Preparation And Photoelectric Properties Of HfO₂ Film By ALD Combined With MWA

With the continuous development of science and technology,people have higher and higher requirements on the performance and size of optoelectronic devices and semiconductor devices,which leads to the upsurge of research on nano film materials.Hafnium oxide?HfO₂?thin films have attracted much attention due to their high transmittance,large optical band gap,high dielectric constant and good thermal stability.In this paper,HfO₂ Thin films were prepared by atomic layer deposition?ALD?to improve the optical properties of the films,increase the dielectric properties,reduce the leakage current density and dielectric loss.Combined with microwave annealing?MWA?heat treatment,the quality of the films was high,and had better electrical properties and stability.?1?Using ALD to prepare HfO₂ thin films,the effects of substrate temperature and deposition cycle number on the properties of thin films were studied.The results show that when the substrate temperature is greater than 200°C,sufficient energy can be generated to crystallize the film.The prepared HfO₂ film has good anti-reflection performance;the refractive index from the visible to the near infrared spectral range increases with increasing temperature.Compared with the amorphous state,the crystallized HfO₂ film becomes denser at 290°C the uniformity and density of the film are the best.With the increase of the number of deposition cycles,the growth rate of the film is basically unchanged,about 0.13nm/cycles;the roughness of the film increases with the increase of the deposition cycle,Sq from 1.85nm to 7.93nm;there are three processes in the film growth process:aggregation Growth,island growth and nucleation growth;as the number of cycles increases,the refractive index of the HfO2film gradually increases and the transmittance decreases slightly.As the number of cycles increases,the band gap also increases,from 5.56eV for 500 cycles to 5.82eV for 2000 cycles.The photoluminescence band of the thin film shifts by 0.01 eV to the long wave as the number of cycles increases.At 2000 cycles,the HfO₂ film has a maximum dielectric constant of 43.8,and the greater the breakdown voltage,the lower the leakage current density.?2?HfO₂ Thin films were prepared by different oxygen sources and their properties were characterized.The results show that when the number of cycles is more than 1000,the crystallinity and surface roughness of HfO₂ film prepared by H₂O as precursor oxygen source in the same cycle are better than those by O₃ as oxygen source.This is because when water is used as the precursor of oxygen source,crystalline particles are formed on the surface,while when ozone is used as the precursor of oxygen source,only particles gather on the surface and no crystals are formed,which is in an amorphous state;because the film HfO₂ prepared by H₂O as the precursor of oxygen source has higher density,grain size and crystallinity,its refractive index is higher;the film HfO₂ prepared by O₃ precursor has better permeability The maximum optical band gap is 5.9eV.?3?The effects of microwave annealing temperature and time on the properties of HfO2 films were studied.The results show that with the increase of annealing time,the crystallinity of the film increases,the surface roughness decreases and monoclinic structure appears;the reflectivity appears the lowest point of antireflection in the visible light region,and the refractive index is not affected by the microwave annealing time,and the refractive index is 1.99-2.25 in the near ultraviolet to near infrared band.The maximum dielectric constant of the film is 14.2 in the as deposited state.With the increase of microwave annealing time,the ionic polarization decreases,which leads to the decrease of the dielectric constant of the film.When the annealing temperature is 350^°C,the polycrystalline state begins to appear.When the annealing temperature is 450^°C,the characteristic peak of monoclinic crystal structure appears,indicating that the film has been transformed into polycrystalline state.With the increase of microwave annealing temperature,the refractive index increases,the transmittance decreases,and the band gap decreases from 5.76ev to 5.54ev.In addition,the photoluminescence peak value of HfO₂ film also shifted 0.03ev by microwave annealing.