Image Sensor Chip Scale Package Fusion Bonding
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Solution Overview
Problem
Conventional image sensor semiconductor packages face challenges in achieving a compact chip scale package size due to the need for adhesive bonding, which results in larger package dimensions and increased distance between the active pixel array and the die edge, requiring a keep out zone to account for adhesive bleed.
Innovation Solution
The method involves forming image sensor chip scale packages by creating cavities in semiconductor wafers, filling them with materials, and bonding a transparent cover using fusion bonds with passivation oxide or anti-reflective coating, eliminating the need for adhesives and allowing for a more compact design by ensuring the cover is bonded directly to the wafer stack without adhesive bleed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If adhesive bonding is used to bond the transparent cover, then the bonding process is simpler, but the package size increases and a keep out zone is required
Solution Approach 1:
The patent removes the adhesive layer from the bonding structure, extracting the source of the keep out zone problem. By eliminating the adhesive and its required bleed margin, the package size is reduced while maintaining bonding functionality through direct fusion bonding between the transparent cover and the passivation oxide or anti-reflective coating.
Solution Approach 2:
The patent introduces fusion bonding as an intermediary mechanism that eliminates the need for adhesive materials. The direct bonding between the transparent cover and the wafer stack surfaces (passivation oxide or anti-reflective coating) serves as a mediator that achieves bonding without requiring a separate adhesive layer or keep out zone.
2Reliability
If adhesive is used for bonding, then the transparent cover can be bonded to the wafer stack, but the distance between the active pixel array and die edge increases
Solution Approach 1:
The adhesive layer is extracted from the bonding structure, removing the source of the increased distance problem. The direct fusion bonding eliminates the adhesive thickness and associated keep out zone, thereby reducing the distance from the active pixel array to the die edge while maintaining bonding reliability.
Solution Approach 2:
The bonding method is changed from adhesive-based to fusion bonding, fundamentally altering the bonding parameters. This parameter change eliminates the adhesive layer thickness and associated keep out zone requirements, reducing the overall distance from the active pixel array to the die edge while maintaining reliable bonding.
3Reliability
If adhesive bonding is used, then the transparent cover can be secured, but the package dimensions increase
Solution Approach 1:
The adhesive layer is removed from the package structure, extracting the source of the increased package dimensions. The direct fusion bonding between the transparent cover and the wafer stack eliminates the adhesive thickness and keep out zone, thereby reducing the overall package dimensions while maintaining secure cover attachment.
Solution Approach 2:
Fusion bonding serves as an intermediary mechanism that directly bonds the transparent cover to the wafer stack without requiring adhesive materials. This intermediary bonding method achieves secure cover attachment while eliminating the dimensional penalties associated with adhesive layers and keep out zones.
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 approach enables the formation of image sensor CSPs with reduced package size, eliminating the need for a keep out zone and allowing the active pixel array to be closer to the die edge, thus achieving a more compact and efficient chip scale package.
Implementation Method 1
bonding a transparent cover over the fill material and over the one or more layers using either: a fusion bond between the transparent cover and a passivation oxide, or; a fusion bond between the transparent cover and an anti-reflective coating
Data Source
AI summary
Methods of forming an image sensor chip scale package. Implementations may include providing a semiconductor wafer having a pixel array, forming a first cavity through the wafer and/or one or more layers coupled over the wafer, filling the first cavity with a fill material, planarizing the fill material and/or the one or more layers to form a first surface of the fill material coplanar with a first surface of the one or more layers, and bonding a transparent cover over the fill material and the one or more layers. The bond may be a fusion bond between the transparent cover and a passivation oxide; a fusion bond between the transparent cover and an anti-reflective coating; a bond between the transparent cover and an organic adhesive coupled over the fill material, and/or; a bond between a first metallized surface of the transparent cover and a metallized layer coupled over the wafer.