3D Mask Model for Lithography Simulation Accuracy
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Solution Overview
Problem
Current lithography simulation methods struggle with accurately modeling three-dimensional mask effects, particularly at sub-wavelength feature sizes, due to limitations in existing thin-mask approximations, which lead to inaccuracies in predicting patterning performance and verifying optical proximity corrections.
Innovation Solution
A three-dimensional mask model is developed, utilizing filtering kernels or correction factors derived from rigorous electromagnetic field simulations, to produce a near-field image that accounts for mask topography and polarization effects, enhancing the accuracy of lithography simulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If thin-mask approximation is used for lithography simulation, then computational speed is improved, but accuracy in predicting patterning performance deteriorates
Solution Approach 1:
The patent transitions from a two-dimensional thin-mask approximation to a three-dimensional mask model that incorporates mask topography and thickness variations. This dimensional expansion allows the simulation to account for near-field optical effects and electromagnetic field interactions that occur in the vertical dimension, thereby improving prediction accuracy without requiring full rigorous 3D electromagnetic simulations for every case.
Solution Approach 2:
The patent introduces additional parameters to characterize mask three-dimensional effects, including mask thickness, refractive index, and topography profiles. By incorporating these parameters into the lithography simulation model, the system can predict patterning performance more accurately while maintaining computational efficiency through optimized algorithms that handle the increased parameter space.
2Measurement precision
If rigorous electromagnetic field simulations are used to model three-dimensional mask effects, then accuracy in predicting patterning performance is improved, but computational complexity increases
Solution Approach 1:
The patent segments the complex three-dimensional mask structure into discrete computational elements or voxels, allowing the electromagnetic field simulation to be performed in a structured manner. This segmentation enables the use of efficient numerical methods such as finite difference time domain (FDTD) or rigorous coupled-wave analysis (RCWA) while maintaining manageable computational complexity through systematic decomposition of the problem space.
Solution Approach 2:
The patent introduces an intermediate model that bridges between simple thin-mask approximations and full rigorous electromagnetic field simulations. This intermediate three-dimensional mask model incorporates essential near-field effects and topography variations while using optimized algorithms and approximations that reduce computational complexity, serving as a practical mediator for most lithography simulation applications.
3Measurement precision
If three-dimensional mask model is used to account for mask topography, then accuracy in verifying optical proximity corrections is improved, but computational time increases
Solution Approach 1:
The patent performs preliminary characterization of mask three-dimensional effects by pre-calculating near-field optical responses for various mask topography configurations. These pre-computed results are stored in lookup tables or used to generate correction factors that can be applied during actual lithography simulation, avoiding the need to perform full three-dimensional electromagnetic field calculations for every simulation case and thereby reducing computational time.
Solution Approach 2:
The patent implements a hybrid approach that applies full three-dimensional mask modeling only to critical regions where mask topography effects are most significant, while using simplified models for less critical areas. This selective application of computational resources focuses accuracy where it matters most for optical proximity correction verification while maintaining overall computational efficiency across the entire device structure.
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
The three-dimensional mask model provides more accurate predictions of critical dimensions and patterning performance, improving the verification of optical proximity corrections and reducing errors in lithography processes, especially at sub-wavelength scales.
Implementation Method 1
utilizing filtering kernels or correction factors derived from rigorous electromagnetic field simulations
Implementation Method 2
produce a near-field image that accounts for mask topography and polarization effects
Data Source
AI summary
A three-dimensional mask model that provides a more realistic approximation of the three-dimensional effects of a photolithography mask with sub-wavelength features than a thin-mask model. In one embodiment, the three-dimensional mask model includes a set of filtering kernels in the spatial domain that are configured to be convolved with thin-mask transmission functions to produce a near-field image. In another embodiment, the three-dimensional mask model includes a set of correction factors in the frequency domain that are configured to be multiplied by the Fourier transform of thin-mask transmission functions to produce a near-field image.