Copper Interconnect Capping Layers for Electromigration Resistance
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Solution Overview
Problem
As integrated circuit (IC) devices miniaturize, electromigration failures increase due to poor adhesion between copper interconnects and dielectric diffusion barrier layers, primarily caused by weak copper oxide bonds and inadequate interfacial bonding energy, leading to reliability issues at the 45 nm technology node and beyond.
Innovation Solution
A method involving the formation of a capping layer on copper lines using a metal-containing precursor and silicon-containing precursor, which improves adhesion of a subsequently deposited barrier layer by creating a metal or metal-containing compound layer that enhances the bonding between copper and dielectric materials, thereby reducing electromigration and resistance shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin layer of dielectric diffusion barrier material (silicon carbide or silicon nitride) is deposited to prevent metal diffusion, then diffusion prevention is improved, but adhesion between the barrier layer and copper is insufficient leading to electromigration failures
Solution Approach 1:
A self-aligned buffer layer comprising silicon and copper silicide is formed at the interface between the copper interconnect and the dielectric diffusion barrier layer. This buffer layer acts as an intermediary that significantly improves adhesion between the barrier layer and copper, preventing electromigration failures while maintaining effective diffusion prevention.
Solution Approach 2:
The buffer layer is formed as a composite structure containing both silicon and copper silicide phases. This composite material provides superior adhesion properties compared to either pure silicon or pure copper, while also maintaining compatibility with the dielectric diffusion barrier layer.
2Productivity
If copper interconnect dimensions are reduced to enable IC miniaturization, then device integration is improved, but electromigration failures increase due to poor adhesion
Solution Approach 1:
The self-aligned buffer layer serves as a mediator that enables reliable copper interconnects at reduced dimensions. By improving the adhesion between copper and the dielectric barrier layer, the buffer layer prevents electromigration failures that would otherwise occur in miniaturized interconnect structures.
3Strength
If the copper surface is treated to improve adhesion, then bonding energy is improved, but copper oxide formation may occur reducing reliability
Solution Approach 1:
The buffer layer is formed using a self-aligned process that occurs in-situ before the copper interconnect is exposed to environments where oxidation could occur. This preliminary formation of the silicon-containing buffer layer protects the copper surface and prevents oxide formation while establishing strong adhesion.
Solution Approach 2:
The silicon-containing buffer layer acts as an intermediary that prevents direct contact between copper and oxidizing environments. This protective interface maintains strong adhesion while preventing copper oxide formation that would degrade reliability.
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 described method significantly improves the adhesion energy between copper and dielectric barrier layers, reducing electromigration failures and maintaining low resistance in copper lines, with the capping sequence minimizing resistance shifts to less than about 1% and enhancing the reliability of interconnects.
Implementation Method 1
exposing the Cu surface first to a metal containing precursor to form an atomic layer of adsorbed precursor or metal atoms
Implementation Method 2
delivering a silicon-containing precursor to the reaction chamber; and forming the capping layer on the metal line by allowing at least a portion of the silicon-containing precursor to interact with the exposed surface of the metal line and/or interact with the metal-containing precursor or a first metal
Data Source
AI summary
Disclosed methods cap exposed surfaces of copper lines with a layer of metal or metal-containing compound combined with silicon. In some cases, the metal or metal-containing compound forms an atomic layer. In certain embodiments, the methods involve exposing the copper surface first to a metal containing precursor to form an atomic layer of adsorbed precursor or metal atoms, which may optionally be converted to an oxide, nitride, carbide, or the like by, e.g., a pinning treatment. Subsequent exposure to a silicon-containing precursor may proceed with or without metallic atoms being converted.