Micro-Raman measurement of strain in silicon nanowires

Abstract

Crystalline nanostructures such as silicon nanowires (SiNWs) may have residual mechanical stress and strain from the fabrication process, which can potentially impair their reliability as building blocks of Microelectromechanical system (MEMS). The amount of strain may be minuscule, which requires very accurate measurements to determine the strain. Micro-Raman spectroscopy is a work horse tool since it is a simple, fast and nondestructive technique that can be used to assess mechanical strain. However, a precise evaluation of residual strain for nanostructures using micro-Raman spectroscopy requires careful calibrations and theoretical calculations. This thesis describes the interrelations between Raman shift and strain in fabricated silicon nanowires. The calibration methods are used to eliminate the two dominant errors: errors in focusing, and laser heating effects, which can lead to apparent Raman shifts. Finally, the Raman measurement results are discussed and the corresponding residual strain in the [110] direction is calculated. This work is concluded with the discussion of possible causes of strain.