Pupil Plane Metrology for Lithographic Alignment Error Correction
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Solution Overview
Problem
Current calibration methods for metrology sensors in lithographic apparatuses are insufficient in correcting for sensor aberration-induced errors, particularly those that are process-dependent or stack-dependent, leading to alignment errors in complex device manufacturing.
Innovation Solution
A method involving pupil plane measurement datasets and sensor terms is used to determine correction values for alignment measurements, employing a data-driven approach to account for intensity variations in the pupil plane, which are processed using models like linear regression to improve alignment accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current calibration methods are used for metrology sensors, then the manufacturing process can be maintained with existing equipment, but alignment errors occur due to insufficient correction of sensor aberration-induced errors
Solution Approach 1:
The patent changes the parameters used in calibration by introducing pupil plane measurement datasets that capture intensity variations across different spatial frequencies and angles. Instead of using traditional calibration parameters, the system measures the actual pupil plane intensity distribution and uses these measurements to determine correction values, thereby improving alignment measurement accuracy while accounting for process-dependent errors
Solution Approach 2:
The patent implements a feedback mechanism where pupil plane measurements are continuously taken and used to update correction values. The system measures the pupil plane intensity distribution, compares it against reference data, and adjusts the alignment measurements accordingly. This closed-loop feedback approach enables the system to compensate for sensor aberrations and process-dependent errors dynamically
2Measurement precision
If traditional alignment measurement methods are used, then the measurement process remains simple and fast, but alignment errors occur due to uncorrected sensor aberrations
Solution Approach 1:
The patent makes the measurement system multi-functional by using the same pupil plane measurements for multiple purposes: characterizing sensor aberrations, determining correction values, and validating measurement accuracy. The pupil plane dataset serves multiple functions in the correction process, reducing the need for separate specialized measurement systems while improving position measurement accuracy
Solution Approach 2:
The patent introduces pupil plane measurements as an intermediary element between the sensor and the final alignment measurement. Instead of directly measuring alignment positions and applying corrections, the system first measures the pupil plane intensity distribution, which serves as an intermediate representation of sensor aberrations. This intermediary measurement enables more accurate correction while maintaining a systematic measurement approach
3Measurement precision
If calibration is performed without considering process and stack dependencies, then the calibration process remains quick and straightforward, but alignment errors persist due to uncorrected process-dependent aberrations
Solution Approach 1:
The patent performs preliminary pupil plane measurements to characterize sensor aberrations before conducting actual alignment measurements. By pre-measuring the pupil plane intensity distribution and determining correction values in advance, the system prepares correction data that accounts for process and stack dependencies. This preliminary action enables faster subsequent measurements while maintaining high alignment accuracy under varying process conditions
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 effectively corrects for process and stack-dependent alignment errors, enhancing the accuracy of position measurements and reducing alignment inaccuracies in lithographic processes.
Implementation Method 1
obtaining pupil plane measurement dataset at a pupil plane relating to scattered radiation resultant from a measurement of a structure
Implementation Method 2
a lens focused a bundle of parallel radiation beams onto a substrate
Implementation Method 3
A diffraction grating may be used to disperse the radiation into a number of diffraction orders
Data Source
AI summary
Disclosed is a method of metrology such as alignment metrology. The method comprises obtaining pupil plane measurement dataset at a pupil plane relating to scattered radiation resultant from a measurement of a structure. The method comprises determining a measurement value or correction therefor using the pupil plane measurement dataset and a sensor term relating to sensor optics used to perform said measurement.