Electrical Characteristics of SrBi2Ta2O9 Capacitor after Aluminum Metallization

Abstract

The electrical characteristics of ferroelectric SrBi2Ta2O9 capacitors, after patterning Al interconnects on them, were investigated to determine the causes of the characteristic degradation occurring with metallization. The Al interconnect structures were patterned using various Al etching times (overetching: 5, 30, 60, and 75%) and etching methods (ion 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 found that overetching is the dominant factor responsible for the degradation of the I–V characteristics occurring with metallization. Stress in the ferroelectric film and charge-up effects were also investigated as causes of degradation by bending wafers and cutting off the neutralizer during ion-milling, but it was found that neither of these were significant causes of degradation. Furthermore, uniform I–V characteristics with very slight degradation were obtained by cutting off the neutralizer. Recovery of the degradation was attempted by annealing in N2 ambient, but no improvement in the I–V characteristics of the capacitors was obtained.