CMOS Image Sensor Protection Film for Sidewall Moisture Blocking
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Solution Overview
Problem
Solid-state imaging devices, such as CMOS image sensors, face issues with moisture and impurity ingress, particularly at side surfaces without a protection film, leading to degradation in quality, decolorization of color filters, and increased dark current due to high water vapor pressure environments.
Innovation Solution
A transparent protection film with a side wall and ceiling part is implemented, covering the region surrounding photodiodes on the substrate, extending along side surfaces and embedded in grooves, and contacting the substrate to prevent moisture and impurity ingress, while also serving as a microlens for light gathering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection film is formed only over the surface of the microlens, then the microlens is protected from moisture and impurity, but the side surface of the chip remains vulnerable to moisture ingress
Solution Approach 1:
The protection film is extended from the traditional two-dimensional planar configuration over the microlens surface to a three-dimensional structure that includes vertical side wall portions extending along the side surfaces of the chip. This dimensional extension ensures that moisture and impurities are blocked not only from the top surface but also from the side surfaces, completely preventing moisture ingress pathways.
Solution Approach 2:
The protection film is divided into distinct functional portions: a planar ceiling portion covering the microlens surface and vertical side wall portions extending along the side surfaces. This segmentation allows each portion to address specific protection needs - the ceiling protects the optical surface while the side walls protect the lateral surfaces, collectively providing comprehensive protection.
2Reliability
If the protection film is extended to cover side surfaces, then waterproofing is improved, but the device structure becomes more complex
Solution Approach 1:
The protection film serves multiple functions simultaneously: it acts as a moisture barrier, an optical element (microlens), and a structural protective layer. By forming the side wall portions of the protection film to function as both protective barriers and optical components, the design achieves comprehensive waterproofing without adding separate structural elements, thereby maintaining manufacturing simplicity.
Solution Approach 2:
The protective function and optical function are merged into a single integrated protection film structure. The side wall portions that provide waterproofing also serve as optical elements for light guidance, eliminating the need for separate protective housings or additional optical components, thus reducing overall device 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 solution effectively enhances the waterproofing of solid-state imaging devices, preventing moisture and impurity entry, maintaining optical characteristics, and reducing dark current, even in high humidity environments.
Implementation Method 1
a protection film that is transparent, has a water-proofing property, and includes a side wall part vertical to the surface of the substrate and a ceiling part covering a region surrounded by the side wall part
Implementation Method 2
the ceiling part and the side wall part surrounding a region where a plurality of photodiodes are arranged over the substrate
Data Source
AI summary
There is provided a solid-state imaging device including a substrate having a surface over which a plurality of photodiodes are formed, and a protection film that is transparent, has a water-proofing property, and includes a side wall part vertical to the surface of the substrate and a ceiling part covering a region surrounded by the side wall part, the side wall part and the ceiling part surrounding a region where the plurality of photodiodes are arranged over the substrate.