FinFET Hybrid Work Function Layers for Selective Etch Tuning
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Solution Overview
Problem
Current FinFET devices face challenges in forming flexible and tunable work function layers, as existing methods lack precision in removing target materials without affecting other layers, limiting the flexibility in transistor design and performance.
Innovation Solution
The use of selective wet etch processes and deposition methods allows for the formation of hybrid work function layer stacks with multiple layers using different materials, enabling precise control over work function layers and independent tuning of threshold voltages in FinFET devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional work function layer formation methods are used, then the process is simple, but the flexibility and tunability of work function layers are limited
Solution Approach 1:
The work function layer is divided into multiple distinct layers (first work function layer, second work function layer, third work function layer) with different materials and functions. Each layer can be independently formed, tuned, and optimized, providing enhanced flexibility in transistor design while maintaining manageable process complexity through systematic segmentation of the formation steps.
Solution Approach 2:
The patent employs a composite work function layer stack consisting of different materials (e.g., titanium nitride, tantalum nitride, tungsten, molybdenum) combined in specific configurations. This composite structure enables independent tuning of threshold voltages and work functions by selecting appropriate material combinations and thicknesses for each layer, significantly improving design flexibility.
2Manufacturing precision
If selective wet etch processes are used to remove target materials, then precision in removing only target materials is improved, but the process complexity increases
Solution Approach 1:
The patent introduces selectively removable intermediate layers (such as aluminum oxide or silicon nitride) between the work function layers and other structures. These intermediary layers serve as sacrificial elements that can be selectively removed using specific wet etch processes, enabling precise exposure and removal of target materials without affecting surrounding layers, thereby achieving high manufacturing precision.
Solution Approach 2:
The patent utilizes parameter changes in the etch process, including selective etchants with different chemistries and conditions tailored for specific materials. By adjusting etch parameters (etchant composition, temperature, time) to match the specific target material, the process achieves high precision in removing only the intended layer while leaving other materials intact, despite the increased process complexity.
3Adaptability or versatility
If multiple work function layers with different materials are formed, then the tunability of threshold voltages is improved, but the manufacturing complexity increases
Solution Approach 1:
The formation process is segmented into distinct sequential steps for depositing each work function layer (first, second, and third layers) with different materials. This segmentation allows each layer to be independently optimized and formed using appropriate deposition techniques, enabling precise threshold voltage tuning while maintaining systematic and manageable manufacturing processes.
Solution Approach 2:
Different regions of the device can have different work function layer configurations by selectively forming or removing specific layers in different areas. This local quality approach allows independent tuning of threshold voltages for different transistors or device regions using the same base structure, enhancing versatility without requiring entirely different manufacturing processes for each configuration.
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 flexibility in transistor design, allowing for different combinations of work function layers and improved performance by enabling precise removal and deposition of layers, even in narrow gate trenches, which is crucial for advanced processing nodes.
Implementation Method 1
The use of selective wet etch processes and deposition methods allows for the formation of hybrid work function layer stacks with multiple layers using different materials
Implementation Method 2
The use of selective wet etch processes and deposition methods allows for the formation of hybrid work function layer stacks
Data Source
AI summary
A semiconductor device includes a first fin, a second fin, and a third fin protruding above a substrate, where the third fin is between the first fin and the second fin; a gate dielectric layer over the first fin, the second fin, and the third fin; a first work function layer over and contacting the gate dielectric layer, where the first work function layer extends along first sidewalls and a first upper surface of the first fin; a second work function layer over and contacting the gate dielectric layer, where the second work function layer extends along second sidewalls and a second upper surface of the second fin, where the first work function layer and the second work function layer comprise different materials; and a first gate electrode over the first fin, a second gate electrode over the second fin, and a third gate electrode over the third fin.