Design, Fabrication and Testing of Wafer Level Vacuum Package for MEMS Device

Abstract

A wafer level vacuum package with getters deposited on the cap wafer is developed for an accelerometer device. An accelerometer wafer and cap wafer is bonded together in a vacuum of 1 milli torr and is characterized using a MEMS motion analyzer (MMA). Vacuum inside the package is measured indirectly by measuring the Q factor response of the accelerometer structure inside the package. The obtained results indicated that there is variation from the center to the edge of the wafer. This may be due to difference in the outgassing of the package. Different reliability tests on the wafer level package showed the package is robust to the reliability conditions. A progressive test on Q factor for different cycles of reliability test proven that there is no shift in the measurement value. A 3D wafer level package for accelerometer device is also developed to meet the requirements of vacuum packaging. Hermeticity and CV test showed that no degradation in the device performance when subjected to reliability tests.