Strain analysis in Si micro-electromechanical systems by dynamical X-ray diffraction

Long-range strain in nearly perfect crystalline materials can be detected by dynamical X-ray diffraction. Long-range strain due to uniform bending or torsion is undetectable by conventional methods when the specimen is vertical in a symmetrical Laue setting, but it can be detected by rotating the specimen along the scattering vector. This method is applied to Si devices for a resonating torsion mirror in a micro-electromechanical system. X-ray transmission topography clearly reveals local strain concentrations as enhancements or reductions in the diffraction intensity where non-uniform strain exists. In conjunction with reflection plane-wave topography, a model of local strain is proposed and the strain qualitatively analysed.