Focused ion beam (FIB) nano-machining and FIB Moire technique for strain analysis in MEMS/NEMS structures and devices

The accurate determination of residual strain/stress in thin films is especially important in the emerging field of MEMS/NEMS. In this paper, a focused ion beam (FIB) Moire method is proposed and demonstrated to measure residual strain/stress in microstructures. This technique is based on advantages of the FIB system in nano-machining, in-situ deposition, imaging, and fine adjustment. A nano-grating is directly written on the top of the microstructures by ion milling without any etch mask; the FIB Moire pattern is formed by the interference between a prepared specimen grating and raster scan lines. Since the local strain of a microstructure itself can be monitored during the process, the FIB Moire technique has many potential applications in the mechanical metrology of MEMS.