FABRICATION OF 5-7 NM WIDE ETCHED LINES IN SILICON USING 100 KEV ELECTRON-BEAM LITHOGRAPHY AND POLYMETHYLMETHACRYLATE RESIST

The present limit of around 10 nm for the width of lines fabricated by e-beam lithography using polymethylmethacrylate (PMMA) resist on silicon substrates has been overcome. 5-7 nm wide etched lines in bulk Si substrates have been produced. A 65 nm thick layer of PMMA was exposed with an 80 kV electron beam of diameter smaller than 5 mum. After exposure the resist was developed in 3:7 cellosolve:methanol with ultrasonic agitation. The pattern in resist was transferred to the Si substrate with reactive ion etching. Lines of width varying between 5 and 7 nm were recorded using an S-900 scanning electron microscope which has a resolution of 0.7 nm.