Oxidized TMD Monolayer Stack for Gate Dielectric Growth
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Solution Overview
Problem
Integrating transition metal dichalcogenide (TMD) materials with gate dielectric materials is challenging due to the lack of dangling bonds that facilitate nucleation, hindering the scaling of transistors below 5 nm.
Innovation Solution
A TMD layer stack is formed with chemically altered uppermost and lowermost monolayers to provide nucleation sites for gate dielectric layer growth, maintaining the integrity of the sandwiched monolayers and enabling a three-dimensional structure for improved mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TMD materials are used as channel layers to improve mobility and enable transistor scaling, then device performance is improved, but integration with gate dielectric materials becomes challenging due to lack of dangling bonds for nucleation
Solution Approach 1:
The patent applies preliminary action by chemically altering the TMD surface before gate dielectric deposition. The outermost monolayer is oxidized or functionalized to create dangling bonds and nucleation sites, preparing the surface in advance for successful gate dielectric growth. This pre-treatment resolves the nucleation problem without affecting the underlying TMD channel properties.
Solution Approach 2:
The patent applies local quality by modifying only the outermost monolayer of the TMD structure while preserving the bulk TMD properties. The chemical alteration is localized to the surface region, creating nucleation sites specifically where needed for gate dielectric attachment, while the inner monolayers maintain their original high-mobility characteristics.
2Reliability
If outermost monolayers are chemically altered to provide nucleation sites, then gate dielectric adhesion is improved, but TMD layer integrity may be compromised
Solution Approach 1:
The patent applies segmentation by dividing the TMD structure into distinct functional regions: the outermost monolayer serves as a sacrificial nucleation layer that is chemically altered, while the inner monolayers are preserved as the functional channel. This segmentation allows the surface to be modified for adhesion without compromising the bulk TMD integrity.
Solution Approach 2:
The patent applies the intermediary principle by using the outermost monolayer as a mediator between the gate dielectric and the bulk TMD channel. This intermediate layer provides the necessary chemical functionality for nucleation while protecting the underlying TMD structure from direct exposure to harsh chemical treatments.
3Productivity
If transistor size is scaled down to increase device density, then chip functionality is improved, but mobility and subthreshold slope become adversely affected at dimensions less than 5 nm
Solution Approach 1:
The patent applies parameter changes by transitioning from traditional silicon channel materials to TMD materials with different physical and chemical parameters. TMDs offer superior mobility and electrostatic control at nanoscale dimensions, allowing transistors to scale below 5 nm while maintaining or improving performance parameters that deteriorate in silicon-based devices.
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 solution facilitates defect-free adhesion of the gate dielectric layer, reducing gate current leakage and enhancing mobility, while allowing for feature scaling in transistors to dimensions less than 10 nm.
Implementation Method 1
The articles refer to transition metal dichalcogenides (TMDs) as one family of layered materials with electronic properties that are particularly interesting for semiconductor devices
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 1E
AI summary
A transistor includes two stacked channel channels (204, 206), each including a first layer (104) including a first monolayer of a monocrystalline transition metal dichalcogenide, TMD, material, where the first layer is stoichiometric and includes a first transition metal. The channel further includes a second layer (404A, 404B) above the first layer, the second layer including a second monolayer of a monocrystalline TMD material, where the second monocrystalline TMD material includes a second transition metal and oxygen (417), and where the second layer is sub-stoichiometric. The transistor further includes a gate electrode above a first portion of the channel layer, a gate dielectric layer (418) between the channel layer and the gate electrode, a source contact on a second portion of the channel layer and a drain contact on a third portion of the channel layer, where the gate electrode is between drain contact and the source contact. The sub-stoichiometric second monocrystalline TMD monolayer improves the growth of the gate dielectric on the stoichiometric TMD layer.