JP3521070B2 - Fibrous crystal production equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high-quality, low-defect, for example, silicon, lithium niobate (LN),
The present invention relates to an apparatus for producing fibrous materials such as lithium tantalate (LT), yttrium-aluminum garnet (YAG), sapphire, and eutectic. More specifically,
An apparatus for producing fibrous crystals as a functional material used in the field of electronics or optoelectronics, or a structural material used in a high temperature environment, which was difficult to manufacture by the FZ method, Bridgman method, CZ method, or the like. Regarding

[0002]

2. Description of the Related Art Whiskers are known as fibrous single crystals, which are used as reinforcing materials for various composite materials due to their excellent mechanical strength. Various methods for manufacturing whiskers have been studied, but at the commercial level, only the reinforcing material having a diameter of several tens of μm and a length of several tens of mm, that is, a whisker for structural use is provided.

As a method for producing a single crystal material, the CZ method for obtaining a silicon single crystal, an LN single crystal or the like is known. The CZ method provides a bulk crystal having good crystallinity in response to the recent increase in the size of the substrate in the semiconductor manufacturing process. However, when viewed as a method for producing a fibrous single crystal, the radius and depth of the crucible that holds the melted crystalline material (hereinafter referred to as the molten material), the temperature gradient conditions in the furnace, and the conditions suitable for these It is difficult to optimize the pulling speed at the same time.

In view of the above situation, a length of 100 mm and a diameter of 50 which can be used not only for structural materials but also for functional materials.
~ As a method for producing a fibrous single crystal of several 100 μm,
A method for producing a fibrous single crystal has been proposed by forming pores in the lower part of a crucible that holds a molten material, and sequentially crystallizing a minute amount of the molten material that leaks from the pores due to gravity. ing.

FIG. 6 shows a schematic view of an apparatus used for the above manufacturing. The crucible 10 is held vertically, and a seed crystal 3 (hereinafter referred to as a seed) is brought into contact with the molten material 10 leaking from the pores 11 below the crucible 10. Fibrous crystals 2 are produced by pulling down the seed 3 while rotating it in accordance with the crystallization of the molten material 10. Further, by optimizing the pulling speed and the temperature gradient from the crucible 10 to the crystal part, the fibrous crystal is made into a single crystal.

[0006]

In the case of manufacturing a bulk material like the CZ method, the seed is rotated because the latent heat per unit length of the bulk material is large and the crystal growth rate in the pulling direction is slow. The flatness of the crystal growth portion, that is, the solid-liquid interface can be easily maintained only by performing the above.

On the other hand, even in the case of producing a fibrous crystal having a very small latent heat per unit length, the vicinity of the crystal growth portion should be kept for a long time under the condition of a very gentle temperature gradient. For example, the flatness of the solid-liquid interface can be maintained. However, depending on the viscosity of the molten material, there is a problem that the melted part is cut by its own weight or the diameter of the crystal increases due to so-called liquid dripping, so it is actually necessary to make the temperature gradient in the crystal growth part too gentle. Not at all.

Therefore, it is necessary to select a condition that provides an appropriate temperature gradient according to the viscosity of the molten material, increase the pulling rate, and maintain a certain crystal growth rate. However, it is often difficult to maintain the flatness of the solid-liquid interface, so that the crystal orientation is different in the pulling direction, bending, distortion, or defects are likely to occur. In some cases, a crystal having the required characteristics could not be obtained, such as the crystal breaking during pulling.

In view of the above problems, it is an object of the present invention to provide an apparatus for producing a fibrous crystal having a sufficient length with few defects, which prevents bending and distortion of the fibrous crystal during crystal growth. To do.

[0010]

In order to solve the above-mentioned problems, the crystal material held in a container is melted and the melted crystal material is pulled down from the pores provided in the container through a seed crystal. A fibrous crystal manufacturing apparatus according to the present invention for generating a fibrous crystal by the above, a seed holder that holds a seed crystal by a gripping means that is coupled to the tip, and a seed shaft that connects the upper portion to the seed holder. A device comprising an adjusting system connected to the seed shaft to move the seed shaft on a plane perpendicular to the lowering direction, and a drive mechanism for lowering the seed shaft and the adjusting system in a substantially vertical direction. It is characterized by comprising a rotating device for rotating the seed shaft with the direction as the central axis and an angle adjusting means for adjusting the angle of the pulling-down direction with respect to the vertical direction.

