Image Sensor Transfer Gate Contacting Device Isolation Layer
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Solution Overview
Problem
As the integration density of image sensors increases, the size of each pixel or photodiode becomes smaller, leading to reduced light incidence and sensitivity.
Innovation Solution
The image sensor design includes a substrate with a device isolation layer, a photoelectric conversion layer, a floating diffusion region, and a transfer gate that is in contact with the device isolation layer, optimizing the active region structure to enhance light transfer and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the integration density of image sensors is increased to reduce pixel size, then the device complexity is reduced and more pixels can be packed, but the light incidence amount decreases and sensitivity deteriorates
Solution Approach 1:
The transfer gate extends in the vertical direction (depth dimension) by contacting the device isolation layer, creating a three-dimensional structure that increases the photocharge transfer path length without increasing the horizontal pixel area. This dimensional transition allows maintaining high integration density while improving sensitivity through enhanced light transfer efficiency.
Solution Approach 2:
The device isolation layer serves as an intermediary structure that the transfer gate contacts to improve photocharge transfer. By extending the transfer gate to contact the device isolation layer, the transfer path is optimized, reducing photocharge loss and improving sensitivity without requiring larger pixel areas.
2Area of stationary object
If the pixel size is reduced to increase integration density, then more pixels can be arranged, but the amount of incident light decreases leading to photocharge loss
Solution Approach 1:
The transfer gate structure transitions from a two-dimensional planar configuration to a three-dimensional structure by extending vertically to contact the device isolation layer. This increases the transfer path length and cross-sectional area for photocharge transport, reducing photocharge loss even when the horizontal pixel area is minimized for high integration density.
Solution Approach 2:
The transfer gate dimensions are optimized by extending its length to contact the device isolation layer, changing the geometric parameters of the transfer path. This parameter modification increases the transfer efficiency and reduces photocharge loss without requiring an increase in the overall pixel area.
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 increases the sensitivity of image sensors, allowing for improved image capture in low illumination environments by reducing photocharge loss and optimizing the transfer path.
Implementation Method 1
a photoelectric conversion layer in the substrate
Data Source
AI summary
An image sensor includes a substrate including an active region defined by a device isolation layer, a photoelectric conversion layer in the substrate, a floating diffusion region in the substrate at an edge of the active region, and a transfer gate on the active region. The transfer gate is in contact with a portion of the device isolation layer adjacent the active region.