Patent ID: 8197604
Filing Date: 2012-06-12
Classification: H01L,Y10S

Abstract:
1. A method comprising: positioning a substrate at a first distance from a piezoelectric transducer; supplying a cleaning liquid between the substrate and the transducer; applying an oscillating acoustic force to the cleaning liquid by actuating the transducer, wherein actuating the transducer includes applying an alternating current and voltage to the transducer; measuring a first phase shift between the alternating current and the voltage while the substrate is positioned at the first distance from the transducer; moving the transducer relative to the substrate, thereby causing the substrate to be positioned at a second distance from the transducer; measuring a second phase shift between the alternating current and the voltage while the substrate is positioned at the second distance from the transducer, determining whether the second phase shift is different from the first phase shift measured, and based on the determination that the second phase shift is different from the first phase shift, adjusting the second distance towards the first distance to adjust the second phase shift towards the first phase shift.