Optical Measuring System for Nanostructure Critical Size
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Solution Overview
Problem
Current optical measuring methods for nanostructures, such as OCD and TSOM, are inefficient for non-periodic and small-sized structures, requiring mechanical scanning which is unreliable and slow, especially as critical sizes approach 20 nanometers, necessitating a more precise and rapid measurement technique.
Innovation Solution
An optical measuring system that processes defocused images without mechanical scanning, utilizing a module to adjust and monitor optical scheme and illumination parameters, and records images at various defocusing levels using a radiation source with adjustable wavelengths, allowing for precise measurement of nanostructure critical sizes without mechanical shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mechanical scanning is used to capture defocused images at various focus positions, then measurement capability for non-periodic structures is achieved, but system reliability decreases and measurement speed is reduced
Solution Approach 1:
The patent replaces the mechanical scanning system with a computational approach. Instead of physically moving the sample or objective lens to capture defocused images, the system uses a single in-focus image and applies digital image processing algorithms to simulate defocused images at various z-positions. This substitution eliminates mechanical wear, positioning errors, and vibration issues while maintaining the ability to analyze non-periodic structures.
Solution Approach 2:
The patent creates virtual copies of defocused images through computational processing. Rather than capturing actual optical defocused images through mechanical scanning, the system generates synthetic defocused image copies from a single in-focus image using point spread function convolution and other image processing techniques. These virtual copies enable the same measurement capabilities without mechanical movement.
2Adaptability or versatility
If mechanical scanning is used to capture defocused images, then through-focus analysis is enabled, but measurement speed decreases
Solution Approach 1:
The patent performs preliminary computational processing to generate all necessary defocused image variants from a single in-focus image. By pre-calculating the point spread functions and convolution results for multiple z-positions, the system enables rapid through-focus analysis without the time-consuming mechanical scanning process. The computational models are prepared in advance, allowing quick comparison and measurement.
Solution Approach 2:
The patent replaces time-consuming mechanical scanning with fast computational image processing. Digital operations can be performed much faster than mechanical systems can physically move and capture images, thereby dramatically increasing measurement speed while maintaining through-focus analysis capability.
3Measurement precision
If mechanical scanning with high precision is used, then measurement precision for small critical sizes is improved, but system complexity and vulnerability increase
Solution Approach 1:
The patent replaces complex mechanical scanning systems with simpler computational processing. Instead of requiring precision mechanical stages, vibration isolation, and positioning control systems, the invention uses digital image processing algorithms that can achieve the same measurement precision through software-based focus variation analysis.
Solution Approach 2:
The patent creates virtual defocused image copies through computational methods, eliminating the need for physical scanning mechanisms. These synthesized images maintain the optical information needed for precise critical size measurement without requiring complex mechanical positioning systems.
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
Enables accurate measurement of nanostructure critical sizes across a wide range of objects, including non-periodic ones, by optimizing image comparison and calculation methods, thereby improving precision and speed in semiconductor production.
Implementation Method 1
The OCD method is based on the dependence of the reflectivity factor of a subundular structure on the CS, on the wavelength and the sight angle of the incident radiation
Implementation Method 2
a defocusing module (104) configured to defocus the optical image
Data Source
AI summary
Optical measuring systems for measuring geometrical parameters of nano-objects and methods of measuring a critical size (CS) are provided. The optical method of measuring the CS includes selecting parameters of an optic scheme and an illumination condition; recording a set of nanostructure images corresponding to various wavelengths with various defocusing levels of scattered radiation; calculating a plurality of sets of images of a nanostructure with various defocusing levels, corresponding to various wavelengths of the scattered radiation with CS values within a known range; and comparing a set of measured images of the nanostructure with the sets of the calculated images and determining a best approximate value of the CS values.