Pixel Array Layout With Shared Floating Diffusion for High Resolution
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Solution Overview
Problem
Current image sensors face challenges in increasing pixel resolution due to the limited pitch between pixels, which affects the area and sensitivity of the pixel structure.
Innovation Solution
A pixel array design where each pixel includes four subpixels with shared floating diffusion regions connected via internal wiring, allowing for increased capacitance and improved sensitivity, and an output circuit with transistors for efficient charge transfer and signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pitch between pixels is reduced to increase resolution, then the number of pixels increases, but the area and sensitivity of each pixel structure decreases
Solution Approach 1:
The patent merges multiple floating diffusion regions from different subpixels into a shared common floating diffusion region. This allows multiple photoelectric conversion units to share a single floating diffusion region, effectively increasing the useful area for charge storage and processing without increasing the physical pixel pitch, thereby resolving the contradiction between high resolution and sufficient pixel area.
Solution Approach 2:
The common floating diffusion region serves multiple functions: it acts as the charge storage node for multiple subpixels, the amplification node for multiple photodetectors, and the output node for multiple transmission gates. This multi-functionality allows the pixel structure to maintain high sensitivity and resolution performance with reduced pitch by eliminating redundant floating diffusion regions.
2Measurement precision
If the pitch between pixels is reduced to increase resolution, then the number of pixels increases, but the sensitivity of the pixel structure decreases
Solution Approach 1:
By merging multiple floating diffusion regions into a shared common floating diffusion region, the patent increases the effective capacitance available for charge storage and signal amplification. This enhanced capacitance improves the sensitivity and signal-to-noise ratio, counteracting the sensitivity loss that would normally result from reduced pixel area due to smaller pitch.
3Area of moving object
If floating diffusion regions are shared among subpixels via internal wiring, then the useful area increases and sensitivity improves, but the device complexity increases
Solution Approach 1:
The patent combines multiple floating diffusion regions into a single shared region, which eliminates the need for separate wiring connections to each floating diffusion region. Although internal wiring is required to connect photoelectric conversion units to the common floating diffusion region, the overall wiring complexity is reduced compared to having separate floating diffusion regions for each subpixel, as the shared architecture consolidates the connection points.
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 the resolution and sensitivity of the image sensor by increasing the useful area of each pixel and allowing for more efficient charge handling, leading to improved image quality and sensitivity.
Implementation Method 1
Image sensors generate an image of an object by using a photoelectric conversion device that reacts according to the intensity of light reflected by the object
Data Source
AI summary
A pixel array and an image sensor including the pixel array are provided. The pixel array included in the image sensor includes a plurality of pixels arranged in a matrix, and a plurality of column lines each commonly connected to pixels arranged on a same column from among the plurality of pixels. Each of the plurality of pixels includes four subpixels. Each of the four subpixels includes four photoelectric conversion devices; a floating diffusion region storing electric charges generated by the four photoelectric conversion devices; and four transmission gates configured to transmit the electric charges generated by the four photoelectric conversion devices to the floating diffusion region. Four floating diffusion regions included in the four subpixels are electrically connected to one another via internal wiring. Each of the plurality of pixels further includes a reset gate, a first driving gate and a first selection gate.