Metrology Calibration via Pupil Representation Analysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In the context of metrology processes, particularly in lithographic apparatuses, there is a challenge in accurately aligning a radiation spot with metrology targets in confined spaces, leading to reduced accuracy due to limited space and the need for small target sizes, which can result in sampling regions outside the target, thereby compromising measurement precision.
Innovation Solution
A method involving obtaining and analyzing measurement data from a metrology process that includes illuminating a target with measurement radiation, detecting the redirected radiation, and processing the detected pupil representation to determine the position and focus properties of the radiation spot relative to the target, with calibration data being stored for various position and focus values to improve alignment and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the target size is reduced to fit confined spaces, then the metrology target can be positioned in product areas with limited space, but the alignment accuracy between the radiation spot and the target deteriorates
Solution Approach 1:
The patent applies preliminary action by determining calibration data that characterizes the radiation spot properties (size, shape, position, focus) before actual metrology measurements are performed. This calibration data is stored and used to guide the radiation spot alignment process, allowing the system to pre-compensate for misalignment issues that would otherwise occur with small targets in confined spaces.
Solution Approach 2:
The patent implements feedback by using detected pupil representations from initial measurements to determine radiation spot properties, then using this information to adjust and refine the alignment. The system continuously monitors the radiation spot characteristics and uses this feedback to improve positioning accuracy on small targets, thereby resolving the contradiction between small target size and alignment precision.
2Productivity
If the radiation spot is not perfectly aligned with the target, then the measurement process is simpler and faster, but the measurement accuracy deteriorates due to sampling regions outside the target
Solution Approach 1:
The system performs preliminary calibration measurements to characterize the radiation spot properties before actual metrology measurements. This calibration data is stored and used to optimize the measurement process, allowing for accurate measurements without requiring perfect alignment during production measurements, thus maintaining both speed and accuracy.
Solution Approach 2:
The patent applies partial action by using only the necessary calibration data and radiation spot characteristics needed for accurate measurement, rather than requiring perfect alignment in all conditions. The system uses the determined radiation spot properties to selectively adjust alignment parameters, achieving sufficient accuracy without excessive alignment efforts, thereby maintaining measurement productivity while improving precision.
3Measurement precision
If calibration data is collected for multiple position and focus values, then the alignment accuracy is improved, but the data processing time and complexity increase
Solution Approach 1:
The patent applies partial action by collecting calibration data for multiple position and focus values, but only using the necessary subset of this data for actual measurements. The system determines which calibration data points are most relevant based on the specific measurement conditions, avoiding the need to process all calibration data, thus reducing processing time while maintaining alignment accuracy.
Solution Approach 2:
The system performs calibration data collection in advance as a preliminary step, storing the results for later use. This allows the time-consuming calibration process to be separated from production measurements, so that alignment accuracy is improved through comprehensive calibration while the actual measurement process remains fast by using the pre-computed calibration data.
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 enhances the accuracy of metrology processes by allowing for precise alignment and focus adjustments, reducing errors caused by misalignment and focus issues, thereby improving the measurement precision and reliability in confined spaces.
Implementation Method 1
detecting radiation redirected by the target
Implementation Method 2
a detected pupil representation of an optical characteristic of the redirected radiation in a pupil plane
Data Source
AI summary
Methods for processing data from a metrology process and for obtaining calibration data are disclosed. In one arrangement, measurement data is obtained from a metrology process. The metrology process includes illuminating a target on a substrate with measurement radiation and detecting radiation redirected by the target. The measurement data includes at least a component of a detected pupil representation of an optical characteristic of the redirected radiation in a pupil plane. The method further includes analyzing the at least a component of the detected pupil representation to determine either or both of a position property and a focus property of a radiation spot of the measurement radiation relative to the target.