Optical Measurement System for Nanostructure Critical Dimension
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Solution Overview
Problem
Current optical methods for measuring critical dimensions of nanostructures, such as OCD and TSOM, are inefficient for non-periodic and isolated nanostructures, requiring mechanical through-focus scanning which is unreliable and time-consuming, especially as nanostructure sizes decrease.
Innovation Solution
An optical measurement system that records a defocused image of a nanostructured surface using a microscope optical system with controlled optical scheme parameters, allowing for CD measurement without mechanical through-focus scanning by inclining the nanostructured surface and using rigorous coupled wave analysis and finite-difference time-domain methods for image calculation and comparison.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mechanical through-focus scanning is used to measure non-periodic and isolated nanostructures, then measurement capability is improved, but measurement reliability and speed deteriorate
Solution Approach 1:
The patent replaces mechanical through-focus scanning with a computational approach. Instead of physically moving the sample or objective lens through multiple focal planes, the system captures a single defocused image and uses rigorous coupled wave analysis (RCWA) and finite-difference time-domain (FDTD) methods to calculate and compare images, thereby determining critical dimensions. This substitution eliminates mechanical complexity and improves reliability while maintaining measurement capability for non-periodic and isolated structures.
Solution Approach 2:
The patent changes the optical parameters of the imaging system by intentionally introducing defocus and inclining the nanostructured surface at a predetermined angle. By controlling these optical parameters and using computational algorithms to analyze the resulting defocused image, the system achieves accurate CD measurement without mechanical scanning. This parameter-based approach improves both reliability and speed while maintaining versatility.
2Adaptability or versatility
If mechanical through-focus scanning is used, then measurement capability is improved, but measurement time increases
Solution Approach 1:
The patent replaces mechanical through-focus scanning with a computational approach. Instead of physically moving the sample or objective lens through multiple focal planes, the system captures a single defocused image and uses rigorous coupled wave analysis (RCWA) and finite-difference time-domain (FDTD) methods to calculate and compare images, thereby determining critical dimensions. This substitution eliminates mechanical complexity and improves reliability while maintaining measurement capability for non-periodic and isolated structures.
Solution Approach 2:
The patent performs preliminary computational work by pre-calculating reference images using RCWA and FDTD methods for various critical dimension values. During actual measurement, the system only needs to capture one defocused image and compare it against the pre-computed reference library, dramatically reducing measurement time. This preliminary action enables rapid productivity while maintaining full measurement capability.
3Reliability
If optical scheme parameters are controlled to record defocused images, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
The patent changes the optical parameters of the imaging system by intentionally introducing defocus and inclining the nanostructured surface at a predetermined angle. By controlling these optical parameters and using computational algorithms to analyze the resulting defocused image, the system achieves accurate CD measurement without mechanical scanning. This parameter-based approach improves both reliability and speed while maintaining versatility.
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 enables accurate and reliable measurement of nanostructure CD without mechanical scanning, improving measurement speed and reliability, and can analyze both periodic and non-periodic structures within a narrower CD range.
Implementation Method 1
measuring a geometric variable with respect to a nanostructure by means of scattered light investigation
Implementation Method 2
optical measurement system for measuring a CD of a nanostructure based on defocus image processing
Data Source
AI summary
An optical measurement system for measuring a critical dimension having a nanostructured surface including a nanostructure formed on a plane. The optical measurement system includes an image recording module including a microscope optical system which records a defocused image having an nonuniform degree of defocusing with respect to the nanostructured surface, an optical scheme parameter control module which sets and outputs to the microscope optical system optical scheme parameters for the microscope optical system, an image calculation module which receives receiving the optical scheme parameters set by the optical scheme parameter control module and calculates an image of the nanostructured surface, and a comparison module which compares the defocused image recorded by the image recording module and the image calculated by the image calculation module.