Patent ID: 6228277
Filing Date: 2001-05-08
Classification: G01B,H01J,H01L

Abstract:
A process for etching a layer upon another layer comprising the steps of:a. mounting a substrate in an etching apparatus, said substrate having a substrate surface, and at least a first layer on the substrate surface the first layer having a top surface and a bottom surface in contact with the substrate,b. sealing the apparatus,c. etching said layer,d. directing an incident light beam onto the top surface of said first layer to create a reflected beam from the top surface of the first layer and the surface of the substrate, said incident light beam having a linear absorption in said first layer of greater than 30% per 100 Angstroms,e. monitoring the intensity of the reflected beam from the surface of the first layer and the surface of the substrate over time while said etching proceeds,f. detecting a single change in the intensity of the reflected beam, while some of said first layer remains andg. changing step c in response to step f.