Image Sensor Surface Texturing to Reduce Dark Current
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Solution Overview
Problem
CMOS image sensors suffer from plasma damage and non-uniformity issues due to dry etching processes used to form conical protrusions, leading to increased dark current and photo response non-uniformity, which degrade image quality.
Innovation Solution
Employing a wet etching process to create pyramidal shaped topographical features with substantially flat surfaces on the substrate, which reduces plasma damage and enhances absorption efficiency while maintaining uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dry etching process is used to form conical protrusions, then absorption efficiency is enhanced, but plasma damage increases and manufacturing uniformity deteriorates
Solution Approach 1:
The patent changes the etching process parameter from dry etching to wet etching, fundamentally altering the chemical and physical mechanisms involved. This parameter change eliminates plasma damage while maintaining the ability to form effective light absorption structures through chemical etching of pyramidal features on the silicon substrate surface.
Solution Approach 2:
The patent replaces the plasma-based dry etching mechanism with a wet chemical etching mechanism. This substitution eliminates the harmful plasma effects while achieving the desired surface topography modification through chemical reactions that selectively remove silicon material to form pyramidal structures.
2Reliability
If dry etching process is used to form conical protrusions, then absorption efficiency is enhanced, but photo response non-uniformity increases
Solution Approach 1:
The patent changes the etching process parameter from dry etching to wet etching, fundamentally altering the chemical and physical mechanisms involved. This parameter change eliminates plasma damage while maintaining the ability to form effective light absorption structures through chemical etching of pyramidal features on the silicon substrate surface.
3Object-affected harmful factors
If wet etching process is used to create pyramidal features, then dark current generation decreases, but manufacturing complexity increases
Solution Approach 1:
The patent extracts and removes the harmful plasma component from the etching process by completely replacing dry etching with wet etching. This extraction eliminates the source of plasma damage and dark current generation while using simpler wet chemical processes that are well-established in semiconductor manufacturing.
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
The wet etching process significantly decreases dark current generation by 80-90% and photo response non-uniformity by 20-80%, improving quantum efficiency and image quality.
Implementation Method 1
The substantially flat surfaces of the plurality of interior surfaces are formed by one or more wet etching processes
Implementation Method 2
a plurality of interior surfaces arranged directly over the image sensing element and defining a plurality of topographical features
Data Source
AI summary
The present disclosure, in some embodiments, relates to a method of forming an integrated chip. The method includes forming a masking layer on a first side of a substrate. A first etching process is performed on the first side of the substrate with the masking layer in place. The masking layer is removed. A second wet etching process is performed on the first side of the substrate after removing the masking layer. The first etching process and the second wet etching process collectively form a plurality of topographical features respectively having a triangular shape in a cross-section.