Low-loss CPW lines on surface stabilized high-resistivity silicon

The authors propose a solution to the surface conduction problem in silicon monolithic microwave integrated circuits (MMIC's). An LPCVD polycrystalline silicon layer is deposited over the surface of a high-resistivity silicon wafer which is then covered with a silicon dioxide layer. The polycrystalline silicon layer effectively removes, through traps, any free electrons or holes that may have been induced at the oxide-silicon interface. The CPW lines with 1.25-μm aluminum metallization on passivated HRS substrates have an attenuation loss at 30 GHz of only 1.08 dB/cm.