Mechanisms for Power Deposition in Ar/SiH4 Capacitively Coupled RF Discharges

In low-pressure capacitively coupled parallel-plate radiofrequency (RF) discharges, such as those used in plasma processing of semiconductor materials, power deposition and the rate of electron-impact excitation collisions depend upon time during the RF cycle and position in the discharge. Power is coupled into the discharge in at least two ways: by way of a high-energy "e-beam" component of the electron distribution resulting from electrons falling through or being accelerated by the oscillating sheaths, and by "joule heating" in the body of plasma. This paper will discuss the method of power deposition by electrons and the spatial dependence of electron-impact excitation rates in low-pressure capacitively coupled RF discharges with results from a Monte Carlo plasma simulation code. Mixtures of argon and silane will be examined as typical examples of discharges used for the plasma deposition of amorphous silicon.