A problem in the manufacture of semiconductor wafers exists in that reaction product adhering to a quartz member is peeled off and falls on wafers, thus causing particles to contaminate the wafers. In system of introducing electro-magnetic waves from the outside via the quartz member, an inventive high-density plasma etching system for processing wafers by introducing electro-magnetic waves generated by a TCP electrode into a vacuum chamber via a quartz top board and by generating plasma by exciting gas within the chamber comprises a far infrared ray heater disposed above the quartz top board to heat the quartz top board by radiant heat of infrared rays generated from the far infrared ray heater, reducing the product adhering to the quartz member and thus the contaminating particles, thereby improving the yield of the wafers.