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Thermally activated chemical vapor-phase etching of titanium nitride (TiN) is studied by utilizing either alternate exposures of niobium pentafluoride (NbF5) and carbon tetrachloride (CCl4) or by using CCl4 alone. Nitrogen (N2) gas purge steps are carried out in between every reactant exposure. Titanium nitride is etched in a non-self-limiting way by NbF5-CCl4 based binary chemistry or by CCl4 at temperatures between 370 and 460 °C. Spectroscopic ellipsometry and a weight balance are used to calculate the etch per cycle. For the binary chemistry, an etch per cycle of ≈0.8 Å is obtained for 0.5 and 3 s long exposures of NbF5 and CCl4, respectively at 460 °C. On the contrary, under the same conditions, the etch process with CCl4 alone gives an etch per cycle of about 0.5 Å. In the CCl4-only etch process, the thickness of TiN films removed at 460 °C varies linearly with the number of etch cycles. Furthermore, CCl4 alone is able to etch TiN selectively over other materials such as Al2O3, SiO2, and Si3N4. X-ray photoelectron spectroscopy and bright field transmission electron microscopy are used for studying the post-etch surfaces. To understand possible reaction products and energetics, first-principles calculations are carried out with density functional theory. From thermochemical analysis of possible reaction models, it is found that NbF5 alone cannot etch TiN while CCl4 alone can etch it at high temperatures. The predicted byproducts of the reaction between the CCl4 gas molecules and TiN surface are TiCl3 and ClCN. Similarly, TiF4, NbFCl3, and ClCN are predicted to be the likely products when TiN is exposed to both NbF5 and CCl4. A more favorable etch reaction is predicted when TiN is exposed to both NbF5 and CCl4 (ΔG = -2.7 eV at 640 K) as compared to exposure to CCl4 only (ΔG = -2 eV at 640 K) process. This indicates that an enhanced etch rate is possible when TiN is exposed alternately to both NbF5 and CCl4, which is in close agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Metal matrix nanocomposite thin films consisting of TiF3 nanoparticles embedded in TiN matrix were synthesized with the atomic layer deposition (ALD) method. TiF4, Si2H6 (or Si3H8), and NH3-based process at 350-370 °C led to nanocomposite TiF3:TiN thin films with the embedded TiF3 nanoparticles in the size range of 2-50 nm. The films grown on quartz wafers were conductive and transparent in the visible spectral range. The resistivities of the films could be controlled by the (TiF4 + Si2H6)/NH3 pulsing ratio. Transparency of the films correlated with the resistivity of the films, namely the more transparent the films were, the higher the resistivities. About 4 cm2 area photovoltaic cells with TiF3:TiN/SiO2 (1.5-20 nm)/p-Si (1-85 Ωcm)/SiO2 (1.5-20 nm)/TiN structures resulted in 0.10-0.45 V open circuit voltage and 1-2.5 μA current flow into a 120 Ω load resistor under halogen lamp (Osram 50 W, 240 V bulb, 2800 K) illumination. The mechanism of the photovoltaic effect in these structures is not known in detail, but it is suggested that the TiF3:TiN nanocomposite functions as a partly transparent conducting electrode on the silicon wafer forming a MIS-type silicon photovoltaic cell. This new material and its derivatives may have multiple applications in current and future photonic devices. TEM images of the TiF3:TiN nanocomposite thin film. The plan view image is a dark field image showing the TiF3 crystallites as bright spots, whereas the cross sectional image is a bright field image showing the TiF3 crystallites as dark spots. [ABSTRACT FROM AUTHOR]