JPS62171987A - Cz single crystal production apparatus and production method - Google Patents

Abstract

PURPOSE:To eliminate noise generation in output signal from a load cell and to prevent precession of grown single crystal, by inserting an elastomer between a force bar and a guide shaft, thereby shifting characteristic frequency of simple harmonic oscillation from rotational frequency of growing single crystal. CONSTITUTION:In an apparatus for producing a single crystal by Czochralski method, an elastomer holder 11 is attached near the lower end of a guide shaft 5 of a force bar 1 and is linked to the lower end of the guide shaft 5 with a spring 13 via a spacer 25. The characteristic frequency of simple harmonic oscillation of a pendulum having a length equal to the distance between the detection end 15 of a load cell 4 and the center of gravity of the grown crystal is made higher than the rotational frequency of the crystal by this process. The process is effective in eliminating the noise generation in the output signal of the load cell 4 caused by the contact of the guide shaft 5 with the force bar 1 and carrying out accurate control of the diameter by weight.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement of a gravimetric diameter control device for growing single crystals in the Czochralski method (hereinafter referred to as CZ method).
In particular, the present invention relates to a support device and method for a so-called force bar, which is a transmission section to a load cell that suspends a single crystal and measures tensile force.

[Prior Art] Gravimetric control is one of the diameter control methods for CZ single crystals.

This measures the weight of the growing crystal and compares it with the model crystal weight, and changes the temperature in the crystal growth furnace and crystal pulling speed depending on the size of the deviation, and approximates the crystal diameter to the diameter of the model crystal. It is controlled as follows.

In order to measure the weight of the growing crystal in this method,
A load cell fixed to the carriage that pulls the growing single crystal is used, and a rod-shaped rigid body is installed between the detection end of the load cell and the seed chuck that holds the seed crystal, and transmits the tensile force due to the weight of the crystal to the load cell. is generally called a force bar.

Usually, crystals grow while rotating, and in order to provide this rotational motion, the load cell, seed chuck, and force bar must all be rotated on the same rotation axis.

In addition, in order for the force bar to accurately transmit the weight of the grown crystal to the load cell, it must not come into contact with other fixed parts and cause friction while suspended from the load cell detection end.

In such a mechanism, when the crystal is rotated, the pendulum length is the natural harmonic motion with the load cell detection end as the fulcrum and the length of the pendulum determined by the force bar, the seed chuck, and the center of gravity determined by the weight of the growing crystal. When the frequency approaches the crystal rotational speed, a resonance phenomenon occurs, and the growing crystal begins to precess with a large amplitude in synchronization with the rotation. the result,
Harmful dislocations may occur or the crystal may bend during growth.

However, in a normal CZ method single crystal growth furnace, M=
2 (m), f=21.1 (min-'), which falls within the crystal rotational speed range of 15 to 30 rpIll.

Conventionally, in order to prevent such precession due to resonance, a ring with an inner diameter slightly larger than the diameter of the force bar, called a collar 3, was installed near the joint between the force bar 1 and the seed chuck 2, as shown in Fig. 7. The guide shaft 5 rotates on the same axis as the force bar and the load cell 4.
The amplitude of the force bar was regulated mechanically.

However, with this method, the collar and force bar come into contact during resonance, which causes instability in weight measurement due to friction for the reason mentioned above, which appears as noise in the load cell output, which may make diameter control even more inaccurate. There is.

In addition, since the joint between the collar and the guide shaft is easily exposed to relatively high temperatures, the material of the collar must normally be graphite, but when the force bar and the collar come into contact, part of the collar is destroyed and the raw material melt It may also fall into the crystal and adhere to the growing crystal growth interface, interfering with single crystallization.

Force bars may also become deformed due to long-term use at high temperatures. In this case, even if a slight clearance is maintained so as not to contact the collar at the time of initial adjustment, contact will eventually occur all the time even at times other than resonance. The results are also similar to those described above.

[Problems to be Solved by the Invention] As described above, the above-mentioned collar provided to prevent vibration of the single crystal has a disadvantage in weight control due to the additional problem of contact with the force bar. brings stability. Furthermore, if contact occurs and the collar is damaged, the broken material that falls at this time will adhere to the crystal growth interface and inhibit single crystallization. Naturally, this inevitably leads to a decrease in yield and production efficiency.

In addition, the conventional phenomenon of crystal mass reduction and generation of dislocations due to the precession of the growing single crystal during pulling also leads to lower yields and production efficiency.

[Means for Solving the Problems] The present invention has been made to solve the following problems. In a gravimetric diameter control device for m-crystals in a single-crystal manufacturing device using the Czochralski method, the force bar and guide shirt i are made elastic so that the force bar has a small rigidity in the axial direction and a large rigidity in the perpendicular direction. It is characterized in that the natural frequency of simple harmonic vibration, where the pendulum length is from the load cell detection end to the center of gravity of the growing crystal, is different from the crystal rotation speed used for normal CZ method single crystal growth. do.

