Wetting Layer for N-Type CNT FET Drive Current and Yield
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Solution Overview
Problem
Conventional methods for enhancing drive current and device yield in n-type carbon nanotube field effect transistors (CNT FETs) face challenges, particularly with scaled contacts, as they result in reduced performance and increased complexity, limiting the integration of CNT FETs into CMOS architecture and reducing device yield.
Innovation Solution
The implementation of a wetting layer between the carbon nanotube and a low work function metal contact, such as titanium, improves physical and electrical contact, leading to increased drive current and device yield by facilitating efficient charge carrier injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional methods are used to form contacts in n-type CNT FETs, then device fabrication can proceed with standard processes, but drive current is reduced and device yield decreases
Solution Approach 1:
A wetting layer of titanium is introduced as an intermediary between the low work function metal (scandium) and the carbon nanotube. This wetting layer improves the physical and electrical contact at the interface, enabling efficient charge carrier injection while maintaining n-type behavior. The wetting layer acts as a mediator that resolves the contradiction between using simple contact structures and achieving high drive current.
2Adaptability or versatility
If scaled contacts are used in n-type CNT FETs, then device integration can be improved, but drive current and device yield are reduced
Solution Approach 1:
The wetting layer enables scaled contacts to maintain reliable electrical connection with the carbon nanotube despite reduced contact dimensions. By improving the interfacial contact quality, the wetting layer ensures that scaled contacts do not compromise device yield or reliability, thus resolving the contradiction between device integration and device yield.
3Productivity
If a wetting layer is added between the low work function metal and carbon nanotube, then drive current and device yield increase, but fabrication complexity increases
Solution Approach 1:
The wetting layer is formed by controlling deposition parameters (thickness, material composition) to optimize the contact interface. By carefully adjusting these parameters, the wetting layer provides significant improvements in drive current and device yield while minimizing the increase in fabrication complexity. The thinness and specific material properties of the wetting layer allow it to be integrated into existing fabrication processes with minimal additional complexity.
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 use of a wetting layer enhances drive current and device yield by improving the carbon nanotube/electrode interface, achieving higher average drive currents and operational device counts, as demonstrated by the increase from 0.46 μA to 0.77 μA and improving device yield from 81 to 226 operational devices.
Implementation Method 1
A wetting layer is formed between the low work function metal and the nanotube
Data Source
AI summary
Embodiments of the invention are directed to methods and resulting structures for enhancing drive current and increasing device yield in n-type carbon nanotube field effect transistors (CNT FETs) with scaled contacts using a wetting layer. In some embodiments of the invention, a nanotube is formed over a surface of a substrate. An insulating layer is formed over the nanotube such that end portions of the nanotube are exposed. A low work function metal is formed over the end portions of the nanotube and a wetting layer is formed between the low work function metal and the nanotube.