Method of measuring retention performance and imprint degradation of

Abstract

A test method for characterizing retention performance, both same state and opposite state performance, of ferroelectric capacitors includes the steps of writing an original complementary data state into first and second ferroelectric capacitors after the ferroelectric capacitors have been initialized into an initial valid data state. The first and second ferroelectric capacitors are then subjected to time and temperature stress. The original complementary data state from the first and second ferroelectric capacitors is then read, and same state charge (Q.sub.SS) information is collected. An opposite complementary data state is then written in the first and second capacitors. After a short time interval, possibly at an elevated temperature, the opposite complementary data state from the first and second ferroelectric capacitors is read to gather opposite state charge (Q.sub.OS) information. The original complementary data state is then written into the first and second ferroelectric capacitors. The first and second ferroelectric capacitors are then subjected to further stress cycles, after which the same state and opposite state charge values are recorded. A plot of the same state charge (Q.sub.SS) and opposite state charge (Q.sub.OS) versus log time can be generated, which has great value for fully characterizing a ferroelectric capacitor and for predicting the performance of a ferroelectric capacitor in a memory circuit.