A System for Calibration and Reliability Testing of MEMS Devices Under Mechanical Stress

Microelectromechanical systems (MEMS) are employed in safety-critical fields such as automotive, aerospace and medical applications. In all these fields, reliability-related system characterization receives growing attention. This includes studies on the possible deterioration of the device during manufacturing, i.e. system test in the course of fabrication, and in the application. This paper reports on a setup and a method that enables the automated analysis of mechanical stress impact on MEMS devices. The system comprises a 6-inch compatible automated wafer stage with electrical probing capability combined with an impact control unit for the application of well defined forces to the MEMS device. The impact control unit itself consists of an xyz stage for the precise positioning of an impact object that is moved against a target in a force-controlled mode. The experiments allow optical inspection during force application and can be performed either on the wafer level or using single chips. This experimental setup presents a significant improvement over an existing setup that has been applied in characterizing various MEMS devices. It is improved with respect to the maximum applicable force, accuracy in force measurement, speed of force application, and repeatability. The new setup is characterized by a maximum static force of 10 N and accuracy in force measurement of 2 mN. Further, dynamic loads can be induced to the device under test at frequencies of up to 1 kHz. As an example, the paper describes the calibration of a highly sensitive cantilever-based tactile force sensor used in the metrology of microcomponents.