Inferring Local Uniformity Metrics via Diffraction Intensity
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Solution Overview
Problem
Current methods for measuring local contributors to edge placement errors (EPE) in lithographic processes, such as CD-SEM inspection, are too slow for practical applications, necessitating a faster method for monitoring parameters like local overlay, local CD uniformity, Line Edge Roughness, and Line Width Roughness.
Innovation Solution
A method and apparatus that utilize intensity data from diffraction orders to infer local uniformity metrics, involving the measurement of intensity distributions and differences between complementary diffraction orders, processed by a computer program to control metrology apparatus, enabling faster monitoring of EPE and related parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CD-SEM inspection is used to measure local contributors to edge placement errors, then measurement precision is improved, but productivity deteriorates due to slow measurement speed
Solution Approach 1:
The patent replaces the mechanical scanning electron microscope (CD-SEM) inspection system with an optical scatterometry-based measurement system. This substitution uses light diffraction and scattering phenomena to measure local uniformity metrics, achieving both high measurement precision and fast measurement speeds, thereby resolving the contradiction between measurement precision and productivity
Solution Approach 2:
The patent changes the measurement parameters by using multiple wavelengths of radiation and analyzing multiple diffraction orders simultaneously. This parameter change enables the system to extract multiple local uniformity metrics (LCDU, LOVL, LER, LWR) from a single rapid measurement, maintaining high precision while dramatically improving measurement speed and productivity
2Loss of information
If multiple local uniformity metrics are measured simultaneously, then information completeness is improved, but measurement complexity increases
Solution Approach 1:
The patent implements a universal measurement system that can simultaneously measure multiple local uniformity metrics (LCDU, LOVL, LER, LWR) using a single scatterometry apparatus. The system uses multiple wavelengths and analyzes multiple diffraction orders to extract all required metrics from one measurement, achieving information completeness without proportionally increasing device complexity
Solution Approach 2:
The patent performs preliminary calibration and establishes lookup tables that correlate scatterometry measurements with local uniformity metrics. This preliminary action enables the system to rapidly infer multiple metrics from raw intensity data without complex real-time calculations, reducing measurement complexity while maintaining information completeness
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 faster measurement of local EPE and uniformity metrics, allowing for wafer-to-wafer monitoring, thereby improving manufacturing efficiency and reducing the need for slow SEM measurements.
Implementation Method 1
These devices direct a beam of radiation onto a target and measure one or more properties of the scattered radiation... to obtain a diffraction 'spectrum' from which a property of interest of the target can be determined
Data Source
AI summary
A method of inferring a value for at least one local uniformity metric relating to a product structure, the method including: obtaining intensity data including an intensity image relating to at least one diffraction order obtained from a measurement on a target; obtaining at least one intensity distribution from the intensity image; determining, from the at least one intensity distribution, an intensity indicator expressing a variation of either intensity over the at least one diffraction order, or a difference in intensity between two complimentary diffraction orders over the intensity image; and inferring the value for the at least one local uniformity metric from the intensity indicator.