Tunnel Magnetoresistance with Plasma Oxidation Time in Doubly Oxidized Barrier Process

Ohsung Song, Y. M. Lee, Kiyung Lee, C. S. Yoon, C. K. Kim

Research output: Contribution to journalArticlepeer-review


Magnetic tunnel junctions (MTJ) with the tunnel barrier oxidized in two steps with plasma were fabricated to obtain a structurally uniform AlO x insulator. Plasma oxidation of 10 Å-thick AI layer for 5-20 sec formed the initial oxide barrier on top of which a second oxide layer was deposited by oxidizing 13 Å-thick Al for 120 sec. The doubly oxidized junctions exhibited a magnetoresistance (MR) ratio of 27-31 % depending on the oxidation period of the initial oxide layer while only 24 % was obtained for the junction deposited in one-step oxidation with a similar stack configuration. The junction resistance of the MTJ increased monotonically with oxidation time while minimal deterioration of the MR ratio was observed when oxidation time increased from 5 sec to 20 sec. Transmission electron microscopy of the junctions also confirmed that the AlOx thickness was thinner for the doubly oxidized junctions compared to the singly oxidized MTJ. X-ray photoelectron spectroscopy of the double junction also strongly suggested that the initial oxide layer prevents over-oxidation of the bottom electrode. Our results suggest that the AlOx oxidized in two steps produces improved junction performance as well as a wider processing window.

Original languageEnglish
Pages (from-to)421-425
Number of pages5
JournalMetals and Materials International
Issue number4
StatePublished - Aug 2003


  • Doubly oxidation barrier
  • MRAM
  • Magnetic tunnel junction
  • Plasma oxidation time
  • TEM
  • XPS


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