U.S. patent application number 16/125764 was filed with the patent office on 2019-01-03 for magnetic memory device.
This patent application is currently assigned to TOSHIBA MEMORY CORPORATION. The applicant listed for this patent is TOSHIBA MEMORY CORPORATION. Invention is credited to Tatsuya KISHI, Kenji NOMA, Satoshi SETO, Kazuhiro TOMIOKA, Shuichi TSUBATA, Hiroaki YODA, Masatoshi YOSHIKAWA.
Application Number | 20190006580 16/125764 |
Document ID | / |
Family ID | 54069906 |
Filed Date | 2019-01-03 |
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United States Patent
Application |
20190006580 |
Kind Code |
A1 |
YOSHIKAWA; Masatoshi ; et
al. |
January 3, 2019 |
MAGNETIC MEMORY DEVICE
Abstract
A method of manufacturing a magnetic memory device includes
forming a stacked structure including a magnetic element, forming a
metal film which covers the stacked structure, and forming a
protective insulating film formed of a metallic oxide by oxidizing
the metal film. A metal element contained in the metallic oxide is
selected from yttrium (Y), aluminum (Al), magnesium (Mg), calcium
(Ca), zirconium (Zr) and hafnium (Hf).
Inventors: |
YOSHIKAWA; Masatoshi;
(Seoul, KR) ; YODA; Hiroaki; (Kawasaki Kanagawa,
JP) ; TSUBATA; Shuichi; (Seoul, KR) ; NOMA;
Kenji; (Yokohama Kanagawa, JP) ; KISHI; Tatsuya;
(Seongnam-si Gyeonggi-do, KR) ; SETO; Satoshi;
(Seoul, KR) ; TOMIOKA; Kazuhiro; (Seoul,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOSHIBA MEMORY CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
TOSHIBA MEMORY CORPORATION
Tokyo
JP
|
Family ID: |
54069906 |
Appl. No.: |
16/125764 |
Filed: |
September 9, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15400466 |
Jan 6, 2017 |
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16125764 |
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14479192 |
Sep 5, 2014 |
9570671 |
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15400466 |
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61952047 |
Mar 12, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 43/10 20130101;
H01L 43/12 20130101; H01L 43/08 20130101; H01L 43/02 20130101 |
International
Class: |
H01L 43/02 20060101
H01L043/02; H01L 43/10 20060101 H01L043/10; H01L 43/08 20060101
H01L043/08; H01L 43/12 20060101 H01L043/12 |
Claims
1. A method of manufacturing a magnetic memory device, the method
comprising: forming a stacked structure including a magnetic
element; forming a metal film which covers the stacked structure;
and forming a protective insulating film formed of a metallic oxide
by oxidizing the metal film, wherein a metal element contained in
the metallic oxide is selected from yttrium (Y), aluminum (Al),
magnesium (Mg), calcium (Ca), zirconium (Zr) and hafnium (Hf).
2. The method of claim 1, wherein a linear coefficient of thermal
expansion of the metallic oxide is greater than
5.times.10.sup.-6/K.
3. The method of claim 1, wherein a linear coefficient of thermal
expansion of the metallic oxide is greater than
7.times.10.sup.-6/K.
4. The method of claim 1, wherein the magnetic element contains at
least one of cobalt (Co), iron (Fe), boron (B) and magnesium
(Mg).
5. The method of claim 1, wherein the magnetic element includes a
first magnetic layer, a second magnetic layer, and a nonmagnetic
layer provided between the first magnetic layer and the second
magnetic layer.
6. A method of manufacturing a magnetic memory device, the method
comprising: forming a stacked structure including a magnetic
element; forming a metal film which covers the stacked structure;
and forming a protective insulating film formed of a metallic oxide
by oxidizing the metal film, wherein a linear coefficient of
thermal expansion of the metallic oxide is greater than
5.times.10.sup.-6/K.
7. The method of claim 6, wherein the linear coefficient of thermal
expansion of the metallic oxide is greater than
7.times.10.sup.-6/K.
