Managing effects in CD control from PED and PEB in advanced DUV photomask manufacturing using FEP-171 resist

Abstract

A continuing improvement in resist process is a necessity for high-end photomask fabrication. In advanced chemically amplified resist systems the lithographic performance is strongly influenced by diffusion of acid and acid quencher (i.e. bases). Beside the resist properties, e.g. size and volatility of the photoacid, the process conditions play important roles for the diffusion control. Understanding and managing these properties influences lithographic characteristics on the photomask such as CD uniformity, CD and pitch linearity, resolution, substrate contamination, clear-dark bias and iso-dense bias. In this paper we have investigated effects on the lithographic characteristics with respect to post exposure bake conditions, when using the chemically amplified resist FEP-171. We used commercially available mask blanks from the Hoya Mask Blank Division with NTAR7 chrome and an optimized resist thickness for the 248 nm laser tool at 3200Å. The photomasks were exposed on the optical DUV (248nm) Sigma7300 pattern generator.Additionally, we investigated the image stability between exposure and post exposure bake. Unlike in wafer fabrication, photomask writing requires several hours, making the resist susceptible to image blur and acid latent image degradation.

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

“…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.…”

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

“…The recent introduction of high-productivity DUV laser mask writers has been facilitated by a relatively straight forward adaptability to the standard materials and processes used for 50 keV VSB. This adaptation has been described for binary masks in a series of papers [1][2][3] for the SLM-based DUV (248 nm) Sigma7300 mask writer [4][5], papers that have also suggested possible optimizations of the materials and processes for the Sigma7300. An overview of the Sigma7300 process papers is found in Table 1.…”