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

The metal-insulator-metal (MIM) capacitors were prepared with Ba_0.7Sr_0.3TiO₃/Cr/Ba_0.7Sr_0.3TiO₃ (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.