Image Sensor Pixel Division Air Spacer Light Efficiency
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Solution Overview
Problem
Image sensors with pixel division structures face challenges in reducing dark current and enhancing light efficiency due to high light absorption rates of polysilicon cores and high refractive indices of nitride lateral patterns, which decrease light efficiency.
Innovation Solution
Incorporating a lateral pattern structure with an air spacer having a low refractive index on the sidewall of the core, alongside a nitride lateral pattern with a high refractive index, to capture electrons and reduce dark current while increasing light efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polysilicon core is used in the pixel division structure, then electrons can be captured to decrease dark current, but light absorption increases so that light efficiency decreases
Solution Approach 1:
The lateral pattern structure is divided into multiple segments: a first lateral pattern (oxide material) on the lower portion of the core sidewall, and a second lateral pattern (nitride material) on the upper portion. This segmentation allows different materials to perform different functions - the oxide layer captures electrons to reduce dark current while the nitride layer with high refractive index improves light efficiency by reducing light loss at interfaces.
2Use of energy by moving object
If a nitride lateral pattern with high refractive index is used, then light efficiency can be improved, but dark current increases due to electron flow at the boundary
Solution Approach 1:
Different materials are applied to different local regions of the core sidewall based on functional requirements. The first lateral pattern using oxide material is applied to the lower portion where electron capture is critical for dark current reduction. The second lateral pattern using nitride material is applied to the upper portion where optical performance is prioritized. This local quality differentiation resolves the contradiction by optimizing each region for its primary function.
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 decreases dark current and enhances light efficiency by utilizing the air spacer's low refractive index to improve reflectivity and the nitride's high refractive index to capture electrons, resulting in improved image sensor performance.
Implementation Method 1
the lateral pattern structure includes a first lateral pattern on a sidewall of a lower portion of the core; an air spacer on the first lateral pattern; and a second lateral pattern on outer sidewalls of the first lateral pattern and on outer sidewalls of the air spacer
Implementation Method 2
the nitride's high refractive index to capture electrons
Data Source
AI summary
An image sensor includes a pixel division structure, a light sensing element, a planarization layer, a color filter array layer, and a microlens. The pixel division structure extends through a substrate in a vertical direction, and defines unit pixel regions where unit pixels are formed. The light sensing element is in each unit pixel region. The planarization layer is on the substrate. The color filter array layer including color filters is on the planarization layer. The microlens is on the color filter array layer. The pixel division structure includes a core extending in the vertical direction and a lateral pattern structure on a sidewall thereof. The lateral pattern structure includes a first lateral pattern on a sidewall of a lower portion of the core, an air spacer on the first lateral pattern, and a second lateral pattern on outer sidewalls of the first lateral pattern and the air spacer.