On-chip 3D inductors using thru-wafer vias

Three-dimensional (3D) inductors using high aspect ratio (10:1); thru-wafer via (TWV) technology in a complementary metal oxide semiconductor (CMOS) process have been designed, fabricated, and measured. The inductors were designed using 500 μm tall vias, with the number of turns ranging from 1 to 20 in both wide and narrow-trace width-to-space ratios. Radio frequency characterization was studied with emphasis upon de-embedding techniques and the resulting effects. The open, short, thru de-embedding (OSTD) technique was used to measure all devices. The highest quality factor (Q) measured was 11.25 at 798 MHz for a 1-turn device with a self-resonant frequency (f_sr) of 4.4 GHz. The largest inductance (L) measured was 45 nH on a 20-turn, wide-trace device with a maximum Q of 4.25 at 732 MHz. A 40% reduction in area is achieved by exploiting the TWV technology when compared to planar devices. This technology shows promising results with further development and optimization.