Contact Structure Barrier Integrity via Protective Cap
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Solution Overview
Problem
Conventional methods face challenges in selectively removing titanium nitride hardmasks from dual damascene structures without etching the underlying metal contact structure barrier layers, leading to void formation and integrity issues during wet etching processes in semiconductor fabrication.
Innovation Solution
The use of fluorine-free tungsten (FFW), tungsten carbide, or tungsten nitride as barrier layers, combined with a conductive contact cap that encapsulates the plug metal and barrier layer, prevents etching during the removal of the hardmask using a suitable wet etchant, ensuring the barrier layer's integrity and allowing for selective hardmask removal without damaging the contact structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If titanium nitride is used as both metal hardmask and barrier metal, then material versatility is improved, but selective etching becomes impossible leading to void formation
Solution Approach 1:
A contact cap layer is introduced as an intermediary protective layer between the wet etchant and the barrier metal layer. The contact cap is selectively removed after protecting the barrier metal during etching, enabling the use of titanium nitride for both hardmask and barrier metal while preventing etchant attack on the contact structure
Solution Approach 2:
The contact cap is formed in advance before the wet etching process to pre-establish protection over the barrier metal layer. This preliminary protective action allows subsequent selective removal of the hardmask without damaging the underlying contact structure
2Productivity
If wet etching is used to remove metal hardmask, then hardmask removal efficiency is improved, but barrier layer etching occurs causing voids
Solution Approach 1:
The contact cap provides localized protection specifically over the barrier metal layer and plug metal, allowing the wet etchant to freely remove the hardmask in other areas. This selective local protection enables efficient hardmask removal while maintaining precise contact structure dimensions without void formation
3Device complexity
If same metal is used for hardmask and barrier layer, then process simplification is achieved, but selective etching cannot be performed
Solution Approach 1:
The protective function is segmented into a separate contact cap layer distinct from the barrier metal layer. This segmentation allows both layers to be formed from the same material (titanium nitride) for process simplification, while the contact cap's selective removal capability enables easy manufacture without compromising selective etching feasibility
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 effectively inhibits etching of the contact structure barrier layers, maintaining their integrity and preventing void formation, even when the hardmask and barrier layer are formed from the same material, enabling broader selection of wet etchants for hardmask removal and improving metal integrity in integrated circuits.
Implementation Method 1
A wet etching process is normally performed after forming the via and/or trench of the dual damascene structure to remove the metal hardmask
Implementation Method 2
a conductive contact cap that encapsulates the plug metal and barrier layer, prevents etching during the removal of the hardmask
Data Source
AI summary
Integrated circuits with improved contact structures are provided. In an exemplary embodiment, an integrated circuit includes a semiconductor substrate disposed with a device therein and/or thereon. The integrated circuit includes a contact structure in electrical contact with the device. The contact structure includes a plug metal and a barrier layer, and the barrier layer is selected from fluorine-free tungsten (FFW), tungsten carbide, and tungsten nitride. The integrated circuit further includes a dielectric material overlying the semiconductor substrate. Also, the integrated circuit includes an interconnect formed within the dielectric material and in electrical contact with the contact structure.