Mixed Wavy Epitaxy for FinFET Source/Drain Contact Resistance
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Solution Overview
Problem
In the formation of Fin Field-Effect Transistors (FinFETs), existing methods face challenges in achieving both low contact resistance and preventing fin bending, as epitaxy regions grown from neighboring semiconductor fins often merge, leading to planar top surfaces that do not effectively address reliability and contact resistance issues.
Innovation Solution
The formation of a merged epitaxy region with both wavy and non-wavy portions, where the non-wavy portion prevents fin bending and the wavy portion increases contact area, thereby reducing contact resistance, is achieved by recessing semiconductor fins and growing epitaxy regions with specific height relationships between fin spacers and epitaxy layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If epitaxy regions are grown from recesses of neighboring semiconductor fins, then source/drain regions are formed, but the epitaxy regions merge and form planar top surfaces that increase contact resistance
Solution Approach 1:
The patent applies local quality by creating different surface profiles in different regions of the epitaxy structure. Specifically, the epitaxy regions are designed to have non-planar top surfaces with elevated portions between adjacent fins, while maintaining merged characteristics in other areas. This localized variation in surface geometry reduces contact resistance by providing better contact interfaces without compromising the merged structure integrity.
Solution Approach 2:
The patent utilizes curvature by forming non-planar, wavy top surfaces on the merged epitaxy regions. The elevated portions and curved interfaces between adjacent epitaxy regions create increased surface area and improved contact geometry. This curved surface approach replaces the traditional planar interface, thereby reducing contact resistance through enhanced electrical contact between source/drain regions and contact plugs.
2Reliability
If epitaxy regions are grown to merge between fins, then source/drain regions are formed, but fin bending occurs reducing device reliability
Solution Approach 1:
The patent applies segmentation by dividing the epitaxy growth process and structure into distinct functional zones. The epitaxy regions are formed as separate entities from each fin recess but are designed to merge at controlled interfaces. This segmented approach allows independent control of each epitaxy region's growth and morphology, enabling prevention of fin bending through controlled merging while managing structural complexity through modular design.
Solution Approach 2:
The patent utilizes composite material principles by creating merged epitaxy structures that combine characteristics of multiple adjacent fin regions. The merged epitaxy regions form a composite structure that integrates material from multiple sources, providing mechanical support that prevents fin bending. This composite approach manages device complexity by creating a unified structure from multiple components, where the merged nature provides both structural integrity and electrical functionality.
3Quantity of substance
If planar top surfaces are formed on merged epitaxy regions, then manufacturing is simplified, but contact area is reduced increasing contact resistance
Solution Approach 1:
The patent applies curvature by forming non-planar, wavy top surfaces on the merged epitaxy regions. The elevated portions and curved interfaces between adjacent epitaxy regions create increased surface area and improved contact geometry. This curved surface approach replaces the traditional planar interface, thereby reducing contact resistance through enhanced electrical contact between source/drain regions and contact plugs.
4Reliability
If non-wavy epitaxy regions are used, then fin bending is prevented, but contact area is insufficient leading to high contact resistance
Solution Approach 1:
The patent applies local quality by creating different surface profiles in different regions of the epitaxy structure. Specifically, the epitaxy regions are designed to have non-planar top surfaces with elevated portions between adjacent fins, while maintaining merged characteristics in other areas. This localized variation in surface geometry reduces contact resistance by providing better contact interfaces without compromising the merged structure integrity.
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 reduces contact resistance and enhances the reliability of FinFETs by creating a merged epitaxy region with increased contact area and sharper corners, which improves the formation of source/drain regions and reduces fin bending.
Implementation Method 1
growing epitaxy regions starting from the recesses
Data Source
AI summary
A method includes forming a first fin-group having has a plurality of semiconductor fins, and a second fin-group. The plurality of semiconductor fins include a first semiconductor fin, which is farthest from the second fin-group among the first fin-group, a second semiconductor fin, and a third semiconductor fin, which is closest to the second fin-group among the first fin-group. The method further includes performing an epitaxy process to form an epitaxy region based on the plurality of semiconductor fins. The epitaxy region includes a first portion and a second portion. The first portion is in middle between the first semiconductor fin and the second semiconductor fin. The first portion has a first top surface. The second portion is in middle between the second semiconductor fin and the third semiconductor fin. The second portion has a second top surface lower than the first top surface.