U.S. patent application number 15/364147 was filed with the patent office on 2018-04-12 for method and system for providing a low moment cofebmo free layer magnetic junction usable in spin transfer torque applications.
The applicant listed for this patent is Samsung Electronics Co., Ltd.. Invention is credited to Gen Feng, Mohamad Towfik Krounbi, Donkoun Lee, Xueti Tang.
Application Number | 20180102474 15/364147 |
Document ID | / |
Family ID | 61801312 |
Filed Date | 2018-04-12 |
United States Patent
Application |
20180102474 |
Kind Code |
A1 |
Tang; Xueti ; et
al. |
April 12, 2018 |
METHOD AND SYSTEM FOR PROVIDING A LOW MOMENT CoFeBMo FREE LAYER
MAGNETIC JUNCTION USABLE IN SPIN TRANSFER TORQUE APPLICATIONS
Abstract
A magnetic junction and method for providing the magnetic
junction are described. The magnetic junction resides on a
substrate and is usable in a magnetic device. The magnetic junction
includes free and pinned layers separated by a nonmagnetic spacer
layer. The free layer is switchable between stable magnetic states
when a write current is passed through the magnetic junction. The
free layer has a free layer perpendicular magnetic anisotropy
energy greater than a free layer out-of-plane demagnetization
energy. The free layer includes a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer, where u+t=1, x+y+z=1
and u, t, x, y and z are each nonzero. The
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer has a perpendicular
magnetic anisotropy energy greater than its out-of-plane
demagnetization energy.
Inventors: |
Tang; Xueti; (Fremont,
CA) ; Krounbi; Mohamad Towfik; (San Jose, CA)
; Lee; Donkoun; (San Jose, CA) ; Feng; Gen;
(North Potomac, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd. |
Gyeonggi-do |
|
KR |
|
|
Family ID: |
61801312 |
Appl. No.: |
15/364147 |
Filed: |
November 29, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62405589 |
Oct 7, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 43/12 20130101;
H01L 41/00 20130101; H01L 27/20 20130101; H01L 43/08 20130101; H01L
43/10 20130101; G11C 11/161 20130101; H01L 27/22 20130101; H01L
27/228 20130101 |
International
Class: |
H01L 43/08 20060101
H01L043/08; H01L 43/10 20060101 H01L043/10; H01L 43/12 20060101
H01L043/12; H01L 27/22 20060101 H01L027/22; G11C 11/16 20060101
G11C011/16 |
Claims
1. A magnetic junction residing on a substrate and usable in a
magnetic device comprising: a pinned layer; a nonmagnetic spacer
layer; and a free layer, the free layer being switchable between a
plurality of stable magnetic states when a write current is passed
through the magnetic junction, the nonmagnetic spacer layer
residing between the pinned layer and the free layer, the free
layer having a free layer perpendicular magnetic anisotropy energy
greater than a free layer out-of-plane demagnetization energy, the
free layer including a [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t
layer, where u+t=1 and x+y+z=1 and wherein u, t, x, y and z are
each nonzero, the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer
having a [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer
perpendicular magnetic anisotropy energy greater than a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer out-of-plane
demagnetization energy.
2. The magnetic junction of claim 1 wherein the free layer consists
of the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer.
3. The magnetic junction of claim 1 wherein the free layer also
includes and at least one of at least one CoFeB layer and at least
one FeB layer.
4. The magnetic junction of claim 1 where t is not more than 0.50
and at least 0.05.
5. The magnetic junction of claim 4 wherein t is not more than
0.2.
6. The magnetic junction of claim 4 wherein t is at least 0.1 and
not more than 0.15.
7. The magnetic junction of claim 1 wherein the alloy is a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer, having a thickness
of at least thirteen Angstroms and not more than forty
Angstroms.
8. The magnetic junction of claim 7 wherein the thickness is at
least fifteen Angstroms and not more than twenty Angstroms.
9. The magnetic junction of claim 7 wherein the thickness is
greater than twenty Angstroms.
10. The magnetic junction of claim 1 wherein the nonmagnetic spacer
layer includes MgO and adjoins the free layer.
11. The magnetic junction of claim 1 further comprising: at least
one of a seed layer adjoining the free layer and a capping layer
adjoining the free layer, the seed layer and the capping layer each
including at least one of magnesium oxide, tantalum oxide,
molybdenum oxide and vanadium oxide.
12. The magnetic junction of claim 1 further comprising: an
additional nonmagnetic spacer layer, the free layer being between
the additional nonmagnetic spacer layer and the nonmagnetic spacer
layer; and an additional pinned layer, the additional nonmagnetic
spacer layer being between the additional pinned layer and the free
layer.
13. A magnetic memory residing on a substrate and comprising: a
plurality of magnetic storage cells, each of the plurality of
magnetic storage cells including at least one magnetic junction
including a pinned layer, a nonmagnetic spacer layer and a free
layer, the free layer being switchable between a plurality of
stable magnetic states when a write current is passed through the
magnetic junction, the nonmagnetic spacer layer residing between
the pinned layer and the free layer, the free layer having a free
layer perpendicular magnetic anisotropy energy greater than a free
layer out-of-plane demagnetization energy, the free layer including
a [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer where u+t=1 and
x+y+z=1, and wherein u, t, x, y and z are each nonzero, the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer having a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer perpendicular
magnetic anisotropy energy greater than a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer out-of-plane
demagnetization energy; a plurality of bit lines coupled with the
plurality of magnetic storage cells.
14. A method for providing magnetic junction residing on a
substrate and usable in a magnetic device, the method comprising:
providing a pinned layer; providing a nonmagnetic spacer layer, and
providing a free layer, the free layer being switchable between a
plurality of stable magnetic states when a write current is passed
through the magnetic junction, the nonmagnetic spacer layer
residing between the pinned layer and the free layer, the free
layer having a free layer perpendicular magnetic anisotropy energy
greater than a free layer out-of-plane demagnetization energy, the
free layer including a [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t
layer, where u+t=1 and x+y+z=1 and wherein u, t, x, y and z are
each nonzero, the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer
having a [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer
perpendicular magnetic anisotropy energy greater than a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer out-of-plane
demagnetization energy.
15. The method of claim 14 wherein the step of providing the free
layer further includes: providing at least one of at least one
CoFeB layer and at least one FeB layer.
