Nanosheet Source-Drain Strain via Conductive Passivation
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Solution Overview
Problem
Existing nanosheet and nanowire devices suffer from source and drain electrodes that are not significantly strained in the transport direction, leading to poor performance due to the lack of constraint in their growth, resulting in epitaxial regrowth from multiple surfaces without alignment with the substrate.
Innovation Solution
The method involves deep etching to form electrode recesses, using conductive passivation layers to inhibit growth from channel and sacrificial layers, and epitaxially growing source and drain electrodes from the substrate, ensuring a substantial volume fraction is strained by registration with the substrate, with conductive passivation layers made of materials like RuO2 or oxygen-deficient TiO2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If source and drain electrodes are epitaxially regrown from multiple surfaces (channel layers, sacrificial layers, substrate), then the fabrication process is simpler, but the electrodes lack strain in the transport direction which negatively affects device performance
Solution Approach 1:
A conductive passivation layer is introduced as an intermediary between the channel layer and the source/drain electrode. This layer selectively inhibits epitaxial regrowth from the channel layer while permitting growth from the substrate, thereby enabling electrode strain without significantly complicating the fabrication process
Solution Approach 2:
The conductive passivation layer is applied locally only in regions where channel layer growth inhibition is needed, while leaving substrate exposure unchanged. This localized modification achieves the desired electrode strain effect without globally altering the fabrication process
2Reliability
If conductive passivation layers are formed to inhibit growth from channel layers, then electrode strain in transport direction is improved, but the device complexity increases
Solution Approach 1:
The conductive passivation layer serves multiple functions simultaneously: it acts as a growth inhibition barrier, provides electrical conductivity for electrode formation, and enables strain transfer from substrate to electrode. This multi-functionality reduces the need for additional separate process steps
Solution Approach 2:
The conductive passivation layer's material properties (conductivity, thickness, composition) are optimized to achieve the desired balance between growth inhibition and electrical functionality, allowing a single layer to fulfill multiple roles rather than requiring separate components
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 performance of nanosheet and nanowire devices by ensuring that a large fraction of the source and drain electrodes are strained in the transport direction, improving device performance compared to unstrained electrodes in related art devices.
Implementation Method 1
The source and drain electrodes are grown from the substrate and the conductive passivation layers substantially inhibit the source and drain electrodes from being grown from the channel layers
Implementation Method 2
epitaxially growing the source and drain electrodes in the electrode recesses
Data Source
AI summary
A method of manufacturing a nanosheet or nanowire device from a stack including an alternating arrangement of sacrificial layers and channel layers on a substrate. The method includes deep etching portions of the stack to form electrode recesses for a source electrode and a drain electrode, forming conductive passivation layers in the electrode recesses, and epitaxially growing the source and drain electrodes in the electrode recesses. Each conductive passivation layer extends at least partially along a side of one of the electrode recesses. Portions of the substrate at lower ends of the electrode recesses are uncovered by the conductive passivation layers. The source and drain electrodes are grown from the substrate and the conductive passivation layers substantially inhibit the source and drain electrodes from being grown from the channel layers.