JPH10251092A - Upper shaft lifting for apparatus for pulling up single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the accuracy of diameter control of a fixed diameter part for which the particularly high diameter accuracy of a semiconductor single crystal is required and to improve the quality of the crystal by pulling up the single crystal by a motor to be exclusively used which has its pulling up speed within a rated vertical permissible range at the time of growing this fixed diameter part. SOLUTION: The motor (servo motor) 31 for growing the fixed diameter part of which the pulling up speed (0.3 to 3.0mm/min) at a stage for growing the fixed diameter part is within the permissible range of 10% above and below the rating is started in the stage for growing the fixed diameter part for which the high diameter accuracy is required. The rotating driving power of this motor is transmitted via a reduction gear 40, a clutch 41 and a timing belt 48, etc., (transmission mechanism) to a take-up drum 18. As a result, the semiconductor single crystal may be pulled up with good accuracy in a middle speed range of 0.3 to 3.0mm/min by means of a pulling up wire. In the stage for growing parts exclusive of the fixed diameter part, the rotation of a motor 30 for high-speed rotation is transmitted via a reduction gear 43 and a double clutch 42, etc., to the take-up drum 18.

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 for pulling a semiconductor single crystal from a semiconductor melt stored using a crucible, and more particularly to a seed crystal suspended on an upper shaft (pulling wire). The present invention relates to an upper shaft raising / lowering mechanism (pulling wire winding mechanism) for raising and lowering the shaft.

Conventionally, a CZ (Czochralski) method is known as one of the methods for growing a semiconductor single crystal such as silicon (Si) or gallium arsenide (GaAs). This CZ method is a method used for growing various semiconductor crystals because it has a feature that a large-diameter, high-purity single crystal can be easily obtained without dislocations or with extremely few lattice defects.

The outline of the CZ method is as follows. As shown in FIG. 5, a polycrystalline silicon lump (or granular polycrystalline silicon) is filled in a quartz crucible (not shown) and melted to form a silicon melt 6. And Pull wire (upper shaft) 7
Seed 9 hung via the seed crystal holder 8 at the lower end of the
Is immersed in the silicon melt 6 to start pulling after the seed crystal 9 itself is melted (seeding). The crystal diameter is gradually increased by continuing the pulling, and the process proceeds to the pulling of the constant diameter portion (main body) 5 through the process of forming the neck 2, the cone 3 and the shoulder 4.

[0004] Here, with reference also to Fig. 6, an outline of a lifting mechanism (winding mechanism) of the pulling wire 7 will be described. The upper end of the pulling wire 7 is fixed to the winding drum 18, and the pulling wire 7 can be raised (pulled) or lowered by rotating the winding drum 18 forward or backward. The rotation of the low-speed rotation motor (servo motor) 10 having the speed reducer 11
2 is transmitted to the first pulley 13, while the rotation of the high-speed rotation motor 14 is transmitted to the second pulley 15. First pulley 13 and second pulley 1
5, a timing belt 16 is stretched. The rotation of the first pulley 13 is transmitted to the winding drum 18 via the worm mechanism 17.

[0005] Prior to the growth of the semiconductor single crystal,
When the seed crystal 9 is lowered, the clutch 12 is disengaged, the winding drum 18 is reversely rotated at a high speed by the high-speed rotation motor 14, and the seed crystal 9 is rotated at a high speed (for example, 16.7 to 16.7).
(In the range of 1000 mm / min). When the seed crystal 9 is pulled up, the clutch 12 is connected and the low-speed rotation motor 10 is driven to drive the winding drum 1.
Rotate 8 forward. In the seeding step, the pulling speed is generally set to 0.1 to 6.0 in order to control the diameter of the seed crystal 9.
Adjust in the low speed range of mm / min. On the other hand, in the growth process of the constant diameter portion 5, the pull-up wire 7 is generally set to 0.1 mm in order to make the diameter of the constant diameter portion 5 a predetermined value while feeding back the diameter of the constant diameter portion 5 to the low-speed rotation motor 10. 3 to 3.0 mm /
It is necessary to raise in the range of min.

[0006]

However, in the above-mentioned conventional upper shaft raising / lowering mechanism (pulling wire winding mechanism), when growing a constant diameter portion of a semiconductor single crystal, the pulling wire is 0.3 to 3.0 mm / mm. In spite of the necessity to raise the speed accurately in the speed range of m, this range is greatly deviated from the rating of the motor for low-speed rotation. Lower,
As a result, there is a problem that improvement in quality of the semiconductor single crystal is hindered. This problem has become more prominent with the increase in diameter of the constant diameter portion, which is required to have high diameter accuracy, and it has been strongly desired to solve the problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has been developed to improve the quality of a semiconductor single crystal, particularly when growing a constant diameter portion required to have high diameter accuracy. It is an object of the present invention to provide an upper shaft elevating mechanism for a single crystal pulling apparatus that can be improved.

