Wafer Edge Pre-Wetting Ring for Stable Ultrasonic Coupling
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Solution Overview
Problem
In ultrasonic scanning of bonded wafers, the edges often fail to absorb couplant fluid uniformly, leading to artifacts and poor inspection results due to sponge-like materials reflecting ultrasound and hiding air defects, which increases scan time and may contaminate internal wafer layers.
Innovation Solution
A pre-wet ring system with multiple nozzles is used to rapidly wet the edges of the wafer before scanning, creating a film of water that maintains ultrasound coupling throughout the inspection, reducing the need for additional water sources and minimizing scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional ultrasonic scanning is performed without pre-wetting the wafer edges, then the scanning process can proceed directly, but the edges fail to absorb couplant uniformly causing artifacts and poor inspection results
Solution Approach 1:
The patent applies preliminary action by pre-wetting the wafer edges with couplant before the ultrasonic scanning process begins. This is achieved through a pre-wet ring that delivers couplant to the wafer edges, ensuring uniform absorption and eliminating artifacts that would otherwise degrade inspection accuracy. The pre-wetting step prepares the surface in advance, allowing the main scanning to proceed efficiently without rework.
2Reliability
If additional water sources are used during scanning to maintain coupling, then ultrasound coupling is maintained, but scan time increases and contamination risk increases
Solution Approach 1:
The pre-wet ring delivers couplant to the wafer edges before scanning begins, creating a reservoir that maintains ultrasound coupling throughout the scan without requiring additional water sources. This preliminary wetting ensures reliable coupling while preventing the need for continuous fluid addition, thereby maintaining scan efficiency and reducing contamination risks from multiple water sources.
Solution Approach 2:
The system allows the pre-wetted wafer edges to self-maintain ultrasound coupling throughout the scanning process. The couplant absorbed into the sponge-like edge materials continues to provide coupling medium as the transducer scans across the wafer surface, eliminating the need for external water sources during scanning and preventing contamination from additional fluid sources.
3Measurement precision
If sponge-like materials at wafer edges are not pre-wetted, then the scanning can start immediately, but they reflect ultrasound and hide air defects
Solution Approach 1:
The pre-wet ring applies couplant to the sponge-like edge materials before scanning begins, transforming their acoustic properties. This preliminary wetting eliminates the ultrasound reflection problem caused by dry sponge materials, allowing defects to be detected accurately without increasing manufacturing complexity. The system integrates this pre-wetting function into a simple ring structure that delivers couplant uniformly to the edges.
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
The pre-wet ring system ensures uniform wetting of the wafer edges and surfaces, enhancing inspection accuracy by reducing artifacts and maintaining ultrasound coupling, thereby improving scan efficiency and preventing contamination.
Implementation Method 1
A pre-wet ring system with multiple nozzles is used to rapidly wet the edges of the wafer before scanning, creating a film of water that maintains ultrasound coupling throughout the inspection
Implementation Method 2
A scanning process using an ultrasonic transducer benefits from using a fluid, or couplant to provide an imaging medium for the scanning process
Implementation Method 3
edges of a wafer may not absorb, or be exposed to the fluid, or couplant, which causes artifacts and poor scanning
Data Source
AI summary
Systems, methods and apparatus related to pre-wetting an edge portion of a bonded wafer prior to wetting a flat, horizontal portion of the bonded wafer. The apparatus includes a frame having nozzles directed such that couplant discharged from these nozzles wet the edge of the wafer. The edge nozzles have couplant flow vectors that interface to dampen the trajectory of fluid to reduce splash and pre-wet the edges of the bonded wafer.