Preparation And Properties Of The Surface Acoustic Wave Devices Research

Surface acoustic wave device has some characteristics, such as miniaturization,multifunction,high frequency,high reliability,digital output and so on. So surface acoustic wave device is widely used in many kinds of electronic systems of military and civil, such as mobile communications,aviation and spaceflight,radar,electronic counterwork,telecontrol and telemetry,television and so on. Surface acoustic wave device has great potential in application and wider foreground in development, so it is significative to investigate surface acoustic wave device.The fabricate technology of surface acoustic wave device is mainly explored in this paper, at the same time oscillator consisted by surface acoustic wave device is investigated. It is mainly to fabricate high quality piezoelectric substrate and design interdigital transducers which are used to bestir and detect signals for surface acoustic wave device. It is mainly to focus investigation on design and simulation of circuit for oscillator.PZT piezoelectric thin film was chosen as piezoelectric material layer of surface acoustic wave device, multilayer structure of Au/Cr/SiO2/Si was adopted as substrate. It was successful to fabricate PZT piezoelectric thin film which was dense and crackless by appending adhesive named polyvinylpyrrolidone, and the PZT film had better tropism by XRD testing. Some key problems were investigated during the fabrication processes of PZT piezoelectric thin film, such as excess of lead, concentration of adhesive and so on. When the anneal temperature was at 700℃, the experiment proved that without adhesive there was no loss of lead in PZT thin film. Concentration of adhesive was selected between 0.001 mol/L and 0.0015mol/L by repeat experiments in order to ensure that PZT thin film was crackless and had definite thickness. At last, electric characteristics of PZT thin film were investigated, such as P-E hysteresis loop-line,piezoelectric coefficient and dielectric constant: Pr=25μc/cm~2, Ec=25KV/cm; d 33 ( eff )=210pC/N;εr=1130F/m.The mainly parameters of interdigital transducers (IDT) contain pairs of fingers of IDT(N),length of period(P),width of finger(d),distance between neighbour fingers(b),aperture(w),distance between the centers of the IDT(L) and so on. Each parameter was analyzed in theory in this paper. According to existing technology condition in laboratory, the layout of IDT was designed, and the width of finger was 10μm. Ultrafine-grain plate was adopted to make edition in experiment, but quality of edition was disqualification, so chromium edition was offered by 47 research institute. Photolithography technology was improved in detail in laboratory, and surface acoustic wave device was successful made. When the IDTs were tested by SEM, it was found that the width of finger was nearly 12μm, and the distance between neighbour fingers was nearly 8μm. They were different from the design values, the reasons which may cause the differences were analyzed in this paper.Design and simulation of oscillator were investigated in this paper, it contained some problems such as the surge condition of oscillator, analysis of circuit's structure and so on.