Cu Interconnects Using Cu Intermetallic Barriers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As copper (Cu) interconnects scale, issues arise with increased resistance due to smaller cross-sectional area, grain boundary and surface scattering, diffusion barrier integrity, electromigration, and adhesion problems, particularly in narrow lines and vias, where existing solutions like self-forming embedded diffusion barriers are insufficient.
Innovation Solution
The use of Cu intermetallics to form liners, electromigration barriers, and caps by depositing a metal layer that reacts with Cu to form a Cu intermetallic barrier and liner, and optionally a nitride bilayer, which are then annealed to enhance adhesion, prevent electromigration, and limit Cu diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If liner thickness is reduced to maintain volume in narrow lines, then Cu volume is limited, but diffusion barrier integrity deteriorates and metals diffuse into dielectric
Solution Approach 1:
The patent uses a composite liner structure consisting of a first liner material layer (e.g., Ta, W, or Mo) and a second liner material layer (e.g., Ru, Rh, or Ir). This composite structure provides superior diffusion barrier integrity compared to single-material liners, preventing metal diffusion into the dielectric while accommodating the reduced thickness requirements for narrow interconnect lines.
2Productivity
If line area is reduced for scaling, then resistance increases due to smaller cross-sectional area, but electromigration resistance worsens due to increased current density
Solution Approach 1:
The patent applies different material compositions and thicknesses at different locations within the interconnect structure. The liner materials are strategically selected and positioned to provide enhanced electromigration resistance at critical interfaces, while the overall line dimensions are optimized for scaling. This local optimization allows the structure to maintain reliability even as overall line area is reduced.
3Quantity of substance
If liner thickness is reduced at bottom of vias, then volume is saved, but adhesion between levels deteriorates
Solution Approach 1:
The patent employs a composite liner structure with specific material combinations (e.g., Ta/Ru, W/Rh, or Mo/Ir) that provide superior adhesion properties. The first liner material layer offers strong bonding to the underlying structure, while the second liner material layer provides additional adhesion enhancement and diffusion barrier functionality, ensuring robust adhesion between interconnect levels even with reduced overall liner thickness.
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 Cu intermetallic barriers and liners improve the reliability of Cu interconnects by reducing electromigration, enhancing adhesion, and preventing crack propagation, while maintaining conductivity and preventing Cu diffusion into dielectrics.
Implementation Method 1
annealing the metal layer and the Cu line under conditions sufficient to form a Cu intermetallic barrier at the bottom of the via
Implementation Method 2
annealing the metal layer and the Cu line under conditions sufficient to form a Cu intermetallic barrier
Data Source
AI summary
Techniques for improving reliability in Cu interconnects using Cu intermetallics are provided. In one aspect, a method of forming a Cu interconnect in a dielectric over a Cu line includes the steps of: forming at least one via in the dielectric over the Cu line; depositing a metal layer onto the dielectric and lining the via such that the metal layer is in contact with the Cu line at the bottom of the via, wherein the metal layer comprises at least one metal that can react with Cu to form a Cu intermetallic; annealing the metal layer and the Cu line under conditions sufficient to form a Cu intermetallic barrier at the bottom of the via; and plating Cu into the via to form the Cu interconnect, wherein the Cu interconnect is separated from the Cu line by the Cu intermetallic barrier. A device structure is also provided.