CMOS Image Sensor Air Grid Structure for Optical Isolation
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Solution Overview
Problem
Current image sensor designs and fabrication methods result in poor light blocking or isolation between adjacent photodiodes, leading to poor performance and pixel failure in complementary metal oxide semiconductor (CMOS) image sensors.
Innovation Solution
The implementation of an air grid structure with reinforcing pillars at cross-points between pixels, enhancing optical isolation and mechanical strength by forming voids and pillars in the dielectric layer between adjacent color filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current image sensor designs and fabrication methods are used, then manufacturing simplicity is maintained, but optical isolation between adjacent photodiodes deteriorates
Solution Approach 1:
The patent divides the dielectric layer into multiple functional regions: air grid trenches for optical isolation, pillars for mechanical support, and voids for enhanced isolation. This segmentation allows each component to perform its specific function optimally, resolving the contradiction between optical isolation and structural complexity by creating a modular architecture where complexity is organized into discrete, functional units.
Solution Approach 2:
The patent implements a nested structure where pillars are positioned within the dielectric layer at the intersections of air grid trenches, and voids are formed around these pillars. This nesting approach allows multiple isolation mechanisms (pillars, trenches, voids) to work together in a compact arrangement, improving optical isolation without proportionally increasing overall device complexity.
2Reliability
If air grid structure with pillars is implemented, then optical isolation is improved, but fabrication complexity increases
Solution Approach 1:
The patent forms pillars before creating the air grid trenches and voids. This preliminary action establishes a stable structural framework that guides subsequent fabrication steps. By pre-positioning the pillars, the patent simplifies the overall fabrication process despite the increased structural complexity, as the pillars serve as reference points for trench formation and void creation.
Solution Approach 2:
The patent applies different materials and structures at different locations: pillars at intersections for mechanical support, air grid trenches between pixels for optical isolation, and voids around pillars for enhanced isolation. This local differentiation allows each region to be optimized for its specific function, improving overall optical isolation while managing fabrication complexity through localized rather than universal structuring.
3Strength
If pillars are added at intersection points, then mechanical strength is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into the pillar structure: mechanical support at intersections, optical isolation through associated voids, and structural framework for the air grid trenches. By combining these functions into a single integrated element, the patent improves mechanical strength without proportionally increasing device complexity, as the pillars serve multiple purposes simultaneously.
Solution Approach 2:
The pillars serve multiple functions: providing mechanical support at vulnerable intersection points, acting as structural anchors for the air grid trenches, and serving as centers for void formation that enhance optical isolation. This multi-functionality allows the patent to improve mechanical strength while minimizing the increase in device complexity, as the same structural element addresses multiple requirements.
Data Source
AI summary
Embodiments of image sensors and methods of fabrication are provided herein. In some embodiments, a device includes: a substrate having a dielectric layer disposed atop the substrate; a pillar disposed within the dielectric layer; and a plurality of voids arranged in an array within the dielectric layer, wherein the pillar is disposed between adjacent voids of the plurality of voids. A two-dimensional array of color filters can be disposed atop the substrate having respective voids of the plurality of voids disposed between adjacent color filters and having the pillar disposed between adjacent voids and between diagonally disposed color filters of the array of color filters. A plurality of photoelectric elements can be disposed in the substrate and correspond to and be disposed beneath individual color filters of the array of color filters.