Carmela Amato-Wierda

Kinetics and mechanism relevant to TiSiN chemical vapor deposition from TDMAT, silane and ammonia

Abstract Tetrakis(dimethylamino)titanium (TDMAT) is an important precursor for the metal-organic chemical vapor deposition (MOCVD) of TiN and TiSiN thin films, both of which are used as hard coatings. Understanding the kinetics and mechanism of the gas phase reactions in these processes will lead to a better understanding of the CVD process, and an improvement in material properties. As a basis for understanding the CVD of TiN and TiSiN, the focus of this research is on the kinetics and mechanism of TDMAT and silane decomposition. The experiments were performed in a hot-wall LPCVD reactor coupled to a molecular beam sampling system for the quadrupole mass spectrometer (MBMS). The gases are injected into the flow reactor through a temperature-controlled, moveable injector. At the end of the reactor a fraction of the gases are sampled and formed into a molecular beam, which passes along the axis of the system to the ion source of the mass spectrometer. The decomposition of TDMAT follows first-order kinetics in the temperature range investigated (333–593 K). The activation energy changes from 16 kJ mol −1 at low temperatures to 166 kJ mol −1 at high temperatures, which is indicative of a change in reaction mechanism from a heterogeneous mechanism at lower temperatures to a homogeneous one at higher temperatures. An increase in surface-to-volume ratio ( S / V ) increases the rate constants for each regime, but does not change the activation energies. The increase in rate constants in the high temperature regime with increased S / V indicates the presence of a surface component at high temperature in addition to the gas phase reaction. The silane decomposition reaction resulted in a calculated activation energy of 128 kJ mol −1 in the temperature range from 823 to 1023 K. The results of the reaction between TDMAT and silane at 723 K is also discussed.

Chemical vapor deposition of titanium nitride thin films from tetrakis(dimethylamido)titanium and hydrazine as a coreactant

Hydrazine was used as a coreactant with tetrakis(dimethylamido)titanium for the low-temperature chemical vapor deposition of TiN between 50 and 200 °C. The TiN film-growth rates ranged from 5 to 45 nm/min. Ti:N ratios of approximately 1:1 were achieved. The films contain between 2 and 25 at.% carbon, as well as up to 36 at.% oxygen resulting from diffusion after air exposure. The resistivity of these films is approximately 10 4 μΩ cm. Annealing the films in ammonia enhances their crystallinity. The best TiN films were produced at 200 °C from a 2.7% hydrazine–ammonia mixture. The Ti:N ratio of these films is approximately 1:1, and they contain no carbon or oxygen. These films exhibit the highest growth rates observed.

Chemical vapor deposition of TiWC thin films

Abstract TiWC thin films were deposited on stainless steel substrates (440C) by chemical vapor deposition (CVD) in a horizontal hot-wall reactor from a TiCl 4 W(CO) 6 CH 4 H 2 Ar gaseous mixture, at 1323 K and at pressures ranging from 0.13 to 20.00 kPa. The structures of the TiWC thin films were characterized using X-ray diffraction (XRD). The lattice constant of the TiWC films shifts from that of TiC to WC 1− x with increasing W concentration in the thin films. A morphological analysis was carried out using scanning electron microscopy (SEM). It was found that the surface morphology varied with the W concentration and total flow. Compositional studies and binding characteristics in the TiWC films were investigated by X-ray photoelectron spectroscopy (XPS). The associated hardness measured by nano-indentation ranged from 23 to 32 GPa. The studies of transmission electron microscopy (TEM) and selected area diffraction (SAD) reveal the detailed microstructure of the TiWC thin films and the presence of a WC phase.

Gas phase analysis of TiCl4 plasma processes by molecular beam mass spectrometry

Abstract Molecular beam mass spectrometry (MBMS) has been used to analyze the gas phase of Ar, Ar+TiCl 4 and Ar+TiCl 4 +NH 3 and CH 4 plasmas. The gas phase composition was analyzed as a function of pressure and plasma power. The results show that an increase in plasma power increases the concentration of dissociated and ionized species in the plasma phase. Higher plasma power increased the intensity of ions from TiCl 4 and Ar up until 100 W and then ion intensity starts to level off with increasing r.f. power. The Ar ion intensity increases with total reactor pressure up to 66.6 Pa and then ion intensity was found to decrease with pressure. In the case of the reaction of TiCl 4 and NH 3 , a single peak in the mass spectrum at m / e =80 is observed, possibly corresponding to Ti(NH 2 ) 2 + .

Low Temperature Chemical Vapor Deposition of Titanium Nitride Thin Films With Hydrazine and Tetrakis-(dimethylamide)Titanium

Hydrazine and tetrakis-(dimethylamido)titanium have been used as precursors for the low temperature chemical vapor deposition of TiN thin films between 50°C and 200°C at growth rates between 5 to 35 nm/min. At hydrazine to TDMAT ratios of 50:1 and 100:1 the resulting films show an increase in the Ti:N ratio with increasing deposition temperature. They contain 2% carbon, and varying amounts of oxygen up to 36% as a result of diffusion after air exposure. The low temperature growth is improved when hydrazine-ammonia mixtures containing as little as 1.9% hydrazine are used. Their Ti:N ratio is almost 1:1 and they contain no carbon or oxygen according to RBS. The TiN films grown from pure hydrazine or the hydrazine-ammonia mixture have some crystallinity according to x-ray diffraction and their resistivity is on the order of 10 4 µω cm. The low temperature growth is attributed to the weak N–N bond in hydrazine and its strong reducing ability. In these films, the Ti:N ratio is approximately 1:1.

CVD of Carbide Multi-Phased Coatings

TiC and Ti-W-C films have been produced by chemical vapor deposition (CVD). A fractional factorial design was used to study the effects of deposition temperature, C:Ti input, H:Ti input, reactor pressure, and total mass flow on TiC film composition. Statistical models were developed for both titanium at.% and C:Ti in the film. It was found that the most significant affect on titanium at.% was the interaction of temperature, pressure and total mass flow. The most important affect on the C:Ti in the deposited film was the interaction C:Ti input, H:Ti, and total mass flow. Ti-W-C films have been deposited at 1050°C at various (TiCl 4 +W(CO) 6 )/CH 4 inlet ratios ranging from 0.53 to 1.01. The characterization of the films revealed that the changes in deposition rate, crystallinity, film orientation, and morphology of various Ti-W-C compositions were affected by (TiCl 4 +W(CO) 6 )/CH 4 inlet ratios.