Mary E. Day

Correlation of electrical resistivity and grain size in sputtered titanium films

Abstract Thin Ti films deposited onto thermal SiO2 by sputtering in Ar or Ne are analyzed accounting for electron scattering at both film and grain boundary surfaces. An intrinsic resistivity of 54 and 63 μΩ cm, and an electron mean free path of 18 and 15 nm is derived for films sputter deposited in Ar and Ne, respectively. For both gases, a grain boundary reflection coefficient of 0.17 is calculated, assuming pure specular electron reflection at the film surfaces. Resistivity lowering is shown to correlate directly with an increase in grain size. Sputtering in Ar results in larger grain size films that have a small 21 μΩ cm residual resistivity and a high 2800 ppm temperature coefficient of resistance. The film grain size is independent of the deposition rate and reduced when sputtered in Ne, or in Ar and an applied negative substrate bias. The Ti film texture is found to be independent of film thickness and the presence of a collimator but sensitive to an applied substrate bias.

Electron Cyclotron Resonance Plasma Etching of Native TiO2 on TiN

Thin-film polycrystalline Tin with an approximate 2 nm thick native TiO{sub 2} overlayer is bombarded with 50 to 200 eV Ar ions in an electron cyclotron resonance plasma. In situ X-ray photoelectron spectroscopy and static secondary ion mass spectrometry suggest complete removal of oxygen from the planar surface, independent of ion energy, with TiO{sub 2} remaining on the columnar grain boundaries. The TiN etching rate increases from 6 to 14 nm/min as the ion energy is raised from 100 to 200 eV. The TiN stoichiometry does not change with ion bombardment.

Hydrogenating silicon dioxide in an electron cyclotron plasma

The hydrogenating effect of a low‐temperature, electron cyclotron resonance excited H2 plasma on the surface chemistry of thermal SiO2 films is analyzed in situ by x‐ray photoemission spectroscopy and static secondary ion mass spectrometry. Hydrogenation with this nominal 10 eV proton flux results in Si‐(O4), H‐Si‐(O3), (H2)‐Si‐(O2), (H2)‐Si‐O, and H‐Si‐(Si3) bonding states to the complete exclusion of Si—OH bond formation. A simple thermodynamic argument accounts for the exclusivity of Si—H bonds terminating the outermost (O3)‐Si‐O‐Si‐(O3) network of a thick SiOx<2 film, thereby transforming what is normally a hydrophilic surface into one that is hydrophobic.

Effect of electron cyclotron resonance H/sup +/, Ne/sup +/, Ar/sup +/, and Xe/sup +/ plasma precleaning on titanium silicide formation

A vacuum integrated cluster tool process incorporating electron cyclotron resonance plasma cleaning, Ti sputter deposition, and rapid thermal annealing in N/sub 2/ is used to form a TiN/sub x 150 eV Ne/sup +/ promotes silicidation, thereby minimizing nitride thickness. The effects of precleaning are significant as the activation energy for TiSi/sub y/ formation is reduced from 1.8 eV characteristic of a BOE cleaned surface to 1.2 eV on Si etched with 250 eV Ne/sup +/. Mechanistically, the silicide kinetics are shown to be inhibited by the presence of a thin amorphous layer that is formed only when cleaning Si with Ar/sup +/ and Xe/sup +/ with the effect that both knock-on oxygen atoms and implanted noble gas atoms trapped within the amorphous layer retard the requisite solid-phase epitaxial regrowth kinetics. Recrystallizing the amorphous Si surface prior to metallization appears to restore the near-normal silicide kinetics that is characteristic of Ne/sup +/ cleaning. >

Study of silicon surfaces bombarded with noble gas ions in an electron cyclotron resonance plasma

The effect of electron cyclotron resonance plasma cleaning (100)Si surfaces with low energy Ne, Ar, and Xe ions is studied by in situ x‐ray photoelectron spectroscopy, high‐resolution cross‐sectional transmission electron microscopy, atomic force microscopy, and measurement of both the single‐surface reflectance and the modulated optical reflectance. Photoemission spectra show that complete removal of all surface contaminants with oxygen atoms knocked‐in from the original native Si oxide and noble gas atoms implanted into the Si substrate are a common characteristic of this plasma cleaning process. The oxygen concentration appears to decrease with ion energy for all three ions, whereas the noble gas concentration is inversely proportional to the ion mass and essentially independent of the ion energy. This low energy ion bombardment sputters the surface causing only point defects with Ne ions, formation of a continuous thin amorphous overlayer with either Ar or Xe ions, and in addition, occasional subsurfa...