Research On Vapor Deposition And Control Of Preferential Orientation Of AlN Thin Films

Because of anisotropy of AlN crystal, it is believed that AlN thin films with (100) orientated are better for SAW propagating then with (002) orientated. But many authors think that it is hard to obtain AlN thin films with (100) oriented, and orientation growth mechanism for AlN thin films is still obscure. It is significant to study morphology and photoelectric performance for AlN thin films'application at the basis of preparing AlN thin films. In this thesis, AlN thin films with (002) transited to (100) orientated have been prepared through adjusting working pressure, substrate-target distance, sputtering power and substrate temperature by RF magnetron sputtering. AlN thin films have been characterized by XRD, SEM, AFM, RBS, FTIR and UV. In this thesis, deposition parameters such as working pressure, substrate-target distance, sputtering power, substrate temperature, and deposition time have been studied, and orientation growth law for AlN thin films has been obtained. Higher working pressure, longer substrate-target distance, lower sputtering power,lower substrate temperature and shorter deposition time are favor of growing AlN thin films with (100) oriented, in verse, with (002) oriented. By further study the deposition parameters and the results, 'Inverse S Model'of orientation growth mechanism for AlN thin films has been suggested. Smaller ratio of mean free path of Al atoms to substrate-target distance is in favor of growing AlN thin films with (100) oriented, in verse, with (002) oriented. Morphology of two kind of oriented AlN films are different, as characterized by SEM and AFM. Crystals of (002) oriented films are larger and uniformity then (100) oriented films and a lot of small crystals united together forming a large crystal in (100) oriented films; There is an amorphous layer at the interface of AlN/Si, as can be seen from the SEM section view of AlN thin films. Band gap of AlN thin films decrease with increased film thickness, as calculated by UV absorption spectra. RBS spectrum of AlN thin film showed that Al atoms and N atoms in the sample are...