20-nm Resolution of electron lithography for the nano-devices on ultrathin SOI film

We have investigated the ultimate resolution of e-beam lithography with PMMA resist (MW=1 000 000 and 2 000 000) in-situ during single-electron transistor (SET) formation by means of using an e-beam diameter 5 nm and electron energy 22 keV. The pattern generator and software was from RAITH (PROXY). Writing structures had a minimim size of 40 nm. It was found that if PMMA is at MW=2 000 000, the silicon nanobridges with 15 nm width are available. We have made Ohmic contacts to SOI by Ti/Au evaporation. The resistivity of nanobridges did not change after wet etching in HF. The transistor-like effect was found on pure silicon nanobridges at room temperature in split in-plane gate geometry (IPGFET). The conductance of heavy boron-doped silicon nanobridges at T=4.2 K was investigated. Zero conductivity was found at drain voltage less than 50 mV.