TMD Monolayer Contacts for Fermi Level Tuning
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Solution Overview
Problem
As transistor geometries continue to scale down, reducing parasitic resistance of metal contacts to semiconductor source/drain regions becomes increasingly important, as existing methods like increasing metal contact area and using materials with low Schottky barrier height are limited by Fermi level pinning and non-conformal doping concentrations.
Innovation Solution
Incorporating a transition metal dichalcogenide (TMD) monolayer at the metal-semiconductor interface, which pins the interface Fermi level, allowing for the selection of TMDs to reduce the Schottky barrier height and thereby decrease the contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal contact area is increased to reduce contact resistance, then contact resistance decreases, but device area increases and scaling is limited
Solution Approach 1:
The patent changes the material parameter at the metal-semiconductor interface by introducing a TMD monolayer with specific electronic properties. This monolayer modifies the Schottky barrier height through its unique band structure and Fermi level positioning, enabling lower contact resistance without increasing physical contact area.
Solution Approach 2:
The patent creates a composite interface structure consisting of metal contact, TMD monolayer, and semiconductor. This multi-layer composite leverages the advantageous properties of each material: the metal provides conductivity, the TMD monolayer provides Fermi level tuning and low barrier height, and the semiconductor provides the active device function.
2Reliability
If materials with low Schottky barrier height are used to reduce contact resistance, then contact resistance decreases, but Fermi level pinning limits the effectiveness
Solution Approach 1:
The TMD monolayer serves as an intermediary layer between the metal contact and semiconductor. It mediates the electronic interaction by providing a controlled interface that tunes the Schottky barrier height through its specific Fermi level position, overcoming the direct metal-semiconductor Fermi level pinning limitation.
Solution Approach 2:
The patent utilizes the ability to change the Schottky barrier height parameter by selecting different TMD materials with varying band structures and Fermi levels. This allows optimization of contact resistance for different semiconductor types and applications.
3Productivity
If transistor geometries are scaled down to improve integration density, then device size decreases, but parasitic resistance becomes more significant
Solution Approach 1:
By changing the interface material parameter (introducing TMD monolayer), the patent reduces the contact resistance parameter, which becomes increasingly important as device dimensions scale down. This allows maintaining low parasitic resistance even in highly scaled devices with smaller contact areas.
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
This approach effectively reduces the contact resistance of metal contacts to semiconductor regions, improving transistor performance by tuning the Schottky barrier height, and can be applied to various transistor architectures such as planar FETs, FinFETs, and GAAFETs.
Implementation Method 1
the presence of this 2D material at the metal-semiconductor interface pins the interface Fermi level
Data Source
AI summary
Transition metal dichalcogenide (TMD) monolayers are positioned between a contact metal and a semiconductor to pin the Fermi level at the metal-semiconductor interface. The pinned Fermi level can provide for a lower Schottky barrier height between the contact metal and semiconductor than if no TMD were present at the contact metal-semiconductor interface. The height of the Schottky barrier can be tuned through the selection of the transition metal dichalcogenide used for the monolayer. Transition metal dichalcogenides have the chemical formula MX2, where M is a transition metal and X=sulfur, selenium, or tellurium. The transition metal dichalcogenides used for metal contact-semiconductor interfaces can have M=titanium, platinum, molybdenum, tungsten, erbium, rhodium, or lanthanum. A lower Schottky barrier height can reduce contact resistance, which can improve transistor performance as the parasitic resistance of source/drain channels approach that of transistor channel as transistor geometries continued to scale.