INFRARED STUDIES OF THE SURFACE AND GAS-PHASE REACTIONS LEADING TO THE GROWTH OF TITANIUM NITRIDE THIN-FILMS FROM TETRAKIS(DIMETHYLAMIDO)TITANIUM AND AMMONIA

The reaction of tetrakis(dimethylamido)titanium (Ti(NMe2)4) with ammonia has been studied in the gas phase and on titanium disilicide, aluminum, and copper surfaces using infrared spectroscopy. In the gas phase the main product of this reaction, dimethylamine, forms rapidly even at 300 K, and a fine yellow powder is deposited on the windows of the IR cell. Under ultrahigh vacuum conditions there is no reaction between Ti(NMe2)4 and NH3 on any of the three surfaces studied at temperatures between 300 and 650 K. Heating pure Ti(NMe2)4 to temperatures >550 K in the gas phase, leads to species that contain Ti-N-C metallacycles and N=C double bonds. The thermal decomposition of Ti(NMe2)4 on both TiSi2 and Al surfaces at temperatures up to 650 K yields films that contain titanium, nitrogen, and a significant amount of carbon. No decomposition is observed on copper; instead, molecular desorption occurs below 400 K. Our observations are compared with the known thermal chemistry of titanium dialkylamides in solution.