Patent ID: 7322243

Claim:
An acoustic wave sensor system for monitoring the etchability of a material exposed to an etchant, the sensor system comprising: an acoustic wave sensing device having a piezoelectric substrate, and a pair of electrodes, coupled to said substrate, said pair of electrodes being adapted and arranged to generate an acoustic wave propagating in the device upon application of a voltage potential and to transform the propagating wave into an output response, a selective material disposed on said substrate, said material being chemically reactive with said etchant such that said material is etchable by said etchant, wherein one of said electrodes is at least partially formed from said selective material or has said selective material disposed thereon, and wherein the other of said electrodes is made inactive to said etchant; and at least one reflector for reflecting the propagating wave back to at least one electrode; whereby, said sensing device can provide an output response in which changes in frequency, phase or other propagation characteristics of said wave caused by etching of said selective material can be analyzed to evaluate the etching rate or etchability of said selective material.