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Scanning force microscopy (SFM) has been used to study nanoscale variations in switching parameters in layered perovskite films of SrBi2Ta2O9 and to investigate the effect of capacitor scaling on the standard deviation of the capacitors’ integral polarization signal. Ferroelectric poling and SFM piezoresponse imaging were performed in a number of regions on the film surface sized 2x2, 1x1, 0.5x0.5, and 0.3x0.3 μm2 with subsequent statistical analysis of the obtained data. It has been found that variations of the polarization signal can be approximated by the normal distribution function. The standard deviation increases with the decrease in the capacitor size, suggesting a stronger effect of grain misalignment in smaller capacitors. The obtained results imply that reliable high-density ferroelectric memories cannot be realized unless a certain capacitor size/ grain size ratio is maintained.