JPH09227281A - Device for pulling up single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent the fall of a single crystal with a device for pulling up the single crystal from a melt by a CZ method by providing the subject device with a second means for pulling up the single crystal which pulls up the single crystal by surface-to-surface supporting the single crystal at plural points in the circumference direction of its outer peripheral surface. SOLUTION: This device for pulling up the single crystal has a pulling-up device body 20 which holes the silicon single crystal 10 by the seed crystal 40 and pulls up the silicon single crystal from the silicon melt and the second means for pulling up the single crystal 30 which is disposed within a pull chamber 21 of the pulling up device body 20 and holds and pulls up the straight cylindrical part 12 of the single crystal 10. The single crystal 10 is pulled up from the raw material melt by the CZ method while the single crystal is rotated. The second means 30 for pulling up the single crystal consisting of an annular lifting base 32 suspended and supported by means of plural pieces of wire ropes 31, four piece of holding arms 33 extending downward from the fore positions in the circumferential direction of the lifting base 32, a holding plate 34, a block 35 for operation, etc., is actuated at the point of the time the single crystal 10 is pulled into the chamber 21 according to progression of the growth of the single crystal 10, by which the single crystal 10 is surface-to-surface supported and is pulled up.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a single crystal pulling apparatus used for growing a single crystal by the CZ method.

[0002]

2. Description of the Related Art As a material for a silicon wafer used for manufacturing a semiconductor device, a silicon single crystal grown by the CZ method is often used. In the growth of a silicon single crystal by the CZ method, as is well known, a seed crystal is attached to the lower end of a pulling shaft, the seed crystal is dipped in a silicon melt generated in a quartz crucible, and the seed crystal is rotated from this state. While pulling up, a silicon single crystal is grown below the seed crystal.

Here, the seed crystal is a fine rod made of a silicon single crystal having a diameter of about ten and several millimeters. The upper end is connected to the seed chuck and the lower end is immersed in the silicon melt. When a seed crystal is immersed in a silicon melt, dislocations are introduced by thermal shock.Therefore, after the seed crystal is immersed in the silicon melt, the diameter of the seed crystal is reduced, and this state is maintained for a while to maintain the dislocation-free crystal. A so-called seed reduction is carried out. The diameter of the seed narrowing portion is required to be 5 mm or less from the viewpoint of dislocation-free, and is preferably 3 mm or less.

By the way, the silicon single crystal grown by the CZ method has a diameter of 8 inches and a weight of 100.
The thing of about kg was the mainstream. However, recently, a further increase in diameter has been demanded, and the growth of silicon single crystals with a diameter of 12 inches or more has been planned. As the diameter of the single crystal increases, the weight naturally increases, and the weight reaches 200 kg when the diameter is 12 inches.

The weight of the single crystal being grown is concentrated on the seed crystal, particularly on the seed crystal. When the weight of the crystal increases, the load on the seed crystal increases, but the breaking strength of silicon is 20 kg / m.
The diameter is about m ² , and in order to reliably hold 200 kg of the silicon single crystal, the seed drawing portion needs to have a diameter of more than 5 mm, at least. However, if the diameter exceeds 5 mm, it is impossible to dislocation-free the seed crystal.
Therefore, it is impossible to grow a single crystal of up to 200 kg with the current technology.

In order to solve such a problem, Japanese Patent Publication No. 5-65477 discloses that a single crystal is provided with a constriction at its top, and the constriction is clamped from the surroundings by a plurality of claws. A pulling technique that does not depend on a seed crystal for pulling is shown.

[0007]

The technique for directly clamping the cracked portion formed on a single crystal can reliably pull up a single crystal of more than 200 kg and prevent its fall unless the clamp claws are opened carelessly. it can. However, with the current growth technique, it is difficult to form a dented portion symmetrical with respect to the crystal pulling axis. Therefore, when the single crystal is grown by clamping the constricted portion, the single crystal impairs the concentricity, and there arises a problem that dislocations occur and the diameter control accuracy decreases. In addition, the single crystal has a meandering shape in the pulling axial direction, and an increase in the cutting allowance due to the outer peripheral cutting in the subsequent step becomes a big problem. Furthermore, the scratched portion itself becomes a loss, and the reduction in yield due to this is also a problem that cannot be ignored.

An object of the present invention is to reliably prevent even a single crystal of more than 200 kg from falling, and to prevent the adverse effect on the pulling and the decrease in yield due to the prevention as much as possible. To provide.

