Image Sensor Embossing Structures Prevent Crack Propagation
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Solution Overview
Problem
MOS image sensors are prone to cracking in the protective layer due to thermal and mechanical stress during packaging, which can adversely affect the optical characteristics by allowing cracks to propagate from the peripheral circuit region to the pixel array region.
Innovation Solution
The implementation of embossing structures in the peripheral circuit region, separated from each other and formed with the same material as the lenses, increases the surface area for contact with the protective layer, enhancing its surface energy and preventing crack propagation into the pixel array region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a protective layer is formed over the lenses and peripheral circuit region, then the structural integrity is improved, but cracking occurs due to thermal and mechanical stress during packaging
Solution Approach 1:
The peripheral circuit region is divided into multiple embossing structures that are separated from each other, creating segmented stress distribution zones that prevent crack propagation across the entire region
Solution Approach 2:
Embossing structures with increased surface area are locally formed in the peripheral circuit region to enhance surface energy specifically where stress concentration occurs, without affecting the optical properties of the lens region
2Reliability
If embossing structures are formed in the peripheral circuit region, then crack propagation is prevented, but device complexity increases
Solution Approach 1:
The embossing structures are formed with the same material composition as the existing lenses, maintaining material homogeneity across the device while providing different functional roles (stress management vs. light focusing)
Solution Approach 2:
The embossing structures serve multiple functions: they increase surface energy to prevent cracking, maintain planarity for protective layer formation, and are formed using the same material process as the lenses, thereby reducing overall manufacturing 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
The increased surface energy of the protective layer effectively prevents cracks from spreading into the pixel array region, maintaining the optical integrity of the MOS image sensor.
Implementation Method 1
increases the surface area for contact with the protective layer, enhancing its surface energy and preventing crack propagation into the pixel array region
Data Source
AI summary
An image sensor includes a first region of a substrate having photoelectric conversion elements formed therein, and includes a second region of the substrate outside of the first region. The image sensor includes a plurality of lenses, a plurality of embossing structures, and a protective layer. The lenses are formed over the first region. The embossing structures are formed over the second region, and the embossing structures are separated from each-other. The protective layer is formed over the lenses and the embossing structures that prevent crack propagation.