Optimization of Q factor in spiral inductor on silicon

In this paper, analyzing the Q factor of the spiral inductor is done by computer simulation, the results showed that the series resistance R/sub s/ dominates the Q factor of the spiral inductor, and that increasing the substrate silicon resistance is beneficial to increasing the Q factor and decreasing the substrate noise. To increase the Q factor of the spiral inductor, the experiments of decreasing via contact resistance and etching away the substrate silicon under the spiral inductor are done. The compatibility of the 3-dimensional bulk process with the planar IC process has been solved. Using the novel method, the inductor with high Q factor of 8.4 and low series resistance of 3 /spl Omega/ is obtained, and substrate noise is reduced. This method can be used effectively in the design and manufacturing of high performance RF-ICs.