Huge reduction of wake-up effect in ferroelectric HfZrO2 nanostructures
Résumé
We report the fabrication of two samples deposited by magnetron sputtering with excellent performances, quite similar to samples deposited by ALD. The samples are called NM, and M. NM and M refers to two different architectures, respectively non-mesa and mesa structures. Fabrication and architecture details can be found in reference [1]. The set-up for electrical measurements have been described in reference [2, 3]. This set-up allows us to wake the samples with bipolar square pulses. Measurements are performed with a positive up negative down (PUND) sequence. Pr values are among the highest for samples deposited by sputtering. Although the N-sample and NM-samples show very close Pr values, the two samples show completely different electrical behaviors. During cycling, the increase of Pr value for the NM-sample is more than an order of magnitude higher than the M-sample. It is accompanied by a decrease of the endurance which is two order of magnitude higher for the NM-sample than for the M-sample. As electrical behaviors are not the same, for low stress conditions M-sample has a higher Pr value during cycling whereas for high stress conditions NM-sample has a higher Pr value during cycling. As a matter of fact, it has been proven that maximum Pr values are more sensitive to stress conditions than the structures themselves. The origins of the different electrical behaviors come from the micro-crystalline structures of the two samples, according to GIXRD results. The crystallization takes place during the annealing step. During annealing, M-sample is built with a TiN TE fully covering the HZO layer whereas the TiN covers only partially the HZO layer in case of the NM-sample. It induces different stress states which lead to two different micro-crystalline patterning. The M-sample shows no monoclinic peak, whereas the NM-sample shows many monoclinic orientations. It can explain the huge reduction of the wake-up effect. [1] J. Bouaziz, P.R. Romeo, N. Baboux, B. Vilquin, ACS Appl. Electron. Mater. 1, 1740 (2019). [2] J. Bouaziz, P. Rojo Romeo, N. Baboux, R. Negrea, L. Pintilie, B. Vilquin, APL Mater. 7, 081109 (2019). [3] J. Bouaziz, P.R. Romeo, N. Baboux, B. Vilquin, Appl. Phys.Lett. 118, 082901 (2021).