Lithography Simulation Using Offline Pre-characterization for Accuracy
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Solution Overview
Problem
Current lithographic simulation methods, such as the Kirchhoff approximation and modified thin-mask models, are inadequate for accurately simulating photolithography processes due to their reliance on heuristic parametric models and failure to account for diffraction, polarization, and coupling effects, especially at advanced technology nodes below 45 nm, leading to poor accuracy and inefficiency.
Innovation Solution
A system and method for improved lithographic simulation that employs offline pre-characterization to generate models accounting for diffraction, polarization, and coupling effects, and uses online evaluation with model reduction techniques to efficiently simulate the photolithography process, incorporating physics-based governing equations and parameterized forms to enhance accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Kirchhoff approximation or modified thin-mask models are used for lithographic simulation, then computational efficiency is improved, but simulation accuracy deteriorates due to failure to account for diffraction, polarization, and coupling effects
Solution Approach 1:
The patent applies preliminary action by pre-characterizing mask patterns offline using rigorous electromagnetic solvers that fully account for diffraction, polarization, and coupling effects. These pre-computed characterizations are stored in lookup tables, enabling fast online simulation without repeatedly solving full physics equations, thus achieving both high accuracy and computational efficiency
Solution Approach 2:
The patent creates simplified copies of the complex electromagnetic field interactions by representing them as pre-computed lookup tables based on mask pattern geometry and lithographic parameters. These tabulated models copy the essential physics behavior without requiring full physics-based equations during online simulation, maintaining accuracy while improving speed
2Measurement precision
If full physics-based equations are solved for lithographic simulation, then simulation accuracy is improved by accounting for all physical effects, but computational time increases significantly
Solution Approach 1:
The patent performs the computationally intensive task of solving full physics-based electromagnetic equations in advance during an offline pre-characterization phase. The results are stored in tabulated form, eliminating the need to solve these equations during online simulation, thus achieving high accuracy without the associated computational time penalty
Solution Approach 2:
The patent applies partial action by using simplified models that capture the dominant physical effects (diffraction, polarization, coupling) through pre-computed tabulated data, rather than solving the complete set of Maxwell's equations in real-time. This provides sufficient accuracy for most practical applications while dramatically reducing computational requirements
3Ease of manufacture
If heuristic parametric models are used for mask modeling, then ease of implementation is improved, but fidelity to actual lithographic processes deteriorates
Solution Approach 1:
The patent replaces heuristic parametric models with tabulated models that copy the actual physical behavior of light-matter interactions in photolithography. These tables are generated from rigorous electromagnetic simulations, providing faithful representations of diffraction, polarization, and coupling effects without relying on simplified assumptions
Solution Approach 2:
The patent transforms the mask model from a heuristic parametric form to a tabulated form based on actual physical parameters (mask pattern geometry, lithographic wavelength, numerical aperture). This changes the model structure to directly reflect physical reality while maintaining computational tractability through pre-computation
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 provides more accurate and efficient lithographic simulation by accounting for critical effects without solving full physics-based equations, reducing CPU time, and improving the fidelity of mask models, especially for smaller feature sizes, thereby enhancing the design and manufacturing of integrated circuits.
Implementation Method 1
offline pre-characterization to generate models accounting for diffraction, polarization, and coupling effects
Implementation Method 2
offline pre-characterization to generate models accounting for diffraction, polarization, and coupling effects
Data Source
AI summary
Disclosed are improved methods, systems, and computer program products for lithographic simulation of an electronic circuit design. Various embodiments of the present invention identifies a mask pattern, performs offline precharacterization for the mask pattern by solving an equation which models a solution for the mask pattern and an interaction between the mask pattern and one or more effects, performs online evaluation based at least upon a parameterized form of the equation, determines a field around the mask pattern based at least upon the act of performing the online evaluation, and stores a result of the act of determining an electromagnetic field around the mask pattern in a tangible computer readable or usable medium