Substrate Height Map Determination via Alignment Mark Scanning
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Solution Overview
Problem
The existing method of obtaining a height map of a substrate in lithographic apparatuses is time-consuming due to the need for multiple scans of the complete substrate surface, which limits production performance.
Innovation Solution
A method that determines a height map of a substrate by measuring alignment marks at different tilted and offset positions, using a shape model based on a single scan or low-resolution height map, and calibrating the relationship between measured positions and heights to calculate the substrate's height map efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple scans of the complete substrate surface are performed to obtain a height map, then the accuracy of the height map is improved, but the time required to obtain the height map increases
Solution Approach 1:
The substrate surface is divided into multiple regions, and the height map is obtained by scanning only specific regions containing alignment marks rather than the entire substrate surface. This segmentation approach maintains sufficient measurement precision for focus and overlay performance while significantly reducing the scanning time and computational resources required.
Solution Approach 2:
The method extracts only the essential information needed for height map generation by focusing scans on alignment marks rather than scanning the complete substrate surface. This extraction of critical measurement points maintains the necessary accuracy for lithographic alignment while eliminating redundant scanning of areas that do not contribute to the height map quality.
2Manufacturing precision
If multiple scans of the complete substrate surface are performed to obtain a height map, then the focus performance is improved, but the production performance is reduced
Solution Approach 1:
The scanning process is segmented to focus only on critical regions containing alignment marks rather than the entire substrate. This maintains sufficient focus performance for lithographic processing while dramatically reducing the time required, thereby improving production performance and throughput.
Solution Approach 2:
Instead of performing exhaustive scans of the complete substrate surface, the method applies partial scanning action limited to essential regions. This partial action provides sufficient height map quality for focus performance while avoiding the excessive time consumption that would limit production performance.
Data Source
AI summary
The present invention provides a method to obtain a height map of a substrate having alignment marks, the method comprising the steps: determining a height of one or more locations or areas of the substrate, and determining the height map of the substrate on the basis of the determined height of the one or more locations or areas of the substrate and a shape model of the substrate.