Imprint testing of ferroelectric capacitors used for non-volatile memories

Abstract

A set of criteria is presented, based on the polarization versus electric field hysteresis characteristics, which can be used to reveal a tendency towards imprint failure in ferroelectric capacitors. A series of pulsed voltage waveforms, generated by the RT66A ferroelectric tester, are utilized to validate our established criteria for the tendency towards imprinting. The tests have been performed on hetero-structure Pb(Zr_xTi_1−x)O₃(PZT)-based capacitors produced by a pulsed laser ablation depositon technique (PLAD). The loss of retained charge in the ferroelectric capacitors is considered in light of the imprint test methodology. Rates of retention loss and imprint are extracted from the experimental data and treated as separate processes that lead to device failure. The rate of approach towards imprint failure is found to be influenced by the magnitude of the read pulse.

Key Words:

• Imprint
• fatigue
• retention
• ferroelectric memory
• lead-zirconate-titanate