Optimization of a MEMS variable capacitor with high linearity and large tuning ratio

A novel micro-electro-mechanical system variable capacitor with a nonplanar top plate and a side leverage electrode structure is proposed to achieve a large tuning ratio and excellent linearity. A theoretical analysis of the structure is performed, including both a mechanical analysis and an electrical analysis. The effects of the structural parameters on the linearity were analyzed and a design method was derived to optimize the linearity. A simulation using CoventorWare was carried out to verify the capacitor performance with particular emphasis on the capacitance versus voltage (C–V) response. The results show a high linearity factor of 99.92% between 0.077 and 0.238 pF (the linear C–V response range) that corresponds to a linear capacitance tuning ratio of 309%.