Study On MEMS Piezo-resistance 3D Micro Tactile Probe And Application In NMM

In measurement field of micro structure and device's 3D dimension, position, and topography, the coordinate measurement method and instrument with large range and high precision play important roles. As the probe of Nanomeasuring machine (NMM), a MEMS 3D micro tactile probe based on piezo-resistance effect is developed. Based on the NMM, probe performance test and measuring system is constructed. The follow is the main contents of this paper:1. Based on structure matrix analysis and material mechanical theory, a mechanical module of probe is presented. The stress distribution of beam, stiffness, sensitivity, and linearity of probe are calculated. Relationship between displacement of probe tip and stress distribution of piezo-resistors is set up. Influence mechanism of the static force and dynamic force between probe and sample during the measurement, induced by probe structure parameters and coordinate measurement machine parameters is studied. Meanwhile, 3D analytical module of piezo resistors is presented. Stress distribution of beam is analyzed. The direction, type, number, arrangement and dimension of piezo resistors are designed.2. Through the ANSYS Finite Element Method, the stress distribution, stiffness, and resonance of probe are simulated. The suspending topological structure and stylus are designed. For the consideration for MEMS technics implement, methods and equipments about position and alignment between stylus and intermediate are presented, and precision assembly with self-alignment and self-position is achieved. Compared with the probe performance of standard parameters, according to the influence degree of structure parameters of beam, intermediate body, and stylus, optimum structure and parameters are chosen. Simulated data of optimum structure are compared and validated with the conclusion of theoretical anlysis.3. The MEMS layout of suspending structure is designed. Key technics, such as piezoresistors, convex compensation of KOH are studied. Cooperated with Department of Microelectronics of Beijing University, the suspending structure is fabricated. Using the high precision fabrication technique, the tip and stylus are machined. According to requirement of workspace of NMM,package and fix house of probe are designed to connect to signal conditioning circuit.4. Combined with NMM positioning platform, the performance test system of micro tactile probe is constructed. The filter and amplification theory and method of output weak signal by Wheatstone bridge of piezoresistors are studied. Signal conditioning circuit and corresponding functional modules are designed. The linearity, sensitivity, resolution, cross-talk and hysteresis are tested and analyzed. A low frequency vibration test system of probe using the precision PZT is constructed. The response to low frequency vibration signal is observed, and stability of performance is analyzed.5. Through feedbacking output signal of probe into NMM, movement control of NMM is achieved. Using the metrological function of NMM, dimension measurement with high precision is realized. By analysis of line scan and topographical scan, the scanning performance is studied. Finally, the errors induced by gravity of stylus, magnetic force, shift of stylus and vibration of environment are discussed.