Negative-tone Photoresist Simulation via Variable Diffusion Coefficients
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Solution Overview
Problem
Current simulation methods for negative tone development processes in microlithography, such as the inverse Mack method, fail to accurately predict the behavior of chemically-amplified photoresists due to inadequate modeling of lithographic effects from developer diffusion into insoluble resist, leading to degraded modeling accuracy and process control challenges in high-volume manufacturing.
Innovation Solution
The method simulates a negative-tone development process by determining the reaction of a developer with a soluble photoresist surface and the flux of developer into exposed and partially soluble resist, incorporating a vector-valued diffusion coefficient dependent on the blocked polymer concentration to account for both dissolution-controlled and expansion-controlled regimes, thereby improving simulation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the inverse Mack method is used to simulate negative tone development, then the simulation process is simple, but the modeling accuracy is degraded
Solution Approach 1:
The patent introduces a concentration-dependent diffusion coefficient parameter that changes based on the blocked polymer concentration, transforming the simulation from a constant-parameter model to a variable-parameter model. This allows the simulation to capture the non-linear behavior of developer diffusion into insoluble resist, significantly improving modeling accuracy while maintaining computational feasibility
Solution Approach 2:
The patent transitions from a static simulation model to a dynamic one by incorporating the evolution of blocked polymer concentration during development. The diffusion coefficient dynamically adjusts as the resist transforms from soluble to insoluble states, enabling the model to capture time-dependent behavior and improve prediction of process latitude and depth-of-focus
2Productivity
If developer diffusion into insoluble resist is not modeled, then the simulation is computationally efficient, but the prediction of process latitude and depth-of-focus is inaccurate
Solution Approach 1:
The patent applies different diffusion characteristics to different regions of the resist based on local blocked polymer concentration. Areas with high blocked polymer concentration (insoluble regions) exhibit different diffusion behavior compared to areas with low blocked polymer concentration (soluble regions), enabling accurate local prediction of development effects
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces modeling errors, enhancing the prediction of process latitude and depth-of-focus, and allows for faster manufacturing throughput by optimizing the source-mask combination, resulting in more accurate and efficient microlithography processes.
Implementation Method 1
inadequate modeling of lithographic effects from developer diffusion into insoluble resist
Implementation Method 2
determining a reaction of a developer with a soluble photoresist surface
Data Source
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AI summary
In some embodiments, a method may include improving a development process of a photoresist. The method may include simulating a negative-tone development process of a photoresist. The method may include determining a reaction of a developer with a soluble photoresist surface. Determining the reaction of the developer may include applying a reaction rate constant at a power of a reaction order to a blocked polymer concentration to yield a resist dissolution rate of soluble resist comprising the dissolution-limited regime of development. The method may include determining a flux of the developer into exposed and partially soluble resist. Determining the flux of the developer may include applying a vector valued diffusion coefficient of the developer dependent upon the blocked polymer concentration to a gradient of developer concentration to an expansion rate of insoluble resist comprising the expansion-controlled regime of development. The method may include optimizing an illumination source and a mask on a full chip.