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Magnetic tunnel junction device

Foreign code F200010178
File No. K02012US8
Posted date Jun 5, 2020
Country United States of America
Application number 201916443875
Gazette No. 20200020851
Gazette No. 10680167
Date of filing Jun 18, 2019
Gazette Date Jan 16, 2020
Gazette Date Jun 9, 2020
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
  • 200510591947 (Mar 10, 2005) US
  • 2005JP04720 (Mar 10, 2005) WO
  • 201012923643 (Sep 30, 2010) US
  • 201213400340 (Feb 20, 2012) US
  • 201313767290 (Feb 14, 2013) US
  • 201514837558 (Aug 27, 2015) US
  • 201715428842 (Feb 9, 2017) US
Title Magnetic tunnel junction device
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.
Outline of related art and contending technology BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a magnetic tunnel junction device and a method of manufacturing the same, particularly to a magnetic tunnel junction device with a high magnetoresistance and a method of manufacturing the same.
Description of Related Art
Magnetoresistive random access memories (MRAMs) refer to a large-scale integrated memory circuit that is expected to replace the currently widely used DRAM memories. Research and development of MRAM devices, which are fast and non-volatile memory devices, are being extensively carried out, and sample products of a 4 Mbit MRAM have actually been delivered.
FIGS. 8(A) and 8(B) show the structure and operation principle of a magnetic tunnel junction device (to be hereafter referred to as a “MTJ device”), which is the most important part of the MRAM. As shown in FIG. 8(A), a MTJ device comprises a tunnelling junction structure in which a tunnel barrier (to be hereafter also referred to as a “barrier layer”) made of an oxide is sandwiched between a first and a second electrode made of a ferromagnetic metal. The tunnel barrier layer comprises an amorphous Al―O layer (see Non-Patent Document 1). As shown in FIG. 8(A), in the case of parallel magnetization alignment where the directions of magnetizations of the first and second ferromagnetic electrodes are aligned parallel, the electric resistance of the device with respect to the direction normal to the interfaces of the tunneling junction structure decreases. On the other hand, in the case of antiparallel magnetization alignment where the directions of magnetizations of the first and second ferromagnetic electrodes are aligned antiparallel as shown in FIG. 8(B), the electric resistance with respect to the direction normal to the interfaces of the tunneling junction structure increases. The resistance value does not change in a general state, so that information “1” or “0” can be stored depending on whether the resistance value is high or not. Since the parallel and antiparallel magnetization alignments can be stored in a non-volatile fashion, the device can be used as a non-volatile memory device.
FIGS. 9(A)-(C) show an example of the basic structure of the MRAM. FIG. 9(A) shows a perspective view of the MRAM, and FIG. 9(B) schematically shows a circuit block diagram. FIG. 9(C) is a cross-section of an example of the structure of the MRAM. Referring to FIG. 9(A), in an MRAM, a word line WL and a bit line BL are disposed in an intersecting manner, with an MRAM cell disposed at each intersection. As shown in FIG. 9(B), the MRAM cell disposed at the intersection of a word line and a bit line comprises a MTJ device and a MOSFET directly connected to the MTJ device. Stored information can be read by reading the resistance value of the MTJ device that functions as a load resistance, using the MOSFET. The stored information can be rewritten by applying a magnetic field to the MTJ device, for example. As shown in FIG. 9(C), an MRAM memory cell comprises a MOSFET 100 including a source region 105 and a drain region 103 both formed inside a p-type Si substrate 101, and a gate electrode 111 formed on a channel region that is defined between the source and drain regions. The MRAM also comprises a MTJ device 117. The source region 105 is grounded, and the drain is connected to a bit line BL via the MTJ device. A word line WL is connected to the gate electrode 111 in a region that is not shown.
Thus, a single non-volatile MRAM memory cell can be formed by a single MOSFET 100 and a single MTJ device 117. The MRAMs are therefore suitable where high levels of integration are required.
- Non-Patent Document 1: D. Wang, et al.: Science 294 (2001) 1488.
Scope of claims [claim1]
1. A method of manufacturing a magnetic tunnel junction (MTJ) device, comprising:
forming a first CoFeB layer that is amorphous;
forming a magnesium oxide (MgO) layer over the first CoFeB layer;
forming a second CoFeB layer that is amorphous over the MgO layer; and
annealing the first and second CoFeB layers and the MgO layer,
wherein the first and second CoFeB layers are crystallized by the annealing, and
wherein the MgO layer is poly-crystalline in which a (001) crystal plane is preferentially oriented.

