Recovery of forming gas damaged Pb(Nb, Zr, Ti)O3 capacitors

We report on the recovery of fully integrated Pb(Nb, Zr, Ti)O3 ferroelectric capacitors damaged during forming gas (4% H2, balance N2) annealing. The capacitors were encapsulated using TiOx and SiO2 as interlevel dielectrics to prevent any loss of oxygen or lead. Hydrogen, however, diffused into the ferroelectric film leading to the loss of ferroelectricity. To recover the properties of the capacitor, the fully integrated structure was annealed in N2 ambient to drive the hydrogen out. Raman scattering experiments performed in the high frequency regime to detect the [OH-] stretching vibration mode confirmed the removal of hydrogen after annealing in N2. The ferroelectric properties, including polarization and resistivity of the capacitors, were restored to their initial values prior to damage. This shows that the process of hydrogen damage is reversible with the time to recovery being dependent on the amount of hydrogen in the forming gas. © 2000 American Institute of Physics.