Development of ferroelectric PZT thin films by the sol-gel technique for non-volatile memory applications

PZT thin films have been prepared via a sol-gel route using standard butoxide and acetate precursors. The solution compositions were modified by the addition of acetylacetone in 2 methoxyethanol, which has the effect of changing the solution complex and therefore its deposition and drying characteristics. Varying amounts of excess lead were included in some cases. The films were prepared by spin coating onto Pt/Ti electroded silicon with an intermediate barrier layer of either boron phosphate silica glass (BPSG) or thermal silicon oxide and the resulting samples subjected to a range of thermal annealing conditions in an oxidising atmosphere. Several methods have been investigated including two regimes using rapid furnace annealing (RFA) up to 700°C and slow annealing at 450°C in air. The latter method yielded highly (111) oriented and crack-free perovskite films with no evidence of other orientations, whereas the former route showed the presence of (100) and (110) orientations. The correlation between the thermal anneal method and orientation will be discussed. Surface electrode dots have been evaporated onto the film to allow electrical measurements. The ferroelectric and fatigue properties of these films have been assessed with respect to non-volatile memory applications. The implications of film quality and thermal processing on the overall ferroelectric performance will be discussed.