JPH10139584A - Method for pulling up single crystal and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which the single crystal can safely be pulled up without causing falling of the crystal at the time of producing a single crystal having a great weight and also to provide the device for the method. SOLUTION: (1) This method for pulling up a single crystal by a Czochralski method comprises: forming a neck part in a single crystal 3 by a single crystal pulling-up means 4; then, gripping the neck part by using a pair of holding jigs 9 moveably engaged with a holding frame 8; and thereafter, pulling up the single crystal 3 in cooperation with the single crystal pulling-up means 4. (2) This device is provided with: the single crystal pulling-up means 4 for forming the neck part; a holding frame adjustment means 5 for adjusting the height of the holding frame 8; and a holding jig adjustment means 6 for adjusting the position of the holding jigs 9 moveably engaged with the holding frame 8; wherein these means 4, 5 and 6 are coaxially arranged with each other and the neck part of the single crystal 3 is gripped with the holding jigs 9 to pull up the holding frame 8 and holding jigs 9 in cooperation with the single crystal pulling-up means 4. In the device, desirably, the fixed frame 8d is formed into a staircase shape and the position adjustment of the holding jigs 9 movably engaged with the holding frame 8 is performed by elevating/lowering the pair of jigs 9 with two wires 10 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulling method for producing a single crystal by the Czochralski method (hereinafter referred to as "CZ method") and an apparatus therefor. The present invention relates to a method and apparatus for pulling a single crystal that can be safely pulled without causing the single crystal to fall.

[0002]

2. Description of the Related Art There are various methods for producing a single crystal. Among them, the CZ method is widely applied in a method capable of industrial mass production for growing a silicon single crystal.
In the production of a single crystal by this method, the seed crystal is brought into contact with the surface of the melt of the crystal raw material contained in the crucible, and the crucible is rotated, and the seed crystal is pulled upward while rotating in the opposite direction. Thereby, a single crystal in which the melt is solidified grows at the lower end of the seed crystal.

When a single crystal is produced by the CZ method,
When the seed crystal is brought into contact with the melt, it is necessary to completely remove dislocations generated by the thermal shock so that the dislocation does not reach the main body of the grown single crystal. Usually, as this measure, in order to eliminate dislocations from the crystal surface and make the single crystal dislocation-free,
A so-called "neck process" is employed in which the diameter is narrowed and elongated. At this time, the diameter of the neck portion necessary for eliminating dislocations is 3 to 4 mm, and its mechanical strength is about 200 kg.

Conventionally, the weight of a single crystal produced by the CZ method has been limited to about 120 to 130 kg, but in recent years there has been a strong demand for more efficient semiconductor production. And the weight of the single crystal becomes 2
Cases exceeding 00 kg have come to be assumed. As described above, the load that can be borne by the neck portion of the single crystal is limited, and if the single crystal becomes too heavy and torsion or bending stress is applied during pulling, the neck portion of the single crystal is broken and the single crystal is crucible. It may fall into the melt inside, causing damage to the lifting device, outflow of the melt, and even a steam explosion, which may lead to personal injury.

[0005] Therefore, in order to prevent an accident such as dropping during pulling which is expected to frequently occur with the increase in the weight of the single crystal, a method of eliminating dislocations at a neck portion having a large diameter, or A method of mechanically holding a single crystal has been attempted, but the latter method has been conventionally proposed. For example, Japanese Patent Application Laid-Open No. 62-288191 discloses a basic concept of mechanically holding a single crystal by providing an engaging portion on the single crystal. Japanese Patent Application Laid-Open No. 295893 proposes a pulling apparatus in which the means for holding a single crystal is improved. That is, by forming an engaging step on the upper part of the single crystal and adopting a structure in which the engaging step is engaged and gripped by a plurality of claws or a plurality of grip holders having claws, The single crystal is prevented from falling.

