JP2015160786A - Method for manufacturing oxide single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an oxide single crystal, capable of preventing a grown single crystal from dropping when the single crystal is separated from a raw material melt.SOLUTION: The method for manufacturing an oxide single crystal grown by a crystal pulling method of contacting a seed crystal attached at the tip of a pulling shaft with a raw material melt in a crucible to be pulled while rotating the pulling shaft comprises the steps of: growing a straight body part 6b; growing a tail part 6c having a crystal diameter gradually reduced; and separating the grown oxide single crystal from the raw material melt. When a crystal diameter D2 at the tip of the tail part is φ10-20 mm, and a distance L from the end of the straight body part to the tip of the tail part is 0.2- 0.5 times (L/D1=0.2-0.5) to the crystal diameter D1 of the straight body part, the rotation and pulling operation of the pulling shaft are stopped, and the grown oxide single crystal is separated from the raw material melt by descending the crucible.

Description

The present invention relates to a method for growing an oxide single crystal such as TSAG (Tb ₃ Sc ₂ Al ₃ O ₁₂ ) exhibiting hard and brittleness by a crystal pulling method, and in particular, an oxide single crystal efficiently from a small-sized seed crystal. The present invention relates to a method for producing an oxide single crystal capable of producing

  As a method for producing a single crystal, a crystal pulling method called the Czochralski method is widely known. In this method, as shown in FIG. 2, the crucible 1 charged with the raw material is heated by a heating means such as a coil 10 to melt the raw material, and the seed crystal 5 fixed to the tip of the pulling shaft 3 with a pin 4 is provided. The single crystal 6 is grown by bringing it into contact with the surface of the raw material melt 2 and gradually pulling up the seed crystal 5 while rotating it. Single crystal growth by this method is usually performed by a seeding (contacting the seed crystal with the surface of the raw material melt), a shoulder forming (forming a shoulder having a gradually increased crystal diameter), a straight body forming ( A step of forming a straight body portion with a constant crystal diameter) and a step of separating (the grown single crystal is separated from the raw material melt).

  3 is an explanatory view showing a state after the grown single crystal 6 is separated from the raw material melt 2. After the formation of the straight body portion 6b is completed, the diameter is approximately the same as the diameter of the straight body portion 6b. When the single crystal 6 is pulled away from the raw material melt 2 with a diameter of 5 mm, the pulling process is completed by pulling up the seed crystal 5 at a high speed.

  However, when the seed crystal 5 is pulled up at a high speed by operating the pulling shaft 3, cracks occur in the vicinity of the pin 4 that fixes the seed crystal 5, in the vicinity of the lower end of the seed crystal 5, or in the shoulder 6 a of the crystal. May occur or the grown single crystal 6 may fall into the raw material melt 2, which is remarkable when a small-sized seed crystal is used. When the seed crystal 5 is pulled up at a high speed, the seed crystal 5 or the shoulder of the crystal is caused by the surface tension when the grown single crystal 6 leaves the raw material melt 2, the impact caused by the lifting operation of the pulling shaft 3 being stopped, or the like. It is considered that a crack is generated in the portion 6a.

  In order to avoid this problem, in Patent Document 1, a straight body portion having a constant crystal diameter is grown, and a tail portion having a crystal diameter gradually smaller than that of the straight body portion is further grown. Has been proposed to separate the material from the raw material melt. However, in the method proposed in Patent Document 1, the surface tension when the single crystal is separated from the raw material melt can be reduced due to the presence of the tail portion, but the impact caused by stopping the pulling operation of the pulling shaft is eliminated. Can not. For this reason, the fall of the single crystal still cannot be prevented, resulting in a decrease in yield. Further, the tail part is a non-product part, and the yield may be greatly reduced depending on its shape.

  Further, in Patent Document 2, when the growth of the straight body portion is completed and the single crystal is separated from the raw material melt, the rotation speed of the seed crystal is 0 to 8 rpm, and the pulling speed of the single crystal is 50 mm / min or more and 250 mm / min. In addition to the single crystal pulling operation, a method for separating the single crystal at a minimum value of less than min is proposed, and a method for lowering the crucible is also proposed. However, even with the method proposed in Patent Document 2, it is impossible to eliminate the impact caused by stopping the pulling-up operation of the pulling shaft, so that the yield is reduced as in the method proposed in Patent Document 1.

