| Popis: |
As Critical Dimension (CD) sizes decrease for 32 nm node and beyond, resist loss increases and resist patterns become more vulnerable to etching failures. Traditional OPC models only consider 2D contours and neglect height variations. Rigorous resist simulators can simulate a 3D resist profile but they are not fast enough for correction or verification on a full chip. However, resist loss for positive tone resists is mainly driven by optical intensity variations which are accurately modeled by the optical portion of an OPC model. In this article, we show that a Calibre TM CM1 resist model can be used to determine resist loss by properly selecting the optical image plane for calibration. The model can then be used to identify toploss hotspots on a full chip and in some cases to correction of these patterns. In addition, the article will show how the model can be made more accurate by accounting for some 3D effects like diffusion through height. |
