High-performance inductors using capillary based fluidic self-assembly

In this paper, a batch microfabrication process is presented for creating high aspect ratio, micron-sized helical and toroidal inductors with Q greater than or equal to 50 at multi-GHz frequencies. With a maximum processing temperature of only 220 degreesC, the inductors can be fabricated on top of standard CMOS wafers. This process can also be used to create inductor chiplets, which are polymer-encapsulated inductors with the same form factor as an EIA (Electronics Industries Association) standard 0201 surface mount device. The chiplets can be assembled onto CMOS wafers using a fluidic microassembly technique. This technique allows for multiple electrical interconnects to the inductor chiplets. The 40-mum gap between the substrate and assembled inductor increases the Q by a factor of similar to 3 compared to as-fabricated inductors. Assembled and as-fabricated inductors have been characterized on similar substrates and have maximum Q values of 50 and 15 with resonant frequencies of 10 GHz and 9 GHz, respectively. Performance of the assembled inductors is nearly comparable to that of inductors as fabricated and tested on quartz substrates.