8. The method of claim 6, wherein the magnetic element contains at
least one of cobalt (Co), iron (Fe), boron (B) and magnesium
(Mg).
9. The method of claim 6, wherein the magnetic element includes a
first magnetic layer, a second magnetic layer, and a nonmagnetic
layer provided between the first magnetic layer and the second
magnetic layer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional application of U.S.
application Ser. No. 15/400,466, filed Jan. 6, 2017, which is a
Divisional application of U.S. application Ser. No. 14/479,192,
filed Sep. 5, 2014. U.S. application Ser. No. 14/479,192 claims the
benefit of U.S. Provisional Application No. 61/952,047, filed Mar.
12, 2014. The entire contents of all of the above-identified
applications are incorporated herein by reference.
FIELD
[0002] Embodiments described herein relate generally to a magnetic
memory device.
BACKGROUND
[0003] Recently, many kinds of solid-state memories which record
data based on new principles have been suggested. In particular, as
a solid-state magnetic memory, a magnetoresistive random access
memory (MRAM) comprising a magnetoresistive tunneling junction
(MTJ) element using the magneto resistance (MR) effect is known.
Currently, the MRAM stores the information of 0 or 1 depending on
the state of magnetization of the storage layer of an MTJ
element.
[0004] The MTJ element includes a magnetic storage layer
(hereinafter, storage layer) and a magnetic reference layer
(hereinafter, reference layer). In the storage layer, data is
stored and the magnetization is variable. In the reference layer,
the magnetization is fixed and does not move. When the direction of
magnetization of the storage layer is parallel to the direction of
magnetization of the reference layer, the resistance is low (0
state); when anti-parallel, the resistance is high (1 state). This
difference in resistance is used to determine the information.
[0005] As a method for writing data to the MTJ element, a current
magnetic-field-writing system (hereinafter, magnetic-field writing)
by the current magnetic field from a bit line is known. In this
system, lines are provided near the MTJ element. By the magnetic
field produced by the current flowing through the lines, the
magnetization of the storage layer of the MTJ element is inverted.
When the MTJ element is made small to miniaturize the MRAM, the
magnetic field necessary to invert the storage layer of the MTJ
element increases. In sum, the magnetic coercive force Hc is
increased. Thus, in the magnetic-field-writing MRAM, a large
current magnetic field is required in association with the
development of the miniaturization, and the write current is large.
As a result, it is difficult to realize both the miniaturization
and the low current of the memory cell for the purpose of
increasing the capacity.
[0006] To solve this problem, a writing system (hereinafter, spin
transfer torque writing) using spin-momentum transfer (SMT) is
suggested.
[0007] In a spin transfer torque writing MRAM, the state of
magnetization of the storage layer of the MTJ element is changed
(inverted) by vertically passing current into the film surface of
each film constituting the MTJ element.
[0008] In the magnetization inversion by spin transfer torque, the
current Ic necessary for magnetization inversion is defined by the
current density Jc. Therefore, if the area of the surface of the
MTJ element in which current passes is reduced, the injection
current Ic for inverting the magnetization is also decreased. In a
case where writing is performed with a constant current density,
when the MTJ element is small, the current Ic is also small. Thus,
the spin transfer torque writing system is, in principle, scalable.
With the spin transfer torque writing system, an MRAM with a large
capacity has become possible.
[0009] The above-described MTJ element (magnetic element) is
covered by a protective insulating film. However, generally, the
coefficient of thermal expansion of the material contained in the
MTJ element (magnetic element) is greater than the coefficient of
thermal expansion of the material contained in the protective
insulating film. Therefore, a thermal stress may be applied between
the magnetic element and the protective insulating film, and have a
negative influence on the characteristic and reliability of the
magnetic memory device.
[0010] In view of the above factors, an MRAM comprising an MTJ
element in which the stress between an MTJ element (magnetic
element) and a protective insulating film is reduced is
desired.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a cross-sectional view schematically showing a
part of a method for manufacturing a magnetic memory device
according to a first embodiment.
