GAA Nanosheet Gate Structure for Uniform Channel and Gate Dimensions
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Solution Overview
Problem
The development of three-dimensional designs, such as multi-gate field effect transistors (FETs), particularly gate-all-around (GAA) FETs, faces challenges in achieving uniformity and efficiency due to non-uniform channel regions and gate structures, leading to issues like short-channel effects and increased device size.
Innovation Solution
A method involving the patterning of an epitaxial stack to form semiconductor fins, replacing sacrificial semiconductor layers with dielectric and metal gate structures, ensuring uniform nanosheet thickness and gate height, and forming high-k/metal gate structures around nanosheets to enhance device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If three-dimensional designs such as GAA FETs are adopted to increase device density and performance, then device density and performance are improved, but manufacturing complexity and achieving uniformity become more difficult
Solution Approach 1:
The channel region is divided into multiple discrete nanosheets stacked vertically, with each nanosheet providing an independent conduction path. This segmentation allows for better control of short-channel effects while maintaining high device density through the vertical stacking arrangement.
Solution Approach 2:
The gate electrode completely surrounds each nanosheet channel region in a nested configuration, with the gate wrapping around the channel from all sides. This gate-all-around structure provides maximum electrostatic control over the channel while maintaining a compact three-dimensional footprint.
2Reliability
If gate-all-around structure is implemented to reduce short-channel effects, then short-channel effects are reduced, but achieving uniform nanosheet thickness and gate dimensions becomes more difficult
Solution Approach 1:
Sacrificial semiconductor layers are deposited as part of the epitaxial stack before the actual nanosheet formation process. These sacrificial layers define the precise positions and thicknesses of the future nanosheets, enabling uniform nanosheet formation through controlled removal of the sacrificial material that defines the nanosheet spacing and dimensions.
Solution Approach 2:
The sacrificial semiconductor layers serve as intermediary structures during manufacturing, temporarily present to define nanosheet geometry and spacing. These intermediary layers are removed after defining the nanosheet structure, leaving behind uniformly spaced nanosheets with precise thickness control.
3Reliability
If larger device structures are used to accommodate three-dimensional designs, then device functionality is maintained, but cell capacitance and device size increase
Solution Approach 1:
The transistor structure transitions from a planar two-dimensional configuration to a three-dimensional vertical configuration with multiple nanosheets stacked along the vertical axis. This dimensional change increases the effective channel area and capacitance without increasing the lateral footprint, allowing higher device density while maintaining compact cell size.
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 results in improved logic cell speed and reduced cell capacitance by ensuring uniform nanosheet and gate structure dimensions, addressing non-uniformity and size issues in GAA FETs.
Implementation Method 1
depositing an epitaxial stack over a semiconductor substrate, wherein the epitaxial stack comprises a plurality of first and second semiconductor layers alternatively arranged over the semiconductor substrate
Data Source
AI summary
A method for manufacturing an integrated circuit device is provided. The method includes depositing an epitaxial stack over a semiconductor substrate, wherein the epitaxial stack comprises a plurality of first and second semiconductor layers alternatively arranged over the semiconductor substrate and a third semiconductor layer over the first and second semiconductor layers; patterning the epitaxial stack to form a semiconductor fin; forming a dummy gate structure over the semiconductor fin; replacing the third semiconductor layer in the semiconductor fin with a dielectric layer; and replacing the dummy gate structure and first semiconductor layers in the semiconductor fin with a metal gate structure.