Image Sensor Depletion Inducing Layer for Pixel Uniformity
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Solution Overview
Problem
Existing image sensors face challenges in achieving high-quality images with uniform pixel characteristics due to reduced pixel size, which leads to increased power routing paths and power voltage supply mismatch, resulting in variations in pixel characteristics.
Innovation Solution
The image sensor incorporates a pixel array with a photoelectric conversion element featuring a depletion inducing layer and a floating electrode buried in a trench within an inter-layer dielectric layer, which helps in securing full well capacitance and reducing pixel characteristic variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel size is reduced to increase pixel density, then productivity and resolution are improved, but power routing paths increase causing power voltage supply mismatch and pixel characteristic variations
Solution Approach 1:
The patent applies local quality by creating a depletion inducing layer with specific impurity concentration only in regions where photocharges are generated (under the color separation layer), rather than uniformly throughout the entire photoelectric conversion element. This localized doping approach addresses power voltage supply mismatch specifically at the critical interfaces where photocharges are collected, thereby maintaining pixel characteristic uniformity even as pixel size is reduced for higher density.
Solution Approach 2:
The patent changes the impurity concentration parameter locally within the photoelectric conversion element. By forming a depletion inducing layer with higher impurity concentration (1E16 to 1E18 atoms/cm³) in specific regions compared to the base impurity concentration (1E15 atoms/cm³), the patent optimizes the depletion region characteristics to ensure uniform pixel performance across high-density pixel arrays.
2Productivity
If pixel size is reduced to increase pixel density, then productivity is improved, but power routing paths increase leading to increased complexity in power supply management
Solution Approach 1:
The patent extracts the power supply management complexity from the pixel level by creating a depletion inducing layer that passivates interface states at the photoelectric conversion element interfaces. This reduces the need for complex power routing and voltage compensation circuits within each pixel, thereby maintaining device simplicity even as pixel density increases.
3Manufacturing precision
If depletion inducing layer is formed with ion implantation, then manufacturing precision is improved, but manufacturing process complexity increases due to additional process steps
Solution Approach 1:
The patent merges the depletion inducing layer formation with the existing color separation layer fabrication process. The depletion inducing layer is formed in the same semiconductor region where the color separation layer is subsequently deposited, combining multiple functions (photocharge generation, color separation, and depletion region control) into a unified structural approach that simplifies overall manufacturing despite the precision requirements.
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 enhances the sensitivity and uniformity of pixel characteristics, enabling the production of high-quality images by ensuring full depletion of the photoelectric conversion element and reducing variations in pixel characteristics.
Implementation Method 1
one or more depletion inducing layers formed in the photoelectric conversion element
Implementation Method 2
a substrate including a photoelectric conversion element
Data Source
AI summary
An image sensor may include a pixel array where a plurality of unit pixels are arranged in a two dimensional matrix, wherein each of the unit pixels includes: a substrate including a photoelectric conversion element; one or more depletion inducing layers formed in the photoelectric conversion element; an inter-layer dielectric layer formed over the substrate; and one or more floating electrodes formed in the inter-layer dielectric layer to overlap each of the depletion inducing layers.