[0012] FIG. 2 is a cross-sectional view schematically showing a
part of the method for manufacturing the magnetic memory device
according to the first embodiment.
[0013] FIG. 3 is a cross-sectional view schematically showing a
part of the method for manufacturing the magnetic memory device
according to the first embodiment.
[0014] FIG. 4 is a cross-sectional view schematically showing a
part of a method for manufacturing a magnetic memory device
according to a second embodiment.
[0015] FIG. 5 is a cross-sectional view schematically showing a
part of the method for manufacturing the magnetic memory device
according to the second embodiment.
[0016] FIG. 6 is a cross-sectional view schematically showing a
part of a method for manufacturing a magnetic memory device
according to a third embodiment.
[0017] FIG. 7 is a cross-sectional view schematically showing a
part of the method for manufacturing the magnetic memory device
according to the third embodiment.
[0018] FIG. 8 is a cross-sectional view schematically showing a
part of the method for manufacturing the magnetic memory device
according to the third embodiment.
DETAILED DESCRIPTION
[0019] In general, according to one embodiment, a magnetic memory
device includes a stacked structure including a magnetic element; a
protective insulating film covering the stacked structure; and an
interface layer provided at an interface between the stacked
structure and the protective insulating film. The interface layer
contains a predetermined element which is not contained in the
magnetic element or the protective insulating film.
[0020] Embodiments will be described hereinafter with reference to
the accompanying drawings.
Embodiment 1
[0021] FIG. 3 is a cross-sectional view schematically showing a
structure of a magnetic memory device according to a first
embodiment.
[0022] As shown in FIG. 3, an insulating film 12 is provided in a
bottom part region which is not shown in the figure, and a bottom
electrode 14 is formed within the insulating film 12. The bottom
part region includes a semiconductor substrate, a transistor and an
interconnection, etc.
[0023] An MTJ element based on the stack of a magnetic layer/a
tunnel barrier layer/a magnetic layer is formed on the bottom
electrode 14. The MTJ element is included in a stacked structure 30
basically including an underlayer 16, a storage layer 18, a tunnel
barrier layer 20, a reference layer 22, a shift cancelling layer 24
and a cap layer 26. A spacer layer may be formed between the
reference layer 22 and the shift cancelling layer 24.
[0024] The basic unit of a magnetoresistive effect element
(magnetic element) 28 is formed by the storage layer (first
magnetic layer) 18, the tunnel barrier layer (nonmagnetic layer) 20
and the reference layer (second magnetic layer) 22 described above.
In other words, the magnetic tunneling junction (MTJ) element 28
having the tunnel barrier layer (nonmagnetic layer) 20 between the
storage layer (first magnetic layer) 18 and the reference layer
(second magnetic layer) 22 is formed.
[0025] The MTJ element is not limited to the bottom-SL structure of
FIG. 3 in which the storage layer is provided under the tunnel
barrier layer. The MTJ element includes a top-SL structure, in
which the position of the storage layer and the reference layer is
adverse, and an RL-SCL separation structure, in which the storage
layer is provided between the reference layer and the shift
canceling layer, etc.
[0026] The storage element 28 is a magnetoresistive effect element
of a perpendicular magnetization type of a spin-transfer-torque
(STT) system. A binary value (0 or 1) is stored depending on
whether the direction of magnetization of the storage layer 18 is
parallel or anti-parallel to the direction of magnetization of the
reference layer 22. A binary value is set in accordance with the
direction of the current flowing through the storage element
28.
[0027] The stacked structure 30 including the storage element 28,
the underlayer 16 and the cap layer 26 is covered by a protective
insulating film 32. The protective film has a thermal stress
produced by the temperature at the time of formation and an
in-film-stress (intrinsic stress) of which the protective film
itself is possessed. The thermal stress is produced by the
difference in coefficient of thermal expansion between the magnetic
element and the protective film. The intrinsic stress is the stress
which relies on the film density and the composition of the
protective film, etc., and can be controlled by composition control
or a film formation method. An interface layer 34 is formed at the
interface between the stacked structure 30 and the protective
insulating film 32.
