Si1−xGex pulsed plasma etching using CHF3 and H2

Selective reactive ion etching of Si over Si1−xGex and Si1−xGex over Si has been demonstrated by using a modulation-frequency, plasma-etch technique which employs CHF3 and H2 as the etch precursor gases. The selective etch crossover region appears at a modulation frequency of 2–3 Hz for a duty cycle of 50%. It is suggested that the etch selectivity phenomenon arises from the relative ion-assisted and purely chemical components of the radio frequency plasma and decaying plasma afterglow.