Semiconductor Gate Stack With Alternating Metal Nitride 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 optimal work function layers that can be tuned for specific device requirements, particularly in planar FET devices, FinFETs, and gate-all-around transistors.
Innovation Solution
The formation of a gate structure with a work function layer comprising alternating layers of different metal nitrides, 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 forming gate structures with optimal work function layers becomes more difficult
Solution Approach 1:
The work function layer is segmented into multiple alternating layers of different metal nitrides (e.g., TiN and TaN), allowing independent control of each layer's thickness to tune the overall work function while maintaining compatibility with scaled device dimensions
Solution Approach 2:
The gate structure employs composite material layers combining different metal nitrides, where the work function can be precisely controlled by adjusting the thickness ratio of constituent materials, enabling optimal electrical properties at reduced feature sizes
2Ease of manufacture
If a single metal nitride layer is used, then the manufacturing process is simple, but the work function cannot be precisely tuned for specific device requirements
Solution Approach 1:
The work function is tuned by changing the physical parameter of layer thickness for each metal nitride component. By adjusting the relative thicknesses of TiN and TaN layers, the composite work function can be precisely controlled to match specific device requirements while using standard deposition processes
Solution Approach 2:
A composite structure of alternating metal nitride layers is used, where each material contributes differently to the overall work function. This composite approach enables continuous tuning of the work function value by varying the thickness ratio of constituent layers, providing versatility without requiring entirely different materials or processes
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.