TiNx/TiN/TiNy Stacked Diffusion Barrier for Metal Gate
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Solution Overview
Problem
Conventional diffusion barrier layers in semiconductor devices are insufficient to prevent metal atom diffusion from metal gates into dielectric layers, which degrades transistor performance as semiconductor technology advances.
Innovation Solution
A titanium-nitride stacked layer is used as a diffusion barrier, comprising TiNx, TiN, and TiNy layers, with optional tantalum and tantalum nitride layers, to effectively suppress metal atom diffusion into the dielectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional diffusion barrier layers are used to prevent metal atom diffusion from metal gate into dielectric layer, then some diffusion protection is provided, but the barrier capability is insufficient to meet demanding requirements of advanced semiconductor devices
Solution Approach 1:
The patent employs a composite diffusion barrier layer structure consisting of multiple materials including titanium nitride (TiN), tantalum nitride (TaN), and tungsten nitride (WN) layers. Each material contributes different properties: TiN provides good adhesion and basic barrier properties, TaN offers superior diffusion resistance, and WN adds enhanced barrier capability. This composite structure achieves superior diffusion barrier capability that meets the demanding requirements of advanced semiconductor devices, resolving the contradiction between reliability and the simplicity of single-layer structures.
Solution Approach 2:
The diffusion barrier layer is segmented into multiple thin layers with different material compositions and thicknesses. The patent specifies a multi-layer structure where each layer has optimized thickness (e.g., TiN: 5-20nm, TaN: 3-10nm, WN: 2-5nm) to provide progressive diffusion resistance. This segmentation allows each layer to perform its specific function optimally while collectively providing superior barrier capability that a single thick layer cannot achieve.
2Reliability
If metal gate is formed using gate last process to prevent metallic material from affecting transistor structure, then transistor performance is improved through low resistance, but metal atom diffusion into dielectric layer degrades device performance
Solution Approach 1:
The multi-layer diffusion barrier structure acts as an intermediary between the metal gate and the dielectric layer. This intermediary structure prevents direct contact and interaction between metal atoms and the dielectric material, blocking diffusion pathways while allowing the metal gate to maintain its low-resistance electrical function. The barrier layers are designed with appropriate thickness and material properties to stop metal atom diffusion while not interfering with the electrical performance of the transistor.
Solution Approach 2:
The use of composite barrier materials (TiN, TaN, WN in specific combinations) provides enhanced diffusion protection while maintaining compatibility with the metal gate structure. Each material in the composite barrier layer contributes specific properties that collectively prevent metal atom diffusion into the dielectric layer, thereby protecting device performance while allowing the metal gate to function optimally.
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
The titanium-nitride stacked layer significantly reduces metal atom diffusion, enhancing the performance of semiconductor devices by providing superior diffusion barrier capabilities.
Implementation Method 1
a diffusion barrier layer is formed on sidewall surfaces of the gate trench to reduce diffusion of metal atoms from the metal gate into the dielectric layer
Data Source
AI summary
The present disclosure provides a semiconductor device including a metal gate structure and formation method thereof. The semiconductor device includes a substrate and a dielectric layer disposed on the substrate. The dielectric layer includes a trench. A diffusion barrier layer is disposed over a bottom surface and sidewall surfaces of the trench in the dielectric layer. The diffusion barrier layer includes at least a titanium-nitride stacked layer. The titanium-nitride stacked layer includes a TiNx layer disposed over the bottom surface and the sidewall surfaces of the trench, a TiN layer on the TiNx layer, and a TiNy layer on the TiN layer, x<1 and y>1. A metal gate is filled in the trench and disposed on the diffusion barrier layer.