Ruthenium-Doped Cobalt Seed Layer for Void-Free Gap Fill
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Solution Overview
Problem
As microelectronic devices shrink, traditional copper plating processes face challenges in achieving void-free fill and low resistance due to the need for thick barrier and liner layers, which become proportionally larger and increase resistance, while cobalt, a potential replacement, suffers from agglomeration issues at current processing temperatures.
Innovation Solution
Doping cobalt layers with ruthenium to reduce agglomeration, achieved through pre-deposition, co-flowing ruthenium precursors, or post-deposition exposure to ruthenium, forming a ruthenium-doped cobalt seed layer that allows for conformal coverage and low roughness, and subsequent annealing to remove impurities and reduce resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used as the barrier metal material, then electromigration resistance is improved, but cobalt agglomeration occurs at the interface between the copper barrier layer and the capping layer
Solution Approach 1:
The patent applies local quality by introducing ruthenium doping specifically at the interface region between the copper barrier layer and the capping layer. This localized modification creates a ruthenium-rich zone precisely where cobalt agglomeration occurs, providing targeted protection against agglomeration without affecting the bulk copper barrier layer's electromigration resistance properties.
Solution Approach 2:
Ruthenium acts as an intermediary element between the copper barrier layer and the capping layer. The ruthenium-doped region serves as a mediating layer that prevents direct interaction between cobalt and the copper-capping layer interface, thereby blocking the agglomeration pathway while maintaining the overall barrier structure's electromigration resistance.
2Reliability
If conventional copper barrier layers are used, then electromigration resistance is achieved, but gap-fill performance deteriorates due to cobalt agglomeration
Solution Approach 1:
The invention applies local quality by introducing ruthenium doping specifically at the interface region between the copper barrier layer and the capping layer. This localized modification creates a ruthenium-rich zone precisely where cobalt agglomeration occurs, providing targeted protection against agglomeration without affecting the bulk copper barrier layer's electromigration resistance properties.
Solution Approach 2:
Ruthenium acts as an intermediary element between the copper barrier layer and the capping layer. The ruthenium-doped region serves as a mediating layer that prevents direct interaction between cobalt and the copper-capping layer interface, thereby blocking the agglomeration pathway while maintaining the overall barrier structure's electromigration resistance.
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 ruthenium-doped cobalt process enables conformal and defect-free filling of narrow features with cobalt, reducing resistance and improving reliability by minimizing agglomeration and impurities, thus addressing the limitations of traditional copper plating and cobalt agglomeration.
Implementation Method 1
it has been discovered that gap-fill performance and via-filling can be enhanced by doping the barrier layer with ruthenium
Implementation Method 2
the ruthenium doping within the barrier layer may reduce or eliminate cobalt agglomeration at the interface between the barrier layer and the capping layer
Data Source
Figure 1
Figure 2A~2C
Figure 2D~2F
AI summary
In one implementation, a method of forming a cobalt layer on a substrate is provided. The method comprises forming a barrier and/or liner layer on a substrate having a feature definition formed in a first surface of the substrate, wherein the barrier and/or liner layer is formed on a sidewall and bottom surface of the feature definition. The method further comprises exposing the substrate to a ruthenium precursor to form a ruthenium-containing layer on the barrier and/or liner layer. The method further comprises exposing the substrate to a cobalt precursor to form a cobalt seed layer atop the ruthenium-containing layer. The method further comprises forming a bulk cobalt layer on the cobalt seed layer to fill the feature definition.