Nanostructured surfaces

Nanosized relief formation on the PbTe and Pb1-хSnхTe crystal surfaces during chemical-mechanical polishing
G.P. Malanych, V.M. Tomashyk
V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, 41 Nauky Ave., Kyiv, 03028,Ukraine. 
E-mail: galya.malanich@gmail.com

Method of high quality polishing surfaces formation of PbTe and Pb1-хSnхTe single crystals by chemical-mechanical polishing (CMP) using developed by us new effective polishing etchants with a wide range of etching rates has been developed. Bromine emerging etchants are one of the most effective polishing solutions. The research was carried out on PbTe and Pb0.83Sn0.17Te, Pb0.8Sn0.2Te single crystal plates grown by Bridgman method.
Samples were cut from the central part of the ingots across their growth direction on a semiconductor cutting machine using a wire saw (with a layer of ~40-μm abrasive grains). After cutting, the resultant semiconductor wafers were 5×7×1.5 mm in dimensions. The cutting-induced surface deformation layer was partially removed by mechanical grinding with aqueous slurries of M10 to M5 and ASM 1/0 abrasive powders. The disturbed during cutting and grinding layer with the thickness of 100-150 μm was removed by CMP using etchant at a polishing rate of 185 μm/min. CMP was carried out on a glass polisher covered with lawn cloth at a continuous supply of etchant (2-3 mL/min) for 2 min and a pressure on the plates in 2-3 kPa.
The crystal dissolution rates were registered by reducing its thickness before and after etching with an electronic indicator TESA DIGICO 400. Microstructure of the plate’s surfaces after various stages of the mechanical and chemical treatments was studied using table scanning microscope JEOL JCM-5000 NeoScope. The sample surface microprofile characteristics and roughness were obtained using a profilometer HOMMEL-ETAMIC W5, which allows to determine the roughness more than 5 nm. Morphological study of the polished PbTe surface was spent on scanning probe microscope NanoScope IIIa Dimension 3000TM (Digital Instruments, USA).
New compositions of ((NH4)2Cr2O7)+НBr+EG)/GL (ethylene glycol or glycerol) polishing etchants and the treatment methods of PbTe and Pb1-хSnхTe single crystal surfaces contribute to a significant decrease in surface roughness meeting the requirements Ra < 10 nm.