Wrap-around contacts with localized metal silicide
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Solution Overview
Problem
The increasing middle-of-line contact resistance in advanced CMOS devices due to aggressive dimensional scaling poses a challenge, particularly at the silicide/source-drain interface, which affects the overall parasitic resistance and performance of semiconductor devices.
Innovation Solution
The method involves forming wrap-around contacts by conformally depositing a metal liner on semiconductor structures, forming a metal silicide liner around epitaxial source/drain regions, and selectively removing the liner to create discrete, contiguous segments that reduce contact resistance, thereby improving the integration and reducing the need for extreme ultraviolet lithography levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If dimensional scaling is aggressively pursued to improve device performance and reduce power consumption, then transistor performance and power consumption are improved, but middle-of-line contact resistance increases
Solution Approach 1:
The contact structure is segmented into multiple portions (first contact portion, second contact portion, third contact portion) that wrap around the source-drain region at different locations. This segmentation allows each portion to independently contribute to reducing contact resistance while maintaining the benefits of dimensional scaling.
Solution Approach 2:
The contact structure transitions from a planar configuration to a three-dimensional wrap-around configuration. The contact portions extend laterally and vertically around the source-drain region, utilizing the third dimension to increase contact area and reduce contact resistance without increasing the planar footprint.
2Reliability
If silicide contact length is increased by wrapping around the source-drain surface to reduce spreading resistance, then contact resistance is reduced, but device complexity increases
Solution Approach 1:
Multiple contact portions are merged into a single continuous wrap-around contact structure that envelops the source-drain region. This merging approach reduces the number of discrete contact elements and simplifies the overall structure while achieving reduced contact resistance through the extended contact path.
Solution Approach 2:
The wrap-around contact structure serves multiple functions simultaneously: it reduces contact resistance, provides mechanical support, and defines the active region boundaries. This multi-functionality reduces the need for additional separate structures, thereby simplifying the overall device architecture.
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 robust and simple integration of wrap-around contacts, reducing the number of EUVL levels required and circumventing issues associated with inverse tone patterning, leading to improved performance and reduced parasitic resistance in semiconductor devices.
Implementation Method 1
Conformal metallization processes using chemical vapor deposition (CVD) or atomic layer deposition (ALD) have been employed for forming metal contacts
Implementation Method 2
Conformal metallization processes using chemical vapor deposition (CVD) or atomic layer deposition (ALD) have been employed for forming metal contacts
Implementation Method 3
A metal silicide liner is formed on the epitaxial source/drain regions from the metal liner and wraps around these regions
Data Source
AI summary
A conformally deposited metal liner used for forming discrete, wrap-around contact structures is localized between pairs of gate structures and below the tops of the gate structures. Block mask patterning is employed to protect transistors over active regions of a substrate while portions of the metal liner between active regions are removed. A chamfering technique is employed to selectively remove further portions of the metal liner within the active regions. Metal silicide liners formed on the source/drain regions using the conformally deposited metal liner are electrically connected to source/drain contact metal following the deposition and patterning of a dielectric layer and subsequent metallization.