Source/Drain Contact Structure With CESL Undercuts for Lower Resistance
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Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, challenges arise in reducing contact resistance and improving performance, particularly in FinFETs, due to the need for increased integration density and efficient surface area contact for source/drain regions.
Innovation Solution
The formation of undercuts in a contact etch stop layer (CESL) between source/drain regions and the overlying inter-layer dielectric layer exposes more surface area, allowing silicides and contacts to effectively contact the source/drain regions, thereby reducing contact resistance and enhancing transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If minimum feature sizes are reduced to increase integration density, then more components can be integrated into a given area, but contact resistance between source/drain regions increases
Solution Approach 1:
The patent introduces undercuts in the CESL that extend laterally beneath the source/drain regions, adding a horizontal dimension to the contact area. This dimensional change allows contacts to reach the source/drain regions through the undercut pathways, effectively increasing the contact surface area without increasing the vertical profile height, thus reducing contact resistance while maintaining miniaturization
Solution Approach 2:
The undercuts act as intermediary structures that facilitate electrical contact between the contacts and source/drain regions. By creating lateral pathways through the CESL, the undercuts serve as intermediate conduits that enable current flow without requiring direct vertical contact, thereby reducing contact resistance in scaled devices
2Productivity
If minimum feature sizes are reduced to increase integration density, then more components can be integrated into a given area, but manufacturing complexity increases
Solution Approach 1:
The undercuts are formed in the CESL before the final contact formation step. This preliminary action prepares the contact pathways in advance, allowing subsequent contact deposition to proceed without additional complex processing steps. The undercuts are created during the CESL formation process itself, integrating the complexity into an existing step rather than adding new process complexity
3Reliability
If undercuts are formed in the CESL to expose greater surface area for contacts, then contact resistance decreases, but manufacturing process complexity increases
Solution Approach 1:
The formation of undercuts in the CESL is merged with the existing CESL deposition and patterning processes. The same deposition tools and etch processes used for CESL formation are utilized to create the undercuts, combining multiple functions into existing process steps rather than introducing separate dedicated process steps, thereby minimizing additional manufacturing complexity
Data Source
AI summary
In an embodiment, a structure includes: a gate stack over a channel region of a substrate; a source/drain region adjacent the channel region; a first inter-layer dielectric (ILD) layer over the source/drain region; a silicide between the first ILD layer and the source/drain region, the silicide contacting a top surface of the source/drain region and a bottom surface of the source/drain region; and a first source/drain contact having a first portion and a second portion, the first portion of the first source/drain contact disposed between the silicide and the first ILD layer, the second portion of the first source/drain contact extending through the first ILD layer and contacting the silicide.