Evaluation of Si thin film formed from Si0.7Ge0.3/Si/Si0.7Ge0.3-stacked layers with CF4/H2 plasma for Si-nanosheet formation toward GAA transistor application

We investigated the influence of selective SiGe etching process condition using CF4/H2 plasma on defect formation in the Si layer. Total photoelectron yield spectroscopy and conductive-atomic force microscopy measurements revealed that the H2-dilution ratio significantly affected defect formation. In particular, defect formation was effectively suppressed, and uniform electron transport in the Si layer was achieved after the etching of Si0.7Ge0.3 with CF4/H2 plasma at 5% H2 dilution. Furthermore, we successfully demonstrated the formation of an ultrathin Si-nanosheet (Si-NS) using CF4/H2 plasma at 5% H2 dilution and evaluated the local electron-transport properties to investigate surface defect uniformity in the Si-NS. These results will lead to the development of highly reliable gate-all-around Si-NS field-effect transistors through an all-dry process.