16. The method of claim 14 where t is not more than 0.20 and at
least 0.05.
17. The method of claim 14 wherein the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer has a thickness of at
least thirteen Angstroms and not more than forty Angstroms.
18. The method of claim 14 wherein the step of providing
nonmagnetic spacer layer includes: providing an MgO layer adjoining
the free layer.
19. The method of claim 14 further comprising: providing at least
one of a seed layer adjoining the free layer and a capping layer
adjoining the free layer, the seed layer and the capping layer each
including at least one of a magnesium oxide layer, a tantalum oxide
layer, molybdenum oxide and a vanadium oxide layer.
20. The method of claim 14 further comprising: providing an
additional nonmagnetic spacer layer, the free layer being between
the additional nonmagnetic spacer layer and the nonmagnetic spacer
layer; and providing an additional pinned layer, the additional
nonmagnetic spacer layer being between the additional pinned layer
and the free layer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of provisional Patent
Application Ser. No. 62/405,589, filed Oct. 7, 2016, entitled
CoFeBMo FOR PERPENDICULAR MAGNETIC TUNNELING JUNCTION, assigned to
the assignee of the present application, and incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] Magnetic memories, particularly magnetic random access
memories (MRAMs), have drawn increasing interest due to their
potential for high read/write speed, excellent endurance,
non-volatility and low power consumption during operation. An MRAM
can store information utilizing magnetic materials as an
information recording medium. One type of MRAM is a spin transfer
torque random access memory (STT-MRAM). STT-MRAM utilizes magnetic
junctions written at least in part by a current driven through the
magnetic junction. A spin polarized current driven through the
magnetic junction exerts a spin torque on the magnetic moments in
the magnetic junction. As a result, layer(s) having magnetic
moments that are responsive to the spin torque may be switched to a
desired state.
[0003] For example, a conventional magnetic tunneling junction
(MTJ) may be used in a conventional STT-MRAM. The conventional MTJ
typically resides on a substrate. The conventional MTJ, uses
conventional seed layer(s), may include capping layers and may
include a conventional antiferromagnetic (AFM) layer. The
conventional MTJ includes a conventional pinned layer, a
conventional free layer and a conventional tunneling barrier layer
between the conventional pinned and free layers. A bottom contact
below the conventional MTJ and a top contact on the conventional
MTJ may be used to drive current through the conventional MTJ in a
current-perpendicular-to-plane (CPP) direction.
[0004] The conventional pinned layer and the conventional free
layer are magnetic. The magnetization of the conventional pinned
layer is fixed, or pinned, in a particular direction. The
conventional free layer has a changeable magnetization. The
conventional free layer may be a single layer or include multiple
layers.
[0005] To switch the magnetization of the conventional free layer,
a current is driven perpendicular to plane. When a sufficient
current is driven from the top contact to the bottom contact, the
magnetization of the conventional free layer may switch to be
parallel to the magnetization of a conventional bottom pinned
layer. When a sufficient current is driven from the bottom contact
to the top contact, the magnetization of the free layer may switch
to be antiparallel to that of the bottom pinned layer. The
differences in magnetic configurations correspond to different
magnetoresistances and thus different logical states (e.g. a
logical "0" and a logical "1") of the conventional MTJ.
[0006] Because of their potential for use in a variety of
applications, research in magnetic memories is ongoing. Mechanisms
for improving the performance of STT-MRAM are desired. For example,
a lower switching current may be desired for easier and faster
switching. Concurrently, the magnetic junction is desired to remain
thermally stable. Accordingly, what is needed is a method and
system that may improve the performance of the spin transfer torque
based memories. The method and system described herein address such
a need.
BRIEF SUMMARY OF THE INVENTION
[0007] A magnetic junction and method for providing the magnetic
junction are described. The magnetic junction resides on a
substrate and is usable in a magnetic device. The magnetic junction
includes free and pinned layers separated by a nonmagnetic spacer
layer. The free layer is switchable between stable magnetic states
when a write current is passed through the magnetic junction. The
free layer has a free layer perpendicular magnetic anisotropy
energy greater than a free layer out-of-plane demagnetization
energy. The free layer includes an alloy. The alloy includes
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t, where u+t=1 and x+y+z=1.
Further, u, t, x, y and z are each nonzero.
[0008] The magnetic junction having the free layer including a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer may have improved
performance. Such a free layer may have a reduced saturation
magnetization while maintaining a high magnetic anisotropy. As a
result, switching current may be reduced. The reduction in
switching current may also improve other aspects of performance,
such as switching speed. Thus, performance of the magnetic junction
and magnetic device employing such a free layer may be enhance.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0009] FIG. 1 depicts an exemplary embodiment of a magnetic
junction usable in a magnetic devices such as a magnetic memory
programmable using spin transfer torque and having a CoFeBMo free
layer.
[0010] FIG. 2 depicts an exemplary embodiment of a CoFeBMo free
layer usable in a magnetic junction.
[0011] FIG. 3 depicts another exemplary embodiment of a CoFeBMo
free layer usable in a magnetic junction.
[0012] FIG. 4 depicts another exemplary embodiment of a CoFeBMo
free layer usable in a magnetic junction.
[0013] FIG. 5 depicts another exemplary embodiment of a magnetic
junction usable in a magnetic devices such as a magnetic memory
programmable using spin transfer torque and having a CoFeBMo free
layer.
[0014] FIG. 6 depicts an exemplary embodiment of a magnetic
junction usable in a magnetic devices such as a magnetic memory
programmable using spin transfer torque and having a CoFeBMo free
layer.
[0015] FIG. 7 is a flow chart depicting an exemplary embodiment of
a method for providing a magnetic junction usable in a magnetic
devices such as a magnetic memory programmable using spin transfer
torque and having a CoFeBMo free layer including.
[0016] FIG. 8 is a flow chart depicting an exemplary embodiment of
a method for providing a CoFeBMo free layer.
[0017] FIG. 9 depicts an exemplary embodiment of a memory utilizing
magnetic junctions in the memory element(s) of the storage
cell(s).
