Experimental evaluation of the forming process of virgin HfO2 memory cells by capacitance–voltage measurements

In this Letter, we evaluate the so-called forming process of virgin HfO2 cells under ac and dc stress by capacitance–voltage measurements. It is found that the ac nonlinearity is higher than the dc one. This is related to the dispersive nature of hopping conduction according to the electrode polarization model. Under short stress times, both capacitance and current are unaffected. However, after longer stress times, no recovery is observed. Consequently, the current increases and a plateau appears in the capacitance. The observed degradation is consistent with the RRAMs-forming process. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)