Capacitance and admittance spectroscopy analysis of hydrogen-degraded Pt/(Ba, Sr)TiO3/Pt thin-film capacitors

Abstract

One of the problems occurring in conjunction with the integration of Ba0.7Sr0.3TiO3 (BST) thin film capacitors into the Si technology is the large increase of leakage current after a forming gas heat treatment. In order to reveal the underlying mechanism, we studied the electric properties of Pt/BST/Pt (metal–insulator–metal) (MIM) structures after annealing in atmospheres containing hydrogen (H2) or carbon monoxide by means of admittance spectroscopy. Frequency-dependent capacitance measurements on these MIM structures revealed a thermally activated relaxation step at low frequencies with an activation energy of 0.62 eV. Admittance spectroscopy, in which the conductance is monitored as a function of temperature and frequency, verifies the Schottky barrier heights at the Pt/BST interface revealed by dc measurements. We found that the Schottky barrier height decreased by 0.4 eV after annealing in a reducing atmosphere, independent of the presence of protons.