Further, in the apparatus for producing fibrous crystals according to the present invention, the drive mechanism includes a motor as a drive source, a speed reducer for reducing the rotation of the motor, and the rotation of the reduced motor to linear motion. And a converter for pulling down the seed axis.

Further, in the fibrous crystal manufacturing apparatus according to the present invention, the gripping means is coupled to the seed holding tool via a coupling tool capable of directing the seed holding tool in an arbitrary direction,
The angle adjusting means has at least one goniometer adjusting mechanism.

Further, in the fibrous crystal production apparatus according to the present invention, the container, the holding means, the seed holder, the seed shaft,
The fibrous crystals are characterized by being held in a vacuum container into which an arbitrary gas can be introduced. Further, the gripping means is preferably a collet chuck.

Further, it is preferable that the fibrous crystal manufacturing apparatus according to the present invention has a deviation detecting means for detecting a deviation of the fibrous crystal with respect to the pulling-down direction. Further, it is more preferable to provide a drive circuit for driving the angle adjusting means based on the detection result of the deviation detecting means.

[0015]

EXAMPLE FIG. 1 shows a schematic configuration of a fibrous crystal production apparatus according to the present invention. This apparatus includes a seed holder 41 and a seed shaft 40 that directly move the seed 3, a drive mechanism 100 that vertically moves these, and a drive direction adjustment system 30,
A heating system 50 and a temperature measuring system 60 for bringing the molten material 1 in the crucible 10 to a predetermined temperature, a decompression container 72 that houses the crucible 10, the seed holder 41, and the like, and an atmosphere control in the decompression container 72 as necessary. The main components are a vacuum exhaust system 70 and a gas introduction system 76 capable of performing the above, and a monitor device 80 for monitoring the growth state of crystals.

Next, each of the above components will be described. FIG. 2 schematically shows a drive mechanism (pull-down mechanism) 100 for moving the seed holder in the vertical direction.
The medium speed servo motor 101 is via the speed reducer 104 and the clutch 107, the low speed servo motor 102 is via the speed reducer 105, and the high speed servo motor 103 is via the speed reducer 106 and the clutch 108.
Transmits rotation to 0.

The vertical movement of the pull-down stage 16 is performed by further transmitting the rotation transmitted to the gear system 110 to the ball screw shaft 14 by a converter including the gear system 110 and the ball screw shaft 14. By selecting an appropriate one from the combination of the servo motor and the speed reducer, it is possible to obtain the pulling down speed of the stage 16 according to the growth speed of the fibrous crystal.

Specifically, in the case of producing a fibrous single crystal, the pulling rate is 0.1 to 1.0 mm / m.
The range is preferably in, and in the case of producing a fibrous eutectic, it is preferably in the range of 1.0 to 30 mm / min. With the above configuration,
In the case of producing any fibrous crystal, it is possible to make the fluctuation of the speed with respect to the set speed ± 1.0% or less.

In this embodiment, the high speed servomotor 103 and the accompanying speed reducer 106 are used, for example, in seed replacement work other than the actual pulling down process. However, the combination of the servomotor and the speed reducer is not limited to the above-described combination and speed range, and it is desirable to use a suitable servomotor and a speed reducer having an appropriate speed reduction ratio according to the manufacturing conditions of the fibrous crystal and the like. .

Generally, the rotation speed of the servo motor is feedback-controlled by detecting the rotation angle, but uneven rotation speed during deceleration, lost motion due to backlash of the reducer, and uneven rotation of the servo motor itself are not caused. I can't adjust. In the present embodiment, the vertical movement amount of the seed holder 41 is directly detected and measured by the linear scale 115 mounted in parallel with the seed shaft 40, and the movement amount is fed back to the rotation of the servo motor to lower the movement amount. We are trying to stabilize the speed.

Further, the diameter of the fibrous crystal 2 is measured at predetermined time intervals by monitoring the state of crystal growth,
The pulling-down speed may be changed at any time to keep the diameter within a predetermined range. Although the pulling-down mechanism 100 secures the straightness in the vertical direction by the high-rigidity linear guide 113, at the same time, in order to flatten the solid-liquid interface of the crystal growth portion, the seed holder and the seed shaft are used. 6 to 60 rp
It is also possible to perform the pulling down step while rotating at m.

The stage 116 shown in FIG. 2 is further provided with a drive direction adjusting system 30. A schematic configuration of the adjustment system 30 is shown in FIG. The servo motor 35, which is a rotating device that rotates the seed shaft 40, has an X table 31 and a Y table 32 that perform position adjustment in the X axis and Y axis directions.
It is installed above and the center of rotation of the servo motor 35 is X.
Adjustment is possible within a range of ± 20 mm with respect to the center of each of the Y tables 31 and 32.

