Image Sensor Pixel Structure Sharing Output Circuit
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Solution Overview
Problem
CMOS image sensors face challenges in minimizing pixel size while maintaining performance, leading to increased random telegraph signal noise and image imbalance due to reduced channel length of source follower transistors and inconsistent output circuits.
Innovation Solution
The semiconductor structure of the image sensor increases the channel length of the source follower transistor and configures pixels of the same color to share a reading circuit, reducing noise and inconsistency by rearranging the output circuit to cross pixel boundaries and share resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the size of unit pixels is minimized to increase pixel density, then the number of pixels in limited area increases, but the channel length of source follower transistor is reduced causing increased random telegraph signal noise
Solution Approach 1:
The source follower transistor is configured to extend in the column direction (vertical dimension) rather than being confined within the horizontal pixel boundary. This dimensional transition allows the transistor channel to span across pixel boundaries, effectively increasing the channel length without expanding the pixel area, thereby reducing random telegraph signal noise while maintaining high pixel density
Solution Approach 2:
The source follower transistor serves multiple pixels simultaneously by extending across pixel boundaries. A single transistor channel length extension benefits multiple adjacent pixels, allowing the same structural modification to improve signal quality for multiple pixels without proportionally increasing area consumption
2Quantity of substance
If the size of unit pixels is minimized to increase pixel density, then the number of pixels in limited area increases, but the output circuit performance deteriorates
Solution Approach 1:
The output circuit is reconfigured to extend in the column direction across pixel boundaries rather than being confined within each pixel. This allows the source follower transistor to achieve a longer effective channel length and improved performance while the pixel area remains minimized for high density
3Adaptability or versatility
If pixels are arranged with individual output circuits, then each pixel has independent output capability, but pixel area increases reducing pixel density
Solution Approach 1:
Adjacent pixels share common output circuit components, particularly the source follower transistor, by extending it across pixel boundaries. This merging of output circuits between multiple pixels reduces redundant components, decreases overall pixel area, and increases pixel density while maintaining independent output capability through shared resources
Data Source
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AI summary
The present invention discloses a semiconductor structure of an image sensor, an associated chip and an electronic apparatus. The semiconductor structure includes a semiconductor substrate, and a plurality of pixel groups disposed on the bottom of the semiconductor substrate. Each of the pixel groups includes: a first pixel and a second pixel located in the same row and being adjacent to each other, and a third pixel and a fourth pixel located in another row and being adjacent to each other, wherein the first pixel and the third pixel are disposed diagonally. Each of the pixels includes four sub-pixels, and the four sub-pixels of each pixel share a floating diffusion region and the floating diffusion region is surrounded by photodetectors of the four sub-pixels. An output circuit is shared by the first pixel and the third pixel, and the shared output circuit of the first pixel and the third pixel is located between the first pixel and the third pixel, and extends to the left/right side of the first pixel and the right/left side of the third pixel. The present application is capable of enhancing image quality of the image sensor and improving performance of the output circuit.