Passivation routes to binary and ternary intermetallic compounds

Due to challenges to metallize interconnect lines below 10 nm half pitch in the near future, new alternative metallization schemes have recently been explored to replace Cu, which has been the traditional choice for interconnect metallization during the last 20 years. After an initial focus on alternative elemental metals such as Co, Mo, or Ru, research has lately evolved to include also binary and ternary compounds, targeting improved reliability and resistivity at small dimensions. Transition metal aluminides are amongst the intermetallics with potential as alternative metals in scaled interconnects. As an example, AlNi, Al₃Sc, AlCu, and Al₂Cu thin films have been investigated as potential alternatives for Cu in interconnect metallization schemes. Several challenges are associated with the instability of these materials with respect to surface oxidation which leads to performance degradation. Different metal oxide removal and surface cleaning chemistries will be tested in combination with organic and inorganic selective capping layers to overcome the formation of an oxide top layer.

The goal of this PhD is to investigates the interaction between these metals and a range of corrosion inhibitors, such as benzotriazole and heterocyclic self-assembled molecules... The inhibitors will be deposited in the liquid and vapor phase and combined with in-situ metal surface cleaning. Various analytical techniques will be used to elucidate surface chemistry and surface reaction mechanisms.

A second class of organic passivation agents consists in monomolecular SAMs derived from alkyl-thiols, alkyl-selenols, or alkyl-amino precursors.

Finally, graphene is known to strongly interact with transition metals such as Ni and suppress oxidation of the surface.  It has therefore been identified as an additional promising candidate as a metal passivation layer in this project, especially as it can be highly conductive and may further reduce the NiAl sheet resistance.  Graphene as a passivation layer for binary intermetallic compounds on this nanoscale has not yet been demonstrated, and therefore this project will progress this research beyond the current state-of-the-art.

A cross-team collaboration between the surface and interface preparation, thin film deposition and characterization experts will enable and in-depth understanding of material properties and mechanisms.