Thin Film Transistor Gate Electrode Segmentation for Parasitic Capacitance Reduction
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Solution Overview
Problem
In thin film transistors, the disposition of electrodes leads to increased parasitic capacitance due to overlapping regions, which deteriorates device performance, especially when the source and drain electrodes are on different planes from the gate electrode.
Innovation Solution
A method of forming a thin film transistor with a gate electrode having a 'dumbbell' shape, where the first part is narrower than the space between the source and drain electrodes, and the second part is wider, ensuring the electrodes are not overlapped, and surface-processing the gate electrode to form grooves that taper from the edges towards the center, reducing parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the source and drain electrodes are positioned on different planes from the gate electrode to improve electrical connection, then electrical conductivity is improved, but parasitic capacitance increases due to overlapping regions
Solution Approach 1:
The gate electrode is segmented into two distinct parts: a first part positioned between the source and drain electrodes, and a second part positioned away from them. This segmentation allows the gate electrode to fulfill multiple functions - providing electrical control over the channel while minimizing parasitic capacitance through spatial separation of its different functional regions
Solution Approach 2:
The invention utilizes vertical layering (different planes) to resolve the contradiction. The source and drain electrodes are positioned on one plane while the gate electrode is positioned on a different plane, allowing electrical connection improvement through 3D spatial arrangement while the specific configuration of the gate electrode's first and second parts controls the parasitic capacitance
2Reliability
If the gate electrode width is increased to improve gate control over the channel, then switching performance is improved, but overlapping regions with source and drain electrodes increase, leading to higher parasitic capacitance
Solution Approach 1:
By dividing the gate electrode into a first part (between source and drain) and a second part (away from source and drain), the invention allows the first part to provide necessary gate control while the second part extends the gate electrode area without increasing parasitic capacitance, since it is positioned away from the source and drain electrodes
Solution Approach 2:
Different parts of the gate electrode are given different spatial qualities - the first part is positioned close to the channel for effective control, while the second part is positioned away from the source and drain electrodes to avoid parasitic capacitance. This local differentiation of spatial positioning optimizes both switching performance and parasitic capacitance
Data Source
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AI summary
A thin film transistor includes a gate electrode on a semiconductor layer, a first insulation layer between the semiconductor layer and the gate electrode, a second insulation layer on the gate electrode, and a source and drain electrode on the semiconductor layer. The gate electrode includes a first part and a second part adjacent to the first part. A width of the second part is greater than a width of the first part. The source electrode and the drain electrode are on the semiconductor layer and arranged such that the first part of the gate electrode is between the source electrode and the drain electrode. The source electrode and the drain electrode are electrically connected to the semiconductor layer through the first insulation layer and the second insulation layer, respectively. A space between the source electrode and the drain electrode is greater than the width of the first part.