Spectroscopic Ellipsometry With Detector Resolved Numerical Aperture
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Solution Overview
Problem
Current optical metrology techniques struggle to accurately measure critical dimensions and film thickness of high aspect ratio semiconductor structures due to low signal-to-noise ratios and inadequate penetration of illumination light, particularly in structures with opaque layers and deep depths, limiting their ability to meet throughput and precision requirements.
Innovation Solution
Implementing spectroscopic ellipsometry with angle-resolved detection, which subdivides the collection numerical aperture (NA) into multiple subranges at the detector, enabling high spectral resolution and sensitivity for measurements of deep structures, using coherent and incoherent illumination sources to enhance signal intensity and reduce measurement time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical metrology techniques are used to measure deep semiconductor structures, then measurement capability is provided, but signal-to-noise ratio is low and measurement precision deteriorates
Solution Approach 1:
The collection NA is segmented into multiple discrete sub-NA ranges, with each subrange detected by separate detector regions. This segmentation allows the system to resolve specific angular information from deep structures, improving signal discrimination and measurement precision while maintaining reliable detection through systematic analysis of multiple angular components
Solution Approach 2:
The patent adds the angular dimension (NA resolution) to the traditional spectral measurement. By resolving collection NA into discrete sub-NA ranges and detecting them separately, the system transforms a 1D spectral measurement into a 2D measurement (wavelength + angle), providing additional information dimensions that improve both precision and reliability for deep structure characterization
2Measurement precision
If conventional spectroscopic ellipsometry is used, then spectral measurement is provided, but spectral resolution is insufficient for deep structures
Solution Approach 1:
The detection system segments the collection NA into multiple discrete sub-NA ranges, with each subrange directed to separate detector regions. This segmentation achieves high spectral resolution by angularly resolving reflected light from deep structures, while the modular detector design manages system complexity through systematic spatial arrangement of detection elements
Solution Approach 2:
The system employs dynamic optical elements including a rotating compensator and variable NA control to adapt the detection configuration. These dynamic components allow the system to optimize between spectral resolution and measurement speed, adjusting the collection NA and compensation parameters based on the specific measurement requirements of different deep structures
3Productivity
If measurement time is reduced to increase throughput, then productivity is improved, but measurement precision deteriorates
Solution Approach 1:
The system uses periodic modulation of the polarization state through a rotating compensator, which cycles through different angular positions to encode structural information. This periodic action allows rapid data collection that can be processed to achieve high precision measurements in reduced time, improving throughput without sacrificing measurement quality
Solution Approach 2:
The system maintains continuous illumination and detection during measurement, with the rotating compensator continuously modulating the polarization state. This continuous operation eliminates idle time between measurements, maintaining high productivity while the continuous angular modulation ensures sufficient data quality for precise critical dimension extraction
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 allows for precise critical dimension, shape, and film thickness measurements of complex semiconductor structures with high throughput, overcoming limitations of existing methods by achieving small measurement box sizes and improved spectral resolution across a wide range of wavelengths.
Implementation Method 1
an amount of illumination light is directed from an illumination source to a measurement spot on a surface of a specimen under measurement
Implementation Method 2
an amount of collected light is collected from the measurement spot on the surface of the specimen under measurement over a range of collection angles
Implementation Method 3
the collected light is dispersed according to wavelength across one direction of a surface of a detector
Implementation Method 4
the detector resolves the collected light into discrete wavelengths on the surface of the detector along a first direction and according to collection angle along a second direction perpendicular to the first direction
Implementation Method 5
spectroscopic ellipsometry with angle-resolved detection, which subdivides the collection numerical aperture (NA) into multiple subranges at the detector
Data Source
AI summary
Methods and systems for performing spectroscopic ellipsometry measurements of semiconductor structures with a collection NA resolved at the detector are presented herein. The collection NA defines a small measurement box size. Resolving the collection NA at the detector dramatically increases measurement sensitivity. In some examples, the collection NA is subdivided into 50-100 subranges at the detector. In some embodiments, a spectroscopic ellipsometer employing angle-resolved detection of the collection NA includes a coherent illumination source with high spectral intensity across a range of wavelengths from 400 nanometers to 2,500 nanometers. In some embodiments, the illumination beam is scanned over the surface of the specimen under measurement at high frequency during measurement. Spectroscopic ellipsometry measurements with detector resolved collection NA enable critical dimension, shape and profile measurements, and film measurements of deep structures fabricated in accordance with current semiconductor fabrication nodes and those contemplated for fabrication at future semiconductor fabrication nodes.