JP2956574B2 - Single crystal pulling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 of a silicon wafer used for manufacturing a semiconductor device, a silicon single crystal grown by a CZ method is frequently used. As is well known, in growing a silicon single crystal by the CZ method, a seed crystal is attached to the lower end of a pulling shaft, the seed crystal is immersed in a silicon melt generated in a quartz crucible, and the seed crystal is rotated from this state. While pulling, 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 several tens of mm, the upper end of which is connected to a seed chuck, and the lower end of which is immersed in a silicon melt. When the seed crystal is immersed in the silicon melt, dislocations are introduced by thermal shock. A so-called seed squeezing is carried out for the purpose. The diameter of the seed drawing portion is required to be 5 mm or less from the viewpoint of eliminating dislocations, and is desirably 3 mm or less.

Meanwhile, a silicon single crystal grown by the CZ method has a diameter of 8 inches and a weight of 100.
Those around kg were the mainstream. However, recently, a further increase in the diameter is required, and the growth of a silicon single crystal having a diameter of 12 inches or more is also being planned. As the diameter of the single crystal increases, the weight naturally increases, and when the diameter is 12 inches, the weight reaches 200 kg.

[0005] The weight of the single crystal during the growth is concentrated on the seed crystal, particularly at the seed drawing part. When the crystal weight increases, the load applied to the seed drawing part also increases, but the breaking strength of silicon is 20 kg / m2.
m ² and about, in order to securely hold the silicon single crystal of 200kg is required for seed throttle portion diameter greater than 5mm be underestimated. However, if the diameter exceeds 5 mm, it is impossible to make the seed crystal dislocation-free.
Therefore, it is impossible to grow a single crystal reaching 200 kg with the current technology.

In order to solve such a problem, Japanese Unexamined Patent Publication No. 5-65477 discloses a method in which a crack is formed at the top of a single crystal, and the crack is clamped from the periphery with a plurality of claws to form a single crystal. A seeding-independent pulling technique is shown.

[0007]

The technique of directly clamping a crack formed on a single crystal is a technique for securely pulling up a single crystal exceeding 200 kg and preventing its fall unless a clamp claw is carelessly opened. it can. However, it is difficult to form a crack portion symmetrical with respect to the crystal pulling axis with the current growth technique. For this reason, when a single crystal is grown by clamping a cracked portion, the single crystal loses core circularity, causing problems such as dislocations and reduction in diameter control accuracy. Further, the single crystal has a meandering shape in the direction of the pulling axis, and an increase in the cutting allowance due to the cutting of the outer peripheral portion in a later step also poses a serious problem.

An object of the present invention is to provide a single crystal pulling apparatus capable of reliably preventing a single crystal exceeding 200 kg from dropping and avoiding as much as possible adverse effects on pulling due to the prevention. It is in.

[0009]

SUMMARY OF THE INVENTION A single crystal pulling apparatus of the present invention comprises a pulling apparatus body for pulling a single crystal from a raw material melt while rotating the single crystal by a CZ method, and forming a crack at a top portion of the single crystal; An annular base which rises together with the single crystal in a state where a single crystal top portion is present, and a plurality of crystal holding members which are arranged in a plurality of circumferential positions of the annular base in a crystal radial direction and are movable in the crystal radial direction. idea,
Means for converting the load of the annular base into a driving force in the direction of the crystal center of the plurality of crystal holding pins.

In the single crystal pulling apparatus of the present invention, a plurality of crystal holding pins are fitted into the crevice portion in a non-contact state with the outer surface of the crystal, and the annular base is raised in this state, so that the single crystal can be formed as in the prior art. It is held by the seed crystal and pulled up. When the single crystal falls due to the destruction of the seed crystal, the large-diameter portion above the crack portion is caught by the plurality of crystal holding pins.
Then, the load of the single crystal is applied to the annular base via the plurality of crystal holding pins, and apparently the load of the annular base increases. As a result, the driving force of the plurality of crystal holding pins toward the crystal center increases. Thus, the single crystal is securely held by the plurality of crystal holding pins.

