Strain Engineering for Germanium-on-Insulator Mobility Enhancement with Phase Change Liner Stressors

We investigate the strain in various Ge-on-insulator (GeOI) micro-structures induced by three phase-change materials (PCMs) (Ge_2Sb_2Te_5, Sb_2Te_3, GeTe) deposited. The PCMs could change the phase from amorphous state to polycrystalline state with a low temperature thermal annealing, resulting in an intrinsic contraction in the PCM films. Raman spectroscopy analysis is performed to compare the strain induced in the GeOI micro-structures by various PCMs. By comparison, Sb_2Te_3 could induce the largest amount of tensile strain in the GeOI micro-structures after the low temperature annealing. Based on the strain calculated from the Raman peak shifts, finite element numerical simulation is performed to calculate the strain-induced electron mobility enhancement for Ge n-MOSFETs with PCM liner stressors. With the adoption of Sb_2Te_3 liner stressor, 22% electron mobility enhancement at N_\rm inv=1\times10^13 cm^-2 could be achieved, suggesting that PCM especially Sb_2Te_3 liner stressor is a promising technique for the performance enhancement of Ge MOSFETs.