Nanosheet Channel Surface Smoothing After Gate Replacement
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Solution Overview
Problem
The etching process in semiconductor manufacturing leaves behind residue and creates a rough texture on the channel surfaces of nano-FETs, which negatively impacts performance by affecting channel mobility, interface state density, and threshold voltage fluctuation.
Innovation Solution
A process involving oxidation and subsequent etching is used to remove residue and smooth the channel surfaces, improving the interface between the gate work function layers and the nanostructures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If etching process is used to form nanosheet channels, then channel structure is created, but residue and rough texture remain on channel surfaces
Solution Approach 1:
A sacrificial nanosheet layer is deposited and patterned in advance to define the channel regions. This preliminary structuring allows subsequent selective removal of sacrificial material to release the nanosheet channels, ensuring precise channel formation before the actual channel-defining etch process.
Solution Approach 2:
A sacrificial nanosheet material layer is introduced as an intermediary component. This sacrificial material is selectively removed to release the nanosheet channels, acting as a mediator that enables channel formation while protecting the final channel structure from direct etching damage, thereby reducing residue and surface roughness.
2Productivity
If minimum feature size is reduced to improve integration density, then more components can be integrated, but etching residue and surface roughness worsen
Solution Approach 1:
The sacrificial nanosheet layer is deposited and patterned beforehand to precisely define channel locations at scaled dimensions. This advance preparation enables accurate channel formation even as feature sizes are reduced, maintaining surface quality despite smaller dimensions and higher integration density requirements.
Solution Approach 2:
The mechanical etching process is replaced by a chemical release mechanism. Instead of directly etching the channel structure, the sacrificial material is selectively removed through chemical means, allowing precise channel release at reduced feature sizes without the mechanical damage and residue associated with traditional etching.
3Reliability
If channel surface is smoothed to improve performance, then channel mobility increases, but additional processing steps are required
Solution Approach 1:
The sacrificial nanosheet layer is deposited with controlled thickness and composition in advance, creating a template that defines the final channel geometry. This preliminary structuring ensures that when the sacrificial material is removed, the channel surfaces are already smooth and ready for operation, eliminating the need for separate smoothing steps.
Solution Approach 2:
The sacrificial nanosheet material structure serves dual purposes: it defines the channel geometry during fabrication and, when removed, leaves behind smooth channel surfaces. The structure essentially services its own removal function, where the same sacrificial material that defines the channel also protects the channel surface quality, reducing the need for additional processing 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
The process effectively removes residue and smooths the channel surfaces, enhancing the performance of nano-FETs by improving channel mobility and reducing threshold voltage fluctuations.
Implementation Method 1
A process involving oxidation and subsequent etching is used to remove residue and smooth the channel surfaces
Implementation Method 2
A process involving oxidation and subsequent etching is used to remove residue and smooth the channel surfaces
Data Source
AI summary
Embodiments include a nanoFET device and method for forming the same, the nanoFET having channel regions which have been thinned during a gate replacement process to remove etching residue. In some embodiments, the channel regions become dog bone shaped. In some embodiments, the ends of the channel regions have vertical protrusions or horns resulting from a previous trimming process which is performed prior to depositing sidewall spacers.