For this reason, it is stated that the use of the proposed pulling apparatus makes it possible to pull the single crystal reliably and safely even when pulling a heavy single crystal.

[0007]

In the pulling technique based on the CZ method, it is difficult to form a constricted portion uniformly on the pulling axis of a single crystal. However, when the single crystal is grown while holding the single crystal in a state where the constricted portion of the single crystal is displaced from the pulling axis, the roundness of the single crystal is impaired, and the accuracy of diameter control is reduced. In addition, the single crystal is not uniformly engaged and gripped by the gripping means, and the weight burden of the single crystal is applied only to the gripping means that is engaged. Then, the engagement by the gripping means is extremely poor in stability, and may be disengaged. For this reason, in the lifting device disclosed in Japanese Patent Application Laid-Open No. 3-285893, a holding means for holding the engagement so as not to be disengaged is provided as a countermeasure for these, and the engagement and gripping of the gripping means is ensured. I have.

FIG. 6 is a view for explaining a means for holding a single crystal used in a pulling apparatus proposed in Japanese Patent Application Laid-Open No. 3-285893. That is, a constricted portion 3e is formed on the upper part of the single crystal 3 grown at the tip of the seed chuck 7 to form an engagement step, and this engagement step is formed into an L-shaped gripping lever having a plurality of claws 38. The structure supported by 39 is adopted. Then, the grip lever 39 is held by a ring 40 so that the support is not released when the grip lever is supported by the grip lever. In this way, even when the load of the single crystal 3 is unevenly applied to the gripping lever 39, the single crystal is prevented from dropping during the pulling by the pulling wire.

Certainly, with the proposed gripping means, it is possible to prevent the single crystal from falling during pulling. However, since the engagement and gripping is performed by a plurality of claws, the single crystal is held by the point contact at the engagement step portion, so that significant stress concentration occurs. For this reason, unexpected breakage may occur at the engaging step portion of the single crystal, or the single crystal may be twisted during pulling and the single crystal may be greatly inclined, and the claws or grip holders may be disengaged and drop the single crystal. Is worried.

In the proposed pulling apparatus, a plurality of claws, gripping levers and rings are arranged in the pulling region of the single crystal, and these are raised and lowered simultaneously with the single crystal pulling means. When dislocations occur in the initial stage, the crystals cannot be melted again and pulled up again, that is, remelting cannot be performed. For this reason, a certain limit is imposed on the yield of growing single crystals, which is contrary to the above-mentioned demand for increasing the efficiency of semiconductor manufacturing.

The present invention solves the above-described problems of the conventional pulling apparatus, avoids stress concentration due to point contact, ensures the holding of the constricted portion of the single crystal, and further reduces the occurrence of dislocations. An object of the present invention is to provide a single crystal pulling method and a single crystal pulling method capable of efficiently producing a single crystal without causing a falling accident even when a heavy crystal is pulled, sometimes allowing a remelting operation. It is an object.

[0012]

According to the method and apparatus for pulling a single crystal of the present invention, the seed crystal is brought into contact with the surface of the melt by the single crystal pulling means, and then pulled up while rotating to perform a neck process. Is increased or decreased to form a constricted portion, and the shoulder portion of the single crystal and the main body of the single crystal are grown. On the other hand, the weight increases with the progress of pulling the single crystal, but before reaching the limit of the load that can be borne by the neck portion of the single crystal, the holding frame and the holding jig sandwich the narrow portion of the single crystal. Then, the process shifts to holding the single crystal by the holding frame and the holding jig. Therefore, the gist of the present invention is, as shown in FIGS. 1 and 2, the following (1) a method for pulling a single crystal and (2) an apparatus therefor.

(1) In a single crystal pulling method in which a crystal is grown by pulling while rotating by the CZ method, the diameter of the single crystal 3 is increased by the single crystal pulling means 4 and then reduced to reduce the constricted portion 3e. Forming a single crystal, and holding the constricted portion between a pair of holding jigs 9 loosely fitted to the holding frame 8 and pulling the single crystal in synchronization with the single crystal pulling means. Top method.

