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Megan Landberg. Portrait.

Megan Landberg

Postdoctoral fellow

Megan Landberg. Portrait.

Ferroelectricity in Ultrathin HfO2-Based Films by Nanosecond Laser Annealing

Author

  • Robin Athle
  • Megan O. Hill
  • Austin Irish
  • Huaiyu Chen
  • Rainer Timm
  • Elias Kristensson
  • Jesper Wallentin
  • Mattias Borg

Summary, in English

Nonvolatile memory devices based on ferroelectric HfxZr1-xO2 (HZO) show great promise for back-end integrable storage and for neuromorphic accelerators, but their adoption is held back by the inability to scale down the HZO thickness without violating the strict thermal restrictions of the Si CMOS back end of line. In this work, we overcome this challenge and demonstrate the use of nanosecond pulsed laser annealing (NLA) to locally crystallize areas of an ultrathin (3.6 nm) HZO film into the ferroelectric orthorhombic phase. Meanwhile, the heat induced by the pulsed laser is confined to the layers above the Si, allowing for back-end compatible integration. We use a combination of electrical characterization, nanofocused scanning X-ray diffraction (nano-XRD), and synchrotron X-ray photoelectron spectroscopy (SXPS) to gain a comprehensive view of the change in material and interface properties by systematically varying both laser energy and the number of laser pulses on the same sample. We find that NLA can provide remanent polarization up to 2Pr= 11.6 μC/cm2 in 3.6 nm HZO, albeit with a significant wake-up effect. The improved TiN/HZO interface observed by XPS explains why device endurance goes beyond 107 cycles, whereas an identical film processed by rapid thermal processing (RTP) breaks already after 106 cycles. All in all, NLA provides a promising approach to scale down the ferroelectric oxide thickness for emerging HZO ferroelectric devices, which is key for their integration in scaled process nodes.

Department/s

  • LTH Profile Area: Nanoscience and Semiconductor Technology
  • NanoLund: Centre for Nanoscience
  • Electromagnetics and Nanoelectronics
  • MAX IV Laboratory
  • Synchrotron Radiation Research
  • LU Profile Area: Light and Materials
  • Combustion Physics
  • Lund Laser Centre, LLC

Publishing year

2024

Language

English

Publication/Series

ACS Applied Materials and Interfaces

Volume

16

Issue

41

Document type

Journal article

Publisher

The American Chemical Society (ACS)

Topic

  • Atom and Molecular Physics and Optics

Keywords

  • BEOL compatibility
  • FeRAM
  • ferroelectric
  • hafnium oxide
  • thin films

Status

Inpress

Research group

  • Electromagnetics and Nanoelectronics

ISBN/ISSN/Other

  • ISSN: 1944-8244