Research On Millimeter Wave Interconnects Under Silicon-based MEMS Process

With the development of information technology,the processing speed,signal bandwidth and information capacity are promoted rapidly.Therefore,low loss,high bandwidth and low crosstalk interconnects are imperative in high-speed transmission system.Conventional interconnects such as microstrip and stripline are both open structures and hence have disadvantages of large crosstalk and serious radiation,and thus these conventional interconnects cannot meet the requirements of high-speed data transmission.However,substrate integrated coaxial line(SICL)is preferred recently as a novel transmission line because of the ultra-wideband,low loss and low crosstalk features.SICL can be widely utilized to millimeter-wave system-in-package(SIP)or integrated circuit(IC)applications.In this dissertation,design methodologies and fabrication procedures of SICL interconnects are discussed in detail.In addition,differential SICL interconnects are also studied under silicon-based MEMS process.Firstly,analytical formulas for characteristic impedance of SICL are proposed.Accuracies of the proposed formulas are validated with full-wave simulation tools.Furthermore,SICL-based interconnects including quasicoaxial transitions and step impedance matching structures are discussed in detail.These optimized designs can alleviate impedance discontinuities in SICL-based interconnects.Simulation results show that the proposed SICLbased interconnects can support ultra-wideband millimeter-wave signal transmission.Secondly,silicon-based MEMS process is introduced in this part.Fabrication procedures of silicon-based MEMS process are discussed detailedly and the proposed SICL-based interconnects are fabricated successfully.The fabricated SICL-based interconnects are measured with vector network analyzer(VNA)and oscillator.The return loss is 10 dB in the frequency range of DC to 110 GHz and the 3 dB bandwidth is from DC to 77 GHz.Furthermore,the fabricated SICL-based interconnect can transmit 30 Gbps digital signals.Finally,differential SICL is introduced in this part.Propagation properties of differential SICL are discussed and differential transition structures are designed.The differential SICL interconnects are analyzed by full-wave electromagnetic simulation tools.The insertion loss is less than 2 dB and the return loss is larger than 15 dB from DC to 110 GHz.Furthermore,the differential SICL interconnect has very low dispersion in the range of DC to 110 GHz,which is very suitable for high-speed data transmission.