U.S. patent application number 11/517559 was filed with the patent office on 2007-03-15 for magnetic switching element and signal processing device using the same.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Shigeru Haneda, Takahiro Hirai, Hirofumi Morise, Yuichi Motoi, Shiho Nakamura.
Application Number | 20070057278 11/517559 |
Document ID | / |
Family ID | 37854196 |
Filed Date | 2007-03-15 |
United States Patent
Application |
20070057278 |
Kind Code |
A1 |
Nakamura; Shiho ; et
al. |
March 15, 2007 |
Magnetic switching element and signal processing device using the
same
Abstract
A magnetic switching element according to an example of the
present invention includes a magnetic element, first and second
electrodes which put the magnetic element therebetween, a current
control section which is connected to the first and second
electrodes, the current control section controlling a magnetization
direction of a magnetization free section in such a manner that a
current is made to flow between the magnetization free section and
the magnetization fixed section, a movable conductive tube having a
fixed end and a free end, and a third electrode connected to the
fixed end of the conductive tube. A switching operation is
performed in such a manner that a spatial position of the
conductive tube is caused to change depending on the magnetization
direction of the magnetization free section.
Inventors: |
Nakamura; Shiho;
(Fujisawa-shi, JP) ; Motoi; Yuichi; (Yokohama-shi,
JP) ; Haneda; Shigeru; (Yokohama-shi, JP) ;
Morise; Hirofumi; (Yokohama-shi, JP) ; Hirai;
Takahiro; (Yokohama-shi, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
|
Family ID: |
37854196 |
Appl. No.: |
11/517559 |
Filed: |
September 8, 2006 |
Current U.S.
Class: |
257/107 |
Current CPC
Class: |
G11C 13/025 20130101;
G11C 2213/71 20130101; G11C 11/16 20130101; B82Y 10/00 20130101;
Y10S 977/725 20130101; Y10S 977/943 20130101; G11C 23/00 20130101;
H01H 1/0094 20130101 |
Class at
Publication: |
257/107 |
International
Class: |
H01L 29/74 20060101
H01L029/74 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 9, 2005 |
JP |
2005-262579 |
Claims
1. A magnetic switching element comprising: a magnetic element
which has a magnetization fixed section whose magnetization
direction is fixed, a magnetization free section whose
magnetization direction changes due to spin-polarized electrons,
and a non-magnetic intermediate layer between the magnetization
fixed section and the magnetization free section; first and second
electrodes which puts the magnetic element therebetween; a current
control section which is connected to the first and second
electrodes, the current control section controlling the
magnetization direction of the magnetization free section in such a
manner that a current is made to flow between the magnetization
fixed section and the magnetization free section; a movable
conductive tube having a fixed end and a free end; a magnetic fine
particle provided at the conductive tube; and a third electrode
connected to the fixed end of the conductive tube.
2. The magnetic switching element according to claim 1, wherein a
state that the magnetic fine particle comes into contact with the
first electrode, the second electrode or the magnetic element is
defined as an ON state, while a state that the magnetic fine
particle is separated from the first electrode, the second
electrode or the magnetic element is defined as an OFF state.
3. The magnetic switching element according to claim 1, further
comprising a fourth electrode independent of the first, second and
third electrodes, wherein a state that the magnetic particles come
into contact with the fourth electrode is defined as an ON state,
while a state that the magnetic fine particle is separated from the
fourth electrode is defined as an OFF state.
4. The magnetic switching element according to claim 1, further
comprising a dummy electrode arranged at a position opposite to the
third electrode.
5. The magnetic switching element according to claim 1, wherein the
magnetic fine particle is arranged at the free end of the
conductive tube.
6. The magnetic switching element according to claim 1, wherein the
magnetization of the magnetic element is in an anti-parallel state
in a state that the current does not flow, while the magnetization
of the magnetic element is in a parallel state in a state that the
current flows.
7. The magnetic switching element according to claim 1, wherein the
magnetization of the magnetic element is in a parallel state in a
state that the current does not flow, while the magnetization of
the magnetic element is in an anti-parallel state in a state that
the current flows.
8. The magnetic switching element according to claim 1, wherein
when the current flows in a first direction, the magnetic element
remains in a parallel state even though the current is cut off
thereafter, while when current flows in a second direction, the
magnetic element remains in an anti-parallel state even though the
current is cut off thereafter.
9. The magnetic switching element according to claim 1, wherein the
magnetization fixed section has an SAF structure, and the
magnetization of the magnetization free section is in a heat
fluctuation state in a state that the current does not flow, while
the magnetization of the magnetization free section heads toward
one direction in a state that the current flows.
10. The magnetic switching element according to claim 1, wherein
the magnetization fixed section has an SAF structure, and the
magnetization of the magnetization free section heads toward one
direction in a state that the current flows in a first direction,
while the magnetization of the magnetization free section heads
toward another direction opposite to the one direction in a state
that the current flows in a second direction.
11. The magnetic switching element according to claim 1, wherein
the magnetic switching element is in an OFF state in a state that
the current does not flow.
12. The magnetic switching element according to claim 1, wherein
the magnetic switching element is in an ON state in a state that
the current does not flow.
13. The magnetic switching element according to claim 1, wherein
the magnetic switching element is in an OFF state in a state that
the current flows in a first direction, while the magnetic
switching element is in an ON state in a state that the current
flows in a second direction.
14. The magnetic switching element according to claim 1, wherein
the non-magnetic intermediate layer is composed of a non-magnetic
conductive layer.
15. The magnetic switching element according to claim 1, wherein
the conductive tube is arranged within a cavity covered with an
insulating layer.
16. A signal processing device comprising: switch units each
comprising the magnetic switching element according to claim 1,
wherein a logic circuit is composed of combination of the switch
units.
17. The signal processing device according to claim 16, wherein the
switch units are stacked on a semiconductor substrate.
18. A magnetic switching element comprising: a magnetic element
which has a magnetization fixed section whose magnetization
direction is fixed, a magnetization free section whose
magnetization direction changes due to spin-polarized electrons,
and a non-magnetic intermediate layer between the magnetization
fixed section and the magnetization free section; first and second
electrodes which put the magnetic element therebetween; a current
control section which is connected to the first and second
electrodes, the current control section controlling the
magnetization direction of the magnetization free section in such a
manner that a current is made to flow between the magnetization
fixed section and the magnetization free section; a movable
conductive tube having a fixed end and a free end; a third
electrode connected to the fixed end of the conductive tube; a
magnetic fine particle provided at the conductive tube; and a
supporting stand which supports the free end of the conductive
tube.
19. The magnetic switching element according to claim 18, wherein a
state that the magnetic fine particle comes into contact with the
first electrode, the second electrode or the magnetic element is
defined as an ON state, while a state that the magnetic fine
particle is separated from the first electrode, the second
electrode or the magnetic element is defined as an OFF state.
20. The magnetic switching element according to claim 18, further
comprising a fourth electrode independent of the first, second and
third electrodes, wherein a state that the magnetic particles come
into contact with the fourth electrode is defined as an ON state,
while a state that the magnetic fine particle is separated from the
fourth electrode is defined as an OFF state.
21. The magnetic switching element according to claim 18, wherein
the magnetic fine particle is included in the conductive tube.
22. The magnetic switching element according to claim 18, wherein
the magnetization of the magnetic element is in an anti-parallel
state in a state that the current does not flow, while the
magnetization of the magnetic element is in a parallel state in a
state that the current flows.
23. The magnetic switching element according to claim 18, wherein
the magnetization of the magnetic element is in a parallel state in
a state that the current does not flow, while the magnetization of
the magnetic element is in an anti-parallel state in a state that
the current flows.
24. The magnetic switching element according to claim 18, wherein,
when the current flows in a first direction, the magnetic element
remains in a parallel state even though the current is cut off
thereafter, while when current flows in a second direction, the
magnetic element remains in an anti-parallel state even though the
current is cut off thereafter.
25. The magnetic switching element according to claim 18, wherein
the magnetization fixed section has an SAF structure, and the
magnetization of the magnetization free section is in a heat
fluctuation state in a state that the current does not flow, while
the magnetization of the magnetization free section heads toward
one direction in a state that the current flows.
26. The magnetic switching element according to claim 18, wherein
the magnetization fixed section has an SAF structure, and the
magnetization of the magnetization free section heads toward one
direction in a state that the current flows in a first direction,
while the magnetization of the magnetization free section heads
toward another direction opposite to the one direction in a state
that the current flows in a second direction.
27. The magnetic switching element according to claim 18, wherein
the magnetic switching element is in an OFF state in a state that
the current does not flow.
28. The magnetic switching element according to claim 18, wherein
the magnetic switching element is in an ON state in a state that
the current does not flow.
29. The magnetic switching element according to claim 18, wherein
the magnetic switching element is in an OFF state in a state that
the current flows in a first direction, while the magnetic
switching element is in an ON state in a state that the current
flows in a second direction.
30. The magnetic switching element according to claim 18, wherein
the non-magnetic intermediate layer is composed of a non-magnetic
conductive layer.
31. The magnetic switching element according to claim 18, wherein
the conductive tube is arranged within a cavity covered with an
insulating layer.
32. A signal processing device comprising: switch units each
comprising the magnetic switching element according to claim 18,
wherein a logic circuit is composed of combination of the switch
units.
33. The signal processing device according to claim 32, wherein the
switch units are stacked on a semiconductor substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2005-262579,
filed Sep. 9, 2005, the entire contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a switching element which
uses a magnetic force.
[0004] 2. Description of the Related Art
[0005] A switching element using a semiconductor represented by a
MOSFET or a diode can be ultra-miniaturized and integrated, and
therefore, such a switching element becomes one of indispensable
devices in various existing electronic devices.
[0006] Meanwhile, development advances concerning microscopic
machine such as a micro-machine or a nano-machine due to an
improvement of a nano-technology of late. For example, in a medical
field, a nano-machine will be materialized in the not-too-distant
future.
