RF Harmonic Distortion of CPW Lines on HR-Si and Trap-Rich HR-Si Substrates

In this paper, the nonlinear behavior of coplanar waveguide (CPW) transmission lines fabricated on Si and high-resistivity (HR) Si substrates is thoroughly investigated. Simulations and experimental characterization of 50- $Omega$ CPW lines are analyzed under small- and large-signal operation at 900 MHz for a wide variety of Si substrates with nominal resistivities from 10 $Omegahbox{-cm}$ up to values higher than 10 $hbox{k}Omegahbox{-cm}$. The introduction of a trap-rich layer to recover the Si substrate nominal HR characteristics is also considered. We experimentally demonstrate that the distortion level of a CPW line lying on Si substrate decreases with the effective resistivity sensed by the coplanar structure. Si substrates of effective resistivity higher than 3 $hbox{k}Omegahbox{-cm}$ present harmonic levels below $-$80 dBm for an output power of $+$15 dBm.