Control of charged particle machining of substrate - is particularly for thickness control and uses substrate resonant frequency

摘要

A control system is for machining substrates, particularly piezo-electric substrates used as high frequency resonators, the machinining being achieved by ionic bombardment. Control of the ion beam is derived from a comparison of the resonant frequency of the substrate and a reference frequency, such that when the two frequencies match, the substrate thickness required has been achieved and machining stops. The control technique is particularly applicable to substrates intended to work in the 40 MHz to 500 MHz band. The substrate carries electrodes on both its faces leaving the central area free for bombardment, the electrodes transmitting the frequency generated during the process to detection and control circuits.