An in situ platform for the investigation of Raman shift in micro-scale silicon structures as a function of mechanical stress and temperature increase

Abstract

Raman spectroscopy provides an accurate approach to measure temperature and stress in semiconductors at micro-scale and nano-scale. In the present work an in situ experimentation-based approach to separate a measured room to high temperature Raman shift signal into mechanical and thermal components when a uniaxial compressive load is applied in situ is presented. In situ uniaxial compressive loads were applied on examined silicon cantilever specimens from room temperature to 150 °C. The Raman shift measurements were performed as a function of strain at constant temperature and as a function of temperature at constant strain levels. The results show that the Raman shift measured at a given temperature under a given level of applied stress can be expressed as a summation of stress-induced Raman shift signal and temperature-induced Raman shift signal measured separately. For silicon, the stress-induced Raman shift is caused by inelastic interaction between the incident laser and the vibration of crystal lattice, while the temperature-induced Raman shift is caused by the anharmonic terms in the vibrational potential energy. Analyses indicate that such separation of Raman shift signal can be used to measure localized change in thermal conductivity and mechanical stress of semiconductor structures under applied stress.