Method and apparatus employing external light source for endpoint detection

An apparatus for determining an endpoint for stripping of a material from a surface of a substrate, comprising:

• a stripping chamber for receiving said substrate;
• a microwave generator for generating at least one reactive species for delivery to said stripping chamber for etching said material;
• a primary high energy light source;
• first optical apparatus for forming a beam of high energy light and directing the high energy light to said material on said substrate;
• second optical apparatus for collecting emanated light from said material as a secondary light beam and directing said secondary light beam through a band pass filter;
• and
• a light intensity sensing apparatus for receiving said filtered secondary light beam, measuring an intensity thereof, and generating an electric signal representative of said measured light intensity.