DETAILED DESCRIPTION OF THE INVENTION
[0018] The exemplary embodiments relate to magnetic junctions
usable in magnetic devices, such as magnetic memories, and the
devices using such magnetic junctions. The magnetic memories may
include spin transfer torque magnetic random access memories
(STT-MRAMs) and may be used in electronic devices employing
nonvolatile memory. Such electronic devices include but are not
limited to cellular phones, smart phones, tables, laptops and other
portable and non-portable computing devices. The following
description is presented to enable one of ordinary skill in the art
to make and use the invention and is provided in the context of a
patent application and its requirements. Various modifications to
the exemplary embodiments and the generic principles and features
described herein will be readily apparent. The exemplary
embodiments are mainly described in terms of particular methods and
systems provided in particular implementations. However, the
methods and systems will operate effectively in other
implementations. Phrases such as "exemplary embodiment", "one
embodiment" and "another embodiment" may refer to the same or
different embodiments as well as to multiple embodiments. The
embodiments will be described with respect to systems and/or
devices having certain components. However, the systems and/or
devices may include more or less components than those shown, and
variations in the arrangement and type of the components may be
made without departing from the scope of the invention. The
exemplary embodiments will also be described in the context of
particular methods having certain steps. However, the method and
system operate effectively for other methods having different
and/or additional steps and steps in different orders that are not
inconsistent with the exemplary embodiments. Thus, the present
invention is not intended to be limited to the embodiments shown,
but is to be accorded the widest scope consistent with the
principles and features described herein.
[0019] A magnetic junction and method for providing the magnetic
junction are described. The magnetic junction resides on a
substrate and is usable in a magnetic device. The magnetic junction
includes free and pinned layers separated by a nonmagnetic spacer
layer. The free layer is switchable between stable magnetic states
when a write current is passed through the magnetic junction. The
free layer has a free layer perpendicular magnetic anisotropy
energy greater than a free layer out-of-plane demagnetization
energy. The free layer includes a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer, where u+t=1, x+y+z=1
and u, t, x, y and z are each nonzero. The
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer has a perpendicular
magnetic anisotropy energy greater than its out-of-plane
demagnetization energy.
[0020] The exemplary embodiments are described in the context of
particular methods, magnetic junctions and magnetic memories having
certain components. One of ordinary skill in the art will readily
recognize that the present invention is consistent with the use of
magnetic junctions and magnetic memories having other and/or
additional components and/or other features not inconsistent with
the present invention. The method and system are also described in
the context of current understanding of the spin transfer
phenomenon, of magnetic anisotropy, and other physical phenomenon.
Consequently, one of ordinary skill in the art will readily
recognize that theoretical explanations of the behavior of the
method and system are made based upon this current understanding of
spin transfer, magnetic anisotropy and other physical phenomena.
However, the method and system described herein are not dependent
upon a particular physical explanation. One of ordinary skill in
the art will also readily recognize that the method and system are
described in the context of a structure having a particular
relationship to the substrate. However, one of ordinary skill in
the art will readily recognize that the method and system are
consistent with other structures. In addition, the method and
system are described in the context of certain layers being
synthetic and/or simple. However, one of ordinary skill in the art
will readily recognize that the layers could have another
structure. Furthermore, the method and system are described in the
context of magnetic junctions and/or substructures having
particular layers. However, one of ordinary skill in the art will
readily recognize that magnetic junctions and/or substructures
having additional and/or different layers not inconsistent with the
method and system could also be used. Moreover, certain components
are described as being magnetic, ferromagnetic, and ferrimagnetic.
As used herein, the term magnetic could include ferromagnetic,
ferrimagnetic or like structures. Thus, as used herein, the term
"magnetic" or "ferromagnetic" includes, but is not limited to
ferromagnets and ferrimagnets. As used herein, "in-plane" is
substantially within or parallel to the plane of one or more of the
layers of a magnetic junction. Conversely, "perpendicular" and
"perpendicular-to-plane" corresponds to a direction that is
substantially perpendicular to one or more of the layers of the
magnetic junction.
[0021] FIG. 1 depicts an exemplary embodiment of a magnetic
junction 100 usable in a magnetic devices and having a CoFeBMo free
layer. For clarity, FIG. 1 is not to scale. The magnetic junction
100 may be used in a magnetic device such as a spin transfer torque
magnetic random access memory (STT-MRAM) and, therefore, in a
variety of electronic devices. The magnetic junction 100 may
include a pinned layer 104 having a magnetic moment 105, a
nonmagnetic spacer layer 106, a free layer 108 having magnetic
moment 109, an optional additional nonmagnetic spacer layer 110,
and an optional additional pinned layer 112 having magnetic moment
113. Also shown are optional seed layer(s) 102 and capping layer(s)
114. The substrate 101 on which the magnetic junction 100 is formed
resides below the seed layers. A bottom contact and a top contact
are not shown but may be formed. Similarly, other layers may be
present but are not shown for simplicity.
[0022] As can be seen in FIG. 1, the magnetic junction 100 is a
dual magnetic junction. In another embodiment, the nonmagnetic
spacer layer 110 and pinned layer 112 might be omitted. In such an
embodiment, the magnetic junction 100 is a bottom pinned magnetic
junction. Alternatively, the pinned layer 104 and nonmagnetic
spacer layer 106 might be omitted. In such an embodiment, the
magnetic junction 100 is a top pinned magnetic junction. Optional
pinning layer(s) (not shown) may be used to fix the magnetization
of the pinned layer(s) 104 and/or 112. In some embodiments, the
optional pinning layer may be an AFM layer or multilayer that pins
the magnetization(s) through an exchange-bias interaction. However,
in other embodiments, the optional pinning layer may be omitted or
another structure may be used. In the embodiment shown, the
magnetic moments 105 and 113 of the pinned layers 104 and 112,
respectively, are pinned by the magnetic anisotropy of the layers
104 and 112, respectively. The free layer 108 and the pinned layers
104 and 112 have a high perpendicular magnetic anisotropy. Stated
differently, the perpendicular magnetic anisotropy energy exceeds
the out-of-plane demagnetization energy for the layers 104, 108 and
112. Such a configuration allows for the magnetic moments 105, 109
and 113 of the layers 104, 108 and 112, respectively, having a high
perpendicular magnetic anisotropy to be stable perpendicular to
plane. Stated differently, the magnetic moments of the free layer
108 and pinned layer(s) 104 and 112 are stable out-of-plane.
