Image Sensor Transparent Conductive Layer Dark Current Reduction
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Solution Overview
Problem
CMOS image sensors face challenges in reducing dark current, which affects their performance and image quality, particularly due to issues with charge leakage and light interference.
Innovation Solution
The design incorporates a substrate with an active region and a dummy region, featuring a transparent conductive layer and a light-blocking layer with a grid structure, which helps in managing charge distribution and reducing dark current by effectively blocking light and discharging positive charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transparent conductive layer is added to the substrate surface, then charge distribution is improved and dark current is reduced, but device structure becomes more complex
Solution Approach 1:
The transparent conductive layer serves multiple functions simultaneously: it acts as an electrode for charge management, maintains electrical connection across the substrate surface, and allows light transmission to reach the photodetectors. This multi-functionality reduces the need for separate components, thereby managing complexity while improving dark current properties.
Solution Approach 2:
The transparent conductive layer acts as an intermediary between the substrate and the light-blocking layer, providing a conductive pathway for charge management while allowing optical signals to pass through to the active regions. This mediator approach enables charge control without interfering with light detection.
2Reliability
If a light-blocking layer with grid structure is added, then light interference is reduced and image quality improves, but manufacturing complexity increases
Solution Approach 1:
The light-blocking layer is divided into a grid structure with multiple discrete blocking regions separated by light transmission regions. This segmentation allows light to pass through specific areas to the photodetectors while blocking light in other areas, reducing light interference and improving image quality through spatial differentiation.
Solution Approach 2:
Different regions of the light-blocking layer have different optical properties: the grid regions block light while the transmission regions allow light passage. This local variation in optical quality enables selective light management, improving image quality by preventing light leakage while maintaining transparency where needed.
3Reliability
If the transparent conductive layer is made highly conductive, then charge leakage is reduced, but light transmission is blocked
Solution Approach 1:
The transparent conductive layer uses materials and deposition parameters that achieve sufficient electrical conductivity for charge management while maintaining optical transparency. By carefully controlling the conductivity parameter within an optimal range, the layer provides charge leakage control without significantly blocking light transmission to the photodetectors.
Solution Approach 2:
The transparent conductive layer employs composite material structures or specific material compositions that combine electrical conductivity with optical transparency. These specialized materials enable simultaneous charge management and light transmission by integrating multiple functional properties into a single layer.
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 the dark current property of the image sensor, enhancing its performance and image quality by effectively managing charge leakage and light interference.
Implementation Method 1
a light-blocking layer on the transparent conductive layer and electrically connected to the transparent conductive layer, the light-blocking layer having a grid structure adjacent light transmission regions
Implementation Method 2
a transparent conductive layer on a first surface of the substrate... A depth of the trench may be less than a thickness of the substrate
Data Source
AI summary
An image sensor is disclosed. The image sensor includes a substrate including an active region and a dummy region, a plurality of unit pixels on the active region, a transparent conductive layer on a first surface of the substrate, a light-blocking layer on the transparent conductive layer and electrically connected to the transparent conductive layer, the light-blocking layer having a grid structure adjacent light transmission regions, and a pad electrically connected to the light-blocking layer, on the dummy region.