Atomic Layer Deposition of GeTe Films Using Ge{N[Si(CH₃)₃]₂}₂, {(CH₃)₃Si}₂Te, and Methanol

In this report, a new method to deposit GeTe thin film by atomic layer deposition (ALD) is described. Ge(N(Si(CH 3 ) 3 ) 2 ) 2, in which Ge is in +2 oxidation state, and ((CH 3 ) 3 Si) 2 Te were used as Ge and Te precursors, respectively. GeTe films were deposited at a low wafer temperature of 70–120 °C. To improve low reactivity of Ge(N(Si(CH 3 ) 3 ) 2 ) 2 toward ALD-type reaction with ((CH 3 ) 3 Si) 2 Te, methanol vapor was coinjected with the Ge precursor and the Te precursor to form a reactive Ge intermediate having methoxy ligands and a Te intermediate having hydrogen ligands in the gas phase. This chemistry-specific ALD process deposited films various compositional GeTe alloys including the desired composition of Ge:Te = 1:1. Detailed mechanism study on the probable chemical reactions and film composition analysis revealed that the film growth could proceed via the formations of GeTe 2, GeTe, and Ge 2 Te phases depending on the relative Ge-precursor concentration during the ALD process. The films showed feasibility for phase-change memory applications.