JP2000044382A - Production of single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a single crystal, so designed as to hold a single crystal when a to-be-held portion of the single crystal stands at such a temperature as to exhibit ductility to secure effective contact area between the single crystal and the holding claw of a single crystal holder and enable the single crystal to be safely held through preventing its chipping. SOLUTION: This method for producing a single crystal comprises the following procedure: a seed crystal 4 attached to a seed holder 3 is immersed in a melt 5 to form a neck part, and the larger-diameter part 6a, narrow part 6b, shoulder part 6c, and cylindrical part 6d of a single crystal 6 are formed; after the larger-diameter part 6a is brought to a specified diameter, the pull-up rate is raised to prevent the crystal diameter from increasing, and then regulated so as to narrowly draw the crystal diameter to form the narrow part 6b; subsequently, both the pull-up rate and melt temperature are regulated to grow the shoulder part 6c and the cylindrical part 6d; when the temperature of the narrow part 6b falls to 750-850 deg.C, a wire winding mechanism is driven to rewind a holder-suspending wire 11 and a claw-opening/closing wire 15 and the holding claw 16 of a single crystal holder 10 and the narrow part 6b are brought into contact with each other to hold the single crystal 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a semiconductor single crystal by the CZ method, and more particularly to a method for producing a single crystal suitable for pulling a heavy single crystal.

[0002]

2. Description of the Related Art Single crystal silicon is generally manufactured by the CZ method. In the CZ method, polycrystalline silicon is filled in a quartz crucible installed in a single crystal manufacturing apparatus, and the polycrystalline silicon is heated and melted by a heater provided around the quartz crucible to form a melt. Then, the seed crystal attached to the seed holder is immersed in the melt, and the seed holder is pulled up while rotating the seed holder and the quartz crucible in the same or opposite directions to grow single crystal silicon to a predetermined diameter and length. .

In a seed crystal, dislocations are generated by thermal shock when immersed in a melt. In order to remove the dislocation, a neck portion having a diameter of about 3 to 4 mm is formed below the seed crystal by using a dash neck method, and the dislocation is released to the surface of the neck portion. After dislocation-free, the shoulder is formed to expand the single crystal to a predetermined diameter, and then the process shifts to the formation of a straight body.

In recent years, the weight of single crystals has increased with the increase in the diameter or the axial length of single crystals for the purpose of improving the efficiency of semiconductor device production, improving the yield, etc., and the strength of the neck portion has reached the limit. I have. Therefore, the neck portion may be broken by the conventional crystal pulling method, and a safe single crystal growth cannot be performed. As a countermeasure, a pulling device and a pulling method for transferring the load from the neck to the holder during the growth of the single crystal have been proposed. According to such an apparatus and method, since most of the weight of the single crystal is supported by the holder, breakage of the neck portion is prevented, and even when the neck portion is broken, the single crystal can be prevented from falling by the holder. .

[0005] For example, a crystal pulling apparatus disclosed in Japanese Patent Publication No. 7-103000 has a plurality of doglegs each having a claw for holding a constricted portion of a single crystal and opening and closing by winding or unwinding a wire. The single crystal is held using a gripping lever and a ring for preventing the gripping lever from opening. The crystal pulling apparatus disclosed in Japanese Patent Publication No. 7-515, represented by a rotating claw type, has a downward rotation at a lower end of a grip holder that can move up and down along a pulling axis connected to a seed holder. In this configuration, a plurality of claws are provided to stop at a predetermined time, and these claws are engaged with a constricted portion of the single crystal to hold the single crystal. By lowering the gripping holder along the pulling axis, the tip of the claw opens upward while contacting the enlarged diameter portion of the single crystal, and returns to the closed position by its own weight when passing through the enlarged diameter portion. . In this crystal pulling device,
Since the pawl opens and closes following the enlarged diameter portion formed above the constriction, no special pawl opening / closing drive device is required. Further, the method and apparatus for growing a single crystal disclosed in Japanese Patent Application Laid-Open No. 9-2893 relate to a method in which a hanging tool is engaged with a convex or concave portion formed on the surface of a neck portion or a straight body, or The single crystal is held by attaching a hanging fixture to the outer peripheral surface of the inverted straight conical portion formed at the upper end. Furthermore, in order to stabilize the holding, Japanese Unexamined Patent Publication No. 9-183694 discloses a technique for preventing the opening of the arm and increasing the number of contact points with the single crystal.

[0006]

However, each of the above crystal pulling apparatuses has the following problems. (1) Since the contact between the holding claw and the single crystal is basically a point contact, if the weight increases as the single crystal grows, the surface pressure at the contact interface with the claw increases, and the single crystal is chipped. It is very likely to happen. When the single crystal is chipped and the fragments that have fallen into the melt reach the growth interface, the crystal is dislocated. There is also a danger that the single crystal breaks with the part where the chipping occurred as a fracture starting point. (2) In a tensile test using a constricted portion as a test piece, it was reported that the starting point of silicon breakage was a contact portion between the constricted portion and a nail. This is done in 3). (3) In recent years, silicon single crystals having a diameter of 300 mm have been manufactured, and if the diameter and the weight are further increased in the future, it is considered that crystal holding technology will be indispensable. Chipping is a serious problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has an effective contact area between a holding claw of a single crystal holder and a single crystal to prevent chipping of the single crystal. It is an object of the present invention to provide a method for producing a single crystal that can be held safely.

