Atomic Layer Deposition of Hafnium Silicate Thin Films Using Tetrakis(diethylamido)hafnium and Tris(2-methyl-2-butoxy)silanol

Hafnium silicate films were grown by atomic layer deposition using the liquid precursors tetrakis(diethylamido)hafnium (TDEAH) and tris(2-methyl-2-butoxy)silanol, [CH(3)CH(2)C(CH(3))(2)O](3)SiOH (TMBS). Using in situ ellipsometry, ex situ high resolution transmission electron microscopy (HRTEM), medium energy ion scattering (MEIS), and X-ray photoelectron spectroscopy (XPS), the details of the film thickness and composition were examined as functions of both the substrate temperature and silanol pulse time. Both HRTEM and MEIS measurements revealed that the films comprised two layers, with the surface layer containing more Hf than the layer in contact with the substrate. A self-limiting growth with a rate similar to 1 ML/cycle was observed only after several initial cycles, a behavior that is ascribed to the chemistry of the initial Si substrate surface. Hf 4f XPS confirmed that the films were stoichiometric Hf(x)Si(1-x)O(2) throughout despite the nonconstant Hf concentration with depth. A reaction mechanism between TDEAH and TMBS is proposed.