Epitaxial Source/Drain SiGe Stack for Dopant Diffusion Control
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Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, challenges arise in integrating more components into a given area, including issues with dopant diffusion and the short channel effect, which affect device performance and integration density.
Innovation Solution
The formation of epitaxial source/drain regions using a bottom layer of silicon-germanium doped with arsenic, which increases activated dopant concentration and blocks other dopants from diffusing, thereby improving device performance and integration density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If minimum feature sizes are reduced to increase integration density, then more components can be integrated into a given area, but dopant diffusion and reduced solid solubility of dopants occur affecting device performance and reliability
Solution Approach 1:
The patent changes the material composition parameter by incorporating silicon-germanium (SiGe) instead of pure silicon, and adjusts the germanium concentration parameter (e.g., 5-20% Ge) to optimize both integration density and dopant solid solubility, thereby resolving the contradiction between scaling and device performance
Solution Approach 2:
The patent uses composite silicon-germanium materials combining silicon and germanium in specific ratios to create source/drain regions with enhanced properties, where the composite structure provides both the scaling benefits and the improved dopant retention needed to maintain reliability
2Productivity
If minimum feature sizes are reduced to increase integration density, then more components can be integrated into a given area, but dopant diffusion increases affecting device performance
Solution Approach 1:
The patent introduces an intermediary silicon-germanium layer between the dopant source and the channel region, where the specific Ge concentration acts as a mediator to control and reduce unwanted dopant diffusion while allowing necessary dopant incorporation for device operation
Solution Approach 2:
By changing the germanium concentration parameter in the SiGe alloy, the patent optimizes the balance between allowing sufficient dopant incorporation for functionality and preventing excessive dopant diffusion that would harm device 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 enhances the integration density of semiconductor devices by increasing the concentration of activated dopants and reducing dopant diffusion, thereby improving device performance and addressing the short channel effect.
Implementation Method 1
silicon-germanium (SiGe) doped with arsenic (As) to enhance dopant concentration and block diffusion
Implementation Method 2
block diffusion
Implementation Method 3
multi-layer epitaxial structure to improve solid solubility and control stress
Data Source
AI summary
A device includes a fin extending from a substrate, a gate stack over and along sidewalls of the fin, a gate spacer along a sidewall of the gate stack, and an epitaxial source/drain region in the fin and adjacent the gate spacer. The epitaxial source/drain region includes a first epitaxial layer on the fin, the first epitaxial layer including silicon, germanium, and arsenic, and a second epitaxial layer on the first epitaxial layer, the second epitaxial layer including silicon and phosphorus, the first epitaxial layer separating the second epitaxial layer from the fin. The epitaxial source/drain region further includes a third epitaxial layer on the second epitaxial layer, the third epitaxial layer including silicon, germanium, and phosphorus.