[0007] By the way, a drive source of such a microscopic machine is
a battery or radio wave. For this reason, energy loss is fatal for
the micro machine.
[0008] Accordingly, accomplishment of power saving is desired with
respect to the whole element in relation to the micro machine.
[0009] However, as for the switching element such as the MOSFET or
diode, an ON/OFF resistance ratio is small and ON resistance is
large, and thus, it is disadvantageous for accomplishment of power
saving. For this reason, in the case where the switching element is
applied to the microscopic machine, the problem that the battery
life is dead soon takes place (for example, JP-A 2004-221442
(KOKAI), Appl. Phys. Lett. 86 023109 (2005), Appl. Phys. A69,
305-308 (1999), Jpn. J. Appl. Phys. 42, 2416 (2003)).
BRIEF SUMMARY OF THE INVENTION
[0010] A magnetic switching element according to an aspect of the
present invention comprises, a magnetic element composed of a
magnetization fixed section whose magnetization direction is fixed,
a magnetization free section whose magnetization direction changes
due to spin-polarized electrons, and a non-magnetic intermediate
layer between the magnetization fixed section and the magnetization
free section, first and second electrodes which puts the magnetic
element therebetween, a current control section which is connected
to the first and second electrodes, the current control section
controlling the magnetization direction of the magnetization free
section in such a manner that a current is made to flow between the
magnetization fixed section and the magnetization free section, a
movable conductive tube having a fixed end and a free end, a
magnetic fine particle provided at the conductive tube, and a third
electrode connected to the fixed end of the conductive tube.
[0011] A magnetic switching element according to another aspect of
the present invention comprises, a magnetic element composed of a
magnetization fixed section whose magnetization direction is fixed,
a magnetization free section whose magnetization direction changes
due to spin-polarized electrons, and a non-magnetic intermediate
layer between the magnetization fixed section and the magnetization
free section, first and second electrodes which put the magnetic
element therebetween, a current control section which is connected
to the first and second electrodes, the current control section
controlling the magnetization direction of the magnetization free
section in such a manner that a current is made to flow between the
magnetization fixed section and the magnetization free section, a
movable conductive tube having a fixed end and a free end, a third
electrode connected to the fixed end of the conductive tube, a
magnetic fine particle provided at the conductive tube, and a
supporting stand which supports the free end of the conductive
tube.
[0012] A signal processing device according to still another aspect
of the present invention comprises switch units each comprising the
magnetic switching element according to the aspect of the
invention. A logic circuit is composed of combination of the switch
units.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0013] FIG. 1 is a plan view of a magnetic switching element
according to a first embodiment;
[0014] FIG. 2 is a cross sectional view taken along a line II-II of
FIG. 1;
[0015] FIG. 3 is a cross sectional view showing a first modified
example of the first embodiment;
[0016] FIG. 4 is a plan view showing a second modified example of
the first embodiment;
[0017] FIG. 5 is a cross sectional view taken along a line V-V of
FIG. 4;
[0018] FIG. 6 is a plan view of a magnetic switching element
according to a second embodiment;
[0019] FIG. 7 is a cross sectional view taken along a line VII-VII
of FIG. 6;
[0020] FIG. 8 is a cross sectional view showing a first modified
example of the second embodiment;
[0021] FIG. 9 is a plan view showing a second modified example of
the second embodiment;
[0022] FIG. 10 is a cross sectional view taken along a line X-X of
FIG. 9;
[0023] FIG. 11 is a plan view of a magnetic switching element
according to a third embodiment;
[0024] FIG. 12 is a cross sectional view taken along a line XII-XII
of FIG. 11;
[0025] FIG. 13 is a cross sectional view showing a first modified
example of the third embodiment;
[0026] FIG. 14 is a cross sectional view showing a second modified
example of the third embodiment;
[0027] FIG. 15 is a plan view of a magnetic switching element
according to a fourth embodiment;
[0028] FIG. 16 is a cross sectional view taken along a line XVI-XVI
of FIG. 15;
[0029] FIG. 17 is a plan view of a magnetic switching element
according to a fifth embodiment;
[0030] FIG. 18 is a plan view of a magnetic switching element
according to a sixth embodiment;
[0031] FIG. 19 is a cross sectional view taken along a line XIX-XIX
of FIG. 18;
[0032] FIG. 20 is a plan view of a magnetic switching element
according to a seventh embodiment;
[0033] FIG. 21 is a cross sectional view taken along a line XXI-XXI
of FIG. 20;
[0034] FIG. 22 is a cross sectional view showing one process of a
manufacturing method according to an example of the present
invention;
[0035] FIG. 23 is a cross sectional view showing one process of a
manufacturing method according to an example of the present
invention;
[0036] FIG. 24 is a cross sectional view showing one process of a
manufacturing method according to an example of the present
invention;
[0037] FIG. 25 is a cross sectional view showing one process of a
manufacturing method according to an example of the present
invention;
[0038] FIG. 26 is a view showing CASE A of switching principles
according to an example of present invention;
[0039] FIG. 27 is a view showing magnetic field lines generated
from a magnetic element in an anti-parallel state;
[0040] FIG. 28 is a view showing magnetic field lines generated
from a magnetic element in a parallel state;
[0041] FIG. 29 is a graph showing a relationship between a
resistance value and a current that flows through the magnetic
element of CASE A;
[0042] FIG. 30 is a view showing CASE B of the switching principles
according to an example of the present invention;
[0043] FIG. 31 is a view showing a relationship between a
resistance value and a current that flows through the magnetic
element of CASE B;
[0044] FIG. 32 is a view showing CASE C of the switching principles
according to an example of the present invention;
[0045] FIG. 33 is a view showing a relationship between a
resistance value and a current that flows through the magnetic
element of CASE C;
[0046] FIG. 34 is a view showing CASE D of the switching principles
according to an example of the present invention;
[0047] FIG. 35 is a view showing CASE E of the switching principles
according to an example of the present invention;
[0048] FIG. 36 is a circuit diagram showing an inverter circuit
using a magnetic switching element;
[0049] FIG. 37 is a waveform diagram showing an input/output
waveform of the inverter circuit of FIG. 36;
[0050] FIG. 38 is a view showing a state at the time of ON of the
inverter circuit of FIG. 36;
[0051] FIG. 39 is a view showing a state at the time of OFF of the
inverter circuit of FIG. 36;
[0052] FIG. 40 is a circuit diagram showing an AND gate circuit
using a magnetic switching element;
[0053] FIG. 41 is a waveform diagram showing an input/output
waveform of the AND gate circuit of FIG. 40;
[0054] FIG. 42 is a circuit diagram showing an OR gate circuit
using a magnetic switching element;
[0055] FIG. 43 is a waveform diagram showing an input/output
waveform of the OR gate circuit of FIG. 42;
[0056] FIG. 44 is a circuit diagram showing an example of a signal
processing device using a magnetic switching element;
[0057] FIG. 45 is a circuit diagram showing an example of a signal
processing device using a magnetic switching element;
[0058] FIG. 46 is a view showing a semiconductor memory to which an
example of the present invention is applied;
[0059] FIG. 47 is a view showing an image of 3D-chip to which an
example of the present invention is applied; and
[0060] FIG. 48 is a view showing a structure image of FPGA.
DETAILED DESCRIPTION OF THE INVENTION
[0061] A mangetoresistive element of an aspect of the present
invention will be described below in detail with reference to the
accompanying drawings.
[0062] 1. Outline
[0063] In an example of the present invention, a switching element
such as MOSFET for controlling ON/OFF operation electrically is not
proposed, but a mechanical switching element for controlling ON/OFF
operation mechanically is proposed.
[0064] A conductive tube, such as carbon nanotube, having
sufficient intensity and elastic force is utilized as a moving
element. Then, a switching operation is performed in such a manner
that a magnetic fine particle is arranged at a tip end of the
conductive tube and a physical position of the magnetic fine
particle is controlled by a magnetic force.
[0065] A magnetic field which is basis of the magnetic force is
generated by the magnetic element. The magnetic element contains a
magnetization fixed section whose magnetization direction is fixed
and a magnetization free section whose magnetization direction is
changed. A magnetic field is controlled depending on the
magnetization direction of the magnetization free section.
[0066] The magnetization direction of the magnetization free
section is changed in such a manner that spin-polarized electrons
are made to flow into the magnetic element. That is, switching can
be controlled by controlling a spin-polarized current (or
electrons) in a current control section.
[0067] Such switching elements are referred to as magnetic
switching elements.
[0068] The magnetic switching element can be formed on a
semiconductor substrate by using, for example, a semiconductor
process. For this reason, it is possible to combine a semiconductor
integrated circuit such as a CMOS logic circuit or a memory circuit
with the magnetic switching element.
[0069] Further, if constituting a switch unit with the magnetic
switching element, it is possible to form a signal processing
device serving as a logic circuit by combining a plurality of
switch units. Further, a 3D (dimension)-chip can be also formed
while accumulating a plurality of switch units on the semiconductor
substrate.
[0070] 2. Embodiment
[0071] Now, embodiments of the invention will be described.
[0072] (1) First Embodiment
[0073] A first embodiment relates to a magnetic switching element
in a state that a channel of an input signal IN and a channel of an
output signal OUT are overlapped with each other, the input signal
IN and output signal OUT cause the switch to operate ON/OFF.
[0074] A. Basic Structure
[0075] FIG. 1 is a plan view of the magnetic switching element
according to the first embodiment. FIG. 2 is a cross sectional view
taken along a line II-II of FIG. 1.
[0076] A magnetic field generation section 11 is composed of first
and second electrodes 11a, 11b and a magnetic element arranged
between the electrodes. The magnetic element is composed of
magnetic layers 11b, 11d and a non-magnetic layer 11c arranged
between the magnetic layers.
[0077] One of the two magnetic layers 11b, 11d functions as a
magnetization fixed section whose magnetization direction is fixed,
while the other thereof functions as a magnetization free section
whose magnetization direction is changed due to spin-polarized
electrons.
