Wafer Bonding Layer Edge Rebuild for Uniform Bonding Surfaces
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Solution Overview
Problem
Nonuniformities in the surfaces of semiconductor wafers, such as edge roll-off, result in partial bonding and potential gaps at the edges, leading to weak points in the bonding interface, which can cause humidity ingress and delamination.
Innovation Solution
A thick bonding layer is formed with a top surface higher than the bottom surface in the edge region, and a photoresist material is used to etch the bonding layer, ensuring a flat and uniform surface across the edge and non-edge regions, minimizing the likelihood of gaps and enhancing bonding integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bonding methods are used on wafers with edge roll-off, then bonding can be achieved in the center regions, but gaps and weak points form at the edges leading to humidity ingress and delamination
Solution Approach 1:
The edge region is rebuilt with an elevated structure before the bonding process. This preliminary action compensates for the edge roll-off nonuniformity, ensuring that the bonding surfaces are substantially coplanar when the wafers are bonded together, preventing gaps and improving bonding integrity
Solution Approach 2:
The rebuilding process applies material selectively to the edge region of the wafer, creating a localized elevation that compensates for the edge roll-off. This local modification ensures uniform bonding surfaces without affecting the center regions, resolving the surface uniformity issue while maintaining bonding integrity
2Reliability
If complex edge rebuilding processes are used to fix edge roll-off, then bonding integrity is improved, but processing time and complexity increase
Solution Approach 1:
The edge rebuilding process is merged with the existing wafer fabrication process flow. The rebuild layer is formed using standard deposition and etching equipment already present in the manufacturing line, combining multiple functions into a integrated process that improves bonding integrity without requiring separate complex processing steps
Solution Approach 2:
The methodology controls the rebuild layer thickness and etch depth parameters to achieve the desired edge elevation. By optimizing these parameters, the process achieves effective edge rebuilding in a controlled manner, improving bonding integrity while maintaining processing efficiency through precise parameter management
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
This method provides faster and cost-effective edge rebuilding by reducing processing operations and utilizing low-complexity techniques, resulting in improved bonding integrity and reduced contamination.
Implementation Method 1
a photoresist material is used to etch the bonding layer
Data Source
AI summary
A thick bonding layer is formed over the surface of a semiconductor wafer such that a top surface of the bonding layer in an edge region is at a greater vertical height than a bottom surface of the bonding layer in a non-edge region of the semiconductor wafer. A photoresist material is then deposited across the surface of the semiconductor wafer and patterned such that the photoresist material remains only on the edge region of the semiconductor wafer. The bonding layer in the non-edge region is etched based on the photoresist material such that the top surface of the bonding layer is substantially flat and uniform across the edge region and the non-edge region of the semiconductor wafer.