Inherent selective pulsed chemical vapor deposition of amorphous hafnium oxide / titanium oxide nanolaminates

Abstract

Water-free Inherent selective pulsed chemical vapor deposition (CVD) of HfO2/TiO2 nanolaminates on Si and SiO2 in preference to SiCOH has been studied. SiCOH is highly porous alkylated SiO2, which is used as a nonreactive low-k dielectric. Ti(OiPr)4 [titanium(IV) isopropoxide] and Hf(OtBu)4 [Hafnium tert butoxide] were used in the CVD study. Previous studies showed that metal alkoxide precursors could form oxide films through thermal decomposition. However, single oxide films greater than 2 nm can be rough due to crystallization. To solve this issue, HfO2/TiO2 nanolaminate structures were studied. With sequential dosing of each precursor in a supercycle at 300 °C sample temperature, HfO2/TiO2 nanolaminate films with thin (less than 3 nm) sublayers were selectively deposited. The films were smooth with root mean square (RMS) roughness lower than 0.5 nm and almost amorphous from XRD analysis; this is unexpected since both oxides readily crystalize. Amorphous nanolaminate oxide film deposition with high selectivity was achieved by controlling each sublayer thickness and the Hf:Ti ratio. TEM studies proved that ∼ 20 nm of the nanolaminate film could also be selectively deposited on nanoscale patterned surfaces. This selective amorphous nanolaminate oxide CVD process has a potential to be applicable in the nanoscale patterning in MOSFET fabrication.