Power efficiency oriented optimal design of high density CCP and ICP sources for semiconductor RF plasma processing equipment

This paper discusses the optimization of radio frequency (RF) power efficiency in the design of low pressure and high density capacitively coupled plasma (CCP) and inductively coupled plasma (ICP) sources for semiconductor RF plasma processing equipment, based on the analysis of the effect of stray capacitance on the RF power efficiency in the plasma reactors. Historically, RF plasma processing chambers have been designed and operated using empirical methods. The electrical analysis in this paper reveals design guidelines for both CCP and ICP sources to maximize RF power efficiency by minimizing the stray capacitance in the hardware layout. It is also shown from the external electrical analysis that at low pressure, the ICP sources are usually more efficient than the CCP sources, which is in agreement with the existing experimental results on high density RF plasma sources though the associated micromechanism in plasma physics has remained to be explored. It is further concluded that the RF frequency for an ICP source should not be too high in order to avoid the deep capacitive operating region where an ICP source is inefficient. Besides, lower frequency bias RF power on the chuck has higher RF power efficiency.