Sub-10-nm electron beam lithography using a poly(alpha-methylstyrene) resist with a molecular weight of 650

Only the 7 nm patterning has been achieved by using an organic negative ele ctron beam (EB) resist, poly(a-methylstyrene) resist with a molecular weigh t of 650 (alpha MST650). An alpha MST650 resist film can be prepared by a c onventional spin-coating technique and its surface roughness is smooth, wit h peak-to-valley roughness of less than 1.5 nm. Although the sensitivity of alpha MST650 is very low, 30 mC/cm(2), high-resolution patterns of 15 nm w idth and 25 nm pitch with no scum have been fabricated using a 50 kV electr on beam of about 7 nm diameter. The etching selectivity between Si and alph a MST650 is about 2.3 and the etching durability of alpha MST650 is superio r to thouse of calixarene resist and polystyrene resist. The minimum line p attern sizes achievable with alpha MST650 resist is 7 nm, although the mini mum line pattern size of polystyrene with a molecular weight of 1100 is abo ut 12 nm. The pattern size dependence of resist resin molecular weight exit in beyond resist molecular weight of 650.