Dummy Nanosheet Channel Layers for Multi-Vt Patterning Damage Reduction
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Solution Overview
Problem
The existing semiconductor fabrication techniques for non-planar field-effect transistor (FET) devices, such as nanosheet FETs, face challenges in maintaining uniformity and performance due to the unwanted growth of interfacial oxide layers during work function metal patterning, which degrades device performance and channel layer non-uniformity.
Innovation Solution
The implementation of dummy nanosheet channel layers above active nanosheet channel layers to protect them from oxidation during work function metal patterning, using a directional plasma etch process, where the dummy layers serve as oxygen infusion blocking layers to prevent oxidation and maintain channel layer integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If work function metal patterning is performed using directional plasma etch process, then multiple threshold voltages can be achieved for optimized device performance, but interfacial oxide layers grow on active nanosheet channel layers causing non-uniformity and degraded device performance
Solution Approach 1:
A dummy nanosheet channel layer is introduced as an intermediary protective layer between the plasma etch environment and the active nanosheet channel layers. This dummy layer absorbs the harmful oxygen infusion from the plasma etch process, preventing oxidation of the active channel layers while allowing the work function metal patterning to proceed for multi-Vt device fabrication
2Adaptability or versatility
If work function metal patterning is performed to tune threshold voltages, then device performance can be optimized for different applications, but oxidation of active nanosheet channel layers occurs resulting in degraded device performance
Solution Approach 1:
The dummy nanosheet channel layer is formed in advance before the work function metal patterning process. This preliminary protective layer is positioned to cover the active nanosheet channel layers, preventing oxidation during subsequent processing steps. The dummy layer serves its protective function throughout the patterning process and can be removed later after the work function metal layers are successfully patterned
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 ensures the preservation of active nanosheet channel layers' integrity and uniformity, enhancing the performance and reliability of nanosheet FET devices by preventing oxidation and maintaining consistent interfacial oxide layers, thus improving device performance and integration density.
Implementation Method 1
the dummy nanosheet channel layer serves as an oxygen infusion blocking layer to protect the active nanosheet channel layer from being infused with oxygen and oxidized by a directional plasma etch process
Implementation Method 2
a directional plasma etch process performed during the work function metal patterning process
Data Source
AI summary
Devices and methods are provided to fabricate nanosheet field-effect transistor devices having dummy nanosheet channel layers disposed above active nanosheet channel layers to protect the active nanosheet channel layers from oxidation during work function metal patterning processes that are implemented as part of a multi-threshold voltage process module. The dummy nanosheet channel layers have a reduced thickness so that the dummy nanosheet layers do not function as active channel layers of the nanosheet field-effect transistor devices. The dummy nanosheet channel layers serve as oxygen infusion blocking layers to protect the active nanosheet channel layers from being infused with oxygen and oxidized by a directional plasma etch process performed during a work function metal patterning process.