Cobalt Gate Fill for Lower Threshold Voltage in Semiconductors
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Summary
Problems
As semiconductor integrated circuits scale down, reducing threshold voltage becomes challenging without adversely affecting other transistor aspects, particularly due to difficulties in increasing the thickness of the work function metal layer.
Innovation solutions
A gate structure using a cobalt fill instead of a tungsten fill, formed through a process involving Physical Vapor Deposition, Chemical Vapor Deposition, and Electro-Chemical Plating, with a glue layer for better adhesion, allows for a lower threshold voltage without increasing the work-function metal layer size.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If the thickness of the work function metal layer is increased to reduce threshold voltage, then the threshold voltage is reduced, but the manufacturing complexity and difficulty increase due to scaling constraints
Why choose this principle:
The patent changes the material parameter from traditional work function metals (titanium nitride, tungsten) to cobalt, which has different physical and chemical properties including lower contact resistance and better adhesion characteristics. This material substitution allows achieving the same electrical function with different structural requirements, resolving the contradiction between threshold voltage control and manufacturing complexity
Principle concept:
If the thickness of the work function metal layer is increased to reduce threshold voltage, then the threshold voltage is reduced, but the manufacturing complexity and difficulty increase due to scaling constraints
Why choose this principle:
The patent employs a multi-layer structure where a thin cobalt layer is deposited and then selectively removed in non-active areas through wet etching. This approach uses a temporary, easily removable material that simplifies the overall manufacturing process by enabling simple wet etch release rather than requiring complex patterning of the work function layer itself
Application Domain
Data Source
AI summary:
A gate structure using a cobalt fill instead of a tungsten fill, formed through a process involving Physical Vapor Deposition, Chemical Vapor Deposition, and Electro-Chemical Plating, with a glue layer for better adhesion, allows for a lower threshold voltage without increasing the work-function metal layer size.
Abstract
A method for forming a gate structure includes forming a trench within an interlayer dielectric layer (ILD) that is disposed on a semiconductor substrate, the trench exposing a top surface of the semiconductor substrate, forming an interfacial layer at a bottom of the trench, forming a dielectric layer within the trench, forming a work function metal layer on the dielectric layer, forming an in-situ nitride layer on the work function metal layer in the trench, performing a first cobalt deposition process to form a cobalt layer within the trench, performing a second cobalt deposition process to increase a thickness of the cobalt layer within the trench, and performing an electrochemical plating (ECP) process to fill the trench with cobalt.