Shared-Pixel Image Sensor Local Wire Level Optimization
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Solution Overview
Problem
Shared-pixel-type image sensors face challenges in maximizing light-receiving efficiency due to reduced exposed areas between metal wires as device size decreases and the number of wires increases, leading to lower fill factor and sensitivity.
Innovation Solution
A shared-pixel-type image sensor design featuring a shared floating diffusion region with local wires connecting contacts at a lower level than the top surfaces, allowing for reduced metal wire lines and increased exposed areas for photoelectric conversion elements, enhancing light-receiving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of metal wires is increased to connect reading elements in a shared-pixel-type image sensor, then the electrical connectivity is improved, but the exposed area between metal wires is reduced, lowering the fill factor
Solution Approach 1:
The patent introduces a vertical dimension by forming contacts at different levels (first contact at a first level, second contact at a second level higher than the first level). This multi-level contact structure allows electrical connection without requiring additional horizontal wire space, thereby preserving the exposed area between metal wires while maintaining electrical connectivity.
2Productivity
If device size is reduced to increase pixel integration, then the number of pixels per unit area is increased, but the exposed area of each photoelectric conversion element is reduced, lowering light-receiving efficiency
Solution Approach 1:
The patent segments the connection structure into multiple independent components: first contact, second contact, and local wire. This segmentation allows each component to be optimized independently - contacts are positioned to minimize interference with photoelectric conversion elements, while the local wire provides necessary electrical connection without occupying excessive horizontal space.
Solution Approach 2:
By utilizing vertical stacking of contacts at different levels, the patent reduces the horizontal footprint required for electrical connections. This enables smaller device dimensions while maintaining adequate exposed areas for photoelectric conversion elements, thus improving pixel integration without sacrificing light-receiving efficiency.
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 design improves light-receiving efficiency and sensitivity by maximizing the area between metal wires, reducing the need for additional wire lines and enhancing the coupling properties of transmission gates to the floating diffusion region.
Implementation Method 1
first and second photoelectric conversion regions which are formed in the semiconductor substrate and are adjacent to each other in a first direction
Data Source
AI summary
A shared-pixel-type image sensor including a shared floating diffusion region formed in a semiconductor substrate; first and second adjacent photoelectric conversion regions sharing the floating diffusion region; two transmission elements that alternately transfer electric charges accumulated in the first and second photoelectric conversion regions to the shared floating diffusion region, respectively; a drive element for outputting the electric charges of the shared floating diffusion region; a first contact formed on the floating diffusion region; a second contact formed on the drive element; and a local wire that connects the first and second contacts to electrically connect the floating diffusion region and the drive element, wherein the local wire is formed at a level lower than respective top surfaces of the first and second contacts.