Multi-Layer Image Alignment for Semiconductor Metrology
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Solution Overview
Problem
Current semiconductor manufacturing processes face challenges in accurately determining control parameters for processes such as lithography, etching, and ion-implantation, especially in low-k1 lithography where features are printed below the classical resolution limit, leading to difficulties in reproducing patterns with intended dimensions and electrical functionality.
Innovation Solution
A method is introduced to determine an image-metric of features on a substrate by obtaining multiple images of the same features at different layers, aligning these images to remove overlay errors, and calculating the image-metric based on comparisons of the aligned images. This method allows for the determination of control parameters for manufacturing processes by analyzing image-related metrics such as critical dimension uniformity, line width roughness, and overlay errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple images are obtained and aligned to remove overlay errors, then manufacturing precision is improved, but measurement precision requirements increase
Solution Approach 1:
The patent divides the measurement process into multiple independent image acquisitions at different layers, allowing each image to be processed and aligned separately. This segmentation enables the use of alignment marks and reference features to compensate for overlay errors, thereby improving manufacturing precision without requiring impossible measurement precision
Solution Approach 2:
The patent introduces alignment marks and reference features as intermediaries between the actual features and the measurement system. These intermediaries provide stable reference points for image alignment, allowing overlay errors to be removed through computational alignment rather than requiring direct precise measurement of the features themselves
2Manufacturing precision
If images are aligned to remove overlay errors, then manufacturing precision is improved, but process complexity increases
Solution Approach 1:
The patent performs preliminary alignment by identifying and matching alignment marks across multiple images before actual measurement. This preliminary action removes overlay errors in advance, simplifying the subsequent measurement process and reducing the complexity of real-time image processing
Solution Approach 2:
The patent creates aligned copies of images from different layers by applying transformation parameters derived from alignment mark matching. These copied and aligned images can then be analyzed without dealing with the original overlay errors, reducing processing complexity while maintaining measurement accuracy
Data Source
AI summary
A method for determining an image-metric of features on a substrate, the method including: obtaining a first image of a plurality of features on a substrate; obtaining one or more further images of a corresponding plurality of features on the substrate, wherein at least one of the one or more further images is of a different layer of the substrate than the first image; generating aligned versions of the first and one or more further images by performing an alignment process on the first and one or more further images; and calculating an image-metric in dependence on a comparison of the features in the aligned version of the first image and the corresponding features in the one or more aligned versions of the one or more further images.