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Magnetic tunnel junction device

Foreign code F110005387
File No. K02012US3
Posted date Sep 5, 2011
Country United States of America
Application number 92364310
Gazette No. 20110031570
Gazette No. 8319263
Date of filing Sep 30, 2010
Gazette Date Feb 10, 2011
Gazette Date Nov 27, 2012
International application number JP2005004720
International publication number WO2005088745
Date of international filing Mar 10, 2005
Date of international publication Sep 22, 2005
Priority data
  • P2004-071186 (Mar 12, 2004) JP
  • P2004-313350 (Oct 28, 2004) JP
  • 2005US-10591947 (Mar 10, 2005) US
  • 2005WO-JP04720 (Mar 10, 2005) WO
Title Magnetic tunnel junction device
Abstract (US8319263)
The output voltage of an MRAM is increased by means of an Fe(001)/MgO(001)/Fe(001) MTJ device, which is formed by microfabrication of a sample prepared by the following steps.
A single-crystalline MgO (001) substrate 11 is prepared.
An epitaxial Fe(001) lower electrode (a first electrode) 17 with the thickness of 50 nm is grown on a MgO(001) seed layer 15 at room temperature, followed by annealing under ultrahigh vacuum (2×10-8 Pa) and at 350° C.
A MgO(001) barrier layer 21 with the thickness of 2 nm is epitaxially formed on the Fe(001) lower electrode (the first electrode) at room temperature, using a MgO electron-beam evaporation.
A Fe(001) upper electrode (a second electrode) with the thickness of 10 nm is then formed on the MgO(001) barrier layer 21 at room temperature.
This is successively followed by the deposition of a Co layer 21 with the thickness of 10 nm on the Fe(001) upper electrode (the second electrode) 23.
The Co layer 21 is provided so as to increase the coercive force of the upper electrode 23 in order to realize an antiparallel magnetization alignment.
Scope of claims [claim1]
1. A magnetoresistive device having a tunnel barrier junction structure, the magnetoresistive device comprising: a first ferromagnetic material layer of BCC structure;
a second ferromagnetic material layer of a BCC structure; and
a tunnel barrier layer located between the first and second ferromagnetic material layers, and
wherein the tunnel barrier layer comprises:
a single-crystalline magnesium oxide layer in which (001) crystal plane is preferentially oriented or a poly-crystalline magnesium oxide layer in which (001) crystal plane is preferentially oriented, and
wherein the tunnel barrier layer has a tunnel barrier height omega in a range of 0.2 to 0.5 eV.
[claim2]
2. The magnetoresistive device according to claim 1, wherein at least one of the first and second ferromagnetic material layers comprises CoFeB alloy.
[claim3]
3. The magnetoresistive device according to claim 1, wherein said tunnel barrier height psi is obtained by fitting J-V characteristics of the tunnel barrier junction structure to an equation (1)
J=[(2mpsi )1/2/DELTA s](e/h)2 * exp[-(4 pi DELTA s/h) * (2mpsi )1/2] * V (1)
where J is a tunnel current density flowing through the tunnel barrier layer, V is an applied bias voltage that is 100 mV or smaller, m is a mass of the free electron, e is the elementary electric charge, h is the Planck's constant, DELTA s is an effective thickness of the tunnel barrier layer that is approximately equivalent to (TMgO-0.5 nm), and tMgO is an actual thickness of the tunnel barrier layer determined using a cross-sectional transmission electron microscope image.
[claim4]
4. The magnetoresistive device according to claim 3, wherein at least one of the first and second ferromagnetic material layers comprises CoFeB alloy.
  • Inventor, and Inventor/Applicant
  • YUASA SHINJI
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
  • NATIONAL INSTITUTE OF ADVANCED INDUSTRIAL SCIENCE AND TECHNOLOGY
IPC(International Patent Classification)
Reference ( R and D project ) PRESTO Nanostructure and Material Property AREA
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