An approach for fabricating high-performance inductors on low-resistivity substrates

Porous Si layers up to 250 /spl mu/m in thickness are used to isolate spiral inductors from low resistivity substrates. Wafer curvature and secondary ion mass spectroscopy (SIMS) analysis are done to address the manufacturability issue of porous Si. Spiral inductors with a single level Al on 2 in, p-type substrates of 0.008 /spl Omega/-cm resistivity are demonstrated with Q<6 at 3 GHz for an L of /spl sim/8 nH. Large inductors with L/spl sim/100 nH have been shown with the first resonance frequency at 1 GHz. The expected performance potential as well as factors that could be limiting the Q are discussed.