Wafer Bump Optical Inspection for Immediate Height Defect Detection
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Solution Overview
Problem
Existing methods for detecting abnormal bump heights in through-package-vias (TPVs) of 3D integrated circuits are inefficient, leading to significant yield loss and increased glass recycle rates due to delayed detection, often occurring several hours after plating, with low sampling rates and high rates of undetected defects.
Innovation Solution
Implementing an in-situ automated optical inspection system within a plating tool to detect abnormal bump heights immediately after plating, positioned on the wafer transfer path between processing and load chambers, using a photoelectric sensor, light source, and image analysis device to analyze wafer images for defects before photoresist stripping and UBM etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional inspection methods are used with delayed detection several hours after plating, then device complexity is reduced, but manufacturing precision and productivity deteriorate due to low sampling rates and high defect escape rates
Solution Approach 1:
The patent replaces traditional mechanical contact-based height measurement methods with optical inspection technology. The optical system uses light sources and sensors to non-contactly detect bump heights, eliminating the need for physical probes and reducing system complexity while improving measurement precision and enabling 100% sampling inspection.
Solution Approach 2:
The patent creates optical copies (images) of the wafer surface and bump structures to analyze bump heights. By capturing optical images and processing them through image analysis algorithms, the system can measure bump heights with high precision without physically touching the samples, thereby improving manufacturing precision while keeping the inspection system relatively simple.
2Productivity
If 100% sampling inspection is implemented immediately after plating, then manufacturing precision and productivity improve, but device complexity and inspection time increase
Solution Approach 1:
The patent performs inspection immediately after plating while the bumps are still accessible and before subsequent processing steps (photoresist stripping, UBM etching) that would make inspection more difficult or time-consuming. This preliminary inspection approach enables 100% sampling without significant time penalty, as it leverages the existing process sequence rather than adding separate inspection stages.
Solution Approach 2:
By using optical inspection instead of mechanical measurement methods, the system achieves rapid non-contact measurement that can handle 100% sampling rates. The optical method eliminates time-consuming mechanical probe positioning and contact measurement, thereby improving productivity while maintaining acceptable inspection times.
3Productivity
If optical inspection is performed on the wafer transfer path between processing and load chambers, then productivity improves through immediate detection, but device complexity increases due to integration requirements
Solution Approach 1:
The patent merges the optical inspection system with the existing plating tool structure by integrating the inspection station into the wafer transfer path between processing and load chambers. This consolidation allows immediate inspection of plated wafers without requiring separate handling or transport to external inspection equipment, improving productivity while the shared infrastructure reduces overall system complexity.
Solution Approach 2:
The plating tool is designed to serve multiple functions: plating processing, immediate optical inspection, and wafer handling. By making the plating tool universal and capable of performing both processing and inspection functions, the system improves productivity through immediate defect detection while avoiding the need for separate dedicated inspection equipment, thereby reducing integration complexity.
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
Enhances detection of abnormal bump heights to 100% sampling rate, reducing the impact of defective wafers from 16 to 4, improving glass recycle rate from 1.66% to 0.4%, and increasing yield from 50 parts per million to 10 parts per million by preventing undetected defects.
Implementation Method 1
a light source to emit light to illuminate a wafer on a transfer path of a plating tool
Implementation Method 2
a photoelectric sensor to detect the wafer on the transfer path
Data Source
AI summary
An image analysis device may align an image to determine a position of a wafer within the image. The wafer may include a plurality of wafer bumps. The image analysis device may mask, based on the position of the wafer, the image to obtain an image of a portion of the wafer. The image analysis device may binarize the image of the portion of the wafer to create a binarized image of the portion of the wafer. The image analysis device may determine a bump pattern, associated with the plurality of wafer bumps, based on the binarized image of the portion of the wafer. The image analysis device may perform a defect analysis of the determined bump pattern. The defect analysis may be associated with detecting regions of the portion of the wafer in which one or more wafer bumps have abnormal bump heights.