Underfilled Optical Metrology for Smaller Target Precision
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Overfilled metrology methods in lithographic processes are susceptible to edge effects, which affect the accuracy of parameter determination due to brighter or less bright regions along the edges of metrology targets, especially as targets become smaller.
Innovation Solution
A metrology method involving underfilled illumination to minimize edge effects by optimizing the illumination beam profile to only illuminate regions of interest on the target, capturing scattered radiation at an image plane, and determining parameters of interest from the imaged radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If overfilled metrology is used to enable smaller targets and simultaneous acquisition of multiple sub-targets, then productivity and measurement capability are improved, but measurement precision deteriorates due to edge effects
Solution Approach 1:
The patent applies local quality by using multiple independently controllable illumination beams, each tailored to illuminate a specific sub-target region with optimal parameters. This allows each local area to be illuminated with customized intensity and angular distribution, eliminating edge effects while maintaining overall measurement efficiency across multiple sub-targets simultaneously.
Solution Approach 2:
The illumination system is segmented into multiple independent illumination beams, each dedicated to a specific sub-target or region. This segmentation allows precise control over which areas are illuminated and with what characteristics, enabling accurate measurement of smaller targets without the detrimental edge effects that plague conventional overfilled metrology.
2Productivity
If the illumination beam is expanded to cover multiple sub-targets simultaneously, then productivity is improved, but measurement precision deteriorates due to edge effects from surrounding structures
Solution Approach 1:
The broad illumination beam is segmented into multiple discrete, independently controlled sub-beams, each targeted at a specific sub-target. This segmentation enables simultaneous measurement of multiple targets while preventing edge effects from surrounding structures by ensuring that each sub-target is illuminated only by its dedicated beam, not by spill-over from adjacent regions.
Solution Approach 2:
Each sub-target receives customized local illumination with optimized intensity and angular distribution tailored to its specific characteristics and measurement requirements. This local optimization eliminates the compromise that would be necessary with a single broad beam, allowing each region to be measured with maximum precision while maintaining high productivity through simultaneous multi-point measurement.
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 reduces the impact of edge effects, allowing for accurate and efficient measurement of smaller targets by minimizing the influence of target edges and surrounding structures, thereby improving measurement precision and throughput.
Implementation Method 1
capturing scattered radiation resultant from illuminating the target
Data Source
AI summary
Disclosed is a metrology method. The method comprises illuminating a target comprising one or more sub-targets on a substrate using underfilled illumination such that an illumination beam profile underfills each of said one or more sub-targets; capturing scattered radiation resultant from said illuminating the target; imaging the scattered radiation at a detection image plane to obtain an image; and determining a parameter of interest from the imaged scattered radiation.