Semiconductor Mask Inspection False Defect Removal
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Solution Overview
Problem
Current mask inspection systems for semiconductor manufacturing face challenges in accurately distinguishing between true defects and false defects, such as white spots caused by cosmic rays, which can lead to increased review time and reduced productivity due to the difficulty in shielding cosmic rays and the limitations of existing comparison methods.
Innovation Solution
An inspection apparatus and method that utilize a line sensor to acquire optical images, compare them with reference images, and employ a false defect determining unit to calculate differences in gradation values between center pixels and adjacent pixels, identifying and removing false defects by averaging adjacent pixel values or re-acquiring images to minimize false defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cosmic rays are shielded using a screen, then false defects from cosmic rays can be reduced, but the inspection system complexity and cost increase significantly
Solution Approach 1:
The patent extracts and removes false defect data from the inspection results through software processing. The false defect determining unit identifies and eliminates white spots caused by cosmic rays from the optical image data, separating the harmful false defects from the useful inspection data without adding physical shielding components.
Solution Approach 2:
The patent creates a reference image from design data and compares it with the actual optical image. By copying the expected pattern from CAD data and comparing it with the measured image, the system can identify deviations that are true defects versus those that are false defects matching the reference.
2Reliability
If multiple inspection processes are performed to remove white spots, then false defect detection is reduced, but inspection time and productivity decrease
Solution Approach 1:
The patent performs preliminary processing of the optical image data by storing data from three lines and calculating differences between center pixels and adjacent pixels before final defect determination. This preliminary analysis identifies potential false defects early in the process, allowing their removal before the inspection is completed, thus eliminating the need for multiple inspection passes.
Solution Approach 2:
The patent implements a feedback mechanism where the false defect determining unit continuously monitors the optical image data, identifies white spots based on gradient analysis, and removes them from the inspection results. This real-time feedback loop eliminates false defects during a single inspection process rather than requiring multiple passes.
3Measurement precision
If operators manually review all detected defects, then true defects can be confirmed, but review time increases due to false defects like white spots
Solution Approach 1:
The patent extracts false defect information from the inspection results through automated analysis. By calculating gradient values and comparing center pixels with adjacent pixels, the system identifies and removes white spots caused by cosmic rays, leaving only true defects for operator review. This extraction process significantly reduces the number of defects operators need to manually verify.
Solution Approach 2:
The patent enables the inspection system to automatically identify and eliminate false defects without operator intervention. The false defect determining unit performs self-service by autonomously analyzing the optical image data, detecting white spots through gradient calculation, and removing them from the results, freeing operators to focus only on true defect verification.
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 approach enhances inspection accuracy by effectively reducing false defect detection, thereby improving productivity and reducing the burden on operators by minimizing the need for multiple inspection processes.
Implementation Method 1
Light transmitted through or reflected from the mask is focused on an image sensor forming an image thereon
Data Source
AI summary
An inspection apparatus and method comprising a unit for acquiring an optical image of an object to be inspected by irradiating the object with light, wherein the unit includes a line sensor comprising a plurality of sensors linearly arranged in a row, a generating unit for generating a reference image from design data of the object to be inspected, a comparing unit for comparing the optical image with the reference image, a unit for storing data of three lines acquired by the line sensor, and calculating differences between a gradation value of a pixel on a center line and each gradation value of the eight pixels adjacent to the pixel determining if the pixel is a defect if all of the eight differences of the adjacent pixels are more than a predetermined threshold.