These problems are significant when growing an oxide single crystal exhibiting hard and brittleness such as TSAG (Tb ₃ Sc ₂ Al ₃ O ₁₂ ).

Japanese Patent Laying-Open No. 2008-169095 (refer to claim 1 of claims) JP 2002-0201097 A (refer to claims 1, 5, 6, and 11 of claims)

  The present invention has been made paying attention to such problems, and the problem is that the single crystal can be almost completely prevented from falling when the grown single crystal is separated from the raw material melt, and the tail portion is An object of the present invention is to provide a method for producing an oxide single crystal with a small yield reduction due to the formation of.

Therefore, in order to solve the above-mentioned problems, the present inventor has developed a unique method in which after the straight body portion and the tail portion are grown, the rotation of the pulling shaft and the pulling operation are completely stopped, and the crucible is lowered at this timing. In addition to being able to reduce the surface tension when the single crystal leaves the raw material melt, it was confirmed that the impact of stopping the lifting operation was also eliminated, and the crystal diameter at the tip of the tail part was further confirmed. D2 is φ10 mm to φ20 mm, and the distance L from the straight barrel end to the tail tip is 0.2 to 0.5 times the crystal diameter D1 of the straight barrel (L / D1 = 0.2 to 0.5) When the rotation of the pulling shaft and the pulling operation are stopped, the surface tension is remarkably reduced and an oxide single crystal exhibiting hard brittleness such as TSAG (Tb ₃ Sc ₂ Al ₃ O ₁₂ ) is grown. Valid Rukoto has been confirmed. The present invention has been completed by such technical discovery.

That is, the invention according to claim 1
A method of growing an oxide single crystal by a crystal pulling method in which a seed crystal attached to the tip of a pulling shaft is brought into contact with a raw material melt in a crucible and the pulling shaft is rotated, and the crystal diameter is kept constant. An oxide single crystal comprising a step of growing the straight body portion, a step of growing a tail portion having a crystal diameter gradually smaller than the straight body portion, and a step of separating the grown oxide single crystal from the raw material melt In the manufacturing method of
The crystal diameter D2 at the tip of the tail part is φ10 mm to φ20 mm, and the distance L from the end of the straight body part to the tip of the tail part is 0.2 to 0.5 times the crystal diameter D1 of the straight body part (L / D1 = 0.2 to 0.5), the rotation of the pulling shaft and the pulling operation are stopped, and the oxide single crystal grown by lowering the crucible is separated from the raw material melt. (However, the condition is that the outer diameter of the seed crystal is φ5 mm to φ7 mm, the crystal diameter D1 of the oxide single crystal is φ40 mm to φ50 mm, and the weight of the grown oxide single crystal is 1200 g or less).

The invention according to claim 2
In the manufacturing method of the oxide single crystal of Claim 1,
The crucible lowering speed is set to 5 mm to 10 mm / second,
The invention according to claim 3
In the manufacturing method of the oxide single crystal of Claim 1 or 2,
After stopping the rotation of the lifting shaft and the lifting operation, the crucible is lowered within 30 seconds,
The invention according to claim 4
In the manufacturing method of the oxide single crystal in any one of Claims 1-3,
The oxide single crystal is TSAG (Tb ₃ Sc ₂ Al ₃ O ₁₂ ).

According to the method for producing an oxide single crystal according to the present invention by a crystal pulling method,
The crystal diameter D2 at the tip of the tail part is φ10 mm to φ20 mm, and the distance L from the end of the straight body part to the tip of the tail part is 0.2 to 0.5 times the crystal diameter D1 of the straight body part (that is, L / D1 = 0) 2 to 0.5), the rotation of the pulling shaft and the pulling operation are stopped, and the oxide single crystal grown by lowering the crucible is separated from the raw material melt. As a result, the surface tension when the single crystal is separated from the surface can be reduced, the impact caused by stopping the pulling operation of the pulling shaft can be eliminated, and the yield reduction due to the formation of the tail portion can be reduced.

