Nitridized Metal Barrier for Semiconductor Interconnect Adhesion
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Solution Overview
Problem
Current barrier metals in semiconductor interconnects, such as chromium, tantalum, and titanium, do not adhere well to dielectric materials, leading to poor adhesion and increased electromigration of copper atoms, which results in defects and performance issues in copper interconnect structures.
Innovation Solution
A nitrogen-enriched surface is created on the dielectric material using molecular modification, allowing a non-nitridized metal layer to nitridize upon adhesion, thereby strengthening the metal/dielectric interface and improving adhesion and reducing electromigration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If typical barrier metals (e.g., chromium, tantalum, titanium, tungsten) are used to prevent copper diffusion, then copper contamination is mitigated, but adhesion to dielectric materials is poor
Solution Approach 1:
The patent creates a composite barrier metal structure consisting of a first barrier metal layer (e.g., chromium) and a second barrier metal layer (e.g., tantalum, titanium, or tungsten). This composite structure combines the excellent adhesion properties of chromium with the superior copper diffusion barrier properties of the second metal, resolving the contradiction between adhesion strength and diffusion prevention.
Solution Approach 2:
The patent applies a preliminary adhesion promotion treatment to the dielectric surface before depositing the barrier metal layers. This preliminary action enhances the surface properties of the dielectric, improving the adhesion of the first barrier metal layer to the dielectric material, which subsequently supports the second barrier metal layer.
2Reliability
If copper interconnect structures are scaled down to reduce resistance, then conduction performance is improved, but current density increases exponentially leading to increased electromigration
Solution Approach 1:
The composite barrier metal structure provides enhanced protection against electromigration by combining two metals with complementary properties. The first barrier metal layer adheres strongly to the dielectric, while the second layer provides superior diffusion barrier properties, together preventing copper atom migration even at high current densities in scaled-down interconnects.
Solution Approach 2:
The patent changes the structural parameters of the barrier metal from a single-layer configuration to a multi-layer composite configuration. This parameter change enhances the barrier effectiveness against electromigration without significantly increasing the overall thickness, allowing the interconnect structure to withstand higher current densities.
3Device complexity
If a single-layer barrier metal is used to simplify the structure, then device complexity is reduced, but adhesion and electromigration resistance are insufficient
Solution Approach 1:
The patent employs a composite barrier metal structure with two distinct layers, each optimized for specific functions. The first layer prioritizes adhesion to the dielectric, while the second layer prioritizes copper diffusion barrier properties. This functional division resolves the contradiction between structural simplicity and performance requirements.
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 nitridized metal layer enhances the adhesion between the metal and dielectric, reducing electromigration and improving the electrical performance of the interconnects by providing a stronger interface that withstands manufacturing processes and environmental exposure.
Implementation Method 1
At least a portion of a surface of the substrate is molecularly modified to convert at least a portion of the surface of the substrate to a nitrogen-enriched surface
Implementation Method 2
A metal layer is deposited on the molecularly modified surface of the substrate interacting with the molecularly modified surface to form a nitridized metal layer
Data Source
AI summary
A method for fabricating a semiconductor structure includes the following steps. A substrate including a dielectric material is formed. A surface of the substrate is molecularly modified to convert the surface of the substrate to a nitrogen-enriched surface. A metal layer is deposited on the molecularly modified surface of the substrate interacting with the molecularly modified surface to form a nitridized metal layer.