Non-linear Raman shift-stress behavior in top-down fabricated highly strained silicon nanowires

Abstract

Strain engineering is a key technology to continue Moore's law with silicon or any other foreseen semiconductor in very large scale integration. The characterization of strain in nanostructures is important to determine the potential of these technologies, and it is typically performed using micro-Raman when investigating strained silicon. Here, we report on the Raman shift-stress behavior from the (001) silicon surface of highly strained ultra-thin (15 nm-thick) suspended nanowires with stresses in the range of 0–6.3 GPa along the [110] direction. We employ a strain technology that offers a precise control of stress values at large sampling while reducing variability. The stress level of the nanostructures has been accurately evaluated by the finite element method simulations and further correlated to the Raman spectra. For stresses below 4.5 GPa, the aforementioned behavior was linear and the extracted stress shift coefficient was in agreement with those reported in the literature. For stresses greater than 4.5 GPa, we show that the Raman shift-stress behavior resembles a quadratic function.