EUV OPC for 56 nm Metal Pitch

For the logic generations of the 15 nm node and beyond, the printing of pitches at 64 nm and below are needed. For EUV lithography to replace ArF-based multi-exposure techniques, it is required to print these patterns in a single exposure process. The k(1) factor is roughly 0.6 for 64 nm pitch at an NA of 0.25, and k(1) similar or equal to 0.52 for 56 nm pitch. These k(1) numbers are of the same order at which model based OPC was introduced in KrF and ArF lithography a decade or so earlier. While we have done earlier work that used model-based OPC for the 22 nm node test devices using EUV,(1) we used a simple threshold model without further resist model calibration. For 64 nm pitch at an NA of 0.25, the OPC becomes more important, and at 56 nm pitch it becomes critical. For 15 nm node lithography, we resort to a full resist model calibration using tools that were adapted from conventional optical lithography. We use a straight shrink 22 nm test layout to assess post-OPC printability of a metal layer at pitches at 64 nm and 56 nm, and we use this information to correct test layouts.