| 摘要 |
PURPOSE:To improve the yeild and quality of elements by setting the lengthwise direction of a straight line projecting part caused at the cut-off of a wire saw as a direction in crossing with the cleavage direction so as to prevent damages of a wafer caused to cleavage at polishing process. CONSTITUTION:An orientation flat 10 is formed in parallel with the 112.2 deg. Y direction is formed to a lithium tantalate single crystal ingot 9. Then tbe ingot 9 is rotated so that the flat 10 has a minimum rotating angle of 148.2 deg. from the 112.2 deg. Y direction and fitted to a recess 12 of a processing base 11. Then wires 13-are fed in a direction of the arrow 14 orthogonal to the upper face of the base 11 to cut off the ingot 9 to obtain wafers of a desired thickness. Both-side lapping is applied to the wafer 15. In this case, the lap load is exerted only the vicinity of the waving projecting part of the wafer 15 and a tensile stress is generated in a direction at a right angle to the projecting part. However, the projecting part resides in a direction having the maximum rotating angle to cleavage faces 11'02,l'012 and 011'2, not being in agreement with the 011'2 cleavage face direction and cracks along the projecting part hardly take place.
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