conditions to exist at any given flow rate it is necessary to adjust the microwave power and rf bias voltage or rf power in order to obtain the optimum deposition rate in general increasing the microwave power increases the deposition rate and increasing the rf bias decreases the deposition rate as noted the process of forming a silicon dioxide layer has a sputtering aspect in addition to the deposition aspect sputtering occurs all the time that oxygen is present in the reaction chamber provided the rf bias is on and there is material to sputter and thus in particular sputtering takes place simultaneously with deposition additionally in at least some cases it is desirable to perform at least one sputtering step in alternation with deposition i e without reacting additional material to be deposited this is readily performed by simply shutting off the flow of teos or tmcts for example at a negative dc bias of 500 v wells can be filled with void free oxide by deposition with sputtering in a single step by contrast at a dc bias of only 300 v at least one sputtering step without deposition may be required to achieve similar results thus for example fig2.