[0078] It is preferable that the non-magnetic layer 11c serving as
an intermediate layer is a non-magnetic conductive layer. However,
for example, the non-magnetic layer 11c may be a non-magnetic
insulating layer functioning as a tunnel barrier layer.
[0079] A current control section 12 is connected to the first and
second electrodes 11a, 11e, and controls the magnetization
direction of the magnetization free section in such a manner that a
spin injection current is made to flow between the magnetic layers
11b, 11d, for example, based on the input signal IN.
[0080] A conductive tube 14 is constituted of, for example, a
carbon nanotube, and functions as a moving element. The conductive
tube 14 has a fixed end and a free end. A third electrode 13 is
connected to the fixed end of the conductive tube 14, and a lead
layer 16 is connected to the third electrode 13. Further, a
magnetic fine particle 15 is arranged at the free end of the
conductive tube 14.
[0081] Here, the conductive tube 14 is illustrated as being of one.
However, a plurality of conductive tubes 14 may extend toward the
upper part of the magnetic field generation section 11 from the
third electrode 13.
[0082] The magnetic field generation section 11, the third
electrode 13 and the lead layer 16 are buried in an insulating
layer 17. On the insulating layer 17, insulating layers 19, 20
surrounding the conductive tube 14 are provided. As a result, a
cavity 18 is formed, and the conductive tube 14 is arranged in the
cavity 18.
[0083] The magnetic switching element (switch unit) is constituted
by the above elements.
[0084] B. Modified Example
[0085] FIG. 3 shows a first modified example of the first
embodiment.
[0086] A plan view is the same as FIG. 1. The modified example is
characterized in that an upper surface of the third electrode 13 is
upper than an upper surface of the second electrode 11e.
[0087] In this modified example, the third electrode 13 has a shape
projected from the insulating layer 17.
[0088] Provided that above-described condition is satisfied, part
or the whole of a side wall of the third electrode 13 of part
projected from the insulating layer 17 may be covered with an
insulating layer.
[0089] With the configuration described above, growth of the
conductive tube 14 becomes easy, so that reliability of a device is
improved.
[0090] FIG. 4 shows a second modified example of the first
embodiment. FIG. 5 is a cross sectional view taken along a line V-V
of FIG. 4.
[0091] A characteristic of the modified example resides in
structure of the magnetic field generation section 11. The
respective layers 11a to 11e constituting the magnetic field
generation section 11 are stacked in not a vertical direction (up
and down direction), but a lateral direction (right and left
direction).
[0092] Here, a lead layer 21 is connected to the first electrode
11a, and a lead layer 22 is connected to the second electrode 11e.
However, the lead layer 21 may be integrated with the first
electrode 11a, and also the lead layer 22 may be integrated with
the second electrode 11e.
[0093] In addition, the respective layers 11a to 11e constituting
the magnetic field generation section 11 may be stacked in an
oblique direction, neither in the vertical direction nor in the
lateral direction.
[0094] In other words, the respective layers 11a to 11e may be
stacked in any direction as long as the spin injection current
crosses interfaces of the respective layers 11a to 11e.
[0095] C. Basic Operation
[0096] A basic operation is performed in such a manner that the
spin-polarized electrons are made to flow into the magnetic element
to thereby control a composite magnetic field composed of a
magnetic field generated from the magnetization fixed section and a
magnetic field generated from the magnetization free section.
Specifically, a spatial position of the magnetic fine particle 15
is changed in accordance with the magnetization direction of the
magnetization free section in order to perform ON/OFF operation of
the amount of current flowing between the third electrode 13 and
the first or second electrode 11a, 11e.
[0097] For example, when the magnetization directions of the
magnetic layers 11b, 11d are in a parallel state (the same
direction), the composite magnetic field is generated, and then,
the magnetic fine particle 15 moves by the magnetic force. On the
other hand, when the magnetization direction of the magnetic layers
11b, 11d is in an anti-parallel direction (opposite directions),
the composite magnetic field disappears, and the magnetic fine
particle 15 returns to the initial position by the elastic force of
the conductive tube 14.
[0098] In the case where the magnetic fine particle 15 is separated
from the first or second electrode 11a, 11e in an initial state
that the magnetic field is not generated, a normally-off-type
switching element is constituted, while in the case where the
magnetic fine particle 15 comes into contact with the first or
second electrode 11a, 11e in the initial state that the magnetic
field is not generated, a normally-on-type switching element is
constituted.
[0099] D. Layout
[0100] The Layout of the first electrode 11a, the second electrode
11e, the third electrode 13 and the lead layers 16, 21 and 22 is
not limited to the present embodiment. Their shapes, extending
directions and the like can be set freely in the condition not to
interfere with one another.
[0101] A planar shape of the magnetic element within the magnetic
field generation section 11 is also not limited to the present
embodiment. For example, the planar shape of the magnetic element
may adopt a square, a diamond shape, a circle, an oval and the like
in addition to a rectangle.
[0102] Further, the magnetic field generation section 11 can be
also set so as to become shapes such as a column and a square
pillar as a whole. Furthermore, the magnetic field generation
section 11 may become a shape in which an upper layer becomes
tapered-shape at the tip end compared with a lower layer as a
whole, in such a manner that planar shapes of the respective layers
11a to 11e constituting the magnetic field generation section 11
are formed with a dimension gradually decreasing as going from the
lower layer to the upper layer.
[0103] E. Size
[0104] An average size of the respective layers 11a to 11e
constituting the magnetic field generation section 11 is as
follows. That is, when its planar shape is made to be a four-sided
figure, each one side is preferably not more than 200 nm, and
further, most preferably not more than 100 nm.
[0105] This is because magnetization control of the magnetization
free layer due to the spin injection current becomes easy when the
size of the magnetic element is as small as possible.
[0106] Further, it is preferable that a diameter of the conductive
tube 14 is made not more than 100 nm, and preferably, the diameter
is made degree of several-tens nm.
[0107] The reason is as follows. That is, since a distance between
the magnetic field generation section 11 and the third electrode 13
is proportional to the diameter of the conductive tube 14, a size
of the switch unit becomes large when the diameter becomes large
excessively, so that miniaturization of the magnetic switching
element cannot be realized.
[0108] F. Others
[0109] As to the number of the conductive tube 14, it is preferable
that plural conductive tubes 14 are provided in order to decrease
ON resistance. In this case, the plural conductive tubes 14 may be
coupled physically with each other, or may be separated from each
other. As a matter of course, some of the plural conductive tubes
14 may be coupled, and the others may be separated.
[0110] A positional relationship between the magnetic fixed section
and the magnetic free section is that any section may be at its
upper side or lower side. Further, the magnetic layers 11b, 11d
constituting these sections may be an in-plane magnetization film
whose magnetization direction is in parallel to a film surface, or
may be a perpendicular magnetization film whose magnetization
direction is perpendicular to a film surface.
[0111] G. Conclusion
[0112] As described above, according to the first embodiment, the
ON/OFF operation of the switch is executed due to mechanical
contact/non-contact operation, and consequently, an ON/OFF
resistance ratio can be infinity. In addition, since the conductive
tube is constituted of a material having metallic characteristic, a
signal channel is in all metal, and thus it is possible to decrease
the ON resistance.
[0113] Furthermore, as will be described later, such a magnetic
switching element is formed by the semiconductor process.
Therefore, ultra miniaturization is possible, and thus, it is
possible to realize the switching element in nano-level.
[0114] (2) Second Embodiment
[0115] A second embodiment relates to a magnetic switching element
in which a channel of an input signal IN and a channel of an output
signal OUT are separated from each other, the signals causing a
switch to perform ON/OFF operation.
[0116] A. Basic Structure
[0117] FIG. 6 is a plan view of the magnetic switching element
according to the second embodiment. FIG. 7 is a cross sectional
view taken along a line VII-VII of FIG. 6.
[0118] A structure of a magnetic field generation section 11 is the
same as that of the first embodiment, and is composed of first and
second electrodes 11a, 11e, and a magnetic element arranged between
the electrodes. The magnetic element is composed of magnetic layers
11b, 11d, and a non-magnetic layer 11c arranged between the
magnetic layers.
[0119] In the present embodiment, the channel of the input signal
IN and the channel of the output signal OUT are separated from each
other. For this reason, the second electrode 11e of the magnetic
field generation section 11 is buried completely on the inside of
an insulating layer 17. Instead, a fourth electrode 23 which is
insulated from the first or second electrode 11a, 11e is arranged
on a surface area of the insulating layer 17.
[0120] A position of the fourth electrode 23 is set, for example,
between the magnetic field generation section 11 and the magnetic
fine particle 15. The fourth electrode 23 is connected to a
terminal A serving as one end of the switch.
[0121] A current control section 12 is connected to the first and
second electrodes 11a, 11e, and for example, based on the input
signal IN, controls the magnetization direction of the
magnetization free section in such a manner that a spin injection
current is made to flow between the magnetic layers 11b, 11d.
[0122] Like the first embodiment, a conductive tube 14 is
constituted by, for example, a carbon nanotube, and functions as a
moving element. A third electrode 13 is connected to a fixed end of
the conductive tube 14, and a lead layer 16 is connected to the
third electrode 13. The lead layer 16 is connected to a terminal B
serving as the other end of the switch.
[0123] The magnetic fine particle 15 is arranged at a free end of
the conductive tube 14.
[0124] Insulating layers 19, 20 surrounding the conductive tube 14
are provided on the insulating layer 17. As a result, a cavity 18
is formed, and then, the conductive tube 14 is arranged within the
cavity 18.
[0125] The magnetic switching element (switch unit) is constituted
by the above elements.
[0126] B. Modified Example
[0127] FIG. 8 shows the first modified example of the second
embodiment.
[0128] A plan view is the same as FIG. 6. The modified example is
characterized in that an upper surface of the third electrode 13 is
upper than an upper surface of the fourth electrode 23.
[0129] In this modified example, the third electrode 13 has a shape
projected from the insulating layer 17.
