ALD approach toward electrodeposition of Sb₂Te₃ for phase-change memory applications

Abstract

This paper describes various studies undertaken to devise a deposition cycle for the formation of Sb2Te3, a phase-change memory material, by electrochemical atomic layer deposition (EC-ALD). The importance of deposition potentials to the formation of deposits of Sb and Te, were investigated. The resulting potentials were then used in an EC-ALD cycle to form deposits one atomic layer at a time, using a sequence of surface limited reactions. The optimal deposition potentials for the Sb2Te 3 EC-ALD cycle, on a Au substrate, consisted of -0.22 V for Sb deposition, and -0.35 V for Te. Bulk Te stripping at was performed at -0.70 V. The conditions using a TiN substrates included Sb deposition at -0.20 V, Te deposition, and bulk stripping at -0.35 and -0.70 V, respectively. The deposits obtained were stoichiometric, with a TeSb atomic ratio of 1.5 from electron probe microanalysis. Glancing angle X-ray diffraction studies showed a (015) preferred orientation for the deposit. Sb2Te3 was shown to grow successfully on patterned TiN substrates with 200 nm vias. © 2008 The Electrochemical Society.