BREAKDOWN MECHANISMS IN PZT THIN-FILM CAPACITORS

Breakdowns of PZT thin film capacitors were demonstrated by applying i nput signals such as DC bias, square waves, triangular waves, and unip olar pulse. Effects of frequency, capacitor size, and pulse width on b reakdown were investigated in order to understand breakdown mechanisms . It was confirmed that impulse breakdown is related to rise time of t he input signal in association with charging time of the capacitors an d steady-state thermal breakdown, pulse width. Energy stored in the fe rroelectric capacitors during hysteretic cycling may be additional the rmal breakdown source. ]Electrode burst was observed which may occur d ue to thermal breakdown through grain boundaries. In addition to break down, a new leakage current test technique for FRAM application was su ggested in consideration of transient current of the capacitors. In co nclusion, breakdown is more serious and leakage current is less seriou s in FRAM applications than in DRAM applications. Finally, homogeneous polycrystalline structure or single crystal structure is recommended to minimize electrode burst.