Tungsten Via Stack for MRAM Copper Diffusion Control
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Solution Overview
Problem
Copper used in back-end-of-line (BEOL) interconnects for magnetoresistive random-access memory (MRAM) is prone to high electromigration and diffusion into insulating layers, leading to performance degradation and damage.
Innovation Solution
A tungsten via is used between the lower magnetic layer of the MRAM and the copper interconnect, with additional tantalum nitride layers and an adhesion layer to prevent copper diffusion, corrosion, and peeling, while reducing resistivity and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used in BEOL interconnects for MRAM, then electrical conductivity is improved, but electromigration and diffusion into insulating layers occur causing performance degradation
Solution Approach 1:
A tungsten via is introduced as an intermediary material between the copper interconnect and the lower magnetic layer of the MRAM. The tungsten via physically separates the copper from the magnetic layer, preventing copper diffusion while maintaining electrical conductivity. Additional tantalum nitride layers are deposited on the copper interconnect surface before the tungsten via to further prevent copper electromigration and diffusion.
Solution Approach 2:
The interconnect structure is transformed from a simple copper interconnect to a composite structure consisting of multiple layers: copper interconnect, tantalum nitride barrier layers, tungsten via, and additional tantalum nitride layers. This composite structure combines the high conductivity of copper with the protective properties of tantalum nitride and tungsten, resolving the contradiction between conductivity and reliability.
2Reliability
If tungsten via is used to prevent copper diffusion, then reliability is improved, but manufacturing complexity increases due to additional layers
Solution Approach 1:
The via structure is segmented into multiple functional layers: a first tungsten via layer, first and second tantalum nitride barrier layers, and an adhesion layer. Each segment performs a specific function (electrical conduction, diffusion barrier, adhesion), allowing the complex structure to be manufactured through sequential deposition processes that are standard in semiconductor fabrication.
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 solution provides lower resistivity and prevents copper electromigration and fluorine corrosion, enhancing the reliability and performance of the MRAM by reducing copper intermixing and stress on the tungsten layer.
Implementation Method 1
Copper used in back-end-of-line (BEOL) interconnects for magnetoresistive random-access memory (MRAM) is prone to high electromigration and diffusion into insulating layers
Implementation Method 2
A tungsten via is used between the lower magnetic layer of the MRAM and the copper interconnect, with additional tantalum nitride layers and an adhesion layer to prevent copper diffusion, corrosion, and peeling
Implementation Method 3
a via comprising, one or more tantalum nitride layers disposed on an upper surface of the copper interconnect an adhesion layer disposed on an upper surface of the one or more tantalum nitride layers
Data Source
AI summary
One or more semiconductor processing tools may deposit one or more tantalum nitride layers on an upper surface of a copper interconnect and within a via. The one or more semiconductor processing tools may deposit an adhesion layer on an upper surface of the one or more tantalum nitride layers and within the via. The one or more semiconductor processing tools may deposit tungsten on an upper surface of the adhesion layer and within the via for via i