Integration of a split word line ferroelectric memory using a novel etching technology

A ferroelectric random access memory (FeRAM) was fabricated using a novel p rocessing technology to investigate the characteristics of the FeRAM with a new cell structure. The new cell includes two split word lines (SWL's) whi ch play roles not only as word lines but also as plate lines. This structur e can enhance operation speed and prevent the decrease of remnant polarizat ion of non-selected cell capacitors in write/read operation since SWL's can be driven independently. The cell capacitors were composed of Pt electrode s and the sol-gel derived Pb(Zr,Ti)O-3 films. An efficient procedure to rea lize the new cell structure is proposed by introducing a new etching method , which includes the one-step patterning of a metal-ferroelectric-metal (MF M) and a metal-ferroelectric (MF) using a metal mask (Ti or Ru) and an etch stopping layer (TiO2 or RuO2). The degradation of the ferroelectric capaci tors due to etching process and interlayer dielectric (ILD) deposition proc ess was almost recovered by annealing in oxygen. Memory operation was confi rmed in the 2T/2C SWL FeRAM with the capacitor area down to 16 mu m(2).