Tensile-Strained Group IV Nanostructures Using Sb/Bi Source-Drain Epitaxy
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Solution Overview
Problem
Existing semiconductor monocrystalline nanostructures, such as nanowires and nanosheets, face challenges in enhancing charge mobility to compete with FinFETs and planar FETs, particularly in introducing adequate strain through epitaxially grown source and drain structures.
Innovation Solution
The method involves growing epitaxial source and drain structures made of a group IV semiconductor doped with Sb and Bi, and optionally As and P, on the extremities of semiconductor monocrystalline nanostructures, thereby creating tensile strain in the nanostructures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniaxial strain is introduced through lattice mismatch between Ge source/drain and SiGe strain-relaxed-buffer, then charge mobility is enhanced, but the growth process becomes complex and incompatible with emerging CFET architectures
Solution Approach 1:
The patent changes the doping parameters of the source/drain structures by incorporating Sb and Bi dopants in specific concentrations. This modifies the lattice constant of the source/drain material, creating tensile strain in the channel without requiring complex SiGe buffer structures. The parameter change in doping composition directly achieves strain enhancement while simplifying the overall device architecture.
Solution Approach 2:
Instead of using compressive strain from SiGe buffers grown from the substrate (bottom-up approach), the patent inverts the approach by using tensile strain from epitaxially grown source/drain structures on the channel extremities. This top-down approach with inverted strain type and growth direction enables compatibility with CFET architectures while maintaining strain-induced mobility enhancement.
2Reliability
If source and drain are grown bottom-up from substrate, then strain can be introduced, but different source/drain materials with different doping types cannot be used for superimposed nanostructures
Solution Approach 1:
The patent inverts the growth direction from bottom-up to top-down, enabling independent selection of source and drain materials. By growing source and drain structures epitaxially from the channel extremities, the invention allows different group IV semiconductor materials with different doping types to be used for superimposed nanostructures, achieving both strain introduction and material versatility.
Solution Approach 2:
The patent applies different doping compositions locally to source and drain structures. Each extremity can have independently optimized doping concentrations and material compositions tailored to specific device requirements, enabling different source/drain materials with different doping types for different superimposed nanostructures while maintaining strain in the channel.
3Adaptability or versatility
If epitaxial source and drain structures are grown from channel extremities, then material versatility is improved, but it is unclear if adequate strain can be introduced
Solution Approach 1:
The patent systematically varies the doping parameters (Sb and Bi concentrations) in the epitaxial source/drain structures to optimize strain introduction. By changing the dopant composition and concentration, the lattice constant of the source/drain material is adjusted to create the desired tensile strain in the channel, proving that adequate strain can indeed be introduced through epitaxial growth from extremities.
Solution Approach 2:
The patent uses composite doping strategies combining multiple dopants (Sb, Bi, and optionally As and P) in the group IV semiconductor source/drain structures. This composite approach allows fine-tuning of the material properties to achieve both material versatility and adequate strain introduction, with the combined effect of multiple dopants optimizing both versatility and strain effectiveness.
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 effectively enhances charge mobility in semiconductor monocrystalline nanostructures, improving the performance of FETs by inducing tensile strain, which is compatible with CFET technology and requires minimal adaptation to existing manufacturing practices.
Implementation Method 1
the epitaxial source and drain structures are made of a group IV semiconductor doped with one or more of Sb and Bi, and optionally one or more of As and P, thereby creating tensile strain in the group IV semiconductor monocrystalline nanostructure
Data Source
AI summary
A semiconductor structure including a semiconductor substrate having a top surface, one or more group IV semiconductor monocrystalline nanostructures, each having a first and a second extremity defining an axis parallel to the top surface of the semiconductor substrate and separated therefrom by a non-zero distance, each nanostructure having a source structure epitaxially grown on the first extremity and a drain structure epitaxially grown on the second extremity. The epitaxial source and drain structures are made of a group IV semiconductor doped with one or more of Sb and Bi, and optionally one or more of As and P, thereby creating tensile strain in the group IV semiconductor monocrystalline nanostructure.