Nanostructured surfaces

Chemical etching of InSb crystals using I2 + methanol or DMF compositions
Malanych G.P.
Semiconductor Chemistry Department, V.Ye. Lashkaryov Institute of Semiconductor Physics of the NAS of Ukraine. 
Prospect Nauki, 41, Kyiv-03028, Ukraine.
E-mail: galya.malanich@gmail.com

The quality and condition of the surface play an important role in the technology of manufacturing semiconductor devices. The chemical etching is a usual method of the cleaning and the texturing of the substrate surfaces.
InSb (112) crystals were used for the investigations. The single-crystalline ingots were cut into 25 mm2 size substrates using the string cutting with diamond coating. In order to achieve the nanosized relief, the samples were treated in the following sequence: mechanical grinding, chemical-mechanical polishing (CMP) and in-process washing (after each stage of the treatment) and chemical-dynamic polishing (CDP). 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 non-abrasive etchant. CMP was carried out on a glass polisher covered with lawn cloth at a continuous supply of etchant (2-3 ml·min–1) for 3 min and a pressure on the plates in 2-3 kPa. CDP was the finish stage of the substrate modification. It was carried out in the reproducible hydrodynamic conditions using the disk rotation method. The dissolution rate of crystals was defined using the electronic indicator TESA DIGICO 400. In-process washing of the crystals was carried out after every treatment stages in Na2S2O3 and NaOH solutions and distilled water.
The interaction between the semiconductors and the I2 + methanol or DMF etchants was studied using the CDP. It was found that in the studied concentration range (6-18 mass.% I2 in DMF) with increasing I2 content, the dissolution rate of InSb increases from 0.4 to 7.7 μm.min-1, forming a polished surface with a mirror luster. The dependence of PbTe dissolution rates in the range of concentrations of 3-15 mass.% I2 in methanol was studied. It was determined that with increasing iodine content from 3 to 12 mass.%, the dissolution rate increases from 1.8 to 9.6 μm.min-1 A further increase in the content of I2 to 15 mass.% in the etching composition leads to a decrease in the etching rate of the samples to 1.4 μm.min-1. As a result of the CDP, the polished surface is formed with Ra < 5 nm.