Segmented Pixel Isolation Stack for Higher-Quantum-Efficiency Image Sensors
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Solution Overview
Problem
Existing image sensors face challenges in enhancing performance, particularly in reducing light absorption in pixel isolation portions and improving quantum efficiency.
Innovation Solution
The image sensor incorporates a substrate with pixel regions separated by a pixel isolation portion that includes insulation layers, a conductive layer, and an inner layer with different materials and stacking structures, reducing light absorption and enhancing light reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel isolation portion is used, then pixel regions are separated, but light is absorbed in the conductive layer reducing quantum efficiency
Solution Approach 1:
The pixel isolation portion is divided into multiple segments: a first conductive layer for electrical connection, a second conductive layer for additional isolation, and an insulating layer between them. This segmentation allows each layer to perform its specific function optimally while reducing overall light absorption compared to a single thick conductive layer.
Solution Approach 2:
An insulating layer is introduced as an intermediary between the first and second conductive layers. This insulating layer reduces the total light absorption by providing a non-absorbing medium in the isolation structure, while still maintaining electrical isolation and structural integrity.
2Reliability
If pixel isolation portion penetrates substrate, then pixel regions are effectively separated, but dark current and crosstalk increase
Solution Approach 1:
The pixel isolation portion uses a composite structure combining conductive layers and insulating layers. The conductive layers provide electrical connection and isolation, while the insulating layer provides optical isolation and reduces dark current. This composite material approach addresses both the separation effectiveness and the harmful effects simultaneously.
3Ease of manufacture
If single-layer conductive structure is used, then manufacturing is simple, but electrical insulation and light reflection are insufficient
Solution Approach 1:
The conductive structure is segmented into multiple layers with an insulating layer in between. This segmentation maintains manufacturing simplicity through sequential deposition processes while achieving the required electrical insulation and light reflection properties that a single layer cannot provide.
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
This configuration improves image sensing performance by increasing light reaching the photoelectric converter, reducing dark current and crosstalk, and simplifying the manufacturing process, thereby enhancing reliability and reducing costs.
Implementation Method 1
another part of the pixel isolation portion may be a part in which a total reflection is induced by the inner layer having a refractive index lower than a refractive index of the conductive layer
Data Source
AI summary
An image sensor includes a substrate including adjacent first and second pixel regions; a photoelectric converter at the substrate; and a pixel isolation portion separating the first and second pixel regions based on penetrating at least a part of the substrate between the first and second pixel regions. The pixel isolation portion includes first and second insulation portions respectively adjacent to the first and second pixel regions, and a conductive layer and an inner layer between the first and second insulation portions and including different materials. The pixel isolation portion includes a first portion including a portion where the conductive layer occupies a space between the first and second insulation portions in an intersection direction that intersects an extension direction of the pixel isolation portion, and a second portion including the conductive layer and the inner layer between the first and second insulation portions in the intersection direction.