In-situ test structures for ultra low leak detection

New leak detection strategies are required for MEMS packages as traditional methods are not suited due to the small size of the cavities involved. This paper presents the design, fabrication and calibration procedure for three in-situ test structures intended to monitor electrically the hermeticity of packages. The calibration results of a micro-Pirani test structure show that this test structure can be used to monitor the ambient pressure of vacuum packaged MEMS. Using a pressured tracer gas to accelerate the test, the micro-Pirani test structure can detect leak rates down to 10-15 atm.cm3.s-1.