Effect Of Interface Passivation On The Electrical Properties Of Gd₂O₃-doped-HfO₂High-k Films

Recently, with the rapid development of complementary Metal-Oxide-Semiconductor (CMOS) integrated circuit according to Moore’s law, the device size will scale down continuously. Decreasing of thickness of SiO2insulator causes dielectric high leakage current and it is necessary to find new materials with high dielectric constant to replace SiO2. As application of the high-k materials as gate dielectric, some problems occur:one is the creation of interface layer between the substrate and the high-k, which calls for a suitable method for interfacial passivation. Another is degradation of carrier mobility which can be solved by introducing a new substrate with a high carrier mobility. In this paper, GDH(Gd2O3-doped-HfO2) was taken as high-k gate dielectric material, and Si and Ge were selected as substrates, some studies were done on the effect of Al2O3interfacial control layer and nitridation for interfacial passivation on the electrical properties of GDH film.(1)The GDH films were deposited on p-Si(100) substrate by magnetron sputtering, and the effect of N2annealing on the electrical properties of Ag/Si/GDH/Pt/MOS have been studied. The results show that:with annealled, the hysteresis and the shift of flat band voltage of C-V curves get better, the maximum accumulation capacitance rises and the leakage current at a gate voltage of-1V decreases.(2)lnm Al2O3interfacial control layer was introduced between the substrate and high-k by atomic layer deposition. The results show that AlI2O3interfacial control layer suppresses the growth of native interface layer:with Al2O3interfacial control layer, the thickness of interface for p-Si(100)/GDH system reduces from4nm to2.8nm, and Ag/Si/Al2O3/GDH/Pt stack showes better properties:the leakage current at a gate voltage of-1V decreases two orders of magnitude compared with the sample without Al2O3, CET decreases from5.4nm to2.7nm, and the flat band voltage changes to-0.5V compared the former-1.98V, the hysteresis decreases from0.7V to40mV. For n-Ge(100)/GDH system, after1nm Al2O3interfacial control layer introduced, the thickness of the interface between the substrate and high-k reduces from5nm to2nm. Al/Ge/Al2O3/GDH/Ti/Au stack shows better electrical properties:the leakage current at a gate voltage of1V decreases nearly two orders of magnitude compared with the sample without Al2O3, CET decreases from4.36nm to1.98nm, the flat band voltage changes to1.53V compared the former2.07V, and the hysteresis decreases from1.07V to50mV.(3)Effects of pre-nitridation on Ge substrate have been studied. The results show that: GeOxNy films have been formed after nitrogen treatment and the thickness of the interface layer between Ge substrate and GDH decreases by2nm. The effect of NH3-annealing on the electrical properties of Au/Ti/GDH/Ge/Al stack is remarkable. Capacitance-Voltage(C-V) characteristics shows better properties in higher nitridation temperature:maximum accumulation capacitance promotes and hysteresis become better. But the leakage current increases.