Geometry impact on ultrahigh resolution pattern collapse

Abstract

Pattern collapse is one critical issue that lithography must overcome to address future high resolution nodes (32 and 22nm). Published pattern collapse models showed that lines collapse when the capillary pressure exerted by the liquid overcomes the mechanical strength of the material. To simplify equations, those models consider that the maximum capillary pressure is exerted only on one side of the pattern, when the rinse liquid fills the space on one side of the pattern while no liquid remains on the other side. The collapsing behavior of 60nm dense lines printed with extreme ultraviolet interferometric lithography (EUV-IL) and electron beam lithography (EBL) has been studied. These experiments confirm that this phenomenon can be correctly modeled with an asymmetric rinse liquid filling configuration. Then the influence of the pattern shape of sub-60-nm dense lines on collapse behavior is checked. The authors demonstrate that reentering slope deteriorates the pattern holding, whereas top rounding improves it. Finally, they observe that exposure defaults due to the tool properties such as stitching (EBL) or exposure dose heterogeneity (EUV-IL) considerably influence pattern collapse and should be considered for a better prediction.