System and method for controlling a polishing machine

摘要

A system for controlling a polishing machine during polishing of a workpiece, such as a semiconductor wafer, includes a carrier which has an interface surface for engaging a workpiece and establishing ultrasonic coupling thereto. At least one crystal oscillator is ultrasonically coupled to the carrier and operates at a resonant frequency in an ultrasonic band which is indicative of a desired polishing depth of the workpiece, such as the endpoint of polishing. A detector circuit provides an output signal which is representative of an output level of the crystal oscillator. A processor circuit receives the signal from the detector circuit and provides a signal to the polishing machine when the amplitude of the signal from the detector circuit indicates that the desired polishing endpoint has been reached. A number of crystal oscillators can be spatially arranged on the carrier to establish a local polishing depth detection array.