Therefore, when the oxide single crystal grown from the raw material melt is pulled away, it is possible to avoid a phenomenon such as a crack occurring near the lower end of the seed crystal or the shoulder of the single crystal, or a single crystal falling into the crucible. Therefore, it has an effect that an oxide single crystal exhibiting hard brittleness such as TSAG (Tb ₃ Sc ₂ Al ₃ O ₁₂ ) can be efficiently produced using a small-sized seed crystal.

Explanatory drawing which shows the manufacturing method of the oxide single crystal which concerns on this invention. The schematic perspective view which shows the growth method of the single crystal by the Czochralski method. Explanatory drawing which shows the state after isolate | separating the grown single crystal from the raw material melt. BRIEF DESCRIPTION OF THE DRAWINGS Schematic structure explanatory drawing which shows an example of the single crystal pulling apparatus used when implementing the manufacturing method of the oxide single crystal which concerns on this invention.

  Hereinafter, embodiments of the present invention will be specifically described.

(1) Single Crystal Pulling Device FIG. 4 is a schematic configuration explanatory diagram showing an example of a single crystal pulling device used when carrying out the method for producing an oxide single crystal according to the present invention.

  This single crystal pulling apparatus includes a computer 12 that controls the operation of each part of the apparatus, a weight sensor (load cell) 11 that detects the weight of the grown single crystal 6 and outputs a detection signal to the computer 12, and a computer 12. In response to the output control signal, the pulling shaft drive device 13 moves up and down and rotates the crystal pulling shaft based on the signal, and the control signal output from the computer 12 lifts the crucible 18 based on the signal. A crucible driving device 14 that lowers, a coil 16 that heats the crucible 18, a monitor thermocouple 17 that detects the temperature of the bottom of the crucible 18 and outputs a detection signal to the computer 2, and an indication temperature of the monitor thermocouple 17 Receives a control signal output from the computer 12 so that becomes equal to the set temperature, and supplies power to the coil 16 based on the signal. It has a configuration including a frequency oscillator 15 for feeding.

(2) Manufacturing Method of Oxide Single Crystal An embodiment in which an oxide single crystal such as TSAG (Tb ₃ Sc ₂ Al ₃ O ₁₂ ) exhibiting hard brittleness is grown using the single crystal pulling apparatus will be described.

First, the iridium crucible 18 is filled with the TSAG raw material powder weighed in the composition ratio (Tb ₃ Sc ₂ Al ₃ O ₁₂ ) and supplied with power from the high-frequency oscillator 15. Heat to a raw material melt and heat to a predetermined temperature.

  Next, the seed crystal fixed at the tip of the crystal pulling shaft is lowered by the pulling shaft driving device 13 and brought into contact with the raw material melt, and the crystal pulling shaft is rotated at a predetermined pulling speed while rotating the crystal pulling shaft at a predetermined rotation speed. The TSAG single crystal is grown by pulling up.

  However, in the present invention, the outer diameter of the seed crystal is φ5 mm to φ7 mm (5 mm square to 7 mm square), and the crystal diameter D1 (straight barrel portion) of the grown oxide single crystal is φ40 mm to φ50 mm. The condition is that the weight of the material single crystal is 1200 g or less.

  When growing a TSAG single crystal, first, a conical shoulder portion is formed, and when the TSAG single crystal is grown to a predetermined outer diameter, a straight body portion is formed by pulling and growing with a constant outer diameter (crystal diameter). . At this time, the formation angle of the shoulder outer peripheral surface is set in the range of 20 degrees to 50 degrees. If the formation angle of the shoulder outer peripheral surface exceeds 50 degrees, cracks are likely to occur at the end of the shoulder formation, and if the formation angle is less than 20 degrees, output adjustment is performed by automatic diameter control of the single crystal pulling apparatus. Becomes difficult to follow and is easily melted out from the raw material melt.