Moreover, a spring, a thin plate, rubber, etc. can be used as the elastic body. The force bar and the guide shaft may be directly connected with an elastic body, but once an elastic body holder is fixed to either the force bar or the guide shaft, the connection between the elastic body holder and the force bar, or between the elastic body holder There is also a method of connecting the guide shaft with an elastic body.

Further, one end of the guide shaft is normally attached to the lower surface of the load cell, but in the practice of the present invention, it may be attached to the lower surface of the rotation transmission gear for rotating the grown single crystal.

[Function] The present invention reduces the rigidity of the elastic body in the axial direction of the force bar by using the connection form of the elastic body between the force bar and the guide shaft and the shape of the elastic body, thereby reducing the weight of the load cell. By increasing the rigidity in the perpendicular direction without affecting detection, the restoring force proportional to the displacement of the force bar in the perpendicular direction is increased compared to the case of gravity alone. Furthermore, by the action of an elastic body having a desired spring constant, with the load cell detection end as a fulcrum,
The pendulum length is the length from there to the center of gravity determined by the weight of the force bar, seed chuck, and growing crystal, and the natural frequency of simple harmonic vibration is made different from the rotational speed of the growing single crystal.

That is, for example, when a spring is used as the elastic body, the displacement amount in the full span of the load cell is usually 20 μm.
Since the following is considered, if a spring constant of 2000 ON/m and a length of 30 mm is used, the tensile force in the axial direction due to the spring will be 0.4 N.

This is 0.1 assuming the full span weight is 50 kg.
% or less, and does not affect diameter control accuracy within a practical range.

In this way, the present invention prevents the weight detection of the load cell from being affected by the effect of the spring constant of the elastic body and the shape of its attachment, and also prevents the precession of the growing single crystal. be.

[Embodiment 1] FIG. 1 is an enlarged partial cross-sectional view of an elastic body retainer portion showing an embodiment of the present invention.

FIG. 2 is a longitudinal cross-sectional view of essential parts showing an embodiment of the present invention.

Further, FIG. 3 shows a plan view of the elastic body retainer portion in this embodiment.

FIG. 6 shows a conventional CZ method single crystal production apparatus, and FIG. 7 shows a longitudinal sectional view of a conventional CZ method force bar support device.

In one embodiment shown in FIGS. 1 and 2, a load cell 4 is placed on a carriage 7 that pulls up a growing single crystal 6 (see FIG. 6), and a force bar 1 is inserted through the carriage. The guide shaft 5 extends into the crystal growth furnace 8 (see FIG. 6).

A seed chuck 2 is attached to the tip of the forceper 1, which grasps the seed 9 and pulls up the crystal. A bearing 10 is provided between the guide shaft 5 and the carriage 7. The entire apparatus, including the load cell 4, is located within the growth reactor.

The two ends of the guide shaft 5 are fixed to the lower surface of the load cell, and the lower end reaches halfway along the force par length. An elastic body holder 11 is attached to a position near the lower end of the guide shaft of the forceper 1, and the elastic body holder and the lower end of the guide shaft 5 are connected by a spring 13 via a spring spacer 25.

The load cell 4 is attached to the rotation transmission gear 14,
The growing single crystal 6 (see FIG. 6) is rotated.

The guide shaft 5 and the force par 1 therefore rotate in the same manner. The rotation speed is 15-30 rpm.

Assuming that the length of the pulled single crystal is 700 mm, the weight M is 25 kg, and the center of gravity is at point 172 of the crystal length, the pendulum length Ω when the grown single crystal from the load cell detection end 14 is the pendulum.
is 2m. Further, the length χ from the load cell detection end 15 to the position where the spring is attached is 2 to 3 m, and therefore the ratio a to Ω is Q/χ·3.

The overall spring constant of the three springs is 3000ON/m.
It is. Therefore, from the natural vibration of the simple harmonic motion with the grown single crystal as a pendulum due to the provision of a spring, f'=
112 (min-').

The crystal rotation speed is 15 to 30 rpm as described above.

When the material was pulled up in this manner, no precession caused by rotation and no noise in the load cell output occurred. Furthermore, since no collar or the like was used, single crystallization was easily achieved without contamination of foreign matter into the melt.

In this example, the mechanism shown in FIGS. 1 and 2 was used, but similar results were obtained with the mechanism shown in FIG. 4.

[Embodiment 2] FIG. 5 is a plan view of an elastic body retainer portion showing an embodiment of the present invention.

A thin plate 17 having a slit 16 is provided between the guide shaft 5 and the inner wall 12 of the elastic body retainer.

It has a structure in which the spring in Example 1 is replaced with a thin plate.

