Model based OPC for implant layer patterning considering wafer topography proximity (W3D) effects

Implant layer patterning is becoming challenging with node shrink due to decreasing critical dimension (CD) and usage of non-uniform reflective substrates without bottom anti-reflection coating (BARC). Conventional OPC models are calibrated on a uniform silicon substrate and the model does not consider any wafer topography proximity effects from sub-layers. So the existing planar OPC model cannot predict the sub-layer effects such as reflection and scattering of light from substrate and non-uniform interfaces. This is insufficient for layers without BARC, e.g., implant layer, as technology node shrinks. For 45-nm and larger nodes, the wafer topography proximity effects in implant layer have been ignored or compensated using rule based OPC. When the node reached 40 nm and below, the sub-layer effects cause undesired CD variation and resist profile change. Hence, it is necessary to model the wafer topography proximity effects accurately and compensate them by model based OPC. Rigorous models can calculate the wafer topography proximity effects quite accurately if well calibrated. However, the run time for model calibration and OPC compensation are long by rigorous models and they are not suitable for full chip applications. In this paper, we demonstrate an accurate and rapid method that considers wafer topography proximity effects using a kernel based model. We also demonstrate application of this model for full chip OPC on implant layers.