Research On Manufacturing Technology Of SAW Devices Based On POS Substrate

Lithium niobate (LiNbO3) is often used for the piezoelectric layer of the surface acoustic wave (SAW) device. Because the thickness of LiNbO3wafer is usually much larger than the required thickness of the SAW device, it is difficult to meet the demand for hybrid integration. In the thesis, the author proposes the surface acoustic wave device which is based on a POS (Piezoelectrics on Silicon) substrate, and achieves the SAW device with a high degree of integration.Bonding, thinning and polishing techniques are used to process LiNbO3wafer, then the POS substrate and the SAW device based on a POS substrate are manufactured. Main research contents of this paper focus on bonding technologies for LiNbO3wafer and SiO2, thinning and polishing techniques for LiNbO3wafer, producing and testing for SAW device based on a POS substrate. The results are as follow.(1) To bond LiNbO3wafer and SiO2, bonding technologies for the polyimide (PI), benzocyclobutene (BCB) and anodic were studied. After comparing the test results of the bonding quality, the BCB bonding technology was selected as the best choice. The bonding strengths of several samples were tested in experiment and the average shear force was43.85N, and the pass rate was95%.The optimized experimental parameters of BCB bonding technology are as follows:the warming slope is1K/s. Bonding temperature are100℃for120s,150℃for120s,200℃for120s, natural cooling. The pressure for bonding is20N.(2) Thinning and polishing techniques for LiNbO3wafer were studied. Grinding was used to thin LiNbO3wafer. After thinning, the LiNbO3wafer samples were polished by chemical mechanical. The polishing pad, the polishing disc speed, the pressure and the polishing time were studied in the sense of influencing the polishing process. The polishing results show that the best polishing process parameters are that the polishing cloth is chosen, the polishing liquid is SiO2for100nm, revolving speed for120r/min, pressure for3.9N, polishing time for40min, the best thickness of testing samples for80μm, and the best roughness for Ra=0.468nm, Rq=0.593nm.(3) According to the nature and principle of the surface acoustic wave devices, the design and craftsmanship of the SAW devices were studied. The SAW delay line devices with a center frequency of100MHz and200MHz were designed, and the testing work for the performance parameters of the SAW devices was completed. The test showed that the operating frequency of the SAW device based on the POS substrate increases by3%to10%.