2D Semiconductor Epitaxy for Low-Defect Short-Channel Transistors
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Solution Overview
Problem
The challenge of further increasing transistor density is hindered by the short channel effect, which is exacerbated by the reduction in channel length, and existing methods struggle to form single-crystalline layers over two-dimensional (2D) semiconductor materials, leading to increased off-state current and defects.
Innovation Solution
The formation of single-crystalline layers, such as 2D dielectric, metal, and semiconductor layers, is achieved through epitaxial growth on lattice-matched 2D materials, utilizing techniques like ALD and sputtering at lower temperatures to reduce strain and defects, thereby improving the integration of transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If channel length is reduced to increase transistor density, then integration density is improved, but short channel effect is exacerbated leading to increased off-state current
Solution Approach 1:
The patent changes the material parameter from conventional silicon to two-dimensional semiconductor materials (such as MoS2, WS2, WSe2, MoSe2, black phosphorus, or germanene) with atomic-layer thickness. This material substitution fundamentally alters the electrical characteristics, enabling ultra-thin channel structures that suppress short channel effects while maintaining high transistor density through continued miniaturization
2Ease of manufacture
If conventional deposition methods are used to form layers over 2D semiconductor materials, then manufacturing process is simplified, but single-crystalline layer formation is difficult leading to increased defects
Solution Approach 1:
The patent employs an intermediary approach by first forming a buffer layer or seed layer on the substrate, then epitaxially growing the single-crystalline 2D semiconductor material on top of this intermediary layer. This two-step process mediates between the substrate and the final 2D material, enabling high-quality single-crystalline formation while maintaining practical manufacturability through established epitaxial techniques
Solution Approach 2:
The patent utilizes epitaxial growth processes that involve phase transitions from vapor or liquid precursor phases to solid crystalline 2D semiconductor layers. By controlling the phase transition conditions (temperature, pressure, gas flow), the method achieves single-crystalline material formation with minimal defects, resolving the contradiction between process simplicity and manufacturing precision
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 transistor performance by reducing defect density and improving the interface quality between layers, leading to better mobility and reliability of semiconductor devices.
Implementation Method 1
forming a single-crystalline two-dimensional (2D) semiconductor layer over a substrate
Implementation Method 2
epitaxially growing a single-crystalline 2D material layer on the single-crystalline 2D semiconductor layer
Data Source
AI summary
A method includes following steps. A single-crystalline two-dimensional (2D) semiconductor layer is formed over a substrate. A single-crystalline 2D material layer is epitaxially grown on the single-crystalline 2D semiconductor layer. The single-crystalline 2D material layer is lattice-matched with the single-crystalline 2D semiconductor layer. A semiconductor device is over the single-crystalline 2D semiconductor layer.