Deep Pixel Isolation Structure for Dark Current Suppression
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Solution Overview
Problem
Image sensors face challenges in suppressing dark current and improving photosensitivity due to issues like crystal defects and dangling bonds caused by etching damage, which lead to loss of light and deterioration of dark current characteristics.
Innovation Solution
The implementation of an image sensor design that includes a substrate with deep pixel isolation regions, amorphous regions adjacent to these regions, and electron suppression regions doped with boron ions to prevent electron migration and diffusion, thereby enhancing dark current characteristics and photosensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep pixel isolation regions are formed by etching, then pixel areas are separated effectively, but crystal defects and dangling bonds are created causing dark current increase
Solution Approach 1:
An amorphous region is introduced as an intermediary layer between the deep pixel isolation region and the pixel area. This amorphous region acts as a mediator that prevents direct interaction between electrons and the defective crystalline silicon at the isolation region boundary, thereby suppressing dark current while maintaining effective pixel separation.
Solution Approach 2:
The patent changes the physical and chemical parameters of the silicon substrate by creating an amorphous phase (different from the crystalline phase) in the region adjacent to the deep pixel isolation region. This phase change modifies the electrical properties, reducing electron migration and suppressing dark current generation at the isolation boundary.
2Ease of manufacture
If conventional isolation structures are used, then manufacturing is simpler, but photosensitivity is reduced due to light loss
Solution Approach 1:
The patent applies local quality by creating an amorphous region specifically in the area adjacent to the deep pixel isolation region, while maintaining crystalline silicon in the photoelectric conversion region. This localized structural modification improves dark current suppression and light handling in critical areas without affecting the overall manufacturing process or reducing photosensitivity.
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 effectively suppresses dark current and improves photosensitivity by blocking electron migration and preventing the diffusion of boron ions, leading to better light handling and reduced white spots in dark states.
Implementation Method 1
an electron suppression region between the amorphous region and the sidewall of the deep pixel isolation region. The electron suppression region may include boron ions
Implementation Method 2
The amorphous region may prevent diffusion of the boron ions
Data Source
AI summary
Image sensors are provided. An image sensor includes a substrate including a plurality of pixel areas. The substrate has a first surface and a second surface that is opposite the first surface. The image sensor includes a deep pixel isolation region extending from the second surface of the substrate toward the first surface of the substrate and separating the plurality of pixel areas from each other. The image sensor includes an amorphous region adjacent a sidewall of the deep pixel isolation region. Moreover, the image sensor includes an electron suppression region between the amorphous region and the sidewall of the deep pixel isolation region.