FinFET Source/Drain SiGe Structure for Lower Leakage Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, they face challenges such as increased leakage current due to dopant diffusion, which degrades device performance, and reduced integration density, necessitating improved methods for forming epitaxial source/drain regions in FinFETs.
Innovation Solution
The formation of epitaxial source/drain regions with a bottom layer of silicon germanium doped with boron, which reduces dopant diffusion and allows for a deeper recess, increasing the volume of these regions and enhancing the turn-on current of FinFETs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature size is reduced to increase integration density, then more components can be integrated into a given area, but leakage current increases due to dopant diffusion
Solution Approach 1:
A silicon germanium layer is introduced as an intermediary material between the source/drain regions and the channel. This intermediate layer acts as a diffusion barrier that prevents dopant migration while allowing the device to maintain scaled dimensions, thereby resolving the contradiction between high integration density and low leakage current
Solution Approach 2:
The patent uses composite material structure combining silicon and germanium in specific ratios to create source/drain regions with tailored properties. The silicon germanium alloy provides both the mechanical integrity needed for scaled devices and the chemical properties to suppress dopant diffusion, enabling simultaneous achievement of high integration density and low leakage
2Reliability
If epitaxial source/drain regions are formed to reduce dopant diffusion, then leakage current is reduced, but the volume of source/drain regions is limited
Solution Approach 1:
The patent applies local quality by forming silicon germanium layers with varying compositions at different locations within the source/drain structure. The bottom portion has higher germanium content for diffusion blocking, while upper portions have lower germanium content to maintain electrical conductivity and increase effective volume, thus resolving the contradiction between leakage reduction and volume enhancement
Solution Approach 2:
The patent extends the source/drain structure into the substrate vertically, creating a three-dimensional configuration. By utilizing the vertical dimension through deeper recesses and multi-layer epitaxial growth, the effective volume of source/drain regions is increased without compromising the lateral scaling needed for high integration density
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 leakage current by up to 15% and increases the turn-on current by up to 10% by blocking dopant diffusion and increasing the volume of the epitaxial source/drain regions, thereby improving the electrical performance of FinFETs.
Implementation Method 1
increased leakage current due to dopant diffusion
Implementation Method 2
epitaxially growing a first semiconductor material on sidewalls of the recess
Data Source
AI summary
A method includes forming a semiconductor fin over a substrate, etching the semiconductor fin to form a recess, wherein the recess extends into the substrate, and forming a source/drain region in the recess, wherein forming the source/drain region includes epitaxially growing a first semiconductor material on sidewalls of the recess, wherein the first semiconductor material includes silicon germanium, wherein the first semiconductor material has a first germanium concentration from 10 to 40 atomic percent, epitaxially growing a second semiconductor material over the first semiconductor material, the second semiconductor material including silicon germanium, wherein the second semiconductor material has a second germanium concentration that is greater than the first germanium concentration, and epitaxially growing a third semiconductor material over the second semiconductor material, the third semiconductor material including silicon germanium, wherein the third semiconductor material has a third germanium concentration that is smaller than the second germanium concentration.