[0130] Provided that above-described condition is satisfied, part
or the whole of a side wall of the third electrode 13 of part
projected from the insulating layer 17 may be covered with an
insulating layer.
[0131] With the configuration described above, growth of the
conductive tube 14 becomes easy, so that reliability of a device is
improved.
[0132] FIG. 9 shows a second modified example of the second
embodiment. FIG. 10 is a cross sectional view taken along a line
X-X of FIG. 9.
[0133] A characteristic of the modified example resides in
structure of the magnetic field generation section 11. The
respective layers 11a to 11e constituting the magnetic field
generation section 11 are stacked in not a vertical direction (up
and down direction), but a lateral direction (right and left
direction).
[0134] Here, a lead layer 21 is connected to the first electrode
11a, and a lead layer 22 is connected to the second electrode 11e.
However, the lead layer 21 may be integrated with the first
electrode 11a, and also the lead layer 22 may be integrated with
the second electrode 11e.
[0135] In addition, the respective layers 11a to 11e constituting
the magnetic field generation section 11 may be stacked in an
oblique direction, neither in the vertical direction nor in the
lateral direction.
[0136] In other words, the respective layers 11a to 11e may be
stacked in any direction as long as the spin injection current
crosses interfaces of the respective layers 11a to 11e.
[0137] C. Basic Operation
[0138] Like the first embodiment, a basic operation is performed in
such a manner that the spin-polarized electrons are made to flow
into the magnetic element to thereby control a composite magnetic
field composed of a magnetic field generated from the magnetization
fixed section and a magnetic field generated from the magnetization
free section.
[0139] Specifically, a magnetization direction of the magnetization
free section within the magnetic field generation section 11 is
determined while causing the spin injection current to flow between
the first electrode 11a and the second electrode 11e. Then, a
spatial position of the magnetic fine particle 15 is changed in
accordance with the above magnetization direction, and
connection/disconnection operation between the third electrode
(terminal B) 13 and the fourth electrode (terminal A) 23 is
controlled.
[0140] For example, when the magnetization directions of the
magnetic layers 11b, 11d are in a parallel state (the same
direction), the composite magnetic field is generated, and then,
the magnetic fine particle 15 moves due to the magnetic force. On
the other hand, when the magnetization directions of the magnetic
layers 11b, 11d are in an anti-parallel state (opposite
directions), the composite magnetic field disappears, and the
magnetic fine particle 15 returns to the initial position due to
the elastic force of the conductive tube 14.
[0141] In the case where the magnetic fine particle 15 is separated
from the first or second electrode 11a, 11e in an initial state
that the magnetic field is not generated, a normally-off-type
switching element is constituted, while in the case where the
magnetic fine particle 15 comes into contact with the first or
second electrode 11a, 11e in the initial state that the magnetic
field is not generated, a normally-on-type switching element is
constituted.
[0142] D. Layout
[0143] The layout of the first electrode 11a, the second electrode
11e, the third electrode 13, the fourth electrode 23 and the lead
layers 16, 21 and 22 is not limited to the present embodiment.
Their shapes, extending directions and the like can be set freely
in the condition not to interfere with one another.
[0144] A planar shape of the magnetic element within the magnetic
field generation section 11 is also not limited to the present
embodiment. For example, the planar shape of the magnetic element
may adopt a square, a diamond shape, a circle, an oval and the like
in addition to a rectangle.
[0145] Further, the magnetic field generation section 11 can be
also set so as to become shapes such as a column and a square
pillar as a whole. Furthermore, the magnetic field generation
section 11 may become a shape in which an upper layer becomes
tapered-shape at the tip end compared with a lower layer as a
whole, where planar shapes of the respective layers 11a to 11e
constituting the magnetic field generation section 11 are formed
with a dimension gradually decreasing toward the upper layer from
the lower layer.
[0146] E. Size
[0147] An average size of the respective layers 11a to 11e
constituting the magnetic field generation section 11 is as
follows. That is, when its planar shape is made to be a four-sided
figure, each one side is preferably not more than 200 nm, and
further, most preferably not more than 100 nm.
[0148] This is because magnetization control of the magnetization
free layer due to the spin injection current becomes easy when the
size of the magnetic element is as small as possible.
[0149] Further, it is preferable that a diameter of the conductive
tube 14 is made not more than 100 nm, more preferably, the diameter
is made degree of several-tens nm.
[0150] The reason is as follows. Since a distance between the third
electrode 13 and the fourth electrode 23 is proportional to the
diameter of the conductive tube 14, a size of the switch unit
becomes large when the diameter becomes large excessively, so that
miniaturization of the magnetic switching element cannot be
realized.
[0151] F. Others
[0152] As to the number of the conductive tube 14, it is preferable
that plural conductive tubes are provided in order to decrease ON
resistance. In this case, plural conductive tubes 14 may be coupled
physically with each other, or may be separated from each other. As
a matter of course, some of the plural conductive tubes 14 may be
coupled, and the others may be separated.
[0153] A positional relationship between the magnetic fixed section
and the magnetic free section is that any section may be at its
upper side or lower side. Further, the magnetic layers 11b, 11d
constituting these sections may be an in-plane magnetization film
whose magnetization direction is in parallel to a film surface, or
may be a perpendicular magnetization film whose magnetization
direction is perpendicular to a film surface.
[0154] G. Conclusion
[0155] As described above, like the first embodiment, according to
the second embodiment, the ON/OFF operation of the switch is
executed due to the mechanical contact/non-contact operation. For
this reason, an ON/OFF resistance ratio can be infinity. Further,
since the conductive tube is constituted of a material having
metallic characteristic, a signal channel is in all metal, and thus
it is possible to decrease the ON resistance. Furthermore, such a
magnetic switching element is formed by the semiconductor process.
Therefore, ultra miniaturization is possible, and it is possible to
realize the switching element in nano-level.
[0156] (3) Third Embodiment
[0157] A third embodiment has a characteristic in the conductive
tube. In the first and the second embodiments, the conductive tube
is caused to grow from a flat surface substantially in parallel to
a surface beneath which the magnetic field generation section is
buried. However, in the third embodiment, the conductive tube is
formed substantially in parallel to a surface beneath which a
magnetic field generation section is buried.
[0158] A. Basic Structure
[0159] FIG. 11 is a plan view of a magnetic switching element
according to the third embodiment. FIG. 12 is a cross sectional
view taken along a line XII-XII of FIG. 11.
[0160] A structure of the magnetic field generation section 11 is
the same as that of the first embodiment. That is, the respective
layers constituting the magnetic field generation section 11 may be
stacked in the vertical direction as shown in FIGS. 1 and 2, or
alternatively, may be stacked in the lateral direction as shown in
FIGS. 4 and 5.
[0161] Like the first embodiment, the magnetic field generation
section 11 is buried within an insulating layer 17. However, in the
third embodiment, a third electrode 24 for obtaining an output
signal OUT is arranged on the insulating layer 17.
[0162] Further, in the third embodiment, a fifth electrode 25 is
newly arranged on the insulating layer 17 in such a manner as to
face to the third electrode 24.
[0163] The fifth electrode 25 is used to determine a growth
direction of the conductive tube when the conductive tube 14 is
formed. When applying a voltage between the third and the fifth
electrodes 24, 25, the conductive tube 14 grows linearly toward the
fifth electrode 25 from the third electrode 24. For this reason, in
the present embodiment, the conductive tube 14 extends in parallel
to the surface of the insulating layer 17.
[0164] Here, when the tip end of each of the third and fifth
electrodes 24, 25 is sharpened, an electric field is concentrated
between sharpened parts, and therefore, a direction control at the
time of growth of the conductive tube 14 becomes facilitated.
[0165] As a method of sharpening the tip ends of the third and
fifth electrodes 24, 25, for example, the third and fifth
electrodes 24, 25 are made to be tapered-shape at the tip end as a
planar shape, and are made to be overhang shape as a cross
sectional shape.
[0166] A current control section 12 controls the magnetizing
direction of the magnetizing free section within the magnetic field
generation section 11 due to supply of the spin injection current
to the magnetic element within the magnetic field generation
section 11 based on, for example, an input signal IN.
[0167] The conductive tube 14 is constituted of, for example, a
carbon nanotube, and functions as a moving element. The third
electrode 24 is connected to the fixed end of the conductive tube
14, and the output signal OUT is obtained from the third electrode
24. Further, a magnetic fine particle 15 is arranged at the free
end of the conductive tube 14.
[0168] Insulating layers 19, 20 surrounding the conductive tube 14
are provided on the insulating layer 17. As a result, a cavity 18
is formed, and the conductive tube 14 is arranged within the cavity
18.
[0169] The magnetic switching element (switch unit) is constituted
by the above elements.
[0170] B. Modified Example
[0171] FIG. 13 shows a first modified example of the third
embodiment.
[0172] A cross sectional view is the same as FIG. 12. The modified
example is characterized in that plural conductive tubes 14 extend
toward the fifth electrode 25 from the third electrode 24.
[0173] It is possible to reduce the ON resistance of the switching
element by forming plural conductive tube 14.
[0174] Here, when there is a difference in growing speed among
plural conductive tubes 14, some of them arrive at the fifth
electrode 25 and come into contact with the fifth electrode 25 in
some cases.
[0175] While supposing such a case, the fifth electrode 25 is made
to be in a floating state after growth of the conductive tube 14,
and when the fifth electrode 25 is used as the switching element,
the problem is not taken place on the operation.
[0176] Alternatively, instead of this, the voltage may be applied
between the third electrode 24 and the fifth electrode 25 after
growth of the conductive tube 14, so that the tube coming into
contact with the fifth electrode 25 may be disconnected
electrically. By doing this, the problem does not take place on the
switching operation even though the fifth electrode 25 is not in
the floating state.
[0177] FIG. 14 shows a second modified example of the third
embodiment.
[0178] A cross sectional view is the same as FIG. 12. Like the
first modified example of FIG. 13, the modified example is
characterized in that plural conductive tubes 14 extend toward the
fifth electrode 25 from the third electrode 24.
