Bis(diethylamino) silane as the silicon precursor in the atomic layer deposition of HfSiOx

Bis(diethylamino) silane is studied and evaluated as a liquid-phase, silicon precursor in the low-temperature atomic layer deposition (ALD) of hafnium silicate films. The depositions were performed using ozone as the oxidizing reagent and tetrakis(diethylamino)hafnium as the source of hafnium in hafnium silicate. The ALD process temperature windows for the deposition of silicon dioxide and hafnium oxide from the aforementioned precursors overlap between 200 and 250 degrees C. This overlap of temperature process windows is especially advantageous as it allows ALD of composite HfSiOx films. The variable compositions of HfSiOx films were prepared by varying ALD pulse sequencing, and excellent tunability of film composition is confirmed using Rutherford backscattering spectroscopy. The morphology of resulting films was also studied using X-ray diffraction. Whereas the SiO2 films were amorphous after deposition and remained amorphous up to deposition annealing temperatures of 1000 degrees C, the HfO2 films were amorphous as-deposited but started crystallizing at annealing temperatures above 600 degrees C. The amorphous structure stability in ternary films of HfSiOx was found to depend on the relative amounts of hafnia and silica deposited. For example, films prepared by alternating five cycles of hafnia and one cycle of silica remained amorphous up to 800 degrees C annealing, while films prepared by less than 2:1 alternating hafnia:silica cycles remained amorphous up to 1000 degrees C. (C) 2008 The Electrochemical Society.