2-D TMD Contact Formation by Chalcogen Removal
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Solution Overview
Problem
The semiconductor industry faces challenges in forming reliable semiconductor devices at increasingly smaller sizes due to the complexity of fabrication processes, particularly in creating reliable contacts with 2-D material layers like transition metal dichalcogenides (TMDs), where the scaling down of feature sizes complicates the formation of effective source/drain contacts.
Innovation Solution
The method involves etching processes to remove chalcogen atoms from the 2-D material layers, allowing metal contacts to form direct metallic bonds with transition metal atoms, thereby increasing the contact area and improving current conductivity, and using specific etching techniques and chemical species to weaken and break covalent bonds between chalcogen and metal atoms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes are scaled down to increase functional density, then production efficiency and cost are improved, but fabrication process complexity and difficulty increase
Solution Approach 1:
The patent changes the chemical state of the 2-D material layer by removing chalcogen atoms through etching processes, transforming the material from a complete TMD structure to a metal-rich structure that enables direct metallic bonding with contact metals, thereby improving contact properties at scaled dimensions
Solution Approach 2:
The patent applies selective etching to specific regions of the 2-D material layer, removing chalcogen atoms primarily from areas where metal contacts will be formed, while preserving the integrity of the channel region, thus creating locally optimized contact interfaces without compromising overall device structure
2Reliability
If conventional contacts are formed on 2-D material layers, then device structure is simple, but contact resistance is high due to covalent bonding requirements
Solution Approach 1:
The patent extracts chalcogen atoms from the 2-D material layer through selective etching processes, removing the element that creates covalent bonding barriers and preventing direct metallic bonding between contact metals and transition metal atoms in the TMD layer
Solution Approach 2:
The patent uses chemical etchants as intermediaries to facilitate the removal of chalcogen atoms, employing species such as chlorine-containing, fluorine-containing, or hydrogen-containing compounds that selectively react with and remove chalcogen while leaving the transition metal lattice intact
3Reliability
If chalcogen atoms are removed from 2-D material layers, then contact area and current conductivity are increased, but manufacturing process complexity increases
Solution Approach 1:
The patent divides the etching process into multiple sequential stages with different etchants and conditions, first using one type of etchant to remove chalcogen atoms and then using another etchant to further process the structure, allowing precise control over the etching depth and selectivity
Solution Approach 2:
The patent employs periodic alternation between etching steps and deposition steps, cycling through different chemical treatments to progressively remove chalcogen atoms and restore metal atoms to their proper lattice positions, enabling controlled modification without complete structure degradation
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 enhances the contact resistance between source/drain contacts and the 2-D material layer, leading to improved transistor performance by increasing the contact area and current conductivity, especially when chalcogen atoms are removed from multiple sides of the TMD channel layer and when the work function of the contact metals exceeds that of the transition metals.
Implementation Method 1
weakener and break covalent bonds between chalcogen and metal atoms
Implementation Method 2
etching processes to remove chalcogen atoms from the 2-D material layers
Implementation Method 3
allowing metal contacts to form direct metallic bonds with transition metal atoms
Data Source
AI summary
A method includes forming a 2-D material layer over a substrate, wherein the 2-D material layer comprises transition metal atoms and chalcogen atoms; forming a gate structure over the 2-D material layer; supplying chemical molecules to the 2-D material layer, such that atoms of the chemical molecules react with portions of the chalcogen atoms to weaken covalent bonds between the portions of the chalcogen atoms and the transition metal atoms; and forming source/drain contacts over the 2-D material layer, wherein contact metal atoms of the source/drain contacts form metallic bonds with the transition metal atoms of the 2-D material layer.