Abstract
Background: Negative-tone development (NTD) photoresists are prone to shrinkage effects during lithographic processing. Along with deformation seen during the postexposure bake (PEB), there are additional effects during the development that cannot be fully explained by a conventional PEB shrinkage model alone. Aim: Understand the impact of PEB shrinkage on the development rate. Develop a model that can help predict resist profiles after chemical development. Approach: A PEB shrinkage model for NTD resists is introduced, which uses the thermal properties of the resist material to help simulate shrinkage. The deformed state of the resist is used as an input to the development rate equation to predict the final feature dimensions observed in experiments. Results: The strain concentration within the resist bulk can have an influence on the stability of the resist during the development. The strain influences the development rate depending on the resist feature shape and contours. Conclusions: The results from this study can help improve optical proximity correction (OPC) modeling performance and help better understand the deformation characteristics of NTD resist materials. The model also shows that the development shrinkage has an influence on the edge placement error.
Highlights
Traditional negative-tone development (NTD) resists are prone to shrinkage and deformation effects during various stages of the lithography process
The strain concentration within the resist bulk can have an influence on the stability of the resist during the development
A number of 2D test cases were analyzed in order to verify and better understand the shrinkage effects resulting from a variation in the input parameters
Summary
Traditional negative-tone development (NTD) resists are prone to shrinkage and deformation effects during various stages of the lithography process. The main benefit of these methods was a lower overall computation time compared to more rigorous methods. These approaches do not consider the thermomechanical interaction of the resist polymer with the heating step. The thermal properties of the resist provide information on its conductivity and heat capacity. From another perspective, the modeling technique introduced in this paper uses the thermal properties of the resist to help model the shrinkage effects during PEB. Negative-tone development (NTD) photoresists are prone to shrinkage effects during lithographic processing. Along with deformation seen during the postexposure bake (PEB), there are additional effects during the development that cannot be fully explained by a conventional PEB shrinkage model alone
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