Dual Transfer Gate Pixel Layout for Backflow and Noise Control
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Solution Overview
Problem
Current image sensors face challenges in reducing defects and enhancing the function of transfer gates, particularly in preventing backflow phenomena and point fixed pattern noise.
Innovation Solution
The implementation of a semiconductor device with dual transfer gates, where the first and second transfer gates are disposed asymmetrically with respect to the photoelectric converter and floating diffusion region, and an off-voltage is sequentially applied to prevent backflow and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single transfer gate is used to transfer charges from the photoelectric converter to the floating diffusion region, then the device structure is simple, but backflow phenomena occur where electrons return to the photoelectric converter causing image defects
Solution Approach 1:
The single transfer gate is divided into two separate transfer gates (first transfer gate and second transfer gate) positioned at different locations. This segmentation allows independent control of charge transfer from different regions of the photoelectric converter, effectively preventing electron backflow to the photoelectric converter while maintaining manageable device complexity through modular architecture.
2Reliability
If transfer gates are positioned symmetrically around the photoelectric converter, then the structure is balanced and simple, but point fixed pattern noise occurs due to insufficient charge transfer control
Solution Approach 1:
The transfer gates are positioned asymmetrically relative to the photoelectric converter and floating diffusion region, with the first transfer gate located at a first position and the second transfer gate located at a second position. This asymmetric arrangement optimizes charge transfer control from different regions, reducing point fixed pattern noise while maintaining a relatively simple device structure through strategic positioning rather than complex multi-component architecture.
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 configuration effectively prevents backflow and reduces point fixed pattern noise, improving the overall performance and image quality of the image sensor.
Implementation Method 1
The photodiode serves to convert incident light into an electrical signal
Data Source
AI summary
The present disclosure relates to semiconductor device. One example semiconductor device includes a plurality of unit pixels, where each unit pixel of the plurality of unit pixels includes a pair of transfer gates including a first transfer gate and a second transfer gate, a photoelectric converter, and a floating diffusion region spaced apart from the photoelectric converter. The first transfer gate and the second transfer gate are disposed asymmetrically with respect to the photoelectric converter and the floating diffusion region.