(2) A single crystal pulling means 4 for increasing the diameter of the single crystal 3, which is pulled while being rotated, and then reducing the diameter to form a constricted portion 3e, and raising and lowering the holding frame 8 to raise and lower the height. Holding frame adjusting means 5 for adjusting, and holding jig adjusting means 6 for adjusting the position of holding jig 9 loosely fitted to the holding frame.
Wherein the holding frame adjusting means 5 and the holding jig adjusting means 6 are arranged coaxially with the single crystal pulling means 4 and the constricted portion of the single crystal is fixed to the holding frame 8. Characterized in that the holding frame (8) and the holding jig (9) are pulled up in synchronism with the single crystal pulling means (4) while being held by a holding jig (9) supported by a fixed frame (8d) provided at the lower part of the frame. Upper device.

In the above-described lifting device, the fixed frame 8d provided below the holding frame 8 is formed in a stepped shape, and the position of the holding jig 9 loosely fitted to the holding frame is adjusted by raising and lowering the wire 10. It is desirable that this be done.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The form of a single crystal pulling apparatus used in the method of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 are cross-sectional views of an essential part for explaining an entire configuration example of a single crystal pulling apparatus used in the method of the present invention. FIG. 1 is a front view and FIG. Is shown. As shown in both figures, a crucible 1 is disposed at a central position in a vacuum chamber (not shown), and a melt 2 in which polycrystalline silicon as a raw material is melted is held in the crucible 1. Above the crucible 1, a seed chuck 7 attached to the tip of the single crystal pulling means 4, and a holding frame adjusting means 5
A holding frame 8 supported at a lower end of the holding frame 8 is disposed.
A pair of holding jigs 9 that can be individually and individually moved and adjusted are loosely fitted therein. 1 and 2 show that the height position of the holding jig 9 is adjusted by raising and lowering the holding jig wire 10 of the holding jig adjusting means 6, but in the present invention, similar operations are performed. Can be achieved, other methods may be used for adjusting the height position of the holding jig 9.

In the process of growing the single crystal, although the specific structure is not shown, the single crystal is rotated in a certain direction by the single crystal pulling means 4 and is pulled upward in accordance with the growth rate of the crystal. On the other hand, the holding frame adjusting means 5 supports the holding frame 8 in the pulling region of the single crystal, and further adjusts the height position of the holding frame 8, and therefore performs a lifting operation by a mechanism (not shown). The holding jig adjusting means 6 adjusts the position of the holding jig 9 in the holding frame 8 by elevating the holding jig wire 10, for example. Therefore, the relationship between the single crystal pulling means 4, the holding frame adjusting means 5 and the holding jig adjusting means 6 is coaxially arranged in FIGS. 1 and 2, respectively. The adjusting means 6 and the single crystal pulling means 4 operate in separate systems. However, as described later, after holding the constricted portion of the single crystal with the holding frame 8 and the holding jig 9, the holding frame adjusting means 5 and the holding jig adjusting means 6 are synchronized with the single crystal pulling means 4. It has a rotating and ascending structure.

In the apparatus of the present invention, when the single crystal and the holding jig are pulled up, the single crystal pulling means 4 is connected to the holding frame adjusting means 5.
Since it is a separate system from the holding jig adjusting means 6,
Even if the constricted portion of the single crystal is displaced from the pull-up axis, the displacement can be easily adjusted, and the roundness of the single crystal can be prevented from being impaired and the diameter control accuracy can be prevented from being degraded.

On the other hand, as described above, the single crystal pulling means 4, the holding frame adjusting means 5, and the holding jig adjusting means 6 are arranged coaxially and their rotation speeds are tuned. Trouble in growing a single crystal can be prevented. In the apparatus of the present invention, the operation of the holding frame adjusting means 5 and the holding jig adjusting means 6 is different from the operation of the single crystal pulling means 4, and the holding frame 8 and the holding jig 9 are operated by the single crystal pulling means. Since the crystal can be moved up and down independently of the crystal 4, it is possible to remelt a crystal that has undergone dislocation in the initial stage of growing a single crystal.

