Experimental formation and mechanism study for super-high dielectric constant AlOx/TiOy nanolaminates

Super-high dielectric constant (k) AlOx/TiOy nanolaminates (ATO NLs) are deposited by an atomic layer deposition technique for application of next-generation electronics. Individual multilayers with uniform thicknesses are formed for the ATO NLs. With the increase of AlOx content in each ATO sublayer, the shape of Raman spectrum has a tendency to close to that of the single AlOx layer. Effects of ATO NL deposition conditions on electrical properties of the met-al/ATO NL/metal capacitors are investigated. Lower deposition temperature, thicker ATO NL, and lower TiOy content in each ATO sublayer can lead to lower leakage current and smaller loss tangent at 1 kHz for the capacitors. Higher deposition temperature, larger number of ATO in-terface, and higher TiOy content in each ATO sublayer are important to obtain higher k values for the ATO NLs. With the increase of resistance for the capacitors, the ATO NLs vary from semi-conductors to insulators and their k values have a decrease tendency. For most of the capacitors, the capacitances reduce with the increment of absolute measurement voltage. There are semi-circular shapes for impedance spectra of the capacitors. By fitting them with the equivalent circuit, it is observed that with the increase of absolute voltage, both parallel resistor and capacitance decrease. The variation of the capacitance is explained well by a novel double-Schottky electrode contact model. The formation of super-high k values for the semiconducting ATO NLs is possibly attributed to the accumulation of charges.