FinFET Junction Formation via Thermal Condensation
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Solution Overview
Problem
In FinFET structures, improving pFinFET performance often degrades nFinFET performance due to the use of different materials for fins, and there is a need for independently tunable channel and source/drain regions with distinct material properties to enhance overall device performance.
Innovation Solution
A method involving a silicon germanium fin with an epitaxial layer and a spacer, where thermal condensation increases the germanium concentration in the channel region, forming a germanium-enriched channel with a higher germanium concentration than the source/drain region, and a replacement metal gate is deposited after removing the dummy gate and oxidized channel region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different materials are used for fins of pFinFETs and nFinFETs to improve device performance, then performance of one type is improved, but performance of the other type is degraded
Solution Approach 1:
The patent applies local quality by creating distinct material compositions in different regions of the fin structure. The channel region contains silicon-germanium with higher germanium concentration (e.g., 30-70% Ge) optimized for carrier mobility, while the source/drain regions contain silicon-germanium with lower germanium concentration (e.g., 0-20% Ge) optimized for doping and contact properties. This spatial variation in material composition allows each region to be optimized for its specific function while maintaining overall device performance.
Solution Approach 2:
The fin structure is segmented into functionally distinct regions with different material properties. The channel region and source/drain regions are separated and given different silicon-germanium compositions through selective epitaxial growth and thermal condensation processes. This segmentation enables independent optimization of each region's material characteristics without compromising the other type of FinFET device on the same substrate.
2Quantity of substance
If thermal condensation is performed to increase germanium concentration in the channel region, then germanium enrichment is achieved, but oxidation of the fin surface occurs requiring additional processing steps
Solution Approach 1:
The patent employs preliminary action by performing thermal condensation in an oxidizing atmosphere that simultaneously achieves germanium enrichment in the channel region and forms a protective silicon oxide layer on the fin surface. This preliminary oxidation step prepares the surface for subsequent epitaxial growth of source/drain regions, combining material enrichment and surface preparation in one process step, thereby reducing overall process complexity.
Solution Approach 2:
The patent converts the harmful effect of oxidation during thermal condensation into a beneficial outcome. The silicon oxide formed on the fin surface during germanium enrichment is not removed but instead serves as a protective layer and template for subsequent epitaxial source/drain growth. This approach transforms what would traditionally be a harmful byproduct into a useful intermediate structure, eliminating the need for additional cleaning or preparation steps.
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 allows for independently tuning the channel and source/drain regions, improving device performance by enhancing the germanium concentration in the channel region, resulting in an abrupt junction and improved overall FinFET structure performance.
Implementation Method 1
A thermal condensation is performed on an exterior portion of the silicon germanium fin in the channel region. The thermal condensation forms a silicon oxide layer on the exterior portion of the silicon germanium fin in the channel region and an enriched germanium fin on an interior portion of the silicon germanium fin in the channel region.
Data Source
AI summary
A finFET structure, and method of forming such structure, in which a germanium enriched nanowire is located in the channel region of the FET, while simultaneously having silicon-germanium fin in the source/drain region of the finFET.