Lithography performance of contact holes: II. Simulation of the effects of reticle corner rounding on wafer print performance

Pattern fidelity of contact features on the wafer is critical to the functionality of a device. Without good pattern fidelity of these features, interconnects between conductor layer may be unreliable, ultimately causing the device to fail. Among other error sources, the feature quality on the reticle is thought to be a key contributing factor to wafer contact pattern fidelity. In particular, the pattern generation tool used to exposure the reticle may be selected based on the maximum acceptable amount of corner rounding of a contact feature. Of course, optimization of contact layers is dependent on the exposure and process of both the mask and wafer, as well as on their relationship to one another. Understanding how reticle pattern fidelity affects the patterned image on the wafer helps to optimize both imaging processes. This paper examines the key parameters that contribute to wafer contact thole pattern fidelity through simulation. The impact of reticle corner rounding on the printed wafer result will be examined for conventional and attenuated phase shifting masks, dense and isolated contacts. Results from this work will be sued to predict the acceptable amount of corner rounding on the reticle, and to define a proper metric of reticle shape.