Integration of Foundry MIM Capacitor and OSAT Fan-Out RDL for High Performance RF Filters

Abstract

5G communication has been widely implemented since year 2020, especially for FR1 sub-6GHz range. Band n77, n78 and n79 are three critical bands in the 5G FR1 because of higher frequency and much wider bandwidth - This also brings new challenge on filter design. In this work, we propose a new structure which combines OSAT Fan-Out RDL inductors and foundry MIM capacitors to enhance filter performance. A 800 MHz LPF test vehicle indicates this new structure is able to sustain 38 dBm at least, which is better than 36 dBm in the conventional IPD. Band pass filters for band n77 and n79 are designed and fabricated by this new structure as well. The insertion loss is about 1.44 dB for band n77 and 2.07 dB for band n79; The maximum sustainable input power is 34 dBm for both n77 filter and n79 filter. Besides single filter, Fan-Out RDL can replace conventional coreless packaging substrate to realize a thinner RF FEM.