[0008]

Means for Solving the Problems To achieve the above object, the first of the single crystal production methods according to the present invention is to use a CZ method for growing a single crystal at the lower end of a seed crystal immersed in a raw material melt, A single crystal manufacturing method for pulling a single crystal being grown while holding the single crystal by a holder is characterized in that the single crystal is held when the temperature of the portion to be held of the single crystal shows ductility. According to the above configuration, since the single crystal is held by the holder when the single crystal is at a temperature showing ductility, the single crystal is deformed by the contact of the holder, and the holder comes into surface contact with the single crystal. become. Therefore, the surface pressure of the portion to be held is maintained at a low state, and the single crystal is kept in a stable state without the increase in the surface pressure due to the point contact of the holder and the resulting chipping of the single crystal as in the prior art. It can be pulled up while holding it. In addition, even when there is some defect in the shape of the portion to be held of the single crystal, since the single crystal is held at a temperature showing ductility, good surface contact with the holder is obtained. .

A second aspect of the method for producing a single crystal according to the present invention is the method according to the first aspect, wherein the single crystal holding portion is 750 to 8
It is characterized in that it is held by a single crystal holder when it is in a temperature range of 50 ° C. It is generally known that silicon exhibits ductility in a temperature range of 750 ° C. or higher. 7
If the temperature is lower than 50 ° C., the silicon is unlikely to exhibit ductility, and the surface pressure increases because the holder makes point contact as in the conventional case. On the other hand, when the temperature exceeds 850 ° C., the strength of the silicon is insufficient and the silicon is not suitable for holding. According to the above configuration, the holder is brought into contact when the silicon is in a temperature range showing ductility to an external force, so that the single crystal can be held in surface contact.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the method for producing a single crystal according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of a single crystal holder. A wire winding mechanism 1 is provided above the single crystal manufacturing apparatus, and a seed holder 3 is attached to a lower end of a crystal pulling wire 2 hanging from the wire winding mechanism 1. The single crystal holder 10 includes a holder main body 12 suspended from a plurality of holder hanging wires 11 hanging down from the wire winding mechanism 1 so as to surround the crystal pulling wire 2, an upper link 13, and a lower link 14.
, A plurality of claw opening / closing wires 15, one holding claw suspended from each of the plurality of claw opening / closing wires 15, and an opening stopper 17.

The holder body 12 has a shape in which a plurality of L-shaped legs 12a are fixed to the lower end of a cylinder, and the lower end of each leg 12a forms a stopper that projects substantially horizontally outward. The stopper regulates the position of the claw portion at the lower end of the holding claw 16 when the single crystal holder 10 is in the holding posture. A holding claw 16 is connected to each leg 12a via an upper link 13 and a lower link 14.
The four-bar link mechanism is constituted by 3, 14 and the holding claw 16. An opening stop 17 is rotatably attached to the outer peripheral surface of the cylindrical portion of the holder main body 12, and a recess is provided on the upper surface of the upper link 13 for engaging the free end of the opening stop 17. The free end of the stopper 17 is the holder body 1
When the holding claw 16 is lowered to a predetermined position with respect to 2, the claw is caught in the depression and the movement of the holding claw 16 is suppressed. In addition,
Although FIG. 1 shows two holding claws for easy viewing, the number of holding claws is preferably three to four.

The wire winding mechanism 1 is provided with a load cell for detecting a load applied to the claw opening / closing wire 15. The seed holder 3 can freely pass through the holder main body 12 of the single crystal holder 10.

The method for producing a single crystal according to the present embodiment is as follows. After the seed crystal 4 attached to the seed holder 3 is immersed in the melt 5 in the quartz crucible, a neck portion is formed, followed by the enlarged diameter portion 6a, the constricted portion 6b, the shoulder portion 6c of the single crystal 6, A straight body 6d is formed. After the enlarged diameter portion 6a reaches a predetermined diameter, the pulling speed is increased to stop the crystal diameter from being increased, and the narrowing portion 6b is formed by adjusting the pulling speed so as to narrow down the crystal diameter. Next, in order to form the shoulder 6c, the pulling speed and the melt temperature are adjusted to enlarge the crystal diameter so as to have a predetermined value, and the crystal is grown while maintaining a constant diameter to form the straight body 6d. Nurture. Crystal growth before holding the single crystal 6 by the single crystal holder 10 is performed by the crystal pulling wire 2, and the constricted portion 6 b is 750.
Until the temperature falls to the temperature range of ８850 ° C., the single crystal holder 10 stands by above the growing single crystal 6. At this time, the upper link 13 and the lower link 14 are maintained substantially horizontal, and the free end of the stopper 17 is in contact with the upper inside of the holding claw 16. In this state, the single crystal holder 10 is opened.
The distance between the lower ends of the holding claws 16 is the maximum. The interval is sufficiently larger than the diameter of the enlarged diameter portion 6a of the single crystal 6, and the inward movement of the holding claw 16 is suppressed by the opening stopper 17, so that the holding claw 16 is Does not come into contact with the enlarged diameter portion 6a.

