Carbon Nanotube Thin Film Transistor Threshold Voltage Control
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Solution Overview
Problem
Carbon nanotubes-based thin film transistors face significant challenges in controlling threshold voltage, with existing methods failing to achieve a controllable level of voltage adjustment due to considerable variation and unpredictable results from methods like gate electrode work function improvements, doping, and gate oxide layer adjustments.
Innovation Solution
A method is developed to select a nano-structure material with a monotonic relationship between threshold voltage and channel length, determining a nominal channel length based on this relationship to achieve a consistent threshold voltage, and forming a thin film transistor with a source and drain electrode, along with passivation layers to enhance electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods (gate electrode work function improvement, doping, gate oxide layer adjustment) are used to control threshold voltage, then threshold voltage adjustment is attempted, but the results show considerable variation and lack of controllability
Solution Approach 1:
The patent changes the geometric parameter (channel length) of the transistor to control the threshold voltage. By fabricating transistors with different channel lengths and establishing a monotonic relationship between channel length and threshold voltage, the invention achieves precise and reliable threshold voltage control without the variation problems of conventional methods
Solution Approach 2:
The patent performs preliminary characterization by fabricating multiple test transistors with different channel lengths, measuring their threshold voltages, and establishing the monotonic relationship before actual production. This preliminary action creates a reliable design guideline that ensures consistent threshold voltage control in subsequent manufacturing
2Reliability
If carbon nanotubes material is used as channel material, then high mobility and large current density are achieved, but threshold voltage control becomes difficult due to material variability
Solution Approach 1:
The patent shifts from controlling threshold voltage through material composition changes to controlling it through geometric parameter changes (channel length). This approach works effectively with carbon nanotubes material, maintaining the material's excellent electrical properties while achieving precise threshold voltage control through dimensional design
Solution Approach 2:
The patent replaces the chemical/material-based control methods (doping, work function adjustment) with a geometric/structural control method (channel length design). This substitution eliminates the material variability issues while preserving the high performance benefits of carbon nanotubes
Data Source
AI summary
The present application provides a method of fabricating a thin film transistor. The method includes selecting a nano-structure material having a monotonic relationship between a threshold voltage and a channel length when the nano-structure material is formed as a channel part in a thin film transistor; forming an active layer using the nano-structure material; determining a nominal channel length of a channel part of the thin film transistor based on the monotonic relationship and a reference threshold voltage so that the thin film transistor is formed to have a nominal threshold voltage; and forming a source electrode and a drain electrode thereby forming the channel part in the active layer having the nominal channel length.