Overlay Metrology Scanning for Optical Aberration Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithographic apparatuses suffer from optical aberrations that affect the quality of off-axis images in overlay systems, necessitating improved control of optical aberrations for better image quality and focus.
Innovation Solution
A system comprising an illumination system, scanning system, optical system, detector system, and processor is used to direct and control an optical beam onto a target structure, maintaining alignment with the optical axis during scanning, and analyzing the detected signal beam to determine overlay characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If optical aberrations are present in the overlay system, then the system can operate with simpler optical components, but the image quality and focus deteriorate
Solution Approach 1:
The patent implements a feedback mechanism where the overlay system measures overlay characteristics and this information is fed back to control the optical aberrations. The processor analyzes the signal beam to determine overlay characteristics and uses this feedback to adjust the optical system, creating a closed-loop control system that maintains image quality while managing system complexity.
Solution Approach 2:
The patent changes optical parameters dynamically to control aberrations. By adjusting parameters such as the size of the focal spot and maintaining alignment during scanning, the system adapts the optical characteristics to compensate for aberrations, improving measurement precision without requiring a completely complex optical design.
2Area of stationary object
If the optical beam is scanned to measure overlay characteristics, then the measurement coverage is improved, but optical aberrations affect image quality
Solution Approach 1:
The patent employs dynamic control during scanning operations. The scanning system dynamically adjusts the optical beam parameters while maintaining alignment with the optical axis, allowing the system to cover larger areas through scanning while compensating for aberrations that would otherwise degrade image quality across the measurement coverage area.
3Adaptability or versatility
If off-axis images are used for overlay measurement, then the measurement capability is enhanced, but optical aberrations degrade image quality
Solution Approach 1:
The system uses feedback from the detected signal beam to control and compensate for optical aberrations in off-axis images. The processor analyzes the overlay characteristics from the off-axis measurements and uses this information to adjust the optical system, thereby maintaining the versatility of off-axis imaging while improving image quality through closed-loop control.
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 image quality and focus in overlay systems by effectively controlling optical aberrations, improving the accuracy of overlay measurements.
Implementation Method 1
a signal beam generated from the target structure during scanning of the optical beam. The signal beam comprises at least a scattered beam generated from the target structure
Implementation Method 2
The scanning system scans the optical beam and controls a size of a focal spot of the optical beam onto the target structure
Data Source
AI summary
A system includes an illumination system, a scanning system, an optical system, a detector system, and a processor. The illumination system directs an optical beam to illuminate a target structure. The scanning system scans the optical beam and controls a size of a focal spot of the optical beam onto the target structure. The optical system maintains an alignment with an optical axis of the system during scanning of the optical beam. The detector system detects a signal beam generated from the target structure during scanning of the optical beam. The signal beam comprises at least a scattered beam generated from the target structure. The processor analyzes the detected signal beam to determine an overlay characteristic of the target structure.