Examination Beam Tilt Calibration Using Height-Shifted Images
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Solution Overview
Problem
Current examination systems face challenges in accurately determining the stray tilt angle of beams used for semiconductor wafer inspection, which affects the precision and uniformity of metrology measurements, and require time-consuming and costly tilt wafer measurements.
Innovation Solution
A method and system that utilizes a target at different height positions to determine the stray tilt angle of an examination beam by analyzing image displacements and height variations, enabling accurate calibration without a tilt wafer, allowing real-time switching between metrology operations and stray tilt angle determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional tilt wafer measurements are used to determine stray tilt angle, then measurement accuracy is improved, but measurement time and cost increase
Solution Approach 1:
The patent creates a virtual copy of the tilt wafer measurement process by using image displacement analysis of a target at different height positions. Instead of physically measuring a tilt wafer, the system analyzes the displacement of a target image across multiple captured images at different heights to compute the stray tilt angle, achieving the same measurement function with reduced time and cost
Solution Approach 2:
The patent replaces the mechanical tilt wafer measurement system with an optical imaging system. Instead of using physical tilt wafers and mechanical measurement apparatus, the system uses an examination system with imaging capabilities to capture target images at different heights and processes these images to determine the stray tilt angle through computational analysis
2Measurement precision
If tilt wafer measurements are performed, then measurement accuracy is improved, but system complexity and cost increase
Solution Approach 1:
The patent replaces the complex physical tilt wafer measurement system with a simplified optical imaging approach. The system uses a standard examination system with imaging capabilities to capture target images at different heights, eliminating the need for specialized tilt wafers and complex measurement apparatus while maintaining measurement accuracy
Solution Approach 2:
The patent makes the examination system multi-functional by enabling it to perform both routine specimen examination and stray tilt angle measurement using the same hardware and imaging capabilities. The system can switch between examining specimens and measuring stray tilt angles by simply changing the target, eliminating the need for separate dedicated measurement equipment
3Productivity
If beam calibration is performed without stray tilt angle determination, then examination speed is improved, but measurement precision deteriorates
Solution Approach 1:
The patent performs stray tilt angle determination as a preliminary calibration step before conducting metrology measurements. By first determining the stray tilt angle using the target images and then using this information to calibrate the beam, the system ensures that subsequent examination measurements are performed with optimized precision while maintaining high examination speed
Solution Approach 2:
The patent implements a feedback mechanism where the stray tilt angle determination results are fed back into the beam calibration process. The system uses the measured stray tilt angle information to adjust and optimize beam alignment, ensuring that the examination system operates at optimal precision levels without sacrificing examination speed
Data Source
AI summary
There are provided systems and methods comprising obtaining a set of images of a target, wherein the set of images has been acquired by an examination system operative to transmit a beam towards the target, wherein a first image of the set of images has been acquired capturing the target at a first height position, and a second image of the set of images has been acquired capturing the target at a second height position, different from the first height position, determining data DΔZ informative of a displacement of the target in the set of images, and using the data DΔZ and data informative of the first and second height positions to determine a stray tilt angle of a beam of the examination system.