Combined Alignment Modeling for Multi-Layer Overlay Accuracy
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Solution Overview
Problem
Existing lithographic processes face challenges in accurately aligning and measuring patterns on substrates due to distortions caused by processing steps and apparatuses, leading to errors in overlay and feature placement, particularly when different modeling strategies are used for different layers.
Innovation Solution
A method for modeling alignment data involves obtaining alignment data from multiple layers, fitting separate models to each layer, determining weightings for model parameters, and combining these models to create a combined alignment model for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If different modeling strategies are used for different layers, then alignment accuracy for each layer can be optimized, but errors are introduced due to inconsistencies between models
Solution Approach 1:
The patent combines multiple layer-specific alignment models into a single unified alignment model. The system integrates alignment data from multiple layers and merges the individual models to create one consistent model that maintains the accuracy benefits of layer-specific modeling while eliminating the inconsistency errors that would arise from using separate models.
2Measurement precision
If separate models are fitted to each layer, then layer-specific alignment characteristics are captured, but the complexity of the alignment process increases
Solution Approach 1:
The patent segments the alignment modeling process into distinct phases: first fitting separate models to individual layers to capture layer-specific characteristics, then combining these models into a unified model. This segmentation allows the system to benefit from layer-specific optimization while managing complexity through a structured multi-step approach rather than attempting to create one complex model all at once.
3Measurement precision
If extensive measurement operations are performed prior to exposure, then alignment accuracy is improved, but processing time increases
Solution Approach 1:
The patent performs alignment measurements and model fitting operations before the actual exposure process. By conducting extensive measurement operations and creating the unified alignment model in advance, the system ensures high alignment accuracy is achieved beforehand, allowing the exposure process itself to proceed efficiently without time-consuming measurements during production.
Data Source
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AI summary
Disclosed is method for modeling alignment data for exposure of a third layer on a substrate in an exposure process. The method comprises obtaining at least first layer alignment data relating to a first layer and second layer alignment data relating to a second layer; fitting a first model to the first layer alignment data to obtain a first alignment model and fitting a second model to the second layer alignment data to obtain a second alignment model; determining, for each of a plurality of different subsets of model parameters of said first alignment model and second alignment model, a respective weighting for each of said first model and second model; and combining the first model and second model in accordance with said weighting to determine a combined alignment model.