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20 October 2006 Process window enhancement for 45-nm node using alterable transmission phase-shifting materials
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A case study was carried out investigating the influence of different transmission and phase shift materials on lithographic performance at 45 nm node. The bilayer approach for embedded attenuated Phase Shift Masks (EAPSM) offers the advantages to adjust phase shift and transmission independently. The transmission of Ta/SiO2 can be tuned up to 40% depending on the required application. Three different PSM blank types with the stacks Ta/SiO2-6%, Ta/SiO2-30% and Ta/SiON-30% have been manufactured and characterized. Afterwards, an identical line pattern, consisting of different feature sizes and duty cycles, has been patterned in each of the three PSM types as well as in the MoSi-6% for reference. Using the AIMSTM 45-193i tool we have evaluated the lithographic performance of the four PSM in terms of contrast and process latitude using unpolarized and TE polarized illumination. The case study showed that the process window for Ta/SiO2-6% is comparable to standard MoSi-6%. For dense line application a 6% EAPSM is preferable. The Ta/SiO2-30% EAPSM provides a significantly larger process window for higher duty cycles compared to MoSi-6%. This means a 50% increase in depth of focus (DOF) at 10% exposure latitude (EL). Therefore for logic application with higher duty cycles a EAPSM material with 30% transmission is preferable.
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Hans Becker, Markus Renno, Guenter Hess, Ute Buttgereit, Corinna Koepernik, Lorenz Nedelmann, Mathias Irmscher, Robert Birkner, Axel Zibold, and Thomas Scheruebl "Process window enhancement for 45-nm node using alterable transmission phase-shifting materials", Proc. SPIE 6349, Photomask Technology 2006, 63490J (20 October 2006);

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