Die-Level Vacuum Packaging of Mems Devices with Non-Evaporating Getters

In this article original method of vacuum packaging in ceramic package 5142.48-A with non-evaporating getter inside is described. Some MEMS devices such as gyroscopes, accelerometers and resonators often require high and stable vacuum for operational capability. It is known two main approaches to the vacuum packaging of MEMS devices: hermetization on the wafer level and on the die level. Die-level vacuum packaging can be implemented by sealing the die in ceramic package providing excellent hermeticity with sufficiently low leak rate. However, because of outgassing from materials of the package it is difficult to achieve stable vacuum over all MEMS device lifetime. To prevent vacuum degradation it is necessary to use special materials that can remove active gases from the package by chemical sorption named getters. In this work tablet-shaped non-evaporating getter with thickness of 0.7 mm made of titan-vanadium alloy with activation temperature near 525 °C was used. For the vacuum packaging workflow new special vacuum chamber is designed. It may contain four MEMS devices simultaneously. During the process of getter activation heating was provided by halogen lamps G12 35 Wplaced over the caps of the ceramic packages with a little gap. It is defined that in deep vacuum full power of one lamp can heat the cap of the package to the temperature more than 600 °C. Probable overheating is excluded by means of the newly-designed programmable device — power switch, which can maintain required temperature in automatic mode for the necessary time. Temperature control is realized by no-contact pyrometrical method. During the experiment all necessary parameters providing specified temperature profile of the process were determined. Efficiency of the developed vacuum packaging workflow is successfully confirmed by the high and stable Q-factor of fabricated MEMS gyroscopes.