Effects of Post-Annealing on the Conduction Properties of Pt/(Ba, Sr)TiO3/Pt Capacitors for Dynamic Random Access Memory Applications

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Abstract
Pt/(Ba, Sr)TiO3/Pt capacitors were fabricated on TiN/Ti/ Poly–Si/SiO2/Si substrate by sputtering technique and effects of post-annealing conditions on the current vs. voltage ( I–V ) characteristics of the capacitors were investigated. It was found that leakage currents of Pt/BST/Pt capacitors were greatly depended on the annealing sequence as well as annealing atmosphere. BST films annealed under Ar/H2 or N2 showed much higher leakage current than as-deposited films regardless of the fabrication of top electrode. On the contrary, annealing under O2 atmosphere was effective to reduce leakage currents of the BST films if annealing process was carried out after fabrication of top electrode. Leakage current of Pt/BST(50 nm)/Pt capacitors annealed under O2 atmosphere at 500° C for 1 h after fabrication of Pt top electrode was 5×10-7 A/cm2 even at 7 V. In this work, effects of annealing conditions on the I–V properties of Pt/BST/Pt capacitors were explained with energy band diagram in which oxygen vacancies play a key role.