[0179] However, in the second modified example, there are provided
plural tapered portions at the tip ends of the third and fifth
electrodes 24, 25 such that the plural conductive tubes 14 are
surely formed.
[0180] As a consequence, it is possible to allow the plural
conductive tubes 14 to grow reliably, which is effective for
reduction of the ON resistance of the switching element.
[0181] Like the first modified example of FIG. 13, even though some
of the plural conductive tubes 14 arrive at the fifth electrode 25,
problems on the switch operation do not take place if the fifth
electrode 25 is made floating state after growth of the conductive
tube 14.
[0182] Alternatively, instead of this, the voltage is applied
between the third electrode 24 and the fifth electrode 25 after
growth of the conductive tube 14, the tube coming into contact with
the fifth electrode 25 may be disconnected electrically. By doing
this, the problem does not take place on the switching operation
even though the fifth electrode 25 is not in the floating
state.
[0183] C. Basic Operation
[0184] Since a basic operation is the same as the first embodiment,
its explanation will be omitted here.
[0185] D. Layout
[0186] The layout of the magnetic field generation section 11, the
third electrode 24 and the fifth electrode 25 is not limited to the
present embodiment. Their shapes, extending directions and the like
can be set freely in the condition not to interfere with one
another.
[0187] E. Size
[0188] A size of the magnetic field generation section 11 is as
follows. That is, like the first embodiment, when its planar shape
is made to be a four-sided figure, each one side is preferably not
more than 200 nm, and further, most preferably not more than 100
nm. Further, it is preferable that a diameter of the conductive
tube 14 is made not more than 100 nm, and more preferably, the
diameter is made degree of several-tens nm.
[0189] Preferably, a width w (refer to FIG. 12) from the third
electrode 24 to the fifth electrode 25 is set to a value within the
range from 100 nm to several .mu.m. Provided that the width w is
made to be equal to or larger in size than the magnetic field
generation section 11.
[0190] F. Others
[0191] In the first and second modified examples of the third
embodiment, some of the plural conductive tubes 14 may be
physically coupled with each other.
[0192] G. Conclusion
[0193] As described above, according to the third embodiment, the
ON/OFF resistance ratio can be infinity, and the ON resistance can
be decreased, like the first embodiment. Further, such a magnetic
switching element is formed by the semiconductor process.
Therefore, ultra miniaturization is possible, and thus, it is
possible to realize the switching element in nano-level.
[0194] (4) Fourth Embodiment
[0195] A fourth embodiment is obtained by combining the second
embodiment and the third embodiment. That is, a conductive tube is
formed linearly, and a channel of an input signal IN and a channel
of an output signal OUT are separated, the signals causing a switch
to perform ON/OFF operation.
[0196] A. Basic Structure
[0197] FIG. 15 is a plan view of a magnetic switching element
according to the fourth embodiment. FIG. 16 is a cross sectional
view taken along a line XVI-XVI of FIG. 15.
[0198] A structure of a magnetic field generation section 11 is the
same as that of the second embodiment. That is, the respective
layers constituting the magnetic field generation section 11 may be
stacked in the vertical direction as shown in FIGS. 6 and 7, or
alternatively, may be stacked in the lateral direction as shown in
FIGS. 9 and 10.
[0199] Like the second embodiment, the magnetic field generation
section 11 is buried in an insulating layer 17. However, in the
fourth embodiment, a third electrode 24 connected to a terminal B
serving as the other terminal of the switch is arranged on the
insulating layer 17.
[0200] Further, in the fourth embodiment, a fifth electrode 25 is
newly arranged on the insulating layer 17 so as to face to the
third electrode 24.
[0201] Furthermore, since the channel of the input signal IN and
the channel of the output signal OUT are separated, the magnetic
field generation section 11 is completely buried on the inside of
the insulating layer 17. Instead, in the surface region of the
insulating layer 17, the fourth electrode 23 is arranged which is
isolated respectively from the magnetic field generation section 11
and the fifth electrode 25.
[0202] A position of the fourth electrode 23 is set, for example,
between the magnetic field generation section 11 and the magnetic
fine particle 15. The fourth electrode 23 is connected to a
terminal A serving as one terminal of the switch.
[0203] A current control section 12 supplies a spin injection
current to the magnetic field generation section 11, for example,
based on the input signal IN, and controls the magnetization
direction of the magnetization free section in the magnetic field
generation section 11.
[0204] Like the second embodiment, a conductive tube 14 grows
linearly toward the fifth electrode 25 from the third electrode 24.
For this reason, in the present embodiment, the conductive tube 14
extends in parallel to the surface of the insulating layer 17.
[0205] Here, like the third embodiment, it is preferable that the
tip end of each of the third and fifth electrodes 24, 25 is
sharpened.
[0206] Insulating layers 19, 20 surrounding the conductive tube 14
are provided on the insulating layer 17. As a result, a cavity 18
is formed, and the conductive tube 14 is arranged in the cavity
18.
[0207] By the above elements, the magnetic switching element
(switch unit) is constituted.
[0208] B. Modified Example
[0209] Also in the fourth embodiment, the first and second modified
examples (refer to FIGS. 13 and 14) of the third embodiment can be
applied as they are.
[0210] C. Basic Operation
[0211] Since a basic operation is the same as that of the second
embodiment, its explanation will be omitted here.
[0212] D. Layout
[0213] The layout of the magnetic field generation section 11, the
third electrode 24, the fourth electrode 23 and the fifth electrode
25 is not limited to the present embodiment. Their shapes,
extending directions and the like can be set freely in the
condition not to interfere with one another.
[0214] E. Size
[0215] A size of the magnetic field generation section 11 is as
follows. That is, like the second embodiment, when its planar shape
is made to be a four-sided figure, each one side is preferably not
more than 200 nm, and further, most preferably not more than 100
nm. Further, it is preferable that a diameter of the conductive
tube 14 is made not more than 100 nm, and more preferably, the
diameter is made degree of several-tens nm.
[0216] It is preferable that a width w (refer to FIG. 12) from the
third electrode 24 to the fifth electrode 25 is set to a value
within the range from 100 nm to several .mu.m. Provided that the
width w is made to be equal to or larger in size than the magnetic
field generation section 11.
[0217] F. Others
[0218] In the case where the first and second modified examples of
the third embodiment are applied to the fourth embodiment, some of
the plural conductive tubes 14 may be physically coupled with each
other.
[0219] G. Conclusion
[0220] As described above, according to the forth embodiment, the
ON/OFF resistance ratio can be infinity, and the ON resistance can
be decreased, like the second embodiment. Further, such a magnetic
switching element is formed by the semiconductor process.
Therefore, ultra miniaturization is possible, and thus, it is
possible to realize the switching element in nano-level.
[0221] (5) Fifth Embodiment
[0222] A fifth embodiment has a characteristic in the number of
magnetic field generation sections. That is, one magnetic field
generation section is provided in the first to the fourth
embodiments, while in the fifth embodiment, motion of a conductive
tube is controlled by plural magnetic field generation
sections.
[0223] FIG. 17 is a plan view of a magnetic switching element
according to the fifth embodiment.
[0224] The magnetic switching element is the same as the magnetic
switching element of FIGS. 15 and 16 being the fourth embodiment
except for the number and the position of magnetic field generation
sections.
[0225] In the fifth embodiment, two magnetic field generation
sections 11a, 11b exist.
[0226] A structure of each of the magnetic field generation
sections 11a, 11b is the same as that of the second embodiment.
That is, the respective layers constituting the magnetic field
generation sections 11a, 11b may be stacked in the vertical
direction as shown in FIGS. 6 and 7, or alternatively, may be
stacked in the lateral direction as shown in FIGS. 9 and 10.
[0227] The magnetic field generation sections 11a, 11b are
arranged, for example, at a position where the conductive tube 14
is to be sandwiched. A third electrode (terminal B) 24 is connected
to the fixed end of the conductive tube 14, and a magnetic fine
particle 15 is arranged at the free end of the conductive tube
14.
[0228] A fifth electrode 25 is arranged at a position opposite to
the third electrode 24. The conductive tube 14 extends toward the
fifth electrode 25 from the third electrode 24.
[0229] A fourth electrode (terminal A) 23 is arranged directly
below the conductive tube 14. Motion of the conductive tube 14 is
controlled due to a magnetic field generated from the magnetic
field generation sections 11a, 11b, and the switch becomes ON-state
in such a manner that the magnetic fine particle 15 comes into
contact with the fourth electrode 23.
[0230] In the switching element of FIG. 17, the magnetic switching
element of FIGS. 15 and 16 being the fourth embodiment is
presupposed. However, it is possible to set the number of the
magnetic field generation sections to plural number in the magnetic
switching element according to the first to third embodiments.
[0231] (6) Sixth Embodiment
[0232] A sixth embodiment has a characteristic in the number of
magnetic fine particles. That is, in the first to the fourth
embodiments, the magnetic fine particle is arranged at the free end
of the conductive tube. However, in the sixth embodiment, plural
magnetic fine particles are arranged within the conductive
tube.
[0233] FIG. 18 is a plan view of a magnetic switching element
according to the sixth embodiment. FIG. 19 is a cross sectional
view taken along a line XIX-XIX of FIG. 18.
[0234] The magnetic switching element is the same as the magnetic
switching element of FIGS. 11 and 12 being the third embodiment
except for the structure of a conductive tube 14 and the number of
magnetic fine particles 15.
[0235] A structure of a magnetic field generation section 11 is the
same as that of the first embodiment. That is, the respective
layers constituting the magnetic field generation sections 11 may
be stacked in the vertical direction as shown in FIGS. 1 and 2, or
alternatively, may be stacked in the lateral direction as shown in
FIGS. 4 and 5.
