No abstract

Owing to photon shot noise and inhomogeneous distribution of the molecular components in a chemically amplified resist, resist patterns defined by extreme ultraviolet (EUV) lithography tend to suffer from stochastic variations. These stochastic variations are becoming more severe as critical dimensions continue to scale down, and can thus be expected to be a major challenge for the future use of single exposure EUV lithography. Complementing EUV lithography with directed self-assembly (DSA) of block-copolymers provides an interesting opportunity to mitigate the variability related to EUV stochastics. In this work, the DSA rectification process at imec is described for both line/space (L/S) and hexagonal contact hole (HEXCH) patterns. The benefits that rectification can bring, as well as the challenges for further improvement are being addressed based on the current status of imec’s rectification process.

For printing the most critical features in semiconductor devices, single exposure extreme ultraviolet (EUV) lithography is quickly advancing as a replacement for ArF immersion-based multipatterning approaches. However, the transition from 193 nm to 13.5 nm light is severely limiting the number of photons produced by a given source power, leading to photon shot noise in EUV patterns. In addition, inhomogeneous distribution of components inside conventional photoresists is adding to the printing variability, especially when critical dimensions continue to shrink. As a result, stochastic issues leading to rough, non-uniform, and potentially defective patterns have become a major challenge for EUV lithography. A promising solution for this top-down patterning approach is complementing it with bottom-up directed self-assembly (DSA) of block copolymers. In combination with 193i lithography, DSA of lamellae forming block copolymers has previously shown favorable results for defining dense line-space patterns using LiNe flow.1 In this study, we investigate the complementarity of EUV + DSA for rectification of pitch 28 nm line-space patterns. Roughness and defectivity are critical factors that need to be controlled to make these patterns industrially relevant. We look at the impact of DSA material and processing parameters on line edge roughness and line width roughness in order to identify and mitigate the origins of pattern roughness. On the other hand, we also assess the different types of defect modes that are observed by means of optical defect inspection and ebeam review, and study the root causes for their formation. To wrap-up, the benefits of 1X DSA versus 3X DSA are presented by comparing EUV + DSA to LiNe flow.