Photolithographic Mask Optimization Using Inverse Lithography
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Solution Overview
Problem
Existing photolithographic mask optimization technologies are limited by the location of lattice points, leading to unsatisfactory imaging results due to the Optical Proximity Effect, as the same main patterns located at different lattice points result in significantly different assistant feature placements and locations, affecting the final optimized mask pattern.
Innovation Solution
A method that divides the edges of the main pattern into short edges and generates same or similar assistant feature sample points around similar main patterns, forming an objective function with these variables for optimization, using an inversion lithography technology to adjust the mask pattern and assistant feature placement, thereby minimizing the impact of lattice point regularity and improving optimization accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the mask is gridded first and optimization is performed based on lattice points, then the optimization process is simplified and structured, but the final optimization result is subject to the regularity of lattice points leading to unsatisfactory imaging
Solution Approach 1:
The patent segments the optimization process into two independent stages: first optimizing the main pattern geometry, then optimizing assistant feature placement. This segmentation allows each stage to focus on specific optimization variables without being constrained by the lattice point structure, thereby improving imaging accuracy while maintaining process organization.
Solution Approach 2:
The patent performs preliminary optimization of the main pattern before adding assistant features. By first determining the optimal main pattern geometry and then separately optimizing assistant feature placements based on that result, the method avoids the constraint of having to fit both elements to a rigid lattice structure from the beginning, thus improving final imaging accuracy.
2Adaptability or versatility
If assistant features are placed at different lattice points for the same main pattern located at different positions, then the optimization covers various locations, but the number and location of assistant features become very different leading to inconsistent optimization results
Solution Approach 1:
The patent applies local quality by determining assistant feature placements based on the local geometric characteristics of each main pattern rather than applying a uniform lattice-based approach. Each main pattern receives assistant features optimized for its specific location and shape, ensuring consistent optimization results across different positions while maintaining adaptability to local variations.
Solution Approach 2:
The patent performs preliminary optimization of the main pattern to establish a consistent reference framework before optimizing assistant features. This preliminary action ensures that subsequent assistant feature placements are based on a stable, optimized main pattern structure, reducing variability in optimization results across different locations.
3Manufacturing precision
If the pattern dimension is much smaller than the wavelength of the light source, then the technology node is advanced, but the Optical Proximity Effect becomes significant causing extreme deformation of the exposure pattern
Solution Approach 1:
The patent applies preliminary anti-action by pre-compensating for the Optical Proximity Effect through inverse lithography optimization. The optimization process calculates and applies counteracting adjustments to the mask pattern in advance, so that when the Optical Proximity Effect occurs during exposure, it compensates for the predicted deformations, thereby maintaining pattern accuracy at advanced technology nodes.
Solution Approach 2:
The patent implements feedback by using the predicted exposure pattern deformation caused by the Optical Proximity Effect as input to guide the mask pattern optimization. The optimization process continuously adjusts the mask pattern based on feedback from the predicted exposure results, iteratively reducing the impact of the Optical Proximity Effect until the desired pattern fidelity is achieved.
Data Source
AI summary
The present invention relates generally to the technical field of integrated circuit mask design, and more particularly to a method, an apparatus and an electronic device for photolithographic mask optimization of joint optimization of pattern and image. The method includes steps: inputting the main pattern; dividing edges of each main pattern into short edges, and regarding the short edges as a first variable for optimizing the main pattern; generating same or similar assistant feature sample points around same or similar main patterns, and regarding the assistant feature sample points as a second variable for optimizing the main pattern; and forming an objective function with the first variable and the second variable as optimization variables. The rules for generating assistant feature sample points around each main pattern are consistent, which are not limited to specific locations of the main pattern and ensures the consistency of final results for optimizing each main pattern.