[0008]

According to the present invention, there is provided a single crystal pulling apparatus in which a seed crystal is suspended in a semiconductor melt stored in a crucible by lowering an upper shaft on which a seed crystal is suspended. An upper shaft elevating mechanism for growing the semiconductor single crystal with the seed crystal as a nucleus above the semiconductor melt by immersing the seed crystal in the semiconductor melt and winding the upper shaft on a winding drum, A constant-diameter portion growth motor that is used when growing a constant-diameter portion of the semiconductor single crystal, and in which a predetermined pulling speed of the upper shaft is within a rated upper and lower allowable range; A transmission mechanism for transmitting the rotating power of the diameter growth motor to the winding drum; and a high-speed rotation used when lowering the upper shaft at a high speed or when growing the semiconductor single crystal other than a constant diameter portion. When the motor and the upper shaft descend A high-speed transmission mechanism for transmitting the rotational power of the high-speed rotation motor to the winding drum, and during the growth of the semiconductor single crystal other than the constant diameter portion, the rotational power of the high-speed rotation motor is reduced. A low-speed transmission mechanism for transmitting this to the winding drum, and a clutch for transmitting rotation of the high-speed rotation motor to the winding drum via one of the high-speed transmission mechanism and the low-speed transmission mechanism. And a mechanism.

[0009] Further, a clutch may be provided for preventing one rotation of the constant diameter portion growth motor and the high speed rotation motor from being transmitted to the other.

According to the first aspect of the present invention, when the seed crystal is lowered prior to the growth of the semiconductor single crystal, the rotation of the high-speed rotation motor is transmitted to the high-speed transmission mechanism by the clutch mechanism, and the high-speed rotation is transmitted. The rotating power of the motor is transmitted to the winding drum via the high-speed transmission mechanism, and the motor is rotated in reverse at high speed.
Thereby, the seed crystal can be dropped at a high speed. When pulling up the seed crystal, the clutch mechanism is switched to transmit the rotation of the high-speed motor to the low-speed transmission mechanism, and the rotational power of the high-speed motor is reduced by the low-speed transmission mechanism and transmitted to the winding drum. Thereby, the winding drum rotates forward at a low speed and the seed crystal can be pulled up at a low speed. Here, in only the constant diameter portion growth step required for high diameter accuracy, the high-speed rotation motor is stopped, and the predetermined pulling speed in the constant diameter portion growth step is within a rated upper and lower allowable range. The rotation power is transmitted to the winding drum via the medium-speed transmission mechanism, and the diameter of the constant-diameter portion is fed back to the constant-diameter portion growth motor, and the pull-up wire 7 is turned off. 3. Pull accurately with a medium speed range of 3 to 3.0 mm / min.

According to the second aspect of the present invention, the rotation of one of the constant diameter portion growth motor and the high-speed rotation motor is not transmitted to the other by disengaging the clutch. No drag rotation occurs.

[0012]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic perspective view of a single crystal pulling apparatus according to the present invention, and FIG. 2 is a schematic view of a first embodiment of an upper shaft elevating mechanism of the present invention in FIG.

First, as shown in FIG. 1, a quartz crucible 21 supported by a graphite susceptor 22 is accommodated in a chamber (airtight container) 20 of a single crystal pulling apparatus. Melt (semiconductor melt)
6 is stored. A substantially cylindrical graphite heater 23 is provided around the quartz crucible 21, and a heat shielding plate 24 is further provided outside the graphite heater 23. The optical system 25 measures the diameter of the liquid surface portion of the silicon melt 6 of the silicon single crystal (semiconductor single crystal) 1 at the time of crystal growth, and controls a pulling speed of a pulling wire 7 described later based on the measured value.

