Semiconductor Channel Structure With Strained Source/Drain Epitaxy
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Solution Overview
Problem
As semiconductor devices continue to shrink in size, the complexity of fabrication processes increases, making it challenging to form reliable semiconductor devices at smaller scales.
Innovation Solution
The method involves forming an epitaxial seed layer over an isolation layer in source/drain openings, followed by the growth of source/drain epitaxial structures with a higher germanium concentration, inducing strain due to lattice mismatch, and forming a gate structure around the semiconductor channel layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes continue to decrease to increase functional density, then production efficiency is improved and costs are lowered, but fabrication process complexity increases and reliability deteriorates
Solution Approach 1:
The fabrication process is divided into multiple distinct stages: forming isolation layers in source/drain regions, selective epitaxial growth of semiconductor layers, pattern transfer, and gate formation. Each stage addresses specific requirements independently, making the overall complex process more manageable and reliable despite continued scaling.
Solution Approach 2:
Different regions of the device are given different properties: isolation layers are formed specifically in source/drain regions rather than uniformly across the substrate, and epitaxial growth is performed selectively in certain areas. This localized approach allows optimization for each region's specific functional requirements while maintaining overall device performance.
2Productivity
If feature sizes continue to decrease to increase functional density, then production efficiency is improved and costs are lowered, but fabrication reliability deteriorates
Solution Approach 1:
Isolation layers are formed in the source/drain regions before the main epitaxial growth and device fabrication steps. This preliminary action prepares the structure in advance, preventing potential reliability issues that would arise from forming these features later at smaller dimensions.
Solution Approach 2:
The isolation layers act as intermediary structures between the substrate and the active device regions. These layers mediate the interface properties, providing a controlled transition zone that enhances fabrication reliability by managing stress, contamination, and electrical properties at critical interfaces.
3Reliability
If source/drain epitaxial structures with higher germanium concentration are formed, then current flow is enhanced, but lattice mismatch strain increases
Solution Approach 1:
The germanium concentration in the epitaxial structures is varied to optimize device performance. By controlling the composition parameter, the material achieves higher carrier mobility and improved current flow while the resulting lattice mismatch strain is managed through the previously formed isolation layers and careful structural design.
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 improves device performance by reducing leakage current and parasitic capacitance, while also enhancing current flow through the semiconductor channel layers.
Implementation Method 1
growth of source/drain epitaxial structures with a higher germanium concentration, inducing strain due to lattice mismatch
Data Source
AI summary
A semiconductor device includes a substrate. Semiconductor channel layers are over the substrate. A gate structure wraps around each of the semiconductor channel layers. Source/drain epitaxial structures are on opposite sides of the gate structure. Epitaxial seed layers are below the source/drain epitaxial structures, respectively, in which a lattice constant of the epitaxial seed layers is different from a lattice constant of the source/drain epitaxial structures. Isolation layers are over the substrate and vertically below the epitaxial seed layers, respectively.