JP2013209257A5 - - Google Patents

Description

The difficulty in growing a sapphire single crystal is that a large-diameter and long ingot is grown while suppressing the introduction of bubbles and defects. Bubbles and defects are easily introduced due to irregular melt fluctuations and convection, melt temperature distribution, temperature changes, and the like. In order to suppress these irregular factors, it is necessary to add appropriate and delicate control to the conditions that change as the ingot grows. Currently, sapphire single crystals are mainstream production and supply by kilometers prosulfuron method, in order to grow a large diameter c-axis sapphire single crystal CZ method has many problems.

In the present invention, the alumina melt is preferably heated by a resistance heating method. In this case, the crucible is preferably a molybdenum crucible, and it is preferable to dispose a resistance heater around the molybdenum crucible and to heat the alumina melt by radiant heat from the resistance heater. In the case of the resistance heating method, the alumina melt is heated together with the crucible by radiant heat from a resistance heater provided around the crucible. As a result, the alumina melt has a longitudinal temperature gradient. The viscosity of the alumina melt is very high and is not stirred so much that a longitudinal temperature gradient is maintained. As a result, crystal growth in the c-axis direction under the surface of the alumina melt can be promoted. Furthermore, since the molybdenum crucible is less expensive than the iridium crucible, the manufacturing cost of the sapphire single crystal can be reduced.

In the present invention, the crystal length A of the single crystal portion is pulled above the liquid level position of the alumina melt, the single crystal part fraction growing under the liquid surface of the alumina melt the crystal length B The sapphire single crystal is preferably pulled up so that the ratio B / A is 0.2 or more and 2 or less.

Furthermore, in the sapphire single crystal according to the present invention, the ratio B / A between the crystal length A of the single crystal portion from the enlarged diameter portion to the straight body portion and the crystal length B of the single crystal portion of the reduced diameter portion is 0.2 or more. 2 or less. The sapphire single crystal according to another aspect of the present invention is a sapphire single crystal at the lower end of the seed crystal by immersing a c-axis sapphire seed crystal in an alumina melt and pulling the seed crystal upward while rotating. In the c-axis direction, the crystal length A of the single crystal portion pulled up above the liquid surface position of the alumina melt, and the single crystal grown below the liquid surface of the alumina melt. the ratio B / a of the crystal length B of the crystal unit content, characterized in that 0.2 to 2. According to the present invention, it is possible to provide a high-quality sapphire single crystal in which bubbles and defects are not introduced into the crystal portion.

Thereafter, when the single crystal reaches a predetermined length, the single crystal is taken out from the alumina melt, and the pulling is finished. At this time, by pulling sapphire single crystal 20 by pulling mechanism 19, and disconnects the single crystal from the melt (step S 8). Thus, the sapphire single crystal 20 is completed.

As shown in FIG. 3C, the sapphire single crystal 20 obtained by the present embodiment includes a crystal length A of the single crystal portion pulled upward from the liquid surface position of the alumina melt, and the alumina melt. the ratio B / a of the crystal length B of the single crystal part fraction growing under the liquid surface is 0.2 to 2. In other words, the ratio B / A between the crystal length A of the single crystal portion from the enlarged diameter portion to the straight body portion and the crystal length B of the single crystal portion of the reduced diameter portion is 0.2 or more and 2 or less. The shape of such a sapphire single crystal ingot is a shape peculiar to a sapphire single crystal with few bubbles manufactured by the above manufacturing method.

(Example 2)
Next, a sapphire single crystal was grown under the same conditions as in Example 1 except that the target diameter of the single crystal was variously changed. The target diameter of the single crystal to be grown was set to four conditions of 70, 100, 150, and 180 (mm). The crystal pulling rate of 3 mm / hr, and the crystal rotation speed and 12 rp m.

As is clear from Table 3, when the crystal rotation speed was as low as 6 rpm, the interface shape was U-shaped, and bubbles were introduced at a high density. Further, when the crystal rotation speed was as high as 30 rpm, the crystal interface shape was twisted, making it impossible to continue crystal growth. On the other hand, when the crystal rotation speed was 8 rpm and 25 rpm, the interface shape was V-shaped and there were few bubbles. Furthermore, when the crystal rotation speed was 10 rpm and 18 rpm, the interface shape was V-shaped and there were no bubbles. From the above results, it was found that the crystal rotation speed is preferably 8 rpm or more and 25 rpm or less, more preferably 10 rpm or more and 18 rpm or less.

Claims (8)

A method for producing a sapphire single crystal in which a c-axis sapphire seed crystal is immersed in an alumina melt in a crucible, and the seed crystal is pulled upward while rotating the seed crystal to grow a sapphire single crystal in the c-axis direction at the lower end of the seed crystal. Because
The sapphire single crystal is grown below the surface of the alumina melt, and the seed crystal is pulled upward so that the single crystal growth portion that grows in the melt does not reach the bottom of the crucible. A method for producing a sapphire single crystal.   2. The method for producing a sapphire single crystal according to claim 1, wherein a side surface shape of a single crystal growth portion grown in the melt is a substantially V-shape protruding downward.   The method for producing a sapphire single crystal according to claim 1 or 2, wherein a pulling rate of the seed crystal is 0.5 mm / hr or more and 10 mm / hr or less.   4. The diameter according to claim 1, wherein a diameter of a single crystal growth portion that grows in the melt when pulled up from the alumina melt is not more than 2/3 times a diameter of the crucible. A method for producing a sapphire single crystal.   The method for producing a sapphire single crystal according to any one of claims 1 to 4, wherein a rotation speed of the seed crystal is 8 rpm or more and 25 rpm or less.   The sapphire single crystal according to any one of claims 1 to 5, wherein a molybdenum crucible is used as the crucible, a resistance heater is disposed around the molybdenum crucible, and the alumina melt is heated by a resistance heating method. Production method. A crystal length A of the single crystal portion is pulled above the liquid level position of the alumina melt, the ratio B / A of the crystal length B of the single crystal part fraction growing under the liquid surface of the alumina melt is The method for producing a sapphire single crystal according to any one of claims 1 to 6, wherein the sapphire single crystal is pulled up to be 0.2 or more and 2 or less.   Sapphire characterized in that the ratio B / A of the crystal length A of the single crystal portion from the enlarged diameter portion to the straight body portion and the crystal length B of the single crystal portion of the reduced diameter portion is 0.2 or more and 2 or less Single crystal.