Fluorine-Treated Gate Stacks for Threshold Voltage Tuning
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Solution Overview
Problem
As the semiconductor industry continues to reduce minimum feature sizes to improve integration density, it faces challenges such as increased complexity in manufacturing processes and potential performance degradation in semiconductor devices.
Innovation Solution
The implementation of gate stacks with a fluorine-treated work function metal (WFM) layer, where a fluorine soak is performed on the WFM layer, allowing fluorine to diffuse into the underlying gate dielectric, thereby adjusting the flatband voltage and threshold voltage of the transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If minimum feature sizes are reduced to improve integration density, then more components can be integrated into a given area, but manufacturing complexity increases and device performance may degrade
Solution Approach 1:
The patent applies preliminary action by performing fluorine treatment on the work function metal layer before final gate formation. This pre-treatment modifies the metal layer's properties in advance, enabling better voltage control and reducing subsequent manufacturing complexity despite scaled dimensions. The fluorine diffusion is established beforehand to ensure proper electrical characteristics at reduced feature sizes.
Solution Approach 2:
The patent changes physical and chemical parameters of the work function metal layer by introducing fluorine through diffusion. This parameter change modifies the metal's work function and electrical properties, enabling precise control of transistor threshold voltage and flatband voltage. The fluorine concentration and distribution are carefully controlled to achieve desired electrical characteristics at reduced feature sizes.
2Area of moving object
If minimum feature sizes are reduced to improve integration density, then more components can be integrated into a given area, but device performance may degrade
Solution Approach 1:
The patent changes physical and chemical parameters of the work function metal layer by introducing fluorine through diffusion. This parameter change modifies the metal's work function and electrical properties, enabling precise control of transistor threshold voltage and flatband voltage. The fluorine concentration and distribution are carefully controlled to achieve desired electrical characteristics at reduced feature sizes.
Solution Approach 2:
The patent substitutes mechanical/physical scaling with chemical modification to maintain device performance. Instead of relying solely on dimensional scaling, the invention uses fluorine diffusion to chemically modify the work function metal layer, thereby controlling electrical properties independently of feature size. This substitution allows performance maintenance despite continued miniaturization.
3Manufacturing precision
If fluorine is diffused into the gate dielectric through the WFM layer, then flatband voltage increases towards the band edge, but the process complexity increases
Solution Approach 1:
The patent merges multiple functions into a single integrated process step. The fluorine treatment simultaneously performs work function modification, flatband voltage adjustment, and threshold voltage control in one diffusion process. This consolidation reduces overall process complexity compared to performing separate treatments for each electrical parameter adjustment.
Solution Approach 2:
The fluorine-treated work function metal layer serves multiple functions: it controls flatband voltage, adjusts threshold voltage, and maintains proper gate-electrode electrical characteristics. This multi-functionality reduces the need for additional process steps, thereby reducing overall process complexity while achieving precise voltage control.
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 device performance by increasing the flatband voltage towards the band edge of the metal, decreasing the threshold voltage, and improving overall transistor performance.
Implementation Method 1
a fluorine soak is performed on the WFM layer, allowing fluorine to diffuse into the underlying gate dielectric
Data Source
AI summary
A device includes a first nanostructure; a second nanostructure over the first nanostructure; a first high-k gate dielectric around the first nanostructure; a second high-k gate dielectric around the second nanostructure; and a gate electrode over the first and second high-k gate dielectrics. The gate electrode includes a first work function metal; a second work function metal over the first work function metal; and a first metal residue at an interface between the first work function metal and the second work function metal, wherein the first metal residue has a metal element that is different than a metal element of the first work function metal.