Atomic layer deposition and tellurization of Ge-Sb film for phase-change memory applications

We studied the atomic layer deposition (ALD) and the tellurization of Ge-Sb films to prepare conformal crystalline Ge-Sb-Te (GST) films and to achieve void-free gap filling for emerging phase-change memory applications. ALD Ge-Sb film was prepared by alternating exposures to GeCl₂-dioxane and Sb(SiEt₃)₃ precursors at 100 °C. The growth rate was 0.021 nm per cycle, and the composition ratio of Ge to Sb was approximately 2.2. We annealed the ALD Ge-Sb films with a pulsed feeding of di(tert-butyl)tellurium. The ALD Ge-Sb films turned into GST films by the tellurization annealing. When the tellurization temperature was raised to 190 °C or higher temperatures, the Raman peaks corresponding to Ge-Sb bond and amorphous Ge-Ge bond disappeared. The Raman peaks corresponding to Ge-Te and Sb-Te bonds were evolved at 200 °C or higher temperatures, resulting in the phase transition temperature of 123 °C. At 230 °C or higher temperatures, the entire film was fully tellurized to form a GST film having a relatively uniform composition of Ge₃Sb₂Te₆, and the carbon impurities in the as-deposited ALD Ge-Sb film were eliminated. As the tellurization temperature increases, the volume of the ALD film is expanded owing to the incorporation of tellurium, resulting in complete filling of a trench pattern by GST film after the tellurization at 230 °C.