Image Sensor Isolation Trench Layout for Uniform Bias Coverage
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Solution Overview
Problem
Current image sensors face challenges in achieving uniformity and reliability due to the decreasing size of pixels and components, leading to issues with photoelectric charge accumulation and dark current generation.
Innovation Solution
The image sensor design incorporates a substrate with a photoelectric conversion region and isolation regions featuring a trench, semiconductor patterns, insulating films, and conductive patterns to ensure uniform coverage and application of a negative bias voltage, which helps in reducing dark current by preventing electron diffusion across interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the size of pixels and components is decreased to increase degree of integration, then productivity and integration density are improved, but manufacturing precision and reliability deteriorate due to non-uniform conductor coverage and increased dark current
Solution Approach 1:
The conductor is divided into multiple segments: a first conductor at the bottom, a second conductor in the middle, and a third conductor at the top. This segmentation allows each conductor layer to be independently formed and optimized, ensuring uniform coverage even as pixel size decreases. The multi-layer conductor structure compensates for the difficulty of achieving uniformity in smaller dimensions by distributing the coverage function across multiple layers.
Solution Approach 2:
The solution transitions from a single-plane conductor to a three-dimensional multi-layer conductor structure. By adding vertical dimensionality with conductors at different heights (first, second, and third conductors), the patent achieves comprehensive interface coverage that cannot be obtained with a single flat conductor layer, thereby maintaining manufacturing precision at higher integration densities.
2Productivity
If the size of pixels and components is decreased to increase degree of integration, then productivity and integration density are improved, but reliability deteriorates due to increased dark current generation
Solution Approach 1:
The conductor is divided into multiple segments: a first conductor at the bottom, a second conductor in the middle, and a third conductor at the top. This segmentation allows each conductor layer to be independently formed and optimized, ensuring uniform coverage even as pixel size decreases. The multi-layer conductor structure compensates for the difficulty of achieving uniformity in smaller dimensions by distributing the coverage function across multiple layers.
Solution Approach 2:
The solution transitions from a single-plane conductor to a three-dimensional multi-layer conductor structure. By adding vertical dimensionality with conductors at different heights (first, second, and third conductors), the patent achieves comprehensive interface coverage that cannot be obtained with a single flat conductor layer, thereby maintaining manufacturing precision at higher integration densities.
3Reliability
If a conductor is formed to cover the entire interface of the photoelectric conversion region, then reliability is improved by reducing dark current, but device complexity increases due to additional conductor layers
Solution Approach 1:
The patent merges multiple conductor layers (first, second, and third conductors) into a unified multi-layer conductor structure that works together to achieve comprehensive interface coverage. By combining these layers, the patent achieves reliable dark current suppression while the conductors share common material properties and formation processes, thereby managing complexity through functional integration.
Solution Approach 2:
The multi-layer conductor structure serves multiple functions: it provides comprehensive interface coverage, suppresses dark current, and maintains electrical connectivity. Each conductor layer contributes to the overall function of interface coverage and dark current suppression, making the complex structure universally beneficial for reliability improvement.
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 design enhances the reliability and performance of image sensors by maintaining uniformity and reducing dark current, thereby improving the quality of image signals.
Implementation Method 1
a conductive pattern covering an inner wall of an upper portion of the insulating film and an uppermost surface and an inner wall of the second semiconductor pattern and configured to receive a negative bias voltage
Implementation Method 2
Each pixel outputs an image signal from light energy. Each of the plurality of pixels accumulates photoelectric charges corresponding to the amount of light incident through a photoelectric conversion element
Data Source
AI summary
Provided is an image sensor including a substrate including a first photoelectric conversion region, and an isolation region arranged in the substrate vertically from the first surface and defining the first photoelectric conversion region, wherein the isolation region includes a first semiconductor pattern conformally covering an inner wall of a trench, an insulating film conformally covering an inner wall of the first semiconductor pattern, a second semiconductor pattern conformally covering an inner wall of a lower portion of the insulating film, and a conductive pattern covering an inner wall of an upper portion of the insulating film and an uppermost surface and an inner wall of the second semiconductor pattern, wherein a vertical distance from the first surface to the uppermost surface of the first semiconductor pattern is substantially the same as a vertical distance from the first surface to the uppermost surface of the conductive pattern.