Actinic inspection of multilayer defects on EUV masks
The production of defect-free mask blanks, and the development of techniques for inspecting and qualifying EUV mask blanks, remains a key challenge for EUV lithography. In order to ensure a reliable s...
Line width variation with absorber thickness in extreme ultraviolet lithography
Selectivity of extreme ultra-violet lithography mask's material and thickness significantly influences on pattern formation. Since the reflectance changes periodically depending on absorber thickness,...
Proc. SPIE, Vol. 5751, 660 (2005);
doi:10.1117/12.598559
Online Publication Date: 13 May 2005
Conference Date: Thursday 03 March 2005
Conference Location: San Jose, CA, USA
Conference Title: Emerging Lithographic Technologies IX
Conference Chairs: R. Scott Mackay
Toqualify the performance of non-actinic inspection tools, a novel EUVmask inspection system has been installed at the Advanced LightSource (ALS) synchrotron facility at Lawrence Berkeley National Laboratory. Similarto the older generation actinic mask inspection tool1, the newsystem can operate in scanning mode, when mask blanks arescanned for defects using 13.5-nm in-band radiation to identify andmap all locations on the mask that scatter a significantamount of EUV light. By modifying and optimizing beamline optics(11.3.2 at ALS) and replacing K-B focusing mirrors with ahigh quality Schwarzschild illuminator, the new system achieves an orderof magnitude improvement on in-band EUV flux density at themask, enabling faster scanning speed and higher sensitivity to smallerdefects. Moreover, the system can also operate in imaging mode,when it becomes a zone-plate-based full-field EUV microscope with spatialresolution better than 100 nm. The microscope utilizes an off-axissetup, making it possible to obtain bright field images overa field-of-view of 5x5 um2.
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