Patent ID: 6174407
Filing Date: 2001-01-16
Classification: H01J,H01L

Abstract:
An apparatus for etching a first side of a semiconductor wafer down to a level, comprising:an etching chamber;a wafer chuck configured to (i) engage said wafer by a second side of said wafer, and (ii) position said wafer in said etching chamber;a light source unit positioned such that light signals generated by said light source unit are directed toward said wafer;a light detector positioned such that said light signals generated by said light source unit emanate from said wafer and are directed toward said light detector; anda light receiving unit positioned such that said light signals generated by said light source unit emanate from said wafer and are received with said light receiving unit, wherein said light signals upon reaching a specific intensity are refracted by said light receiving unit when said wafer has been etched down to said level such that said light signals generated by said light source unit are prevented from being detected by said light detector.