Back-Focal-Plane Detector for Lithography Fault Detection
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Solution Overview
Problem
Current fault detection and classification methods in lithographic systems are time-consuming and computationally intensive, often requiring a limited number of data points to reduce processing time, which compromises accuracy, and existing methods like scatterometry are not practical for real-time monitoring of system performance.
Innovation Solution
An inspection apparatus and method that uses a detector to measure radiation redirected from a substrate at its back focal plane, monitoring changes in radiation to correlate with faults, and notifying users of detected issues, allowing for more data points to be used without increasing computation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scatterometry is used to determine the exact shape of a structure on a layer, then measurement precision is improved, but processing time increases significantly
Solution Approach 1:
The patent extracts only the essential information needed for fault detection from the scattered radiation data, rather than performing complete scatterometry analysis. By using a detector at the back focal plane to capture radiation intensity distributions, the system obtains sufficient fault detection data without computing the complete structural parameters, thus reducing processing time while maintaining detection accuracy.
Solution Approach 2:
The system performs a partial measurement by detecting radiation at specific angular ranges corresponding to the back focal plane, rather than measuring the complete scattered radiation pattern. This partial action provides enough information for fault detection and classification without the computational burden of full scatterometry, achieving a balance between precision and speed.
2Productivity
If a limited number of data points are used to reduce processing time, then productivity is improved, but measurement precision deteriorates
Solution Approach 1:
The patent implements partial measurement by capturing radiation intensity distributions at the back focal plane, which provides sufficient data for accurate fault detection without requiring complete scatterometry data. This approach uses a manageable number of data points that maintain detection precision while enabling faster processing and higher throughput.
Solution Approach 2:
The system replaces the computationally intensive mechanical process of complete scatterometry analysis with a simplified detection approach using a back focal plane detector. This substitution reduces the computational burden and data processing requirements while maintaining the essential fault detection capability, thereby improving productivity without sacrificing measurement precision.
3Measurement precision
If complete scatterometry analysis is performed, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts only the necessary information for fault detection from the scattered radiation, using a back focal plane detector to capture intensity distributions at specific angles. This extraction approach avoids the complex computational algorithms required for complete scatterometry analysis, reducing device complexity while maintaining sufficient measurement precision for fault detection and classification.
Solution Approach 2:
Instead of using complete scatterometry analysis to first determine structure parameters and then detect faults, the patent inverts the approach by directly detecting fault-related information from the radiation intensity distribution at the back focal plane. This inverted methodology simplifies the measurement process and reduces computational complexity while maintaining fault detection accuracy.
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
Enables efficient and accurate fault detection and classification in lithographic systems by monitoring changes in radiation patterns, reducing the need for extensive data processing and improving throughput by identifying faults before they become significant.
Implementation Method 1
detecting radiation, redirected from a structure on a substrate, at a back focal plane of the detector
Implementation Method 2
measuring the spectrum (intensity as a function of wavelength) of the radiation scattered into a particular narrow angular range
Data Source
AI summary
A fault detection and classification method is disclosed that uses raw back-focal-plane image data of radiation from a substrate surface, detected by a scatterometer detector, to determine a variation in the raw data and correlate the variation in the raw data with a possible fault in a lithographic apparatus or a process that patterned the substrate surface. The correlation is carried out by comparing the variation in the raw data with known metrology data. Once a fault has been determined, a user may be notified of the fault.