Practical High-Resistivity Silicon-on-Insulator Solution for Spiral Inductors in Radio-Frequency Integrated Circuits

The effect of high-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 kΩ cm, and the resistivity must be maintained high with a thickness of about 300 µm. 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.