Experimental validation of rigorous, 3D profile models for negative-tone develop resists

The extension of 193nm immersion lithography to the 14nm node and beyond directly encounters a significant reduction in image quality. One of the consequences is that the resist profile varies noticeably, impacting the already limited process window. Resist top-loss, top-rounding, T-top and footing all play significant roles in the subsequent etch process. Therefore, a reliable rigorous model with the capability to correctly predict resist 3D (R3D) profiles is acquiring higher importance. In this paper, we will present a calibrated rigorous model of a negative-tone develop resist. Resist profiles can be well simulated through focus and dose, and cases that match well to the experimental wafer data are validated. Such a model can not only provide early investigation of insights into process limitation and optimization, but can also complement existing OPC models to become R3D-aware in process development.