Pattern Roughness Mitigation of 22 nm Lines and Spaces: The Impact of a H2 Plasma Treatment

As the semiconductor industry pursues Moore's law, the demand to obtain smaller features continues. Extreme ultraviolet (EUV) lithography remains one of the primary options for sub-20 nm patterns. However, the technology struggles to meet the line width roughness (LWR) specifications. In this article, we present the significance of plasma treatment as a roughness smoothing technique. Two EUV photoresists with 22 nm lines are exposed to various plasma processes. We highlight the advantages of a hydrogen plasma treatment and its vacuum ultraviolet (VUV) emission as an optimal smoothing process and discuss the effect of photoresist thickness, initial LWR and the VUV plasma emission. Even though a H2 plasma treatment results in a successful reduction of LWR/LER, the target value of below 2nm is not yet achieved.