A power inductor integration technology using a silicon interposer for DC-DC converter applications

In this paper, a new power inductor integration technology using a silicon interposer for DC-DC converter applications is proposed and experimentally demonstrated. Using this technology, coreless spiral inductors can be embedded from the back of a silicon interposer and connected with the front-side metal routing through TSVs (through-silicon vias). Trenches for the inductor windings and TSVs are etched from the back of the silicon interposer and filled with copper by using a two-step electroplating process. In this way, process difficulties and limitations in current TSV based interposer technologies for embedded power inductor applications can be overcome. Using this embedded power inductor integration technology, a 4.2 μH power inductor is embedded at the backside of a silicon interposer and integrated with a buck converter IC and LED chips to form a compact LED system. The buck converter in the LED system achieves an overall power efficiency of 69% while the size of the system is reduced by 5 times compared to the discrete counterparts. The silicon interposer embedded power inductor shows a good power efficiency of 89%.