Raman measurement of stress distribution in multicrystalline silicon materials

Micro-Raman spectroscopy was used to assess the spatial distribution of stress in multicrystalline silicon (mc-Si). Changes in the Raman peak position of about 0.1 wavenumbers on a length of several micrometers were detected between the grains and around the grain boundaries. These changes correspond to stress variations of about 50 MPa. Since the shifts caused by the stress are comparably small a careful analysis of the factors, influencing the measurement is necessary. Three major restrictions of the technique have to be considered: (i) the laser power should not cause significant local heating; (ii) the integration time should be large enough to resolve the signal with sufficient accuracy; (iii) the sample surface should be kept at the focus of the probe beam.