Raman Spectroscopy of Laser Induced Material Alterations

Raman spectroscopy is a powerful tool for material characterisation. It can be used for the optical characterisation of mechanical stress in homogeneous samples, for material identification, and for compositional mapping. In addition, confocal Raman microscopy is useful for the measurement of stress fields generated, for example, by mechanical loading or residual stress after fabrication in silicon and silicon carbide. For precise stress measurements, the thermally induced shift of Raman peaks must be characterised in detail. In addition to external heating, the measurement itself may affect the sample temperature because the focused, intense light can locally heat the sample. Local heating must be taken into account to ensure reliable stress measurements, for example in silicon micro-structures. This information is important for optimising manufacturing processes and increasing the reliability of micro devices. Raman spectroscopy can also be used for compositional mapping of heterogeneous specimens or for the characterisation of material alterations, which can also be caused by the excitation laser itself.