Photolithographic Imaging Simulation Using Low Pass Filtering
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Solution Overview
Problem
Current lithographic projection systems face challenges in accurately reproducing patterns with dimensions smaller than the classical resolution limit, due to smaller diffraction pattern overlap and low illumination efficiency, which affects scanner throughput and pattern fidelity.
Innovation Solution
A method is introduced to simulate and improve pattern imaging by modifying the pattern using low pass filters, specifically reducing the number of edges and vertices, and applying edge filters based on geometry, to enhance thick mask modeling and account for three-dimensional mask effects, source effects, and optical system effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithographic projection systems are used to image patterns with dimensions smaller than the classical resolution limit, then sub-wavelength feature imaging is attempted, but diffraction pattern overlap is reduced and illumination efficiency is low, affecting scanner throughput and pattern fidelity
Solution Approach 1:
The patent applies preliminary actions by modifying the pattern before imaging through low pass filtering and edge filter application. These pre-processing steps reduce high-frequency components that cause diffraction issues, enabling better sub-wavelength feature imaging while maintaining scanner throughput by avoiding repeated exposures
Solution Approach 2:
The patent changes parameters by applying low pass filters with specific cutoff frequencies and edge filters with defined kernel sizes to the pattern. These parameter modifications transform the original pattern into a filtered version that images more accurately at sub-wavelength dimensions, resolving the contradiction between imaging precision and throughput
2Measurement precision
If high-resolution patterns with many edges and vertices are imaged, then pattern fidelity is maintained, but computational complexity increases and scanning time is extended
Solution Approach 1:
The patent extracts and removes high-frequency components from the pattern through low pass filtering. By taking out the problematic high-frequency edges and vertices that contribute most to computational complexity and scanning time, the system maintains essential pattern fidelity while reducing processing time
Solution Approach 2:
The patent applies partial action by selectively filtering only the high-frequency components that cause excessive computational load, rather than removing all detail. The low pass filter preserves low-frequency pattern information while removing excessive high-frequency noise, achieving a balance between fidelity and speed
3Manufacturing precision
If thick mask effects and three-dimensional mask effects are accounted for in simulation, then pattern modeling accuracy is improved, but computational complexity and simulation time increase
Solution Approach 1:
The patent applies preliminary action by pre-filtering the pattern with low pass filters before performing thick mask simulations. This pre-processing reduces the computational complexity of the subsequent three-dimensional mask effect calculations by removing high-frequency components that would otherwise require excessive computational resources
Solution Approach 2:
The patent segments the simulation process into distinct stages: first applying low pass filtering to reduce complexity, then applying edge filters, and finally performing thick mask modeling. This segmentation allows each step to be optimized independently, reducing overall computational complexity while maintaining accuracy
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 improves the accuracy of pattern reproduction, increases scanner throughput, and enhances the fidelity of sub-wavelength feature imaging by reducing computational complexity and accounting for edge interference, leading to more accurate critical dimension predictions.
Implementation Method 1
modifying the pattern to improve a thick mask model of an image of the pattern... applying low pass filters, specifically reducing the number of edges and vertices
Implementation Method 2
A lithographic projection apparatus can be used... to transfer a pattern on the patterning device to a substrate... by methods such as irradiating the target portion through the pattern on the patterning device
Implementation Method 3
the lithographic projection apparatus will have a reduction ratio M (e.g., 4)... Different portions of the pattern on the patterning device are transferred to one target portion progressively
Data Source
AI summary
A method of simulating a pattern to be imaged onto a substrate using a photolithography system, the method includes obtaining a pattern to be imaged onto the substrate, smoothing the pattern, and simulating an image of the smoothed pattern. The smoothing may include application of a graphical low pass filter and the simulating may include application of edge filters from an edge filter library.