Full-field exposure performance of electron projection lithography tool

Electron projection lithography (EPL) is a realistic technology for the 65 nm node and below, as a complementary technology of optical lithography especially for contacts and gate layers because of its high resolution and large process margin. Nikon has developed an EPL exposure tool as an electron-beam (EB) stepper and the first generation EB stepper; NSR-EB1A is now almost completed as an R&D tool for the 65 nm technology node. Using a ϕ 200 mm reticle, a 20 mm × 25 mm exposure field is realized. Full-field exposure performance of NSR-EB1A is shown. A 70 nm isolated line and 1:1 nested lines are simultaneously resolved, as are 50 nm 1:2 nested lines. 60 nm contact holes are resolved with a depth of focus over a 10 μ m range and dosage window over ± 6 % . Stitching accuracy is about 20 nm ( 3 σ ) and the single machine overlay is about 30 nm (mean + 3 σ ) . These data mean sufficient performance for device manufacturing of the 65 nm technology node. The concept of a large subfield is one candidate for resolution and throughput enhancement in EPL production tool. The Coulomb blur is directly measured by an aerial image sensor for a large subfield and small beam half-angle, and the data show good agreement with simulations. It is shown that throughput over 20 wafers per hour ( ϕ 300 mm ) is realistic and achievable in a production tool of a 45 nm technology node.