Resistive switching characteristics of MIM structures based on oxygen-variable ultra-thin HfO2 and fabricated at low temperature

We report the resistive switching characteristics of Metal-Insulator-Metal (MIM) structures fabricated at low temperature and having different concentrations of oxygen vacancies in the insulator. The oxygen modulation in HfO2 is promoted by a very simple variation of standard thermal Atomic-Layer Deposition (ALD), so that different exposure times to H2O during each half-cycle of the hafnium oxide deposition are used (being Tetrakis Dimethylamino Hafnium TDMAH the other precursor). We show the correlation of the stoichiometry with the forming voltage, conduction mechanisms and resistance windows of memory devices. All structures present a bipolar operation mode in which the resistive switching mechanism is related to the migration of oxygen vacancies inside the dielectric. These MIM devices have a simple structure, low power consumption and they are fabricated using a very low thermal budget of only 250 degrees C, thus enabling their integration at the Back-End of Line (BEOL) stage of an integrated circuit in order to increase the density of memory arrays in at least one order of magnitude.