Characterisation of a CMP nanoscale planarisation based process for RF MEMS resonators

This paper characterises a novel Chemical Mechanical Polishing (CMP) based process for the fabrication of nanometer wide transducer gaps for RF MEMS resonators. The process requires one photolithographic step less than previously reported fabrication methods and does not suffer from transducer gap widening, which otherwise strongly affects the impedance of manufactured resonators. CMP test masks were used to evaluate the ability to produce nanometer wide planarised capacitive transducer gaps and to determine the planarity of CMP based processing. As a result of this work, pattern dependent removal rates for polysilicon have been determined and design guidelines defined to optimise the yield of CMP fabricated resonators.