Ternary Alloy Cap Layer for Copper Interconnect Etch Resistivity
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Solution Overview
Problem
Advanced integrated circuits face premature failure due to electromigration-induced material transport at the interface between copper and dielectric cap layers, particularly in high current density environments, where existing conductive cap layers like CoWP suffer from severe defects during patterning and etching processes.
Innovation Solution
The use of ternary alloys with a more noble metal species, such as nickel, instead of cobalt, in conductive cap layers to enhance etch resistivity against standard wet chemical etch recipes while maintaining superior electromigration performance, by considering the standard electrode potentials of the alloy species.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cobalt-based ternary alloy (CoWP) is used as conductive cap layer, then electromigration performance is improved, but etch resistivity deteriorates causing severe defects during patterning
Solution Approach 1:
The invention changes the electrode potential parameter of the alloy by replacing cobalt with metals having less negative standard electrode potentials (such as nickel, iron, or manganese). This parameter change transforms the alloy's chemical properties to achieve better etch resistivity while preserving the electromigration performance through careful selection of replacement metals.
Solution Approach 2:
The invention uses composite ternary alloys combining tungsten with metals having less negative standard electrode potentials (nickel, iron, or manganese) instead of cobalt. This composite material approach creates a cap layer that simultaneously provides superior electromigration resistance and enhanced etch stability during patterning processes.
2Ease of manufacture
If standard wet chemical etch recipes are used, then manufacturing process simplicity is maintained, but cap layer integrity deteriorates due to low etch resistivity
Solution Approach 1:
The invention modifies the cap layer's electrode potential parameter by selecting metals with less negative standard electrode potentials, which fundamentally changes the layer's resistance to wet chemical etching. This allows standard etch recipes to be used without compromising cap layer integrity, maintaining manufacturing simplicity while improving reliability.
3Productivity
If copper interconnect dimensions are reduced to increase circuit density, then functionality is improved, but electromigration-induced material transport increases
Solution Approach 1:
The invention introduces a conductive cap layer as an intermediary protective structure on top of the copper interconnect. This cap layer acts as a barrier that prevents electromigration-induced material transport from the copper, enabling reduced dimensions and higher circuit density while maintaining reliability against electromigration effects.
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 significantly increases the etch resistivity of conductive cap layers, reducing defects and maintaining high electromigration performance, thereby enhancing the reliability and stability of copper-based interconnects in advanced semiconductor devices.
Implementation Method 1
The conductive cap layer is comprised of a ternary alloy including tungsten and at least one metal having a standard electrode potential that is less negative than a standard electrode potential of cobalt. The standard electrode potentials of the alloy species are considered to enhance etch resistivity against standard wet chemical etch recipes.
Implementation Method 2
Operating the interconnect structures at elevated current densities may entail a plurality of problems related to stress-induced line degradation, which may finally lead to a premature failure of the integrated circuit. One prominent phenomenon in this respect is the current-induced mass transport in metal lines and vias, also referred to as 'electromigration.'
Data Source
AI summary
A conductive cap material for a copper region may be provided with enhanced etch resistivity by taking into consideration the standard electrode potential of one or more of the species contained therein. For example, instead of a conventionally used CoWP alloy, a modified alloy may be used, by substituting the cobalt species by a metallic species having a less negative standard electrode potential, such as nickel. Consequently, device performance may be enhanced, while at the same time the overall process complexity may be reduced.