Evolving MEMS qualification requirements

In the early 1990s, Microelectromechanical Systems (MEMS) products were qualified using a suite of application-specific stress tests that were previously developed and used for mechanical sensors. For example, automotive companies required MEMS accelerometers to pass the same stress tests as mechanical accelerometers, including shock, vibration, temperature cycling, acceleration, and operating life tests. Semiconductor companies augmented these traditional stress tests with other tests to assess the robustness of MEMS products, such as cyclic sensor deflection, ESD, and latch-up tests. The proliferation of MEMS products and applications, especially in consumer electronics, poses major challenges to MEMS suppliers qualifying products for a wide range of applications and operating environments. Unlike automotive companies, many consumer electronics companies do not have sensor-specific reliability requirements; instead, they increasingly impose the same stress test requirements specified for all other ICs. Products with MEMS elements directly exposed to the outside world (such as microphones) may have intrinsic failure mechanisms that preclude passing all industry-standard stress tests. In addition, these standard stress tests do not adequately assess the reliability of MEMS products in terms of sensor robustness to failure mechanisms such as stiction, fracture, and particles. Thus, MEMS suppliers and their customers sometimes need to develop and agree upon a set of stress tests and acceptance criteria that are tailored to a particular category of MEMS products. This paper will focus on the qualification requirements for four categories of MEMS products used in diverse applications and operating environments, and then will discuss likely future trends and challenges in qualifying MEMS products.