A large-diameter cylindrical body 26 is connected to the upper part of the chamber 20, and an upper shaft elevating mechanism (pull-up wire winding mechanism) 28 described later is provided at the upper end of the large-diameter cylindrical body 26. A small diameter cylinder 27 is connected. The upper shaft elevating mechanism 28 includes a guide drum 2 in a casing 32.
9 and a winding drum 18 are provided.
8 is a constant diameter portion growth motor (servo motor) 31 described later.
And the high-speed rotation motor (servo motor) 30 to drive the lifting wire 7 up or down. A seed crystal 9 is suspended from a lower end of a pulling wire 7 serving as an upper shaft via a seed crystal holder 8. Reference numeral 33 denotes a known rotation mechanism for rotating the entire upper shaft elevating mechanism 28 with the axis of the small-diameter cylinder 27 as a rotation axis.

Next, the structure of the upper shaft elevating mechanism 28 will be described in detail with reference to FIG. The constant diameter portion growth motor 31 is connected to an input side of a clutch 41 via a speed reducer 40, and a pulley 44 is connected to an output side of the clutch 41. Is decelerated by a speed reducer 40 and further transmitted to a pulley 44 via a clutch 41. This pulley 4
A timing belt 48 is stretched between the pulley 4 and another pulley 45, and the rotation of the pulley 45 is transmitted to the winding drum 18 via the worm mechanism 17. In this manner, the winding drum 18 can be rotated by the rotational power of the constant diameter portion growth motor 31, and the constant diameter portion growth motor 31 rotates the constant diameter portion 5 (FIG. 5). Here, the constant diameter portion 5 of the silicon single crystal 1
(See FIG. 5) at a predetermined pulling speed (0.3 to 3.0 mm)
/ Min) is within the range of 10% above and below the rating of the constant diameter portion growth motor 31 (allowable range of rating). A predetermined pulling speed (0.3 to 3.0) of the constant diameter portion 5 (see FIG. 5) is set within a range of 10% above and below the rating of the constant diameter portion growth motor 31.
mm / min), the accuracy of the rotation control of the constant diameter portion growth motor 31 and, consequently, the diameter control of the constant diameter portion 5 is reduced, and as a result, the improvement of the quality of the silicon single crystal 1 is hindered. become. The clutch 41, pulley 44,
The timing belt 48 and the pulley 45 constitute a transmission mechanism for transmitting the rotation of the constant diameter portion growth motor 31 to the winding drum 18.

A pulley 51 is connected to an output shaft of the high-speed rotation motor 30, and an input side of a speed reducer 43 is connected to the pulley 51. The output side of the speed reducer 43 is connected to a pulley 47. On the other hand, a timing belt 52 is stretched between the pulley 51 and one input pulley 42a of a double clutch (clutch mechanism) 42 described later. The other input side pulley 4 of the double clutch 42
A timing belt 49 is stretched between 2 b and the pulley 47 on the output side of the speed reducer 43. The output shaft 46 of the double clutch 42 is connected to the pulley 45. The double clutch (unit) 42 is a publicly known one configured to transmit the rotation of one of the two input pulleys 42a and 42b to the output shaft 46, and is, for example, manufactured by Miki Pulley Co., Ltd. Model 121-10 was used.

One pulley 42a of the double clutch 42
When the (input side of the speed reducer 43) is connected to the output side shaft 46, the rotation of the high-speed rotation motor 30 is controlled by the pulley 5
1. The power is transmitted to the winding drum 18 via the timing belt 52, the double clutch 42, the pulley 45, the worm mechanism 17, and the like, whereby the winding drum 18 can be reversely rotated at high speed. As a result, the seed crystal 9 can be lowered at a high speed. On the other hand, when molding other than the constant diameter portion 5 of the silicon single crystal 1 (shoulder, bottom, etc.), the double clutch 42
By connecting the other pulley 42b (the output side of the speed reducer 43) to the output side shaft 46, the rotation of the high-speed rotation motor 30 is controlled by the pulley 51, the speed reducer 43, the pulley 47, the timing belt 49, and the double clutch 42. Is transmitted to the winding drum 18 via the pulley 45 and the worm mechanism 17 and the like, and the winding drum 18 can be rotated forward at a low speed.

As is apparent from the above description, the pulley 5
1, a timing belt 52, a pulley 45 and the like constitute a high-speed transmission mechanism, and the speed reducer 43, the pulley 47
The timing belt 49, the pulley 45, and the like constitute a low-speed transmission mechanism.

Next, the operation of the single crystal pulling apparatus of the present embodiment, particularly, the operation of the upper shaft elevating mechanism will be mainly described. The basic steps in growing a silicon single crystal by the CZ (Czochralski) method are melting, seeding, and single crystal pulling growth of a polycrystalline silicon raw material.

