Hydrogen induced imprint mechanism of PT/PZT/PT capacitor by low temperature hydrogen treatment

We found that low temperature and low pressure hydrogen annealing induced a severe voltage shift (imprint) of P - V hysteresis loop of Pt/PZT/Pt capac itor. The amount of shift depended on the annealing temperature and hydroge n pressure, and was about 0.8 V at 60 degrees C, 10 min., 230 mTorr, From S IMS analyses, it was found that hydrogen accumulated at the interfaces betw een Pt and PZT after the annealing, The voltage shift increased with the in crease in hydrogen concentration at the interfaces. The accumulated hydroge n is thought to reduce the PZT film and create oxygen vacancies at the inte rfaces, which act as fixed positive charges. The shift direction indicates that an internal bias field directed toward the bottom electrode was formed in the PZT film. This indicates that the hydrogen treatment resulted in a fixed positive charge being formed mainly at the interface between the top Pt and PZT. Detailed SIMS analyses revealed that PZT near the bottom electr ode was conductive. Therefore, the oxygen vacancies in PZT near the bottom Pt do not play as fixed charges.