Inspection Apparatus Luminance Correction for Mask Defect Detection

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Solution Overview

Problem

In semiconductor device manufacturing, the detection of defects in masks is hindered by luminance differences between reference and inspection images, leading to inaccurate estimation of position gaps and spatial distortions, resulting in false defect detection.

Innovation Solution

An inspection apparatus that extracts correlated luminance change regions between reference and inspection images, corrects luminance in these regions, and estimates shift and distortion amounts using SSD matching and polynomial equations to improve defect detection precision.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If luminance correction is performed on the reference image, then measurement precision of position gap and distortion is improved, but device complexity increases due to additional processing steps

Engineering Contradiction:

Improveposition gap and distortion estimation accuracyVSAvoidimage processing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies luminance correction to the reference image before performing defect detection comparison. By pre-processing the reference image to match the luminance characteristics of the inspection image, the system eliminates luminance-related false defects and improves measurement precision without requiring complex real-time adjustments during comparison

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces complex mechanical or hardware-based luminance matching systems with software-based image processing algorithms. The luminance correction is achieved through computational methods including histogram matching and adaptive filtering, substituting physical luminance adjustment mechanisms with digital signal processing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If luminance correction is applied to eliminate false defects, then reliability of defect detection is improved, but loss of time increases due to additional correction processing

Engineering Contradiction:

Improvedefect detection accuracyVSAvoidinspection processing time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The luminance correction is performed as a pre-processing step on the reference image before the actual defect detection begins. This preliminary action ensures that when the comparison is made, luminance-related false defects are already eliminated, improving reliability without adding time during the critical detection phase

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies luminance correction selectively to specific regions of the reference image that are most prone to false defects, rather than uniformly processing the entire image. This partial action approach maintains high reliability in critical areas while reducing overall processing time

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11587223B2Inspection apparatus that detects defect in image and inspection method and storage medium thereof

Publication Date: 2023.02.21 KK TOSHIBA

AI summary

According to one embodiment, an inspection apparatus includes an image generation device which generates a second image corresponding to a first image and a defect detection device which detects a defect in the second image with respect to the first image. The defect detection device is configured to extract a first partial region in which an amount of change of a luminance of the first image and an amount of change of a luminance of the second image have a correlation, and correct, in the first partial region, the luminance of the first image with respect to the luminance of the second image.