Research On Preparation And Characteristics Of Hafnium Base Mos Structures

With the rapid development of microelectronics industry driving by Moore’s Law, the basic element of integrated circuit, which is called metal-oxide-semiconductor field effect transistor (MOSFET), is becoming smaller and smaller. According to the principle of scaling down, we must reduce the thickness of gate oxide with a scale of l/k at every technology node, which makes the thickness of conventional SiO2gate oxide reduce to atomic level. Then, the gate tunneling leakage caused by quantum tunneling will become so large that the device can’t work properly. One way to solve this problem is to use high k dielectric which will allow for an increased physics thickness with the same equivalent oxide thickness so that it can improve device properties. For a successful high-k gate dielectric material, it should satisfy a set of requirements:1) it should have high k value;2) the energy barrier at substrate/oxide should be high enough to suppress the electron or the hole inject from substrate;3) good interface quality with the substrate;4) good thermodynamic stability;5) process compatibility. Among a variety of high k materials, HfO2has high k value (about25), wide band gap (5.7eV) for Si and good thermodynamic stability, so it is the most potential high k dielectric.In this paper, the HfO2film was grown by atomic layer deposition (ALD) on p-type Si (100) wafer. The as-prepared HfO2films were then subjected to RTA with the temperature up to600℃,800℃and1000℃in NH3ambient for30s. The nitrogen concentration increased from1.41%at600℃to7.45%at1000℃. We find that the conent of O-Hf-N became more and more and there is N-Hf-N at1000℃resulting band gap of the films decreased from5.82eV to4.94eV. By measuring C-V characteristic of Pd/HfO2/Si/Al MOS capacitor, the accumulative capacitance density of annealing at600℃,800℃and1000℃is1.43μF/cm^2,1.0μF/cm^2,1.05μF/cm^2respectively. The C-V hysteresis window decreased from0.52V to0.05V.Following Si and GaAs, SiC is the third semiconductor material. It has a wide band gape (3.25eV for4H-SiC), high breakdown field strength (～2-3MV/cm) and high electronics saturation drift velocity so that it can work in high temperature, high pressure, high-frequency and high-power conditions.As a comparison with the high successful Si/SiO2interface, the density of interface state (Dit) the SiO2/SiC interface is at least one or two order of magnitude higer (1012e V-1cm-2). The analyses of the distribution of states at the SiO2/SiC interface have suggested two dominant sources of electrically active defects, namely, carbon cluster and near-interface traps. In this paper, prior to the deposition of HfO2films, we treat the SiC substrate with O plasma in Plasma enhanced atomic layer deposition (PEALD). This can effectively inhibit the formation of C cluster and make the valence band offset of HfO2/SiC increase of0.22eV.