Synthesis of Lithography Test Patterns Using Machine Learning Model

Diversity of test patterns is important for many lithography applications. It is however difficult to achieve with sample layouts or by using a popular pattern generator. We propose a synthesis method of lithography test patterns. Each pattern is represented by a map of IPS (image parameter space) values, called IPS map. A key in the proposed method is to guarantee that the center of the synthesized pattern corresponds to the IPS values given as input. The synthesis consists of three steps: a new IPS map is generated using an adversarial auto-encoder (AAE) with given IPS values; the IPS map is converted to its corresponding layout through an auto-encoder (AE); the layout goes through the final processing to remove any unrealistic shapes. Both AAE and AE are trained beforehand by using a few sample layouts. The synthesis method is applied to lithography modeling. The RMSE of lithography model is reduced by 30% when the model is calibrated with synthesized patterns, compared to the model based on test patterns from a pattern generator. A machine learning-based lithography simulation is taken as a second application. When the synthesized patterns are used to train the machine learning model, the accuracy of lithography simulation improves by 7%.