Epitaxial Source/Drain Doping Layout for Low-Resistance GAA FETs
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Solution Overview
Problem
As semiconductor devices scale down, it becomes challenging to form epitaxial material with high dopant concentration in finFET or GAA devices without forming defects, which limits circuit speed and increases source/drain resistance, especially due to boron clusters forming in p-type epitaxial silicon-germanium lattices.
Innovation Solution
A method is provided to form epitaxial source/drain regions with a polygonal-shaped upper portion and a column-like lower portion, where the corner regions have a higher boron concentration than the epitaxial body region, allowing boron dopants to diffuse and increase the overall dopant concentration, reducing resistance and improving device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high dopant concentration is attempted in epitaxial source/drain regions, then source/drain resistance is reduced, but defects form in the epitaxial material
Solution Approach 1:
The epitaxial source/drain region is divided into two distinct zones: a first region with higher dopant concentration and a second region with lower dopant concentration. This segmentation allows the high-dopant first region to reduce source/drain resistance while the low-dopant second region maintains epitaxial material quality, preventing defect formation throughout the entire structure.
Solution Approach 2:
Different dopant concentrations are applied to different spatial locations within the epitaxial source/drain region. The first region near the contact interface receives high dopant concentration to minimize resistance, while the second region extends with lower concentration to avoid defects, creating locally optimized properties throughout the structure.
2Productivity
If device geometry is scaled down, then integration density and production efficiency are improved, but resistance increases
Solution Approach 1:
The dopant concentration parameter is strategically varied within the epitaxial source/drain region to compensate for resistance increases due to scaling. By implementing a gradient from high to low concentration, the structure maintains low resistance despite reduced dimensions, enabling continued scaling while preserving electrical performance.
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 reduces source/drain resistance, metal contact resistance, and epitaxial layer loss, enhancing device performance, reliability, and yield, and can be applied to various technology nodes and semiconductor structures like finFETs, GAAFETs, and planar FETs.
Implementation Method 1
the corner regions are characterized by a first dopant concentration and the epitaxial body region is characterized by a second dopant concentration, and the first dopant concentration is higher than the second dopant concentration
Data Source
AI summary
A semiconductor device includes a plurality of nanostructures, a gate dielectric layer disposed on each nanostructure of the plurality of nanostructures, a gate electrode disposed on the gate dielectric layer and on the plurality of nanostructures, and a source/drain region adjacent to the nanostructures. The source/drain region includes an epitaxial structure including a polygonal-shaped upper portion and a column-like lower portion, wherein the polygonal-shaped upper portion has multiple facets, and each of the facets characterized by a (111) crystallographic orientation. The polygonal-shaped upper portion includes corner regions adjacent an intersection of two facets with a (111) crystallographic orientation and an epitaxial body region in contact with the corner regions. The corner regions are characterized by a first dopant concentration and the epitaxial body region is characterized by a second dopant concentration, and the first dopant concentration is higher than the second dopant concentration.