Solid-State Imaging Device Charge Accumulation Gradient
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Solution Overview
Problem
In solid-state imaging devices, there is a tradeoff between increasing the saturation charge quantity and speeding up charge transfer, as enlarging the charge-accumulating unit size to increase saturation charge quantity leads to longer transfer times, potentially causing image lag and inhibiting speed-up of imaging.
Innovation Solution
The device includes charge-discharging units aligned with charge-accumulating units to discharge excess charges and prevent blooming, with a configuration where the charge-discharging units share a drain region and have a gate region to control charge flow, and the charge-accumulating units have a gradually changing impurity concentration to accelerate charge migration without inhibiting size enlargement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charge-accumulating unit size is enlarged to increase saturation charge quantity, then the saturation charge quantity is improved, but the charge transfer time becomes longer
Solution Approach 1:
The patent applies local quality by creating a non-uniform impurity concentration distribution within the charge-accumulating unit. Specifically, the impurity concentration is designed to gradually decrease from the bottom surface toward the light-receiving surface, creating regions with different electrical properties. This gradient structure accelerates charge migration in specific areas without requiring a complete redesign of the entire charge-accumulating unit, thus increasing saturation charge quantity while maintaining efficient charge transfer.
Solution Approach 2:
The patent implements dynamics by making the charge transfer process adaptable through the impurity concentration gradient. The varying impurity concentration creates dynamic electric field conditions that optimize charge migration speed at different depths. This dynamic structure allows the system to handle both large charge quantities and maintain transfer speed, resolving the contradiction between saturation charge quantity and transfer time.
2Quantity of substance
If the charge-accumulating unit size is enlarged to increase saturation charge quantity, then the saturation charge quantity is improved, but imaging speed is inhibited
Solution Approach 1:
By introducing local quality variations through the impurity concentration gradient, the patent creates optimized regions for charge accumulation and transfer within the enlarged charge-accumulating unit. This allows the unit to maintain large size for high saturation charge quantity while specific regions facilitate rapid charge transfer, preserving imaging speed.
3Quantity of substance
If gate electrodes are applied with electric potential to increase potential in the second direction, then charge accumulation is improved, but charge transfer speed is reduced
Solution Approach 1:
The patent applies parameter changes by modifying the impurity concentration parameter within the charge-accumulating unit. Instead of relying solely on gate electrode potentials, the impurity concentration gradient creates inherent electric field variations that facilitate both charge accumulation and rapid transfer. This parameter modification allows the system to achieve both goals without the tradeoff imposed by gate electrode control alone.
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 allows for both increased saturation charge quantity and accelerated charge transfer, preventing image lag and blooming while maintaining efficient imaging speed.
Implementation Method 1
a plurality of charge-accumulating units, each being adapted to accumulate a charge generated in the corresponding photoelectric converting units; wherein each of the plurality of charge-accumulating units includes a gradually changing impurity concentration in a second direction
Implementation Method 2
each being adapted to accumulate a charge generated in the corresponding photoelectric converting units; and a charge-output unit adapted to obtain charges respectively transferred from the plurality of charge-accumulating units
Implementation Method 3
a plurality of photoelectric converting units aligned in a first direction; a plurality of charge-accumulating units, each being aligned with the corresponding photoelectric converting unit
Data Source
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AI summary
A solid-state imaging device SI includes a plurality of photoelectric converting units and a plurality of charge-accumulating units each accumulating a charge generated in the corresponding photoelectric converting unit. The photoelectric converting unit includes a photosensitive region that generates the charge in accordance with light incidence, and an electric potential gradient forming unit that accelerates migration of charge in a second direction D2 in the photosensitive region. The charge-accumulating unit includes: a plurality of regions (semiconductor layers) 22, 23, 24 having an impurity concentration gradually changed in one way in the second direction D2, and electrodes 32, 33 adapted to apply electric fields to the plurality of regions 22, 23, 24. The electrode 32 is disposed over the plurality of regions 22, 23 having the impurity concentration gradually varied. The electrode 33 is disposed over the plurality of regions 23, 24 having the impurity concentration gradually varied.