Stepped Gate Thin-Film Transistor for Leakage Field Control
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Solution Overview
Problem
The shrinking critical sizes of process technologies in thin film transistors lead to a vertical electric field that affects carriers in semiconductor layers, causing performance deterioration due to leakage issues.
Innovation Solution
A thin film transistor design featuring a gate with a stepped structure, including a first portion in contact with the gate insulating layer, a second portion separated by a vacuum gap, and a third portion connecting these, which reduces the vertical electric field and mitigates leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the gate is positioned close to the semiconductor layer to reduce device size, then the device dimensions are reduced, but the vertical electric field increases causing leakage current
Solution Approach 1:
The gate structure is divided into three distinct portions: a first portion extending along the gate insulating layer surface, a second portion elevated above the gate insulating layer, and a third portion connecting them. This segmentation creates different spatial relationships with the semiconductor layer, allowing the first portion to maintain close proximity for small device dimensions while the elevated second portion reduces the vertical electric field and leakage current.
Solution Approach 2:
The gate structure transitions from a conventional planar configuration to a three-dimensional stepped structure. The second portion is elevated in the vertical dimension above the gate insulating layer, creating a vacuum gap that reduces the vertical electric field component. This dimensional change allows the gate to simultaneously achieve small footprint and reduced leakage.
2Ease of manufacture
If the gate structure is simplified to a single layer, then the manufacturing process is easier, but the ability to control vertical electric field is reduced
Solution Approach 1:
The gate is segmented into three portions with different vertical positions relative to the gate insulating layer. The first portion contacts the gate insulating layer surface, the second portion is elevated above it, and the third portion connects them. This segmentation provides different control zones for the electric field while maintaining a relatively simple fabrication process using standard thin film deposition and patterning techniques.
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
The design effectively reduces the vertical electric field, thereby improving the leakage current problem in thin film transistors, enhancing their overall performance.
Implementation Method 1
a vacuum gap is between the second portion of the gate and the gate insulating layer
Data Source
AI summary
A thin film transistor includes a substrate, a semiconductor layer, a gate insulating layer, a gate, a source and a drain. The semiconductor layer is located above the substrate. The gate insulating layer is located above the semiconductor layer. The gate is located above the gate insulating layer and overlapping with the semiconductor layer. The gate includes a first portion, a second portion and a third portion. The first portion is extending along the surface of the gate insulating layer and directly in contact with the gate insulating layer. The second portion is separated from the gate insulating layer. Taking the surface of the gate insulating layer as a reference, the top surface of the second portion is higher than the top surface of the first portion. The third portion connects the first portion to the second portion. The source and the drain are electrically connected to the semiconductor layer.