Electron beam direct writing technology for fine gate patterning

Electron beam (EB) lithography along with photo lithography is a good candidate for fabricating fine patterns smaller than 200 nm. We examined the pattern fidelity which was one of the most important points for applying EB lithography for proto-typing ULSIs. We used a direct writing EB system with a shaped beam (HL-800D, Vacc: 50 kV, J: 10 A/cm2, Hitachi). In this paper, We applied EB direct writing (EB/DW) for the gate fabrication of 250-nm CMOS devices (Lg: 200 nm). The fidelity in resist patterns was 55 nm (range). The deviation was 21 nm (range), and the variation was 17 nm. We also applied EB/DW and i-line exposure for the gate fabrication of 350-nm CMOS devices (Lg: 350 nm), and measured the source-drain current (Ids) in nMOS transistors. We compared the Lg fluctuations which were calculated by Ids fluctuations. The magnitude of the fluctuations around Lg =350 nm with EBIDW was less than half of that with i-line. According to these results, EB lithography is very effective for fabricating very fine gates of ULSIs