Raman-based mapping and depth-profiling of the relaxation state in amorphous silicon

Our RIMA system has recently played an important role in a collaboration study between researchers from UdeM and Ecole Polytechnique de Montreal.

The research demonstrates how RIMA, Photon etc.'s Raman mapping system, can rapidly identify variations in the relaxation state of stress patterned a-Si over large areas (133 μm × 133 μm) up to the limit of diffraction. Large area Raman imaging combined with confocal μ-Raman which provides depth profile analysis of the relaxation state sheds a new light on the properties of a-Si at the microscale and could also be exploited to map other material properties.

Abstract: We show that the micro-scale variations in the relaxation state of amorphous silicon (a-Si) can be well-identified by Raman mapping over hundreds or thousands of μm² in 1–2 h. Pure and relaxed a-Si is obtained by self-implantation in crystalline silicon (c-Si) followed by anneal at 500 °C. It is then locally re-implanted over micro-sized patterns to produce unrelaxed a-Si zones. Raman mappings are obtained by pointwise confocal μ-Raman and hyperspectral Raman imaging. We also measure the depth profiles of the relaxation state in re-implanted a-Si by scanning the edge of a re-implanted sample. We infer from the depth profiles that the minimal damage dose to fully de-relax a-Si is 0.04 displacements per atoms, which is an order of magnitude smaller than the fluence needed to fully amorphize c-Si.