[0023] The magnetic junction 100 is also configured to allow the
free layer magnetic moment 109 to be switched between stable
magnetic states when a write current is passed through the magnetic
junction 100. Thus, the free layer 109 is switchable utilizing spin
transfer torque when a write current is driven through the magnetic
junction 100 in a current perpendicular-to-plane (CPP) direction.
The direction of the magnetic moment 109 of the free layer 108 may
be read by driving a read current through the magnetic junction
100.
[0024] The nonmagnetic spacer layer(s) 106 and 110 may be tunneling
barrier layers. For example, the nonmagnetic spacer layer 106
and/or 110 may be a crystalline MgO tunneling barrier with a (100)
orientation. Such nonmagnetic spacer layers 106 and 110 may enhance
TMR of the magnetic junction 100. The nonmagnetic spacer layer(s)
106 and 110 may also be considered to serve as seed and capping
layers for the free layer 108.
[0025] The pinned layer(s) 104 and/or 112 have a perpendicular
magnetic anisotropy energy greater than a pinned layer out-of-plane
demagnetization energy. Thus, the moments 105 and 113 are stable
perpendicular-to-plane. In alternate embodiments, the magnetic
moment(s) 105 and/or 113 may be stable in-plane. The pinned layers
104 and 112 are shown as being simple, single layers. However, in
other embodiments, the pinned layer(s) 104 and/or 112 may be
multilayer(s). For example, the pinned layer(s) 104 and/or 112
might be a synthetic antiferromagnet (SAF) including two
magnetically coupled ferromagnetic layers separated by and
sandwiching a nonmagnetic layer, such as Ru. Alternatively, the
pinned layer(s) 104 and/or 112 may be high perpendicular anisotropy
(H.sub.k) multilayer(s). For example, the pinned layer 104 may be a
Co/Pt multilayer. Other pinned layer(s) having other structures may
be used. In addition, in alternate embodiments, the pinned layer
102 and/or 112 may have the magnetic moment(s) 105 and/or 113, in
plane.
[0026] The free layer 108 includes a CoFeBMo alloy. Thus, the free
layer may consist of a CoFeBMo alloy layer or may have additional
layers. As used herein, a "CoFeBMo" layer is one which includes Co,
Fe, B and Mo but in which the ratios between the constituents is
not specified. Similarly, CoFeB refers to a mixture including Co,
Fe and B but in which the ratios between the constituents is not
specified, but may be in the ranges disclosed herein. CoFeBMo may
be the same as to [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t, where
the subscripts refer to atomic percentages, u+t=1 and x+y+z=1. In
addition, u, t, x, y and t are each nonzero. In some embodiments, t
is at least 0.05 and not more than 0.5. In some embodiments, t is
at least 0.05 and not more than 0.2. In some embodiments, t is at
least 0.1 and not more than 0.15. Thus, the alloy may include not
more than fifteen atomic percent Mo in some embodiments. As a
result, the free layer 108 may have a reduced saturation
magnetization (M.sub.s). Stated differently, the M.sub.s of the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t alloy is less than one
thousand emu/cc. In some embodiments, the saturation magnetization
may be less than six hundred emu/cc. In addition, the B content in
the Co may be desired to be limited to a particular range. In some
embodiments, the CoFeB includes at least ten atomic percent and not
more than sixty atomic percent B (i.e. z is at least 0.1 and not
more than 0.6). In some such embodiments, the CoFeB includes at
least fifteen percent and not more than forty atomic percent B.
[0027] The [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t alloy may form a
layer in the free layer 108. In some embodiments, the free layer
108 consists of the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer.
In other embodiments, free layer 108 includes the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer as well as one or
more other layers. For example, the free layer may include a CoFeB
and/or an FeB layer. Thus, the free layer 108 may include a
CoFeB/[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t/FeB trilayer, a
CoFeB/[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t/CoFeB trilayer, a
FeB/[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t/FeB trilayer, a
CoFeB/[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t bilayer, and/or a
FeB/[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t bilayer. The
relationship to the substrate is not fixed. Thus, for the
CoFeB/[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t/FeB trilayer, the FeB
layer may be closest to the substrate 101 in some embodiments or
furthest from the substrate in other embodiments.
[0028] As can be seen in FIG. 1, the free layer 108 has a
perpendicular magnetic anisotropy that exceeds the out-of-plane
demagnetization energy. Thus, the magnetic moment 109 of the free
layer 108 may be oriented substantially perpendicular-to-plane. The
perpendicular anisotropy of the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer within the free layer
108 is also high. Thus, the perpendicular magnetic anisotropy
energy of the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer exceeds
its out-of-plane demagnetization energy. Without more, therefore,
the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer would have its
moment oriented perpendicular to plane. This is may be the case
even if high perpendicular magnetic anisotropy layers, such as
CoFeB layers, are not used in the free layer 108. In some
embodiments, the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer may
have a thickness of at least thirteen Angstroms and not more than
forty Angstroms while having its moment out-of-plane. In some such
embodiments, the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer of
the free layer 108 may have a thickness that does not exceed twenty
Angstroms while maintaining an out-of-plane magnetic moment. In
some cases, the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer may
be at least fifteen Angstroms. Alternatively, the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer of the free layer may
be greater than twenty Angstroms thick while having an out-of-plane
magnetic moment. Thus, the perpendicular magnetic anisotropy may be
higher than the out-of-plane demagnetization energy may occur for
higher thicknesses of the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t
layer.
[0029] The layers surrounding the free layer 108 may be tailored to
aid the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer and the free
layer in maintaining a high perpendicular magnetic anisotropy. For
example, a seed layer and/or capping layer may be selected from a
set of materials in order to enhance the perpendicular magnetic
anisotropy energy. In some embodiments, such a seed layer may
include one or more of magnesium oxide, tantalum oxide, molybdenum
oxide and vanadium oxide. Similarly, the capping layer may include
one or more of a magnesium oxide layer, a tantalum oxide layer, a
molybdenum oxide layer and a vanadium oxide layer. For example, in
the dual magnetic junction 100 depicted in FIG. 1, the nonmagnetic
spacers 106 and 110 may each be crystalline MgO tunneling barrier
layers. Thus, the seed and capping layers would correspond to the
nonmagnetic spacer layers 106 and 110, respectively and may consist
of MgO. Such nonmagnetic spacer layers 106 and 110 not only improve
tunneling magnetoresistance, but may also aid in increasing the
perpendicular magnetic anisotropy of the free layer 108. If the
layers 110 and 112 are omitted, then the capping layer 104 may
include a magnesium oxide layer, a tantalum oxide layer, a
molybdenum oxide layer and a vanadium oxide layer. It the layers
104 and 106 are omitted, then the seed layer 102 may include one or
more of magnesium oxide, tantalum oxide, molybdenum oxide and
vanadium oxide. Such configurations may further enhance the
perpendicular magnetic anisotropy energy of the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer. Thus, the free layer
magnetic moment 109 may have its stable states substantially
perpendicular-to-plane.
