Metal Inter-Diffusion And Eutectic Wafer Bonding Processes For Advanced Mems Packaging
Authors: Sumant Sood, Robert Hergert; and Oliver Treichel Company: SUSS MicroTec Inc. and SUSS MicroTec Lithography GmbH Date Published: 11/5/2013
IWLPC (Wafer-Level Packaging)
Abstract: Until recently, the most commonly used methods for wafer level packaging of high volume MEMS sensors such as pressure sensors, accelerometers and gyroscopes either involved glass frit and anodic bonding. Anodic bonding requires the uses of a glass substrate and suffers from severe alkali-ion contamination while glass frit bonding is an inherently dirty process in addition to having large seal width requirements. Metal and eutectics based wafer bonding has several advantages including enhanced hermeticity and vertical integration capability, allowing for reduction in die size and cost savings with improved device performance. Additionally, with the traditional CMOS foundries now foraying into MEMS manufacturing, there is a demand for MEMS wafer level packaging using CMOS foundry compatible materials. The paper reviews various metaldiffusion and eutectic wafer level bonding techniques with emphasis on CMOS compatible Al-Ge eutectic bonding.