Nanosheet Source-Drain Template on Bottom Dielectric Isolation
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Solution Overview
Problem
The formation of source and drain regions in gate-all-around (GAA) devices with a bottom dielectric isolation layer is hindered by defects during epitaxial growth, as the growth is limited to the sidewall and not the bottom, affecting device performance.
Innovation Solution
A method involving the formation of a superlattice structure on a bottom dielectric isolation layer, followed by depositing a template material in trenches, crystallizing it, and forming source and drain regions, allowing epitaxial growth on both the sidewall and bottom of the trenches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If epitaxial growth is performed only from the sidewall in the presence of a bottom dielectric isolation layer, then the source and drain regions can be formed with the BDI layer providing isolation, but numerous defects occur during growth/formation of the source and drain regions
Solution Approach 1:
The patent applies preliminary action by forming a template structure in the source and drain trenches before performing epitaxial growth. This template is created by depositing a first material and then a second material to establish a prepared surface that enables defect-free epitaxial growth from the bottom, eliminating the need for sidewall-only growth while maintaining processability.
2Reliability
If a bottom dielectric isolation layer is added to enhance device performance, then electrostatic control and device performance are improved, but epitaxial growth can only occur from the sidewall resulting in numerous defects
Solution Approach 1:
The patent forms a template structure comprising a first material and a second material deposited on the bottom dielectric isolation layer before epitaxial growth. This preliminary template preparation enables the epitaxial growth to proceed from the bottom surface with high precision, eliminating defects while preserving the electrostatic control benefits of the BDI layer.
3Ease of manufacture
If sidewall-only epitaxial growth is used with bottom dielectric isolation, then the BDI layer provides proper isolation, but the source and drain regions contain numerous defects
Solution Approach 1:
The patent introduces a preliminary template formation step where a first material and a second material are deposited in the source and drain trenches on top of the bottom dielectric isolation layer. This template structure enables subsequent epitaxial growth to occur from the bottom surface rather than sidewalls, achieving both proper isolation functionality and defect-free source/drain regions.
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 enhances the formation of source and drain regions, improving device performance by enabling uniform growth and reducing defects, thereby enhancing electrostatic control and reducing parasitic capacitance.
Implementation Method 1
crystallizing the template material
Implementation Method 2
annealing the substrate to crystallize the template material
Implementation Method 3
epitaxial source/drain can only be grown from the sidewall and not from the bottom
Data Source
AI summary
Semiconductor devices and methods of manufacturing the same are described. The method includes forming a bottom dielectric isolation (BDI) layer on a substrate and depositing a template material in the source/drain trench. The template material is crystallized. Epitaxially growth of the source and drain regions then proceeds, which growth advantageously occurring on the bottom and sidewalls of the source and drain regions.