Improvement of Electrical Properties of $\hbox{Ba}_{{\bf 0.7}}\hbox{Sr}_{\bf 0.3}\hbox{TiO}_{\bf 3}$ Capacitors With an Inserted Nano-Cr Interlayer

Abstract

The metal-insulator-metal (MIM) capacitors were prepared with Ba0.7Sr0.3TiO3/Cr/Ba0.7Sr0.3TiO3 (BST/Cr/BST) dielectric and Pt electrode. The multilayer BST/Cr/BST was sputtered onto Pt/Ti/SiO2/Si substrate. The presence of nano-Cr interlayer affects the electrical properties of the capacitors. The temperature coefficient of capacitance (TCC) of capacitors with 2 nm Cr is about 69% of that of capacitors without Cr. In a previous work, the formation of the TiO2 secondary phase was found after the BST/Cr/BST dielectrics were annealed at 1023 K in O2 atmosphere for 1 h. It is suggested that the nano-Cr interlayer as a catalyst leads to the TiO2 formation during the annealing in O2 atmosphere. The negative value of TCC of BST can be compensated by the positive TCC of TiO2, and the temperature stability in the dielectric constant can be realized for capacitors with nano-Cr interlayer. The voltage stability of BST is also improved with the insertion of nano-Cr interlayer, and the quadratic coefficient in voltage coefficient of capacitance (VCC) of Pt/BST/Cr(2 nm)/BST/Pt is about 30% of that of the BST capacitor without Cr. The effects of Cr thickness on TCC, VCC, dissipation factor, and leakage current density of Pt/BST/Cr/BST/Pt parallel plate capacitors are investigated.