FinFET Epitaxial Source/Drain Layout for Isolation and Contact Alignment
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Solution Overview
Problem
As IC feature sizes shrink, multigate devices face challenges with epitaxial source/drain configurations that lead to unintentional merging, electrical shorting, and performance degradation due to reduced contact landing windows and alignment issues, particularly in FinFETs.
Innovation Solution
Optimized lateral dimensions and spacings for epitaxial source/drains in FinFETs, including increased widths and tailored spacings to minimize merging and enhance contact landing windows, while accounting for different type FinFET profiles and additional isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If IC feature sizes are reduced to increase device density, then more devices can be packed in a smaller area, but epitaxial source/drain structures experience unintentional merging and electrical shorting
Solution Approach 1:
The source/drain region is segmented into multiple discrete epitaxial source/drain structures separated by isolation fins rather than forming continuous merged structures. This segmentation prevents unwanted electrical connections while maintaining the benefits of scaled feature sizes.
Solution Approach 2:
Isolation fins are introduced as intermediary structures between adjacent epitaxial source/drain regions. These isolation fins act as barriers that prevent merging and electrical shorting of source/drain structures while allowing the overall device density to be increased through scaling.
2Manufacturing precision
If epitaxial source/drain widths are increased to improve contact landing windows, then contact alignment becomes easier, but the spacing between source/drain structures must be increased to prevent merging
Solution Approach 1:
The solution applies different dimensional characteristics to different parts of the source/drain structure. The epitaxial source/drain structures have optimized widths for contact alignment in their local regions, while the isolation fins provide spacing in the horizontal direction. This local optimization allows improved contact alignment without requiring increased overall spacing between devices.
3Productivity
If multigate devices are scaled down to achieve smaller IC feature sizes, then higher integration is achieved, but manufacturing complexity increases due to alignment issues
Solution Approach 1:
The isolation fins are formed before the epitaxial source/drain structures are deposited. This preliminary action establishes the spacing and isolation framework in advance, which then guides the subsequent source/drain formation process and simplifies alignment operations rather than increasing manufacturing complexity.
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
Enhances FinFET density and performance by preventing unintentional merging, improving contact alignment, and reducing device remain defects, thus maintaining reliability and functionality in advanced technology nodes.
Implementation Method 1
epitaxial source/drain configurations
Data Source
AI summary
A semiconductor structure includes a first multigate device, a second multigate device, and an isolation structure. The first multigate device has a first channel layer extending between first epitaxial source/drains along a first direction. The second multigate device has a second channel layer extending between second epitaxial source/drains along the first direction. The first epitaxial source/drains and second epitaxial source/drains have a first width and a second width, respectively, along a second direction that is different than the first direction. The isolation structure includes a dielectric fin over a substrate isolation feature. The dielectric fin is between the first epitaxial source/drains and the second epitaxial source/drains. The dielectric fin has a third width along the second direction. A distance between the first epitaxial source/drains and the second epitaxial source/drains along the second direction is greater than the third width, less than the second width, and less than the first width.