Electrical Properties of HfO₂ on Si_1-xGe_x Substrates Pretreated Using a Y Precursor with and without Subsequent Oxidant Pulsing

We introduced Y-O bonds in the interfacial layer between HfO₂ and Si_1-xGe_x (x = 0, 0.15, and 0.3) using two different pretreatment methods to minimize the number of interfacial defects. The pretreatments involved the application of cyclic pulses of Y(CpBut)₃ and N₂, which proceeded with or without the injection of an oxidizing agent (H₂O) at 250 °C, which was the temperature used for the subsequent in situ atomic layer deposition of HfO₂. Both Y pretreatments were beneficial in reducing the leakage current and positive flatband voltage shift, which were induced by an increase in the Ge concentration of the substrate. In addition, the interface state density was significantly reduced by the pretreatments, and this effect was more pronounced when the oxidizing agent injection step was skipped. However, both pretreatments increased the capacitance-equivalent oxide thickness, thereby having an adverse effect, possibly owing to a change in the composition of the interfacial layer.