[0236] The conductive tube 14 is arranged while lying over from a
third electrode 24 to a fifth electrode 25. One end of the
conductive tube 14 is fixed to the third electrode 24 to become a
fixed end. Further, the other end of the conductive tube 14 exists
on the fifth electrode 25 serving as a supporting stand. However,
the other end is not fixed to the fifth electrode 25 to become a
free end.
[0237] Plural magnetic fine particles 15 are arranged inside the
conductive tube 14. In order to realize such a structure, a carbon
nanotube with built-in fullerene is utilized, for example.
[0238] More specifically, a fullerene composed of, for example, C
(carbon).sub.60 or C.sub.70 has a spherical-shell-shaped structure.
For that reason, it is possible to realize the structure according
to the sixth embodiment if an endohedral compound that contains
magnetic fine particles in the spherical shell is built in the
carbon nanotube.
[0239] The switching operation is performed in such a manner that
the magnetic fine particles 15 within the conductive tube 14 are
attracted due to a magnetic force, and a center portion of the
conductive tube 14 is brought into contact with the magnetic field
generation section 11. Since the other end of the conductive tube
14 is only placed on the fifth electrode 25 as the free end, the
switching operation is performed smoothly.
[0240] Here, the nanotube with the fullerene or the fullerene
containing metals built-in is called as peapod.
[0241] Further, there is a technique for incorporating a fullerene
incorporating magnetic elements such as Gd@C.sub.82 or Dy@C.sub.82
in a nanotube. A method for forming a monolayer nanotube with the
fullerene built-in on a silicon substrate and a method for forming
a monolayer nanotube with the fullerene containing Gd built-in on a
silicon substrate are disclosed in, for example, Appl. Phys. Lett.
86, 023109 (2005).
[0242] A simple explanation will be given below. First, a catalyst
is arranged at a position where a monolayer nanotube is desired to
be grown, and the monolayer nanotube is caused to grow by a vapor
deposition method. Examples of a raw gas used include hydrocarbon
such as ethylene and methane, and alcohol such as ethanol. Gases
such as hydrogen, water or oxygen may be mixed to the raw gas.
[0243] As the vapor deposition method for growing the monolayer
carbon nanotube, it is possible to use a thermal CVD method, a
plasma CVD method or the like.
[0244] The monolayer carbon nanotube formed in such a way as above
is annealed at 470.degree. C. in a mixed gas atmosphere in which a
ratio of nitrogen and oxygen is 4:1. As a result, the tip end of
the carbon nanotube which does not come into contact with the
silicon substrate is made to be an opening end due to
oxidization.
[0245] Thereafter, the silicon substrate having the above structure
and the fullerene containing the magnetic metal are enclosed
together in a quartz ampoule, and its state is kept during two days
at 500.degree. C., thereby to obtain the fullerene containing the
magnetic metal.
[0246] Since Gd or Dy are the magnetic elements, the nanotube with
the fullerene containing the magnetic elements such as Gd@C.sub.82
or Dy@C.sub.82 built-in can be deformed due to the magnetic force,
so that the vicinity of the center of the nanotube can be brought
into contact/non-contact with the magnetic field generation section
by using this characteristic.
[0247] In the switching elements of FIGS. 18 and 19, the magnetic
switching elements of FIGS. 11 and 12 being the third embodiment
have been presupposed. However, in the magnetic switching element
of the first embodiment, it is possible to arrange plural magnetic
fine articles in the conductive tube.
[0248] (7) Seventh Embodiment
[0249] A seventh embodiment is obtained by combining the fourth
embodiment and the sixth embodiment. That is, plural magnetic fine
particles are incorporated in a conductive tube, and a channel of
an input signal IN and a channel of an output signal OUT are
separated, the signals causing the switch to perform ON/OFF
operation.
[0250] FIG. 20 is a plan view of a magnetic switching element
according to the seventh embodiment. FIG. 21 is a cross sectional
view taken along a line XXI-XXI of FIG. 20.
[0251] The conductive tube 14 is arranged while lying over from a
third electrode (terminal B) 24 to a fifth electrode 25. One end of
the conductive tube 14 is fixed to the third electrode 24 to become
a fixed end. Further, the other end of the conductive tube 14
exists on the fifth electrode 25 serving as a supporting stand.
However, the other end is not fixed to the fifth electrode 25 to
become a free end.
[0252] Like the sixth embodiment, plural magnetic fine particles 15
are arranged uniformly inside the conductive tube 14.
[0253] Further, the channel of the input signal IN is separated
from the channel of the output signal OUT. For this reason, the
magnetic field generation section 11 is buried completely on the
inside of an insulating layer 17. Instead, a fourth electrode
(terminal A) 23 which is respectively insulated from the magnetic
field generation section 11 and the fifth electrode 25 is arranged
in the surface area of the insulating layer 17.
[0254] The switching operation is performed in such a manner that
the magnetic fine particles 15 within the conductive tube 14 are
attracted due to a magnetic force, and a center portion of the
conductive tube 14 is brought into contact with the magnetic field
generation section 11. Since the other end of the conductive tube
14 is only placed on the fifth electrode 25 as the free end, the
switching operation is performed smoothly.
[0255] In the switching elements of FIGS. 20 and 21, the magnetic
switching elements of FIGS. 15 and 16 being the fourth embodiment
have been presupposed. However, for example, in the magnetic
switching element of the second embodiment, it is possible to
arrange plural magnetic fine particles in the conductive tube.
[0256] 3. Material Example
[0257] There will be explained about material examples.
[0258] (1) Magnetization fixed section and Magnetization free
section
[0259] A magnetization fixed section and a magnetization free
section constituting a magnetic element each are composed of a
ferromagnetic material. As the ferromagnetic material, for example,
a ferromagnetic material with the most suitable magnetic
characteristic is selected from the followings, in response to
applications of a switching element according to an example of the
present invention:
[0260] A. "Iron (Fe) simple substance", "Cobalt (Co) simple
substance", "Nickel (Ni) simple substance", and "alloy containing
at least one element selected from the group consisting of Iron
(Fe), Cobalt (Co), Nickel (Ni), Manganese (Mn) and Chrome
(Cr)";
[0261] B. "NiFe based alloy referred to as Permalloy", and "soft
magnetic material such as CoNbZr based alloy, FeTaC based alloy,
CoTaZr based alloy, FeAlSi based alloy, FeB based alloy, and CoFeB
based alloy"; and
[0262] C. "Half metal magnetic oxide such as Heusler alloy,
magnetic semiconductor, CrO.sub.2, Fe.sub.3O.sub.4, and
La.sub.1-XSrXMnO.sub.3, or half metal magnetic nitride".
[0263] Here, the "magnetic semiconductor" can be constituted of at
least one magnetic element selected from the group consisting of
Iron (Fe), Cobalt (Co), Nickel (Ni), Chrome (Cr) and Manganese
(Mn), and a compound semiconductor or oxide semiconductor. Specific
examples thereof include (Ga, Cr)N, (Ga, Mn)N, MnAs, CrAs, (Ga,
Cr)As, ZnO:Fe, and (Mg, Fe)O.
[0264] D. "Amorphous magnetic materials including Boron (B) such as
CoFeB", and "Amorphous magnetic materials including 3d-transition
metal and rare earth metal such as GdFeCo, TbFeCo".
[0265] Further, as the material used for the magnetization fixed
section and the magnetization free section, a continuous magnetic
substance may be constituted, or the material may have a complex
structure in which fine particles made of a magnetic substance are
deposited in a non-magnetic matrix.
[0266] An example of the complex structure includes one that is
called "granular magnetic substance".
[0267] The magnetization fixed section and the magnetization free
section may be constituted by plural magnetic layers with
antiferromagnetic coupling or ferromagnetic coupling. For example,
the magnetization fixed section and the magnetization free section
may have a stuck structure of ferromagnetic layer/non-magnetic
layer/ferromagnetic layer.
[0268] In the case where an antiferromagnetic coupling structure
referred to as a synthetic antiferromagnetic (SAF) structure is
adopted, it is preferable that a non-magnetic metal layer such as
Ruthenium (Ru), Iridium (Ir) or Chrome (Cr) and an
antiferromagnetic substance are used as a non-magnetic layer
arranged between two ferromagnetic layers. If he film thickness of
the non-magnetic layer is made a value within the range of 0.2 nm
to 3 nm, the antiferromagnetic coupling structure is formed
easily.
[0269] Further, the magnetization fixed section and the
magnetization free section may have a multilayered structure
composed of a plurality of magnetic layers. In this case, the
following materials may be used:
[0270] A. Two-layered structure composed of [(Co or CoFe
alloy)/(Permalloy alloy composed of NiFe or NiFeCo, or Ni)];
[0271] B. Three-layered structure composed of [(Co or CoFe
alloy)/(Permalloy alloy composed of NiFe or NiFeCo, or Ni)/(Co or
CoFe alloy)]; and
[0272] C. Multi-layer structure composed of [(Co or CoFe alloy)/(Pt
or Pd)].
[0273] (2) Anti-ferromagnetic Layer: AF
[0274] The magnetization direction of the magnetization fixed
section can be fixed absolutely in such a manner that the
antiferromagnetic layer is brought into contact with the
magnetization fixed section. The antiferromagnetic layer is
arranged so as to come into contact with a surface of a fixed
section which does not contact a non-magnetic intermediate layer.
The antiferromagnetic layer is selected from the group consisting
of, for example, iron manganese (FeMn), platinum manganese (PtMn),
palladium manganese (PdMn), and palladium platinum manganese
(PdPtMn).
[0275] (3) Non-magnetic Layer
[0276] The non-magnetic layer is constituted by a metal, an
insulator, a semiconductor or the like. The non-magnetic layer is
classified into two of low resistance material and high resistance
material from aspect of material constituting the non-magnetic
layer.
[0277] Examples of the low resistance material include copper (Cu),
gold (Au), silver (Ag), aluminum (Al), and an alloy containing at
least one element selected from the group consisting of copper
(Cu), gold (Au), silver (Ag) and aluminum (Al).
