FinFET Gate Work Function Tuning via Metal-Oxide Layering
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Solution Overview
Problem
Current FinFET architectures face challenges in adjusting threshold voltages due to limitations in ion implantation, which is not effective for scaling down metal oxide semiconductor transistors, and polysilicon gates suffer from boron penetration and depletion effects that reduce gate capacitance.
Innovation Solution
A method involving the formation of a semiconductor device with a substrate, a high-k dielectric layer, and alternating layers of work function metal and oxygen-containing layers, such as TiN and TiON, to adjust work function values and achieve different threshold voltages by varying the nitrogen to titanium ratio in the work function layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ion implantation is used to adjust threshold voltage, then threshold voltage can be adjusted in conventional planar MOS transistors, but it becomes ineffective for scaling down metal oxide semiconductor transistors and cannot easily adjust threshold voltages in FinFET
Solution Approach 1:
The patent changes the physical and chemical parameters of the gate electrode by forming alternating layers of metal and metal oxide with different stoichiometric ratios. By adjusting the oxygen content and layer thicknesses, the work function and threshold voltage can be precisely tuned without relying on ion implantation, thereby maintaining adaptability in scaled-down FinFET devices while improving fabrication efficiency through a more controllable process
Solution Approach 2:
The patent employs composite gate electrode structures consisting of multiple alternating layers of metal and metal oxide materials. This composite structure enables independent optimization of each layer's properties, providing enhanced versatility in threshold voltage adjustment and eliminating the limitations of conventional ion implantation in scaled devices
2Ease of manufacture
If polysilicon gate is used, then gate electrode can be formed, but boron penetration and depletion effect occur which reduce gate capacitance and worsen driving force
Solution Approach 1:
The patent extracts the problematic polysilicon material and replaces it with metal and metal oxide layers. This elimination removes the source of boron penetration and depletion effects, thereby improving gate capacitance and driving force while maintaining ease of manufacture through standard thin-film deposition techniques
Solution Approach 2:
The patent changes the material parameters from polysilicon to metal/metal oxide composites, fundamentally altering the electrical characteristics. This parameter change eliminates boron-related issues and depletion effects, improving reliability while maintaining manufacturability through established deposition processes
3Reliability
If work function metals are used with high-K gate dielectric layers, then polysilicon gate problems can be replaced, but threshold voltage adjustment becomes difficult in FinFET architecture
Solution Approach 1:
The patent segments the gate electrode into multiple alternating layers of metal and metal oxide. This segmentation allows independent control of each layer's thickness and composition, providing versatile threshold voltage tuning capability in FinFET while maintaining the reliability benefits of work function metals with high-k dielectric layers
Solution Approach 2:
The patent introduces dynamic adjustability by varying the stoichiometric ratios and thicknesses of metal oxide layers. This dynamic control mechanism enables precise threshold voltage tuning in FinFET architecture while preserving the excellent electrical characteristics of metal gate/high-k dielectric combinations
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 allows for precise adjustment of threshold voltages in FinFETs, enhancing device performance by overcoming the limitations of ion implantation and polysilicon gate issues, thereby improving the driving force and capacitance of the transistors.
Implementation Method 1
forming a first oxygen-containing layer on the first work function layer
Data Source
AI summary
A method for fabricating semiconductor device is disclosed. The method includes the steps of: providing a substrate having a high-k dielectric layer thereon; forming a first work function layer on the high-k dielectric layer; and forming a first oxygen-containing layer on the first work function layer.