[0028] The magnetic element 28 contains at least one of cobalt
(Co), iron (Fe), boron (B), magnesium (Mg) and platinum (Pt). In
this embodiment, for example, the storage layer 18 and the
reference layer 22 contain CoFeB. A CoFeB layer may be included.
The tunnel barrier layer 20 includes, for example, MgO. The shift
cancelling layer 24 includes, for example, a CoPt film or a Co/Pt
stacked film.
[0029] The protective insulating film 32 contains silicon (Si) and
nitrogen (N). Specifically, the protective insulating film 32 is
formed by a silicon nitride film (SiN film).
[0030] The linear coefficient of thermal expansion (linear CTE) of
at least one material contained in the magnetic element 28 is
greater than the linear CTE of the material contained in the
protective insulating film 32. For example, the linear CTE of the
above-described silicon nitride film is approximately
3.5.times.10.sup.-6/K. The linear CTE of CoFeB is approximately
12.6.times.10.sup.-6/K. The linear CTE of MgO is approximately
9.7.times.10.sup.-6/K.
[0031] The interface layer 34 may contain a predetermined element
which is not contained in the magnetic element 28 or the protective
insulating film 32. In this case, the predetermined element is
selected from argon (Ar), xenon (Xe), krypton (Kr), neon (Ne),
phosphorus (P) and carbon (C).
[0032] The interface layer 34 may be structured in the following
manner: the interface layer 34 contains the predetermined element,
and the concentration of the predetermined element contained in the
interface layer 34 is higher than the concentration of the
predetermined element contained in the magnetic element 28 and the
concentration of the predetermined element contained in the
protective insulating film 32. In this case, the predetermined
element is selected from nitrogen (N) and boron (B).
[0033] As described later, the interface layer 34 is formed by
ion-implanting the predetermined element into the interface between
the magnetic element 28 and the protective insulating film 32.
Thus, the interface layer 34 includes a mixing layer containing the
element contained in the magnetic element 28, the element contained
in the protective insulating film 32 and the predetermined element
which is ion-implanted.
[0034] As described above, generally, the coefficient of thermal
expansion of the material contained in the magnetic element is
greater than the coefficient of thermal expansion of the material
contained in the protective insulating film. Therefore, in the
normal magnetic memory device, a thermal stress may be applied
between the magnetic element and the protective insulating film,
and have a negative influence on the characteristic and reliability
of the magnetic memory device.
[0035] In this embodiment, the interface layer 34 is provided at
the interface between the stacked structure 30 including the
magnetic element 28 and the protective insulating film 32. By the
interface layer 34, the stress between the magnetic element 28 and
the protective insulating film 32 can be reduced. Thus, it is
possible to obtain a magnetic storage device which is excellent in
the characteristic and reliability.
[0036] FIG. 1 to FIG. 3 are cross-sectional views schematically
showing the method for manufacturing the magnetic memory device
according to the first embodiment.
[0037] First, as shown in FIG. 1, the insulating film 12 and the
bottom electrode 14 are formed. Then, the stacked structure 30
including the underlayer 16, the storage layer 18, the tunnel
barrier layer 20, the reference layer 22, the shift cancelling
layer 24 and the cap layer 26 is formed on the bottom electrode 14.
The stacked structure 30 includes the magnetic element 28.
[0038] Next, as shown in FIG. 2, a silicon nitride film is formed
as the protective insulating film 32. Specifically, the silicon
nitride film is formed at the temperature of approximately
300.degree. C. by the CVD. The stacked structure 30 is covered by
the silicon nitride film 32.
