Wrap-Around Nanowire Contacts for Lower Source-Drain Resistance
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Solution Overview
Problem
The challenge in integrated circuit manufacturing lies in achieving efficient wrap-around contact structures for semiconductor nanowires and nanoribbons, as conventional methods result in significant loss of epitaxial source or drain material and insufficient contact area, leading to high contact resistance and limited device performance.
Innovation Solution
A self-aligned contact etch process is employed after polishing the nanowire or nanoribbon substrate, using a self-aligned mask to preserve fin material and deposit conformal contact metal with low Schottky barrier height, thereby reducing contact resistance and enhancing contact area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional contact structures are used for semiconductor nanowires and nanoribbons, then the fabrication process is simpler, but contact resistance is high and contact area is insufficient
Solution Approach 1:
The patent transitions from conventional planar contacts to wrap-around contacts that extend vertically along the sidewalls of nanowires and nanoribbons. This three-dimensional configuration increases the contact area by utilizing the vertical dimension, thereby reducing contact resistance without requiring excessive lateral space.
Solution Approach 2:
The fabrication process employs preliminary actions by forming sacrificial layers and using self-aligned mask techniques before final contact formation. These preparatory steps ensure precise alignment and preserve fin material, enabling the complex wrap-around structure to be fabricated systematically while managing process complexity.
2Reliability
If self-aligned contact etch process is employed with conformal contact metal deposition, then contact area increases and contact resistance decreases, but fabrication process complexity increases
Solution Approach 1:
The patent implements self-aligned mask techniques where previously formed structures serve as their own alignment references for subsequent etching and deposition steps. This self-service approach ensures precise positioning of wrap-around contacts relative to nanowires and nanoribbons, maximizing contact area while maintaining process control despite increased complexity.
Solution Approach 2:
The fabrication process applies local quality by using selective epitaxial growth to preserve fin material in specific regions while allowing contact formation in other areas. This localized material preservation ensures that critical regions maintain their structural integrity while contact areas are appropriately formed with low Schottky barrier height metals.
3Reliability
If wrap-around contact structures are formed, then contact resistance is reduced, but epitaxial source or drain material is lost
Solution Approach 1:
The patent applies local quality through selective epitaxial growth that preserves fin material in critical source and drain regions while allowing contact formation in appropriate areas. This selective preservation ensures that wrap-around contacts are formed without excessive loss of epitaxial material, maintaining the integrity of active device regions.
Solution Approach 2:
The fabrication process employs preliminary sacrificial layers and self-aligned mask techniques that protect epitaxial source and drain materials during contact formation. These preliminary protective measures ensure that wrap-around contacts are formed with minimal material loss, as the sacrificial structures are removed only after serving their protective function.
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 results in a 1.5 to 6 times reduction in contact resistance, improving integrated circuit performance by reducing active channel width and power consumption while maintaining high doping levels in the epitaxial region.
Implementation Method 1
A self-aligned contact etch process is employed after polishing the nanowire or nanoribbon substrate, using a self-aligned mask to preserve fin material
Implementation Method 2
deposit conformal contact metal with low Schottky barrier height, thereby reducing contact resistance
Data Source
AI summary
Wrap-around contact structures for semiconductor nanowires and nanoribbons, and methods of fabricating wrap-around contact structures for semiconductor nanowires and nanoribbons, are described. In an example, an integrated circuit structure includes a semiconductor nanowire above a first portion of a semiconductor sub-fin. A gate structure surrounds a channel portion of the semiconductor nanowire. A source or drain region is at a first side of the gate structure, the source or drain region including an epitaxial structure on a second portion of the semiconductor sub-fin, the epitaxial structure having substantially vertical sidewalls in alignment with the second portion of the semiconductor sub-fin. A conductive contact structure is along sidewalls of the second portion of the semiconductor sub-fin and along the substantially vertical sidewalls of the epitaxial structure.