A polycrystalline silicon lump is filled in a quartz crucible 21 and melted by heating to 1415 ° C. (melting point of silicon) or more in an inert gas (Ar). If granular polycrystalline silicon is used instead of the polycrystalline silicon lump, filling and melting can be performed in a shorter time.

The seed crystal 9 is moved at a high speed (16.7 to 1000 mm).
/ Min) and dipped in the silicon melt 6. In order to perform this operation, the high-speed rotation motor 30 is started while the constant diameter portion growth motor 31 is stopped and the clutch 41 is disconnected, and one input side pulley 42a of the double clutch 42 is connected to the output side. Connected to shaft 46. Thus, the rotation of the high-speed rotation motor 30 is transmitted to the winding drum 18 via the pulley 51, the timing belt 52, the double clutch 42, the pulley 45, the worm mechanism 17, and the like. Reverse rotation. In addition,
At this time, since the clutch 41 is disengaged, the pulley 45
Is not transmitted to the constant diameter portion growth motor 31, and no drag rotation of the rotor of the constant diameter portion growth motor 31 occurs.

As described above, after the seed crystal 9 is immersed in the silicon melt 6, the seed crystal 9 itself is melted and then the pulling is started (seeding). This is the finest step in the CZ crystal growth process. During the entire crystal growth process, an inert gas (A) is used to exhaust SiO and CO generated as reactants in the apparatus to the outside.
r) flows down from above. Necking
g) After that, the crystal diameter is gradually increased, cone 3, shoulder 4
(See FIG. 5), and the process proceeds to raising the constant diameter portion (main body) 5. The crystal growth rate is optimized by controlling the pulling rate and the melt temperature in consideration of the height of the silicon melt 6 surface (that is, the depth of the melt), which decreases with the pulling growth.
As the amount of the remaining melt decreases, the exposed wall surface of the quartz crucible 21 increases and radiant heat increases, so that the temperature of the solid-liquid interface increases. Therefore, in general, it is necessary to reduce the pulling speed in order to obtain a constant diameter as approaching the end of silicon single crystal 1.

Here, regarding the operation at the time of pulling a single crystal,
This will be described in detail with reference to FIG. During seeding (see region A in FIG. 4), seed crystal 9 is slowly moved (generally 0.1 to
In the case of pulling up at a speed of 6.0 mm / min), the other input side pulley 42b of the double clutch 42 is connected to the output side shaft 46 so that the rotation of the high speed rotation motor 30 is reduced by the speed reducer. 43, a pulley 47, a timing belt 49, a double clutch 42, a pulley 45, the worm mechanism 17, and the like.
The winding drum 18 rotates forward at a low speed. The reason why the pulling speed of the seed crystal 9 has a large variation such as 0.1 to 6.0 mm / min is that the pulling speed of the seed crystal 9 depends on the measured value of the optical system 25 in order to make the diameter of the seed crystal 9 a predetermined value. This is to perform feedback control of the high-speed rotation motor 30.

The seed crystal 9 is continuously pulled at a low speed by the high-speed rotation motor 30 even when the neck 2, the cone 3, and the shoulder 4 are grown, that is, at the time of initial pulling (see the area B in FIG. 4). increase.

At the time of growth of the constant diameter portion 5 (see region C in FIG. 4), the high speed rotation motor 30 is stopped, while the constant diameter portion growth motor 31 is activated and the clutch 41 is started.
Insert Thus, the constant diameter portion growing motor 31 having the pulling speed in the constant diameter portion growing step within the allowable range of the upper and lower limits of the rating.
The rotational power of the speed reducer 40, the clutch 41, the pulley 4
4, transmitted to the winding drum 18 via the timing belt 48, the pulley 45, the worm mechanism 17 and the like, so that the pulling wire 7 can be pulled up accurately in a medium speed range of 0.3 to 3.0 mm / min. . As described above, when growing the silicon single crystal 1 with the constant diameter portion growth motor 31 which is required to have particularly high diameter accuracy, the silicon single crystal 1 is pulled up by the dedicated constant diameter portion growth motor 31. The quality of the silicon single crystal 1 can be improved by increasing the accuracy of controlling the diameter of the portion 5.

Finally, when growing the bottom portion of the silicon single crystal 1 (see region D in FIG. 4), the high-speed rotation motor 30
Is used to pull up the pulling wire 7. That is, the motor 31 for growing the constant diameter portion is stopped, and the clutch 4
Cut off one. Further, the high-speed rotation motor 30 is started to pull up the silicon single crystal 1 at a low speed. It should be noted that the pulling wire 7 can be moved up and down at a high speed by manually operating the high-speed rotation motor 30 in the event of any abnormality.

