Reduction of the hydrogen degradation in SrBi2(Ta1−xNbx)2O9 by TiN barrier metal

Abstract

The use of ferroelectric SrBi2(Ta1−xNbx)2O9 (SBTN) as a mainstream form of nonvolatile memory requires that the degradation of its electrical qualities that is caused by annealing in a hydrogen atmosphere be reduced. Titanium nitride (TiN) is a candidate for use as a barrier-metal layer against hydrogen diffusion. The relationship between the degradation in the qualities of SBTN and the quality of the TiN barrier metal has been investigated. TiN when sputtered onto SBTN capacitors creates a good barrier under all sputtering conditions, and maintains the electrical characteristics of the SBTN through annealing in an atmosphere of H2. Higher density TiN films provide more effective protection. The characteristics of the degraded capacitor were investigated in terms of its current-voltage characteristic. Remanent polarization can be recovered from, at least partially, by applying a series of bipolar pulses. This rejuvenation of the electrical qualities indicates that degradation arises from a combination of electrical and structural faults.

Hydrogen-Sensitive Amorphous Ferroelectric Thin Film Capacitive Devices

“…It is interpreted as a built-up interface potential induced by the hydrogen and in turn the lowering of the Schottky barrier height [26,27]. Several consistent results and mechanisms have been published by NEC [30][31][32][33], Fujitsu [34,35], Hyundai [36,37], Argonne National Laboratory [38][39][40], etc. Meanwhile, several technical routines have been proposed to avoid such hydrogen damage in actual LSI/ULSI fabrication processes [31,32,35,36,[41][42][43].…”