Reaction Mechanism for Atomic Layer Deposition of Germanium Ditelluride Thin Films

The mechanism underlying the deposition of GeTe2 films by alternating exposures to GeCl4 and Te(Ge(CH3)(3))(2) was studied. The reaction model of ALD GeTe2 was constructed by density functional theory (DFT) calculation and verified by in-situ quartz crystal microbalance (QCM) analysis. Based on the result of the DFT calculation, the ligand-exchange reactions between the GeCl4 and Te(Ge(CH3)(3))(2) was expected to produce ClGe(CH3)(3) as the byproduct. QCM analysis at 80 degrees C indicated that a GeCl4 molecule reacts with two surface species of -Te(Ge(CH3)(3) and the surface sites are fully covered by -GeCl2 during the first half reaction, resulting in the mass decrease by GeCl4 pulse. Also, a TeGe(CH3)(3) molecule reacts with a surface species of -Ge0.5Cl and the surface sites are fully covered by -TeGe(CH3)(3) during the second half reaction. Consequently, amorphous GeTe2 film was grown by alternating exposures to GeCl4 and Te(Ge(CH3)(3))(2) , and the saturated mass increase per cycle of 20 ng/cm(2) .cycle was obtained with the saturation doses of 1.2x10(6) L for GeCl4 and 2.5x10(6) L for Te(Ge(CH3)(3))(2)