High frequency properties of silicon-on-insulator and novel depleted silicon materials

High frequency properties of substrates such as substrate losses and cross- talk were investigated for silicon-on-insulator (SOI) materials and for a n ovel depleted silicon material. Simulations were made to reveal high freque ncy properties of SOI MOSFETs made on fully depleted SOI materials of diffe rent substrate resistivities. The substrate resistivity was varied from 0.0 1 Omega cm to 10 k Omega cm, It was found that the high frequency propertie s of intrinsic transistors were independent of the substrate resistivity, b ut a system consisting of both active and passive components showed reduced cut-off frequency, f(T),. and maximum oscillation frequency, f(max), for l ow substrate resistivities. The obtained information on the importance of t he silicon substrate resistivity has been used to manufacture a depleted si licon material by use of wafer bonding. The novel material is intended as s ubstrate for high frequency applications. The space charge regions surround ing a bonded silicon/silicon interface deplete the silicon thereby reducing substrate losses at high frequencies. The novel material has been characte rised electrically for frequencies up to 40 GHz using metal transmission li nes and cross-talk structures on its surface. The measurements have been co mpared to similar measurements on bulk silicon, SIMOX and quartz substrates . The depleted region of the novel material shows up in its electrical char acteristics. (C) 2001 Elsevier Science Ltd. All rights reserved.