The charge trapping effect of metal-ferroelectric (PbZr0.53Ti0.47O3)-insulator (HfO2)-silicon capacitors

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Abstract
Metal-ferroelectric-insulator-semiconductor (MFIS) capacitors with a Pb(Zr0.53,Ti0.47)O3 ferroelectric layer and a hafnium oxide insulator layer have been fabricated and characterized. The size of the capacitance-voltage memory windows was investigated. The memory window first increases to a saturated value of 0.7V with the sweep voltage and then decreases due to charge injection. The oxide trapped charges in the ferroelectric∕insulator layers are studied by a voltage stress method. The flatband voltage (VFB) is measured before and after the voltage stress. The ΔVFB is 0.59V at a negative stress voltage pulse of −5V for 30s. The ΔVFB under positive voltage stress was much less and was 0.06V at a stress voltage of +5V for 5min. The energy-band diagram of the MFIS structure at inversion and accumulation modes are plotted and the VFB shift can be explained by the trapping or detrapping of charges. The current-density versus stress time (J-t) characteristics were also measured. The result is consistent with the charge trapping model.