[0030] The magnetic junction 100 having the free layer 108
including a [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t alloy may have
improved performance. The free layer 108 may have a reduced
saturation magnetization due to the low moment
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer. For example,
saturation magnetizations as low as 550 emu/cc may be obtained.
However, the high perpendicular magnetic anisotropy may be
maintained. For example, a magnetic anisotropy on the order of one
Tesla may still be present. The
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer may also have a low
damping coefficient, for example as low as 0.005 or lower. As a
result, switching current may be reduced. Consequently, the free
layer may be thermally stable when quiescent (not being written).
The reduction in switching current may also improve other aspects
of performance, such as switching speed. Thus, performance of the
magnetic junction and magnetic device employing such a free layer
may be enhanced.
[0031] FIG. 2 depicts an exemplary embodiment of a free layer 120
usable in a magnetic devices such as a magnetic memory programmable
using spin transfer torque. For clarity, FIG. 2 is not to scale.
The free layer 120 may be used as the free layer 108 in the
magnetic junction 100. The free layer 120 includes a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122. In some
embodiments, the free layer 120 consists of the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122. In other
embodiments, additional layer(s) might be present. Also shown are
seed layer(s) 131 and capping layer(s) 132. However, these layers
131 and 132 are not considered part of the free layer 120.
[0032] The [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122 is
analogous to that described above. Thus, in the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122, u, t, x, y and t
are each nonzero. The [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer
122 is an alloy, rather than a multilayer. In some embodiments, t
is at least 0.05 and not more than 0.5. In some embodiments, t is
at least 0.1 and not more than 0.2. In some embodiments, t is not
more than 0.15. In such an embodiment, the reduction in saturation
magnetization may be optimized. For example, the M.sub.s of the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122 may be less than
six hundred emu/cc.
[0033] The [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122 and
the free layer 120 each has a perpendicular magnetic anisotropy
that exceeds the out-of-plane demagnetization energy. Thus, the
free layer magnetic moment 121 may have its stable states
substantially perpendicular-to-plane. The
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122 may have a
thickness as described above. Thus, in some embodiments, the
thickness of the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122
may be greater than twenty Angstroms, and in some embodiments may
be 30-40 Angstroms, while maintaining a perpendicular-to-plane
magnetic moment. In addition, the layers surrounding the free layer
120 may be tailored to aid the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122 and the free
layer 120 in maintaining a high perpendicular magnetic anisotropy.
For example, the seed layer 131 may include one or more of a
magnesium oxide layer, a tantalum oxide layer, molybdenum oxide and
a vanadium oxide layer. Similarly, the capping layer 132 may
include one or more of a magnesium oxide layer, a tantalum oxide
layer, molybdenum oxide and a vanadium oxide layer. The material
selected may depend upon the type of magnetic junction (dual,
bottom pinned or top pinned) and the location of the free layer
120.
[0034] A magnetic junction including the free layer 120 may have
improved performance. The free layer 120 may have a reduced
saturation magnetization due to the low moment of the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 124. However, the
high perpendicular magnetic anisotropy may be maintained. As a
result, switching current may be reduced. The perpendicular
magnetic anisotropy may remain high. Consequently, the free layer
120 may be thermally stable when quiescent. Thus, performance of a
magnetic junction and magnetic device employing such a free layer
120 may be improved.
[0035] FIG. 3 depicts another exemplary embodiment of a free layer
120' usable in a magnetic devices such as a magnetic memory
programmable using spin transfer torque. For clarity, FIG. 3 is not
to scale. The free layer 120' may be used as the free layer 108 in
the magnetic junction 100. The free layer 120' is analogous to the
free layer 120. Consequently, similar components have analogous
labels. The free layer 120' includes a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122' and an
additional layer 124. The layer 124 may be a CoFeB layer or an FeB
layer. In some embodiments, the CoFeB or FeB layer 124 includes at
least ten and not more than sixty atomic percent B. In some cases,
the CoFeB or FeB layer 124 has not more than thirty atomic percent
B. In some embodiments, additional layer(s) might be present in the
free layer 120'. In the embodiment shown, the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122' is furthest from
the substrate (not shown). In an alternate embodiment, the order of
the layers 122' and 124 may be reversed. Thus, the CoFeB/FeB layer
124 might be furthest from the substrate. Also shown are seed
layer(s) 131' and capping layer(s) 132' that are analogous to the
seed layer(s) 131 and the capping layer(s) 132, respectively.
However, these layers 131' and 132' are not considered part of the
free layer 120'.
[0036] The [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122' is
analogous to that described above. Thus, in the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122', u, t, x, y and
t are each nonzero. The [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t
layer 122' is an alloy, rather than a multilayer. In some
embodiments, t is at least 0.05 and not more than 0.5. In some such
embodiments, t is at least 0.1 and not more than 0.2. For example,
t may be not more than 0.15.
[0037] The [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122' and
the free layer 120' each has a perpendicular magnetic anisotropy
that exceeds the out-of-plane demagnetization energy. Thus, the
free layer magnetic moment 121' may have its stable states
substantially perpendicular-to-plane. The
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122' may have a
thickness of at least thirteen Angstroms and not more than forty
Angstroms. In some such embodiments, the thickness of the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122' is at least
fifteen Angstroms and does not exceed twenty Angstroms. Thus, in
some embodiments, the thickness of the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122' may be greater
than twenty Angstroms.
[0038] The CoFeB layer or FeB layer 124 may also be desired to be
thin. In some embodiments, the CoFeB layer or FeB layer 124 is also
at least three Angstroms thick and not more than ten Angstroms
thick.
