Layout pattern density impacts mask critical dimension uniformity (MCDU) as well as wafer critical dimension uniformity (WCDU) performances in some aspects. In patterning the dense contact array with negative tone development (NTD) process, the abrupt pattern density change around the array edge of a NTD clear tone reticle arises as a very challenging issue for achieving satisfactory WCDU. Around the array boundary, apart from the MCDU greatly impacted by the abrupt pattern density change, WCDU in lithographic process is also significantly influenced by the optical flare and chemical flare effects. This study investigates the pattern density effect induced MCDU and WCDU variations. Various pattern densities are generated by the combination of fixed array pattern and various sub-resolution assist feature (SRAF) extension regions for quantifying the separated WCD variation budget contributed by MCD variation, chemical flare effect and optical flare effect. With the proper pattern density modulation outside the array pattern on a clear tone reticle, MCD variation across array can be eliminated, optical flare and chemical flare effects induced WCD variation is also greatly suppressed.

Date Published: 19 March 2015
PDF: 10 pages
Proc. SPIE 9424, Metrology, Inspection, and Process Control for Microlithography XXIX, 94242J (19 March 2015); doi: 10.1117/12.2083674

Published in SPIE Proceedings Vol. 9424:
Metrology, Inspection, and Process Control for Microlithography XXIX
Jason P. Cain; Martha I. Sanchez, Editor(s)