Image Sensor Transfer Gate Potential for Higher Saturation Charge
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As solid-state image pickup devices are miniaturized and the number of pixels increases, the area occupied by the photodiode decreases, leading to reduced saturation electric charges, which lowers image quality and can result in residual images due to incomplete charge transfer.
Innovation Solution
Increasing the potential difference under the transfer gate by doping the accumulation region side with ions of the first conductivity type impurities, allowing for enhanced capacity and saturation charge levels without generating residual images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of pixels is increased and the device is miniaturized, then the pixel density and integration are improved, but the photodiode area decreases and saturation electric charge amount is reduced
Solution Approach 1:
The patent applies local quality by creating a potential depth difference specifically in the accumulation region where charges are stored. By doping the accumulation region with first conductivity type impurities to form a potential depth difference, the invention locally enhances charge storage capacity without affecting the overall photodiode area, thus resolving the contradiction between miniaturization and charge capacity.
Solution Approach 2:
The patent changes the electrical parameters of the accumulation region by introducing doping with first conductivity type impurities. This creates a potential depth difference that increases the capacity for storing signal electric charges, effectively increasing the saturation electric charge amount without changing the physical dimensions of the photodiode, thereby resolving the contradiction between miniaturization and charge capacity.
2Volume of moving object
If the photodiode area is decreased for miniaturization, then device integration is improved, but image quality deteriorates due to reduced saturation electric charges
Solution Approach 1:
The invention applies local quality by enhancing the charge storage capability specifically in the accumulation region through doping. This localized modification allows the photodiode to maintain sufficient saturation electric charge capacity for high image quality while the overall device size is reduced for miniaturization and high integration.
Solution Approach 2:
The patent changes the electrical parameters of the accumulation region by introducing doping with first conductivity type impurities, creating a potential depth difference that increases charge storage capacity. This parameter change allows the photodiode to maintain high saturation electric charge levels for good image quality despite reduced physical size.
3Quantity of substance
If the saturation electric charge amount is increased by doping, then charge storage capacity is improved, but residual images may occur due to incomplete charge transfer
Solution Approach 1:
The patent applies local quality by creating a potential depth difference specifically in the accumulation region through doping. This localized potential enhancement increases charge storage capacity while the potential difference itself facilitates complete charge transfer to the floating diffusion region, preventing residual images and resolving the contradiction between charge capacity and transfer completeness.
Solution Approach 2:
The invention changes the electrical parameters of the accumulation region by introducing doping with first conductivity type impurities, creating a potential depth difference. This parameter change simultaneously increases charge storage capacity and ensures complete charge transfer by establishing an appropriate potential gradient, thereby preventing residual images.
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 approach effectively increases the saturation electric charge capacity of the photodiode, ensuring complete charge transfer and maintaining image quality even as devices are miniaturized and pixel density increases, preventing residual images.
Implementation Method 1
a photoelectric-converting portion (photodiode PD, sensor portion) for photoelectrically converting incident light into signal electric charges and accumulating the thus photoelectrically-converted signal electric charges
Implementation Method 2
Increasing the potential difference under the transfer gate by doping the accumulation region side with ions of the first conductivity type impurities
Data Source
AI summary
A solid-state image pickup device comprises a plurality of pixels arrayed in an XY matrix fashion, each pixel including a photoelectric-converting portion 1 for photoelectrically converting incident light into signal electric charges and accumulating therein the thus photoelectrically-converted signal electric charges, an accumulation region 3 for converting the thus accumulated signal electric charges into a voltage and a transfer gate 2 for transferring the signal electric charges accumulated in this photoelectric-converting portion 1 to the accumulation region 3, wherein an amount of saturation electric charges is increased by forming a difference in potential level under the transfer gate 2.