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

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.