  Further, the pulling speed of the crystal pulling shaft is set within a range of 0.1 to 3 mm / h (hour), and the rotation speed is set within a range of 1 to 50 rpm.

  In this embodiment, as shown in FIG. 1, the pulling speed when growing the straight body portion 6b is set to 1.0 mm / h or less and the rotation speed is set to 10 rpm or less, respectively, and the crystal diameter of the straight body portion 6b is set. A TSAG single crystal satisfying the condition that D1 is φ40 mm to φ50 mm and the weight of the grown single crystal is 1200 g or less is manufactured.

  Then, after growing the straight body portion 6b, the crystal diameter is gradually made smaller than that of the straight body portion 6b to grow the tail portion 6c. The crystal diameter D2 at the tip of the tail portion 6c is φ10 mm to φ20 mm, and the straight body portion 6b. When the distance L from the end to the tip of the tail portion 6c is 0.2 to 0.5 times the crystal diameter D1 of the straight body portion 6b (L / D1 = 0.2 to 0.5), The rotation of the crystal pulling shaft and the pulling operation are stopped, and the oxide single crystal (TSAG) grown by lowering the crucible 18 by 10 to 30 mm is separated from the raw material melt. This separation step is preferably performed by lowering the crucible 18 within 30 seconds after stopping the rotation of the crystal pulling shaft and the pulling operation, and the lowering speed of the crucible 18 is preferably 5 to 10 mm / second.

  Thus, according to the oxide single crystal manufacturing method according to the embodiment, the crystal diameter D2 at the tip of the tail portion 6c is φ10 mm to φ20 mm, and the distance L from the end of the straight barrel portion 6b to the tip of the tail portion 6c is the straight barrel. When the crystal diameter D1 of the portion 6b is 0.2 to 0.5 times (that is, L / D1 = 0.2 to 0.5), the rotation of the crystal pulling shaft and the pulling operation are stopped, and Since the oxide single crystal (TSAG) grown by lowering the crucible 18 is separated from the raw material melt, the surface tension when the single crystal is separated from the raw material melt can be reduced, and the pulling operation of the crystal pulling shaft (operation) ) It has a remarkable effect that can eliminate the impact caused by stopping.

  In this oxide single crystal manufacturing method, the inside of the growth furnace in the single crystal pulling apparatus has a nitrogen atmosphere.

  Examples of the present invention will be specifically described below with reference to comparative examples.

[Example 1]
A TSAG (Tb ₃ Sc ₂ Al ₃ O ₁₂ ) single crystal was grown using the single crystal pulling apparatus.

First, the iridium crucible 18 is filled with the TSAG raw material powder weighed in the composition ratio (Tb ₃ Sc ₂ Al ₃ O ₁₂ ) and supplied with power from the high-frequency oscillator 15. The mixture was heated to obtain a raw material melt and heated to a predetermined temperature.

  Next, a seed crystal having an outer diameter of 5 mm fixed by a pin at the tip of the crystal pulling shaft is lowered while rotating at 10 rpm by the pulling shaft driving device 13 to be brought into contact with the raw material melt, while being pulled 44 mm at a pulling rate of 1 mm / h. The shoulder was formed to a crystal diameter of φ40 mm.

  Next, while maintaining the condition that the crystal diameter D1 shown in FIG. 1 is φ40 mm, the pulling speed of the crystal pulling shaft was set to 0.5 mm / h, and the straight body portion 6b having a length of 40 mm was formed.

  Further, the crystal pulling shaft is pulled up by 15 mm under the condition of a pulling speed of 1 mm / h until the crystal diameter to be grown is gradually reduced from φ40 mm to φ20 mm, thereby forming the tail portion 6c shown in FIG. When the crystal diameter D2 at the tip of 6c becomes φ20 mm [that is, L / D1 = 15/40], the rotation of the crystal pulling shaft and the pulling operation are stopped, and the crucible 18 is moved to 5 mm / mm within 30 seconds after the stop. The oxide single crystal (TSAG) grown at a rate of sec was pulled away from the raw material melt.

