PREVENTION POLYMER BUILD UP ON A PLASMA ETCH VIEW PORT
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2002-Apr-04
In a batch reactor you have two viewport open- ings, one for endpoint and the other for observation. The viewports are opening in chamber walls (anode) with quartz inserted to allow for viewing of inside the chamber. The chamber wall of plasma reactor is heated some of the heat from the wall is conducted to the quartz viewport but because of heat loss and size of the opening the center ofthe viewport is always 3 to 5 degrees cooler than the edge of viewport or chamber wall. This creates a cool spot in the plasma and a good location for non-volatile by-products to accumulate. Over time this accumulation builds up so thick that it blocks any light from passing through. When the viewport is used for detection of endpoint the build up can reduce signal which will prevent the accurate detection of endpoint.