An Interconnecting Technology for RF MEMS Heterogeneous Chip Integration

Abstract

An interconnecting technology using a Au-Au thermocompressive bond has been successfully developed for microelectromechanical system (MEMS) heterogeneous chip integration in this paper. The Daisy chain and RF transition structures are both designed and fabricated for the electrical characterization of the interconnect scheme. Measured dc contact resistance is about 14 +/- 5 m Omega for the bonding interface of Ni (1 mu m)/Au (0.4 mu m)/Au (0.4 mu m)/Ni (1 mu m) with a pad size of 40 mu m in diameter. The electrical transition between two chips, which have coplanar waveguides (CPWs) and microstrip lines, respectively, can be well interconnected with less than -15 dB return loss and -1.8 dB insertion loss up to 50 GHz without implementing complex structure designs and extra impedance matching networks in the transition by employing this technology. Meanwhile, it is found that the mechanical strength for the interconnecting bond can be as large as 100 MPa. A low-power RF low-noise amplifier has been successfully designed, fabricated, and utilized in this paper to demonstrate the feasibility of the interconnecting technology for RF MEMS heterogeneous chip integration by integrating a Taiwan Semiconductor Manufacturing Corporation 0.18-mu m RF complimentary metal-oxide-semiconductor chip with a silicon carrier, where high Q MEMS inductors are fabricated and utilized for good circuit performance in terms of excellent impedance matching, power gain, and gain flatness.