[0039] The layers surrounding the free layer 120' may be tailored
to help the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122' and
the free layer 120' have a high perpendicular magnetic anisotropy.
The seed layer 131' may include one or more of a magnesium oxide
layer, a tantalum oxide layer, a molybdenum oxide and a vanadium
oxide layer. Similarly, the capping layer 132' may include one or
more of a magnesium oxide layer, a tantalum oxide layer, a
molybdenum oxide and a vanadium oxide layer. The material selected
may depend upon the type of magnetic junction (dual, bottom pinned
or top pinned) and the location of the free layer 120'.
[0040] A magnetic junction including the free layer 120' may have
improved performance. The free layer 120' may have a reduced
saturation magnetization due to the low moment of the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122'. However, the
high perpendicular magnetic anisotropy may be maintained. The
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122' may also have
low damping. As a result, switching current may be reduced. The
perpendicular magnetic anisotropy may remain high. Consequently,
the free layer 120' may be thermally stable when quiescent. Thus,
performance of a magnetic junction and magnetic device employing
such a free layer 120' may be improved.
[0041] FIG. 4 depicts another exemplary embodiment of a free layer
120'' usable in a magnetic devices such as a magnetic memory
programmable using spin transfer torque. For clarity, FIG. 4 is not
to scale. The free layer 120'' may be used as the free layer 108 in
the magnetic junction 100. The free layer 120'' is analogous to the
free layer(s) 120 and/or 120'. Consequently, similar components
have analogous labels. The free layer 120'' includes a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122'' and a CoFeB or
FeB layer 124' that are analogous to the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122/122' and the
CoFeB or FeB layer 124, respectively of the free layer 120/120'. In
addition, another CoFeB or FeB layer 126 is also shown. Thus, the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122'' is sandwiched
between two layers. The free layer 120'' may be a
CoFeB/[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t/CoFeB trilayer, a
CoFeB/[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t/FeB trilayer,
FeB/[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t/CoFeB trilayer, or a
FeB/[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t/FeB trilayer. Also
shown are seed layer(s) 131'' and capping layer(s) 132'' that are
analogous to the seed layer(s) 131/131' and the capping layer(s)
132/132', respectively. However, these layers 131'' and 132'' are
not considered part of the free layer 120''.
[0042] The [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122'' is
analogous to that described above. Thus, in the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122'', u, t, x, y and
t are each nonzero. The [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t
layer 122'' is an alloy, rather than a multilayer. In some
embodiments, t is at least 0.05 and not more than 0.5. In some such
embodiments, t is at least 0.1 and not more than 0.2. For example,
t may be not more than 0.15. The
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122'' and the free
layer 120'' each has a perpendicular magnetic anisotropy that
exceeds the out-of-plane demagnetization energy. Thus, the free
layer magnetic moment 121'' may have its stable states
substantially perpendicular-to-plane. The
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122'' may have a
thickness of at least thirteen Angstroms and not more than forty
Angstroms. In some such embodiments, the thickness of the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122'' is at least
fifteen Angstroms and does not exceed twenty Angstroms. Thus, in
some embodiments, the thickness of the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 122'' may be greater
than twenty Angstroms.
[0043] In some embodiments, the CoFeB or FeB layer 124' includes at
least ten and not more than sixty atomic percent B. In some cases,
the CoFeB or FeB layer 124' has not more than thirty atomic percent
B. The CoFeB or FeB layer 124' may also be desired to be thin. In
some embodiments, the CoFeB or FeB layer 124' is also at least
three Angstroms thick and not more than ten Angstroms thick.
Similarly, the CoFeB or FeB layer 126 may have a thickness and
stoichiometry in the same range as that of the layer 124'.
[0044] The layers surrounding the free layer 120'' may be tailored
to aid in ensuring that the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t
layer 122'' and the free layer 120'' have a high perpendicular
magnetic anisotropy. For example, the seed layer 131'' may include
one or more of magnesium oxide, tantalum oxide, molybdenum oxide
and vanadium oxide. The capping layer 132'' may include one or more
of a magnesium oxide layer, a tantalum oxide layer, a molybdenum
oxide and a vanadium oxide layer. The material selected may depend
upon the type of magnetic junction (dual, bottom pinned or top
pinned) and the location of the free layer 120''.
[0045] A magnetic junction including the free layer 120'' may have
improved performance. The free layer 120'' may have a reduced
saturation magnetization due to the low moment of the
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 124''. The high
perpendicular magnetic anisotropy may be maintained. The
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t layer 124'' may also have
low damping. As a result, switching current may be reduced. The
perpendicular magnetic anisotropy may remain high. Consequently,
the free layer 120'' may be thermally stable when quiescent. Thus,
performance of a magnetic junction and magnetic device employing
such a free layer 120'' may be improved.
[0046] FIG. 5 depicts another exemplary embodiment of a magnetic
junction 100' in a magnetic devices such as a magnetic memory
programmable using spin transfer torque. For clarity, FIG. 5 is not
to scale. The magnetic junction 100' is analogous to the magnetic
junction 100. Consequently, similar components have analogous
labels. The magnetic junction 100' is a bottom pinned magnetic
junction including pinned layer 104, nonmagnetic spacer layer 106
and free layer 108' that are analogous to the pinned layer 104,
nonmagnetic spacer layer 106 and free layer 108, respectively.
Optional seed layer 102 and capping layer 114' are also shown.
[0047] The free layer 108' includes a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t alloy. In some embodiments,
the free layer 108' may be the free layer 120, 120' or 120''. In
order to improve the perpendicular magnetic anisotropy of the free
layer 108', the nonmagnetic spacer layer 106 is desired to be a
crystalline MgO layer. Thus, the nonmagnetic spacer layer 106 also
serves as a seed layer 131/131'/131''. Such a crystalline MgO
tunneling barrier layer 106 may also improve tunneling
magnetoresistance and, therefore, signal from the magnetic junction
100'. The capping layers 114' are desired to be analogous to the
layer(s) 132, 132' and/or 132''. Thus, the capping layer(s) 114'
may include one or more of a magnesium oxide layer, a tantalum
oxide layer, a magnesium oxide/tantalum oxide bilayer and a
titanium oxide layer.
