Image Sensor Pixel Vertical Electrodes Charge Transfer
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Solution Overview
Problem
Existing image sensor pixel structures with global shutter control face challenges in reducing substrate surface occupation, incomplete charge transfer, and crosstalk due to limitations in diode size and doping levels, leading to image distortion and unwanted afterglow phenomena.
Innovation Solution
The image sensor pixel design incorporates a semiconductor substrate with a photosensitive zone and storage zone of different doping levels, featuring insulated vertical electrodes and charge transfer zones to facilitate efficient charge transfer and reduce crosstalk, while maintaining a compact footprint and minimizing substrate surface occupation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the diode size is reduced to minimize substrate surface occupation, then the pixel structure becomes more compact, but charge transfer becomes incomplete leading to image distortion and afterglow
Solution Approach 1:
The patent applies different doping levels to different regions: the photosensitive zone has a first doping level, the storage zone has a second doping level, and a heavily doped layer with third doping level covers the surface of both zones. This local quality differentiation creates optimal electrical conditions for complete charge transfer even in compact structures, resolving the contradiction between small size and complete charge transfer.
Solution Approach 2:
The patent introduces vertical transfer grids that extend through the substrate depth, creating charge transfer paths in the vertical dimension rather than relying solely on horizontal surface paths. This dimensional transition allows complete charge transfer from reduced-size diodes by utilizing the third dimension (substrate depth) for charge evacuation.
2Productivity
If vertical transfer grids are introduced to improve charge transfer efficiency, then charge transfer efficiency increases, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into the vertical transfer grids: they serve as charge transfer paths, isolation structures between pixels, and potential readout pathways. By combining these functions into a single structural element, the patent achieves high charge transfer efficiency without proportionally increasing device complexity.
Solution Approach 2:
The vertical transfer grids perform multiple roles simultaneously: transferring charges from photosensitive zones to storage zones, isolating adjacent pixels to prevent crosstalk, and providing structured pathways for efficient charge evacuation. This multi-functionality resolves the contradiction by achieving high productivity without linear increases in 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
This design enhances charge transfer efficiency, reduces image distortion, and minimizes crosstalk, allowing for a more compact pixel structure with improved performance in global shutter control modes by utilizing vertical electrodes and optimized doping levels.
Implementation Method 1
a photodiode (PD) in which a photosensitive zone (205) forms a junction with the substrate (201)
Data Source
Figure 1~2
Figure 3A~3C
Figure 3D~3G
AI summary
The sensor has a set of pixels (200) arranged inside and on top of a semiconductor substrate (201), where each pixel has a photosensitive area (205), a read area, and a storage area (207) extending between the photosensitive area and the read area. A first insulated vertical electrode (203) extends in the substrate between the photosensitive area and the storage area. A second insulated vertical electrode (209) extends in the substrate between the storage area and the read area. The photosensitive area is partially delimited by a third insulated vertical electrode (202).