Substrate Inspection AOI Distortion Correction Using Reflectance Maps
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Solution Overview
Problem
Optical-based substrate inspecting apparatuses face issues with angle of incidence (AOI) distortion due to variations in light source, optical system, and substrate stage distortions, leading to non-uniformity in field of view (FOV) and inaccurate substrate surface characterization.
Innovation Solution
The apparatus includes a light source, illumination and imaging optical systems, a light detector, and a processor to detect and correct AOI distortion by generating standard and measured reflectance distribution data, calculating AOI distribution, and correcting distortions using reference AOI values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical-based substrate inspection is performed using conventional methods, then substrate surface characteristics can be investigated, but angle of incidence distortion occurs due to light source, optical system, and stage distortions
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction values for angle of incidence distortion in a lookup table before actual substrate inspection. The system characterizes the distortion properties of the light source, optical system, and stage in advance, then uses these pre-computed correction values during measurement to compensate for AOI distortion without requiring real-time complex calculations
Solution Approach 2:
The patent introduces an intermediary correction mechanism by inserting a lookup table between the raw measurement data and the final analysis results. This lookup table contains pre-computed angle of incidence correction values that mediate the distorted optical paths and convert them into accurate measurement data, effectively decoupling the distortion sources from the measurement process
2Measurement precision
If distortion correction is implemented through complex calculations, then measurement accuracy improves, but processing time and computational resources increase
Solution Approach 1:
The patent pre-calculates angle of incidence distortion correction values for various field of view positions and stores them in a lookup table before actual substrate inspection. During measurement, the system simply retrieves pre-computed correction values based on pixel coordinates rather than performing complex real-time calculations, dramatically reducing processing time while maintaining correction accuracy
Solution Approach 2:
The patent creates a simplified computational model by copying the distortion characteristics into a lookup table structure. Instead of repeatedly performing complex optical path calculations during measurement, the system uses this copied representation of distortion data to quickly apply corrections through simple table lookups and interpolations
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 substrate inspection by minimizing measurement errors and accurately measuring surface characteristics like film thickness, while providing alarms for significant distortions.
Implementation Method 1
a light source configured to generate incident light
Implementation Method 2
an illumination optical system configured to form an optical path of the incident light
Implementation Method 3
an imaging optical system configured to form an optical path of reflected light reflected from a substrate
Implementation Method 4
a light detector configured to receive the reflected light and convert the received reflected light into an electrical signal
Data Source
AI summary
Proposed is a substrate inspecting apparatus and an operating method of the substrate inspecting apparatus capable of detecting and correcting angle of incidence (AOI) distortion occurring during an optical-based substrate inspection process. The substrate inspecting apparatus includes a light source generating incident light, an illumination optical system forming an optical path of the incident light, an imaging optical system forming an optical path of reflected light reflected from a substrate, a light detector that receives the reflected light and converts the received reflected light into an electrical signal, and a processor that generates a spectral image from the electrical signal.