Sub-10-nm Electron Beam Lithography Using a Poly(α-methylstyrene) Resist with a Molecular Weight of 650

Only the 7 nm patterning has been achieved by using an organic negative electron beam (EB) resist, poly(α-methylstyrene) resist with a molecular weight of 650 (αMST650). An αMST650 resist film can be prepared by a conventional spin-coating technique and its surface roughness is smooth, with peak-to-valley roughness of less than 1.5 nm. Although the sensitivity of αMST650 is very low, 30 mC/cm2, high-resolution patterns of 15 nm width and 25 nm pitch with no scum have been fabricated using a 50 kV electron beam of about 7 nm diameter. The etching selectivity between Si and αMST650 is about 2.3 and the etching durability of αMST650 is superior to thouse of calixarene resist and polystyrene resist. The minimum line pattern sizes achievable with αMST650 resist is 7 nm, although the minimum line pattern size of polystyrene with a molecular weight of 1100 is about 12 nm. The pattern size dependence of resist resin molecular weight exit in beyond resist molecular weight of 650.