Determination of actual defect size in cathode sputter targets subjected to ultrasonic inspection

A method for eliminating defective targets having an unacceptable amount of internal defects larger than a predetermined size, comprising the steps of:

• obtaining an ultrasonic measurement of the size of an actual internal defect having an unknown size in a sputter target material by scanning the material and recording an amplitude of a signal generated;
• obtaining a metallurgical measurement of the size of the internal defect by exposing the internal defect and measuring the actual size thereof with the use of an optical measuring device;
• correlating the ultrasonic measurement with the metallurgical measurement to obtain a correlation factor for the sputter target material that when multiplied by a future ultrasonic measurement of an internal defect will provide the actual size for that defect;
• obtaining an ultrasonic measurement for each of one or more internal defects having an unknown size within a sputter target comprised of the sputter target material;
• multiplying the ultrasonic measurement for each internal defect by the correlation factor to determine the actual size of each internal defect;
• and
• accepting a sputter target in which the number of the internal defects having an actual size greater than the predetermined size is less than a maximum acceptable amount.

A method for eliminating defective aluminum targets having an unacceptable amount of internal defects larger than a predetermined size, comprising the steps of:

• obtaining an ultrasonic measurement for each of one or more internal defects having an unknown size within a sputter target comprised of aluminum or an aluminum alloy;
• multiplying the ultrasonic measurement for each internal defect by a correlation factor of about 0.1 to determine the actual size of each internal defect;
• and
• accepting a sputter target in which the number of the internal defects having an actual size greater than the predetermined size is less than a maximum acceptable amount.