In situ mass spectroscopy of recoiled ion studies of degradation processes in211 SrBi2Ta2O9 thin films during hydrogen gas annealing

摘要

It is known that the forming gas (N(sub 2)-H(sub 2) mixture) annealing process211u001erequired for microcircuit fabrication results in an unacceptable electrical 211u001edegradation of SrBi(sub 2)Ta(sub 2)O(sub 9) (SBT) ferroelectric capacitors due 211u001emainly to the interaction of H(sub 2) with the ferroelectronic layer of the 211u001ecapacitor. We have found a strong relationship between changes in the surface 211u001ecomposition of the ferroelectric layer and the electrical properties of SBT 211u001ecapacitors as a result of hydrogen annealing. Mass spectroscopy of recoiled ions 211u001e(MSRI) analysis revealed a strong reduction in the Bi signal as a function of 211u001eexposure to hydrogen at high temperatures ((approximately)500 C). The Bi signal 211u001ereduction correlates with Bi depletion in the SBT surface region. Subsequent 211u001eannealing in oxygen at temperatures in the range of 700-800 C resulted in the 211u001erecovery of the MSRI Bi signal, corresponding to the replenishment of Bi in the 211u001epreviously Bi-depleted surface region. XRD analysis (probing the whole SBT film 211u001ethickness) showed little difference in the XRD spectra of the SBT fti before and 211u001eafter hydrogen and oxygen-recovery annealing. The combined results of the MSRI 211u001eand XRD analyses can be interpreted as an indication that the degradation of the 211u001eelectrical properties of the SBT capacitors, after hydrogen annealing, is mainly 211u001edue to the degradation of the near surface region of the SBT layer.