Optical Wafer Surface Inspection Tool for Non-Destructive Roughness Measurement
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Solution Overview
Problem
Conventional methods for measuring surface roughness of wafers with patterns are either destructive, inaccurate due to pattern steps, or require manual visual search, making it difficult to achieve high accuracy and non-destructive measurement.
Innovation Solution
A surface inspection tool and method that measures scattering light intensity to automatically identify and set an inspection range for accurate surface roughness measurement without visual search, using a controller to extract measurement coordinates with sufficient scattering light intensity and define the inspection range around pattern peripheries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FIB process is used to measure surface roughness, then measurement accuracy is improved, but the wafer is destroyed and cannot be used for manufacturing
Solution Approach 1:
The patent replaces the mechanical FIB process with an optical measurement system that uses laser light to measure surface roughness. The optical method calculates surface roughness from scattered light intensity patterns without physical contact or destruction of the wafer surface, thus eliminating the harmful effect of wafer destruction while maintaining measurement accuracy.
2Object-affected harmful factors
If AFM is used to measure surface roughness, then non-destructive measurement is achieved, but measurement accuracy is degraded due to pattern steps
Solution Approach 1:
The patent extracts and eliminates the harmful factor of pattern steps from the measurement process by using optical scattering measurement. Instead of physically contacting the surface (which picks up step information), the optical method measures only the scattering characteristics caused by surface roughness, effectively separating the measurement of surface roughness from the presence of pattern steps.
Solution Approach 2:
The patent introduces scattered light intensity as an intermediary parameter to measure surface roughness. Rather than directly measuring surface height (which is affected by pattern steps), the optical method uses the intensity of scattered light as a mediator that reflects surface roughness characteristics without being influenced by pattern steps.
3Object-affected harmful factors
If scattering light method is used to measure surface roughness, then non-destructive measurement is achieved, but measurement accuracy is degraded due to pattern step noise
Solution Approach 1:
The patent applies local quality analysis by measuring scattering light intensity at multiple local positions across the wafer surface and analyzing the spatial distribution of these measurements. By examining the local scattering characteristics at different positions, the method can distinguish between surface roughness variations and pattern step effects, improving measurement accuracy while maintaining non-destructive measurement.
4Measurement precision
If visual search is used to find flat inspection range, then measurement can be performed, but measurement time is increased and automation is lost
Solution Approach 1:
The patent implements self-service automation where the optical measurement system automatically identifies and selects appropriate inspection positions without human intervention. The system autonomously analyzes scattered light intensity patterns, determines flat regions suitable for measurement, and performs the measurement sequence automatically, eliminating the need for manual visual search and significantly reducing inspection time.
Solution Approach 2:
The patent uses feedback mechanisms where the optical system continuously monitors scattered light intensity during the scanning process and uses this information to identify flat regions. The system feeds back the scattering intensity data to automatically determine suitable measurement positions and adjust the inspection sequence, enabling automated operation without manual search.
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 high-accuracy, non-destructive measurement of surface roughness on wafers with patterns, reducing measurement time and improving yield by automating the search for flat inspection areas.
Implementation Method 1
measuring, by the optical wafer surface inspection tool, scattering light intensity of scattering light generated by irradiated irradiation light
Data Source
AI summary
An object of the present invention is to provide a surface inspection tool in which a flat inspection range capable of measuring surface roughness of a wafer with patterns with high accuracy and in a nondestructive manner can be searched without visual search. In order to solve the object, in a surface inspection tool 110 which measures scattering light intensity of scattering light generated by irradiated irradiation light in association with a measurement coordinate on a wafer 200 with patterns and inspects the surface roughness of the wafer 200, the surface inspection tool includes a controller 250 which extracts measurement coordinate of the measured scattering light intensity that is equal to or more than a lower limit threshold L, sets an inspection range 406 of the surface roughness inspection in a partial layout 405a of a part of the whole layout 401 of the pattern corresponding to the periphery of the extracted measurement coordinate, and obtains the surface roughness in the inspection range 406.