Epitaxial Source/Drain Layering for Lower Nanostructure Resistance
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Solution Overview
Problem
As semiconductor devices continue to shrink in size, the integration density of electronic components increases, but this miniaturization leads to challenges such as increased resistance in source/drain regions, which affects device performance.
Innovation Solution
Epitaxial source/drain regions are formed using seed layers and liner layers with specific growth rates to reduce resistance, allowing for increased volume and improved performance by growing these layers from the nanostructures rather than the substrate, thereby reducing out-diffusion of dopants and enhancing device efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If minimum feature size is reduced to increase integration density, then more components can be integrated into a given area, but resistance in source/drain regions increases and device performance deteriorates
Solution Approach 1:
The patent applies local quality by creating distinct regions with different doping concentrations within the source/drain structure. Specifically, it forms lightly-doped extension regions adjacent to the channel and heavily-doped main source/drain regions, allowing each region to optimize for its specific function: the extension regions reduce junction leakage while the main regions provide low resistance contacts, thus resolving the contradiction between miniaturization and performance
Solution Approach 2:
The source/drain structure is segmented into multiple functional regions including extension regions, main source/drain regions, and silicide contact regions. This segmentation allows each portion to be independently optimized for its specific role, enabling the overall structure to achieve both low resistance and high integration density by distributing different functions across separated zones
2Reliability
If source/drain regions are highly doped to reduce resistance, then conductivity improves, but dopant diffusion into channel regions increases and affects device performance
Solution Approach 1:
The patent introduces lightly-doped extension regions as intermediary zones between the heavily-doped main source/drain regions and the channel. These extension regions act as buffers that reduce the doping concentration gradient, thereby suppressing dopant diffusion into the channel while still providing adequate conductivity through the combined source/drain structure
Solution Approach 2:
Different doping concentrations are applied locally to different regions: heavily-doped main source/drain regions for low resistance, lightly-doped extension regions for diffusion suppression, and undoped or lightly-doped channel regions for performance optimization. This local differentiation resolves the contradiction by allowing high doping where needed while preventing harmful diffusion where it would damage performance
3Ease of manufacture
If epitaxial growth is performed from substrate to form source/drain regions, then material deposition is straightforward, but the volume available for highly-doped layers is limited and resistance remains high
Solution Approach 1:
Instead of growing the source/drain regions from the substrate upward through the entire thickness, the patent inverts the approach by forming the source/drain regions epitaxially from the top surface downward, or by growing thin highly-doped layers on pre-formed source/drain structures. This inversion allows much thinner, highly-doped layers to be created with sufficient volume for low resistance while maintaining ease of manufacture through standard epitaxial processes
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 approach decreases the resistance of epitaxial source/drain regions, improving device performance by increasing the volume available for highly-doped epitaxial layers and reducing dopant diffusion into channel regions.
Implementation Method 1
Epitaxial source/drain regions are formed using seed layers and liner layers with specific growth rates to reduce resistance
Implementation Method 2
reducing out-diffusion of dopants and enhancing device efficiency
Data Source
AI summary
In an embodiment, a device includes: a nanostructure; and a source/drain region adjoining a channel region of the nanostructure, the source/drain region including: a first epitaxial layer on a sidewall of the nanostructure, the first epitaxial layer including a germanium-free semiconductor material and a p-type dopant; a second epitaxial layer on the first epitaxial layer, the second epitaxial layer including a germanium-containing semiconductor material and the p-type dopant; and a third epitaxial layer on the second epitaxial layer, the third epitaxial layer including the germanium-containing semiconductor material and the p-type dopant.