Wet oxidation growth of hafnium doped tantalum oxide films with different composition deposited on silicon substrate

Abstract

As-deposited Ta-HfO2 films produced via co-sputtering using different Ta sputtering powers (120, 150, and 180 W) with a fixed HfO2 power (160 W) were transformed to ternary HfxTayOz films after wet oxidation at 800 °C. An increase in the Ta sputtering power encouraged amorphous to crystalline phase transformation. Crystallization has assisted film growth but densification happened in the film sputtered at 180 W, yielding a reduction in thickness. Results indicated that formation of thick TaSiOx-rich interfacial layer (IL) at the interface has triggered the thickest film at 150 W while a thinner SiOx-rich IL was formed in the film at 180 W. Changes in dielectric constant with respect to the IL thickness were reported. The decrease in IL formation at 180 W was due to accumulation of nitrogen at interface for nitridation. Dissimilar from that at 150 W, a higher amount of oxygen vacancies would trap the nitrogen species, decreasing the nitridation activity. The trapping of nitrogen happened together with H2, affecting passivation capability of interface defects. Corresponding changes in trap density were discussed.