Reaction mechanism of ZrCl/sub 4/ with Ge/Si(100)-(2/spl times/1): A density functional theory study of initial stage of ZrO/sub 2/ atomic layer deposition on SiGe alloy surface

The reaction mechanism of ZrCl/sub 4/ adsorption and dissociation on Ge/Si(100)-(2/spl times/1) surface is investigated with density functional theory. The Si-Si, Si-Ge and Ge-Ge one-dimer cluster models are employed in the calculation to represent Ge/Si(100)-(2/spl times/1) surface with different Ge composition. The reaction of ZrCl/sub 2/ with hydroxylated Ge/Si(100)-(2/spl times/1) surface forms a bridged ZrCl/sub 2/ site, while on H-passivated surface ZrCl/sub 3/ site is formed. The reaction energy barrier of ZrCl/sub 2/ with H-passivated SiGe surface is much higher than ZrCl/sub 4/ with hydroxylated SiGe surface, which indicates that the reaction proceeds more slowly on H-passivated surface than on OH-terminated surface. The adsorbates and products on Ge-Ge dimer cluster model of Ge/Si(100)-(2/spl times/1) are most stable while structures on Si-Si dimer cluster model are least stable.