Pixel Diffusion Wiring Layout for Low-Noise Imaging Elements
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Solution Overview
Problem
Current imaging elements face challenges in capturing clearer images with lower noise, especially in low illuminance environments, due to limitations in conversion efficiency and parasitic capacitance.
Innovation Solution
The imaging element incorporates a pixel design with a photoelectric conversion portion, charge transfer unit, diffusion layer with storage capacitance, and connection wiring that extends vertically to connect with the conversion unit, allowing for switching of storage capacitance to adjust conversion efficiency, thereby optimizing image capture in varying light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the connection wiring is formed closer to the semiconductor substrate, then parasitic capacitance is reduced and conversion efficiency is improved, but wiring layout flexibility is limited
Solution Approach 1:
The connection wiring is extended in the vertical direction (depth dimension) to connect the diffusion layer and conversion unit, allowing the wiring to be positioned closer to the substrate while maintaining layout flexibility through multi-layer routing
Solution Approach 2:
The connection wiring is embedded within the semiconductor substrate structure, nesting the wiring path inside the substrate to reduce parasitic capacitance while keeping the overall device structure organized and manageable
2Reliability
If storage capacitance is increased to improve signal strength, then noise performance is improved, but pixel area increases and saturation occurs more easily
Solution Approach 1:
The diffusion layer is designed with non-uniform doping concentration, creating regions of different storage capacitance within the same pixel. The high-doping region provides sufficient signal strength while the overall pixel area remains compact
Solution Approach 2:
The storage capacitance of the diffusion layer is dynamically adjusted by changing the doping concentration parameter. By optimizing the doping level, the pixel achieves adequate signal strength without excessive area or premature saturation
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 enables favorable image capture in low illuminance environments with reduced noise and saturation, suitable for applications like monitoring and vehicle-mounted systems.
Implementation Method 1
a photoelectric conversion portion configured to convert incident light to a charge by photoelectric conversion
Data Source
AI summary
A pixel is included, the pixel including a photoelectric conversion portion configured to convert incident light to a charge by photoelectric conversion and accumulate the charge, a charge transfer unit configured to transfer the charge generated in the photoelectric conversion portion, a diffusion layer to which the charge is transferred through the charge transfer unit, the diffusion layer having a predetermined storage capacitance, a conversion unit configured to convert the charge transferred to the diffusion layer to a pixel signal, and connection wiring configured to connect the diffusion layer and the conversion unit. The connection wiring is connected to the diffusion layer and the conversion unit through contact wiring extending in a vertical direction with respect to a semiconductor substrate on which the diffusion layer is formed and is formed closer to the semiconductor substrate than other wiring provided in the pixel.