  When the seed crystal and oxide single crystal (TSAG) fixed to the tip of the crystal pulling shaft were visually checked, some cracks were found near the seed crystal, but the obtained oxide single crystal (weight) 1000 g) did not fall into the crucible 18.

  As can be confirmed from this result, even when some cracks are generated near the seed crystal, the crystal diameter D2 at the tip of the tail portion is set to 20 mm or less, and the distance L from the end of the straight body portion to the tip of the tail portion is When the crystal diameter D1 is 0.2 to 0.5 times (L / D1 = 0.2 to 0.5), the rotation of the crystal pulling shaft and the pulling operation are stopped, and the crucible is lowered. It can be seen that the single crystal grown in this manner can be prevented from falling into the crucible by separating it from the raw material melt.

[Example 2]
A seed crystal having an outer diameter of φ7 mm is applied, the crystal diameter D1 of the straight barrel portion 6b is φ50mm, the crystal diameter D2 of the tip of the tail portion 6c is φ10mm, and the distance L from the end of the straight barrel portion 6b to the tip of the tail portion 6c The TSAG single crystal (weight) was carried out in the same manner as in Example 1 except that the rotation of the crystal pulling shaft and the pulling operation were stopped when the relationship of the crystal diameter D1 of the body portion became (L / D1 = 25 mm / 50 mm). 1200 g).

  When the seed crystal fixed to the tip of the crystal pulling shaft and the oxide single crystal (TSAG) were visually checked, some cracks were found near the seed crystal, but the obtained oxide single crystal (weight: 1200 g) ) Did not fall into the crucible 18.

[Example 3]
A seed crystal having an outer diameter of φ6 mm is applied, the crystal diameter D1 of the straight barrel portion 6b is φ45mm, the crystal diameter D2 of the tip of the tail portion 6c is φ15mm, and the distance L from the end of the straight barrel portion 6b to the tip of the tail portion 6c The TSAG single crystal (weight) was carried out in the same manner as in Example 1 except that the rotation of the crystal pulling shaft and the pulling operation were stopped when the relationship of the crystal diameter D1 of the body portion became (L / D1 = 22 mm / 45 mm). 1100 g).

  When the seed crystal fixed to the tip of the crystal pulling shaft and the oxide single crystal (TSAG) were visually checked, some cracks were found near the seed crystal, but the obtained oxide single crystal (weight: 1100 g) ) Did not fall into the crucible 18.

[Comparative Example 1]
When the crystal diameter D2 at the tip of the tail portion 6c becomes φ20 mm [ie, L / D1 = 15/40], the crystal pulling shaft is pulled up, and an oxide single crystal (TSAG) grown without lowering the crucible is used as a raw material melt. A TSAG single crystal (weight: 1000 g) was grown in the same manner as in Example 1 except for the point separated from the sample.

  However, since the oxide single crystal (TSAG) was pulled away from the raw material melt by pulling up the crystal pulling shaft without lowering the crucible, the oxide single crystal (weight: 1000 g) obtained by impact by stopping the pulling operation of the crystal pulling shaft Has fallen into the crucible 18.

[Comparative Example 2]
When the distance L from the end of the straight body portion 6b to the tip of the tail portion 6c is less than 0.2 times the crystal diameter D1 of the straight body portion (L / D1 = 4 mm / 40 mm), the crystal pulling shaft is rotated and pulled. A TSAG single crystal (weight: 1000 g) was grown in the same manner as in Example 1 except that the operation was stopped and the single crystal grown by lowering the crucible was separated from the raw material melt.

  However, since it was attempted to change the crystal diameter abruptly in a range where L / D1 was less than 0.2, the control of the crystal diameter became unstable, and the tail portion did not reach the target crystal diameter. For this reason, since the tail part was reworked, the tail part became larger, and the yield was reduced by the extra consumption of raw materials. Also, since the tail part was reworked, it took extra man-hours.

[Comparative Example 3]
When the distance L from the end of the straight body portion 6b to the tip of the tail portion 6c exceeds 0.5 times the crystal diameter D1 of the straight body portion (L / D1 = 32 mm / 40 mm), A TSAG single crystal (weight: 1000 g) was grown in the same manner as in Example 1 except that the pulling operation was stopped and the single crystal grown by lowering the crucible was separated from the raw material melt.

