Method and apparatus for electron beam processing of substrates

An electron beam substrate processing apparatus, comprising:

• a substrate processing chamber defined by sidewalls, a bottom, and a top;
• a spindle motor assembly moveably disposed within the substrate processing chamber;
• a spindle shaft extending from the spindle motor assembly toward the top;
• a substrate support member disposed on an end of the spindle shaft distal the spindle motor assembly, the substrate support member having a substrate supporting surface thereon;
• a first encoder wheel disposed on the spindle shaft and positioned adjacent the substrate support member;
• a first optical detector positioned in optical communication with the first encoder wheel, the first optical detector being configured to output rotation data signals in response to detected rotation of the first encoder wheel;
• a second encoder wheel disposed on the spindle shaft and positioned adjacent the substrate support member;
• a second optical detector positioned in optical communication with the second encoder wheel, the second optical detector being configured to output pattern data signals in response to detected rotation of the second encoder wheel, said pattern data signals outputted by said second optical detector different than said rotation data signals outputted by said first optical detector;
• and
• an electron beam assembly disposed on the substrate processing chamber and configured to direct an electron beam onto a surface of the substrate for processing.