[0048] The magnetic junction 100' may have improved performance.
The free layer 108' may have a reduced saturation magnetization due
to the low moment of the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t
layer. However, the high perpendicular magnetic anisotropy and,
therefore, the out-of-plane magnetic moment 109 may be maintained.
The free layer 108' may also have low damping. As a result,
switching current may be reduced. The perpendicular magnetic
anisotropy may remain high. Thus, performance of a magnetic
junction 100' and magnetic device employing the magnetic junction
100' may be improved.
[0049] FIG. 6 depicts another exemplary embodiment of a magnetic
junction 100'' in a magnetic devices such as a magnetic memory
programmable using spin transfer torque. For clarity, FIG. 6 is not
to scale. The magnetic junction 100'' is analogous to the magnetic
junction(s) 100 and/or 100'. Consequently, similar components have
analogous labels. The magnetic junction 100'' is a top pinned
magnetic junction including free layer 108', nonmagnetic spacer
layer 110 and pinned layer 112 that are analogous to the free layer
108/108', nonmagnetic spacer layer 110 and pinned layer 112.
Optional seed layer 102 and capping layer 114' are also shown.
[0050] The free layer 108' includes a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t alloy layer. In some
embodiments, the free layer 108' may be the free layer 120, 120' or
120''. In order to improve the perpendicular magnetic anisotropy of
the free layer 108', the nonmagnetic spacer layer 110 is desired to
be a crystalline MgO layer. Thus, the nonmagnetic spacer layer 110
also serves as a capping layer 132/132'/132''. Such a crystalline
MgO tunneling barrier layer 110 may also improve tunneling
magnetoresistance and, therefore, signal from the magnetic junction
100''. The seed layers 102' are desired to be analogous to the
layer(s) 131, 131' and/or 131''. Thus, the seed layer(s) 102' may
include one or more of magnesium oxide, tantalum oxide and titanium
oxide.
[0051] The magnetic junction 100'' may have improved performance.
The free layer 108' may have a reduced saturation magnetization due
to the low moment of the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t
layer. However, the high perpendicular magnetic anisotropy and,
therefore, the out-of-plane magnetic moment 109 may be maintained.
The free layer 108' may also have low damping. As a result,
switching current may be reduced. The perpendicular magnetic
anisotropy may remain high. Thus, performance of a magnetic
junction 100'' and magnetic device employing the magnetic junction
100'' may be improved.
[0052] FIG. 7 is a flow chart depicting an exemplary embodiment of
a method 200 for providing a layer for magnetic junction usable in
a magnetic device and including a
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t alloy layer within the free
layer. For simplicity, some steps may be omitted, performed in
another order, include substeps and/or combined. Further, the
method 200 start after other steps in forming a magnetic memory
have been performed. The method 200 is described in the context of
the magnetic junction 100, 100' and 100''. However the method 200
may be used in forming other magnetic junction(s) and the free
layers 120, 120' and/or 120''. Further, multiple magnetic junctions
may be simultaneously fabricated.
[0053] Seed layer(s) 102 are provided on the substrate, via step
202. Step 202 may include depositing the appropriate seed layer(s)
for the pinned layer 104 or for the free layer 108. If the magnetic
junction 100 or 100' is being fabricated, then the seed layer(s)
for the pinned layer 104 are provided in step 202. If the magnetic
junction 100'' is being fabricated, then the seed layer(s) 102' for
the free layer 108/108' are provided in step 202. Thus, step 202
may include providing one or more of magnesium oxide, tantalum
oxide, molybdenum oxide and vanadium oxide.
[0054] A pinned layer 104 may be provided, via step 204. Step 204
is performed if the entire dual magnetic junction 100 is to be
formed or if a bottom pinned magnetic junction 100' that omits the
layers 110 and 112 is to be formed. Step 204 may include providing
a multilayer structure having a high perpendicular magnetic
anisotropy. Thus, the pinned layer 104 formed in step 204 may be a
simple (single) layer or may include multiple layers. For example,
the pinned layer formed in step 204 may be a synthetic
antiferromagnet including magnetic layers antiferromagnetically or
ferromagnetically coupled through thin nonmagnetic layer(s), such
as Ru. Each magnetic layer may also include multiple layers.
[0055] A nonmagnetic spacer layer 106 may be provided, via step
206. Step 206 is performed if the dual magnetic junction 100 or a
bottom pinned magnetic junction 100' is to be formed. In some
embodiments, a crystalline MgO tunneling barrier layer may be
desired for the magnetic junction being formed. Step 206 may
include depositing MgO using, for example, radio frequency (RF)
sputtering. In other embodiments, metallic Mg may be deposited and
then oxidized in step 206 to provide a natural oxide of Mg. The MgO
barrier layer/nonmagnetic spacer layer 106 may also be formed in
another manner. Step 206 may include annealing the portion of the
magnetic junction already formed to provide crystalline MgO
tunneling barrier with a (100) orientation for enhanced TMR of the
magnetic junction. Because the nonmagnetic spacer layer 106 may
also be viewed as a seed layer for the free layer 108/108', step
206 may also be seen as forming seed layer(s) 131, 131' and/or
131''.
[0056] A free layer 108/108' is provided, via step 208. Step 208
includes depositing the material(s) for the free layer 108. If
steps 204 and 206 are omitted, then the free layer may be deposited
on seed layer(s) in step 208. In such embodiments, a top pinned
magnetic junction is fabricated. The seed layer(s) may be selected
for various purposes including but not limited to the desired
crystal structure of the free layer 108/108', magnetic anisotropy
and/or magnetic damping of the free layer 108/108'. For example,
the free layer 108' may be provided on seed layer(s) 102' such as a
crystalline MgO layer that promotes a perpendicular magnetic
anisotropy in the free layer 108/108'. If a dual magnetic junction
or bottom pinned magnetic junction is fabricated, the free layer
may be formed on a nonmagnetic spacer layer provided in step 208.
Step 208 may also be viewed as providing the free layer 120, 120'
or 120''. Thus, step 208 may include depositing one or more layers
including a [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t alloy layer.