The seed holder 41 is attached to the tip of the seed shaft 40. However, when the seed 3 is actually attached to the seed holder 41, the rotation of the seed shaft 41 and the seed center should be considered in consideration of the rotation of the seed shaft 41. It is necessary that the center of rotation of the seed 3 attached to the tip end is aligned. In this embodiment, a self-centering collet chuck 43 is installed at the tip of the seed holder 41 as a gripping means to facilitate and simplify the centering work and seed exchange.

However, when the solid-liquid boundary surface is not flat and tilts in the crystal growth direction during rotation of the seed shaft 40, the seed shaft 40 can be adjusted only by the XY tables 31 and 32. The center of rotation of is displaced from the pores in the lower part of the crucible (eccentricity). When the crystal growth direction is tilted, the position shift can be prevented by tilting the pull-down direction with respect to the vertical direction.

Therefore, in the present embodiment, by further installing the goniometer X table 33 and the goniometer Y table 34 on the XY tables 31 and 32 as the angle adjusting means, near the pores in the lower part of the crucible, that is, the solid-liquid boundary. It is possible to adjust the angle in the pulling direction with the surface as the center. Further, the collet chuck 43 is coupled to the seed holder 41 via a ball joint 44 as a coupler that can be oriented in any direction, so that the addition of fibrous crystals by the angle adjustment operation is relaxed.

Specifically, the gonio XY tables 33, 3
An angle adjustment of ± 3 ° with respect to the vertical direction is made possible by a micrometer head (not shown). During the crystal growth, the deviation of the fibrous crystal with respect to the pull-down direction is detected by the shift detecting means, and the pull-down direction is adjusted by the adjusting mechanism described above. As the deviation detecting means, it is preferable that the deviation detecting means is configured to read a grown portion of a crystal as an image by a CCD or the like, convert the read image into a signal, and perform arithmetic processing using the signal to detect the deviation state.

This makes it possible to prevent bending and distortion of the fibrous crystal during manufacture and to obtain a fibrous crystal of a predetermined length. In addition, it is desirable that the above-mentioned adjustment be performed at any time according to the crystal growth state by monitoring the growth state of the crystal 2 near the solid-liquid interface. Further, it is more preferable to provide a drive circuit that automatically drives the adjustment mechanism based on the monitoring result.

Depending on the molten material used for production, oxidation,
In order to prevent reduction or the like, it may be desirable to reduce the pressure in an inert gas atmosphere or in a vacuum, or it may be desirable to perform atmosphere control using an oxidizing gas, a reducing gas or the like. In the present embodiment, the crucible 10,
Molten material 1, fibrous crystal 2, seed 3, seed holder 4
1, and the seed shaft 40 are arranged in a decompression container 72 capable of introducing gas, and atmosphere control is possible.

Specifically, the decompression container 72 comprises a transparent quartz chamber 73 and a metal bellows 74. The crucible 10, the molten material 1, the crystal growth portion and the vicinity thereof are held in the transparent quartz chamber 73 in order to monitor the crystal growth state from the outside. The seed holder 41 and the seed shaft 40 in the transparent quartz chamber 73 in the initial stage of the production of the fibrous crystal are pulled down as the fibrous crystal 2 grows, and the transparent quartz chamber 7
It is housed inside a telescopic bellows 74 connected to 3.

The decompression container 72 is a transparent quartz chamber 73.
Is evacuated by a vacuum exhaust system 70 connected to a connecting portion between the metal bellows 74 and the metal bellows 74, thereby enabling crystal growth at a predetermined vacuum degree. Further, an arbitrary gas can be introduced into the decompression container 72 by a gas introduction system 76 connected to the connecting portion. In this case, the decompression container 72
The internal pressure is preferably adjusted by adjusting the exhaust speed of the vacuum exhaust system 70 using a conductance valve or the like and adjusting the amount of gas introduced from the gas introducing system 76 using a flow rate controller.

It is desirable that the ultimate vacuum when the vacuum vessel 72 is evacuated is 10 ^-2 Torr or less in order to prevent contamination of the fibrous crystals to be manufactured. Further, when the atmosphere control is required for producing the fibrous crystal, it is desirable to change the gas introduction position such as near the crystal growth portion or near the lower portion of the seed shaft 40 according to the manufacturing conditions.

