Multi-Depth Trench Gate Layout for Smooth Image Charge Transfer
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Solution Overview
Problem
In solid-state imaging devices, there is a challenge in smoothly transferring electric charges from a photoelectric converter to a transfer destination due to potential dips, especially when the transfer section is in an off state, which can affect the reliability and efficiency of imaging performance.
Innovation Solution
The use of a transfer section with a first trench gate and a second trench gate, where the second trench gate has a shorter length than the first, extending from the front surface to the back surface of the semiconductor layer, helps to eliminate potential dips and ensure smooth charge transfer even when the transfer section is off, by increasing the modulation force on the photoelectric converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transfer section is in an off state, then the photoelectric converter can accumulate charges, but potential dips occur that hinder smooth charge transfer
Solution Approach 1:
The transfer gate is divided into multiple trench gates (first trench gate and second trench gate) with different depths extending into the photoelectric converter. This segmentation allows each trench gate to control potential at different depths, eliminating potential dips more effectively while maintaining a manageable structure.
Solution Approach 2:
Different trench gates are designed with different depths (the first trench gate extends deeper than the second trench gate) to create localized potential control at specific depths within the photoelectric converter. This local quality approach addresses potential dips at different depths independently, improving charge transfer reliability without requiring uniform complexity throughout the entire structure.
2Manufacturing precision
If the semiconductor layer thickness is increased to improve imaging performance, then the potential gradient becomes more gradual, but charge transfer efficiency decreases due to potential dips
Solution Approach 1:
The solution addresses the gradual potential gradient in the thickness direction by introducing multiple trench gates at different depths (vertical dimension) rather than simply increasing the overall thickness. This multi-depth approach creates localized potential wells that can effectively guide charge transfer even through thicker semiconductor layers, maintaining transfer efficiency while enabling improved imaging performance through increased thickness.
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 enables efficient and reliable transfer of electric charges, improving the operation reliability and imaging performance of the solid-state imaging device, even with increased semiconductor layer thickness and gradual potential gradients.
Implementation Method 1
a photoelectric converter that is embedded in the semiconductor layer and generates electric charges corresponding to a received light amount
Implementation Method 2
even if there is a potential dip in the photoelectric converter when the transfer section is in an off state, the potential dip is eliminated when the transfer section is in an on state
Data Source
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AI summary
An imaging device that makes it possible to smoothly transfer electric charges from a photoelectric converter to a transfer destination is provided. This imaging device includes: a semiconductor layer having a front surface and a back surface, the back surface being on an opposite side of the front surface; photoelectric converter that is embedded in the semiconductor layer and generates electric charges corresponding to a received light amount; and a transfer section that includes a first trench gate and a second trench gate and transfers the electric charges from the photoelectric converter to a single transfer destination via the first trench gate and the second trench gate, the first trench gate and the second trench gate each extending from the front surface to the back surface of the semiconductor layer into the photoelectric converter. The first trench gate has a first length from the front surface to the photoelectric converter, and the second trench gate has a second length from the front surface to the photoelectric converter, the second length being shorter than the first length.