Metallic Source-Drain Stress Structure for Stacked Nanosheet Current Flow
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Solution Overview
Problem
Defects in the source-drain material of stacked nanosheet structures in semiconductor devices lead to reduced current flow through channels, affecting the performance of horizontal gate-all-around (hGAA) and complementary field effect transistors (CFETs).
Innovation Solution
The formation of compressive stress materials, such as tin germanium (SnGe) epitaxial layers, is introduced to prevent crystal structure merging during epitaxial growth, thereby reducing dislocations and maintaining compressive forces on the channels, enhancing current flow performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If epitaxial growth process is continued to form source-drain material, then source-drain structure is completed, but crystal structure merging occurs causing defects that reduce current flow
Solution Approach 1:
The source-drain formation process is segmented into distinct stages: initial epitaxial growth to form a first portion, followed by a second epitaxial growth process to form a remaining portion. This segmentation prevents crystal structure merging defects by controlling the growth sequence and conditions, thereby maintaining high current flow through the channel while ensuring crystal structure integrity.
2Productivity
If source-drain material is formed without compressive stress, then manufacturing is simpler, but current flow performance is reduced
Solution Approach 1:
The patent applies parameter changes by introducing compressive stress into the source-drain structure through controlled epitaxial growth conditions and material composition. This modifies the physical parameters of the source-drain material to enhance carrier mobility and current flow performance, accepting increased structural complexity as a trade-off for improved device 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 implementation of compressive stress materials increases current flow by at least 5% over traditional source-drain formations by preserving compressive forces on the channels, improving device performance.
Implementation Method 1
Methods and architectures for providing compressive forces on a channel area in a stacked nanosheet structure using source-drains are provided herein
Implementation Method 2
forming an epitaxial growth layer on each of a plurality of channels of the stacked nanosheet structure using an epitaxial growth process
Data Source
AI summary
A method leverages compressive stress forces in forming a source-drain for a stacked nanosheet structure. The method may include forming an epitaxial growth layer on each of a plurality of channels of the stacked nanosheet structure where the channels are a silicon-based material and where the channels are separated by inner spacers of a dielectric material, stopping the epitaxial growth process prior to a crystal structure of one of the epitaxial growth layers on one channel of the stacked nanosheet structure merging into another crystal structure of any other one of the epitaxial growth layers on another channel of the stacked nanosheet structure or merging into surfaces of the inner spacers, and forming a compressive stress material on the plurality of epitaxial growth layers. In some embodiments, the compressive stress material fills the source-drain cavity and in other embodiments, a metal fill with compressive stress fills the source-drain cavity.