In the heating system 50 used for melting the crystalline material in the present embodiment, two types of platinum-based metal heating elements having different heating effective lengths for indirect heating are arranged around the crucible 10 and they are energized. This enables heating up to 1500 ° C. In this case, a thermocouple is used for the temperature measuring system 60, and the temperature is controlled by PID control based on the temperature in the vicinity of the crucible obtained by the direct measurement by the thermocouple.

Further, a high frequency coil is used as the heating system 50 used for the direct heating, and this is installed on the outer circumference of the transparent quartz chamber 73, and the high frequency coil is used to generate 240
Allows heating up to 0 ° C. In this case, a digital infrared two-color thermometer is used as the temperature measuring meter 60, and the temperature of the molten material is directly measured by this to control the temperature.

[0034]

EFFECTS OF THE INVENTION The apparatus according to the present invention provides a fibrous crystal having few defects and having a sufficient length, which prevents bending and distortion of the crystal at the time of growing the crystal when producing the fibrous crystal. It becomes possible to do.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a fibrous crystal production apparatus according to the present invention.

FIG. 2 is a diagram showing a configuration of a drive mechanism in FIG.

FIG. 3 is a diagram showing a configuration of a drive direction adjustment system in FIG.

FIG. 4 is a diagram showing heating by the indirect heating method in FIG. 1, measurement, and an outline of a part of the decompression container in this case.

5 is a diagram showing heating by the direct heating method in FIG. 1, measurement, and an outline of part of the decompression container in this case.

FIG. 6 is a diagram showing an outline of a method for producing a fibrous crystal in the prior art.

[Explanation of symbols]

1: Molten material 2: Fibrous crystals 3: Seed crystal 10: crucible 11: Pore 30: Drive direction adjustment system 31: X table 32: Y table 33: Gonio X table 34: Gonio Y table 35: Servo motor 40: Seed axis 41: Seed holder 43: Collet chuck 50: Heating system 60: Temperature measurement system 70: Exhaust system 72: Decompression container 73: Transparent quartz chamber 74: Metal bellows 76: Gas introduction system 100: Drive mechanism 101, 102, 103: Servo motor 104, 105, 106: reducer 107, 108: Clutch 110: Gear system 113: Linear motion guide 114: Ball screw shaft 115: Linear scale 116: Stage

─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP-A-8-231299 (JP, A) JP-A-51-111478 (JP, A) JP-A-8-143399 (JP, A) JP-A-64- 42400 (JP, A) JP-A-11-278994 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C30B 1/00-35/00 H01L 21/208

Claims (7)

(57) [Claims] 1. Melting a crystalline material held in a container,
In a fibrous crystal manufacturing apparatus for producing a fibrous crystal from the crystalline material by pulling down the crystalline material melted from the pores provided in the container through a seed crystal, a grip connected to the tip Means for adjusting the seed crystal, a seed holder for holding the seed crystal, a seed axis for connecting the upper portion to the seed holder, and an adjustment for connecting the seed axis so that the seed axis can move on a plane perpendicular to the pull-down direction. System, a drive mechanism for pulling down the seed axis and the adjusting system in a substantially vertical direction, and a solid-liquid boundary in which the crystalline material changes into the fibrous crystal.
Detection for monitoring the growth state of the crystal near the interface
And a rotation device that rotates the seed shaft with the pull-down direction as a central axis, and an angle adjusting unit that adjusts an angle of the pull-down direction with respect to a vertical direction. have a, the adjustment system and said angle adjusting means, said detecting means
That the solid-liquid interface was not flat and tilted.
A fibrous crystal manufacturing apparatus, which is driven according to the inclination when detected . 2. The drive mechanism includes a motor as a drive source, a speed reducer for reducing the rotation of the motor, and a converter for converting the reduced rotation of the motor into a linear motion to lower the seed shaft. The device of claim 1, which comprises: 3. The gripping means is coupled to the seed holder via a coupling tool that can be oriented in any direction with respect to the seed holder, and the angle adjusting means includes at least one goniometer adjusting mechanism. The apparatus of claim 1, comprising. 4. The apparatus according to claim 3, wherein the container, the gripping means, the seed holder, the seed shaft, and the fibrous crystal are held in a vacuum container into which an arbitrary gas can be introduced. . 5. The apparatus according to claim 3, wherein the gripping means is a collet chuck. 6. The apparatus according to claim 3, wherein the apparatus further comprises a deviation detecting means for detecting a deviation of the fibrous crystal with respect to the pulling down direction. 7. The apparatus according to claim 6, further comprising a drive circuit for driving the angle adjusting means based on a detection result of the deviation detecting means.