Advanced lithography became possible using breakthrough technologies, including phase shift masks, advanced illumination modes, aggressive OPC patterns and 193nm immersion optics. The Applied Materials Aera193 system, an at-wavelength aerial reticle inspection tool, was introduced for the 90-65nm technology nodes. In the era of immersion lithography and 55-45nm nodes, there is an increasing demand for Aerial inspection under immersion conditions. To face this demand, the Aera193i was upgraded with expanded illumination and collection optics to support up to 1.4 NA immersion conditions. Here, we describe novel Aerial inspection results under immersion conditions. We studied the detection of a variety of defect types on 55nm node phase shift masks for immersion lithography. We found that the immersion-emulation inspection was able to demonstrate a good detection line, with extremely low false alarms and nuisance call rate. We also studied the relationship between Aerial defect detection and actual defect printability by printing the same mask on wafer. We found good correlation between Aera193i detection line and actual defect printability. We also address the polarization effects under immersion NA. We demonstrate that under polarized stepper illumination the polarization effects on the image are negligible, while aerial imaging reliably emulates mask pattern polarization effects.

Date Published: 5 April 2007
PDF: 11 pages
Proc. SPIE 6518, Metrology, Inspection, and Process Control for Microlithography XXI, 65183G (5 April 2007); doi: 10.1117/12.713947

Published in SPIE Proceedings Vol. 6518:
Metrology, Inspection, and Process Control for Microlithography XXI
Chas N. Archie, Editor(s)