Thin-Film Interferometric 3D Measurement With Phase Shift Correction
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Solution Overview
Problem
Existing 3D imaging techniques for semiconductor manufacturing face challenges in accurately measuring features surrounded by transparent layers due to errors caused by variability in optical properties, leading to inaccurate height measurements and profile inconsistencies, which can affect device performance and connectivity.
Innovation Solution
A system and method that utilize interferometric quantitative phase imaging combined with a reflectometer to determine a 3D surface map, correcting it based on the thickness and complex refractive index of transparent thin films or layers, using phase shift correction to account for the optical properties of mixed materials within the field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional 3D imaging techniques are used to measure features surrounded by transparent layers, then measurement speed and field of view are maintained, but measurement accuracy deteriorates due to errors from variability in optical properties
Solution Approach 1:
The patent introduces an intermediary correction process that uses measured thin film thickness and known complex refractive index values to calculate and remove phase shift errors from the interferometric measurements. This intermediary step acts as a mediator between the raw measurement data and the final corrected height map, eliminating measurement errors caused by transparent layers without requiring fundamental changes to the measurement system architecture
Solution Approach 2:
The patent replaces physical/mechanical correction methods with an optical computation-based correction system. Instead of using complex mechanical adjustment mechanisms or physical reference standards, the system uses computational algorithms that process the interferometric phase data along with thin film thickness measurements and refractive index values to mathematically correct the height measurements, thereby improving accuracy without increasing mechanical complexity
2Measurement precision
If thin film thickness correction is applied to interferometric measurements, then measurement accuracy improves, but processing time and computational complexity increase
Solution Approach 1:
The patent performs preliminary measurements of thin film thickness using a reflectometer before conducting the interferometric height measurements. By obtaining the thickness data in advance, the correction process can proceed efficiently without requiring iterative measurements or repeated scans, thereby reducing overall processing time while maintaining high measurement accuracy
Solution Approach 2:
The patent transforms the correction problem from a complex spatial-domain computation to a more efficient frequency-domain or algebraic solution by changing the computational parameters. The correction algorithm uses the measured thickness and known refractive index to directly calculate phase shift corrections, avoiding time-consuming iterative optimization processes and enabling rapid correction of height measurements
3Measurement precision
If multiple measurements are taken to account for optical property variability, then measurement accuracy improves, but productivity decreases due to increased measurement time
Solution Approach 1:
The patent creates a universal correction algorithm that can be applied to all interferometric measurements of features surrounded by transparent layers, regardless of specific layer thickness or refractive index variations. This multi-functional correction approach eliminates the need for separate measurement sequences or repeated scans under different conditions, thereby maintaining high productivity while achieving consistent high accuracy across all measurements
Solution Approach 2:
The patent implements a feedback mechanism where the measured thin film thickness and the corrected height measurements are used to validate and refine the correction algorithm. This feedback loop ensures that the correction process adapts to actual measurement conditions without requiring multiple preliminary measurements, thereby maintaining both high accuracy and fast throughput in manufacturing environments
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
Enables precise 3D measurements of features with improved accuracy, reducing measurement errors by up to 100% and ensuring consistent height and profile measurements, enhancing yield and connectivity in semiconductor manufacturing.
Implementation Method 1
an interferometric quantitative phase imaging technique is used to measure a 3D surface map
Implementation Method 2
a reflectometer is used to measure a thickness and a complex refractive index of the transparent thin film
Data Source
AI summary
A 3D surface map of a workpiece is determined using an interferometric quantitative phase imaging technique. The workpiece includes a transparent thin film or layers stack. The 3D surface map is corrected based on a thickness and a refractive index of the transparent thin film or layers stack. This technique can be used with an inspection system configured to perform an interferometric quantitative phase imaging.