[0039] Next, as shown in FIG. 3, the predetermined element is
ion-implanted into the interface between the stacked structure 30
and the protective insulating film 32. The predetermined element is
selected from argon (Ar), xenon (Xe), krypton (Kr), neon (Ne),
phosphorus (P), carbon (C), nitrogen (N) and boron (B). Two or more
than two predetermined elements may be ion-implanted. The process
temperature at the time of ion-implantation is, for example,
approximately a room temperature.
[0040] By ion-implanting the predetermined element, the interface
layer 34 is formed at the interface between the stacked structure
30 and the protective insulating film 32. The interface layer 34
includes a mixing layer containing the element contained in the
magnetic element 28, the element contained in the protective
insulating film 32 and the predetermined element which is
ion-implanted. As a result of the atom migration at the time of
forming the mixing layer, the stress at the interface between the
stacked structure 30 and the protective insulating film 32 can be
reduced.
[0041] Afterward, the magnetic memory device is completed through
an interconnection step, etc.
[0042] As described above, by ion-implanting the predetermined
element into the interface between the stacked structure 30 and the
protective insulating film 32, the interface layer 34 can be formed
at the interface between the stacked structure 30 and the
protective insulating film 32. Thus, the stress between the stacked
structure 30 and the protective insulating film 32 can be reduced.
Therefore, a magnetic memory device which is excellent in the
characteristic and reliability can be obtained.
[0043] In the above-described embodiment, the protective insulating
film (silicon nitride film) 32 is formed at the temperature of
approximately 300.degree. C. However, the silicon nitride film may
be formed at a temperature lower than 300.degree. C. For example,
the silicon nitride film may be formed at a temperature of, or
lower than 200.degree. C. When the silicon nitride film is formed
at a temperature of, or lower than 200.degree. C., for example,
trisilylamine (TSA) (N(SiH.sub.3).sub.3) can be used as gas for the
CVD. As the decomposition temperature of the TSA is low
(approximately 100 to 200.degree. C.), the silicon nitride film can
be formed even at a low temperature. By forming the silicon nitride
film at a low temperature, the thermal stress between the magnetic
element 28 and the protective insulating film 32 can be further
reduced.
[0044] When the silicon nitride film is formed at a temperature of,
or lower than 200.degree. C. as described above, the thermal stress
can be reduced to some extent without ion-implanting the
predetermined element.
[0045] In the above embodiment, the silicon nitride film (SiN film)
is used as the protective insulating film 32. However, as the
protective insulating film 32, a silicon oxide film (SiO.sub.2
film) or a silicon oxynitride film (SiON film) may be used.
Embodiment 2
[0046] FIG. 5 is a cross-sectional view schematically showing a
structure of a magnetic memory device according to a second
embodiment. The basic structure of the second embodiment is the
same as the first embodiment. Therefore, the structural components
which correspond to the first embodiment are designated by the same
reference numbers and symbols. Thus, the explanations of the
matters written in the first embodiment are omitted.
[0047] In the magnetic memory device of this embodiment, a
protective insulating film 42 covering a stacked structure 30 is
formed from a metallic oxide. The metal element contained in the
metallic oxide is selected from yttrium (Y), aluminum (Al),
magnesium (Mg), calcium (Ca) and zirconium (Zr). Specifically, as
the metallic oxide, Y.sub.2O.sub.3, Al.sub.2O.sub.3, Mgo, CaO and
ZrO.sub.x can be considered.
[0048] The linear coefficients of thermal expansion of the above
metallic oxides are as follows:
TABLE-US-00001 Y.sub.2O.sub.3 7.3 .times. 10.sup.-6/K
Al.sub.2O.sub.3 7.2 .times. 10.sup.-6/K MgO 9.7 .times. 10.sup.-6/K
CaO 13.6 .times. 10.sup.-6/K ZrO.sub.x 10.5 .times. 10.sup.-6/K
[0049] The linear coefficients of thermal expansion of MgO and
CoFeB which are typical materials constituting a magnetic element
28 are as follows:
TABLE-US-00002 MgO 9.7 .times. 10.sup.-6/K CoFeB 12.6 .times.
