Characteristics Of Varactors In Rf Cmos Process Modeling

With the overgrowth in wireless technology and the scaling of CMOS technology up to nanoscale,developing high-performance CMOS RF integrated circuits has bccome an important goal for pushing the wireless communications forward.RF integrated circuits play an important role in sending or receiving radio singals in radio communication system,it brings forth demand for the related RF modules.Varactors are the critical device in RF modules circuits such as tunable filters,LC VCO and so on.So it is very important to design high quality varactors.A varactor with high Q factor and large tuning range is a mandatory prerequisite for a current efficient LC-tank VCO design.Commonly used varactors include the p-n junction varactors,PMOS varactors and accumulation mode(n or p-type) varactors.The thesis discusses the results from the benchmarking of different two and three-terminal MOS varactor structures.These structures are made using advanced 0.13um and 65nm CMOS process in Semiconductor Manufactaring International Corporation(SMIC).The discussion mainly consists of following parts:1) Compare and analyze the advantages and disadvantages of the different structures of varactors.2) Study the effect of layout parameters and process parameters on the Q factor and the tuning range of the varactors.The layout parameters includes finger length,finger width,finger space and the number of fingers,While the gate oxide thickness,doping profile,doping concentration and so on are the process parameters.The test results show the tradeoffs between the Q factor and tuning range dependant on these parameters.3) Build the spectre model for the best type of varactor—accumulation mode Metal-Oxide-Semiconductor(MOS) varactor using Agilent Software (ICCAP).