Image Sensor Pyramidal Surface Structure for Low Dark Current
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Solution Overview
Problem
CMOS image sensors face issues with plasma damage and non-uniformity due to dry etching processes used for absorption enhancement structures, leading to increased dark current and photo response non-uniformity, which degrade image quality.
Innovation Solution
The use of wet etching processes to form pyramidal shaped topographical features with substantially flat surfaces on the substrate, which reduces plasma damage and enhances light absorption while maintaining uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dry etching processes are used to form absorption enhancement structures, then light absorption is enhanced, but plasma damage increases causing dark current and non-uniformity
Solution Approach 1:
The patent changes the etching process parameter from dry etching to wet etching. This parameter change eliminates plasma damage while maintaining the light absorption enhancement function through pyramidal structures with flat tops formed by wet chemical etching processes.
2Illumination intensity
If dry etching is used for absorption enhancement structures, then light absorption improves, but photo response non-uniformity increases
Solution Approach 1:
The patent changes the etching methodology from dry to wet etching, which provides better control over etching uniformity. The wet etching process creates pyramidal structures with flat tops that exhibit more consistent photo response across the sensor array, reducing non-uniformity.
3Illumination intensity
If conical protrusions are formed by dry etching, then absorption enhancement is achieved, but dark current generation increases
Solution Approach 1:
The patent changes the etching process from dry to wet etching, which eliminates plasma-induced damage that generates dark current. The wet etching process forms pyramidal structures with flat tops that maintain light absorption enhancement while significantly reducing dark current generation.
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 approach decreases dark current generation by 80-90% and photo response non-uniformity by 20-80%, improving quantum efficiency and image quality compared to conical protrusions formed by dry etching.
Implementation Method 1
The use of wet etching processes to form pyramidal shaped topographical features with substantially flat surfaces on the substrate
Implementation Method 2
enhances light absorption while maintaining uniformity
Data Source
AI summary
The present disclosure, in some embodiments, relates to an image sensor integrated chip. The image sensor integrated chip includes a semiconductor substrate. One or more isolation structures are arranged within one or more trenches in the semiconductor substrate. The one or more trenches are disposed along opposing sides of a photo diode region within the semiconductor substrate. The semiconductor substrate includes an undulating exterior having rounded corners arranged laterally between neighboring ones of a plurality of flat surfaces. The rounded corners and the plurality of flat surfaces forming a plurality of triangular shaped protrusions arranged between the one or more isolation structures, as viewed along a cross-sectional view.