ELECTRICAL CHARACTERISTICS OF SRBI2TA2O9 CAPACITOR AFTER ALUMINUM METALLIZATION

The electrical characteristics of ferroelectric SrBi2Ta2O9 capacitors, after patterning Al interconnects on them, were investigated to deter mine the causes of the characteristic degradation occurring with metal lization. The Al interconnect structures were patterned using various Al etching times (overetching: 5, 30; 60, and 75%) and etching methods lion milling and reactive ion etching (RIE)). The current-voltage (I- V) characteristics degraded significantly although the capacitors were covered with a Pt top electrode and interdielectric SiO2. It was foun d that overetching is the dominant factor responsible for the degradat ion of the I-V characteristics occurring with metallization. Stress in the ferroelectric film and charge-up effects were also investigated a s causes of degradation by bending wafers and cutting off the neutrali zer during ion-milling, but it was found that neither of these were si gnificant causes of degradation. Furthermore, uniform I-V characterist ics with very slight degradation were obtained by cutting off the neut ralizer. Recovery of the degradation was attempted by annealing in N-2 ambient, but no improvement in the I-V characteristics of the capacit ors was obtained.