Pixel Transfer Gate Layout for Efficient Photocharge Readout
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Solution Overview
Problem
Current image sensing devices face inefficiencies in the transmission of photocharges from the photoelectric conversion region to the floating diffusion region, which affects the overall performance and integration of image sensors in various applications.
Innovation Solution
The image sensing device incorporates a pixel array with unit pixels isolated by device isolation regions, featuring a floating diffusion region that surrounds the transfer gate on multiple sides, enhancing the transfer paths and efficiency of photocharge transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the floating diffusion region is positioned adjacent to the transfer gate, then the transmission efficiency of the transfer transistor is improved, but the area occupied by the pixel circuit increases
Solution Approach 1:
The floating diffusion region is positioned to surround multiple side surfaces of the transfer gate in three-dimensional space, utilizing vertical and lateral dimensions simultaneously. This spatial arrangement maximizes the contact area between the floating diffusion region and transfer gate without requiring additional planar area, thereby improving transmission efficiency while maintaining compact pixel circuit layout.
Solution Approach 2:
The floating diffusion region is configured to surround the transfer gate structure, with portions of the floating diffusion region positioned at both sides of the transfer gate. This nested arrangement allows the floating diffusion region to effectively envelop the transfer gate, increasing the transmission interface area without occupying additional pixel circuit space.
2Reliability
If the floating diffusion region surrounds the transfer gate on multiple sides, then the photocharge transmission paths are enhanced, but the device complexity increases
Solution Approach 1:
The floating diffusion region is merged with the transfer gate structure by positioning it to surround multiple side surfaces of the transfer gate. This integration creates multiple transmission paths simultaneously, enhancing photocharge transmission reliability while avoiding the need for separate additional transmission structures, thereby controlling device complexity.
3Productivity
If the floating diffusion region is located adjacent to the transfer gate in both first and second directions, then the transmission efficiency is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The floating diffusion region is positioned to surround specific side surfaces of the transfer gate, creating localized high-quality transmission interfaces where needed. This selective positioning optimizes transmission efficiency at critical interfaces while allowing less stringent requirements in other areas, thereby managing overall manufacturing precision requirements.
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 improves the transmission efficiency of the transfer transistor, leading to better performance and integration of image sensors in devices such as digital cameras and surveillance systems.
Implementation Method 1
a photoelectric conversion region formed in a lower portion of the substrate within each unit pixel, and configured to generate photocharges by performing photoelectric conversion of incident light
Data Source
AI summary
An image sensing device is provided to include a plurality of unit pixel regions arranged in a first direction and a second direction, a first device isolation region structured to isolate the plurality of unit pixel regions from each other, a plurality of photoelectric conversion regions in the substrate to form a plurality of imaging pixels structured to generate photocharges, a plurality of second device isolation regions configured to define active regions of the plurality of imaging pixels, a plurality of floating diffusion regions formed in a first active region to store the photocharges, and a plurality of transfer gates structured to transmit the photocharges. The floating diffusion region is located contiguous to the transfer gate in the first direction and the second direction and is structured to surround a plurality of side surfaces of a corresponding transfer gate.