Yasutoshi Okuno

Stabilization of ultra-thin Pt bottom electrode for 0.15 μm cup-type BST capacitor

Abstract Structural properties and electrical properties of the ultra-thin Pt film on the cup-type structure were studied. We found that Pt film was segregated inside the cup-type structure after oxygen ambient anneal above 400 °C. For the cup-type structure, the segregation was occurred by Pt migration from bottom part of the cup structure, the thinner area, to top part of the cup structure, the thicker area. To overcome this Pt segregation issue, we developed a post-anneal sequences using hydrogen ambient. With the optimized post-anneal sequence, hydrogen anneal above 500 °C, was be able to prevent from the segregation of Pt thin film for bottom electrodes of the cup structure. It was confirmed that the Pt bottom electrode annealed in hydrogen ambient did not degrade the electrical properties of the BST film. In addition, using this novel anneal sequence, 0.15 μm cup-type BST capacitor was demonstrated the leakage current of 1 fA/cell and capacitance density of 12 fF/cell.