Study On The Structure And Properties Of Oxygen Doped AlN Thin Films

Aluminum nitride(AlN)thin films,as an important group ?-? compound,have the advantages of high surface acoustic wave velocity,high voltage electrical coefficient and good chemical stability,which make AlN piezoelectric thin films attract much attention in the field of high frequency surface acoustic wave devices.In the preparation process of AlN thin films,the films are extremely sensitive to oxygen,and few oxygen impurities can have a great impact on the structure and properties of AlN thin films.In this paper,the doping and orientation of AlN piezoelectric thin films in high back vacuum are studied.In this paper,using the MW-ECR RF unbalanced magnetron sputtering equipment independently developed by the three beam material modification Laboratory of College of physics of Dalian University of technology,oxygen doped AlN thin films were prepared by two ways.One is single-layer oxygen doping,that is,oxygen only participates in the reaction before the preparation of AlN Thin Films,changing the oxygen doping time;The second way is multi-layer oxygen doping,that is,the preparation process of AlN thin films is divided into five stages with the same time,and the doping time of oxygen in each stage is changed.The structure and properties of oxygen doped AlN films were characterized by X-ray diffraction(XRD),photoluminescence fluorescence spectrometer(PL),ultraviolet near infrared transmission spectrometer and Fourier transform infrared spectrometer(FT-IR).The experimental results show that the preferred orientation of AlN thin films prepared by single-layer oxygen doping method is closely related to the types of defects.The AlN thin films grow preferentially along(002)crystal plane with shorter oxygen doping time,and the number of single defects is equal to that of composite defects;The results show that AlN films grow preferentially along the(100)crystal plane with longer oxygen doping time,and the single defects are far less than the composite defects.With the increase of oxygen doping time,AlN(100)crystal face appears but not preferred,(002)crystal face remains preferred but the crysta l quality decreases.With the increase of oxygen doping time,the luminescence of oxygen related defects in both AlN films is enhanced,and the maximum enhancement wavelength is mainly between 500 nm and 600 nm.In the process of increasing the oxygen doping time,the transmittance of AlN thin films prepared by single-layer oxygen doping method at 300 nm is higher than that of AlN thin films without oxygen doping,which is analyzed from the point of view of bond energy and accompanied by the change of band gap;However,the transmittance of AlN films prepared by multi-layer oxygen doping method at 300 nm is much lower than that of AlN films without oxygen doping.From the point of view of bond energy,it is also accompanied by the change of band gap.FT-NIR spectra show that AlN thin films prepared by two kinds of oxygen doping methods have Al-N absorption peaks,and with the increase of oxygen doping time,the peak position "blue shift" caused by internal stress appears,which indicates that the AlN thin films are relatively dense.