Solution chemistry optimization of sol-gel processed PZT thin films

摘要

We have optimized the ferroelectric properties and microstructural characteristics of sol-gel PZT thin films used in a CMOS-integrated, 256 bit ferroelectric non-volatile memory. The sol-gel process utilized in our work involved the reaction of Zr n-butoxide, Ti isopropoxide, and Pb (IV) acetate in a methanol/acetic acid solvent system. A 10-factor screening experiment identified solution concentration, acetic acid addition, and water volume as the solution chemistry factors having the most significant effects on the remanent polarization, coercive field, ferroelectric loop quality, and microstructural quality. The optimal values for these factors were determined by running a 3-factor uniform shell design, modeling the responses, and testing the models at the predicted optimal conditions. The optimized solution chemistry generated 3-layer, 300--400 nm thick films on RuO(sub 2) coated silicon substrates with coercive fields of less than 25 kv/cm (a 40--50% improvement over the original solution chemistry), a remanent polarization of 25--30 (mu)C/cm, and a reduction in the pyrochlore phase content below observable levels.