An Important Failure Mechanism in MOCVD (Ba,Sr)TiO₃ thin Films: Resistance Degradation

Abstract

We have investigated the intrinsic resistance degradation behavior of fiber-textured MOCVD (Ba,Sr)TiO 3 thin films appropriate for use in advanced DRAMs and integrated decoupling capacitors, as a function of applied voltage polarity, thickness, temperature, and dc bias/field. The results suggest that there is a significant stoichiometry effect on the measured resistance degradation lifetimes. The measured degradation lifetime increases as the Ti content is increased from 51.0 to 52.0 at%Ti, and then decreases with higher at%Ti. Predicted resistance degradation lifetimes obtained from both temperature and voltage extrapolations to DRAM operating conditions of 85°C and 1.6 V exceed the current benchmark of 10 years for all of the films studied.

(Ba,Sr)TiO3 dielectrics for future stacked- capacitor DRAM

“…Most experimental studies show that the onset of resistance degradation occurs before TDDB [45][46][47]. There are various failure modes possible for BSTO thin-film devices, including time-dependent dielectric breakdown (TDDB) and resistance degradation.…”

Oxygen vacancy migration and time-dependent leakage current behavior of Ba0.3Sr0.7TiO3 thin films

“…4 It is likely that a similar effect is responsible for the long-term degradation of thin films. 5,6 Several authors associate imprint 7 and fatigue 8,9 with the long-term migration of oxygen vacancies. In addition, a current transient prior to the resistance degradation, also referred to as hump, was observed.…”