Research Of The (002) Oriented AIN Thin Films

Aluminium nitride (AlN) thin films have excellent physical and chemicalproperties and are becoming a promising material widly used in microelectronics,optics, mechanics and acoustics. Especially (002) oriented AlN thin films have highacoustic velocity and excellent piezoelectric properties and high electromechanicalcoupling coefficient which are a splendid piezoelectric material for the surfaceacoustic wave equipment. In this paper, high quality AlN thin films were deposited onthe Diamond/Si, Si and glass substrates, respectively by MIS800equipment and theproperties of AlN thin films were investigated.Firstly, AlN thin films were prepared by different methods, such as reactivemagnetron sputtering, ion beam assisted deposition and ion beam sputtering. Resultsreveal that AlN thin films prepared by pulse magnetron sputtering and ion beamassisted deposition respectively which both exhibit (002) preferential orientation. AlNthin films are amorphous films prepared by ion beam sputtering. The surface of AlNthin films is glazed and flat which prepared by pulse magnetron sputtering, while thesurface of the AlN thin films prepared by direct current magnetron sputtering is notflat, there are some particles on the surface. The AlN thin films exhibit completely(002) preferential orientation which prepared by ion beam assisted deposition ondiamond/Si, Si and glass substrates, while the surface of films deposited on Sisubstrate is loose and porous. The deposition velocity of pulse magnetron sputteringis higher than the velocity of ion beam assisted deposition and ion beam sputtering.The adhesive strength of AlN thin films is higher which deposited by pulse magnetronsputtering.Secondly, introducing several heterogeneous buffer layers between substratesand AlN thin films and the structures and properties of thin films were investigated. Itis demonstrate that AlN thin films exhibit (002) preferential orientation afterintroducing Al， Mo， Ti buffer layers but the adhesive strength decreased afterintroducing metal buffer layer. The films prepared by pulse magnetron sputteringexhibit (002) preferential orientation and the adhesive strength increase afterintroducing TiN buffer layer on the Si substrate. The degree of (002) preferentialorientation of AlN thin films increase remarkably, the films exhibited completely(002) preferential orientation after introducing ZnO buffer layer, but the adhesivestrength is not ideal. Finally, in order to increase the degree of (002) preferential orientation and theadhesive strength, the AlN homogenous buffer layer is introduced. The AlN thin filmscan acquire high (002) preferential orientation even at different target-to-subtrate anddifferent substrate temperature.The surface roughness of AlN thin films decreased andthe adhesive strength increased after introducing the homogeous buffer layer.