Capacitors in the mask: Thanks to a 100 nm thin mask made of aluminum oxide (above), the German and Korean research team were able to trickle the ceramic (PZT) onto the platinum layer (Pt). The scientists then cut off some platinum to create electrical contact to the ceramic. Image: Max Planck Institute of Microstructure Physics
Woo Lee1, Hee Han Andriy Lotnyk, Markus Andreas Schubert, Stephan Senz, Marin Alexe, Dietrich Hesse, Sunggi Baik & Ulrich Gösele1
– Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany
– Department of Materials Science & Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, 790-784 Pohang, Korea
– Korea Research Institute of Standards and Science (KRISS), Yuseong, 305-340 Daejon, Korea
Ferroelectric materials have emerged in recent years as an alternative to magnetic and dielectric materials for nonvolatile data-storage applications. Lithography is widely used to reduce the size of data-storage elements in ultrahigh-density memory devices. However, ferroelectric materials tend to be oxides with complex structures that are easily damaged by existing lithographic techniques, so an alternative approach is needed to fabricate ultrahigh-density ferroelectric memories. Here we report a high-temperature deposition process that can fabricate arrays of individually addressable metal/ferroelectric/metal nanocapacitors with a density of 176 Gb inch- 2. The use of an ultrathin anodic alumina membrane as a lift-off mask makes it possible to deposit the memory elements at temperatures as high as 650 °C, which results in excellent ferroelectric properties.
The permanent memory produced through the German-Korean cooperation can save 176 billion bits per square inch, which is 27 billion bits per square centimeter – more than any comparable memory made of this type of material. “We are approaching memory density of several terabits or billions of bits per square inch, and we hope to be able to increase the memory density even further,” relates Dietrich Hesse. Such high memory density is necessary for more widespread use of permanent memory. They could, for example, make the hard-drive and tedious booting up of computers a thing of the past.