Image Sensor Blockade Region for Dark Current Isolation
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Solution Overview
Problem
Semiconductor imaging devices face a challenge in reducing dark current, which degrades image quality by decreasing the signal-to-noise ratio due to unintended charge flow between the imaging and peripheral regions, caused by electrostatic coupling with digital circuitry.
Innovation Solution
An imaging device is designed with a blockade region containing doped regions and contact plugs between the imaging and peripheral regions to discharge excess charges and suppress electrostatic coupling, using a configuration that includes multiple doped regions and carbon-containing layers to control potential and reduce metal impurity diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an n-type sidewall structure is formed on a p-type substrate to electrically isolate the pixel array from peripheral circuitry, then dark current is reduced, but device complexity increases due to additional manufacturing steps and structural elements
Solution Approach 1:
The patent introduces a p-type barrier layer as an intermediary element between the imaging region and peripheral region. This barrier layer acts as a mediator that blocks electron diffusion from the peripheral n-type circuitry into the imaging region, thereby reducing dark current without requiring complex sidewall structures. The barrier layer is formed as a simple planar layer during standard CMOS processing steps.
Solution Approach 2:
The patent modifies the electrical parameters of the substrate by introducing a p-type barrier layer with specific doping concentration (1×10^16 to 1×10^18 atoms/cm³) and thickness (50 nm to 5 μm). This parameter change creates an electrical barrier that prevents charge leakage while maintaining compatibility with standard manufacturing processes, avoiding the need for complex three-dimensional sidewall structures.
2Productivity
If the imaging region and peripheral region are closely integrated to improve productivity, then manufacturing efficiency increases, but charge transfer between regions occurs causing degraded image quality
Solution Approach 1:
The p-type barrier layer serves as an intermediary region that physically and electrically separates the imaging region and peripheral region while allowing them to remain on the same substrate. This mediator prevents direct charge transfer between the two regions, enabling close integration for high productivity while maintaining image quality by blocking unintended charge flow.
Solution Approach 2:
The patent segments the substrate into distinct functional regions (imaging region and peripheral region) separated by the p-type barrier layer. This segmentation allows each region to operate independently with its own electrical characteristics, preventing charge interference while maintaining overall device integration and manufacturing efficiency.
3Adaptability or versatility
If digital circuitry is placed in the peripheral region to drive the pixels, then device functionality is enhanced, but electrostatic coupling causes noise that decreases the signal-to-noise ratio
Solution Approach 1:
The p-type barrier layer acts as an electrical mediator that isolates the sensitive imaging region from the noisy peripheral digital circuitry. This intermediary blocks electrostatic coupling and noise transmission from the digital circuits to the pixel array, allowing full device functionality while preserving signal-to-noise ratio for high-quality imaging.
Solution Approach 2:
The patent extracts the digital circuitry into a separate peripheral region and introduces the p-type barrier layer to remove the harmful electrostatic coupling effect. This extraction approach allows the digital circuits to perform their driving function while the barrier layer removes the unwanted noise influence on the imaging region.
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 effectively suppresses dark current, improving image quality by reducing noise and maintaining high signal-to-noise ratios, while also minimizing the diffusion of metal impurities that can degrade image quality.
Implementation Method 1
a p-type barrier layer which extends from a surface of the semiconductor substrate and under the isolation
Implementation Method 2
each pixel including a photoelectric conversion layer, a pixel electrode to collect a charge generated in the photoelectric conversion layer
Data Source
AI summary
An exemplary imaging device according to the present disclosure includes: an imaging region including a plurality of pixels; a peripheral region located outside of the imaging region; and a blockade region located between the imaging region and the peripheral region. Each of the plurality of pixels includes a photoelectric conversion layer, a pixel electrode to collect a charge generated in the photoelectric conversion layer, and a first doped region electrically connected to the pixel electrode. In the peripheral region, a circuit to drive the plurality of pixels is provided. The blockade region includes a second doped region of a first conductivity type located between the imaging region and the peripheral region and a plurality of first contact plugs connected to the second doped region.