Imaging Device Transistor Gate Protection Against Leakage
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Solution Overview
Problem
Stacked image sensors face degradation due to leakage current from the charge storage region, particularly under high illuminance conditions, which can damage transistors and affect image quality.
Innovation Solution
The imaging device incorporates a semiconductor layer with an impurity region of a first conductivity type, a photoelectric converter, and transistors with gates of a second conductivity type different from the impurity region, which helps reduce depletion layers under the gate electrodes, thereby minimizing dark current and image degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection transistor is added to inhibit electric potential rise in high illuminance conditions, then transistor damage is prevented, but device complexity increases
Solution Approach 1:
The protection function is merged into the existing pixel circuit by making the reset transistor's gate electrode serve dual purposes: normal reset operation and protection against high illuminance damage. The gate electrode is configured to be electrically connected to the charge storage region, allowing it to automatically limit voltage rise without requiring a separate protection transistor.
Solution Approach 2:
The gate electrode of the reset transistor is designed to perform multiple functions: it controls the reset operation during normal imaging and simultaneously acts as a protection mechanism against high illuminance damage by limiting the electric potential rise in the charge storage region.
2Object-generated harmful factors
If the gate electrode is electrically connected to the charge storage region, then dark current is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The electrical connection between the gate electrode and charge storage region is achieved by merging their physical structures. The gate electrode is formed to directly overlap with and electrically connect to the charge storage region through the gate insulating layer, eliminating the need for separate connection structures and reducing manufacturing precision requirements.
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 effectively reduces dark current and enhances image quality by minimizing depletion layers and stabilizing transistor operation, even under high illuminance conditions.
Implementation Method 1
a photoelectric converter electrically connected to the impurity region
Data Source
AI summary
An imaging device includes a semiconductor layer including an impurity region of a first conductivity type, a photoelectric converter electrically connected to the impurity region, and a transistor having a gate of a second conductivity type different from the first conductivity type, a source and a drain, the transistor including the impurity region as one of the source and the drain, the gate being electrically connected to the impurity region.