Wrap-Around Contacts for 2D VFET Channels With Lower Contact Resistance
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Solution Overview
Problem
As transistors shrink, connecting vertical channels to metal contacts in Vertical-Transport FETs becomes a limiting factor due to the challenges of achieving reliable electrical connections, especially with the use of ultra-thin 2D materials, which are prone to quantum confinement effects and poor contact resistance.
Innovation Solution
The implementation of a vertical field-effect transistor (VFET) design featuring wrap-around female/male connections between the channel and metal contacts, where the channel forms a female portion that wraps around the metal contact, improving electrical connections and reducing contact resistance, particularly effective for channels less than 5 nm wide, using materials like transition metal dichalcogenides or carbon nanotubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metal contacts are used to connect vertical channels, then device structure is simple, but contact resistance is high and electrical connection is poor
Solution Approach 1:
The channel is configured to wrap around the metal contact, forming a nested structure where the channel surrounds the contact. This wrap-around configuration creates multiple contact interfaces between the channel and metal contact, significantly improving electrical connection and reducing contact resistance compared to conventional top-only contacts.
Solution Approach 2:
The contact structure transitions from a conventional two-dimensional top surface contact to a three-dimensional wrap-around configuration. The channel extends around the metal contact in the vertical dimension, creating additional contact areas and improving electrical connection through multi-dimensional contact geometry.
2Productivity
If channel width is reduced for scaling, then device density increases, but contact resistance increases and connection reliability deteriorates
Solution Approach 1:
The wrap-around contact structure allows ultra-thin channels (less than 5 nm) to effectively contact the metal contact from multiple directions. This nested configuration compensates for the reduced channel width by providing multiple contact pathways, maintaining low contact resistance even as device density increases through channel scaling.
Solution Approach 2:
The contact geometry parameters are changed from conventional planar contacts to three-dimensional wrap-around contacts. This parameter change in contact configuration enables effective electrical connection in ultra-thin channel devices where conventional contact geometries would result in excessively high contact resistance.
3Length of moving object
If ultra-thin 2D materials are used for channels, then device scaling is achieved, but quantum confinement effects increase and contact resistance worsens
Solution Approach 1:
The channel wraps around the metal contact in a nested configuration, ensuring that ultra-thin 2D material channels maintain effective electrical contact despite their reduced thickness. This multi-directional contact approach overcomes the challenges of quantum confinement effects by providing robust contact interfaces that are less sensitive to channel thickness variations.
Solution Approach 2:
The contact interface transitions from a single-plane contact to a three-dimensional wrap-around configuration. This dimensional change creates multiple contact points along the channel perimeter, improving electrical connection reliability for ultra-thin 2D materials where conventional planar contacts would be insufficient.
Data Source
AI summary
Embodiments herein describe FETs with channels that form wrap-around contacts (a female portion of a female/male connection) with metal contacts (a male portion of the female/male connection) in order to connect the channels to the drain and source regions. In one embodiment, a first conductive contact is formed underneath a dummy channel. In addition an encapsulation material wraps around the first conductive contact. The dummy channel and the encapsulation material can then be removed and replaced by the material of the channel which, as a result, include a female portion that wraps around the first conductive contact.