High resolution silicon accelerometer

Yun Kwang Jeon, Soon Chang Yeon, Yong Hyup Kim, Seung Wu Rhee, Shi Hwan Oh
Department of Aerospace Engineering, College of Engineering, Seoul National University, KR

Keywords: : Microaccelerometer, Differntial capacitive, Eutectic bonding

Abstract:
High precision micro-accelerometers are used in many applications such as automotives, aviations and aerospace navigation systems. In this paper, a lateral capacitive micro-accelerometer with μg level resolution has been designed and fabricated using simple micromachining process. Large sensing area and large proof mass are important in the design of high precision accelerometer.[1,2] To satisfy these requirements, the differential capacitive comb type is adopted for the sensing part, and the bulk-micromachining is used to define the micro structure. A glass wafer is used to make electrical isolation between the proof mass and electrode. Anchor and gold electrode is pre-defined on the silicon wafer and glass wafer respectively, and bonded each other. Eutectic bonding is used for bonding process of silicon and glass. The role of gold film is not only an adhesion layer but also an electrode layer. The stiction problem which can occur due to wet release process can be removed by using this process. The accelerometer has a 50μm-thick proof mass, 870μm 1027μm in size with 3μm sensing gap defined by deep RIE process. Spring has 3~5μm thickness and 200~300μm length. Proof mass weighs 15.84μgram, and natural frequency is 13.78KHz. This accelerometer is designed to control spring stiffness and force balancing loop to improve resolution.

NSTI Nanotech 2003 Conference Technical Program Abstract