Patent ID: 7334479

Claim:
A method of non-contact ultrasonic thickness measurement of sputtering targets having a front surface and a front surface/bonded surface interface comprising the steps of: a) securing a target to a holder and rotating said target; b) sequentially irradiating the front surface with pulses of sonic energy at a plurality of positions at substantially normal incidence to a tangent line at a plurality of positions on the front surface, at least one of the pulses of sonic energy propagating through the front surface to the front surface/bonded surface interface; c) detecting consecutive echoes induced by said pulses of sonic energy, the echoes being reflected from the front surface and from the front surface/bonded surface interface, respectively; d) converting the front surface echoes and the front surface/bonded surface interface echoes into corresponding electric signals; e) determining transit time of a sound path between the front surface echoes and the front surface/bonded surface interface echoes based on the corresponding electric signals; f) determining thickness data of the target by multiplying known sound velocity of the target material by one half of the determined transit time, corrected for a zero offset factor; g) electronically sending the determined thickness data to a remote controller; h) collecting thickness data for a plurality of positions on the target; i) analyzing the collected data and determining the minimum thickness of the target.