Holistic CD metrology for process control of directed self-assembly

Toward 1x nm and beyond, some candidate lithography tools have been proposed as shown in Fig. 1. We believe multi-patterning with argon fluoride (ArF) immersion lithography will be used and subsequently replaced by extreme ultraviolet (EUV) lithography. This mainstream scenario, however, may have some risks. In regard to multi-patterning, cost is an issue because a number of process steps and two or more reticles are required for each layer. And in regard to EUV lithography, there are still some critical issues to be solved (e.g. light source, resist sensitivity, line edge roughness, and tool cost). Taking into account the worst case scenario, lithographers should prepare alternative approaches for patterning down to 1x nm.