Ellipsometry System Rotating Compensator Spatial Resolution
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Solution Overview
Problem
Current spectroscopic ellipsometry systems have limited spatial resolution and wafer coverage, which are insufficient for the precise characterization of thin films in semiconductor manufacturing, particularly as transistor dimensions shrink, leading to challenges in process control and quality assessment.
Innovation Solution
A combined spectroscopic and imaging ellipsometry system using a rotating compensator and spatial separator allows for simultaneous collection of high spatial resolution data at multiple spectral bandwidths, enhancing measurement performance by converting linearly polarized illumination into a range of polarization states and utilizing a spatial positioner for precise sample positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a measurement beam with diameter ranging from 2 mm to 50 μm is used for spectroscopic ellipsometry measurements, then the measurement sensitivity and reproducibility are maintained, but the lateral resolution is limited and the measurement time increases, reducing effective wafer coverage
Solution Approach 1:
The patent divides the measurement process into two distinct modes: imaging ellipsometry mode for rapid wafer-wide mapping and spectroscopic ellipsometry mode for detailed spectral analysis. This segmentation allows the system to achieve both high productivity through fast imaging mode and high measurement precision through dedicated spectroscopic mode, eliminating the trade-off between speed and accuracy
Solution Approach 2:
The patent implements a dynamic measurement system that can switch between different measurement modes (imaging and spectroscopic) based on the specific requirements. The system dynamically adjusts the measurement beam diameter and acquisition parameters to optimize for either speed or precision depending on the operational context, thereby achieving both high wafer coverage and high measurement sensitivity
2Manufacturing precision
If the measurement spot size is reduced to about 50 μm or smaller to improve lateral resolution, then the spatial resolution increases, but the measurement time increases and the effective wafer coverage decreases
Solution Approach 1:
The patent segments the measurement function into imaging ellipsometry for rapid low-resolution screening and spectroscopic ellipsometry for high-resolution detailed measurement. This allows the system to perform fast wafer-wide mapping with larger spot sizes, then focus detailed high-resolution measurements only on regions of interest, thereby achieving high spatial resolution without proportionally increasing total measurement time
Solution Approach 2:
The patent applies partial action by performing comprehensive wafer mapping at lower resolution first, then applying excessive action by conducting detailed high-resolution measurements only on specific regions of interest rather than the entire wafer. This selective approach achieves high spatial resolution where needed while maintaining overall productivity
3Measurement precision
If point-by-point mechanical scanning is used to obtain wafer maps, then the measurement accuracy is maintained, but the measurement speed decreases and wafer coverage is limited
Solution Approach 1:
The patent replaces the mechanical scanning system with an optical imaging system that uses a camera detector to capture entire wafer maps simultaneously. This substitution eliminates mechanical movement and achieves rapid wafer-wide coverage while maintaining measurement accuracy through the imaging ellipsometry technique, which captures all measurement points in parallel rather than sequentially
4Productivity
If single-wavelength ellipsometry is used to increase measurement speed, then the productivity improves, but the information content and measurement precision decrease
Solution Approach 1:
The patent segments the spectral measurement into multiple discrete wavelengths, where imaging ellipsometry is performed at each wavelength point. This segmentation allows the system to maintain high speed by using discrete wavelength points rather than continuous spectral scanning, while still gathering sufficient spectral information for accurate thin film characterization through the combined multi-wavelength data set
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 significantly increases the information content and measurement speed, providing high-speed, accurate, and reproducible results with improved spatial resolution and sample coverage, overcoming the limitations of individual spectroscopic and imaging ellipsometry techniques.
Implementation Method 1
a rotating compensator... configured to convert linearly polarized illumination light into a range of polarization states by rotating at a known angular velocity
Implementation Method 2
a beam splitter configured to spatially separate the reflected light into different paths
Implementation Method 3
Ellipsometry is based on change in polarization state of specularly reflected light. From analysis of such polarization changes it is possible to deduce the properties of the reflecting surface.
Implementation Method 4
Thin Film Interference methodologies of characterization are based on a natural phenomenon in which light waves reflected by the upper and lower boundaries of a thin film interfere with one another, either enhancing or reducing the irradiance of reflected/transmitted light.
Data Source
AI summary
An imaging spectroscopic ellipsometry apparatus and method configured to measure thin films with high spatial resolution. The apparatus includes a rotating compensator that enables to simultaneously collect both spectrometric ellipsometric data and ellipsometric imaging with the use of the same measurement beam of light. Collecting both data sets simultaneously increases the information content for analysis and affords a substantial increase in measurement performance.