Ellipsometer Apodizer for Decoupled Semiconductor Metrology
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Solution Overview
Problem
Current spectroscopic ellipsometry systems face challenges in decoupling SE data for different target characteristics, leading to correlated or insufficient data that hinders accurate determination of semiconductor wafer characteristics, especially for complex targets, and often fail to provide small spot sizes and near-Brewster angles for high sensitivity metrology applications.
Innovation Solution
The development of an ellipsometer apparatus that includes illumination and collection optics capable of providing illumination beams at multiple wavelengths and angles of incidence (AOI) and azimuth angles (AZ), with polarization generating and analyzing components, and apodizers to control spot size and irradiance, allowing for simultaneous or sequential measurement at discrete ranges of AOI and AZ to break correlations and improve measurement precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional spectroscopic ellipsometry systems are used to measure semiconductor wafer characteristics, then measurement data can be obtained, but the data for different target characteristics remain correlated and insufficient, hindering accurate determination
Solution Approach 1:
The patent segments the measurement process by measuring SE data at multiple discrete angles of incidence (AOI) and azimuth angles (AZ) separately. This segmentation allows the data for different target characteristics to be decoupled, as each measurement at a specific angle provides independent information about different sample properties, transforming correlated data into independent measurements.
Solution Approach 2:
The patent adds angular dimensions (AOI and AZ) to the traditional spectral measurement dimensions. By measuring at multiple discrete angles rather than only at a single angle, the system transitions from one-dimensional spectral data to multi-dimensional data that includes angular information, enabling better decoupling of target characteristics.
2Measurement precision
If conventional ellipsometry systems measure at a single angle of incidence, then the measurement process is simple, but they fail to provide small spot sizes and near-Brewster angles for high sensitivity applications
Solution Approach 1:
The patent divides the angular measurement space into multiple discrete AOI and AZ measurements. Each discrete angle measurement can be performed with dedicated optical paths, allowing optimization for specific sensitivity requirements while maintaining manageable system complexity through modular design.
Solution Approach 2:
The patent employs dynamic or adjustable optical elements (such as programmable aperture masks or adjustable mirrors) that can be reconfigured to select different discrete angles of incidence and azimuth angles. This dynamic capability allows the system to adapt to different measurement requirements without requiring a completely different optical setup for each angle.
3Loss of information
If multiple angles of incidence and azimuth angles are measured simultaneously, then data decoupling is improved, but the device complexity and optical path requirements increase significantly
Solution Approach 1:
The patent merges the illumination and collection optical paths into a single integrated system that can perform multiple measurements. By combining the optical paths and using shared components (such as a single light source and detector system), the patent reduces the overall complexity compared to having separate optical paths for each angle measurement.
Solution Approach 2:
The patent designs a universal measurement system that can perform multiple SE measurements at different angles using the same basic optical hardware. The system uses programmable optical elements (such as spatial light modulators or programmable aperture masks) that can be reconfigured to perform different angle measurements without requiring physical reconfiguration of the entire optical path.
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 enhances measurement repeatability and stability by enabling improved decoupling of SE data, achieving small spot sizes, and providing high sensitivity across a wide range of wavelengths, thereby accurately determining semiconductor wafer characteristics.
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
the collection optics module includes polarization analyzing optical elements for analyzing the polarization state of the output beam
Implementation Method 3
The illumination optics module and collection optics module include reflective optical elements between the polarization generating optical elements and the polarization analyzing optical elements
Data Source
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.