Method and Apparatus for Controlling Optimal Operation of Acoustic Cleaning

Abstract

Methods and apparatuses for cleaning a surface of a substrate are presented. The method comprises positioning a substrate at a controllable 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, and moving the transducer relative to the substrate. The method further comprises, while moving the transducer relative to the substrate, measuring a value that indicates a distance between a surface of the substrate and the transducer, comparing the measured value to a desired value, and adjusting the distance between the surface and the transducer so that the measured value is maintained substantially equal to the desired value. The measured value may be the distance between the surface of the substrate and the transducer or a phase shift between an alternating current and voltage applied to the transducer.

1 . An apparatus for cleaning a surface of a substrate, comprising:
 a piezoelectric transducer;   a support operable to position a substrate at a controllable distance from the transducer;   means for providing a cleaning liquid between the transducer and the substrate;   means for measuring a value indicating a distance between a surface of the substrate and the transducer;   a feedback loop operable to control the measured value such that the measured value remains substantially equal to a desired value.   
     
     
         2 . The apparatus of  claim 1 , wherein the means for providing a cleaning liquid comprises a nozzle. 
     
     
         3 . The apparatus of  claim 2 , wherein the transducer is mounted in the nozzle, and wherein the nozzle is operable to produce a liquid column between the nozzle and the surface. 
     
     
         4 . The apparatus of  claim 1 , wherein the means for providing a cleaning liquid comprises a reservoir in which the substrate may be submerged. 
     
     
         5 . The apparatus of  claim 4 , wherein the transducer is attached to a sidewall of the reservoir. 
     
     
         6 . The method of  claim 1 , wherein the means for measuring a value indicating a distance between a surface of the substrate and the transducer comprises an optical sensor and a laser. 
     
     
         7 . The method of  claim 1 , wherein the measured value is the distance between the surface of the substrate and the transducer, and the desired value is the distance at which the particle removal efficiency (PRE) is at a maximum. 
     
     
         8 . The apparatus of  claim 1 , wherein the transducer is operable to receive an alternating current and voltage from a power source so as to actuate the transducer and apply an oscillating acoustic force to the cleaning liquid. 
     
     
         9 . The apparatus of  claim 8 , wherein the measured value of a phase shift between the alternating current and voltage applied to the transducer, and the desired value is a desired phase shift.