Influences of a crystalline seed layer during atomic layer deposition of SrTiO₃ thin films using Ti(O-iPr)₂(thd)₂, Sr(thd)₂, and H₂O

In situ crystallized ∼20 nm thick SrTiO₃ (STO) thin films were deposited by atomic layer deposition at a growth temperature of 370°C using a 3 or 5 nm thick crystalline STO seed layer before depositing the main layer. The influences of the annealing temperature used to crystallize the seed layer on the structure and electrical properties of the entire STO film were investigated. There was an optimum annealing temperature (650-700°C) for achieving the optimum electrical performance. When the annealing temperature was <600°C, the crystallization of the seed layer was weak, and this resulted in poor in situ crystallization of the main-layer STO. On the other hand, annealing temperatures > 750°C induced adverse chemical interactions between the seed STO and Ru electrode, which inhibited in situ crystallization of the main layer when the seed-layer thickness was 3 nm. A slightly thicker seed layer (5 nm) was necessary for achieving a well-crystallized STO film when the seed annealing temperature was 750°C.