[0278] If the thickness of the non-magnetic layer (intermediate
layer) made of such a low resistance material is set to a value
within the range of 1 nm to 60 nm, a magnetization reversal
efficiency can be enhanced.
[0279] Examples of the high resistance material include an
insulator such as oxide, nitride or fluoride containing at least
one element selected from the group consisting of aluminum (Al),
titanium (Ti), tantalum (Ta), cobalt (Co), nickel (Ni), silicon
(Si), magnesium (Mg) and iron (Fe), and a semiconductor with large
energy gap, such as GaAlAs.
[0280] Examples of the oxide among such materials include alumina
(Al.sub.2O.sub.3-x), magnesium oxide (MgO), SiO.sub.2, Si--O--N,
Ta--O, and Al--Zr--O.
[0281] (4) First to fifth electrodes
[0282] It is preferable that the first to fifth electrodes are
composed of metallic materials with low resistance.
[0283] 4. Method of Manufacturing Conductive Tube and Magnetic Fine
Particle
[0284] It is preferable for the conductive tube to indicate
metallic property as an electrical characteristic, and the
conductive tube is composed of a carbon nanotube, for example.
[0285] In this case, a diameter of the tube is set to a value
within the range of 5 nm to 200 nm. Such a carbon nanotube is
referred to as a multilayered carbon nanotube. Further, in some
occasions, a tube whose diameter exceeds several tens nm may be
also called a carbon fiber.
[0286] Hereinafter, there will be described an example of a method
of manufacturing a conductive tube and magnetic fine particles by
taking the switching element of the first embodiment as an
example.
[0287] First, as shown in FIG. 22, a dummy electrode 27, which is
made of a conductive material such as tungsten, is formed on a
magnetic field generation section 11 via an insulating layer 26.
Further, on a third electrode 13, magnetic fine particles (magnetic
metal) 15 are formed which become a catalyst when a conductive tube
(carbon nanotube) is caused to grow.
[0288] Here, Fe, Co, Ni or the like is used as the magnetic fine
particles 15. Further, the magnetic fine particles 15 may be
Fe-based acetate, Co-based acetate, or Ni-based acetate.
[0289] The magnetic fine particles 15 are not necessary in the case
where the third electrode 13 it self becomes a catalyst when the
conductive tube is caused to grow, that is, in the case where the
third electrode 13 is composed of a magnetic metal (refer to FIG.
23).
[0290] Thereafter, as shown in FIG. 24, a conductive tube 14 is
caused to grow toward the dummy electrode 27 from the third
electrode 13.
[0291] As the growth method at this time, a method is known which
causes a monolayer carbon nanotube to grow by a thermal CVD method.
Examples of a raw gas used include hydrocarbon such as ethylene or
methane, and alcohol such as ethanol. Further, gases such as
hydrogen, water, and oxygen may be mixed to the raw gas. A growth
temperature is set to a value within the range of 400.degree. C. to
900.degree. C.
[0292] As to detail of the growth method, there is described in,
for example, Appl. Phys. A69, 305-308 (1999), or Jpn. J. Appl.
Phys. 42, 2416 (2003).
[0293] Growth is terminated when the tip end of the conductive tube
14 arrives at a position where the tip end is about to touch an
upper part of the magnetic field generation section 11, for
example, the dummy electrode 27.
[0294] Finally, when removing the insulating layer 26 and the dummy
electrode 27 by wet etching, the conductive tube 14 as the moving
element is formed as shown in FIG. 25.
[0295] Here, an etching liquid of the wet etching should be
composed of a substance which does not erode the magnetic fine
particles 15 (or the third electrode 13) as the catalyst of the
conductive tube 14, or the second electrode 11e within the magnetic
field generation section 11 which comes into contact with the
etching liquid at the time of etching.
[0296] Instead of this, for example, the second and third
electrodes 11e, 13 and the magnetic fine particles 15 may be
composed of an alloy insusceptible to corrosion, containing Ni, Fe,
Co, FePt, CoFe or the like. Further, after terminating growth of
the conductive tube 14, the surface of the magnetic fine particle
15 may be coated with a conductive non-magnetic material.
[0297] A cavity 18 in which the conductive tube 14 is arranged can
be formed easily in such a manner that after covering the
conductive tube 14 with a dummy layer made of, for example, carbon,
insulating layers 19, 20 are formed, and then the dummy layer is
removed.
[0298] In the case where the dummy layer is composed of a resist,
removal of the dummy layer can be performed by a vaporization
method of ashing.
[0299] By the way, in the case where the above-described
manufacturing method is applied to the second embodiment, the dummy
electrode 27 may be used as a fourth electrode which becomes one
end (terminal A) of the switch. In this case, a process for etching
the dummy electrode 27 becomes unnecessary.
[0300] In addition, the position of the dummy electrode 27 is not
limited to the upper part of the magnetic field generation section
11. For example, the dummy electrode 27 may be arranged at
periphery of the magnetic field generation section 11, the upper
part of the third electrode 13, or the like.
[0301] Furthermore, although control of length or the like of the
conductive tube becomes somewhat difficult in comparison with above
case, it is possible to cause the conductive tube to grow in the
condition of no dummy electrode. In this case, the length of the
conductive tube is controlled due to the growth speed determined by
the growth condition.
[0302] Moreover, as materials of the conductive tube, it is
possible to use materials excellent in mechanical elasticity, such
as Si-nanotube, in addition to the above carbon.
[0303] 5. Switching Principle A switching principle of the magnetic
switching element of an example of the present invention will be
described.
[0304] The basic structure of the magnetic field generation section
has, as already described, the magnetic element and the first and
second electrodes which put the magnetic element therebetween. The
magnetic element is composed of the magnetization fixed section
(magnetic layer), the magnetization free section (magnetic layer)
and the non-magnetic layer (intermediate layer) arranged between
these magnetic layers.
[0305] In an example of the present invention, the magnetization
direction of the magnetization free section is made to be parallel
or anti-parallel with respect to the magnetization direction of the
magnetization fixed section depending on ON/OFF operation of the
spin injection current. Then, motion of the conductive tube is
controlled depending on a leaked magnetic field from the magnetic
field generation section to carry out the switching.
[0306] (1) CASE A
[0307] FIG. 26 shows CASE A of the switching principle.
[0308] In the CASE A, the magnetic layer 11b becomes the
magnetization fixed section, and the magnetic layer 11d becomes the
magnetization free section. However, to the contrary, even though
the magnetic layer 11b becomes the magnetization free section and
the magnetic layer 11d becomes the magnetization fixed section, the
switching principle is not changed. In FIG. 26, in order to
magnetize and fix the magnetic layer 11b, it is preferable that an
antiferromagnetic layer is further provided between the magnetic
layer 11b and the first electrode 11a.
[0309] As the presupposed condition, the magnetic layer lid as the
magnetization free section has no hysteresis. Further, assume that
the magnetic layers 11b, 11d, in the initial state, maintain the
anti-parallel state due to magnetostatic coupling or negative
exchange interaction.
[0310] In this case, when the spin injection current is OFF
(initial state), no flowing of electrons is generated between the
first and second electrodes 11a, 11e, and the magnetic layers 11b,
11d remain to be the anti-parallel state.
[0311] At this time, as shown in, for example, FIG. 27, the
magnetic field lines which come out from the magnetic layers 11b,
11d become the state to be closed between the magnetic layers 11b,
11d. Consequently, values of the leaked magnetic field on the
external part of the magnetic element become very small.
[0312] Particularly, provided that absolute values of magnetization
of the magnetic layers 11b, 11d are set to be substantially the
same, the leaked magnetic field in this state becomes approximately
zero. More specifically, since no magnetic field is generated from
the magnetic element within the magnetic field generation section,
it is impossible to change the spatial position of the conductive
tube containing the magnetic fine particles, so that the switch
remains the OFF state in the case of normally-off-type while the
switch remains the ON state in the case of normally-on-type.
[0313] To the contrary, when the spin injection current is made ON
state, electron flow is generated between the first and the second
electrodes, the magnetization direction of the magnetic layer 11d
as the magnetization free section is reversed, and the magnetic
layers 11b, 11d are changed into the parallel state from the
anti-parallel state.
[0314] At this time, as shown in, for example, FIG. 28, the
magnetization of the magnetic layers 11b, 11d is not cancelled. For
this reason, the magnetic field lines leak to outside from the
magnetic layers 11b, lid, so that the magnetic field lines
generated from the magnetic layers 11b, 11d become opened
state.
[0315] Therefore, a state takes place where a magnetic field is
generated from the magnetic element within the magnetic field
generation section, so that the spatial position of the conductive
tube containing the magnetic fine particles changes by the magnetic
force according to the magnetic field (to approach to the magnetic
field generation section or to recede from the magnetic field
generation section).
[0316] That is, in the case of the normally-off-type, the switch
changes into ON from OFF, while in the case of the
normally-on-type, the switch changes into OFF from ON.
[0317] By the way, in the CASE A, the magnetic field generation
section has not the hysteresis characteristic. For this reason,
when the spin injection current is made zero, the magnetic field
generation section as the switch returns to the initial state
again.
[0318] FIG. 29 shows a relationship between the spin injection
current and a resistance value of the magnetic element.
[0319] The resistance value represents a magnetization state of the
magnetic layers 11b, 11d.
[0320] When the value of the spin injection current is zero, the
magnetic element is in the anti-parallel state, and its resistance
value becomes large.
[0321] When the spin injection current flows in a positive
direction and its current value exceeds predetermined value, the
magnetic element becomes the parallel state and its resistance
value becomes small.
[0322] Here, in the CASE A, there are two ways in which the spin
injection current is zero, and the spin injection current is made
to flow in the positive direction. The positive direction is a
direction in which the electrons flow from the magnetic layer 11b
serving as the magnetization fixed section toward the magnetic
layer 11d serving as the magnetization free section (opposite
direction as the spin injection current).
[0323] (2) CASE B
[0324] FIG. 30 shows CASE B of the switching principle.
