Preparation And Properties Research Of Multilayer Films For BAW Device

To the development of base material for high-frequency high-power BAW devices, weconstruct the "AlN/Al/Si" and "ZnO/Al/Si" of the multilayer structure. AlN is a kind ofimportantⅢ－Ⅴcompound semiconductor material with wide band-gap, which has wurtzitecrystal structure and many excellent physical properties. AlN thin films were applied widelyin BAW devices for its higher acoustic velocity in GHz level. ZnO is aⅡ-Ⅵcompoundsemiconductor material with wide band-gap,which has hexagonal wurtzite crystalstructure.For its excellent physical properties, ZnO films are widely used in BAW devices.Around "AlN/Al/Si" and "ZnO/Al/Si" of the multilayer structure, this paper’s works areas follows:Using RF magnetron sputtering method to prepare AlN/Al/Si structure on the Sisubstrate, this paper studies the influence of performance of the film at the different postprocessing conditions and substrate temperature.The film is analyzed by the XRD andAFM,finally concluded that:(1)After the experiment,the sample is continued heating for 1hour aroung N2at 1 Pa pressure,it’s helpful for AlN to grow according to (002) crystalorientation,and after post processing roughness got obviously improved. (2) Differentsubstrate temperature on the morphology of film structure also has an important effect.Studiesshow that, when the substrate temperature is 300℃,the film mainly grow according to (002)crystal orientation,and the surface roughness is the minimal.(3)The small target-substratedistance is conducive to the (002) preferred orientation and a better crystalline quality.Thegrain size increases and grain arranges compactly.In addition,the combination of AlN thinfilm prepared and the target base keeps firmer.Using rf magnetron sputtering method to prepare ZnO/Al/Si structure on the Si substrate,The film is analyzed by the XRD and SEM and the analysis shows that: (1) The preparationconditions of ZnO thin film are as follows, temperature of 200℃, pressure of 1 Pa, power of100W, N2:Ar=8:4,target distance at 5 cm,sputtering time for 120 minutes.After postprocessing at 400℃half height width of (002) peak is obvious reduced, grain size increases,the film obviously grows at (002) preferred orientation. (2) Different substrate temperaturealso has an important effect on orientation and roughness of ZnO.The results show that, whensubstrate temperature is 350℃, the film has a good (002) preferred orientation.Along with thesubstrate temperature rises, the grain size increases first then decreases. (3) Using the PFMmethod to analyze piezoelectric properties of ZnO thin film, and we found both of the verticaldirection and parallel direction of the film surface have piezoelectric response.