Two-dimensional imaging of crystal phase and stress component by micro-Raman spectroscope equipped with integral field unit

Abstract

Micro-Raman spectroscopy is used to measure phases, stresses and strains in microstructures comprising semiconductor materials, such as Si. However, the two-dimensional Raman imaging techniques for directly observing phases and measuring stresses and strains in a large area are required. In this study, we develop a new micro-Raman spectroscope equipped with an integral field unit (IFU) for two-dimensional imaging. Two-dimensional Raman images are obtained without scanning laser spots and stages. In addition to the IFU, this instrument primarily comprises an illumination optical system. In the illumination optical system, a diffractive optical element is used to enlarge the area of the laser spot and transform the circular laser beam into a square beam. The IFU simultaneously collects two-dimensional Raman signals using a microlens array, 4 × 4 optical fiber bundle, two-dimensional imaging spectrometer, and highly sensitive two-dimensional charge-coupled device (CCD) detector. Subsequently, we conduct two-dimensional imaging of the Si phase and residual stress components of the (111)-oriented single-crystal Si wafer induced by Vickers indentation. The Raman spectra are measured under polarization conditions to decompose the triple degeneracy of Si, and the residual stress components around Vickers indentation are calculated from the relations between the Raman shift and applied strain.