Interferometric PSS Measurement via Statistical Fringe Order Correction
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Solution Overview
Problem
Conventional vertical-scanning interferometry struggles to accurately measure the width and height of patterned sapphire substrate features due to fringe-order errors and batwing artifacts, especially in transition zones with steep slopes, leading to imprecise dimensions and reduced measurement reliability in production environments.
Innovation Solution
A statistical approach is employed to determine the correct fringe order of phase data by utilizing the best available height and phase maps, particularly around the peaks of features, and calculating an offset based on geometric assumptions to correct fringe-order errors, thereby improving the accuracy of feature width and height measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional vertical-scanning interferometry is used to measure PSS features, then measurement speed is improved, but measurement precision deteriorates due to fringe-order errors and batwing artifacts in transition zones
Solution Approach 1:
The patent introduces an intermediary statistical analysis process that mediates between the interferometric phase data and the final height measurements. By using statistical methods to determine fringe order and correct batwing artifacts, the system bridges the gap between rapid interferometric scanning and precise dimensional measurement, achieving both speed and accuracy
Solution Approach 2:
The patent replaces the conventional mechanical approach of sequential measurement with a computational/statistical system. Instead of physically adjusting measurement parameters or using multiple measurement systems, the invention uses statistical algorithms to process interferometric data, correcting fringe-order errors and batwing artifacts through mathematical operations rather than mechanical adjustments
2Measurement precision
If statistical approach is used to correct fringe-order errors, then measurement precision is improved, but processing complexity increases
Solution Approach 1:
The statistical analysis system performs self-correction of measurement errors without external intervention. The algorithm automatically identifies and corrects fringe-order errors and batwing artifacts through intrinsic statistical properties of the interferometric data, eliminating the need for complex external calibration systems or manual correction procedures
Solution Approach 2:
The patent changes the statistical parameters of the data processing approach by using probability distributions and statistical inference to determine fringe order. This parameter-based statistical approach simplifies the processing complexity compared to deterministic methods, as it leverages the inherent statistical nature of interferometric measurements to achieve correction
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 method enhances the precision and reliability of measuring patterned sapphire substrate features, reducing batwing artifacts and achieving consistent results comparable to atomic force microscopy, with improved repeatability and accuracy for quality control in high-volume production.
Implementation Method 1
Optical interferometric profilometry is a proven method for measuring and monitoring HB-LED wafer surfaces rapidly and repeatably in three-dimensional (3D) detail
Implementation Method 2
phase-shifting interferometry (PSI) techniques with conventional white-light vertical scanning
Data Source
AI summary
A patterned sapphire substrate is measured from a fine phase map and a coarser height map of the sample. The boundaries of the PSS features are identified by finding the locations of minimum contrast in the modulation map of the substrate and are used to produce a height map of the substrate base and a phase map of center regions of the features. A fringe-order map of the features with respect to the base is used to identify the most prevalent fringe order of pixels in the center-regions of the features. That fringe order is adopted as the correct offset between corresponding pixels in the phase map of the center regions of the features and the base of the substrate. A complete map of the substrate is thus obtained by combining the phase map of the features with the height map of the substrate with an offset equal to the fringe order produced by the invention.