Semiconductor Appearance Inspection Using Guard Ring Reference
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Solution Overview
Problem
The existing automatic inspection methods for semiconductor devices, particularly WLP Flip Chips, face challenges in accurately judging defects due to the instability of the first resin layer's edge, leading to incorrect classification of non-defective products as defective, caused by mask misalignment and the fragility of passivation films during the dicing process.
Innovation Solution
The method involves using a guard ring surrounding the element forming region, with a passivation film and resin layer extending over it, and measuring distances between the guard ring and chipping to accurately determine if the chipping extends beyond the resin layer's edge, thereby stabilizing the judgment reference and reducing misclassification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the end portion of the first resin layer is used as a reference for automatic appearance inspection, then the inspection can be performed, but the recognition accuracy varies largely due to mask misalignment causing unstable reference position
Solution Approach 1:
The patent introduces a guard ring as an intermediary reference object that is not affected by mask misalignment. The guard ring serves as a stable mediator between the inspection system and the resin layer, providing a reliable reference position for measuring chipping distances without being influenced by the instability of the resin layer's end portion.
Solution Approach 2:
The patent changes the reference parameter from the resin layer's end portion position (which varies due to mask misalignment) to the guard ring's position (which remains stable). By measuring distances from the guard ring instead of the resin layer edge, the inspection system achieves consistent and accurate defect classification despite variations in resin layer positioning.
2Reliability
If a judgment line is set away from the resin layer end portion to avoid misclassification, then non-defective products are not discarded, but the inspection accuracy decreases and yield is reduced
Solution Approach 1:
The patent replaces the mechanical/physical reference system (resin layer edge position) with an optical/stable reference system (guard ring position). This substitution allows for precise measurement and accurate judgment lines to be established, enabling both high reliability in defect classification and high productivity by correctly identifying non-defective products.
3Strength
If the passivation film is made hard and fragile to protect the device, then device protection is improved, but crack propagation occurs easily during dicing process
Solution Approach 1:
The patent segments the passivation film structure by creating a passivation film removed groove that separates the scribe region from the element forming region. This segmentation prevents cracks from propagating from the scribe region into the element forming region, allowing the passivation film to maintain its hardness and protective function while reducing crack propagation risk during dicing.
Data Source
AI summary
The invention provides a semiconductor device and a method of automatically inspecting the appearance, which achieves proper recognition of the size of a chipping occurring from an end portion of the semiconductor device toward the element forming region by an automatic appearance inspection machine, and prevents a problem of judging an appearance non-defective product as an appearance defective product. A semiconductor device includes a resin layer extending from an element forming region over a guard ring surrounding the element forming region so as to cover these except a plurality of portions of the guard ring, and a chipping extending from a chip end portion of a semiconductor device toward the end portion of the resin layer. An end portion of the guard ring partially exposed from the resin layer is used as a reference to measure a distance y from the end portion of the guard ring to the end portion of the chipping and a distance x from the end portion of the guard ring to the end portion of the resin layer. The device is judged as an appearance non-defective product when y is larger than x or is judged as an appearance defective product when y is equal to x or y is smaller than x.