Effect of NH3 surface nitridation temperature on mobility of ultrathin atomic layer deposited HfO2

Effect of NH3 predeposition anneal (pre-DA) temperature prior to ultrathin atomic layer deposition (ALD) HfO2 deposition (15–30 Å) on equivalent oxide thickness (EOT) and mobility of TiN∕HfO2∕Si metal-oxide field effect transistors has been studied systematically. At the same physical thickness, reduction of EOT by high temperature NH3 pre-DA treatment (∼900°C) has been achieved, with no apparent change in Jg (leakage current density), though no significant channel mobility reduction could be observed. Increase in nitrogen content with pre-DA temperature improved overall dielectric constant and bulk trapping immunity, though slight mobility reduction was attributed to positive charge pile up at the interface. The ultrathin EOT (∼7.4Å) with good mobility values sets ALD HfO2 as a very promising candidate for alternate gate oxide.