Lithographic Dose Correction via Tile-Based Proximity Compensation
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Solution Overview
Problem
Current lithographic techniques face challenges in efficiently modeling and compensating for the proximity effect, leading to increased complexity and cost due to the need for precise calculations that result in unacceptably long processing times as device spacing decreases.
Innovation Solution
A method involving tile-based proximity effect calculations and Self-Consistent Proximity Effect Compensation Technique (SPECTRE) is employed to reduce computational complexity by approximating the effects of nearby features on target regions, allowing for accurate dosage adjustments and improved pattern quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If precise proximity effect calculations are performed for all features, then manufacturing precision is improved, but processing time increases unacceptably
Solution Approach 1:
The patent divides the design database into multiple tiles, each representing a local region of the layout. By calculating proximity effects independently for each tile rather than for the entire layout, the computational complexity is reduced from O(N^2) to O(N), where N is the number of features. This segmentation allows precise local calculations while avoiding the prohibitive cost of global calculations.
Solution Approach 2:
The patent performs proximity effect calculations only for features within a certain distance threshold from the target feature, rather than calculating for all features in the database. This partial action approach focuses computational resources on the most significant contributors to the proximity effect, achieving sufficient accuracy while dramatically reducing processing time.
2Productivity
If device spacing is decreased to increase functional density, then productivity is improved, but the complexity of proximity effect modeling increases
Solution Approach 1:
As device spacing decreases and more features fall within the proximity effect range, the tile-based segmentation becomes even more critical. Each tile handles a localized set of features, keeping the number of features per tile manageable even when overall device density increases. This maintains modeling complexity at acceptable levels while supporting higher functional density.
Solution Approach 2:
The patent modifies the proximity effect model parameters (such as the cutoff distance for calculations) based on the local feature density and spacing. When devices are closely spaced, the model adapts by adjusting calculation parameters to focus on the most relevant nearby features, reducing the effective complexity of modeling while maintaining accuracy for high-density layouts.
Data Source
AI summary
A method of quantifying a lithographic proximity effect and determining a lithographic exposure dosage is disclosed. In an exemplary embodiment, the method for determining an exposure dosage comprises receiving a design database including a plurality of features intended to be formed on a workpiece. A target region of the design database is defined such that the target region includes a target feature. A region of the design database proximate to the target region is also defined. An approximation for the region is determined, where the approximation represents an exposed area within the region. A proximity effect of the region upon the target feature is determined based on the approximation for the region. A total proximity effect for the target feature is determined based on the determined proximity effect of the region upon the target feature.