Multi-Angle Ellipsometry Optics for Small-Spot Semiconductor Metrology
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Solution Overview
Problem
Current spectroscopic ellipsometer systems face challenges in decoupling SE data for different target characteristics, leading to correlated or insufficient data that hinders accurate determination of target characteristics, especially for complex targets, and often fail to achieve small spot sizes and near-Brewster angles for precise metrology.
Innovation Solution
An ellipsometer apparatus with illumination and collection optics capable of generating and analyzing light at multiple wavelengths and angles of incidence (AOI) and azimuth angles (AZ), using polarization generating and analyzing elements, and apodizers to control spot size and irradiance, allowing for simultaneous or sequential measurement of discrete ranges of AOI and AZ.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional spectroscopic ellipsometer systems are used, then the system structure is simple, but the SE data for different target characteristics becomes correlated and insufficient for accurate determination
Solution Approach 1:
The patent segments the measurement process by implementing multiple discrete angles of incidence (AOI) and azimuth angles (AZ) to illuminate and collect light from the sample. This segmentation of the optical measurement space allows decoupling of SE data for different target characteristics, enabling accurate determination of individual parameters without correlation interference between measurements.
Solution Approach 2:
The patent extends the measurement from conventional single-angle ellipsometry to multi-dimensional measurements by incorporating both AOI and AZ variations. This dimensional expansion in the optical parameter space provides additional independent measurement equations, breaking correlations and enabling precise determination of multiple target characteristics simultaneously.
2Manufacturing precision
If conventional ellipsometry is used, then the system is easy to operate, but small spot sizes and near-Brewster angles cannot be achieved for precise metrology
Solution Approach 1:
The patent implements local quality optimization by using apodization functions tailored to specific AOI ranges. Different apodization profiles are applied to different angular regions to optimize spot size and irradiance distribution locally, enabling precise metrology for small dimension features while maintaining system operability through automated control.
Solution Approach 2:
The patent systematically varies critical parameters including AOI, AZ, wavelength, and apodization profiles to achieve optimal measurement conditions. By changing these parameters across multiple discrete values, the system achieves small spot sizes and near-Brewster angle measurements, enhancing precision for advanced semiconductor metrology applications.
3Measurement precision
If multiple discrete ranges of AOI and AZ are measured, then correlations between target characteristics are broken, but measurement time increases
Solution Approach 1:
The patent implements preliminary action by pre-defining discrete AOI and AZ ranges with corresponding apodization functions before measurement. This preparation allows the system to rapidly switch between pre-configured measurement states, reducing the time penalty associated with multi-angle measurements while maintaining the correlation-breaking benefit of diverse angular sampling.
Solution Approach 2:
The patent employs periodic action by systematically cycling through multiple discrete AOI and AZ ranges in a structured sequence. This periodic measurement approach, combined with apodization optimization, efficiently collects decoupled SE data across different angular dimensions while minimizing total measurement time through optimized sequencing.
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 breaks correlations between target characteristics, enabling improved measurement repeatability and stability, achieving small spot sizes and high sensitivity for precise metrology, particularly for small dimension features and complex targets.
Implementation Method 1
The illumination optics module includes polarization generating optical elements for generating a plurality of polarization states for the illumination beam
Implementation Method 2
spectroscopic ellipsometry (SE) metrology measurements sample the light reflected off metrology targets
Implementation Method 3
An ellipsometer apparatus with illumination and collection optics capable of generating and analyzing light at multiple wavelengths and angles of incidence (AOI) and azimuth angles (AZ), using polarization generating and analyzing elements
Implementation Method 4
collection optics for collecting light at multiple AOI's and multiple AZ's and directing the light to a detector
Implementation Method 5
The detector module is configured to detect the output beam from the sample at the discrete ranges of AOI and/or AZ and the polarization states and generate a plurality of signals based on the output beam
Data Source
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AI summary
An apparatus includes (i) a bright light source for providing an illumination beam at multiple wavelengths selectable with a range from a deep ultraviolet wavelength to an infrared wavelength, (ii) illumination optics for directing the illumination beam towards a sample at selectable sets of angles of incidence (AOI's) or azimuth angles (AZ's) and polarization states to provide spectroscopic ellipsometry, wherein the illumination optics include an apodizer for controlling a spot size of the illumination beam on the sample at each of the selectable AOI/AZ sets, (iii) collection optics for directing an output beam from the sample in response to the illumination beam at each of the selectable AOI/AZ sets and polarization states towards a detector that generates an output signal or image based on the output beam, and (v) a controller for characterizing a feature of the sample based on the output signal or image.