Practical LWR sampling approaches for advanced patterning

CD variation and more specifically, the line edge roughness (LER), on features now dominates the edge placement error (EPE) and can even exceed the overlay error component of EPE as we scale to more advanced process nodes. A method to accurately differentiate between patterning options is required at these dimensions. The measurements must be accurate and not be influenced by the measurement technique or equipment. EUV lithography and the scaling of the dimensions has brought a greater importance to the effects of linewidth roughness (LWR) in device performance. Lithographers today have to spend considerable amounts of time to measure these irregularities coming from stochastic effects as well as chemical reactions, in order to accurately quantify the patterning effects whilst maintaining cost-effectiveness in manufacturing. In this paper we examine usage of unbiased LWR measurements for EUV direct-print patterning of 32nm, 36nm and 72nm pitch gratings to help instruct the proper choice of materials for photolithography, etch process optimization, illumination source selection as well as improved matching of scanner equipment.