Wrap-Around Silicide Layer for Low-Resistance Source/Drain Contacts
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Solution Overview
Problem
As semiconductor devices continue to shrink in size, forming silicide layers between source/drain contacts and epitaxial source/drain features becomes challenging due to decreasing gate pitches, leading to difficulties in achieving satisfactory silicide formation.
Innovation Solution
A process is developed to form a wrap-around silicide layer that covers the top surface and sidewalls of source/drain features, involving the deposition of a first contact etch stop layer and interlayer dielectric, followed by selective etching and silicide deposition, with additional layers deposited over the silicide layer to enhance the process window and reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional silicide formation processes are used, then manufacturing simplicity is maintained, but contact resistance increases and process window decreases as gate pitch shrinks
Solution Approach 1:
The silicide formation process is segmented into multiple sequential steps: forming first and second contact etch stop layers at different levels, selective etching to create access trenches, depositing silicide layer, and forming contact openings. This segmentation allows each step to be optimized independently, achieving low contact resistance through wrap-around silicide while maintaining manufacturability through standardized process modules
Solution Approach 2:
The silicide layer is formed to wrap around the source/drain features in three dimensions, extending along sidewalls and wrapping over top surfaces. This dimensional approach increases the contact surface area between silicide and source/drain regions, reducing contact resistance without requiring proportional increases in gate pitch or device area
2Productivity
If gate pitch is reduced to increase device density, then productivity increases, but silicide formation becomes more difficult
Solution Approach 1:
Contact etch stop layers are formed preliminarily before silicide deposition, with the first CESL extending along sidewalls and the second CESL wrapping over top surfaces. This preliminary structuring creates defined access trenches that guide subsequent silicide formation, enabling reliable silicide deposition even at reduced gate pitches where conventional approaches fail
Solution Approach 2:
The contact etch stop layers serve as intermediary structures that mediate between the source/drain features and the silicide layer. These intermediary layers provide a controlled interface that facilitates uniform silicide deposition and defines the wrap-around geometry, making the process robust against variations in gate pitch
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
The wrap-around silicide layer provides an improved process window and reduces contact resistance by increasing the contact surface area, addressing the challenges of shrinking gate pitches and enhancing the manufacturing efficiency of semiconductor devices.
Implementation Method 1
a silicide layer is then deposited to wrap over the source/drain feature
Implementation Method 2
The first interlayer dielectric layer and the first contact etch stop layer are etched to expose a top surface and sidewalls of the source/drain feature
Data Source
AI summary
Semiconductor structures and processes are provided. A semiconductor structure according to the present disclosure includes a channel region of a semiconductor body rising above an isolation feature, a gate structure wrapping over the channel region, a source/drain feature in contact with a sidewall of the channel region, a backside silicide layer disposed on a bottom surface of the source/drain feature, and a backside contact feature extending through the isolation feature to contact a bottom surface of the backside silicide layer. A sidewall of the backside contact feature is spaced apart from the isolation feature by a first backside contact etch stop layer (CESL) and a second backside CESL.