Papers by Author: H.W. Du

Abstract: Lithium tantalite (LiTaO3) possesses a combination of unique electro-optical, acoustic, piezoelectric, pyroelectric and non-linear optical properties, making it a suitable material for applications in high frequency, broad width-band SAW and BAW components, filters in television receivers, etc. The surface quality of LiTaO3 wafers decides the performances of the devices. In this paper, the technique of chemical mechanical polishing (CMP) was used to polish LiTaO3 wafers. The influences of the polishing parameters on the CMP processes of LiTaO3 wafers were analyzed in detail based on the measurement of the material removal rate, surface roughness and topograph of the polished wafers in different polishing conditions.

Abstract: In this paper, the scratching processes by a diamond indentor under the loads linearly increased from zero were studied to assess the mechanical behavior of LiTaO3 crystal wafer. Material removal mechanism of LiTaO3 crystal by mechanical loads was analyzed based on the measured acoustic signals in the scratching processes and the observation on the scratched surfaces of LiTaO3 wafers. The chemical mechanical polishing (CMP) processes of LiTaO3 wafers were analyzed in detail according to the observation and measurement of the polished surfaces of LiTaO3 wafers with SEM and XRD. The research results show that there exist four regimes along the scratched groove with the increasing of down force in a scratching process of LiTaO3 crystal wafer, and the critical load for each regime is affected by the loading speed and final load, etc. When H2O2 and KOH are added into the polishing slurry, the material of LiTaO3 wafer is removed by chemical reaction and mechanical action sequentially in the CMP processes, and the material removal rate increases while the surface roughness is improved.