber material, or a material that does not deform the crystal of the silicon single crystal being grown.

According to the present invention, the silicon single crystal 1 having various diameters can be pulled up by appropriately fitting the inner diameter adjusting ring 8 to the radiation shield main body 7. Further, the pulled-up silicon single crystal is not dislocated due to crystal deformation, and the yield when 40 silicon single crystals are pulled up is 80% or more.

Hereinafter, the present invention will be specifically described based on experimental examples, but the present invention is not limited thereto.
[Example 1]
The raw material silicon was put into a quartz crucible, and a silicon single crystal having a diameter of 460 mm was pulled up. At this time, the diameter of the radiation shield main body having the diameter of the lower end opening of 560 mm, the upper tip portion inclined outward by 60 ° with respect to the lower body portion, and the diameter of the lower end opening (inner diameter of the inner diameter adjusting ring) is 520 mm. A certain inner diameter adjusting ring was used, and the distance t between the inner peripheral surface of the inner diameter adjusting ring and the outer peripheral surface of the silicon single crystal to be pulled up was set to 30 mm.
The inner diameter adjusting ring was manufactured by machining from a carbon material base material by machining.
Under this condition, the pulled-up silicon single crystal did not undergo dislocation due to crystal deformation, and the yield when 40 silicon single crystals were pulled up by the same method was 85.2%. In addition, no crystal deformation occurred. Further, when the average pulling speed of Comparative Example 1 was 1, the average pulling speed ratio was 1.2.

[Example 2]
The raw material silicon was put into a quartz crucible, and a silicon single crystal having a diameter of 420 mm was pulled up. At this time, the radiation shield main body having a diameter of the lower end opening of 560 mm, the upper tip portion inclined outward by 60 ° with respect to the lower body portion, and the diameter of the lower end portion opening (inner diameter of the first inner diameter adjusting ring) is 520 mm. The diameter of the upper tip and lower end openings (second) fitted inside the first inner diameter adjusting ring and the upper tip and lower end, which are fitted inside the first inner diameter adjusting ring and are inclined outward by 40 ° with respect to the lower body. A second inner diameter adjusting ring having an inner diameter adjusting ring (inner diameter of 480 mm) was used, and the distance t between the inner peripheral surface of the second inner diameter adjusting ring and the outer peripheral surface of the silicon single crystal to be pulled up was set to 30 mm. ..
The inner diameter adjusting ring was manufactured by machining from a carbon material base material by machining.
Under these conditions, the pulled-up silicon single crystal did not undergo dozens of dislocations due to crystal deformation, and the yield when 40 silicon single crystals were pulled up by the same method was 83.0%. In addition, no crystal deformation occurred. Further, when the average pulling speed of Comparative Example 1 was 1, the average pulling speed ratio was 1.3.

[Comparative Example 1]
The silicon single crystal was pulled up in the same manner as in Example 1 except that the inner diameter adjusting ring was not used in Example 1.
The pulled-up silicon single crystal undergoes dislocation due to crystal deformation, and the yield when 40 silicon single crystals are pulled up under the same conditions as in Comparative Example 1 is 50.5%, which is higher than that of Example 1. Was inferior. Furthermore, crystal deformation was caused.

In Example 1, the yield at the number of raised lines of 40 was improved by about 69% as compared with Comparative Example 1. Further, in Example 1, since the crystal was not deformed, the average pulling speed could be increased by about 20% as compared with Comparative Example 1.

1 Silicon single crystal 2 Silicon crucible 3 Quartz crucible 4 Graphite crucible 5 Graphite heater 6 Insulation material 7 Radiation shield body 8 Inner diameter adjustment ring 8a Inverted conical trapezoidal upper tip 8b Cylindrical lower body 9 Support structure 10 Support base 70 Radiation shield 100 Silicon single crystal pulling device

Claims (4)

It consists of a radiation shield body and an inner diameter adjusting ring that is detachably fitted to the radiation shield body.
The inner diameter adjusting ring is a radiation shield characterized in that an upper tip portion having an inverted truncated cone shape and a lower body portion having a cylindrical shape are integrally formed. The radiation shield according to claim 1, wherein the inner diameter adjusting ring includes a plurality of inner diameter adjusting rings having different inner diameters. The radiation shield according to claim 1 or 2, wherein the inner diameter adjusting ring is made of a carbon material or a carbon fiber material. The inner diameter adjusting ring comprises an inverted truncated cone-shaped upper tip portion and a tapered lower trunk portion.
The radiation shield according to any one of claims 1 to 3, wherein the lower body portion and the inner peripheral surface of the radiation shield main body are fitted with a tapered surface.

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