Stress mapping in silicon: Advantages of using a Raman spectrometer with a single dispersive stage

Stress is a major concern in microelectronic circuit production and Raman spectroscopy has proved to be an outstanding method for mapping it in silicon. In the literature, a configuration with two or three spectral dispersive stages is usually employed. By using a Raman spectrometer with a single dispersive stage, however, it is possible to have higher collection efficiency, resulting in fast acquisition and high stability of the system. Although the nominal spectral resolution of such a system is approximately 2 cm-1, we have found that the sensitivity to stress is less than 50 MPa, comparable to other systems with more dispersive stages. For low stress values, less than 100 MPa, the Raman measurements can be affected by the patterning of the sample itself, especially if laser plasma lines are used for spectral calibration. It will be shown that the use of a Raman microscope with a single dispersive stage, enabling simultaneous collection of Stokes and anti-Stokes components, provides a feedback for the reliability of the experiment.