At the tip of the single crystal pulling means 4, a single crystal seed
A seed chuck 7 holding 3a is attached, and the neck portion 3b, a portion 3c for increasing the diameter of the single crystal (hereinafter referred to as "increased diameter portion") and the diameter of the single crystal are increased by the pulling operation of the single crystal pulling means 4. A constricted portion 3e composed of a reduced portion 3d (hereinafter, referred to as a "reduced diameter portion") and a shoulder 3f are formed.

On the other hand, a holding frame 8 is attached to the tip of the holding frame adjusting means 5, and a holding jig 9 is loosely fitted below the holding frame 8 so that the height position can be adjusted freely.

As shown in FIG. 2 and FIG. 3, which will be described later, the structure of the holding frame 8 is a holding outer frame 8a forming an upper appearance of the holding frame.
A jig guide frame 8c and a fixed frame 8d are provided at a lower portion, and a holding jig 9 is loosely fitted between the jig guide frame 8c and the fixing frame 8d. The height position of the holding jig wire 10 is guided through the wire guide frame 8b. Adjusted by ascending or descending. The holding jig 9 is shown in FIG.
As shown in FIG. 4 to be described later, it is composed of a holding rod 9a and a lateral displacement prevention plate 9b, and it is desirable to provide a conical cut in the center of the holding rod 9a.

When holding the constricted portion 3e of the single crystal, the holding frame 8 is lowered and the fixed frame 8d is positioned below the constricted portion 3e. Next, the holding jig 9 which was relatively above,
By lowering the holding jig wire 10, the fixed frame 8d
And moves downward, and is located below the constricted portion 3e.
That is, it is desirable to lower the notch provided at the center of the holding rod 9a so that the notch contacts the constriction 3e of the single crystal. After that, the holding frame adjusting means 5 is operated to raise the holding jig 9 until the holding rod 9a is compressed and fixed to the fixed frame 8d, thereby holding the constricted portion 3e of the single crystal.

Although FIGS. 2 and 3 show the stepped fixing frame 8d, the present invention is not limited to this. The holding jig 9 is fixed by the operation of the holding jig adjusting means 6. Any shape may be used as long as it can move as appropriate along the frame 8d.
In addition, by providing a conical notch in the center of the holding rod 9a, the weight of the single crystal is borne by the linear or planar contact portion, so that stress concentration can be avoided and large weight Even if a single crystal is pulled, it can be safely grown. Further, since a fine adjustment space (s dimension shown in FIG. 1) is provided between the lateral displacement prevention plate 9b and the fixing frame 8d of the holding frame 8, when the load is applied, the pulling shaft is finely adjusted by the load. Is possible.

Next, a specific operation procedure will be described. At the start of pulling the single crystal, the holding frame pulling means 5 waits while holding the holding frame 8 upward. At least the lower end of the holding frame 8 is held above the single crystal seed 3a. On the other hand, the single crystal seed 3a attached to the tip of the single crystal pulling means 4 via the seed chuck 7 is brought into contact with the center of the liquid surface of the silicon melt 2 to stabilize the melt. afterwards,
The single crystal pulling means 4 is operated to slowly raise the single crystal seed 3a while rotating it, thereby forming the neck 3b.
Next, the pulling speed of the single crystal is reduced to increase the diameter of the single crystal 3c.
Is formed, and then the pulling speed is increased to reduce the diameter of the single crystal 3d.
Is formed to form a constricted portion 3e of a single crystal.

After forming the constricted portion 3e of the single crystal, the diameter of the single crystal is increased again to form the shoulder 3f, and then the pulling speed and the rotation speed are adjusted to the steady conditions to adjust the single crystal 3 having a predetermined diameter.
Move to the main body pulling.

