Defect printability analysis in negative tone development lithography

In general, contact hole patterning has various challenges such as narrow process window, large mask error enhancement factor (MEEF), poor circularity, and low image contrast compared to line & space patterning. For that reason, it is difficult to make sub-50nm size contact hole with 193nm ArF immersion single exposure. In order to achieve sub-40nm contact hole patterning, we have need of shrink bias over 20nm. However, conventional pattern shrink technology such as resist reflow process is difficult to get shrink bias over 20nm because the shrink volume gets smaller as the pitch gets narrower. Recently several authors have specifically noted the advantages of using negative tone development for patterning narrow trenches. A new negative tone imaging with application of new developer to conventional ArF immersion resist materials is proposed for small contact hole pattern formation. Significantly better LWR and resolution on small contact hole pattern were observed with this negative tone development compared with positive tone development. In this paper, we will introduce the experimental results of sub-40nm contact hole patterning using negative tone systems for contact hole patterning. We will report the results of comprehensive studies of defects originating in negative tone photolithography and reveal the defect generation mechanism of each negative tone imaging-specific defect types.