Strain in Si or Ge from the Edge Forces of Epitaxial Nanostructures

The introduction of strain in semiconductors is a well-known technique exploited in microelectronics to increase their mobility and thus to enhance the performance of silicon-based electronic devices. Moreover, tensile strain is one feasible route towards converting Ge into an efficient light emitter. Here we show how the application of local strain via nanopatterning opens a wider parameter space for strain engineering in semiconductors of the Si/Ge material system. The general approach relies on the top-down fabrication of SiGe stressors realized by electron-beam lithography (EBL) and reactive-ion etching (RIE). Specifically, compressive strain can be locally applied to pure Si and tensile strain can be applied to pure Ge. Raman spectroscopy is used to investigate the strain induced in Si or Ge bulk like substrates. Furthermore, the realization of stressors on micro-bridges demonstrates higher achievable strain level if compared to the attached bulk-like case. The strain enhancement is due to the high sharing of elastic energy in between the nanostructures and the bridges. The SiGe stressor approach hence presents a CMOS compatible alternative for strain creation in Si, Ge and SiGe.