CMOS Switch Buck DC-DC Converter Fabricated in Organic Interposer with Embedded Zn-Fe Ferrite Core Inductor

摘要

To achieve a package-level DC power grid for the next-generation power delivery to LSIs, multiple point-of-load (POL) buck DC-DC converters must be integrated into the package. We developed a 180 nm CMOS switch DC-DC buck converter for the POL DC power supply using a Zn-Fe ferrite core planar inductor embedded in an organic interposer. The embedded inductor had a 25 μm thick copper spiral coil sandwiched by 10 μm thick Zn-Fe ferrite thick film fabricated using the spin-spray method, which exhibited an inductance of 4.6 nH and a Q-factor of 11 at 50 MHz. A 180 nm CMOS switch was mounted using a flip-chip scheme on the organic interposer with the embedded inductor. The developed 50 MHz switching CMOS switch buck DC-DC converter exhibited a power conversion efficiency of about 68% when the input voltage was 2 V, the on-duty ratio was 0.5, the output voltage was 0.855 V, and the current was 1 A.