accompanying drawings referring to fig1 a substrate is placed into a dual frequency high density plasma reactor the substrate is preferably formed of thermally stable materials such as potassium chloride quartz or glass silicon metals ceramics or polymers the substrate is also chemically cleaned prior to insertion into the reactor the reactor is then supplied with argon gas at a rate of 15 sccm and the reactor pressure is set at 50 mtorr the rf modulator power to a bottom electrode is turned on and the power is raised until the bias voltage reaches 300v the reactor is run for 10 minutes to clean the surface of the substrate the rf modulator power is then turned off and the reactor is evacuated to its base pressure by a vacuum pump the reactor includes a vacuum chamber 20 that can be constructed of stainless steel and should be vacuum tight inside the reactor is a substrate holder 21 that is maintained at a constant temperature by a heater 22 the heater 22 is controlled by a temperature controller 35 the substrate holder 21 is supplied with a low frequency signal by a first rf modulator 34 whose excitation frequency can be varied between 10.