The spring constant is 3000 ON/m as in Example 1.

When a pulling experiment similar to that in Example 1 was conducted, no precession due to rotation and no noise in the load cell output occurred. Furthermore, since no collar or the like was used, single crystallization was easily achieved without contamination of foreign matter into the melt.

[Effects of the Invention] According to the present invention, since there is no collar between the guide shaft and the force bar, there is no problem in which damaged parts of the collar adhere to the single crystal growth interface due to vibrational contact of the force bar.

Furthermore, the generation of noise in the load cell output due to contact is eliminated, and weight-based diameter control can be performed accurately.

As can be seen from the above examples, if the conventional method is used, the natural frequency of the simple harmonic vibration with the grown single crystal as a pendulum falls within the range of the crystal rotation frequency obtained by the normal CZ method. Differential motion occurs, causing the crystal to grow in a crooked manner and cause dislocations to occur, but according to the present invention, the natural frequency does not fall within this range, so the above-mentioned problems are completely eliminated.

As a result, the present invention improves the product yield rate in CZ method single crystal production and improves work efficiency.

[Brief explanation of drawings]

FIG. 1 is an enlarged partial cross-sectional view of an elastic retainer portion showing an embodiment of the present invention. FIG. 2 is a vertical cross-sectional view of a main part showing an embodiment of the present invention. 3 to 5 are cross-sectional views of an elastic retainer portion showing an embodiment of the present invention. FIG. 6 is a longitudinal cross-sectional view of a part of the CZ method single crystal manufacturing apparatus. FIG. 7 is a longitudinal cross-sectional view of a conventional CZ method force bar support device. 1...Force bar 2...Seed chuck 3...Collar 4...Load cell 5...Guide shaft 6...Growing single crystal 7... ... Gear ridge 8 ... Crystal growth furnace interior 9 ... Seed 10 ... Bearing 11 ... Elastic body retainer 12 ... Spring support rod] 3. ... Spring 14 ... Rotation transmission gear 15 ... Load cell detection end 16 ... Slit 17 ... Thin plate 18 ... Quartz crucible 19 ...・Graphite heater 20 ・Graphite heat shield 2 parts ・Two-part spring mount 22 ・・・・・
Lower spring mount 23...Reflector 24...Windshield 25...Spacer Patent applicant Komatsu Electronic Metals Co., Ltd. Figure 2 Figure 5 Figure 6-zy2

Claims (1)

[Scope of Claims] 1. In a single crystal gravimetric diameter control device for a single crystal manufacturing apparatus using the Czochralski method, the force bar has a small rigidity in the axial direction and a large rigidity in the perpendicular direction. A diameter control device characterized by connecting guide shafts with an elastic body. 2. The guide shaft has one end fixed to the lower surface of the load cell body or the lower surface of the carriage, and the other end reaches the middle length or lower end length of the force bar.
Diameter control device as described in section. 3. The diameter control device according to claim 1 or 2, wherein an elastic body retainer is fixed to the guide shaft, and the elastic body retainer and the force bar are connected by an elastic body. 4. The diameter control device according to claim 1 or 2, wherein an elastic body holder is fixed to the force bar, and the elastic body holder and the guide shaft are connected by an elastic body. 5. The diameter control device according to any one of claims 1 to 4, wherein the guide shaft is a tubular body centered on the force bar, or a rod-shaped or plate-shaped body along the force bar. 6. The elastic body has the function of making the natural frequency of a simple harmonic motion with a pendulum length from the load cell detection end to the center of gravity of the growing crystal different from the crystal rotation speed. The diameter control device according to item 1. 7. The elastic body has the function of increasing the natural frequency of a simple harmonic motion whose pendulum length is from the detection end of the load cell to the center of gravity of the growing crystal, higher than the rotational speed of the crystal. Diameter control device according to paragraph 1. 8. The diameter control device according to any one of claims 1 to 7, wherein the elastic body is a spring. 9. The diameter control device according to any one of claims 1 to 7, wherein the elastic body is a thin plate. 10. In the single crystal gravimetric diameter control method of single crystal manufacturing equipment using the Czochralski method, the natural frequency of simple harmonic vibration, whose pendulum length is from the load cell detection end to the center of gravity of the growing crystal, is made to be different from the crystal rotation speed. Characteristic diameter control method. 11. Claim 10: By providing an elastic body between the force bar and the guide shaft, the natural frequency of a simple harmonic motion whose pendulum length is from the load cell detection end to the center of gravity of the growing crystal is made different from the crystal rotation speed. Diameter control method described. 12. The diameter control method according to claim 10, wherein the elastic body makes the natural frequency of a simple harmonic motion whose pendulum length is from the detection end of the load cell to the center of gravity of the growing crystal higher than the rotational speed of the crystal.