New top and bottom electrodes for SrBi2Ta2O9 ferroelectric capacitors

SBT is a candidate as the ferroelectric material for large scale FeRAMs with the great advantages of less fatigue and better squareness in its P-E hysteresis curves, while SBT has the disadvantages of higher crystallization temperature that results in difficulties realizing a stacked structure cell and greater damage to its ferroelectric properties from forming gas annealing. This paper presents new top and bottom electrodes to eliminate these disadvantages for SBT. The remanent polarization decreases only slightly after forming gas annealing with the top electrodes of partially oxidized Ru. Ru-O top electrodes show no bubbles or peeling after forming gas. In order to achieve the stacked structure cell for SBT capacitors, a new diffusion barrier was developed. This new diffusion barrier withstands the high temperature annealing that is required to crystallize SBT films. With the new diffusion barrier hysteresis curves could be obtained with electrical connections through Si substrates.