Lithographic Process Modeling via Substrate Fingerprint Segmentation
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Solution Overview
Problem
Current methods for modeling lithographic processes are limited in obtaining comprehensive information across a substrate's surface, often relying on small target portions or varying exposure conditions, which do not fully account for substrate fingerprints such as resist thickness variations or etch rate profiles, leading to non-uniform pattern features.
Innovation Solution
A method and lithographic arrangement that project a beam of radiation onto a substrate with varying properties in different directions across a target portion, allowing for the measurement and modeling of these variations to improve uniformity and accuracy of pattern features by establishing relationships between the properties of the lithographic process and the resulting pattern features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If small target portions are used for measurements, then measurement time is reduced, but the comprehensiveness of substrate fingerprint information is insufficient
Solution Approach 1:
The substrate surface is divided into multiple target portions, each with different properties (e.g., different resist thicknesses or etch rates). By measuring pattern features across these segmented target portions, comprehensive substrate fingerprint information is obtained without requiring measurements across the entire substrate surface, thus reducing total measurement time while maintaining information completeness.
Solution Approach 2:
Different target portions are assigned different local properties (such as varying resist thickness or etch rate characteristics) to represent different regions of the substrate. This allows the measurement process to capture the diversity of substrate conditions across the surface by examining these locally differentiated target portions, achieving comprehensive information gathering efficiently.
2Measurement precision
If comprehensive substrate fingerprint information is obtained across the entire substrate surface, then modeling accuracy is improved, but measurement time and process complexity increase
Solution Approach 1:
Instead of measuring the entire substrate surface, the method segments the measurement task into multiple target portions with different properties. These segmented measurements collectively provide comprehensive substrate fingerprint information needed for accurate modeling, significantly reducing the time required compared to full-surface measurements.
Solution Approach 2:
The method uses a partial action approach by measuring only specific target portions with different properties rather than the entire substrate. This partial measurement strategy is sufficient to capture the essential substrate fingerprint information needed for accurate lithographic process modeling, avoiding the excessive time cost of complete surface coverage.
3Loss of information
If multiple target portions with different properties are measured, then substrate fingerprint information is improved, but device complexity increases
Solution Approach 1:
The lithographic apparatus is configured to perform multiple functions: it can form pattern features on target portions with different properties and also measure the resulting pattern features. This multi-functionality allows comprehensive substrate fingerprint information to be obtained using the same device without requiring additional specialized measurement equipment, thus avoiding increased device complexity.
Solution Approach 2:
The lithographic apparatus measures the pattern features it itself has formed on the target portions. This self-service capability allows the device to gather comprehensive substrate fingerprint information without requiring separate external measurement tools, maintaining device simplicity while achieving information completeness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables more accurate and efficient determination of exposure conditions, reducing non-uniformity in critical dimensions and sidewall angles of pattern features by capturing detailed substrate fingerprints, thus improving the uniformity and precision of lithographic processes across the substrate surface.
Implementation Method 1
A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate... a patterning device, such as, for examples, a mask or a reticle, may be used to generate a circuit pattern... This pattern can be imaged onto a target portion (e.g. comprising part of, one or several dies) on a substrate (e.g. a silicon wafer) having a layer of radiation-sensitive material (resist).
Data Source
AI summary
A method is described for obtaining information for use in modeling of a lithographic process. A pattern feature is formed on a target portion of a substrate by projecting a beam of radiation onto the target portion of the substrate. For that target portion the lithographic process is characterized by one or both of a first property that varies in a first direction along a surface of the substrate, and a second property that varies in a second direction along a surface of the substrate. A property of the pattern feature is measured. Using the measured property of the pattern feature and at least one of the first and second properties, information is obtained for use in modeling the process. The lithographic process may be or include the projection of the beam of radiation onto the surface of the substrate.