SiGe Nanotube Fabrication via Ge Diffusion
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Solution Overview
Problem
Current techniques for fabricating semiconductor nanotubes, such as carbon nanotubes and silicon germanium (SiGe) nanotubes, face challenges in achieving dimensional uniformity and alignment, making it difficult to produce nanotubes with consistent properties.
Innovation Solution
A method involving the formation of alternating silicon (Si) and SiGe layers on a wafer, patterning fins, depositing an oxide material, and annealing to diffuse germanium atoms, resulting in vertically stacked SiGe nanotubes surrounding Si cores, which can be selectively processed to create hollow nanotubes with controlled dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical vapor deposition (CVD) or gas phase condensation is used to fabricate semiconductor nanotubes, then nanotubes can be formed, but dimensional uniformity and alignment are very difficult to achieve
Solution Approach 1:
The patent applies preliminary action by first forming alternating Si and SiGe layers with precisely controlled thicknesses and compositions before any nanotube formation occurs. The layers are patterned into fins with defined geometries, and oxide materials are deposited on specific surfaces prior to annealing. This pre-structured arrangement ensures that when Ge atoms diffuse during annealing, they do so along predetermined paths, guaranteeing dimensional uniformity and alignment of the resulting nanotubes.
Solution Approach 2:
The patent utilizes parameter changes by controlling the composition gradient of Ge atoms in the SiGe layers, the thickness parameters of alternating layers, and the annealing temperature and time parameters. By adjusting these parameters, the diffusion of Ge atoms along the oxide-Si/SiGe interfaces can be precisely controlled to form nanotubes with uniform dimensions and alignment, resolving the contradiction between manufacturing precision and fabrication ease.
2Manufacturing precision
If alternating Si and SiGe layers are formed with controlled composition, then nanotube composition can be controlled, but dimensional uniformity and alignment remain difficult to achieve
Solution Approach 1:
The patent applies segmentation by dividing the nanotube structure into alternating Si and SiGe layers, where each layer serves a specific function. The Si layers form the core structure while the SiGe layers provide Ge atoms for diffusion. This segmentation allows independent control of composition in each layer type, achieving both composition control and dimensional uniformity despite the inherent structural complexity.
Solution Approach 2:
The oxide material deposited on the fin surfaces acts as an intermediary that facilitates controlled Ge atom diffusion during annealing. The oxide-Si/SiGe interfaces serve as preferential diffusion pathways, mediating the movement of Ge atoms from SiGe layers to form uniform nanotube structures. This intermediary mechanism simplifies the overall process by providing a defined route for composition control and dimensional uniformity.
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 enables the fabrication of SiGe nanotubes with improved dimensional uniformity and alignment, enhancing mechanical stability and compatibility with existing semiconductor manufacturing processes, while avoiding alignment issues common in CVD-grown nanotubes.
Implementation Method 1
annealing the at least one fin under conditions sufficient to diffuse germanium (Ge) atoms from the SiGe layers along an interface between the oxide material and the Si and SiGe layers
Data Source
AI summary
Stacked SiGe nanotubes and techniques for the fabrication thereof are provided. In one aspect, a method of forming a SiGe nanotube stack includes: forming Si and SiGe layers on a wafer, one on top of another, in an alternating manner; patterning at least one fin in the Si and SiGe layers; depositing an oxide material onto the at least one fin; and annealing the at least one fin under conditions sufficient to diffuse Ge atoms from the SiGe layers along an interface between the oxide material and the Si and SiGe layers to form at least one vertical stack of SiGe nanotubes surrounding Si cores. A SiGe nanotube device and method for formation thereof are also provided.