journalArticle
Hamouda
W.
Pancotti
A.
Lubin
C.
Tortech
L.
Richter
C.
Mikolajick
T.
Schroeder
U.
Barrett
N.
E-POM
POLE 2
Physical chemistry of the TiN/Hf0.5Zr0.5O2 interface
Ferroelectric hafnia-based thin films are promising candidates for emerging high-density embedded nonvolatile memory technologies, thanks to their compatibility with silicon technology and the possibility of 3D integration. The electrode–ferroelectric interface and the crystallization annealing temperature may play an important role in such memory cells. The top interface in a TiN/Hf0.5Zr0.5O2/TiNTiN/Hf0.5Zr0.5O2/TiN<math display="inline" overflow="scroll" altimg="eq-00001.gif"> <mrow> <mi mathvariant="normal">TiN</mi></mrow> <mo>/</mo> <msub> <mrow> <mi mathvariant="normal">Hf</mi></mrow> <mrow> <mn>0.5</mn></mrow></msub> <msub> <mrow> <mi mathvariant="normal">Zr</mi></mrow> <mrow> <mn>0.5</mn></mrow></msub> <msub> <mrow> <mi mathvariant="normal">O</mi></mrow> <mn>2</mn></msub> <mo>/</mo> <mrow> <mi mathvariant="normal">TiN</mi></mrow></math> metal–ferroelectric–metal stack annealed at different temperatures was investigated with X-ray photoelectron spectroscopy. The uniformity and continuity of the 2 nm TiN top electrode was verified by photoemission electron microscopy and conductive atomic force microscopy. Partial oxidation of the electrode at the interface is identified. Hf is reduced near the top interface due to oxygen scavenging by the top electrode. The oxygen vacancy (VOVO<math display="inline" overflow="scroll" altimg="eq-00002.gif"> <msub> <mi>V</mi> <mrow> <mi mathvariant="normal">O</mi></mrow></msub></math>) profile showed a maximum at the top interface (0.71%) and a sharp decrease into the film, giving rise to an internal field. Annealing at higher temperatures did not affect the VOVO<math display="inline" overflow="scroll" altimg="eq-00003.gif"> <msub> <mrow> <mi mathvariant="normal">V</mi></mrow> <mrow> <mrow> <mi mathvariant="normal">O</mi></mrow></mrow></msub></math> concentration at the top interface but causes the generation of additional VOVO<math display="inline" overflow="scroll" altimg="eq-00004.gif"> <msub> <mrow> <mi mathvariant="normal">V</mi></mrow> <mrow> <mrow> <mi mathvariant="normal">O</mi></mrow></mrow></msub></math> in the film, leading to a decrease of the Schottky Barrier Height for electrons. The interface chemistry and n-type film doping are believed to be at the origin of several phenomena, including wake-up, imprint, and fatigue. Our results give insights into the physical chemistry of the top interface with the accumulation of defective charges acting as electronic traps, causing a local imprint effect. This may explain the wake-up behavior as well and also can be a possible reason of the weaker endurance observed in these systems when increasing the annealing temperature.
064105
February 11, 2020
https://aip.scitation.org/doi/10.1063/1.5128502
2021-01-07 12:18:11
aip.scitation.org (Atypon)
Publisher: American Institute of Physics
Journal of Applied Physics
127
6
J. Appl. Phys.
DOI 10.1063/1.5128502
ISSN 0021-8979