Vacuum Degree Measurement of MEMS Vacuum Package Based on DDS

This paper adopts quartz crystal as a sensor for measurement of vacuum degree which is integrated into the internal cavity of the MEMS package and is excited by an exciting source which is formed by direct digital synthesizer (DDS). The corresponding voltage signal is provided as output by using phase and amplitude comparison circuits to compare the phase and amplitude of the signal from both ends of the quartz crystal. Then it is transmitted to the SCM after AD conversion and can measure and monitor the vacuum degree of the internal cavity of the MEMS package after processing and calibration