Design and modeling of a completely CMOS compatible RF varactor and a MUMPs varactor

Micro electro mechanical system (MEMS) technology has shown its bright future in many different fields, especially in space and radio frequency (RF) systems. In wireless communication systems, passive elements including tunable capacitors and inductors often need a high quality factor and high self-resonant frequency. High-quality tunable capacitors and inductors can lead to improved power or figure of merit in low noise amplifiers, low insertion loss in band-pass filters, and better phase noise and power in voltage-controlled oscillators (VCOs). By using MEMS technology, we can greatly shrink the cost and the footprint of RF circuits since all the off-chip components such as inductors and capacitors can be fabricated and integrated into a whole single chip at one time. Our research is directed by the purpose of developing more powerful RF components. The goal of this project is to build a completely on-chip IC-compatible, high-Q variable capacitor using vertical electro-thermal actuators. The variable capacitor has been accomplished through building an all-Polysilicon microstructure. The fabrication procedure is fully compatible with a standard IC integration. The research results presented at the figure1 shows an SEM of the top-view of a fabricated capacitor with a nominal capacitance value of 1900 fF