Lithography Stepper Alignment Compensation via Field Segmentation
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Solution Overview
Problem
Photolithography steppers experience non-linear distortion as they age, leading to alignment difficulties due to varying magnification, rotation, and offset issues across different visual fields, which existing methods struggle to address effectively and efficiently, especially when dealing with diverse product varieties and high production turnover.
Innovation Solution
A method involving a test template with multiple visual fields to derive and calculate compensation amounts for each field, selecting the closest matching compensation values for alignment, allowing for accurate alignment compensation regardless of visual field size, and providing estimated values before processing to reduce misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If lens adjustment is performed to improve distortion, then alignment accuracy is improved, but cost increases and distortion may still worsen over time
Solution Approach 1:
The patent divides the visual field into multiple segments (first visual field, second visual field, third visual field) and creates separate compensation amount sets for each segment. This segmentation allows precise compensation for different regions without requiring expensive lens adjustments, resolving the contradiction by achieving high alignment accuracy through software-based regional compensation rather than hardware modification.
Solution Approach 2:
The patent changes the parameter approach from physical lens adjustment to digital compensation amount modification. By calculating and applying different compensation amounts (rotation, magnification, offset) for each visual field segment, the system achieves alignment accuracy without the cost and complexity of lens adjustments, while also providing a stable long-term solution.
2Manufacturing precision
If compensation is performed based on measured overlay values of different products, then alignment accuracy is improved, but manpower requirements increase significantly
Solution Approach 1:
The patent performs preliminary action by pre-calculating compensation amounts for multiple visual field segments using a test template before actual production. This preliminary compensation amount calculation eliminates the need for manual measurement and compensation adjustment for each new product, significantly reducing manpower requirements while maintaining high alignment accuracy across diverse product varieties.
Solution Approach 2:
The system implements self-service by automatically selecting the appropriate compensation amount set based on the product's visual field characteristics. The stepper automatically applies the correct compensation without requiring manual intervention or expertise, improving productivity while maintaining alignment accuracy across fast-renewing product lines.
3Device complexity
If a single visual field is selected for monitoring, then monitoring cost is reduced, but alignment accuracy deteriorates when product visual field deflects from selected field
Solution Approach 1:
The patent creates a universal compensation solution by calculating compensation amounts for multiple visual field segments (first, second, third visual fields) that can cover various product visual field sizes and positions. This multi-functional compensation system maintains alignment accuracy regardless of which visual field the product uses, while the system intelligently selects the appropriate compensation set, effectively providing universal coverage without requiring separate monitoring systems for each field.
4Manufacturing precision
If compensation values are calculated for all visual fields, then alignment accuracy for diverse products is improved, but processing time increases
Solution Approach 1:
The patent performs the computationally intensive compensation amount calculations in advance during the setup phase using a test template, before actual production begins. This preliminary action stores the calculated compensation amounts for multiple visual fields, so during production the system only needs to retrieve and apply the appropriate pre-calculated values, maintaining high alignment accuracy for diverse products while minimizing processing time loss during manufacturing.
Data Source
AI summary
A lithography stepper alignment and control method, comprising: providing a test template having a plurality of field sizes, and deriving a set of overlay values for each field size (S1); calculating a set of compensation amounts for the overlay value of each field size (S2); and, comparing a set of estimated alignment compensation values for a product with each compensation amount for each field size, selecting as the product alignment compensation values the set of compensation amounts of a field size closest to the set of estimated alignment compensation values, and, using the product alignment compensation values to perform alignment compensation on said product (S3).