High-resolution and high-precision pattern placement metrology for the 45 nm node and beyond

Abstract:
In order for the lithography world to continue on its path to ever smaller features, process solutions such as OPC assist features and double patterning / exposure strategies put more and more focus on the quality of photomasks. The community roadmap requires for the 45nm/32nm node nominal mask features of 120 nm and 85 nm, respectively. Small feature sizes in combination with tight overlay budgets of only 4.8 nm or even 3.4 nm for the 32 nm node illustrate the need for a registration metrology tool with high resolving power and yet unprecedented specifications on reproducibility and accuracy. Carl Zeiss reports on the concept and the project timeline of its new registration tool currently under development. Novel concepts such as the high resolution at-wavelength imaging optics, an integrated full-field autofocus system, and a correlation algorithm for image analysis are presented as examples for the innovative approach to achieve the very demanding goal.