Self-formation of lead telluride nanostructures during argon plasma etching of single-crystal wafers

Abstract

Application of abnormally high sputtering rate of PbTe(Te) single crystals during inductively coupled argon plasma treatment for fabrication of nanostructures S P Zimin, E S Gorlachev, I I Amirov et al.Plasma sputtering of polycrystalline Pb1xSnxTe thin films grown on glass substrates using hot wall deposition S P Zimin, E S Gorlachev, V F Gremenok et al. Abstract. In this work we report a phenomenon of PbTe nano-and microstructure selfformation that takes place during dry etching of lead telluride (111)-oriented single-crystal wafers with 4 at.% excess tellurium in RF high-density low-pressure inductively coupled argon plasma. Using scanning electron microscopy and energy dispersive X-ray spectroscopy investigations it is established that during the plasma treatment high sputtering rates are accompanied by active redeposition processes on crystal surface and on the inner side of the Si etching mask resulting in a nanostructure arrays self-formation via vapour-liquid-solid mechanism. ExperimentalPbTe single-crystal ingots were grown in (111) direction using Bridgman method according to a wellestablished technique [1]. Synthesized composition had excess tellurium relative to stoichiometry of 4 at.%. The grown crystals were cut perpendicular to the growth axis in order to obtain disk wafers with the thickness of 3-5 mm, whose surface was polished with diamond paste with chemical polishing finish. Plasma sputtering (dry etching) of the surface of PbTe(Te) disks was performed using a radiofrequency high-density low-pressure inductively coupled plasma (RF ICP) treatment [2][3][4]. Power applied to the inductor of the plasma reactor was 800 W, RF bias power at the substrate was varied in the range of 100-300 W, self-bias negative potential was 85-195 V, argon flow rate was 10 sccm. Series of consecutive surface treatments were carried out with a change in the duration (10-60 s) and bias power. During treatment stencil Si masks with native oxide and 0.6 μm thick SiO2 layer were used, with a typical microgap between the sample and Si surfaces being 1-10 μm. The morphology was studied with scanning electron microscopy (SEM) using Supra 40 Carl Zeiss microscope and local elemental composition was determined from energy dispersive X-ray (EDX) data using INCAx-act Oxford Instruments spectrometer. Results and discussions