Photomask contamination inspections, whether performed at maskshops as an outgoing inspection or at wafer fabs for incoming shipping and handling or progressive defect monitoring, have been performed by KLA-Tencor STARlight systems for a number of design nodes. STARlight has evolved since it first appeared on the 3xx generation of KLA-Tencor mask inspection tools. It was improved with the TeraStar (also known as SLF) based tools with the SL1 algorithm. SL2 first appeared on the TeraScan systems (also known as 5xx) and has been widely adopted in both mask shops and wafer fabs. Design rules continue to advance as do inspection challenges. Advances in computer processing power have enabled more complex and powerful algorithms to be developed and applied to the STARlight technology. The current generation of STARlight, which is known as SL2+, implements improved modeling fidelity as well as a completely new paradigm to the existing STARlight technology known as HiRes5, or simply "H5". H5 is integrated seamlessly within SL2+ and provides die-to-die-like performance in both transmitted and reflected light, in addition to the STARlight detection, in unit time. It achieves this by automatically identifying repeating structures in both X and Y directions and applying image alignment and difference threshold. A leading mask shop partnered with KLA-Tencor in order to evaluate SL2+ at its facility. SL2+ demonstrated a high level of sensitivity on all test reticles, with good inspectability on advanced production reticles. High sensitivity settings were used for 45 nm HP and smaller design rule masks and low false detections were achieved. H5 provided additional sensitivity on production plates, demonstrating the ability to extend the use of SL2+ to cover 32 nm DR plate inspections. This paper reports the findings and results of this evaluation.

Date Published: 17 October 2008
PDF: 7 pages
Proc. SPIE 7122, Photomask Technology 2008, 71223N (17 October 2008); doi: 10.1117/12.802333

Published in SPIE Proceedings Vol. 7122:
Photomask Technology 2008
Hiroichi Kawahira; Larry S. Zurbrick, Editor(s)