Self-Aligned Manganese Silicate Barriers for Copper Interconnects
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Solution Overview
Problem
Copper interconnections in microelectronic devices face issues with electromigration, diffusion, and adhesion, leading to increased electrical resistance and short lifetimes due to the use of existing diffusion barriers like SiC, Si3N4, and manganese oxide layers, which have limitations in effectiveness and reliability.
Innovation Solution
A process involving the conformal chemical vapor deposition of metals like manganese, chromium, or vanadium on insulators to form self-aligned diffusion barriers that react with the insulator to create strongly adherent and conductive manganese silicate and manganese nitride layers, preventing copper diffusion and enhancing adhesion without leaving metallic impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SiC or Si3N4 is used to cover the top of copper wiring, then the copper is protected against electromigration, but the dielectric constant increases leading to higher capacitance and decreased signal transmission speed
Solution Approach 1:
The patent applies different materials to different locations: Ta is used on the bottom and sides of copper interconnections for electromigration protection, while SiC or Si3N4 is used only on the top surface. This local differentiation allows electromigration protection where needed without the penalty of increased dielectric constant throughout the entire insulator structure.
Solution Approach 2:
The diffusion barrier is segmented into multiple materials placed at different locations. The Ta barrier is confined to specific regions (bottom and sides) while other materials cover different areas, allowing each material to perform its optimal function without the drawbacks of using a single material throughout.
2Manufacturing precision
If electroless deposition of CoWP or CoWB alloy is used on top of copper wires, then self-aligned diffusion barrier is formed, but breakdown of selectivity causes electrical shorts over insulators between Cu wires
Solution Approach 1:
The patent introduces a new material (Mn, Cr, or V) as an intermediary that reacts with the insulator to form a diffusion barrier. This intermediary approach replaces the problematic electroless deposition process with a controlled reaction process that forms MnSixOy or similar barriers, eliminating the selectivity breakdown issue while maintaining self-alignment.
Solution Approach 2:
The patent changes the formation mechanism from electroless deposition (chemical reduction) to controlled diffusion reactions. By changing the parameter of how the barrier is formed—from depositing an alloy to reacting a metal with the insulator—the process achieves reliable self-alignment without electrical shorts.
3Reliability
If CoWP or CoWB alloy barrier is used on copper surfaces, then diffusion barrier is formed, but the alloy remains on parts contacted by Cu-filled vias increasing electrical resistance
Solution Approach 1:
The patent extracts the problematic alloy material and replaces it with a pure metal (Mn, Cr, or V) that reacts with the insulator. The reaction product (MnSixOy) forms the diffusion barrier without leaving conductive alloy residues on the copper surfaces that would increase resistance at via contacts.
Solution Approach 2:
The patent uses a consumable metal layer (Mn, Cr, or V) that is intentionally deposited and then consumed through reaction with the insulator. This disposable approach ensures complete reaction without residual alloy material that would harm electrical conductivity, unlike the persistent CoWP or CoWB alloy layers.
4Reliability
If Mn is diffused to form MnSixOy layer on insulator, then diffusion barrier is created, but Mn impurity remains in Cu during anneal restricting grain growth and increasing resistance
Solution Approach 1:
The patent applies excessive Mn deposition to ensure complete reaction with the insulator. By depositing more Mn than strictly necessary, the process ensures that all Mn reacts to form the MnSixOy barrier layer, leaving no residual Mn impurity in the copper that would restrict grain growth or increase resistance.
Solution Approach 2:
The patent performs the Mn deposition and reaction process before copper filling and final annealing. This preliminary action ensures the diffusion barrier is fully formed and stabilized before the copper is introduced, preventing any Mn-Cu interaction that would create harmful impurities during subsequent processing.
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 process results in highly conductive, durable, and strongly adherent copper layers with improved resistance to electromigration and increased adhesion, effectively extending the lifetime of copper interconnections and maintaining signal transmission speed.
Implementation Method 1
conformal chemical vapor deposition of metals like manganese, chromium, or vanadium on insulators to form self-aligned diffusion barriers that react with the insulator
Implementation Method 2
reacting at least a part of the deposited metal with the insulating film to form a barrier layer
Data Source
AI summary
An interconnect structure for integrated circuits incorporates manganese silicate and manganese silicon nitride layers that completely surrounds copper wires in integrated circuits and methods for making the same are provided. The manganese silicate forms a barrier against copper diffusing out of the wires, thereby protecting the insulator from premature breakdown, and protecting transistors from degradation by copper. The manganese silicate and manganese silicon nitride also promote strong adhesion between copper and insulators, thus preserving the mechanical integrity of the devices during manufacture and use. The strong adhesion at the copper-manganese silicate and manganese silicon nitride interfaces also protect against failure by electromigration of the copper during use of the devices. The manganese-containing sheath also protects the copper from corrosion by oxygen or water from its surroundings.