Scatterometry Overlay Using Pupil Plane Intensity Peaks
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Solution Overview
Problem
Current angle resolved scatterometry overlay metrology methods face challenges in accurately measuring overlay calculations due to limitations in measuring scattered light from periodic targets, particularly in deriving precise overlay information from intensity spatial distributions and peaks at the pupil plane.
Innovation Solution
Measuring intensity peaks at the pupil plane corresponding to specified diffraction orders from target cells and calculating overlay using these measurements, with the option to derive weight functions for adjusting metrology system performance and calibrating the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple target cells and diffraction orders are measured to improve overlay calculation accuracy, then measurement precision is improved, but device complexity and measurement time increase
Solution Approach 1:
The patent extracts only the essential information needed for overlay calculation from the full scatterometry measurement. Instead of using all measured intensity spatial distributions from multiple target cells and diffraction orders, the method selectively uses only the peak locations of specific diffraction orders (typically first order) to calculate overlay, thereby reducing complexity while maintaining accuracy.
Solution Approach 2:
The patent applies partial action by using only a subset of the available measurement data. Specifically, it uses only the peak location information from certain diffraction orders rather than processing all measured intensities from all target cells and orders, thus reducing computational complexity while achieving sufficient overlay precision.
2Measurement precision
If intensity spatial distributions from multiple target cells are measured to improve overlay estimation, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The patent extracts only the critical peak location information from the intensity spatial distributions rather than processing the complete distribution data from all target cells. This selective extraction significantly reduces the computational workload and measurement time while maintaining overlay estimation accuracy.
Solution Approach 2:
The method uses partial action by relying on only the peak location measurements from specific diffraction orders rather than processing all intensity spatial distribution data, thereby reducing measurement time while preserving the necessary precision for overlay calculation.
3Measurement precision
If standard scatterometry methods are used to measure overlay, then existing measurement capabilities are maintained, but measurement accuracy is limited by the complexity of data processing
Solution Approach 1:
The patent simplifies the data processing by extracting only the peak location information from the intensity spatial distributions. This extraction approach reduces the complexity of data processing while improving measurement accuracy, as it eliminates the need to process and interpret the full complexity of intensity distributions from multiple target cells and diffraction orders.
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 accurate overlay estimation and system calibration, potentially reducing the number of target cells and diffraction orders required, improving measurement accuracy and throughput, and identifying optical system imperfections.
Implementation Method 1
In angle resolved scatterometry overlay (SCOL) metrology measurements the scattered light from a periodic target is measured using a broad range of illumination angles
Implementation Method 2
measuring an intensity peak of at least one spot at a pupil plane of a metrology system that corresponds to a specified diffraction order scattered from at least one specified target cell
Data Source
AI summary
Metrology methods and modules are provided, which comprise measuring intensity spatial distributions and peaks of spots at the pupil plane of a metrology system that correspond to various diffraction orders scattered from target cells and calculating overlay(s) of the target cell(s) from the measured intensity spatial distributions and peaks. For example, intensity peak or distribution of zeroth diffraction orders from four cells, first diffraction orders from two cells as well as diffraction orders from a single cell may be used to derive an overlay estimation, which may also be compared to standard overlay measurements for different purposes. Intensity spatial distributions may also be used to derive weight function for adjusting measurements or the metrology system.