High performance FEP-171 resist process in combination with NTAR7 and NTAR5 chrome and the Sigma7300 DUV mask writer

Abstract

FEP-171 resist is commonly used both together with 50 keV VSB and DUV laser mask writers. To improve resolution and other lithographic parameters, the industry has strived towards thinner resist and absorber films on the mask blank. The chrome thickness and etch resistance limit how thin the resist can be. The NTAR7 (730Å) chrome was optimized for binary masks for 193 nm lithography, while NTAR5 (590Å) chrome is used for attenuated PSM blanks with a MoSi absorber beneath the chrome film.Resolution and lithographic performance can be improved further by integrating improved processes, including PEB, development and dry-etch. Micronic has in a series of papers described improvements to the FEP-171 process in combination with different chrome films and the SLM-based DUV (248 nm) Sigma7300 mask writer. The thickness of FEP-171 for Sigma7300 has been optimized for NTAR7 chrome and improvements have been described for the PEB and dry-etch process of the FEP-171/NTAR7 blanks.In this paper we describe the FEP-171 process development further. We have investigated improvements to the develop process for FEP-171/NTAR7 blanks using Design of Experiments (DOE) and a Steag Hamatech ASP-5000. Improved performance on mask, especially for CD linearity and clear-field/dark-field deviation, was achieved using the resulting development recipe together with the Sigma7300. Better than 5 nm (range) CD linearity in chrome was demonstrated for isolated spaces in the range 200-1400 nm.This work also covers a process study of FEP-171 on NTAR5 chrome. The resist thickness was optimized to 3200Å for the Sigma7300 and the performance was tested in terms of resolution, resist profile, CD linearity and CD uniformity. Resolution of 120 nm isolated lines and 140 nm isolated spaces was demonstrated, as well as 4 nm (range/2) global CD uniformity.

Evaluation of attenuated PSM photomask blanks with TF11 chrome and FEP-171 resist on a 248 nm DUV laser pattern generator

“…Previously, we have optimized the resist thickness and process for NTAR7 binary mask blanks 4 and NTAR5 att-PSM mask blanks 6 . Advancing to an att-PSM blank with TF11 chrome is motivated by improvements to the Sigma7500 that position it for the 65 nm and 45 nm nodes, where TF11 mask blanks are expected to be used 2 .…”

“…At Micronic, DUV mask process development has included advances in mask blanks [3][4][5][6] , from binary AR8, to NTAR7, to att-PSM NTAR5 and now TF11 chrome blanks, while in parallel the Sigma laser pattern generator was developed from the 90 nm node towards the 45 nm node. As a continuation of this mask process development, this paper reports on an experimental evaluation of the use of TF11 chrome and FEP-171 resist together with the Sigma7500 laser pattern generator.…”

“…The second step was to evaluate the global patterning performance using TF11 with two resist thicknesses, 2000 Å and 2550 Å. For comparison, the same global evaluation was made using NTAR5 with 3200 Å FEP-171 resist 6 .…”