After the transition to the pulling of the single crystal under the steady condition, when the weight of the single crystal to be pulled reaches a certain weight or when the pulling length becomes a certain length, the holding which has been waiting above is held. The frame 8 is lowered so that its lower end is sufficiently below the constriction 3e of the single crystal. Thereafter, the holding jig adjusting means 6 is operated to move the holding jig 9 between the jig guide frame 8c and the fixed frame 8d via the holding jig wire 10. At this time, it is desirable that the cut portion at the center of the holding rod 9a be moved to the vicinity of the constricted portion of the single crystal.

Then, the holding frame 8 is gradually raised by the holding frame adjusting means 5, and the constricted portion 3 e of the single crystal is held by the holding jig 9. Thereafter, the holding frame adjusting means 5 and the holding jig adjusting means 6 raise the holding frame 8 and the holding jig 9 in synchronization with the pulling speed of the single crystal pulling means 4.

[0030]

The effects of the method and apparatus of the present invention will be described below based on specific examples (Examples of the present invention and Comparative Examples 1 to 3).

(Example of the Present Invention) Using the pulling apparatus shown in FIGS. 1 and 2, a silicon single crystal having a diameter of 12 inches (305 mm) and a pulling length of 1000 mm was grown. At this time, the polycrystalline silicon was charged at 300 kg.

FIG. 3 is a diagram showing the dimensions of the holding frame used in the embodiment, and FIG. 4 is a diagram showing the dimensions of the holding jig used in the embodiment. At the start of the pulling of the single crystal, the holding jig was made to stand by with the holding frame loosely fitted therein being held upward.
On the other hand, the single crystal seed attached to the tip of the single crystal pulling means is brought into contact with the silicon melt 2, and thereafter the single crystal pulling means 6 is operated to slowly raise the single crystal seed while rotating it. A single crystal neck portion, a constricted portion and a shoulder portion having the shape and dimensions shown in FIG.

After shifting to pulling the main body of the single crystal, the pulling weight becomes
At the time of reaching 100 kg, the holding frame was lowered, the constricted part of the single crystal was held by the holding jig, and a total of 30 pieces were grown,
This was designated as the primary lift. Normally, when dislocations occur during the primary pulling, as described above, the dislocations are remelted and pulled up again to make the final pulling. In the example of the present invention, remelting was performed, and primary lifting and final lifting were performed. Table 1 shows the results of the number of dislocations, the number of drops, and the total dislocation-free length of the grown single crystal when a total of 30 crystals were pulled.

(Comparative Example 1) As a comparative example of a mechanical holding method of a single crystal, a gripping means shown in FIG.
Using a holding jig proposed in Japanese Patent No. 5893, a silicon single crystal similar to that of the present invention was grown.

A single crystal neck portion having the shape and dimensions shown in FIG.
After forming the constricted part and shoulder, and moving to pulling the main body of the single crystal, when the pulling weight reaches 100 kg, the gripping lever with two claws is operated and the constriction of the single crystal is made with two claws. The parts were engaged and gripped, and a total of 30 plants were grown. In Comparative Example 1, since remelting was not possible, final pulling was not performed, but only primary pulling was performed. Table 1 shows the pulling results at this time.

(Comparative Example 2) As in the case of the present invention, a 12-inch diameter (305 m
In m), a total of 30 silicon single crystals with a pulling length of 1000 mm were grown. However, the single crystal neck shown in FIG.
After forming a length of 30 mm), the shoulder was formed and the main body of the single crystal was pulled without forming a constricted portion. Therefore, the holding frame and the holding jig used in the example of the present invention were not used at all. At this time, the primary pull-up and the final pull-up were performed, and the results are shown in Table 1.