10.sup.-6/K
[0050] As clear from the above descriptions, the linear
coefficients of thermal expansion of Y.sub.2O.sub.3,
Al.sub.2O.sub.3, MgO, CaO and ZrO.sub.x are close to the linear
coefficients of thermal expansion of MgO and CoFeB which are
typical materials constituting the magnetic element 28. Therefore,
by using these metallic oxides as the protective insulating film
42, the thermal stress can be reduced. Further, composites of
Y.sub.2O.sub.3, Al.sub.2O.sub.3, MgO, CaO and ZrO.sub.x can be also
used as the protective film. For example, AlMgO and AlCaO can be
used. B, C, P, etc., which can be present between lattices may be
contained. In this case, the metallic oxide protective film is
finely micro-crystalline or amorphous. The micro-crystalline or
amorphous film is preferable in terms of the reduction in
stress.
[0051] By using the above metallic oxides as the protective
insulating film 42, it is possible to reduce the stress between the
magnetic element 28 and the protective insulating film 42. Thus, a
magnetic memory device which is excellent in the characteristic and
reliability can be obtained.
[0052] The linear CTE of MgO which is a typical material
constituting the magnetic element 28 is 9.7.times.10.sup.-6/K as
mentioned above. In terms of the reduction in thermal stress, the
linear CTE of the metallic oxide is preferably greater than
approximately a half of the linear CTE of MgO. Therefore, the
linear CTE of the metallic oxide is preferably greater than
5.times.10.sup.-6/K.
[0053] All of the linear coefficients of thermal expansion of the
above-described metallic oxides are greater than
7.times.10.sup.-6/K. Therefore, the linear CTE of the metallic
oxide is more preferably greater than 7.times.10.sup.-6/K.
[0054] FIG. 4 and FIG. 5 are cross-sectional views schematically
showing a method for manufacturing the magnetic memory device
according to the second embodiment. The basic method for
manufacturing the magnetic memory device of the second embodiment
is the same as the first embodiment. Therefore, the explanations of
the matters written in the first embodiment are omitted.
[0055] First, the step of FIG. 4 is conducted. The step of FIG. 4
is the same as the step of FIG. 1 of the first embodiment. By the
step of FIG. 4, the stacked structure 30 including the magnetic
element 28 is formed.
[0056] Next, the step of FIG. 5 is conducted. In the step of FIG.
5, the protective insulating film 42 covering the stacked structure
30 is formed. Specifically, the above metallic oxides are deposited
at the temperature of approximately 300.degree. C. by means of, for
example, the MOCVD method.
[0057] Outside the protective insulating film 42, an SiN layer is
formed as an oxygen blocking layer 52. Outside the oxygen blocking
layer 52, an interlayer insulating film 54 is formed. An SiO.sub.2
film is used for the interlayer insulating film 54.
[0058] Afterward, the magnetic memory device is completed through
an interconnection step, etc.
[0059] By depositing the above-described metallic oxides, it is
possible to easily form the protective insulating film 42 covering
the stacked structure 30. Thus, the thermal stress between the
magnetic element 28 and a protective insulating film 32 can be
reduced by means of the easy method.
Embodiment 3
[0060] FIG. 8 is a cross-sectional view schematically showing a
structure of a magnetic memory device according to a third
embodiment. The basic structure of the third embodiment is the same
as the first and second embodiments. Therefore, the structural
components corresponding to the first and second embodiments are
designated by the same reference numbers and symbols. Thus, the
explanations of the matters written in the first and second
embodiments are omitted.
[0061] In the magnetic memory device of this embodiment, a
protective insulating film 44 covering a stacked structure 30 is
formed by a metallic oxide. The metal element contained in the
metallic oxide is selected from yttrium (Y), aluminum (Al),
magnesium (Mg), calcium (Ca), zirconium (Zr) and hafnium (Hf).
Specifically, as the metallic oxide, Y.sub.2O.sub.3,
Al.sub.2O.sub.3, MgO, CaO, ZrO.sub.x and HfO.sub.x can be
considered.