[0009]

A single crystal pulling apparatus according to the present invention comprises a pulling apparatus main body for pulling a single crystal from a raw material melt by a CZ method while rotating the single crystal, and a plurality of the outer peripheral surfaces of the single crystal in the circumferential direction. And a second single crystal pulling means for supporting the surface and pulling it at a position.

In the conventional technique for directly clamping a single crystal, the clamp claw makes a point contact with the outer peripheral surface of the constriction portion formed in the single crystal, and the single crystal is pulled up with the constriction portion simply caught by the clamp claw. The single crystal is tilted under the influence of the asymmetrical shape in the cut portion. On the other hand, in the present invention, since the outer peripheral surface of the single crystal is surface-supported at a plurality of positions in the circumferential direction, the single crystal is held upright even if the cut portion formed in the single crystal is asymmetric. Further, since the single crystal is retained even when the formation of the cut portion is omitted, the cut portion can be omitted.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an elevation view showing the configuration of the main part of an example of a single crystal pulling apparatus embodying the present invention, FIG. 2 is a view taken along the line AA of FIG. 1, and FIG. FIG.

This pulling apparatus is provided in a pulling apparatus main body 20 for pulling a silicon single crystal 10 held by a seed crystal 40 from a melt of silicon and a pull chamber 21 of the pulling apparatus main body 20. And a second single crystal pulling means 30 for holding and pulling the straight body part of the.

The pulling device main body 20 is basically the same as the conventional pulling device, and a seed chuck 23 is attached to the lower end of the wire 22 passing through the pull chamber 21 and hanging in the main chamber. Seed crystal 40
The single crystal 10 is grown below the seed crystal 40 and pulled into the pull chamber 21 by pulling while rotating the wire 22 from the state of being immersed in the melt.

Pull chamber 21 of pulling device body 20
The second single crystal pulling means 30 provided therein includes a ring-shaped lifting base 32 suspended and supported by a plurality of wires 31 so that the wire 22 as a pulling shaft is inserted through the central portion, and a lifting base. In order to synchronously close the four holding arms 33 extending downward from the four circumferential positions of 32, the holding plates 34 attached to the lower ends of the holding arms 33, and the four holding arms 33 inwardly. The operation block 35 provided at the lower end of the wire 22.

Each holding arm 33 extends downward from the inclined portion 33a to the outside, a first extending portion 33b extending from the upper end of the inclined portion 33a to the inside, and extends from the lower end of the inclined portion 33a to the inside. The second extending portion 33c is formed. The middle portion of the first extending portion 33b is rotatably connected to the elevating base 32 by a horizontal pin 36 that is perpendicular to the radial direction of the elevating base 32.

As a result, the four holding arms 33 open and close with the horizontal pin 36 as a fulcrum, and are normally kept open to the outside by the plurality of wires 31.

The holding plate 34 is a curved plate bent into an arc corresponding to the outer peripheral surface of the single crystal 10 to be pulled up, and is attached to the tip of the second extending portion 33c of the holding arm 33 with respect to the pulling axis. Are fixed concentrically. As a material of the holding plate 34, it is necessary to use tungsten, molybdenum or the like in order to prevent the single crystal 10 from being contaminated.

The operation block 35 is the seed chuck 2
3 is a conical member located above 3 and attached to the lower end of the wire 22. The maximum diameter of the conical member is set to be larger than the diameter of the circle formed by the tips of the first extending portions 33b provided at the upper ends of the four holding arms 33.

Therefore, as the wire 22 is lifted up, the operation block 35 is moved from below to the inside of the four first extending portions 33b.
Is inserted, the four inclined arms 33 are synchronously closed inward, whereby the uppermost outer peripheral surface of the straight body portion of the single crystal 10 is surface-supported by the four holding plates 34.

Next, a method of growing the single crystal 10 using this pulling apparatus will be described in detail.

Seed chuck 23 of pulling device body 20
The seed crystal 40 attached to the above is soaked in the melt in the crucible installed in the main chamber, and the wire 22 is pulled up while rotating to form the seed diaphragm, the formation of the shoulder portion 11, and the formation of the straight body portion 12. Do in order. At this time, a large diameter portion 13 having a diameter larger than that of the straight body portion 12 is formed at the boundary portion between the shoulder portion 11 and the straight body portion 12. Further, the portion of the second single crystal pulling means 30 excluding the operation block 35 has the pull chamber 21 with the holding arm 33 opened to the outside.
Waiting inside the bottom of

As the growth of the single crystal 10 progresses, the single crystal 10 grows.
When is pulled into the pull chamber 21, the operation block 35 approaches the elevating base 32 from below as the single crystal 10 grows, as shown in FIG. When the operation block 35 is inserted inside the first extending portion 33b of the four holding arms 33, the four holding arms 33 are synchronously closed inward as shown in FIG. Then, at this point, by growing the single crystal 10 so that the portion directly below the large diameter portion 13 of the single crystal 10 is located inside the four holding plates 34, the uppermost outer peripheral surface of the straight body portion 12 becomes 4 It is surface-supported by one holding plate 34.

