Chemical-mechanical polishing of CdTe and based on its solid solutions single crystals using HNO3 + НІ + ethylene glycol iodine-emerging solutions

Abstract

The interaction of the CdTe and Zn0.04Cd0.96Te, Cd0.2Hg0.8Te solid solutions single crystals with the iodine-emerging etchings based on aqueous solutions of HNO3 + НІ + ethylene glycol has been investigated and etching compositions have been developed and optimized, as well as methods of their chemical treatment for the formation of high-quality surface. The dissolution of these semiconductor materials in the aqueous solutions of the (HNO3+HI+EG)/EG have been investigated and dependences “etchant composition – etching rate” with determining the regions of polishing and unpolishing solutions have been constructed. It was found that the semiconductors etching rate (chemical-mechanical polishing) decreases from 73.2 to 0.5 μm/min and the polishing features of the HNO3+HI+EG etching composition improve when the EG content is increasing. The minimum value of the etching rates is achieved when the saturation of the organic component is maximum (95 vol. %). The dependences of the chemical-mechanical polishing rate on the dilution of the base polishing etchant with ethylene glycol and the surface condition after polishing have investigated using metallographic analysis and atomic force microscopy. It was established that chemical-mechanical polishing of the CdTe and Zn0.04Cd0.96Te, Cd0.2Hg0.8Te solid solutions single crystals by the (HNO3+HI+EG)/EG solutions promote decreasing of the structural damages of the substrate and obtaining the high-quality polishing surface. It has been shown that etchant compositions of HNO3+HI+ EG with EG as a solvent completely meet the requirements for CMP etchants. Treatment of the Cd0.2Hg0.8Te crystal surfaces with new etchant mixtures allows to obtain ultra-smooth surfaces Ra = 1.5 nm. The polishing etchant compositions (HNO3+HI+EG)/EG and technological procedures of the chemical mechanical polishing for the disturbed layer elimination, controlled thinning of the plates up to reference dimension, as well as the thin layers removing and CdTe single crystals and Zn0.04Cd0.96Te, Cd0.2Hg0.8Te solid solutions finishing polishing have been optimized.