ABSTRACT
When a ferroelectric capacitor is used as a storage device in an integrated nonvolatile memory cell, a write operation is performed by the application of a voltage pulse across the capacitor. It has been reported elsewhere111 that the nonvolatile polarization of the ferroelectric capacitor depends not only on the amplitude but also on the width of the applied pulses. This indicates that for a given film thickness and available amplitude, a write pulse of some minimum width must be applied to ensure that sufficient polarization of the ferroelectric layer is achieved. If this minimum pulse width is too long, it poses the prob lem of limiting the speed at which realizable memories may operate. It is of vital importance to understand the dependence of polarization on pulse width and amplitude in order to produce successful ferroelectric memory designs. It 561
is therefore necessary to develop techniques for directly measuring these ef fects at speeds comparable to those at which integrated memory circuits actu ally operate. Measurement data of this type are also necessary for developing and refining ferroelectric device models suitable for use in circuit simulators.
