Ferroelectronic ram memory family for critical data storage

Ferroelectric materials show a spontaneous electrical polarization that can be reversed in sense by an applied external electric field. It should, therefore, be feasible to build a ferroelectric memory device that can store information in digital form. Early attempts to build such a memory have failed for various reasons, the major one being a lack of a well defined and stable coercive field, which resulted in the eventual loss of data due to half-select pulses applied to unselected cells in the crosspoint array architecture. Fatigue or wear out was also a problem in that the amount of available signal depended upon the number of polarization reversals. We have been able to overcome these problems by a combination of design innovations and process/materials breakthroughs. We have chosen PZT (lead zirconate titanate) as the basic ferroelectric material and integrated it into a standard 1.5μ CMOS process. PZT has a wide temperature range (+ 350°C Curie Temperature), low coercive voltage, high specific polar...