It is also possible to directly hold a single crystal being pulled by bringing a plurality of crystal holding pins into contact with the outer surface of the crystal. Also in that case, the single crystal can be reliably held by utilizing the load. However, in this case, it is necessary to rotate the annular base in the circumferential direction.

[0012]

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

This pulling apparatus is a pulling apparatus main body 30 for pulling a silicon single crystal 10 from a silicon raw material melt.
And a single crystal holding mechanism 40 provided in a pull chamber 31 of the pulling apparatus main body 30 to prevent the single crystal 10 from falling during pulling.

The pulling device main body 30 is basically the same as a conventional pulling device. A seed chuck 33 is attached to a lower end of a wire 32 that passes through a pull chamber 31 and hangs down in a main chamber, and is attached thereto. Seed crystal 20
The single crystal 10 is grown below the seed crystal 20 by rotating the wire 32 while rotating the wire 32 from a state of being immersed in the raw material melt, and pulled into the pull chamber 31. By controlling the pulling speed and the like in the early stage of the growth, the cracked portion 11 is formed at the top of the single crystal 10.

The pull chamber 31 of the pulling apparatus main body 30
The single crystal holding mechanism 40 provided therein has an annular base 41 through which a wire 32 passes through an inner central portion. The annular base 41 is supported inside the pull chamber 31 by a ring 42 and a bearing 43 so as to be vertically movable and rotatable. That is, the ring 42 can be moved up and down by being guided by a plurality of vertical ribs 44 provided on the inner surface of the pull chamber 31, and the annular base 41 is supported inside the ring 42 via the bearing 43. The annular base 41 is suspended and supported by a plurality of wires 46 hanging from a plurality of outer peripheral portions of a circular support plate 45 which rises on the seed chuck 33.

At a plurality of circumferential positions on the annular base 41, a plurality of crystal holding pins 4 corresponding to the positions of the wires 46 are provided.
7 are provided. Each of the crystal holding pins 47 faces the radial direction of the pull chamber 31, that is, the crystal radial direction, and is supported movably in the crystal radial direction. Then, the wire 46 is wound around a pinion gear in the annular base 41 in a state where the support plate 45 is superimposed on the annular base 41, so that the crystal holding pin 47 is fixed to the retracted position on the outer peripheral side. When the support plate 45 superimposed on the annular base 41 rises and separates from the annular base 41, the wire 46 is pulled out from the annular base 41 and the pinion gear rotates, so that the crystal holding pin 47 is moved to the crystal on the inner peripheral side. Move forward to the holding position.

The diameter of a circle passing through the tips of the plurality of crystal holding pins 47 is the maximum diameter of a portion of the single crystal 10 above the crevice 11 in a state where the crystal holding pins 47 are in the retracted position on the outer peripheral side. In the state where the crystal holding pin 47 is located at the crystal holding position on the inner peripheral side, the diameter is set to be smaller than the maximum diameter and larger than the minimum diameter of the crevice portion 11.

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

The seed chuck 33 of the pulling apparatus main body 30
The seed crystal 20 attached to the crucible placed in the main chamber is immersed in the raw material melt and raised while rotating the wire 32 to perform seed drawing. Then, a shoulder portion and a straight body portion are formed in this order.

At this time, the annular base 41 of the single crystal holding mechanism 40 is held in the lower end of the pull chamber 31, and the support plate 45 is placed on the annular base 41. Therefore, the plurality of crystal holding pins 47 are located at the retracted positions on the outer peripheral side.