Thus, the layer 122, 122' and/or 122'' may be deposited. Multiple
[Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t alloy layers may also be
formed. A CoFeB layer and/or a FeB layer may also be provided. Step
208 may also include cooling the layers that have been provided
before depositing the free layer materials. For example, the
portion of the magnetic junction 100 that has been deposited may be
cooled after step 206 and during step 208. Such a cooling step may
include placing the portion of the magnetic junction 100 that has
been deposited in a cooling chamber having a temperature less than
room temperature (approximately twenty-three degrees Celsius). In
some embodiments, the cooling chamber has a temperature of at least
eighty Kelvin and not more than three hundred Kelvin.
[0057] An additional nonmagnetic spacer layer 110 may be provided,
via step 210. Step 210 is performed if a dual magnetic junction 100
or a top pinned magnetic junction 100'' is desired to be
fabricated. If a bottom pinned magnetic junction is desired, then
step 210 is omitted. In some embodiments, an additional crystalline
MgO tunneling barrier layer may be desired for the magnetic
junction being formed. Step 210 may thus be performed as described
above with respect to step 206. For a dual magnetic junction, the
nonmagnetic spacer layer 110 may be considered to be the main
tunneling barrier layer. Thus, the thickness and crystallinity of
the layer 110 may be optimized in step 210.
[0058] An additional pinned 112 layer may optionally be provided,
via step 212. Step 212 may be performed if the dual magnetic
junction 100 or top pinned magnetic junction 100'' is desired to be
fabricated. If a bottom pinned magnetic junction 100' is desired,
then step 212 is omitted. The pinned layer 112 formed in step 210
may be a simple (single) layer or may include multiple layers. For
example, the pinned layer formed in step 210 may be a SAF.
[0059] The capping layer(s) 114 may then be provided, via step 214.
If the bottom pinned magnetic junction 100'' is being formed, then
step 214 may include providing at least one of a magnesium oxide
layer, a tantalum oxide layer, a molybdenum oxide layer and a
vanadium oxide layer. Step 214 may thus be seen as providing the
capping layer 132, 132' or 132'' in some embodiments.
[0060] Fabrication of the magnetic junction 100 may then be
completed. For example, the edges of the magnetic junction 100 may
be defined. This may be accomplished by providing a mask on the
layers that have been deposited and ion milling the exposed
portions of the layers. In some embodiments, an ion mill may be
performed. Thus, the edges of the magnetic junction 100 may be
defined after steps 202 through 210 are performed. Alternatively,
the edges of various layers may be formed at other times.
Additional structures, such as contacts and conductive lines may
also be formed for the device in which the magnetic junction is
used.
[0061] Using the method 200, the magnetic junction 100, the
magnetic junction 100' and/or the magnetic junction 100'' may be
formed. The free layers 108, 108', 120, 120' and/or 120'' may be
fabricated. As a result, a magnetic junction having free layer(s)
with improved switching characteristics may be achieved.
[0062] FIG. 8 is a flow chart depicting an exemplary embodiment of
a method 210 for providing a free layer for magnetic junction
usable in a magnetic device. The method 210 may be used to from the
free layer 120, 120' and/or 120''. For simplicity, some steps may
be omitted, performed in another order, include substeps and/or
combined. Further, the method 210 start after other steps in
forming a magnetic memory have been performed. The method 210 is
described in the context of the free layers 120, 120' and 120''.
However the method 210 may be used in forming other free layer(s).
Further, multiple free layers may be simultaneously fabricated.
[0063] A seed layer 131/131'/131'' that adjoins, or shares an
interface with, the free layer 120 is provided, via step 222. In
some embodiments, step 222 includes depositing at least one of
magnesium oxide, tantalum oxide layer, molybdenum oxide and
vanadium oxide. In some embodiments, the seed layer provided in
step 222 may form a nonmagnetic spacer layer of the magnetic
junction being formed.
[0064] The seed layer may be cooled to below room temperature, via
step 224. Step 224 is optional and might be skipped in some
embodiments. When performed, step 224 is completed before
deposition of the materials that will form the free layer.
[0065] A CoFeB or FeB layer 124 or 124' may be provided, via step
226. Step 226 may be skipped if the free layer 120' is being
formed. The [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t alloy layer
122/122'/122'' is provided, via step 226. A CoFeB or FeB layer 126
may be provided, via step 230. Step 230 may be skipped if the free
layer 120'' is being formed. Together, steps 226, 228 and 230 may
be viewed as providing at least one of the free layers 120, 120'
and 120''.
[0066] A capping layer 132, 132' or 132'' is provided, via step
232. Step 232 may include providing at least one of a magnesium
oxide layer, a tantalum oxide layer, a molybdenum oxide layer and a
vanadium oxide layer. Fabrication of the free layer 120, 120' or
120'' may then be completed, via step 234. For example, the edges
of the free layer 120, 120' or 120'' may be defined.
[0067] Using the method 210, the free layers 108, 108', 120, 120'
and/or 120'' may be fabricated. As a result, a magnetic junction
having free layer(s) with improved switching characteristics may be
achieved.
[0068] FIG. 9 depicts an exemplary embodiment of a memory 300 that
may use one or more of the magnetic junctions 100, 100' and/or
100'' and/or other magnetic junction including a CoFeBMo free layer
such as the free layer 120, 120' and/or 120''. The magnetic memory
300 includes reading/writing column select drivers 302 and 306 as
well as word line select driver 304. Note that other and/or
different components may be provided. The storage region of the
memory 300 includes magnetic storage cells 310. Each magnetic
storage cell includes at least one magnetic junction 312 and at
least one selection device 314. In some embodiments, the selection
device 314 is a transistor. The magnetic junctions 312 may be one
of the 100, 100', 100'' and/or other magnetic junction including
the [Co.sub.xFe.sub.yB.sub.z].sub.uMo.sub.t alloy layer within the
free layer. Although one magnetic junction 312 is shown per cell
310, in other embodiments, another number of magnetic junctions 312
may be provided per cell. As such, the magnetic memory 300 may
enjoy the benefits described above.
[0069] A method and system for providing a magnetic junction and a
memory fabricated using the magnetic junction has been described.
The method and system have been described in accordance with the
exemplary embodiments shown, and one of ordinary skill in the art
will readily recognize that there could be variations to the
embodiments, and any variations would be within the spirit and
scope of the method and system. Accordingly, many modifications may
be made by one of ordinary skill in the art without departing from
the spirit and scope of the appended claims.
* * * * *