Study On Dry Etching Of LiTaO₃ And LiNbO₃

Lithium tantalate（LiTaO₃）and lithium niobate（LiNbO₃）have excellent properties,such as pyroelectric,photoelectric,piezoelectric and so on,which have great research value and wide application space.In addition to the preparation of excellent LiTaO₃and LiNbO₃materials,the micro patterning has become one of the key technologies.Therefore,the research on the micro patterning of LiTaO₃and LiNbO₃has important theoretical significance and practical value for the development of device preparation technology.The main work of this paper is as followsFirst of all,the ICP power,RIE power,total gas flow,Ar/（Ar+CHF₃）gas ratio on the etching speed and etching selection ratio of LiTaO₃and LiNbO₃were studied.The detailed rules were obtained.Two excellent etching processes with high etching speed,high selection ratio and low roughness were found.The results were up to 1.3μm.The surface morphology after etching was characterized.Then the full spectrum,narrow spectrum and surface atomic content of LiTaO₃before etching,after etching and after Ar+physical bombardment were analyzed by XPS.Through the analysis of the full spectrum,it can be seen that there are F-rich precipitates on the surface after etching,and the F-rich precipitates are removed after Ar+physical bombardment,which indicates that Ar+physical bombardment is effective for accelerating the etching speed.By analyzing the narrow spectrum of each element,it is found that the binding energies of Li_1s,Ta_4fand O_1sare shifted to the high-energy end after etching.These chemical shifts reflect the chemical reaction between Li,Ta and O atoms in LiTaO₃and active F-based plasma.It can be inferred that Li-O and Ta-O bonds are broken and new Li F is formed,Ta-O-F bond,and according to the narrow spectrum of Ta_4f,the peak area decreases after etching,it is speculated that Ta F₅is easy to volatilize,while Li F and Ta_xO_yF_zhave high melting points and are difficult to volatilize,which will adhere to the etching surface and hinder the further etching reaction.Ar+physical bombardment can effectively remove these difficult volatile substances.By analyzing the atomic content of LiTaO₃surface,the above viewpoint is further explained.Finally,the etching cavity is simulated by COMSOL software,and the effects of power and gas pressure on electron concentration distribution,Ars concentration distribution and electron temperature distribution are studied.It is verified that the increase of ICP power can improve the electron concentration and Ars particle concentration in the etching cavity,and further explain the reason that the increase of ICP power will lead to the increase of etching speed in the etching process of LiTaO₃and LiNbO₃.At the same time,it is concluded that the concentration in the center of the cavity is larger,and the concentration at the edge of the cavity is smaller,The sample needs to be placed in the center of the cavity to obtain the best etching effect.