Inter-Pixel Trench Isolation With Low-Transmission Layer for Crosstalk
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Solution Overview
Problem
CMOS image sensors face challenges with crosstalk due to radiation passing between photodetectors, especially from hot carrier luminescence, which degrades signal-to-noise ratios and quantum efficiency, as existing trench isolation structures rely on total internal reflection that is angle-dependent.
Innovation Solution
An image sensor with an inter-pixel trench isolation structure defined by a low-transmission layer that blocks radiation regardless of angle, using materials like metal or conductive ceramics to ensure low transmission and high reflectance, thereby reducing crosstalk and enhancing signal-to-noise ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If total internal reflection is used for trench isolation, then radiation blocking is achieved, but angle-dependent performance degradation occurs
Solution Approach 1:
The patent changes the material parameter of the trench isolation from dielectric (relying on TIR) to metal or conductive ceramic with high reflectance. This parameter change transforms the radiation blocking mechanism from angle-dependent TIR to angle-independent reflective blocking, resolving the contradiction between achieving radiation blocking and maintaining reliable signal-to-noise ratio across all angles.
Solution Approach 2:
The patent substitutes the optical mechanism (TIR) with a material property-based mechanism (high reflectance of metals). Instead of relying on the mechanical/optical condition of total internal reflection at dielectric interfaces, the invention uses the inherent electromagnetic reflective properties of metal materials to block radiation, eliminating angle dependence.
2Ease of manufacture
If dielectric trench isolation is used, then manufacturing is simpler, but radiation transmission remains high
Solution Approach 1:
The patent employs composite material structures, specifically using metal or conductive ceramic materials within the trench isolation. These composite materials combine the structural function of trench filling with the electromagnetic function of high reflectance and low transmission, achieving both radiation blocking and manufacturability.
Solution Approach 2:
The invention changes the material composition parameter from dielectric to metal/conductive ceramic, fundamentally altering the electromagnetic interaction with radiation. This parameter change achieves low transmission and high reflectance while maintaining compatibility with standard semiconductor manufacturing processes.
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 low-transmission layer effectively blocks radiation between photodetectors, increasing signal-to-noise ratios and quantum efficiency by reducing crosstalk and reflecting radiation back to the photodetectors, improving overall performance.
Implementation Method 1
the low-transmission layer has low transmission for incident radiation 114 due to high absorption
Implementation Method 2
the low-transmission layer has high reflectance for incident radiation 114
Data Source
AI summary
Various embodiments of the present disclosure are directed towards an image sensor, and a method for forming the image sensor, in which an inter-pixel trench isolation structure is defined by a low-transmission layer. In some embodiments, the image sensor comprises an array of pixels and the inter-pixel trench isolation structure. The array of pixels is on a substrate, and the pixels of the array comprise individual photodetectors in the substrate. The inter-pixel trench isolation structure is in the substrate. Further, the inter-pixel trench isolation structure extends along boundaries of the pixels, and individually surrounds the photodetectors, to separate the photodetectors from each other. The inter-pixel trench isolation structure is defined by a low-transmission layer with low transmission for incident radiation, such that the inter-pixel trench isolation structure has low transmission for incident radiation. The low-transmission layer may, for example, be or comprise metal and/or some other suitable material(s).