Dual Conversion Gain Gate Structure for Image Sensor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing image sensors face limitations in adjusting conversion gain efficiently, which affects their ability to optimize image capture under varying light conditions.
Innovation Solution
The implementation of a dual conversion gain (DCG) gate structure in unit pixels of image sensors, featuring a vertical gate design with a rounded corner and multiple bottom portions, allows for adjustable capacitance and enhanced photocharge transfer between floating diffusion regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional floating diffusion region structure is used, then the device complexity is low, but the conversion gain cannot be effectively adjusted
Solution Approach 1:
The floating diffusion region is divided into multiple segments (first floating diffusion region and second floating diffusion region) with different capacitance values. The DCG gate can selectively connect to different segments, enabling adjustable conversion gain by changing which segment is active, thus resolving the contradiction between adaptability and device complexity.
Solution Approach 2:
The DCG gate structure enables dynamic switching between different floating diffusion regions based on lighting conditions. By controlling the connection between the photoelectric conversion region and different floating diffusion regions, the conversion gain can be dynamically adjusted, achieving high adaptability without excessive structural complexity.
2Adaptability or versatility
If the photoelectric conversion region area is reduced to adjust conversion gain, then the device complexity is reduced, but the light capture capability deteriorates
Solution Approach 1:
Instead of adjusting conversion gain by changing the area of the photoelectric conversion region (two-dimensional adjustment), the invention introduces a third dimension - multiple floating diffusion regions with different capacitance values connected via the DCG gate. This allows conversion gain adjustment without compromising the photoelectric conversion region area, thus maintaining light capture capability while achieving adaptability.
3Manufacturing precision
If a vertical DCG gate structure with rounded corner is formed, then the manufacturing precision is improved, but the device complexity increases
Solution Approach 1:
The DCG gate structure incorporates a rounded corner at the bottom of the vertical gate. This curvature design improves manufacturing precision by reducing stress concentration and facilitating more uniform material deposition and etching processes during fabrication, while the overall vertical structure maintains relatively simple geometry.
Solution Approach 2:
The DCG gate structure is formed within a recess that is filled with conductive material. The gate structure is nested within the substrate, with the rounded corner fitting into the recess geometry. This nested configuration allows for precise formation through standard semiconductor fabrication processes while managing the complexity of the three-dimensional structure.
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 enables effective adjustment of conversion gain without reducing the photoelectric conversion region's area, improving image sensor performance across different illumination levels.
Implementation Method 1
a photoelectric conversion region in a substrate and configured to generate a photo-charge according to incident light
Implementation Method 2
a dual conversion gain (DCG) gate spaced apart from the first floating diffusion region and the second floating diffusion region, and extending perpendicularly or substantially perpendicularly into the substrate with respect to a first surface of the substrate, wherein the transfer gate is configured to transfer the photo-charge from the photoelectric conversion region to the first floating diffusion region, and wherein the DCG gate is configured to transfer the generated photo-charge from the first floating diffusion region to the second floating diffusion region
Data Source
AI summary
Provided are a unit pixel, an image sensor including the same, a portable electronic device including the same, and a method of manufacturing the same. The method of manufacturing includes: forming a photoelectric conversion region in a substrate; forming, in the substrate, a first floating diffusion region spaced apart from the photoelectric conversion region of the substrate, and a second floating diffusion region spaced apart from the first floating diffusion region; forming a first recess spaced apart from the first floating diffusion region and the second floating diffusion region by removing a portion of the substrate from a first surface of the substrate; filling the first recess to form a dual conversion gain (DCG) gate that extends perpendicularly or substantially perpendicularly from the first surface of the substrate; and forming a conductive layer to fill an inside of the first recess.