FIG. 3 is a configuration diagram of a second embodiment of the upper shaft elevating mechanism of the single crystal pulling apparatus according to the present invention. The difference from the first embodiment is that a clutch 53 is provided between the output shaft 46 of the double clutch 42 and the pulley 45.
In this example, the clutch 53 is disconnected only during the growth of the constant diameter portion 5 (see the area C in FIG. 4), so that the pulley 45
Is not transmitted to the high-speed rotation motor 30, and the rotation of the rotor of the high-speed rotation motor 31 does not occur.

[0028]

Since the present invention is configured as described above, it has the following effects. The invention according to claim 1 is a dedicated motor for growing a constant diameter portion having a pulling speed within an upper and lower allowable range of a rating when growing a constant diameter portion of a semiconductor single crystal which requires particularly high diameter accuracy. Thus, the precision of controlling the diameter of the constant diameter portion can be increased, and the quality of the semiconductor single crystal can be improved. According to the second aspect of the present invention, in addition to the above-described effects, one rotation of the constant diameter portion growth motor and the high-speed rotation motor is not transmitted to the other, so that the drag rotation of the rotor of the other motor by one motor occurs. Absent. As a result, unnecessary load is not applied to both motors, and the life is extended.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a single crystal pulling apparatus according to the present invention.

FIG. 2 is a schematic view of a first embodiment of an upper shaft elevating mechanism (pulling wire winding mechanism) of the present invention.

FIG. 3 is a schematic view of a second embodiment of the upper shaft elevating mechanism of the present invention.

FIG. 4 is a graph showing a relationship between a time and a pulling speed at the time of pulling a single crystal.

FIG. 5 is an enlarged view of an upper portion of the silicon single crystal shown in FIG.

FIG. 6 is a schematic view of a conventional upper shaft elevating mechanism.

[Explanation of symbols]

 Reference Signs List 1 silicon single crystal (semiconductor single crystal) 2 neck 3 cone 4 shoulder 5 constant diameter part (main body) 6 silicon melt (semiconductor melt) 7 pulling wire (upper shaft) 8 seed crystal holder (chuck) 9 seed crystal 17 Worm mechanism 18 Winding drum 20 Chamber 21 Quartz crucible 22 Graphite susceptor 23 Graphite heater 24 Heat shield plate 25 Optical system 26 Large diameter cylinder 27 Small diameter cylinder 28 Upper shaft elevating mechanism (pulling wire winding mechanism) 29 Guide drum 30 High speed rotation Motor (servo motor) 31 constant diameter portion growth motor (servo motor) 32 casing 33 rotating mechanism 40, 43 reducer 41, 53 clutch 42 double clutch 42a, 42b input pulley 44, 45, 47, 51 pulley 46 output Side shaft 48, 49, 52 Timing belt

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akira Higuchi 985 Ino, Ginya, Ikuno-cho, Asago-gun, Hyogo Pref.

Claims (2)

[Claims] 1. A seed crystal is immersed in the semiconductor melt by lowering an upper shaft on which a seed crystal is suspended in a semiconductor melt stored in a crucible of a single crystal pulling apparatus. In an upper shaft elevating mechanism for growing a semiconductor single crystal with the seed crystal as a nucleus above the semiconductor melt by winding the same on a winding drum, the semiconductor single crystal is used when growing a constant diameter portion of the semiconductor single crystal. ,
And a predetermined pulling speed of the upper shaft at this time is within a rated upper and lower allowable range, and a motor for growing a constant diameter portion, and a rotational power of the motor for growing the constant diameter portion is transmitted to the winding drum. A transmission mechanism for; a high-speed rotation motor used when lowering the upper shaft at high speed or when growing the semiconductor single crystal other than a constant diameter portion; and a high-speed rotation motor when lowering the upper shaft. A high-speed transmission mechanism for transmitting the rotation power of the semiconductor single crystal to the winding drum; and, during the growth of the semiconductor single crystal other than the constant diameter portion, the rotation power of the high-speed rotation motor is reduced so as to reduce the rotation power to the winding drum. And a clutch mechanism for transmitting rotation of the high-speed rotation motor to the winding drum via one of the high-speed transmission mechanism and the low-speed transmission mechanism. To Upper shaft lifting mechanism for a crystal pulling device according to symptoms. 2. The single-shaft lifting apparatus according to claim 1, further comprising a clutch for preventing one rotation of the constant diameter portion growth motor and the high-speed rotation motor from being transmitted to the other. mechanism.