Improved interfacial and electrical properties of Ge MOS capacitor with ZrON/TaON multilayer composite gate dielectric by using fluorinated Si passivation layer

A Ge metal-oxide-semiconductor capacitor with a composite gate dielectric composed of a ZrON/TaON multilayer and a Si passivation layer treated with fluorine plasma is fabricated. Its interfacial and electrical properties are compared with those of its counterparts without the Si passivation layer or the fluorine-plasma treatment. Experimental results show that the device with the fluorinated Si passivation layer exhibits excellent interfacial and electrical performances: low interface-state density (2.0 × 10¹¹ cm² eV^-1 at midgap), small flatband voltage (0.17 V), low gate leakage current (2.04 × 10^-6A/cm² at V_g = V_fb + 1 V), and high equivalent dielectric constant (22.6). The involved mechanism lies in the fact that the TaSiON interlayer formed by mixing of TaON and Si passivation layers can effectively suppress the growth of unstable Ge oxides to reduce the defective states at/near the TaSiON/Ge interface. Moreover, the fluorine-plasma treatment can passivate the oxygen vacancies and conduce to the blocking of elemental inter-diffusions, thus largely improving the interfacial quality to achieve excellent electrical properties for the device.