Pixel Architecture Charge Storage via Gating Device Inversion Layer
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Solution Overview
Problem
Solid-state image sensors have a limited capacity for charge storage in their photodiodes, which restricts their performance in capturing images, and existing solutions are not cost and time efficient.
Innovation Solution
A pixel design that incorporates a gating device, such as a semiconductor capacitor, to enhance charge storage capacity by creating an inversion layer in the channel region, allowing for additional charge storage without increasing pixel size, using a 4T or 5T pixel core with a photodiode and transistors, and an overflow device to manage excess charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional photodiode structure is used, then the pixel structure is simple, but the charge storage capacity is limited
Solution Approach 1:
The pixel is divided into two distinct charge storage regions: a first charge storage region (photodiode) and a second charge storage region (gate structure). This segmentation allows each region to serve a specific function - the photodiode for primary charge generation and storage, and the gate structure for additional charge storage capacity - thereby increasing total charge storage capacity while maintaining a manageable structural complexity through functional specialization.
2Quantity of substance
If the pixel size is increased to store more charge, then the charge storage capacity increases, but the pixel area increases
Solution Approach 1:
The invention utilizes the vertical dimension by forming the gate structure over the photodiode region. The gate structure extends vertically above the photodiode, creating a three-dimensional charge storage architecture. This allows additional charge storage capacity to be achieved by utilizing vertical space rather than increasing the horizontal pixel area, effectively solving the contradiction between charge storage capacity and pixel area.
3Quantity of substance
If a gating device is added to increase charge storage, then the charge storage capacity increases, but the manufacturing complexity increases
Solution Approach 1:
The gate structure serves multiple functions simultaneously: it acts as a control electrode for the transfer transistor, provides additional charge storage capacity, and functions as a structural element of the pixel. By merging these functions into a single structure, the invention increases charge storage capacity without proportionally increasing manufacturing complexity, as the same structural element performs multiple roles in the pixel operation.
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
The solution effectively increases the charge storage capacity of image sensors, enabling improved image capture without significant increases in pixel size or production costs, while maintaining low dark leakage currents and efficient operation.
Implementation Method 1
The gating device may be biased to create an inversion layer in a channel region that accepts charges from the photodiode or the volume region below the gating device
Implementation Method 2
A pixel and method for storing charge in the pixel... pixel core is a four transistor (4T) pixel that includes a transfer transistor, a reset transistor, an amplifier, a select transistor, a photodiode... charges are also stored in the photodetector and the charge reception structure
Data Source
AI summary
In accordance with an embodiment, a gating device is connected to a pixel core. The gating device may include a control structure and one or more terminals, wherein the one or more terminals are commonly connected to each other and connected to the pixel core. Alternatively, the terminals may be connected to corresponding photodiodes.