Electrical property improvements of yttrium oxide-based metal-insulator-metal capacitors

We investigate the effects of the thickness reduction and specific postannealing treatments in order to improve the electrical properties of yttrium oxide-based metal-insulator-metal (MIM) capacitors. The films were grown on Si∕TiSi2∕TiN substrates at 350°C by a low temperature process (pulsed liquid injection plasma-enhanced metal organic chemical vapor deposition). Although the thickness reduction leads to an increase of the capacitance density, the other electrical characteristics (the voltage linearity, the leakage currents, and the voltage breakdown) are seriously deteriorated due to the augmentation of the electric field. Low thermal budget annealing posttreatments (⩽450°C) were carried out in a gas flux (Ar, O2, and H2) and under an ultraviolet (UV) radiation (O2 and N2). We demonstrate that the UV-O2 annealing treatment is particularly efficient in improving the voltage linearity, the leakage currents, and the electric field breakdown. The improved electrical properties after the UV-O2 annealing can be related to chemical modifications (organic content reduction and oxygen content increase). The voltage linearity improvement is most likely due to the presence of a residual oxidized silicon ultrathin layer on the top surface of the yttrium oxide films. Thus, a UV-O2 annealing is an effective postdeposition treatment that is compatible with the low thermal budget, which is required for MIM applications.