Silicon as a microwave substrate

Silicon has many advantages as a microwave substrate material including low cost and a mature technology. The lower resistivity of Si (/spl ap/10 k /spl Omega/-cm) compared to GaAs (/spl ap/10 M /spl Omega/-cm) is perceived as a major disadvantage. In this paper, we present measured and simulated results demonstrating that the losses of a coplanar transmission line (CPW) realized on silicon substrates are comparable to the losses of a CPW realized on a GaAs substrate with insulators. The loss mechanisms of Si and GaAs substrates used for microwave applications are analyzed using both microwave and semiconductor physics theory. A high resistivity Si substrate can be used both as a microwave substrate and an active element carrier permitting further integration at low cost.<>