Nanosheet Transistor Inner Spacer Formation for Uniform Sidewalls
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing inner spacers in semiconductor transistors are not entirely satisfactory in protecting the source/drain structure from damage during the gate replacement process, leading to critical dimension variation and surface roughness issues that affect device performance.
Innovation Solution
A pre-treatment process involving radical surface treatment and surface cleaning is applied to remove residues and improve surface roughness, followed by selective etching to form uniform critical dimensions and smoother sidewalls, ensuring the integrity of the inner spacer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional inner spacer formation is used, then the source/drain structure is protected from damage during gate replacement, but critical dimension variation and surface roughness occur affecting device performance
Solution Approach 1:
A pre-treatment process is performed on the sacrificial gate structure before forming the inner spacer. This preliminary action modifies the surface properties of the sacrificial gate, enabling more uniform spacer deposition and reducing critical dimension variation while maintaining the protective function during gate replacement
Solution Approach 2:
The invention changes the surface parameters of the sacrificial gate structure through pre-treatment (such as surface energy, roughness, or chemical composition) to optimize the subsequent inner spacer formation process. This parameter modification ensures uniform spacer thickness and reduces critical dimension variation while preserving the source/drain protection function
2Reliability
If conventional inner spacer formation is used, then the source/drain structure is protected from damage during gate replacement, but surface roughness increases affecting device performance
Solution Approach 1:
The pre-treatment process is applied to the sacrificial gate structure before inner spacer deposition. This preliminary action smooths or modifies the surface to reduce roughness that would otherwise be transferred to the inner spacer and subsequently to the source/drain structure, while maintaining the protective function
Solution Approach 2:
Surface parameters such as roughness and wettability are modified through pre-treatment to enable uniform inner spacer formation. This parameter change reduces surface roughness propagation to the source/drain structure while preserving the damage protection function during gate replacement
3Productivity
If scaling down process is used, then production efficiency increases and costs decrease, but new challenges arise in transistor performance
Solution Approach 1:
The invention modifies process parameters (such as deposition conditions, pre-treatment parameters, or etch conditions) to achieve uniform inner spacer formation at scaled dimensions. This parameter optimization maintains transistor performance (carrier mobility, drive current) while enabling continued scaling for improved production efficiency
Solution Approach 2:
Pre-treatment of the sacrificial gate structure is performed before inner spacer formation to ensure optimal conditions for scaled device fabrication. This preliminary action addresses the challenges of scaling by preparing surfaces that enable uniform spacer deposition at smaller dimensions, maintaining transistor performance while supporting continued scaling for higher productivity
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 pre-treatment process enhances the uniformity of critical dimensions and reduces surface roughness, improving the electrical performance and reliability of semiconductor devices by minimizing damage to the epitaxial source/drain features.
Implementation Method 1
A pre-treatment process involving radical surface treatment and surface cleaning is applied to remove residues and improve surface roughness
Implementation Method 2
followed by selective etching to form uniform critical dimensions and smoother sidewalls
Data Source
AI summary
Various embodiments of the present disclosure provide a method for forming a semiconductor device structure. The method includes forming a sacrificial gate structure over a portion of a fin structure comprising a plurality of first semiconductor layers and a plurality of second semiconductor layers alternatingly stacked. The method also includes removing a portion of the fin structure not covered by the sacrificial gate structure, subjecting exposed surfaces of each first and second semiconductor layers to at least one radical species, removing an edge portion of the second semiconductor layers to form a cavity between two adjacent first semiconductor layers, and forming a dielectric spacer in the cavity.