Noisy Patterned Feature Inspection for RDL Line Defects
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Solution Overview
Problem
Traditional inspection methods for detecting defects in redistribution layers (RDL) on backend packaging wafers are hindered by inconsistent sub-die shifts and metal surface roughness, which cause noise and obscure line opening defects, making intensity-difference based approaches ineffective.
Innovation Solution
A system and method for single die inspection (SDI) using macro inspection tools with oblique illumination and multiple detection channels to detect defects in RDL lines, excluding die-to-die noise and focusing on test image analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional die-to-die difference inspection is used, then common die defects can be detected, but inconsistent sub-die shifts cause substantial noise that obscures line opening defects
Solution Approach 1:
The patent extracts and removes the harmful noise component from the inspection process by using a reference image of the same die before RDL formation, eliminating the influence of sub-die shifts and roughness that are inherent in die-to-die comparison methods
Solution Approach 2:
The patent performs preliminary action by capturing a reference image of the die at an earlier stage (before RDL formation) when the substrate surface is still flat and free from RDL-related noise, so that this clean reference can be used for subsequent defect detection
2Ease of operation
If intensity-difference based inspection is used, then defect detection is simplified, but metal surface roughness and inconsistent shifts create noise that makes defects undetectable
Solution Approach 1:
The patent extracts the harmful noise (roughness and shift variations) by using a reference image captured at an earlier process stage, allowing simple intensity-difference comparison to remain effective while eliminating the noise that would otherwise obscure defects
3Productivity
If die-to-die inspection is used, then manufacturing throughput is maintained, but noise from sub-die inconsistencies requires complex noise filtering
Solution Approach 1:
The patent extracts and removes the noise source by comparing against a reference image from the same die before RDL formation, eliminating the need for complex noise filtering algorithms while maintaining high manufacturing throughput
Solution Approach 2:
The patent performs preliminary action by capturing a clean reference image at an earlier process stage, which serves as a noise-free baseline for defect detection, thereby simplifying subsequent processing while maintaining productivity
Data Source
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AI summary
Methods and systems for detecting defects on a specimen are provided. One system includes an inspection subsystem configured to generate images of a specimen and one or more computer subsystems configured for detecting defect candidates on the specimen. Detecting the defect candidates includes identifying a patterned feature in a test image included in the images generated of the specimen. Detecting the defect candidates also includes, for at least one pixel in the test image located within the patterned feature, determining a difference between a characteristic of the at least one pixel and the characteristic of other pixels in the test image located within a predetermined window of the at least one pixel. In addition, detecting the defect candidates includes detecting a defect candidate at the at least one pixel based on the determined difference.