Wafer Test Key Micro-Lens Samples for Defect Inspection
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Solution Overview
Problem
The tight arrangement of micro-lenses on image sensors makes it difficult to detect defects such as micro-bridges and incorrect curvatures during in-line monitoring, as adjacent lenses interfere with the inspection process, affecting the image capturing ability.
Innovation Solution
A wafer with a test key featuring micro-lens samples arranged differently than the image sensors, allowing for easier in-line monitoring and defect detection, where the micro-lens samples are less densely packed to minimize interference and facilitate observation of defects like over-flow and curvature issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If micro-lenses are tightly arranged on image sensors to increase light gathering efficiency, then the image capturing ability is improved, but defect detection becomes difficult due to interference from adjacent lenses
Solution Approach 1:
The invention divides the monitoring task into two parts: the image sensor array maintains tight packing for optimal performance, while a separate test key with sparsely arranged micro-lens samples provides unobstructed defect detection. This segmentation allows both high-density imaging and clear inspection to coexist on the same wafer.
Solution Approach 2:
The test key contains micro-lens samples that replicate the structure and formation process of the actual image sensor micro-lenses, but in a simplified, sparsely arranged configuration. This copying approach enables defect detection methodology development without requiring inspection of the densely packed sensor array.
2Reliability
If micro-lenses are made as large as possible to increase light gathering efficiency, then the image capturing ability is improved, but micro-bridges may form between adjacent lenses due to over re-flow
Solution Approach 1:
The test key is formed simultaneously with the image sensors during the same micro-lens formation process, allowing preliminary verification of process parameters. By monitoring the sparsely arranged samples first, manufacturers can adjust heating conditions before the entire batch is completed, preventing micro-bridge formation in the densely packed sensor array.
Solution Approach 2:
The sparsely arranged micro-lens samples on the test key provide immediate feedback on the micro-lens formation process quality. This feedback mechanism allows real-time monitoring and adjustment of critical parameters such as heating temperature and duration, ensuring optimal formation conditions for the main image sensor array.
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 effective detection of defects on the test key, which can indicate potential issues on the image sensors, improving yield rates and product quality by simplifying the monitoring process and allowing for timely rectification of processing errors.
Implementation Method 1
After the micro-lens material is heated, each cubical/cylindrical region re-flows to form a convex hemispherical micro-lens
Implementation Method 2
After the micro-lens material is heated, each cubical/cylindrical region re-flows to form a convex hemispherical micro-lens
Data Source
AI summary
A wafer for manufacturing image sensors is disclosed. The wafer includes an image sensor and a test key. The image sensor includes a plurality of micro-lenses; the test key includes a plurality of micro-lens samples for defects inspection. The arrangement of the micro-lens samples on the test key is substantially different from the arrangement of the micro-lenses on the image sensor. The arrangement of the micro-lens samples on the test key allows defects inspection to become less complicated.