[0062] FIG. 6 to FIG. 8 are cross-sectional views schematically
showing a method for manufacturing the magnetic memory device
according to the third embodiment. The basic method for
manufacturing the magnetic memory device of the third embodiment is
the same as the first and second embodiments. Thus, the
explanations of the matters written in the first and second
embodiments are omitted.
[0063] First, the step of FIG. 6 is conducted. The step of FIG. 6
is the same as the step of FIG. 1 of the first embodiment. By the
step of FIG. 6, the stacked structure 30 including a magnetic
element 28 is formed.
[0064] Next, as shown in FIG. 7, a metal film 46 covering the
stacked structure 30 is formed. The metal element contained in the
metal film 46 is selected from yttrium (Y), aluminum (Al),
magnesium (Mg), calcium (Ca), zirconium (Zr) and hafnium (Hf). The
thickness of the metal film 46 is preferably greater than or equal
to 1 nm because the metal film needs to be a continuous film to
completely cover the magnetic element. After the stacked structure
30 is formed, the metal film 46 is preferably formed by the in-situ
process. In this manner, it is possible to inhibit the oxidation of
the magnetic element due to the exposure to the air. The oxidation
due to the air exposure is unstable oxidation which cannot be
controlled.
[0065] Next, as shown in FIG. 8, a metallic oxide film is formed by
oxidizing the metal film 46. By this metallic oxide film, the
protective insulating film 44 is formed. Specifically, by using
plasma oxidation including radical oxidation and ion oxidation,
etc., the metallic oxide film 44 is formed. The radical and ion
oxidations have excellent controllability by controlling plasma.
Further, the metallic oxide film 44 can be also formed by natural
oxidation.
[0066] Outside a protective insulating film 44, an SiN layer is
formed as an oxygen blocking layer 52. Outside the oxygen blocking
layer 52, an interlayer insulating film 54 is formed. An SiO.sub.2
film is used for the interlayer insulating film 54.
[0067] Afterward, the magnetic memory device is completed through
an interconnection step, etc.
[0068] Thus, by oxidizing the metal film 46 to form the metallic
oxide film (the protective insulating film 44), the thermal stress
can be inhibited. The linear CTE of the metal film 46 is close to
the linear CTE of the material contained in the magnetic element
28. Since this metal film 46 is gradually oxidized to form the
metallic oxide film 44 by obtaining atom migration (mobility), it
is possible to form the metallic oxide film (the protective
insulating film 44) without adding a large interface stress or
thermal stress between the magnetic element and the protective
film. Therefore, even if a metallic oxide film whose linear CTE is
comparatively small such as HfO.sub.x is used (the linear CTE of
HfO.sub.x is 3.8.times.10.sup.-6/K), the thermal stress can be
reduced.
[0069] The above-described metal elements contained in the metal
film 46 can more easily perform oxidation than the material
contained in the magnetic element 28. Therefore, it is possible to
easily form the metallic oxide film (the protective insulating film
44) without applying a large thermal stress.
[0070] In the first to third embodiments, the underlayer 16, the
storage layer 18, the tunnel barrier layer 20, the reference layer
22, the shift cancelling layer 24 and the cap layer 26 are included
in the stacked structure 30. However, at least only a layer
constituting the magnetic element 28 may be included in the stacked
structure 30.
[0071] Further, in the first to third embodiments, the magnetic
element 28 includes the storage layer 18, the tunnel barrier layer
20, the reference layer 22 and the shift cancelling layer 24.
However, the shift cancelling layer 24 may not be included in the
magnetic element 28. More generally, the magnetic element 28 may
only include a magnetic layer and have a storage effect.
[0072] Each of above described MTJ structures can be introduced as
MTJ elements of memory cells. Memory cells, memory cell arrays and
memory devices are disclosed in U.S. patent application Ser. No.
13/420,106. Also, the entire contents of which are incorporated by
reference herein.
[0073] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
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