Epitaxial Source/Drain Depth Tuning for Multigate SCE Mitigation
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Solution Overview
Problem
Existing multigate devices face challenges in optimizing reliability as they continue to scale, particularly in mitigating short-channel effects (SCEs) and ensuring optimal performance across varying active region sizes.
Innovation Solution
The implementation of epitaxial source/drain structures with tailored depth and height configurations for source/drain recesses, adjusted based on the active region size, to minimize SCEs and enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If multigate devices continue to scale down, then IC technology can be aggressively scaled maintaining gate control, but device reliability deteriorates due to increased short-channel effects
Solution Approach 1:
The patent applies local quality by creating epitaxial source/drain structures with different depths at different locations. Specifically, the first epitaxial source/drain structure has a first depth while the second epitaxial source/drain structure has a second depth that is different from the first depth. This localized variation in depth allows different regions of the device to have optimized properties for their specific functional requirements, thereby maintaining reliability as devices scale down.
Solution Approach 2:
The patent changes the depth parameter of the epitaxial source/drain structures to address reliability issues during scaling. By adjusting the depth of the epitaxial structures (first depth for first source/drain, second depth for second source/drain), the invention modifies the electrical characteristics and strain distribution in the channel, which helps mitigate short-channel effects and maintain device reliability despite continued scaling.
2Reliability
If epitaxial source/drain structures with different depths are implemented, then short-channel effects are mitigated, but manufacturing complexity increases
Solution Approach 1:
The patent segments the source/drain region into multiple epitaxial structures with different depths. The first epitaxial source/drain structure and second epitaxial source/drain structure are formed as separate entities with controlled depth differences. This segmentation allows each structure to be optimized independently for its specific role in mitigating short-channel effects while maintaining overall device functionality.
Solution Approach 2:
The patent introduces a vertical dimension variation by forming epitaxial structures at different depths. Instead of uniform depth throughout the source/drain region, the invention creates a depth gradient where the first epitaxial structure has a first depth and the second epitaxial structure has a second depth. This dimensional change adds control over strain distribution and electrical characteristics without fundamentally complicating the manufacturing process.
3Power
If epitaxial structures provide strain to channel regions, then drive current is enhanced, but control over strain distribution becomes more difficult
Solution Approach 1:
The patent applies local quality to strain distribution by creating epitaxial structures with different depths at different locations. The first epitaxial source/drain structure provides strain to a first channel region while the second epitaxial source/drain structure provides strain to a second channel region. This localized approach allows precise control over where strain is applied, enhancing drive current in specific regions while maintaining overall device performance.
Solution Approach 2:
The patent changes the depth parameter of the epitaxial structures to control strain distribution. By adjusting the depth of the first epitaxial structure relative to the second epitaxial structure, the invention can tune the amount and distribution of strain in the channel regions. This parameter change enables optimization of drive current while maintaining manageable control over strain distribution through controlled epitaxial growth processes.
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 effectively mitigates short-channel effects and optimizes performance by providing appropriate strain to channel regions, enhancing drive current and reliability across different active region sizes.
Implementation Method 1
epitaxial source/drain structures with tailored depth and height configurations for source/drain recesses
Data Source
AI summary
Epitaxial source/drain structures for enhancing performance of multigate devices, such as fin-like field-effect transistors (FETs) or gate-all-around (GAA) FETs, and methods of fabricating the epitaxial source/drain structures, are disclosed herein. An exemplary source/drain structure extends from a topmost channel layer to a depth into a semiconductor substrate. The source/drain structure includes an undoped epitaxial layer with a trough-shaped top surface, a first doped epitaxial layer over the undoped epitaxial layer, a second doped epitaxial layer over the first epitaxial layer, and a third doped epitaxial layer over the second doped epitaxial layer. A thickness of the undoped epitaxial layer is less than the depth of the epitaxial source/drain structure into the semiconductor substrate. The thickness and the depth are tuned based on a size of an active region to which the epitaxial source/drain structure belongs, such that the epitaxial source/drain structure mitigates short channel effects while optimizing performance.