Hybrid Deep Trench Isolation for Low-Crosstalk Image Sensor Pixels
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Solution Overview
Problem
As image sensors are scaled down, optical cross talk between adjacent pixels becomes more significant, affecting the quality of images captured by CMOS image sensors.
Innovation Solution
A hybrid deep trench isolation (DTI) structure is introduced, which extends through the substrate and includes an upper conductive layer and a lower dielectric layer. This structure reflects incident light back to the corresponding pixel, reducing optical cross talk and increasing quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixels are scaled down to increase production efficiency and lower costs, then productivity improves, but optical cross talk between pixels increases
Solution Approach 1:
The patent introduces a deep trench isolation structure filled with dielectric material as an intermediary between adjacent pixels. This isolation structure physically separates the pixels and prevents optical signals from one pixel from interfering with adjacent pixels, thereby eliminating optical cross talk while allowing pixels to be scaled down for higher production efficiency.
2Object-affected harmful factors
If deep trench isolation structures are implemented to reduce optical cross talk, then optical cross talk is reduced, but device complexity increases
Solution Approach 1:
The patent divides the substrate into discrete pixel regions separated by deep trench isolation structures. Each pixel is segmented and isolated within its own defined region, preventing optical interference with adjacent segments. This segmentation approach systematically reduces optical cross talk while maintaining a manageable manufacturing process through standardized trench formation and fill procedures.
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 hybrid DTI structure effectively reduces optical cross talk between neighboring pixels, enhances quantum efficiency, and improves image integrity by minimizing signal noise ratio.
Implementation Method 1
This structure reflects incident light back to the corresponding pixel, reducing optical cross talk
Data Source
AI summary
An image sensor device is disclosed. The image sensor device includes a substrate having a plurality of pixel regions. Two adjacent pixel regions are optically and electrically isolated by a deep trench isolation structure. In an embodiment, a method of forming the deep trench isolation structure includes receiving a workpiece comprising a first isolation structure formed in a front side of a substrate, forming a trench extending through the first isolation structure and the substrate, forming a dielectric liner to line the trench, depositing a conductive layer conformally over the workpiece after the forming of the dielectric liner, and depositing a dielectric fill layer over the conductive layer to fill the trench. A refractive index of the dielectric fill layer may be smaller than a refractive index of the conductive layer. The present disclosure also includes an alternative method for forming isolation structures at a back side of the substrate.