DTI Resonance Structure in Image Sensors for Pixel Crosstalk
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Solution Overview
Problem
As CMOS image sensors reduce pixel region size to increase resolution, crosstalk between adjacent pixels increases due to intervening layers with different refractive indices, degrading image quality by refracting incident light and causing it to travel laterally.
Innovation Solution
A semiconductor device with a deep trench isolation (DTI) structure featuring a textured lateral 2D resonance structure, where the DTI structure is laterally spaced apart from the radiation absorption region's outer border by a reflective length, reflecting incident light coherently back to the image sensor and reducing cross-talk between pixel regions, thereby enhancing quantum efficiency (QE) and modulation transfer function (MTF).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pixel region size is reduced to increase resolution, then image resolution is improved, but crosstalk between adjacent pixels increases due to refractive index differences in intervening layers
Solution Approach 1:
The patent introduces a resonance structure as an intermediary element positioned between adjacent pixel regions. This structure mediates the optical interaction by reflecting incident light back toward the image sensor before it can laterally refract into adjacent pixels through intervening layers with different refractive indices, thereby reducing crosstalk while maintaining high resolution
Solution Approach 2:
The patent modifies the optical path parameters by introducing a resonance structure with specific geometric dimensions and refractive index characteristics. By changing the structural parameters (depth, width, spacing) of the resonance structure, the patent optimizes light reflection properties to reduce crosstalk while preserving image resolution
2Object-generated harmful factors
If a resonance structure is introduced to reduce crosstalk, then cross-talk reduction and quantum efficiency are improved, but device complexity increases
Solution Approach 1:
The resonance structure is segmented into discrete elements positioned at specific locations between pixel regions. This segmentation allows the complex function of crosstalk reduction to be achieved through multiple simple, identical units rather than a single complex structure, facilitating easier fabrication and integration
Solution Approach 2:
The patent addresses the two-dimensional pixel array problem by introducing a vertical dimension through the resonance structure depth. This third dimension provides additional optical path control, enabling effective crosstalk reduction through vertical light reflection while maintaining the simplicity of the horizontal pixel layout
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 solution effectively reduces cross-talk between adjacent pixel regions, improving the quantum efficiency and modulation transfer function of the image sensor, leading to enhanced image quality by ensuring that incident light is reflected coherently back to the intended pixel, thus increasing the absorption of radiation and improving image sensor performance.
Implementation Method 1
An inner surface of the DTI structure is laterally spaced apart from the outer border of the array of protrusions by a reflective length that is based on the characteristic dimension of the array of protrusions
Implementation Method 2
reflecting incident light coherently back to the image sensor
Implementation Method 3
A radiation absorption region including an array of protrusions arranged along a first side of the substrate over the image sensing element
Data Source
AI summary
The present disclosure relates to a semiconductor device including a semiconductor substrate. A grid structure extends from a first side of the semiconductor substrate to within the semiconductor substrate. An image sensing element is disposed within the semiconductor substrate and is laterally surrounded by the grid structure. A plurality of protrusions are arranged along the first side of the semiconductor substrate. The plurality of protrusions are disposed over the image sensing element and are laterally surrounded by the grid structure. The plurality of protrusions are substantially identical to one another and have a characteristic dimension. An inner surface of the grid structure facing the image sensing element is spaced apart from a point of one of the plurality of protrusions by a predetermined reflective length that is based on the characteristic dimension of the plurality of protrusions.