Optimizing dual-function underlayers for minimal defectivity of directed self-assembly rectified extreme ultraviolet lithography patterns

초록

Background: Complementing extreme ultraviolet (EUV) lithography with directed self-assembly (DSA) of block copolymers is a potential technology solution to overcome stochastic pattern variability. In the EUV + DSA process flow, the underlayer serves two functions. First, it should provide adequate adhesion with the EUV resist to prevent collapse of high-aspect ratio features. Second, after chemical conversion, the underlayer constitutes a chemo-epitaxial guide pattern for directing the block copolymers. Aim: To optimize the defectivity of EUV + DSA patterns, the impact of the underlayer’s surface properties, specifically its surface energy, on resist collapse and DSA performance should be characterized. Approach: Using a series of underlayers with varying surface energies, the dual functionality is characterized by means of the W 3 metric and the chemical contrast of the guide pattern. Results: It is found that the W 3 metric can adequately predict the likelihood of resist pattern collapse. Furthermore, an inverse correlation is observed between the guide pattern contrast and the after etching bridge defect density of a pitch 28-nm line/ space DSA pattern. Conclusions: The underlayers with lower polar component of the surface energy exhibited better collapse margin as well as lower defectivity after DSA rectification.

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