[claim2]
2. The method of claim 1,
wherein after the annealing, the first and second CoFeB layers are entirely crystallized.

[claim3]
3. The method of claim 1,
wherein after the annealing, each of the first and second CoFeB layers is poly-crystalline in which a (001) crystal plane is preferentially oriented.

[claim4]
4. The method of claim 1, wherein after the annealing,
the first and second CoFeB layers are entirely crystallized, and
each of the first and second CoFeB layers is poly-crystalline in which a (001) crystal plane is preferentially oriented.

[claim5]
5. The method of claim 1,
wherein after the annealing, each of the first and second CoFeB layers is poly-crystalline in which a (001) crystal plane is preferentially oriented and each of the first and second CoFeB layers includes a BCC (body-centered cubic) structure.

[claim6]
6. The method of claim 1, wherein after the annealing,
the first and second CoFeB layers are entirely crystallized, and
each of the first and second CoFeB layers is poly-crystalline in which a (001) crystal plane is preferentially oriented and each of the first and second CoFeB layers includes a BCC (body-centered cubic) structure.

[claim7]
7. The method of claim 1,
wherein in the forming the MgO layer, the MgO layer is formed as a MgOx (0<x<1) layer.

[claim8]
8. The method of claim 1,
wherein in the forming the MgO layer, the value of x in MgOx for the MgO layer is greater than 0 and less than 1.

[claim9]
9. The method of claim 1,
wherein in the forming the MgO layer, the MgO layer is formed directly on the first CoFeB layer.

[claim10]
10. The method of claim 1, wherein:
in the forming the MgO layer, the MgO layer is formed directly on the first CoFeB layer, and
in the forming the second CoFeB layer, the second CoFeB layer is formed directly on the MgO layer.

[claim11]
11. A method of manufacturing a magnetic tunnel junction (MTJ) device, comprising:
forming a first ferromagnetic layer including a first CoFeB layer that is amorphous;
forming a barrier layer including a magnesium oxide (MgO) layer to have a poly-crystalline state in which a (001) crystal plane is preferentially oriented over the first ferromagnetic layer;
forming a second ferromagnetic layer including a second CoFeB layer that is amorphous over the barrier layer; and
annealing the first and second ferromagnetic layers and the barrier layer, to crystallize the first and second CoFeB layers.

[claim12]
12. The method of claim 11,
wherein after the annealing, the first and second CoFeB layers are entirely crystallized.

[claim13]
13. The method of claim 11, wherein after the annealing,
the first and second CoFeB layers are entirely crystallized, and
each of the first and second CoFeB layers is poly-crystalline in which a (001) crystal plane is preferentially oriented and each of the first and second CoFeB layers includes a BCC (body-centered cubic) structure.

[claim14]
14. The method of claim 11,
wherein in the forming the barrier layer, the MgO layer is formed as a MgOx (0<x<1) layer.

[claim15]
15. The method of claim 11, wherein:
in the forming the barrier layer, the barrier layer is formed directly on the first ferromagnetic layer, and
in the forming the second ferromagnetic layer, the second ferromagnetic layer is formed directly on the barrier layer.
  • Inventor, and Inventor/Applicant
  • YUASA SHINJI
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
  • NATIONAL INSTITUTE OF ADVANCED INDUSTRIAL SCIENCE AND TECHNOLOGY
IPC(International Patent Classification)
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