FinFET Diffusion Blocking Layer for Short Channel Effects
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Solution Overview
Problem
The reduction in channel length of FETs leads to short channel effects, where the electrical potential of the source region is adversely affected by the drain, degrading the performance of FETs, and it is challenging to increase activated dopant levels without introducing further degradation.
Innovation Solution
A finFET device is developed with a diffusion blocking layer, comprising a first epitaxial semiconductor material with a specific dopant concentration, a silicon carbon diffusion blocking layer, and a second epitaxial semiconductor material with a higher dopant concentration, positioned above the first material to inhibit dopant diffusion and reduce short channel effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the channel length of FETs is reduced to improve operating speed and increase device density, then the switching speed improves, but short channel effects occur where the drain electrical potential adversely affects the source region and channel, degrading FET performance
Solution Approach 1:
A diffusion blocking layer comprising silicon carbon is introduced as an intermediary between the first and second epitaxial semiconductor materials. This blocking layer prevents dopant diffusion from the high-dopant second material to the low-dopant first material, thereby eliminating the harmful interaction (short channel effects) while maintaining the beneficial high doping concentration for performance improvement
Solution Approach 2:
The source/drain region is segmented into three distinct layers: a first epitaxial semiconductor material with lower dopant concentration, a diffusion blocking layer with silicon carbon, and a second epitaxial semiconductor material with higher dopant concentration. This segmentation allows each layer to perform its specific function - the first layer provides a diffusion barrier, the blocking layer prevents dopant mixing, and the second layer provides high doping for performance
2Reliability
If the dopant concentration in the source/drain region is increased to improve electrical performance, then the mobility of charge carriers improves, but short channel effects are intensified, degrading device performance
Solution Approach 1:
Different regions of the source/drain structure are assigned different dopant concentrations: the second epitaxial semiconductor material has high dopant concentration to improve electrical performance and carrier mobility, while the first epitaxial semiconductor material has lower dopant concentration to minimize short channel effects. The diffusion blocking layer ensures these local quality differences are maintained without dopant diffusion
Solution Approach 2:
The diffusion blocking layer acts as an intermediary that allows the high-dopant second material to be placed adjacent to the channel without its dopants diffusing into the channel or the first material, thereby enabling high doping concentrations to be used without intensifying short channel effects
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 diffusion blocking layer effectively reduces the chance of short channel effect degradation by isolating higher dopant levels from the channel region, thereby increasing the device's performance by decreasing contact resistance.
Implementation Method 1
A diffusion blocking layer is positioned above the first epitaxial semiconductor material. The diffusion blocking layer effectively reduces the chance of short channel effect degradation by isolating higher dopant levels from the channel region
Data Source
AI summary
One illustrative device disclosed herein includes, among other things, a fin defined on a substrate. A gate electrode structure is positioned above the fin in a channel region. A source/drain region is defined in the fin. The source/drain region includes a first epitaxial semiconductor material. The first epitaxial semiconductor material includes a dopant species having a first concentration. A diffusion blocking layer is positioned above the first epitaxial semiconductor material. A second epitaxial semiconductor material is positioned above the diffusion blocking layer. The second epitaxial semiconductor material includes the dopant species having a second concentration greater than the first concentration.