Low D_it HfO₂/Al₂O₃/In_0.53Ga_0.47As gate stack achieved with plasma-enhanced atomic layer deposition

We developed Al2O3 and HfO2 plasma-enhanced atomic layer deposition (PEALD) processes as part of the integration of a new high-k/In0.53Ga0.47As gate stack. The Al2O3 featured a bandgap of 7.0 eV and a k-value of 8.1, while the HfO2 presented a bandgap of 6.2 eV and a k-value of 14.6. W/HfO2/Al2O3/n-In0.53Ga0.47As metal-oxide-semiconductor capacitors (MOSCAPs) were fabricated and different In0.53Ga0.47As surface preparations [HF or (NH4)2S] were tested. Both surface preparations revealed similar gate stack electrical performance. Capacitance-voltage (C-V) characteristics yielded very low frequency dispersion near accumulation (as low as 0.3% at Vg = 1 V). Low (<1012/cm2 eV) density of interface traps (Dit) in the upper part of the In0.53Ga0.47As bandgap was also extracted from the high-low frequency C-V and conductance methods, confirming the suitability of PEALD for the integration of high-k dielectrics in n-channel In0.53Ga0.47As field effect transistors.