Semiconductor Wrap-Around Contact Structure for Reduced Parasitic Capacitance
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Solution Overview
Problem
Conventional wrap-around-contact fabrication for semiconductor devices faces challenges such as increased parasitic capacitance between the metal contact and gate, Ge diffusion issues, non-uniform epitaxial growth, and additional processing steps, which complicate the reduction of contact resistance as transistor scaling continues beyond the 5 nm technology node.
Innovation Solution
A semiconductor structure with a recessed source/drain region and a metal contact having a first portion and a second portion, where the second portion is wider and disposed within the recessed portion, to reduce parasitic capacitance and contact resistance without requiring additional sacrificial layers or complex processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wrap-around-contact fabrication is used, then contact resistance reduction is achieved, but parasitic capacitance between metal contact and gate increases
Solution Approach 1:
The contact structure transitions from a planar configuration to a three-dimensional wrap-around configuration that extends underneath the gate. This dimensional change allows the contact to achieve lower resistance by increasing contact area with the source/drain region while positioning the metal contact laterally beneath the gate to minimize overlapping capacitance.
Solution Approach 2:
The metal contact is divided into multiple portions: a first portion at the top surface and a second portion extending underneath the gate. This segmentation allows different portions to serve different functions - the first portion provides lateral connection while the second portion provides vertical connection with minimal gate overlap, thereby reducing parasitic capacitance.
2Reliability
If conventional wrap-around-contact fabrication is used, then contact resistance reduction is achieved, but Ge diffusion issues occur
Solution Approach 1:
A liner layer is introduced as an intermediary between the metal contact and the semiconductor structure. This liner acts as a diffusion barrier that prevents Ge diffusion from the source/drain region into the metal contact while allowing the contact to maintain its low-resistance wrap-around configuration.
3Reliability
If conventional wrap-around-contact fabrication is used, then contact resistance reduction is achieved, but non-uniform epitaxial growth occurs
Solution Approach 1:
The problematic epitaxial sacrificial layer is removed from the process. Instead of using epitaxial growth to form the contact structure, the invention directly forms the metal contact in a wrap-around configuration, eliminating the issues of non-uniform epitaxial growth while achieving the same contact resistance reduction benefit.
4Reliability
If conventional wrap-around-contact fabrication is used, then contact resistance reduction is achieved, but device complexity increases due to additional processing steps
Solution Approach 1:
The formation of the wrap-around contact is merged with the existing contact formation process. The metal contact is deposited and patterned in a single process sequence that simultaneously creates both the lateral and underneath portions, eliminating the need for separate epitaxial growth, sacrificial layer removal, and additional cutting steps.
Data Source
AI summary
A semiconductor structure includes a source/drain region having a recessed portion. The semiconductor structure further includes a metal contact having a first portion and a second portion. The first portion of the metal contact has a first width and the second portion of the metal contact has a second width greater than the first width. At least a portion of the second portion of the metal contact is disposed in the recessed portion of the source/drain region.