Comparative study of the perovskite phase microstructure evolution and electrical properties of lead zirconate titanate thin-film capacitors annealed in oxygen and nitrogen ambients

Abstract

Lead zirconate titanate [PZT, Pb(ZrxTi1−x)O3, x=0.65, 400 nm] thin-film capacitors with very low leakage current and large stored charge densities (Q′c=Pmax–Pr) for ultralarge scale integration dynamic random access memory (ULSI DRAM) memory applications have been fabricated by reactive dc magnetron sputtering followed by an annealing step. In this letter, we present a comparative study of the significant influence of the use of an oxidizing (O2) as against a nonoxidizing annealing ambient (N2) on the evolution of the perovskite phase microstructure and the electrical properties of PZT capacitors. The phase transformation kinetics are faster in a N2 annealing ambient at low temperatures, yielding capacitors with a large Q′c at low annealing thermal budgets. However, N2 annealed films exhibit a lower breakdown field and time to breakdown which is in agreement with a degradation model based on the field-induced concentration polarization of oxygen vacancies.