How to make DRAM non-volatile? Anti-ferroelectrics: A new paradigm for universal memories

Abstract

The major disadvantages of DRAM memory cells are the very short retention time and high power consumption needed to refresh the stored information. Here, we present a new concept using a modified DRAM capacitor stack to enable non-volatile data storage. Recent reports verified anti-ferroelectric properties for pure ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> dielectrics used in DRAM stacks. Anti-ferroelectric materials are well known for high endurance strength but at the same time volatile memory behavior. Based on Landau theory, we propose a simple way how non-volatility can be achieved in state-of-the-art ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> based DRAM stacks. By employing electrodes with different workfunction values, a built-in bias is introduced within the AFE stack, thus creating two stable non-volatile states. Moreover, we report the fabrication of the world's first non-volatile AFE-RAM. Detailed characterization proved high endurance and reliable operation of this non-volatile DRAM stack equivalent. In addition to the 1T-1C cell, we show a proof of concept for a MIS capacitor device which can be integrated in future AFE-FET based 1T memory architectures.