Takehito Okabe

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.

A 2.4-GHz/5-GHz CMOS low noise amplifier with high-resistivity ELTRAN(R) SOI-Epi/sup TM/ wafers

The performance of radio frequency integrated circuits (RFICs) in silicon-on-insulator (SOI) technology can be improved by using a high-resistivity SOI substrate. We investigated the correlation between substrate resistivity and the performance of a low noise amplifier (LNA) on ELTRAN SOI-Epi wafers, whose resistivity can be controlled precisely. The use of high-resistivity ELTRAN wafers improves the Q-factor of spiral inductors, and increases the gain and narrows the bandwidth of the LNA.