  Since the tail part 6c was grown until the distance L from the end of the straight body part 6b to the tip of the tail part 6c was 32 mm, the crystal diameter D2 at the tip of the tail part 6c was reduced. The surface tension during separation from the raw material melt was reduced, and the obtained oxide single crystal did not fall into the crucible 18.

  However, since the tail portion 6c was grown until the distance L from the end of the straight body portion 6b to the tip of the tail portion 6c was 32 mm, the yield was reduced by the extra consumption of raw materials that were not used as the straight body portion 6b.

[Comparative Example 4]
The relationship between the distance L from the end of the straight body portion 6b to the tip of the tail portion 6c and the crystal diameter D1 of the straight body portion is the same as that of the first embodiment [that is, L / D1 = 15/40]. A TSAG single crystal (weight: 1000 g) was grown in the same manner as in Example 1 except that the rotation of the crystal pulling shaft and the pulling operation were stopped when the crystal diameter D2 was φ22 mm (when the surface tension could not be sufficiently reduced). did.

  However, since the rotation of the crystal pulling shaft and the pulling operation were stopped when the crystal diameter D2 at the tip of the tail portion 6c exceeded φ20 mm (when the surface tension could not be sufficiently reduced), the obtained oxide single crystal was crucible. It has fallen into 18

According to the method for producing an oxide single crystal according to the present invention, when the grown oxide single crystal is separated from the raw material melt, the oxide is caused by the surface tension of the melt, the impact caused by stopping the pulling operation of the pulling shaft, etc. Since the falling phenomenon of the single crystal is avoided, it has industrial applicability applied to the growth of oxide single crystals such as TSAG (Tb ₃ Sc ₂ Al ₃ O ₁₂ ) exhibiting hard brittleness.

D1 Crystal diameter of the straight body part D2 Crystal diameter of the tail part tip L Distance from the end of the straight body part to the tail part tip α Pulling direction 1 Crucible 2 Raw material melt 3 Pulling shaft 4 Pin 5 Seed crystal 6 Single crystal 6a Shoulder part 6b Straight body part 6c Tail part 11 Weight sensor (load cell)
12 Computer 13 Pull-up shaft drive device 14 Crucible drive device 15 High-frequency oscillation device 16 Coil 17 Thermocouple for monitoring

Claims (4)

A method of growing an oxide single crystal by a crystal pulling method in which a seed crystal attached to the tip of a pulling shaft is brought into contact with a raw material melt in a crucible and the pulling shaft is rotated, and the crystal diameter is kept constant. An oxide single crystal comprising a step of growing the straight body portion, a step of growing a tail portion having a crystal diameter gradually smaller than the straight body portion, and a step of separating the grown oxide single crystal from the raw material melt In the manufacturing method of
The crystal diameter D2 at the tip of the tail part is φ10 mm to φ20 mm, and the distance L from the end of the straight body part to the tip of the tail part is 0.2 to 0.5 times the crystal diameter D1 of the straight body part (L / D1 = 0.2 to 0.5), the rotation of the pulling shaft and the pulling operation are stopped, and the oxide single crystal grown by lowering the crucible is separated from the raw material melt. Manufacturing method of oxide single crystal (however, the outer diameter of the seed crystal is φ5 mm to φ7 mm, the crystal diameter D1 of the oxide single crystal is φ40 mm to φ50 mm, and the weight of the grown oxide single crystal is 1200 g or less. Condition).   The method for producing an oxide single crystal according to claim 1, wherein a descending speed of the crucible is set to 5 mm to 10 mm / sec.   3. The method for producing an oxide single crystal according to claim 1, wherein the crucible is lowered within 30 seconds after the rotation of the pulling shaft and the pulling operation are stopped. Method of manufacturing an oxide single crystal according to claim 1, wherein said oxide single crystal is a _{TSAG (Tb 3 Sc 2 Al 3} O 12).

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