The Research Of AlN/diamond Multilayed Films For High Frequency SAW Delay Line

Diamond has excellent properties such as the highest SAW velocity、the highest thermalconductivity and so on,which make it applied in various applications.However,diamond itselfis not piezoelectric materials and can’t carry on energy conversion between electromagneticwave and surface acoustic wave,So we need deposit a layer of piezoelectric thin films to makeit into multilayered structure SAW devices.The performance of SAW is decided bypiezoelectric thin films and diamond substrate together.AlN is an important Ⅲ-Ⅴcompound semiconductor material,which has many excellentphysical and chemical characteristics, so it has being widely used in microelectronics、optics、electronics and so on.Because AlN material itself has the highest phase velociety amongpiezoelectric materials,"AlN/diamond" multilayered structure can achieve a higher frequencythan "ZnO/diamond" and "LiNbO3/diamond" structure;The difference of phase velocitybetween AlN and diamond is small,so AlN/diamond multilayered structure show a lowerspeed frequency dispersion;The temperature coefficient of AlN material is small, the centerfrequency of AlN/diamond multilayered structure drift very small with temperatureincreasing,this is a big advantage,especially for narrowband filter.This paper focus on the preparation of AlN(002)/diamond multilayed films of highfrequency SAW delay line,our strudy work as follow:Firstly,we introduce the principle of work of SAW delay line;Secondly,Heterogeneous extension diamond film have been deposited on (100)silicon inmixture atmosphere of O2/H2/CH4gas by microwave plasma CVD method,The film strctureand morphology have been characterized using the X-ray diffraction analyzer(XRD)、RamanSpectrometer and scanning electron microscopy(SEM),the results showed that the preparationof diamond film has high diamond phase purity and closely spaced grain,thereby,we have gotthe diamond thin films for the construction of high frequency SAW devices.Thirdly,AlN thin films with highly C-axis prefential orientation has been deposited onpolished diamond substrates by RF magnetron sputtering.The film strcture and morphologyhave been characterized using the X-ray diffraction analyzer(XRD) and atomic forcemicroscope(AFM).The influence of nitrogen:argon、 sputtering power、 target-substratedistance、nitrogen process and deposition time on the AlN thin films preparation has beenstudied.Finally,we have optimized the sedimentary parameters of AlN depositing on polisheddiamond substate.All in all,high quality diamond films and AlN(002) thin films have been successfullyprepared in the optimization technology conditions,which lay a good foundation oftechnology and material for the further research of SAW devices.