Image Sensor Light Guide Insulator for Crack Prevention
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Solution Overview
Problem
High-resolution image sensors face reliability issues due to faults such as cracks in the optical guide parts on conductive pads during manufacturing, affecting their sensitivity and performance.
Innovation Solution
An image sensor design featuring an interconnection structure with cavities filled with a light guide material having a refractive index greater than the inter-metal insulating layers, and a moisture-blocking layer to enhance light sensitivity and reduce defects like cracks, using materials like fluor series polymers, poly-siloxane resins, or polymethyl methacrylate (PMMA) series polymers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high refractive light guide part is spread on a photoelectric device to improve sensitivity, then sensitivity is improved, but cracks or faults occur on the optical guide part during manufacturing, reducing reliability
Solution Approach 1:
The patent introduces an electrically insulating layer made of light guide material as an intermediary between the conductive pad and the optical guide part. This mediator prevents direct contact between the optical guide part and the conductive pad, eliminating the mechanical stress that causes cracks while still allowing light transmission to maintain sensitivity.
Solution Approach 2:
The patent uses a composite structure combining electrically insulating material (light guide material) with the optical guide part. This composite approach allows the system to simultaneously achieve electrical insulation (preventing cracks) and optical guidance (maintaining sensitivity), resolving the contradiction between reliability and sensitivity.
2Illumination intensity
If the optical guide part is spread on the conductive pad to improve light transmission, then light sensitivity is improved, but the structural integrity deteriorates due to cracks forming during manufacturing
Solution Approach 1:
The electrically insulating layer serves as a mediator that supports the optical guide part without allowing direct adhesion to the conductive pad. This prevents stress concentration and crack formation during manufacturing while maintaining the light transmission pathway for improved sensitivity.
Solution Approach 2:
The patent applies different material properties at different locations: the electrically insulating layer provides mechanical support and electrical insulation at the pad interface, while the optical guide part provides light transmission in the optical path. This localized differentiation maintains structural integrity where needed while preserving light sensitivity where required.
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 improves the reliability and sensitivity of image sensors by stabilizing light transmission and reducing defects, ensuring consistent performance and increased light sensitivity for high-resolution imaging applications.
Implementation Method 1
cavities are filled with a light guide material, which has an index of refraction that is greater than an index of refraction of the inter-metal insulating layers
Implementation Method 2
The index of refraction of the light guide material may be greater than or equal to 1.65
Data Source
AI summary
An image sensor includes an array of image sensor cells, on a substrate, and a peripheral circuit region extending adjacent the array of image sensor cells. The array of image sensor cells includes a plurality of lens elements and a plurality of color filters extending adjacent the plurality of lens elements. A plurality of photodiodes is provided in the substrate. The plurality of photodiodes are aligned to corresponding ones of the plurality of lens elements. An interconnection structure is also provided, which extends between the plurality of photodiodes and the plurality of color filters. The interconnection structure has an array of cavities therein that are aligned to corresponding ones of the plurality of photodiodes and are filled with a light guide material. The peripheral circuit region includes a metal interconnect pattern and an electrically conductive pad on the metal interconnect pattern. An electrically insulating layer extends on the electrically conductive pad. The electrically insulating layer is formed of the light guide material.