In Situ Reaction Mechanism Studies on Atomic Layer Deposition of Sb₂Te₃ and GeTe from (Et₃Si)₂Te and Chlorides

Reaction mechanisms in the atomic layer deposition (ALD) of Sb 2 Te 3 from SbCl 3 and (Et 3 Si) 2 Te at 60 °C and GeTe from GeCl 2 ·C 4 H 8 O 2 (1,4-dioxane complex of GeCl 2 ) and (Et 3 Si) 2 Te at 90 °C were studied in situ with a quadrupole mass spectrometer (QMS) and a quartz crystal microbalance (QCM). Also some experiments were conducted on reactions in ALD of the phase change material GST (germanium antimony telluride, Ge 2 Sb 2 Te 5 ). The byproduct in both the binary telluride processes was found to be Et 3 SiCl, and about 78% (36%) of it was released during the SbCl 3 (GeCl 2 ·C 4 H 8 O 2 ) pulse. Obviously −Te(SiEt 3 ) surface groups serve as reactive sites for the metal precursors, cf. −OH surface groups in the oxide ALD processes that use water as the oxygen source. The dioxane, on the other hand, was expectedly found to be released entirely during the GeCl 2 ·C 4 H 8 O 2 pulse. When depositing GST the mechanism of the SbCl 3 -(Et 3 Si) 2 Te reaction was found to change so that only about 50% of the byproduct Et 3 SiCl was released during the SbCl 3 pulse. The same effect was experienced when the SbCl 3 -(Et 3 Si) 2 Te process was executed on surfaces of Al 2 O 3 and Au.