(Comparative Example 3) As in the case of the present invention, a 12 inch diameter (305 m
In m), a total of 30 silicon single crystals with a pulling length of 1000 mm were grown. However, a large diameter single crystal neck (diameter 8 mm, length
200 mm), the shoulder was formed, and the main body of the single crystal was pulled without forming a constricted portion. Therefore, the holding frame and the holding jig used in the example of the present invention were not used at all. At this time, the primary pull-up and the final pull-up were performed, and the results are shown in Table 1.

[0038]

[Table 1]

As is clear from Table 1, in Comparative Example 1, three single crystals dropped, and in Comparative Example 2, no holding jig was used. Further, in Comparative Example 3, although no drop occurred, all single crystals were dislocated due to the large diameter neck portion. On the other hand, in the example of the present invention, five dislocations occurred during the primary pulling, but all of the dislocations were pulled without dislocation at the final pulling. In addition, since the single crystal did not drop during the pulling and the remelting operation was possible, a good result was obtained with respect to the total dislocation-free length of the grown single crystal.

[0040]

According to the method and apparatus for pulling a single crystal of the present invention, stress concentration due to point contact can be avoided to ensure the holding of the constricted portion of the single crystal, and the remelting operation can be performed when dislocations occur. It is possible to efficiently manufacture a single crystal without causing a fall accident even when a heavy crystal is pulled.

[Brief description of the drawings]

FIG. 1 is a front view showing a cross section of a main part for explaining an example of the entire configuration of a single crystal pulling apparatus used in a method of the present invention.

FIG. 2 is a side view showing a cross section of a main part for explaining an example of the entire configuration of a single crystal pulling apparatus used in the method of the present invention.

FIG. 3 is a diagram showing the shape and specific dimensions of a holding frame used in an example.

FIG. 4 is a view showing the shape and specific dimensions of a holding jig used in the embodiment.

FIG. 5 is a view showing shapes and dimensions of a single crystal neck, a constricted portion, and a shoulder formed in an example.

FIG. 6 is a view for explaining a means for holding a single crystal used in a pulling up device proposed in the prior application.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Crucible, 2 ... Melt, 3 ... Single crystal 3a ... Single crystal seed, 3b ... Neck 3c ... Increased diameter part, 3d ... Reduced diameter part 3e ... Constriction part, 3f ... Shoulder part 4 ... Single crystal pulling means 5: holding frame adjusting means 6: holding jig adjusting means 7: seed chuck 8: holding frame, 8a: holding outer frame 8b: wire guide frame, 8c: jig guide frame 8d: fixing frame 9: holding jig 9a: Holding rod, 9b: Side slip prevention plate 38: Claw, 39: Grip lever 40: Ring

Claims (3)

[Claims] In a single crystal pulling method for growing a crystal by rotating and pulling it by a Czochralski method, a diameter of the single crystal is increased by a single crystal pulling means and then reduced to form a constricted portion. Then, the constricted portion is sandwiched between a pair of holding jigs loosely fitted to a holding frame, and the single crystal is pulled up in synchronization with the single crystal pulling means. 2. A single crystal pulling means for forming a constricted portion by increasing the diameter of a single crystal which is pulled while being rotated and forming a constricted portion, and a holding frame adjusting means for raising and lowering the holding frame to adjust its height. And a holding jig adjusting means for adjusting the position of the holding jig loosely fitted to the holding frame, wherein the holding frame adjusting means and the holding jig adjusting means are The constricted portion of the single crystal is disposed coaxially with the crystal pulling means, and is held in synchronization with the single crystal pulling means by holding a narrow portion of the single crystal by a holding jig supported by a fixed frame provided at a lower portion of the holding frame. A single crystal pulling apparatus characterized by pulling up a frame and a holding jig. 3. A fixing frame provided at a lower portion of the holding frame is formed in a step shape, and a position of the holding jig loosely fitted to the holding frame is adjusted by lifting and lowering a wire. Item 3. A single crystal pulling apparatus according to Item 2.