Semiconductor Gate Stack With Alternating Work Function Layers
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Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, the integration density of electronic components increases, but this leads to challenges in forming gate structures with precise work function layers that can be tuned for optimal performance, particularly in planar FET devices, FinFETs, and gate-all-around transistors.
Innovation Solution
The formation of a gate structure with a work function layer composed of alternating layers of two different metal nitride materials, such as TiN and TaN, allows for tuning the work function by adjusting the ratio of these metals, enabling precise control over the electrical properties of the gate stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature size is reduced to increase integration density, then more components can be integrated into a given area, but manufacturing precision and control of work function layers become more difficult
Solution Approach 1:
The work function layer is segmented into multiple sub-layers with different metal nitride materials (e.g., TiN, TaN, WN) stacked in sequence. Each sub-layer contributes differently to the overall work function, allowing precise tuning of the gate electrode's electrical properties. This segmentation enables independent optimization of each layer's thickness and composition to achieve the desired work function value despite reduced feature sizes.
Solution Approach 2:
The work function is tuned by changing the parameters of the multi-layer structure, specifically the thickness and material composition of each metal nitride sub-layer. By adjusting the ratio and thickness of different metal nitride materials, the overall work function can be precisely controlled to match the required specifications for high-performance transistors with reduced feature sizes.
2Reliability
If work function is tuned for optimal device performance, then device performance is improved, but device complexity increases
Solution Approach 1:
The gate electrode uses a composite structure of multiple metal nitride materials (TiN, TaN, WN, etc.) stacked together. Each material brings specific properties such as different work function values, etch selectivity, and stability characteristics. This composite approach allows tuning the overall work function while maintaining manufacturing compatibility and device performance, balancing the trade-off between performance optimization and structural complexity.
Data Source
AI summary
A semiconductor device and a method of forming the same are provided. The semiconductor device includes a gate stack over an active region of a substrate. The gate stack includes a gate dielectric layer and a first work function layer over the gate dielectric layer. The first work function layer includes a plurality of first layers and a plurality of second layers arranged in an alternating manner over the gate dielectric layer. The plurality of first layers include a first material. The plurality of second layers include a second material different from the first material.