2θ Optical Scatterometry for Semiconductor Metrology
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Solution Overview
Problem
Current metrology techniques, such as scanning electron microscopes and atomic-force microscopes, face challenges in providing fast, non-destructive, and high-resolution measurements for in-line monitoring of semiconductor manufacturing processes, especially at nanoscale dimensions, while existing scatterometry methods are often too slow and incompatible with roll-to-roll manufacturing processes.
Innovation Solution
A 2θ scatterometry system that uses a laser source to produce a polarized optical beam, focusing it with a first numerical aperture (NA1) and sweeping the angle of incidence across a range of angles with a second NA2, allowing for rapid measurement of reflectivity changes, integrated into a roll-to-roll manufacturing tool to provide real-time metrology data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scanning electron microscope is used for dimensional metrology, then measurement precision is improved, but measurement speed deteriorates and vacuum environment requirement increases device complexity
Solution Approach 1:
The patent replaces mechanical scanning systems (SEM/AFM) with an optical measurement system that uses light scattering principles. The optical system captures scattered light patterns from periodic structures and uses computational algorithms to extract dimensional information, eliminating the need for mechanical scanning and vacuum environments while maintaining nanoscale measurement precision and achieving measurement speeds compatible with high-speed manufacturing processes
2Area of stationary object
If atomic-force microscope is used for full wafer measurement, then areal coverage is improved, but measurement speed deteriorates and tip robustness issues arise
Solution Approach 1:
The patent replaces the mechanical AFM tip-scanning system with a non-contact optical system that illuminates the entire wafer surface with light. The scattered light patterns are captured by a camera and processed to extract dimensional information across the full wafer area simultaneously, achieving both complete areal coverage and high measurement speeds without mechanical wear or tip robustness issues
Solution Approach 2:
The patent transitions from one-dimensional mechanical tip scanning to two-dimensional parallel optical measurement. By capturing the entire scattered light field from the wafer surface simultaneously and using computational algorithms to process the spatial information, the system achieves full wafer coverage at high speeds without the sequential scanning limitations of mechanical systems
3Measurement precision
If ellipsometric scatterometry is used, then sensitivity to nanoscale features is improved, but measurement time increases due to broadband source requirements
Solution Approach 1:
The patent changes the illumination parameters by using coherent light sources (lasers) at specific wavelengths instead of broadband incoherent sources. This allows for faster measurement speeds while maintaining sensitivity to nanoscale features through the use of coherent light interference patterns and computational analysis of the scattered light field
Solution Approach 2:
The patent adds the dimension of spatial coherence to the measurement approach. By using coherent laser sources and capturing the full spatial coherence information in the scattered light field with a camera, the system achieves rapid measurements without sacrificing nanoscale sensitivity that would otherwise require time-consuming broadband spectral measurements
4Productivity
If angular scatterometry with laser source is used, then measurement speed is improved, but knowledge of optical properties at single wavelength limits measurement precision
Solution Approach 1:
The patent compensates for the single-wavelength limitation by adding spatial dimension information. The coherent scattered light field contains rich spatial coherence information that, when captured and processed, provides additional constraints for accurate dimensional measurement even at a single wavelength, maintaining measurement precision while achieving high speeds
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 fast, non-destructive, and high-resolution metrology measurements compatible with roll-to-roll manufacturing speeds, providing essential data for monitoring and quality control in semiconductor fabrication without disrupting the manufacturing process.
Implementation Method 1
focusing the optical beam with a first NA1 on a sample surface and to sweep the angle of incidence across a range of angles with an approximately fixed focal position on a sample surface with a second NA2
Implementation Method 2
receive the optical beam reflected from the sample surface
Implementation Method 3
control the polarization of the optical beam
Implementation Method 4
2θ scatterometry, a noncontact optical measurement of the reflectivity of a structured pattern on a wafer
Data Source
AI summary
A system for measuring a periodic array of structures on a sample is provided. The system includes an optical source configured to produce an optical beam; an optical system configured to control the polarization of the optical beam and to focus the optical beam with a first NA1 on a sample surface and to sweep the angle of incidence across a range of angles with an approximately fixed focal position on a sample surface with a second NA2 wherein NA2>NA1; additional optical components configured to receive the optical beam reflected from the sample surface and to focus the reflected beam onto a detector; and a recording system to record the reflectivity of the sample surface as a function of the angle of incidence.