When the uppermost portion of the straight body portion 12 is surface-supported by the four holding plates 34, the second single crystal pulling means 3
The lifting base 32 of 0 is pulled up by the wire 31 while rotating under the same conditions as before. As a result, single crystal 1
The pulling of 0 means that the straight body portion 12 is pulled up by the second single crystal pulling means 30 thereafter.

At this time, the large diameter portion 13 of the single crystal 10 is hooked on the four holding plates 34. Therefore, even if the weight of the single crystal 10 is heavy, it is reliably prevented from falling. Further, as shown in FIG. 3, the single crystal 10 has four holding plates 34 even when the large diameter portion 13 is not symmetrical.
Since the outer peripheral surface is surface-supported by this, there is no inclination and concentricity with respect to the pulling shaft is maintained. Further, according to this surface support, the single crystal 10 can be reliably pulled up while maintaining the concentricity with respect to the pulling axis even when the large diameter portion 13 which is the hooking portion does not exist. Such an effect is further assured by providing a protrusion that digs into the outer peripheral surface of the single crystal 10 on the inner surface of the holding plate 34 to prevent the single crystal 10 from slipping.

The size of the holding plate 34 is preferably 30 mm to 100 mm in height and 0.1 to 0.2 times the circumferential length of the single crystal 10 in the circumferential direction.
If the holding plate 34 is too small, the effect of preventing the tilt of the single crystal 10 is small, but even if it is larger than necessary, the effect does not increase.

The number of holding plates 34, that is, the number of surface supporting points, may be two or more, and the individual supporting area can be reduced as the number of surface supporting points increases.

When growing an 8-inch silicon single crystal, the pulling apparatus shown in FIGS. 1 to 3 was used. For comparison, a general pulling device without a fall prevention measure and a conventional device for supporting the scratched portion formed on the top portion of the single crystal with four claws were used. Table 1 shows the maximum error of the dislocation ratio and the crystal diameter in each case. The dislocation generation rate is the ratio of the number of times of occurrence of dislocation generation to the total number of times of pulling.

[0028]

[Table 1]

As can be seen from Table 1, even when this pulling apparatus is used, the dislocation ratio and the maximum error are substantially the same as those without any countermeasure. On the other hand, in the case of the conventional device that clamps the cut portion, these are significantly increased. It is clear that the pulling device does not substantially cause the adverse effect of preventing the single crystal from falling.

In the above example, the straight body portion 1 of the single crystal 10 is used.
Although the vicinity of the uppermost part of 2 is held, a small-diameter straight body part separately formed on the top part of the single crystal 10 may be held.

[0031]

As described above, since the single crystal pulling apparatus of the present invention directly holds the single crystal without depending on the seed crystal, even if the single crystal exceeds 200 kg, the single crystal can be surely prevented from falling. be able to. In addition, since the outer peripheral surface of the single crystal is surface-supported when holding the single crystal, the concentricity of the single crystal can be maintained even if the constricted portion formed on the single crystal is asymmetric with respect to the pulling axis. It is possible to avoid as much as possible the adverse effect on pulling due to the prevention of crystal falling. Further, since it is also possible to hold the slit portion independently of the slit portion, the slit portion can be made small, and finally it can be omitted. Therefore, it is possible to reduce a decrease in yield due to the formation of the cut portion.

[Brief description of drawings]

FIG. 1 is an elevational view showing the configuration of the main part of an example of a single crystal pulling apparatus embodying the present invention.

FIG. 2 is a view taken along the line AA of FIG. 1;

FIG. 3 is an elevational view showing a holding state of a single crystal.

[Explanation of symbols]

 10 Single Crystal 20 Pulling Device Main Body 22 Wire 23 Seed Chuck 30 Single Crystal Pulling Means 31 Wire 32 Elevating Base 33 Holding Arm 34 Holding Plate 35 Operation Block 40 Seed Crystal

Claims (1)

[Claims] 1. A pulling apparatus main body for pulling a single crystal from a raw material melt by a CZ method while rotating it, and a second single crystal pulling for pulling the single crystal while supporting a plurality of circumferential positions of its outer peripheral surface. And a means for pulling a single crystal.