Photomask Polarization Control for Defect Detection Sensitivity
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Solution Overview
Problem
Photomask inspection systems face challenges in achieving adequate sensitivity and accuracy, particularly for advanced technologies like extreme ultraviolet (EUV) photomasks, due to shrinking feature sizes and increasing pattern complexity.
Innovation Solution
A recipe generation system that utilizes a controller to generate a performance matrix for defect types by varying the rotational positions of waveplates in polarization controlling optics, incorporating a polarizing beam splitter, to identify a run-time polarization state that satisfies inspection tolerances, using techniques like principal component analysis to optimize defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If polarization control optics with multiple waveplates are used to optimize defect detection sensitivity, then measurement precision improves, but device complexity increases
Solution Approach 1:
The system performs preliminary characterization by measuring the performance matrix across multiple polarization states before actual inspection. This pre-characterization data is stored and used to select optimal polarization settings for different defect types, eliminating the need for real-time polarization optimization during inspection and reducing operational complexity
Solution Approach 2:
The system dynamically selects polarization states based on the specific defect type being inspected. By having multiple waveplates with adjustable rotational positions, the system can adapt the polarization state to match the optimal configuration for each defect category, maximizing detection sensitivity while maintaining manageable complexity through software-controlled selection
2Measurement precision
If multiple polarization states are evaluated to optimize inspection performance, then measurement precision improves, but loss of time increases
Solution Approach 1:
The performance matrix characterizing defect detection sensitivity across multiple polarization states is measured and stored in advance. During actual inspection, the system simply retrieves pre-determined optimal polarization settings from this matrix, avoiding time-consuming real-time optimization while maintaining high inspection accuracy
Solution Approach 2:
Instead of evaluating all possible polarization states during inspection, the system measures a sufficient set of polarization states in advance to characterize performance adequately. This partial measurement approach provides enough information to select optimal settings without the excessive time cost of complete characterization during operation
3Measurement precision
If polarization control components are added to the inspection system, then measurement precision improves, but device complexity increases
Solution Approach 1:
The system performs preliminary measurement of the performance matrix that captures defect detection sensitivity across multiple polarization states. This pre-acquired data enables the system to select optimal polarization configurations without requiring complex real-time control, reducing the operational burden despite additional optical components
Solution Approach 2:
The polarization control optics with multiple waveplates serve multiple functions: they enable characterization of defect sensitivity across different polarization states, provides selectable optimal settings for various defect types, and maintain efficient light transmission. This multi-functionality justifies the added complexity by delivering comprehensive inspection capability
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
Enhances defect detection sensitivity and accuracy by selecting polarization states that balance performance across multiple defect types, improving signal-to-noise ratio and reducing photon shot noise, while maintaining efficient light transmission.
Implementation Method 1
a polarizing beam splitter and at least two waveplates positioned between the polarizing beam splitter and a sample
Implementation Method 2
The polarization controlling optics may include a polarizing beam splitter
Data Source
AI summary
A recipe generation system may include a controller with one or more processors configured to execute program instructions. The instructions may cause the processors to generate a performance matrix for one or more defect types. The performance matrix may include inspection data generated with multiple polarization states of illumination light associated with rotational positions of at least two waveplates in a polarization controlling optics of an inspection system. The polarization controlling optics may include a polarizing beam splitter and the waveplates. The system may generate inspection data by propagating illumination light through the optics to the sample and capturing light from the sample by a detector through the optics. The processors may identify a run-time polarization state satisfying an inspection tolerance and generate an inspection recipe using the run-time polarization states.