Precise delineation characteristics of advanced electron beam mask writer EB-X3 for fabricating 1x X-ray masks

This paper discusses the delineation characteristics of a state-of-the-art variable-shaped electron-beam (e-beam) mask writer called the EB-X3, which was developed both to write 100-nm-node patterns on X-ray membrane masks an d also to study the feasibility of the mask technology. For a l-Gb dynamic random access memory (DRAM) pattern (22 mm x 22 mm chip), the best image pl acement (IP) accuracy obtained so far is 3 sigma (X, Y) = (5.6 nm, 8.4 nm) and maximum Delta (X, Y) = (4.2 nm, 7.3 nm). TP values less than IS nm are reproducible. Precise temperature control and a three-point support pallet (4-inch membrane warpage. <100 nm) are the keys to this excellent IF. A res olution of 50 nm was obtained for line-and-space patterns. Good critical di mension control of less than 10 nm and small proximity effects win obtained with ZEP resist and normal-hexyl acetate developer A total overlay accurac y for proximity X-ray lithography of better than 40 nm was achieved at the 1-Gb-DRAM level using X-ray masks with a 19-nm overlay accuracy (gate to co ntact) fabricated using the EB-X3.