Transistor Gate Structure for Fluorine Retention and Vt Control
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Solution Overview
Problem
As semiconductor devices continue to shrink in size, challenges arise in maintaining the integration density and performance of transistors, particularly in retaining fluorine in work function metal layers within gate dielectrics, leading to dissociation issues that affect the flatband voltage and threshold voltage of transistors.
Innovation Solution
Implementing an aluminum treatment on the gate dielectric followed by a fluorine treatment to enhance fluorine retention in the work function metal layer, improving the diffusion of fluorine into the gate dielectric, thereby increasing flatband voltage and decreasing threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the minimum feature size is reduced to improve integration density, then more components can be integrated into a given area, but fluorine retention in work function metal layers deteriorates leading to dissociation issues
Solution Approach 1:
An aluminum treatment is performed on the gate dielectric before depositing the work function metal layer. This preliminary aluminum treatment modifies the gate dielectric surface to enhance subsequent fluorine retention in the work function metal layer, preventing dissociation issues that would otherwise occur at scaled dimensions
Solution Approach 2:
Aluminum acts as an intermediary substance between the gate dielectric and the work function metal layer. The aluminum treatment creates intermediate surface properties on the gate dielectric that facilitate better fluorine retention in the overlying work function metal layer, resolving the contradiction between scaling and fluorine stability
2Manufacturing precision
If fluorine is retained in the work function metal layer to improve flatband voltage, then threshold voltage control is enhanced, but the process complexity increases due to additional aluminum and fluorine treatments
Solution Approach 1:
The aluminum treatment and fluorine treatment are combined into a integrated process sequence that modifies the gate dielectric surface and subsequently deposits the work function metal layer with improved fluorine retention in a coordinated manner, achieving precise flatband voltage control while managing process complexity through systematic integration
3Reliability
If the gate dielectric is treated with aluminum to enhance fluorine diffusion, then fluorine retention improves, but the additional process step increases manufacturing complexity
Solution Approach 1:
The aluminum treatment is performed as a preliminary step before work function metal layer deposition, preparing the gate dielectric surface to enhance fluorine retention. This preliminary modification enables improved fluorine diffusion and retention characteristics without requiring complex post-processing steps
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 enhances the performance of transistors by increasing flatband voltage towards the band edge of the metal layer and reducing the threshold voltage, leading to improved device performance.
Implementation Method 1
enhance the diffusion of fluorine into the gate dielectric
Implementation Method 2
performing a fluorine treatment on the first conductive material
Data Source
AI summary
In some embodiments, a method includes forming a plurality of nanostructures over a substrate; etching the plurality of nanostructures to form first recesses; forming source/drain regions in the first recesses; removing first nanostructures of the plurality of nanostructures leaving second nanostructures of the plurality of nanostructures; depositing a gate dielectric over and around the second nanostructures; performing an aluminum treatment on the gate dielectric; depositing a first conductive material over and around the gate dielectric; performing a fluorine treatment on the first conductive material; and depositing a second conductive material over and around the first conductive material.