Image Sensor Isolation Grid With Conductive Oxide DTI
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Solution Overview
Problem
Image sensor devices face challenges with optical crosstalk, reduced quantum efficiency, and excessive dark current due to metallic structures and deep trench isolation (DTI) limitations, particularly as devices become smaller.
Innovation Solution
The implementation of a conductive oxide film within the DTI structure, selected from transparent conductive oxides like indium tin oxide, which enables efficient voltage biasing and total reflection of incident light without degrading quantum efficiency, thereby reducing crosstalk and improving dark performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic structures are used in image sensor devices, then electrical conductivity is improved, but optical crosstalk increases and quantum efficiency decreases
Solution Approach 1:
The patent changes the material parameter from metallic to conductive oxide, which fundamentally alters the optical properties while maintaining electrical conductivity. The conductive oxide has different refractive index and optical absorption characteristics compared to metals, thereby reducing optical crosstalk and improving quantum efficiency while preserving the necessary electrical conductivity for device operation
Solution Approach 2:
The patent employs a composite structure consisting of multiple conductive oxide layers with different properties. This composite material approach allows optimization of both electrical conductivity and optical performance by combining materials with complementary characteristics, achieving a balance between electrical function and optical transparency/low-crosstalk
2Object-affected harmful factors
If deep trench isolation (DTI) structure is implemented, then optical isolation is improved, but manufacturing complexity increases
Solution Approach 1:
The patent modifies the DTI structure by replacing metallic fill materials with conductive oxide materials. This parameter change simplifies the manufacturing process by eliminating the need for complex metal deposition and patterning steps, while maintaining the optical isolation function through the inherent properties of conductive oxides
Solution Approach 2:
The patent extracts the metallic material from the DTI structure and replaces it with conductive oxide. This extraction simplifies the overall device architecture by removing the need for complex metal interconnection layers within the isolation trenches, reducing manufacturing steps while preserving the essential optical isolation capability
3Productivity
If device size is reduced, then integration density is improved, but dark current increases
Solution Approach 1:
The patent changes the material composition to conductive oxide, which has different electrical properties including lower noise characteristics. This material parameter change helps suppress dark current generation in miniaturized devices by providing better charge carrier control and reducing thermal generation effects that become more pronounced at smaller dimensions
Solution Approach 2:
The patent applies conductive oxide materials specifically in the DTI regions surrounding the pixel elements. This localized application provides enhanced electrical control at the critical interfaces where dark current generation occurs, without affecting the overall pixel structure and allowing continued miniaturization while maintaining low dark current performance
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 conductive oxide film in the DTI structure effectively minimizes crosstalk, enhances quantum efficiency, and reduces dark current, leading to improved image sensor performance while being compatible with existing grid structures.
Implementation Method 1
total reflection of incident light
Implementation Method 2
enables efficient voltage biasing
Data Source
AI summary
An image sensor device and methods of forming an image sensor device are provided. The image sensor device includes a plurality of image-sensing elements arranged within the device substrate. The image sensor device further includes an isolation grid structure extending into the device substrate and made up of a plurality of isolation grid segments that surround the outer perimeters of the plurality of image-sensing elements. The isolation grid structure includes a passivation liner and a conductive material in contact with the passivation liner. The conductive material may be an indium-tin-oxide film.