Effects of post-annealing on the conduction properties of Pt/(Ba,Sr)TiO3/Pt capacitors for dynamic random access memory applications

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/H-2 or N-2 showed much higher leakage current than as-deposited films regardless of the fabrication of top electrode. On the contrary, annealing under O-2 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(50nm)/Pt capacitors annealed under O-2 atmosphere at 500 degrees C for Ih after fabrication of Pt top electrode was 5 x 10(-7) A/cm(2) even at 7V. 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.