Strain Determination Around Vickers Indentation on Silicon Surface by Raman Spectroscopy

Abstract

We used Raman spectroscopy to characterize indentations on silicon. We focused our attention on the strain field around several indentations made on an (001) oriented silicon wafer with loads ranging from 100 mN to 10 N. Micro-Raman spectroscopy was used for the analysis of the indentation strain field. By multiplying the frequency shift of the optical phonon of silicon by the distance from the center of the fingerprint to the point under investigation, we were able to determine the strained zone extension accurately with the boundary between the strained area and the unperturbed area, which becomes clearly visible. This method allowed us to propose an equation valid over a large range of loads (0.1–10 N), which allowed us to estimate the size of the strained zone. We show that even in the absence of visible defects, the strain field extended to a region relatively far from the imprint in between cracks. The analysis of the radial and lateral cracks gives information where the proposed equations are valid.