Reliability Comparison of ZrO2-Based DRAM High-k Dielectrics Under DC and AC Stress

In this paper, the time dependent dielectric breakdown behavior is investigated for production type crystalline ZrO
₂
-based thin films under dc and ac stress. Constant voltage stress measurements over six decades in time show that the voltage acceleration of time-to-breakdown follows the conventional exponential law. The effects of ac stress on time-to-breakdown are studied in detail by changing the experimental parameters including stress voltage, base voltage, and frequency. In general, ac stressing gives rise to a gain in lifetime, which may result from less overall charge trapping. This trap dynamic was investigated by dielectric absorption measurements. Overall, the typical DRAM refresh of the capacitor leads to the most critical reliability concern.