A method for detecting the end point of etching wafers and the like by reflective means. Typically, a detected reflectance signal will have a threshold level representing a lack of substantial etching, a dip in the threshold level representing the commencement of etching and an inflection level representing...http://www.google.co.uk/patents/US4317698?utm_source=gb-gplus-sharePatent US4317698 - End point detection in etching wafers and the like
