Magnetic tunnel junction device

• US 9,123,463 B2
• Filed: 02/14/2013
• Issued: 09/01/2015
• 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:
  US13/767,290
• Publication Number:
  US 20130228883A1
• Time in Patent Office: 929 Days
• US Class Current: 1/1
• 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 as follows: A single-crystalline MgO (001) substrate is prepared. An epitaxial Fe(001) lower electrode (a first electrode) is grown on a MgO(001) seed layer at room temperature, followed by annealing under ultrahigh vacuum. A MgO(001) barrier layer 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) is then formed on the MgO(001) barrier layer at room temperature. This is successively followed by the deposition of a Co layer on the Fe(001) upper electrode (the second electrode). The Co layer is provided so as to increase the coercive force of the upper electrode in order to realize an antiparallel magnetization alignment.

Claims

1. A tunnel barrier layer disposed on a ferromagnetic material layer that is disposed on a substrate,

wherein the tunnel barrier layer comprises a poly-crystalline magnesium oxide layer in which a (001) crystal plane is preferentially oriented,

wherein the tunnel barrier layer has a barrier height φ

in a range of 0.2 to 0.5 e V, where the barrier height φ

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

J=[(2mφ

)^1/2/Δ

s](e/h)²×

exp[−

(4π

Δ

s/h)×

(2mφ

)^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 the free electron mass, e is the elementary electric charge, h is the Plank'"'"'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, and

wherein the ferromagnetic material layer comprises CoFeB alloy that is at least partially crystallized.

2. The tunnel barrier layer according to claim 1, wherein the ferromagnetic material layer is entirely crystallized.