Selective Self-Assembled Monolayer Diffusion Barrier for Copper Interconnects
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Solution Overview
Problem
Current diffusion barrier layers in copper damascene interconnects are ineffective at sub-100 nm feature sizes due to thickness limitations and poor adhesion, leading to increased leakage currents and inferior device performance.
Innovation Solution
A method involving the selective deposition of a releasable self-assembled monolayer (SAM-1) on copper surfaces followed by a permanent SAM-2 on dielectric surfaces, with subsequent heating to remove SAM-1, creating a thin, effective copper diffusion barrier while maintaining good copper-to-copper contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional metal deposition methods (PVD or CVD) are used to deposit thin barrier layers, then the barrier layer thickness can be reduced below 5 nm, but the step coverage and conformality in high-aspect-ratio features deteriorate
Solution Approach 1:
The patent replaces conventional mechanical deposition methods (PVD/CVD) with a chemical self-assembly process. Molecules spontaneously organize into monolayers on surfaces through chemical bonding, eliminating the need for complex deposition equipment and enabling atomic-level thickness control without compromising conformality in high-aspect-ratio features.
Solution Approach 2:
The invention changes the fundamental parameter of barrier layer formation from physical deposition to chemical self-assembly. By using molecules that spontaneously form monolayers through chemical bonding, the process achieves sub-5 nm thickness with perfect conformality, as the molecular self-assembly mechanism inherently adapts to any surface geometry.
2Reliability
If thick diffusion barrier layers are used, then copper diffusion into dielectrics is prevented, but the volume available for low-resistivity Cu is reduced
Solution Approach 1:
The patent employs ultra-thin self-assembled monolayer films as diffusion barriers. These molecularly thin films (single-layer thickness) provide effective copper diffusion prevention while occupying minimal volume, thereby maximizing the space available for low-resistivity copper interconnects compared to conventional thick barrier layers.
Solution Approach 2:
The invention fundamentally changes the barrier layer thickness parameter from nanometer-scale (conventional) to molecular-scale (sub-nanometer). This parameter reduction achieves the same diffusion prevention function while minimizing volume occupation, allowing more space for copper interconnects.
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
This approach enhances electrical and reliability characteristics by preventing copper diffusion into dielectrics, ensuring robust electrical connections and reducing electromigration, thus improving the performance of dual damascene structures.
Implementation Method 1
depositing a first releasable self-assembled monolayer (SAM-1) to a copper containing surface
Implementation Method 2
selectively depositing a first self-assembled monolayer on the copper surface
Implementation Method 3
depositing a second permanent self-assembled monolayer (SAM-2) to the non-copper containing parts of said surface
Implementation Method 4
selectively depositing a second self-assembled monolayer on the dielectric surface
Implementation Method 5
heating said substrate to remove the first self-assembled monolayer
Data Source
AI summary
A method for selective deposition of self-assembled monolayers to the surface of a substrate for use as a diffusion barrier layer in interconnect structures is provided comprising the steps of depositing a first self-assembled monolayer to said surface, depositing a second self-assembled monolayer to the non-covered parts of said surface and subsequently heating said substrate to remove the first self-assembled monolayer. The method of selective deposition of self-assembled monolayers is applied for the use as diffusion barrier layers in a (dual) damascene structure for integrated circuits.