The charge trapping effect of metal-ferroelectric (PbZr_0.53Ti_0.47O₃)-insulator (HfO₂)-silicon capacitors

Metal-ferroelectric-insulator-semiconductor (MFIS) capacitors with a Pb(Zr_0.53,Ti_0.47)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 0.7 V 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 (V_FB) is measured before and after the voltage stress. The ΔV_FB is 0.59 V at a negative stress voltage pulse of -5 V for 30 s. The ΔV_FB under positive voltage stress was much less and was 0.06 V at a stress voltage of +5 V for 5 min. The energy-band diagram of the MFIS structure at inversion and accumulation modes are plotted and the V_FB 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.