Programming speed, cycle-life and failure mechanisms in binary and multistate ovonic (phase-change) chalcogenide memory devices

Sensitivity of resistance-current characteristic and programming speed to material and geometry of electrical contacts is demonstrated for same chalcogenide memory alloys. It was established that set speed is more sensitive to changes in top (positive) contact properties. Reset speed was found mostly dependent on bottom (negative) contact lateral properties: electro- and thermo-conductivity. Single fundamental failure mechanism: deterioration of programming speed is suggested. Failure modes and mechanisms specific only for multistate memory together with several practical ways of either using failure phenomena of avoiding failure are described.