Atomic Layer Deposition of GeTe and Ge–Sb–Te Films Using HGeCl₃, Sb(OC₂H₅)₃, and {(CH₃)₃Si}₂Te and Their Reaction Mechanisms

In this paper, a new atomic layer deposition (ALD) process for depositing binary GeTe and ternary Ge–Sb–Te thin films is reported, where HGeCl 3 and ((CH 3 ) 3 Si) 2 Te were used as Ge and Te precursors, respectively. The precursors reacted together to form the films at a low substrate temperature of 50–100 °C, without involving any additional reactive process gas. HCl elimination from the Ge precursor to form the divalent Ge intermediate, GeCl 2, is proposed to explain the formation of 1:1 composition stoichiometric GeTe films. The GeTe films are promising for use in phase change memory applications. Ternary Ge–Sb–Te films were deposited by combining the GeTe ALD process with a previously developed ALD process for Sb 2 Te 3 films, where Sb(OC 2 H 5 ) 3 and ((CH 3 ) 3 Si) 2 Te were employed respectively as the Sb and Te precursors. However, the composition of the ternary GeSbTe films deviated slightly from the desired GeTe–Sb 2 Te 3 pseudobinary composition suggesting that a certain unwanted reaction was involved between the previously grown layer and incoming precursor molecules. Study of the mechanism revealed that reaction between the Ge precursor and the previously deposited Sb–Te layer caused a substantial portion of Sb to be removed from the Sb–Te layer as volatile SbCl 3 .