Interest in chemically amplified (CA) resist systems has been increasing for advanced mask fabrication due to their superior e-beam sensitivity, contrast and resolution compared to traditional non-CA e-beam resists on high kV (50-100kV) exposure systems. However, most CA resists available are sensitive to temperature variations during the post apply and/or post exposure (PAB/PEB) process steps. This temperature sensitivity can result in poor CD uniformity across the mask. An advanced positive tone CA resist developed at IBM, KRS-XE, has been investigated for use in the fabrication of NGL masks (the continuous membrane and stencil versions of electron projection lithography as well as proximity x-ray masks). KRS-XE is an improved ketal resist system that is robust towards airborne contaminants, is compatible with 0.263N TMAH aqueous developer and has a wide PAB/PEB process latitude. This CA resist has been found to be insensitive with respect to dose and CD over a PAB temperature range of 105°C to 120°C and a PEB temperature range from room temperature to 110°C. Line/space features down to 75nm have been demonstrated in this resist on the IBM EL4+ 75kV vector scan e-beam system. This paper discusses the performance of KRS-XE with respect to CD uniformity on NGL membrane masks and compares the experimentally obtained results from both KRS-XE and a PEB sensitive CA resist (Shipley UVIII™) against the PEB temperature variations predicted from a finite difference model for each mask format.

Date Published: 22 January 2001
PDF: 10 pages
Proc. SPIE 4186, 20th Annual BACUS Symposium on Photomask Technology, (22 January 2001); doi: 10.1117/12.410750

Published in SPIE Proceedings Vol. 4186:
20th Annual BACUS Symposium on Photomask Technology
Brian J. Grenon; Giang T. Dao, Editor(s)