Performance comparison of substrate coupling effect between silicon and SOI substrates in RF-CMOS technology

Substrate coupling may severely degrade the electrical performances of high-speed and RF integrated circuits. An isolation technique study of parasitic effects due to substrate coupling between two blocks of integrated circuits in an RF CMOS 90 nm technology is presented. Isolation performances are compared for both bulk silicon (Si) and silicon-on-insulator (SOI) substrate. For every substrate, a compact electrical model matching well with measurement results is proposed for test structures composed of 50times50 mum cells surrounded with an appropriate guard ring. An isolation improvement of 10 dB is reached by an additional P-type guard ring placed around one cell and an isolation level of 45 dB is achieved at 1 GHz for bulk Si substrate