Preparation And Properties Of HfO₂ Thin Film Capacitors

With the continuous development of CMOS technology,the problem of increasing leakage current becomes more and more serious.In order to solve this problem effectively,we must get rid of Poly Si/SiON/Si gate dielectric and discover new materials for gate dielectric,otherwise it will severely limit the size of MOS transistor.Recently,so called“high-dielectric”,HfO₂ thin film is the representative of new gate dielectric materials.On the other hand,TiN thin film is an ideal choice for new gate electrode materials.In this paper,HfO₂ thin films were prepared by intermediate frequency reactive magnetron sputtering.The effects of sputtering time,substrate temperature and negative bias voltage on the phase structure,thickness and electrical properties of HfO₂ thin films were studied.Moreover,the effect of Y dopant in HfO₂ is also examined.The effect of sputtering time on phase structure,thickness and electrical properties of Y:HfO₂ thin films at same Y target power were studied.Moreover,the effects of Y doping on the chemical composition and surface roughness of the films were also compared.TiN thin films were prepared by RF reactive magnetron sputtering.The effects of sputtering time,sputtering power,negative bias voltage and substrate temperature on the phase structure,thickness and resistivity of TiN thin films were studied.The main experimental characterization methods used in thesis are:small angle grazing incidence X-ray diffraction?GIXRD?to measure the crystal structure of thin films,four-probe tester to measure the resistivity of thin films,X-ray reflectance?XRR?and step tester to measure the thickness of the films,X-ray photoelectron spectroscopy?XPS?to study the composition,content and combination type of the elements in the films,atomic force microscopy?AFM?to measure the surface roughness of the films;and ferroelectric tester to measure the polarization-electric field?P-E?curves and current density-electric field?J-E?curves of the HfO₂ films.The experimental results showed that HfO₂ and TiN thin films prepared under the large negative bias absolute value of sputtering had excellent properties,dense film layers and small surface roughness.The optimum parameters of preparation of TiN films are:sputtering power 200W,target distance 93mm,the substrate temperature 350^?C,bias-200V,sputtering time 30min,the TiN film thickness of 106nm,the resistivity of 27.3???cm,the surface of the film is pure golden.The crystal structure of prepared HfO₂ thin film is monoclinic phase,and its polarization-electric field?P-E?curve presents a straight line,which indicates that the thin film has dielectric property.The film thickness and leakage current density were reduced by the introduction of bias.The thickness of HfO₂ films decreases from 25nm to 9nm with the increase of absolute negative bias voltage.The bias leakage current density of the film capacitor decrease from 1.3×10^-4A?cm^-2 to 5.4×10^-7A?cm^-2,respectively,at the field strength of 1MV/cm.The Y:HfO₂ films prepared by RF-MF reactive magnetron sputtering with different sputtering times were higher than the relative dielectric constant of HfO₂ films,and the leakage current density of film capacitors shows a gradual downward trend,respectively,at the field strength of 1MV/cm.