Preparation Of Suitable For SAWD Double Orientation AlN Thin Films

With the increasing of electronic communications equipment information processing, thefrequency of carrier telecommunication toward to the GHz or higher level, so the multilayerfilms structure of surface acoustic wave (SAW) devices are has attracted many attentions ofthe scholars because of its high frequency characteristics.(100)AlN due to its high velocity,(002) AlN has a high electromechanical coupling coefficient, combined with the advantagesof the above two kinds of the AlN films prepared multilayer films structure, it can guaranteethe need of high frequency characteristics of the SAW device. In this paper, by optimizing theprocess of (100) and (002) AlN films, the two kinds of crystal orientation AlN thin films wereprepared and combined to a multilayer AlN thin film structure suitable for SAW devices.This paper introduces the concept, structure, working principle and characteristics of theSAW and SAW device, based on the current research status at home and abroad in this paper,we are put forward the theoretical foundation and main work. This paper introduces the basicknowledge of the crystal structure of AlN films, the common method and sputteringparameters. The research work what I carry out as follow:First of all, using radio frequency magnetron sputtering to prepare (100)AlN thin films,explores the nitrogen argon ratio, sputtering power and working pressure condition on thequality of AlN film. The results show that in the pure nitrogen atmosphere, sputtering poweris150W and the pressure is1.0Pa is the best preparation parameter. In addition, the study findthat good orientation can be obtained when the substrate temperature is300℃, then in situannealed in argon atmosphere after1h can effectively improve the film crystallinity andalleviate the membrane stress, the excellent (100) AlN thin films can be obtained.Second, in order to solve the difficulty of (100) AlN directly deposited on (002) AlN,consider adding the Al buffer layer between (100) AlN and (002) AlN. And if there is an Albuffer layer on the quality of the (002) AlN were compared. In addition, the Al buffer layersputtering time on the quality of the AlN films (002) are studied, the results show that the(002)AlN film deposited on complete buffer layer has a better crystalline and lower surfaceroughness than on incomplete one. With the increase of Al buffer layer sputtering time, it’sconducive to improving the (002) AlN films crystalline and releasing thin-film stress, theideal (002) AlN/Al/Si multilayer film structure can be obtained.Third, based on the optimization of (100) AlN film as the substrate, the (002) AlN/Alstructure deposited on (100) AlN thin film substrate, design and prepare the (002) AlN/Al/(100) AlN/Si multilayer structure, and the test results show good performance.