Wafer Level Integration of MMIC and Microwave IPD with Metal/BCB Multilayer Interconnection Based on Low Resistance Silicon

摘要

A new high-density wafer-level integration of a GaAs based monolithic microwave integrated circuit (MMIC) chipand a microwave integrated passive device (IPD) is presented. This integration technology, an important andIC-compatible option for system-in-package (SiP), utilizes bulk Si fabrication and film deposition based multichipmodule (MCM-D) process. MMIC is entirely embedded into the silicon wafer while IPDs are integrated on thedielectric layers simultaneously with the metal/BCB multilayer interconnection. Key fabrication processes andcrucial technologies are described in detail. Normal silicon wafer is selected as substrate because of its matureprocessing technology, low cost, good thermal dissipation as well as its thermal expansion matching with GaAs. Toobtain excellent microwave performances and good planarization, thick photosensitive BCB of 25um/layer isadopted as dielectric and thus the use of tapered via that is hollow inside or filled by BCB is a cost-effective way toaccomplish inter-layer connection instead of Au bump bonding or column used in dry-etch BCB process. Furtherpromotions on microwave performances are achieved by the shielding effect through ground layer coverage onsilicon surface and the application of microstrip lines. Several experiment results such as dc inter-layer connectionresistance and thermal resistance measurements are complemented to investigate the characteristic of the wholepackage. The Microwave properties of the integration sample are measured by transmission performance test from15GHz to 30GHz. The measurement results are analyzed and discussed comparing with the theoretical orsimulation results.