Multi-layer Epitaxial Source Drain Structure for Semiconductor Devices
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Solution Overview
Problem
The semiconductor industry faces challenges in scaling down device dimensions due to increased source/drain tunneling, leading to leakage current and short channel effects, particularly in gate-all-around (GAA) devices, where defects like voids and clustering in epitaxial source/drain structures impact device performance and yield.
Innovation Solution
A multi-operation epitaxial source/drain formation process involving plasma-activated nitridation of a silicon-based film, followed by the deposition of a second epitaxial structure, forms a multi-layer epitaxial source/drain structure, reducing defects and enhancing carrier mobility, applicable to GAA, finFET, and planar FETs across various technology nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device dimensions are scaled down to increase storage capacity and processing speed, then storage capacity and processing speed are improved, but source/drain tunneling increases leading to leakage current and short channel effects
Solution Approach 1:
The source/drain structure is segmented into multiple epitaxial layers with different materials (e.g., SiGe and Si) and doping concentrations. This segmentation creates a multi-layer structure that reduces tunneling effects while maintaining high carrier mobility, thereby reducing leakage current without sacrificing processing speed.
Solution Approach 2:
Composite materials consisting of different semiconductor layers (e.g., SiGe/Si heterostructures) are used to form the source/drain regions. The composite structure exploits the beneficial properties of each material: SiGe provides high hole mobility while Si provides low defect density, collectively reducing leakage current while maintaining high-speed performance.
2Ease of manufacture
If conventional epitaxial deposition is used for source/drain structures, then device fabrication is simplified, but defects like voids and clustering occur reducing device yield
Solution Approach 1:
A seed layer is deposited preliminarily on the substrate before the main epitaxial growth. This seed layer prepares the surface for subsequent epitaxial deposition, ensuring uniform nucleation and reducing void formation. The preliminary action maintains fabrication simplicity while significantly reducing defect density.
Solution Approach 2:
Epitaxial deposition parameters such as temperature, pressure, and gas flow rates are optimized and changed during the deposition process. These parameter changes enable precise control over film quality and defect formation, reducing voids and clustering while maintaining ease of manufacture through standardized process control.
3Productivity
If plasma treatment is applied to silicon-based films to facilitate epitaxial growth, then epitaxial growth is enhanced, but plasma-induced damage occurs affecting device reliability
Solution Approach 1:
Plasma treatment is applied selectively to specific regions of the silicon-based film rather than uniformly across the entire surface. This localized plasma treatment enhances epitaxial growth rate in critical areas while minimizing plasma-induced damage in other regions, thereby maintaining device reliability.
Solution Approach 2:
The plasma treatment step is performed rapidly and then immediately followed by epitaxial deposition, minimizing the time the film is exposed to plasma conditions. This approach rushes through the potentially damaging plasma phase while still achieving the desired surface modification for enhanced epitaxial growth, balancing growth rate enhancement with damage reduction.
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 reduces short channel effects, voids, and defects, improving device performance, reliability, and yield by forming nitride layers that facilitate epitaxial growth without plasma-induced damage, suitable for advanced technology nodes like 3 nm and 5 nm.
Implementation Method 1
plasma-activated nitridation of a silicon-based film
Implementation Method 2
plasma-activated nitridation of a silicon-based film
Implementation Method 3
deposition of a second epitaxial structure forms a multi-layer epitaxial source/drain structure
Data Source
AI summary
The present disclosure describes a semiconductor device that includes nanostructures on a substrate and a source/drain region in contact with the nanostructures. The source/drain region includes (i) a first epitaxial structure embedded in the substrate; (ii) a nitride layer on the first epitaxial structure; and a second epitaxial structure on the first epitaxial structure. The semiconductor device also includes a gate structure formed on the nanostructures.