AVS 52nd International Symposium
    Thin Films Tuesday Sessions
       Session TF-TuA

Paper TF-TuA4
Atomic Layer Deposition of Ruthenium on Organic Self Assembled Monolayers for Work Function Tuning

Tuesday, November 1, 2005, 3:00 pm, Room 306

Session: Atomic Layer Deposition - Metals
Presenter: K.J. Park, North Carolina State University
Authors: K.J. Park, North Carolina State University
D.B. Terry, North Carolina State University
G.N. Parsons, North Carolina State University
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Ruthenium is of interest for advanced metal/oxide/ semiconductor (MOS) transistor gate electrodes to reduce poly-silicon depletion and as a nucleation layer for copper interconnects. Patterned self assembled monolayers have previously been used to impede nucleation during ALD processing. In this work, metal atomic layer deposition was achieved on self-assembled monolayers, where the tail groups were chosen to promote, rather than impede nucleation, and the effect of the monolayer on the work function of the metal in an MOS capacitor is characterized. Specifically, Ru was deposited using bis-(cyclopetandienyl) ruthenium and oxygen onto HfSiO@sub x@, SiO@sub 2@, and onto 3-aminopropyltriethoxysilane (APTES) and undecenyl tricholosilane (UDS) monolayers formed on HfSiO@sub x@. Self-limiting atomic layer deposition was achieved at temperatures between ~310° and 350°C, corresponding to ~1 Å per deposition cycle. Capacitance vs. voltage (CV) with various thicknesses of dielectric was measured at 1MHz using p-type silicon substrates with doping levels of 1.5x10@super 18@ cm@super -3@, to determine the effective workfunction (@PHI@@sub m,eff@) of the ALD metal. The organic monolayer undergoes some reaction and modification during the metal ALD step, however CV measurements show relatively stable behavior at room temperature, with large changes observed after a 400°C forming gas anneal, suggesting stability of the monolayer during deposition. Ru on untreated HfSiO@sub x@ gives @PHI@@sub m,eff@ = 4.7 eV, whereas the APTES treated surface shows an increase in @PHI@@sub m,eff@ to about 4.8 eV, and a decrease to about 4.2 eV for the UDS surface. The shifts are consistent with dipoles in the monolayers at the organic/dielectric interface. The ability to deposit metal by ALD onto organic surfaces will likely be useful for a variety of advanced organic device structures.