Gate Barrier Layer Structure for Uniform Work Function Metal Deposition
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Solution Overview
Problem
As semiconductor devices undergo miniaturization, issues such as metal migration between gate stacks and uneven work function metal layer thicknesses lead to device defects and performance degradation, particularly in NMOS and PMOS regions.
Innovation Solution
Incorporating a barrier layer between the work function metal layer and the fill material in the gate electrode to prevent metal migration and ensure even thickness of work function metal layers, using materials like silicon, silicon oxide, tantalum nitride, or tungsten carbonitride depending on the region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate electrode structures are formed without a barrier layer in miniaturized semiconductor devices, then manufacturing process is simpler, but metal migration occurs between gate stacks causing device defects
Solution Approach 1:
A barrier layer is introduced as an intermediary component between the work function metal layer and the fill material in the gate electrode. This barrier layer specifically prevents metal migration from the work function metal layer to the fill material and to adjacent gate stacks, thereby resolving the metal migration issue without requiring fundamental changes to the gate electrode structure
Solution Approach 2:
The gate electrode is segmented into distinct functional layers: a work function metal layer for electrical function, a barrier layer for migration prevention, and a fill material for structural completion. This segmentation allows each layer to perform its specific function independently, preventing metal migration while maintaining manufacturing feasibility
2Manufacturing precision
If work function metal layer thickness is not controlled evenly across different regions, then deposition process is faster, but device performance degrades due to uneven thickness
Solution Approach 1:
Different barrier layer materials are used in different regional contexts (NMOS regions versus PMOS regions) to optimize local properties. The barrier layer material is selected based on compatibility requirements with adjacent structures in each region, ensuring uniform work function metal layer deposition while maintaining regional-specific performance characteristics
Data Source
AI summary
A semiconductor device including a barrier layer surrounding a work function metal layer and methods of forming the same are disclosed. In an embodiment, a semiconductor device includes a semiconductor substrate; a first channel region over the semiconductor substrate; a second channel region over the first channel region; gate dielectric layers surrounding the first channel region and the second channel region; work function metal layers surrounding the gate dielectric layers; and barrier layers surrounding the work function metal layers, a first barrier layer surrounding the first channel region being merged with a second barrier layer surrounding the second channel region.