Ultrathin (5 nm) SiGe-On-Insulator with high compressive strain (−2 GPa): From fabrication (Ge enrichment process) to in-depth characterizations

Abstract

300mm ultrathin Silicon-On-Insulator (SOI) wafers with SiGe/Si stacks on top were used as pre-structures for the fabrication of 5nm thick SiGe-On-Insulator (SGOI) substrates obtained by the Ge enrichment technique. Those substrates will be used as the channel of advanced Fully Depleted (FD) p-type Metal Oxide Semiconductor Field Effect Transistors (pMOSFET). We present in the first part the successful fabrication of 5nm SGOI wafers. Various characterization techniques are used to investigate the Ge profile and the final strain in the fabricated 5nm Si0.7Ge0.3 film. Secondary Ions Mass Spectrometry (SIMS) and Scanning Transmission Electron Microscopy (STEM) clearly show that the Ge content is very homogeneous (xGe=30±1%) in the SiGe layer. Raman spectroscopy and High Angle Annular Dark Field (HAADF) STEM both confirm that the 5nm thick SiGe film is compressively strained (−2GPa). The second part is dedicated to the sensitivity of the Ge enrichment process (based on numerical modelling). We investigate the impact of single and combined fluctuations of the pre-structure parameters (TSi, TSiGe,0, xGe,0) on the final SiGe layer (TSiGe, xGe).