As the growth of the single crystal 10 proceeds, the seed chuck 33 passes through the inside of the annular base 41 in the pull chamber 31 and hits the support plate 45. Then, the support plate 4
5 is placed on the seed chuck 33 and the seed chuck 33
It starts to rise while rotating with it. As a result, the wire 46 is pulled out from the annular base 41, and the plurality of crystal holding pins 47 advance at the same time. When the drawing of the wire 46 is completed, the movable pin 47 reaches the crystal holding position on the inner peripheral side. At this point, the single crystal 10 is grown so that the crack portion 11 of the single crystal 10 is located inside the plurality of crystal holding pins 47, so that the plurality of crystal holding pins 47 It fits inside the crack portion 11 in a non-contact state with the outer surface of the crystal.

When the drawing of the wire 46 is completed, the annular base 41 is pulled by the wire 46 and rises together with the single crystal 10. In addition, when the support plate 45 rotates together with the seed chuck 33, the support plate 45 rotates in the circumferential direction at the same speed as the single crystal 10.

If the seed crystal 20 breaks during or after the growth of the single crystal 10, the portion of the single crystal 10 above the crack portion 11 is hooked on each tip of the plurality of crystal holding pins 47. Then, the load of single crystal 10 is applied to annular base 41 via crystal holding pin 47, and as a result, the load of annular base 41 increases. This load is applied to the wire 46
Therefore, the driving force of the crystal holding pin 47 toward the inner peripheral side increases.

Therefore, the single crystal 10 is reliably prevented from falling. When the single crystal 10 is grown normally, the crystal holding pins 47 do not come into contact with the outer surface of the crystal, and the pulling by the seed crystal 20 is performed in the conventional manner. Adverse effects are avoided.

When the tips of the plurality of crystal holding pins 47 are brought into contact with the outer surface of the crystal of the crack portion 11, the crack portion 1 is formed by utilizing a part of the load of the single crystal 10.
1 is held by the crystal holding pins 47, and the holding force increases as the single crystal 10 becomes heavier, so that the single crystal 10 exceeding 200 kg can be grown.

The present pulling apparatus was used to grow a silicon single crystal having a diameter of 8 inches and a weight of 150 kg. The crystal holding pins 47 in the single crystal holding mechanism 40 did not come into contact with the crystal outer surface of the crack portion. Although the seed crystal was intentionally destroyed by intermittent pulling after the liquid separation, the single crystal was securely held by the crystal holding pin 47 and its falling was prevented.

When growing a single crystal having a diameter of 8 inches and a weight of 150 kg using the pulling apparatus, the seed crystal is narrowed down to 2 mm where final pulling is impossible, while the single crystal holding mechanism 40
The contact portion held the cracked portion. As a result, the growth of the single crystal could be completed without damaging the seed crystal.

The number of the crystal holding pins 47 is four in the illustrated example. However, if the number is three or more, the single crystal 10 can be reliably prevented from falling.

[0029]

As described above, the single crystal pulling apparatus of the present invention has a plurality of crystal holding pins driven by using a load. Also in this case, the single crystal can be reliably prevented from falling. By making the crystal holding pin non-contact with the outer surface of the crystal, it is possible to avoid as much as possible an adverse effect on pulling due to prevention of the single crystal from falling. Therefore, it is very effective in establishing a technique for growing a large-diameter single crystal.

[Brief description of the drawings]

FIG. 1 is an elevation view showing a 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;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Single crystal 11 Crack part 20 Seed crystal 30 Pulling apparatus main body 31 Pull chamber 32 Wire 33 Seed chuck 40 Single crystal holding mechanism 41 Annular base 46 Wire 47 Crystal holding pin

Claims (1)

(57) [Claims] 1. A pulling apparatus body for pulling a single crystal from a raw material melt while rotating it by a CZ method, and forming a crack at the top of the single crystal, and a single crystal in a state where the single crystal top is present inside the single crystal. An annular base that rises together with the plurality of crystal holding pins, the plurality of crystal holding pins being arranged in a plurality of positions in the circumferential direction of the annular base in the radial direction of the crystal, and being movable in the crystal radial direction; Means for converting the driving force into a driving force in the direction of the center of the crystal.