Imaging Sensor Floating Diffusion Region Symmetry
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Solution Overview
Problem
Conventional image sensors with floating diffusion regions located in the corner of imaging pixels lead to asymmetries, causing image artifacts and making it difficult to enclose photodiodes with deep trench isolation, thereby reducing pixel versatility.
Innovation Solution
The design of symmetrical imaging pixels with a centrally located floating diffusion region and deep trench isolation, allowing for improved pixel structure and versatility, including shared pixel architectures, and efficient formation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If floating diffusion regions are formed in the corner of imaging pixels, then charge transfer is enabled, but pixel asymmetry occurs causing image artifacts and reduced versatility
Solution Approach 1:
The patent intentionally introduces asymmetry through the interconnect layer configuration rather than floating diffusion placement. The floating diffusion regions are positioned centrally to maintain pixel symmetry, while the interconnect layer (formed on a separate substrate) provides the necessary electrical connection asymmetry for charge transfer functionality.
Solution Approach 2:
The patent moves the floating diffusion regions from the traditional corner position in the planar dimension to a central position, and resolves the charge transfer connection issue by adding a vertical dimension through substrate stacking. The interconnect layer on a second substrate provides electrical coupling without compromising the symmetrical in-pixel layout.
2Ease of operation
If floating diffusion regions are formed in the corner of imaging pixels, then charge transfer is enabled, but image artifacts occur due to asymmetry
Solution Approach 1:
The patent intentionally introduces asymmetry through the interconnect layer configuration rather than floating diffusion placement. The floating diffusion regions are positioned centrally to maintain pixel symmetry, while the interconnect layer (formed on a separate substrate) provides the necessary electrical connection asymmetry for charge transfer functionality.
Solution Approach 2:
The patent moves the floating diffusion regions from the traditional corner position in the planar dimension to a central position, and resolves the charge transfer connection issue by adding a vertical dimension through substrate stacking. The interconnect layer on a second substrate provides electrical coupling without compromising the symmetrical in-pixel layout.
3Ease of manufacture
If conventional floating diffusion regions are used, then charge readout is achieved, but deep trench isolation integration becomes difficult
Solution Approach 1:
The patent moves the floating diffusion regions from the traditional corner position in the planar dimension to a central position, and resolves the charge transfer connection issue by adding a vertical dimension through substrate stacking. The interconnect layer on a second substrate provides electrical coupling without compromising the symmetrical in-pixel layout.
4Adaptability or versatility
If symmetrical pixel design with central floating diffusion is used, then pixel versatility and image quality improve, but electrical coupling to readout circuitry becomes more complex
Solution Approach 1:
The patent divides the imaging device into two separate substrates: the first substrate contains the photodetectors and centrally-positioned floating diffusion regions for symmetrical pixel design, while the second substrate contains the interconnect layer and readout circuitry. This segmentation allows each substrate to be optimized independently while maintaining electrical coupling through vertical stacking.
Solution Approach 2:
The patent moves the floating diffusion regions from the traditional corner position in the planar dimension to a central position, and resolves the charge transfer connection issue by adding a vertical dimension through substrate stacking. The interconnect layer on a second substrate provides electrical coupling without compromising the symmetrical in-pixel layout.
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
This design enhances image sensor performance by reducing artifacts, facilitating easier integration of photodiodes, and enabling versatile shared architectures, thereby improving image quality and manufacturing efficiency.
Implementation Method 1
Each pixel includes a photosensitive layer that receives incident photons (light) and converts the photons into electrical charge
Data Source
AI summary
An image sensor may include a symmetrical imaging pixel with a floating diffusion region. The floating diffusion region may be formed in the center of the imaging pixel. A shallow p-well may be formed around the floating diffusion region. A transfer gate configured to transfer charge from a photodiode to the floating diffusion region may be ring-shaped with an opening that overlaps the floating diffusion region. Isolation regions including deep trench isolation and a p-well may surround the photodiode of the imaging pixel. A p-stripe may couple the shallow p-well around the floating diffusion region to the isolation regions. The floating diffusion regions of neighboring pixels may be coupled together with additional conductive layers to implement shared configurations.