GAA Gate Electrode Capping Structure for Threshold Voltage Tuning
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Solution Overview
Problem
Semiconductor devices, particularly gate-all-around type transistors, face challenges in adjusting threshold voltage due to limitations in reducing the thickness of work function layers, which complicates high integration and multi-functionality requirements.
Innovation Solution
A semiconductor device design incorporating a capping pattern composed of a double layer of metal nitride layers, where the first layer has a lower work function and the second layer has a higher work function, preventing dopant diffusion and allowing for reduced threshold voltage without altering the thickness of the work function control layer, achieved by controlling the concentration and thickness of the first metal nitride layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of the work function layer is reduced to adjust threshold voltage, then the threshold voltage can be tuned, but the structural integrity and control precision of the gate-all-around transistor deteriorate
Solution Approach 1:
The gate electrode is segmented into multiple functional layers: a work function control layer (first metal nitride) for threshold voltage adjustment, a barrier layer (second metal nitride) to prevent dopant diffusion, and an electrode layer for electrical connection. This segmentation allows each layer to perform its specific function independently, enabling threshold voltage tuning without compromising the integrity of the work function control layer.
Solution Approach 2:
The gate electrode uses a composite structure combining different metal nitride materials with distinct properties. The first metal nitride (e.g., TiN) provides work function control, while the second metal nitride (e.g., TaN or WN) provides barrier functionality. This composite material approach allows simultaneous optimization of threshold voltage control and structural stability.
2Device complexity
If a single layer work function control structure is used, then the structure is simple, but the ability to prevent dopant diffusion and control threshold voltage independently is limited
Solution Approach 1:
The gate electrode is divided into functionally distinct layers: the work function control layer for threshold voltage adjustment and the barrier layer for dopant diffusion prevention. This segmentation enables independent control of each function, allowing versatile threshold voltage adjustment without compromising structural simplicity.
Solution Approach 2:
The multi-layer gate electrode structure provides universal functionality by combining threshold voltage control, dopant diffusion barrier, and electrical conduction in a single integrated component. This multi-functional design enhances adaptability for different transistor types (nMOS, pMOS) and applications while maintaining a relatively simple overall structure.
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 design effectively decreases the threshold voltage of transistors, enabling high integration and multi-functionality while maintaining the integrity of the work function control layer, thereby enhancing the performance and reliability of semiconductor devices.
Implementation Method 1
The first metal nitride layer may be disposed between the second metal nitride layer and the plurality of semiconductor patterns
Data Source
AI summary
A semiconductor device includes a plurality of semiconductor patterns that are sequentially stacked and spaced apart from each other on a substrate, and a gate electrode on the plurality of semiconductor patterns. The gate electrode includes a capping pattern and a work function pattern that are sequentially stacked on the plurality of semiconductor patterns. The capping pattern includes a first metal nitride layer including a first metal element, and a second metal nitride layer including a second metal element whose work function is greater than a work function of the first metal element. The first metal nitride layer is disposed between the second metal nitride layer and the plurality of semiconductor patterns. The first metal nitride layer is thinner than the second metal nitride layer.