Nanoribbon Fin Capping for Stable Si/SiGe Superlattice Fabrication
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Solution Overview
Problem
Nanosheet and nanoribbon transistor devices face issues of fin bending and wiggling during fabrication due to the presence of SiGe layers in Si/SiGe superlattices, which lead to mechanical instability and lattice distortion, particularly in 3D stacked transistor devices.
Innovation Solution
Implementing a cap layer, such as a Silicon cap layer, during the fabrication process to stabilize the fin structures and prevent oxidation of SiGe layers, which is later removed before the sacrificial SiGe layers are removed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SiGe layers are used in Si/SiGe superlattices for nanoribbon fin fabrication, then the transistor device performance is improved, but the fins become mechanically unstable and prone to bending and wiggling
Solution Approach 1:
A cap layer is introduced as an intermediary element between the SiGe sacrificial layer and the external environment. This cap layer serves as a protective mediator that prevents direct exposure of the SiGe layer to oxidizing conditions, thereby maintaining fin mechanical stability while preserving the beneficial electrical properties of the Si/SiGe superlattice structure
Solution Approach 2:
The cap layer is formed preliminarily before the SiGe sacrificial layer is removed. This preliminary protective action prevents oxidation of the SiGe layer during subsequent fabrication steps, ensuring that the fin structure remains mechanically stable throughout the fabrication process until the cap layer is selectively removed
2Productivity
If the fin aspect ratio is increased for better device scaling, then the device density is improved, but the fins become more susceptible to bending and distortion
Solution Approach 1:
The cap layer provides beforehand cushioning or mechanical support to high aspect ratio fins during fabrication. This protective layer acts as a structural reinforcement that prevents bending and distortion of slender fins, enabling the fabrication of higher aspect ratio structures with improved device density while maintaining manufacturing precision
3Ease of manufacture
If the SiGe layers are exposed during fabrication, then the fabrication process is simplified, but the SiGe layers oxidize causing lattice distortion and fin wiggling
Solution Approach 1:
The cap layer serves as a protective intermediary that allows the SiGe layer to remain exposed and accessible for fabrication processes while simultaneously preventing oxidation. This mediator enables simplified fabrication procedures without introducing the harmful effects of SiGe oxidation and lattice distortion
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 cap layer enhances fabrication yield and allows for higher aspect ratio fins, enabling better scaling and fabrication of devices like 3D stacked nanoribbon CFET devices by reducing deformation during the process.
Implementation Method 1
prevent oxidation of SiGe layers
Data Source
AI summary
In embodiments herein, a cap layer (e.g., a layer comprising Silicon) is deposited on a fin formed in a superlattice structure, e.g., during a fabrication process.