Dual-mode microwave/radio frequency plasma deposition of dielectric thin films

Thin films have been deposited in a ‘‘dual frequency mode’’ plasma, in which differing amounts of radio frequency (rf, 13.56 MHz) power were applied to the substrate, while sustaining the plasma with constant microwave (2.45 GHz) power. We report results pertaining to deposition of silicon oxide and organosilicon thin films. The rf-induced negative dc self-bias voltage is shown to affect plasma-chemical reactions, causing very significant changes in the deposition rate, film composition, and dielectric properties of the resulting materials. This provides a powerful new technique for producing ‘‘tailored’’ films, while preserving the important advantages of high deposition rates and low substrate temperatures.