Wafer Pattern Quality Characterization via Azimuthal Spectra
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Solution Overview
Problem
Current methods for characterizing the quality of printed patterns on semiconductor wafers, such as photolithography, are time-consuming and fail to detect subsurface defects, making them inadequate for high-volume manufacturing.
Innovation Solution
A method involving the measurement of spectra signals at multiple azimuth angles to determine a difference spectrum, which is then analyzed to indicate the quality of the pattern without requiring a model or extraction of quantitative features, using techniques like two-dimensional beam profile reflectometry and machine-learning algorithms to differentiate between defective and non-defective structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CD-SEM imaging is used to characterize pattern quality, then measurement precision is improved, but productivity deteriorates due to time-consuming analysis
Solution Approach 1:
The patent replaces the mechanical/electronic CD-SEM imaging system with an optical scatterometry system. The scatterometry system uses optical scattering patterns to characterize patterns, eliminating the need for time-consuming SEM imaging and manual analysis while maintaining measurement capability through optical means.
Solution Approach 2:
The patent creates a simplified optical copy or representation of the pattern structure through scattering patterns. Instead of directly imaging the pattern with SEM, the system captures optical scattering signatures that encode pattern information, enabling rapid characterization without detailed imaging.
2Loss of information
If CD-SEM measurement is used, then surface pattern information is obtained, but subsurface defect detection capability is lost
Solution Approach 1:
The patent makes the scatterometry system multi-functional by configuring it to detect both surface pattern characteristics and subsurface defects using the same optical measurement apparatus. The system analyzes scattering patterns to extract information about both the printed pattern geometry and underlying substrate defects simultaneously.
Solution Approach 2:
The patent transitions from two-dimensional surface imaging (CD-SEM) to three-dimensional information extraction through optical scattering analysis. The scatterometry measurements provide depth-sensitive information that reveals subsurface defect structures beneath the patterned surface.
3Ease of operation
If manual judgment of grating quality is used, then subjective assessment is performed, but objectivity and consistency deteriorate
Solution Approach 1:
The patent implements automated feedback-based analysis where the scatterometry system captures optical signals, compares them against reference patterns or models, and automatically determines pattern quality metrics. This closed-loop approach replaces subjective manual judgment with objective, consistent automated evaluation.
Solution Approach 2:
The system performs self-characterization by automatically analyzing its own scattering pattern measurements without requiring external manual inspection. The automated algorithm processes the optical data to extract quality metrics, making the system self-sufficient and eliminating human subjectivity.
4Productivity
If high-volume manufacturing requirements are met, then productivity increases, but detailed characterization capability must be reduced
Solution Approach 1:
The patent extracts only the essential quality metrics needed for high-volume manufacturing from the full pattern characterization. The scatterometry system measures scattering patterns and extracts key parameters such as pattern dimensions, uniformity, and defect presence, eliminating the need for complete detailed imaging while maintaining sufficient quality control.
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 rapid and objective characterization of pattern quality, enabling better process yield assessment and detection of subsurface defects in semiconductor wafers, improving manufacturing efficiency.
Implementation Method 1
A plurality of spectra signals are measured from a particular structure of interest at a plurality of azimuth angles from one or more sensors of a metrology system
Implementation Method 2
measuring spectra includes generating a differential model by using two dimensional beam profile reflectometry
Data Source
AI summary
Disclosed are apparatus and methods for characterizing a plurality of structures of interest on a semiconductor wafer. A plurality of spectra signals are measured from a particular structure of interest at a plurality of azimuth angles from one or more sensors of a metrology system. A difference spectrum is determined based on the spectra signals obtained for the azimuth angles. A quality indication of the particular structure of interest is determined and reported based on analyzing the difference spectrum.