Noble Metal Cap Layer Enhances Etch Resistivity for Copper Interconnects
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Solution Overview
Problem
In the fabrication of advanced integrated circuits, copper-based metallization layers face challenges such as electromigration-induced degradation and void formation due to high current densities, which can lead to premature device failure, especially when using low-k dielectric materials and complex patterning processes.
Innovation Solution
A noble metal protection layer is selectively deposited on exposed portions of the conductive cap layer to enhance etch resistivity during wet chemical treatments, maintaining the integrity of the cap layer and preventing material removal, thereby reducing void formation and process non-uniformities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wet chemical etching is used to remove damaged dielectric material, then etching efficiency is improved, but the conductive cap layer is removed or degraded
Solution Approach 1:
A noble metal protection layer (such as ruthenium, rhodium, or iridium) is deposited on the conductive cap layer before wet chemical etching. This protection layer acts as an intermediary that is resistant to the wet chemical etchant, allowing the etch to remove damaged dielectric material while preserving the underlying conductive cap layer. The protection layer can be selectively removed after the etching process is complete.
Solution Approach 2:
The patent modifies the chemical parameters of the etching process by introducing a protection layer with different chemical resistance properties. By changing the surface chemistry through the protection layer, the etchant selectively attacks the dielectric material while being blocked from attacking the conductive cap layer, thus resolving the contradiction between etching efficiency and cap layer integrity.
2Reliability
If copper-based metallization is used to reduce electromigration, then resistance to electromigration is improved, but copper diffusion into dielectric materials occurs
Solution Approach 1:
The metallization structure is segmented into multiple functional layers: a copper-based core layer for electrical conduction and electromigration resistance, and an outer conductive cap layer (such as cobalt tungsten phosphide) that acts as a diffusion barrier. This segmentation allows each layer to perform its specific function - the copper core provides low resistance and electromigration resistance, while the cap layer prevents copper diffusion into the dielectric material.
Solution Approach 2:
The patent employs composite metallization structures combining copper with other materials. The copper-based interconnect is combined with a conductive cap layer material that provides both electrical conductivity and diffusion barrier properties. This composite structure maintains the electrical performance benefits of copper while eliminating its harmful diffusion characteristic.
3Productivity
If feature sizes are reduced to increase circuit density, then circuit functionality is improved, but current density in interconnect lines increases
Solution Approach 1:
The patent uses composite interconnect structures with copper-based core layers that have superior electrical conductivity and electromigration resistance compared to traditional aluminum. This allows the interconnect lines to carry higher current densities without degradation, enabling continued scaling to higher circuit densities while maintaining reliable operation at the increased current densities required by smaller feature sizes.
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 use of a noble metal protection layer allows for efficient wet chemical etching while maintaining the integrity of the conductive cap layer, enhancing the reliability and performance of copper-based interconnects by reducing material transport and void formation, thus improving the overall reliability of the metallization system.
Implementation Method 1
A noble metal protection layer is selectively deposited on exposed portions of the conductive cap layer to enhance etch resistivity during wet chemical treatments
Implementation Method 2
efficient wet chemical etching while maintaining the integrity of the conductive cap layer
Implementation Method 3
enhance etch resistivity during wet chemical treatments, maintaining the integrity of the cap layer and preventing material removal
Implementation Method 4
provide a barrier layer between the copper and the dielectric material in which the copper-based interconnect structures are embedded
Data Source
AI summary
During the fabrication of sophisticated metallization systems of semiconductor devices, material deterioration of conductive cap layers may be significantly reduced by providing a noble metal on exposed surface areas after the patterning of the corresponding via openings. In one embodiment, a semiconductor device is provided that includes a metallization system formed above a substrate. The metallization system includes a metal line formed in a dielectric layer and having a top surface. The metallization system also includes a conductive cap layer formed on the top surface. A via extends through the conductive cap layer and connects to the top surface of the metal line. A conductive barrier layer is formed on sidewalls of the via. An interface layer is formed of a noble metal between the conductive cap layer and the conductive barrier layer and between the top surface of the metal line and the conductive barrier layer.