Process window discovery methodology for extreme ultraviolet (EUV) lithography

With the adoption of extreme ultraviolet (EUV) lithography in high volume manufacturing (HVM) to enable the sub-7nm scaling roadmap, defect characterization brings new challenges and learnings. Traditional approaches to process window discovery (PWD) methodology developed^2,3,4 using broadband plasma optical inspection also hold in the realm of EUV lithography. Although there is substantial depth of focus for regular patterns, focus continues to be an important modulation parameter for logic patterns. Dose is an important modulation parameter especially due to stochastic defects.¹ Further, overlay is another important parameter when it comes to hybrid integration schemes such as self-aligned quadruple patterning (SAQP) and EUV block patterning, for example, in BEOL layers. In this paper, we will discuss PWD results on a foundry N5 equivalent M2 layer, studying both SAQP and block integration with direct EUV patterning. We also demonstrate the impact of EUV stochastics to the overall process window and develop useful analysis methodologies.