Reductive elimination of hypersilyl halides from zinc (II) complexes. Implications for electropositive metal thin film growth

Treatment of Zn(Si(SiMe3)3)2 with ZnX2 (X = Cl, Br, I) in tetrahydrofuran (THF) at 23 °C afforded [Zn(Si(SiMe3)3)X(THF)]2 in 83–99% yield. X-ray crystal structures revealed dimeric structures with Zn2X2 cores. Thermogravimetric analyses of [Zn(Si(SiMe3)3)X(THF)]2 demonstrated a loss of coordinated THF between 50 and 155 °C and then single-step weight losses between 200 and 275 °C. The nonvolatile residue was zinc metal in all cases. Bulk thermolyses of [Zn(Si(SiMe3)3)X(THF)]2 between 210 and 250 °C afforded zinc metal in 97–99% yield, Si(SiMe3)3X in 91–94% yield, and THF in 81–98% yield. Density functional theory calculations confirmed that zinc formation becomes energetically favorable upon THF loss. Similar reactions are likely to be general for M(SiR3)n/MXn pairs and may lead to new metal-film-growth processes for chemical vapor deposition and atomic layer deposition

Atomic layer deposition of Ru/RuO2Thin films studied by in situ infrared spectroscopy

The deposition of ruthenium thin films is investigated using a newly synthesized precursor (cyclopentadienyl ethylruthenium dicarbonyl, Ru(Cp)(CO)2 Et) and O2 gas as reactants. The conditions to achieve self-terminated surface reactions (sample temperature, precursor pulse length and precursor gas pressure) are investigated and the resulting composition, conductivity, and surface morphology are determined during/after deposition on hydrogen-terminated silicon (111) surfaces using in situ FTIR, and ex situ Rutherford back scattering, X-ray photoelectron spectroscopy, and atomic force microscopy. Higher growth rates (∼1.5-3 A˚ ) are obtained compared to those typical of ALD of metals (∼0.5-1 A˚ ), under conditions of saturation, i.e., through self-terminated surface reactions. Infrared absorption measurements reveal that bridged CO formed by the self-reaction of Ru(Cp)(CO)2 Et leads to surface passivation, thus terminating the precursor self-reaction. They also show that, under these “saturation” growth conditions, metallic Ru develops during the early stage of deposition (1-5 cycles), and RuO2 is observed later in the growth. The deposition rate is linear with cycles after an initially slow nucleation stage and the film becomes metallic after∼22 cycles. Thick films (∼45 nm) grown with short pulses produce metallic polycrystalline ruthenium with hcp structure