Dual Trench Gate Layout for Smooth Charge Transfer in Image Sensors
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Solution Overview
Problem
In solid-state imaging devices, there is a challenge in smoothly transferring electric charges from the photoelectric converter to the transfer destination, particularly due to potential dips that can occur in the photoelectric converter.
Innovation Solution
The imaging device incorporates a transfer section with a first trench gate and a second trench gate, both extending from the front surface to the back surface of the semiconductor layer into the photoelectric converter. The first trench gate has a longer length than the second trench gate, which helps in eliminating potential dips and ensuring smooth charge transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single trench gate is used for charge transfer, then the device complexity is reduced, but potential dips occur in the photoelectric converter causing poor charge transfer reliability
Solution Approach 1:
The transfer section is divided into multiple trench gates (first trench gate and second trench gate) with different lengths extending into the photoelectric converter. This segmentation allows each trench gate to control charge transfer from different depth regions, eliminating potential dips and improving charge transfer reliability without requiring excessive complexity
Solution Approach 2:
Different trench gates are designed with different lengths to match the local charge distribution characteristics at different depths of the photoelectric converter. The first trench gate extends deeper to handle charges from lower regions, while the second trench gate handles charges from upper regions, creating locally optimized charge transfer paths that eliminate potential dips
2Productivity
If trench gates extend deeper into the photoelectric converter, then charge transfer efficiency improves, but manufacturing precision requirements increase
Solution Approach 1:
Instead of using a single deep trench gate that would require high manufacturing precision, the transfer section is segmented into multiple trench gates with different, shallower depths. This segmentation reduces the depth control precision requirement for each individual trench gate while maintaining effective charge transfer from all depth regions of the photoelectric converter
Solution Approach 2:
Each trench gate is designed to extend only to the depth necessary for its specific function, rather than all trench gates extending to the maximum depth. This partial action approach reduces manufacturing complexity and precision requirements while achieving complete charge transfer coverage through the combination of multiple trench gates
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 from the photoelectric converter to the transfer destination, even when potential dips are present, thereby enhancing the operation reliability and imaging performance of the solid-state imaging device.
Implementation Method 1
a photoelectric converter that is embedded in the semiconductor layer and generates electric charges corresponding to a received light amount
Data Source
AI summary
An imaging device that smoothly transfers electric charges from a photoelectric converter to a transfer destination is provided. This imaging device includes: a semiconductor layer; a photoelectric converter that 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.