MECHANISMS FOR POWER DEPOSITION IN Ar/SiH4 CAPACITIVELY COUPLED RF DISCHARGES.

In low-pressure, capacitively coupled, parallel-plate radio-frequency (RF) discharges, such as those used in plasma processing of semiconductor materials, power deposition and the rate of electron-impact excitation collisions depend on 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. The author discusses 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 are examined as typical examples of discharges used for the plasma deposition of amorphous silicon.