Magnetic tunnel junction device

• US 8,319,263 B2
• Filed: 09/30/2010
• Issued: 11/27/2012
• Est. Priority Date: 03/12/2004
• Status: Active Grant

• Current Assignee: Godo Kaisha IP Bridge 1 (IP Bridge, Inc.)
• Original Assignee: National Institute of Advanced Industrial Science and Technology (Government of Japan), Japan Science And Technology Agency
• Inventors: Yuasa, Shinji
• Primary Examiner(s): Chambliss, Alonzo
• Application Number:
  US12/923,643
• Publication Number:
  US 20110031570A1
• Time in Patent Office: 789 Days
• Field of Search: None
• US Class Current: 257/295
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G11C 11/15 using multiple magnetic layers G11C11/155 takes precedence
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: H01F 10/132 containing cobalt
• CPC Class Codes: H01F 10/3254 the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
• CPC Class Codes: H01L 28/55 with a dielectric comprising a perovskite structure material
• CPC Class Codes: H10B 53/30 characterised by the memory core region
• CPC Class Codes: H10B 61/00 Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
• CPC Class Codes: H10B 61/22 of the field-effect transistor [FET] type
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/80 Constructional details
• CPC Class Codes: H10N 50/85 Magnetic active materials
• CPC Class Codes: H10N 59/00 Integrated devices, or assemblies of multiple devices, comprising at least one galvanomagnetic or Hall-effect element covered by groups H10N50/00 - H10N52/00 MRAM devices H10B61/00

Abstract

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.

Claims

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 ω

in a range of 0.2 to 0.5 eV.

2. The magnetoresistive device according to claim 1, wherein at least one of the first and second ferromagnetic material layers comprises CoFeB alloy.

3. The magnetoresistive device according to claim 1, wherein said tunnel barrier height ψ

is obtained by fitting J-V characteristics of the tunnel barrier junction structure to an equation (1)

J=[(2mψ

)^1/2/Δ

s](e/h)²×

exp[−

(4 π

Δ

s/h)×

(2mψ

)^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, Δ

s is an effective thickness of the tunnel barrier layer that is approximately equivalent to (T_MgO−

0.5 nm), and t_MgO is an actual thickness of the tunnel barrier layer determined using a cross-sectional transmission electron microscope image.

4. The magnetoresistive device according to claim 3, wherein at least one of the first and second ferromagnetic material layers comprises CoFeB alloy.