Practical high-resistivity silicon-on-insulator solution for spiral inductors in radio-frequency integrated circuits

The effect of hi-h-resistivity (high-R) silicon-on-insulator (SOI) substrates on spiral inductors in radio-frequency integrated circuits (RF ICs) has been investigated by experiment and simulation. The effect of the high-R substrates on the spiral inductors saturates at a resistivity above 2-3 k Omega cm, and the resistivity must be maintained high with a thickness of about 300 mu m. The resistivity dependence of the high-R effect can be explained with a dielectric loss mechanism in silicon substrates. The thickness criterion of the effect can be explained with an inductor model that includes magnetically induced current in a ground plane. On the basis of experimental results and discussion, we conclude that a commercially available high-R wafer with carefully designed back-end process is sufficient for obtaining the maximum effect of high-R substrates.