When the constricted portion 6b falls to a temperature range of 750 to 850 ° C., the wire winding mechanism 1 is driven to rewind the holder hanging wire 11 and the claw opening / closing wire 15 simultaneously at a constant speed. At this time, since the single crystal holder 10 is in the "open" state, the holding claw 16 does not contact the enlarged diameter portion 6a but descends slightly below the enlarged diameter portion 6a and stops. Thereafter, the holder hanging wire 11 and the claw opening / closing wire 1
5 is wound up with the crystal pulling wire 2 at a constant speed, and the relative position between the single crystal 6 and the single crystal holder 10 is kept constant.

Next, only the claw opening / closing wire 15 is rewound, and the holding claw 16 is lowered. When the holding claws 16 come into contact with the tips of the legs 12a corresponding to the stoppers, the lowering stops. At this time, the height of the tip of the holding claw 16 is substantially equal to the height of the constricted portion 6b. Further, as the holding claw 16 descends, the free end of the opening stopper 17 slides on the upper surface of the upper link 13 and falls into the recess, so that the opening of the holding claw 16 is suppressed. In this state, the single crystal holder 10 is “closed”, and the interval between the lower ends of the holding claws 16 is minimized. The spacing is a single crystal 6
Since the tip of the leg 12a is larger than the diameter of the constriction 6b and the tip of the leg 12a is in contact with the holding claw 16, the tip of the holding claw 16 does not collide with the constriction 6b.

Thereafter, when the holder hanging wire 11 and the claw opening / closing wire 15 are simultaneously wound at the same speed and at a speed exceeding the winding speed of the crystal pulling wire 2, the single crystal holder 10 Rises, and the tip of the holding claw 16 contacts the lower conical surface of the enlarged diameter portion 6a. Then, the single crystal 6 is deformed, and the single crystal 6 is held on the entire front end portion of the holding claw 16. After completion of the holding, the rising speed of the single crystal holder 10 is controlled to be the same as the pulling speed of the single crystal 6.

In the experiment of the single crystal manufacturing method according to the present invention, the diameter of the straight body 6d was 310 mm, and when the temperature of the constricted portion 6b dropped to about 800 ° C., the holding claws 16 were closed and the single crystal holder 10 was raised. The tip of the holding claw 16 is connected to the enlarged diameter portion 6a.
In contact with the lower conical surface. The load applied to each of the plurality of holding claws 16 was detected and monitored by a load cell to balance the single crystal holder 10, and the single crystal 6 was held while uniformly applying a load to each holding claw 16. Thereafter, the single crystal 6 was pulled up by the claw opening / closing wire 15, and the single crystal production was completed through a tail forming step.

When the single crystal obtained in the above experiment was examined, the lower conical surface of the enlarged diameter portion 6a with which the holding claw 16 was in contact was deformed, and the tip of the holding claw 16 was almost in surface contact. Traces were confirmed. In addition, when the pulled single crystal was taken out of the single crystal manufacturing apparatus, each holding claw was smoothly separated from the single crystal.

[0019]

As described above, according to the present invention, C
The single crystal holder is used to hold the single crystal when the temperature of the portion to be pulled of the single crystal during pulling is ductile by using the Z method. Deformation and good surface contact with the holder are obtained. Therefore,
The surface pressure of the portion to be held is reduced, and the single crystal can be prevented from being chipped and can be held safely. In addition, by utilizing the ductility of silicon, the accuracy of the shape of the portion to be held can be reduced as compared with the related art, so that the productivity of the single crystal is improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a state in which a single crystal being grown is held by a single crystal holder.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wire winding mechanism, 2 ... Crystal pulling wire, 5 ... Melt, 6 ... Single crystal, 6a ... Large diameter part, 6b ... Constriction part, 10
... single crystal holder, 11 ... holder hanging wire, 12 ... holder body, 12a ... leg, 13 ... upper link, 14 ... lower link, 15 ... claw opening / closing wire, 16 ... holding claw, 17 ... opening prevention.

Continued on the front page (72) Inventor Junsuke Tomioka 2612 Shinomiya, Hiratsuka-shi, Kanagawa F-term (reference) in Komatsu Electronics & Metals Co., Ltd. 4G077 AA02 BA04 CF10 EG12 PG01

Claims (2)

[Claims] 1. A method for producing a single crystal, wherein a single crystal is grown at the lower end of a seed crystal immersed in a raw material melt, and the single crystal being grown is pulled up while being held by a holder.
Single crystal at the temperature where the held part of single crystal (6) shows ductility
(6) A method for producing a single crystal, comprising: 2. The holding portion of the single crystal (6) has a thickness of 750 to 850.
2. The method for producing a single crystal according to claim 1, wherein the single crystal is held by a single crystal holder when the temperature is in a temperature range of ° C.