[0325] In comparison with the CASE A, the CASE B has a
characteristic in that in the initial state, the magnetic layers
11b, 11d maintain the parallel state due to positive exchange
interaction.
[0326] In this case, the magnetic layers 11b, 11d are in the
parallel state when the spin injection current is made OFF (initial
state), and thus, the magnetic layers 11b, 11d become the state in
which the magnetic field is generated from the magnetic field
generation section. At this time, the switch is in the OFF state in
the case of normally-off-type, while the switch is in the ON state
in the case of normally-on-type.
[0327] On the contrary, when the spin injection current is made to
be ON state, the magnetization direction of the magnetic layer 11d
serving as the magnetization free section is reversed, so that the
magnetic layers 11b, 11d change into the anti-parallel state from
the parallel state.
[0328] Accordingly, a state takes place where the magnetic field is
not generated from the magnetic field generation section, so that
the magnetic force does not act on the conductive tube or the
magnetic fine particles. At this time, the switch changes to ON
from OFF in the case of normally-off-type, while the switch changes
to OFF from ON in the case of normally-on-type.
[0329] When the spin injection current is made zero, the switch
returns to the initial state again.
[0330] FIG. 31 shows a relationship between the spin injection
current and a resistance value of the magnetic element.
[0331] The resistance value represents a magnetization state of the
magnetic layers 11b, 11d.
[0332] When the value of the spin injection current is zero, the
magnetic element is in the parallel state, and its resistance value
becomes small.
[0333] When the spin injection current is made to flow in a
negative direction and its current value exceeds a predetermined
value, the magnetic element becomes the anti-parallel state and its
resistance value becomes large.
[0334] Here, in the CASE B, there are two ways in which the spin
injection current is zero, and the spin injection current is made
to flow in the negative direction. The negative direction is a
direction in which the electrons flow from the magnetic layer 11d
serving as the magnetization free section toward the magnetic layer
11b serving as the magnetization fixed section (opposite direction
as the spin injection current).
[0335] (3) CASE C
[0336] FIG. 32 shows CASE C of the switching principle. FIG. 31
shows a relationship between the spin injection current and a
resistance value of the magnetic element.
[0337] The CASE C is a case where although an interlayer coupling
of the magnetic layers 11b, 11d is weak, the hysteresis of the
magnetic layer 11d serving as the magnetization free section is
large.
[0338] In the CASE C, the magnetic layer 11b becomes the
magnetization fixed section, and the magnetic layer 11d becomes the
magnetization free section. However, to the contrary, the magnetic
layer 11b may become the magnetization free section and the
magnetic layer 11d may become the magnetization fixed section. In
order to magnetize and fix the magnetic layer 11b, it is preferable
that an anti-ferromagnetic layer is further provided between the
magnetic layer 11b and the first electrode 11a.
[0339] First, when the spin injection current is made to flow in
the negative direction and its current value exceeds a
predetermined value (critical current), the magnetic element
becomes the anti-parallel state and its resistance value becomes
large. In the anti-parallel state, as shown in, for example, FIG.
27, the magnetic field lines which come out from the magnetic
layers 11b, 11d become the state to be closed between the magnetic
layers 11b, 11d. Consequently, values of the leaked magnetic field
on the external part of the magnetic element become small.
[0340] Therefore, it is impossible to change the spatial position
of the conductive tube containing the magnetic fine particles, so
that the switch remains to be the OFF state.
[0341] Thereafter, even though the spin injection current is cut
off, this state remains since the magnetization free section has
the hysteresis. That is, the magnetic element within the magnetic
field generation section remains to be the anti-parallel state to
become a non-volatile switch.
[0342] To the contrary, when the spin injection current is made to
flow in the positive direction and its current value exceeds a
predetermined value (critical current), the magnetic element
becomes the parallel state and its resistance value becomes small.
In the parallel state, as shown in, for example, FIG. 28, the
magnetic field lines which come out from the magnetic layers 11b,
11d become the open state, and thus, values of the leaked magnetic
field leaked on the external part of the magnetic element become
large.
[0343] Therefore, the spatial position of the conductive tube
containing the magnetic fine particles changes by the magnetic
force according to the magnetic field (to approach to the magnetic
field generation section or to recede from the magnetic field
generation section).
[0344] That is, the switch changes to ON from OFF.
[0345] Thereafter, even though the spin injection current is cut
off, this state remains since the magnetization free section has
the hysteresis. That is, the magnetic element within the magnetic
field generation section remains to be the parallel state, to
become a non-volatile switch.
[0346] In the CASE C, there are three ways in which the spin
injection current is zero, the spin injection current is made to
flow in the negative direction, and the spin injection current is
made to flow in the positive direction.
[0347] (4) CASE D
[0348] FIG. 34 shows CASE D of the switching principle.
[0349] The CASE D is characterized in that, in an initial state,
the magnetic layer 11b serving as the magnetization fixed section
has a synthetic antiferromagnetic (SAF) structure, and that the
magnetic layer 11d serving as the magnetization free section is in
a heat fluctuation state (state in which magnetic pole is not
determined as a whole).
[0350] When the spin injection current is OFF (initial state), no
electron flow occurs between the first and second electrodes 11a,
11e, and the magnetic layer 11d serving as the magnetization free
section is in the heat fluctuation state.
[0351] At this time, in the magnetization fixed section having the
SAF structure, the magnetization of the plural magnetic layers
which are antiferromagnetically coupled is cancelled, and
therefore, there is no leaked magnetic field from the magnetization
fixed section. Further, since the magnetic layer 11d constituting
the magnetization free section is also in the heat fluctuation
state, the magnetization direction is not determined in the state
that no spin injection current flows, and thus, there is no
generation of the magnetic field.
[0352] Accordingly, since no magnetic field is generated from the
magnetic element within the magnetic field generation section, it
is impossible to change the spatial position of the conductive tube
containing the magnetic fine particles, and thus, the switch is in
the OFF state.
[0353] To the contrary, when the spin injection current is made ON,
flow of the electrons is generated between the first and second
electrodes 11a, 11e, so that the magnetization direction of the
magnetic layer 11d serving as the magnetization free section is
determined. For example, in the case where the flow of the
electrons heads toward the magnetization free section from the
magnetization fixed section, the magnetization of the magnetic
layer 11d serving as the magnetization free section faces to the
right direction on the drawing. At this time, as described above,
the magnetization of the plural antiferromagnetic coupling magnetic
layers is cancelled in the magnetization fixed section having the
SAF structure. As a consequence, the leaked magnetic field from the
magnetization fixed section can be approximately zero. For this
reason, a state is established in which the magnetic field is
generated from the magnetic layer 11d where the magnetic pole is
determined as a whole.
[0354] Therefore, the spatial position of the conductive tube
containing the magnetic fine particles changes by the magnetic
force according to the magnetic field (to approach to the magnetic
field generation section or to recede from the magnetic field
generation section).
[0355] That is, the switch changes to ON from OFF.
[0356] By the way, when the spin injection current is cut off in
the CASE D, the switch returns to the initial state (the heat
fluctuation state of the magnetic layer 11d) again.
[0357] In the CASE D, the electrons are made to flow in the
direction toward the magnetization free section from the
magnetization fixed section (opposite direction as the spin
injection current), so that the magnetization of the magnetic layer
11d is made to face to the right. However, instead of this, the
electrons are made to flow in the direction toward the
magnetization fixed section from the magnetization free section, so
that the magnetization of the magnetic layer 11d may be made to
face to the left.
[0358] (5) CASE E
[0359] FIG. 35 shows CASE E of the switching principle.
[0360] The CASE E is characterized in that the magnetic layer 11b
serving as the magnetization fixed section has the SAF structure,
and that the magnetic layer 11d serving as the magnetization free
section has the hysteresis. In order to magnetize and fix the
magnetic layer 11b, it is preferable that an antiferromagnetic
layer is provided between the magnetic layer 11b and the first
electrode 11a.
[0361] First, when the spin injection current is made to flow in
the positive direction and its current value exceeds predetermined
value (critical current), the magnetization direction of the
magnetic layer 11d serving as the magnetization free section faces
to the right, and the magnetic element becomes the parallel
state.
[0362] At this time, in the magnetization fixed section having the
SAF structure, the magnetization of the plural magnetic layers
which are antiferromagnetically coupled is cancelled. Consequently,
regardless of presence/absence or direction of the spin injection
current, the leaked magnetic field from the magnetization fixed
section can be made to be approximate zero.
[0363] Therefore, the conductive tube containing the magnetic fine
particles acts upon the magnetic field from the magnetic layer 11d
serving as the magnetization free section.
[0364] Thereafter, even though the spin injection current is cut
off, this state remains since the magnetization free section has
the hysteresis. That is, the magnetic element within the magnetic
field generation section remains the parallel state.
[0365] To the contrary, when the spin injection current is made to
flow in the negative direction and its current value exceeds a
predetermined value (critical current), the magnetization direction
of the magnetic layer 11d serving as the magnetization free section
faces to the left, and the magnetic element becomes the
anti-parallel state.
[0366] At this time, in the magnetization fixed section having the
SAF structure, the magnetization of the plural magnetic layers
which are antiferromagnetically coupled is cancelled. For this
reason, regardless of presence/absence or direction of the spin
injection current, the leaked magnetic field from the magnetization
fixed section can be made to be approximate zero.
[0367] Accordingly, the conductive tube containing the magnetic
fine particles acts upon the magnetic field with the opposite
direction to the above-described case from the magnetic layer 11d
serving as the magnetization free section.
[0368] Thereafter, even though the spin injection current is cut
off, this state remains since the magnetization free section has
the hysteresis. That is, the magnetic element within the magnetic
field generation section remains the anti-parallel state.
[0369] In the CASE E, the direction of the magnetic field lines of
the generated magnetic field changes depending on the direction
(magnetization direction of the magnetic layer 11d) of the spin
injection current. The switching is carried out by utilizing a
repulsive force and an attractive force acting upon between the
magnetic fine particles and the magnetic field generation section
such that the switching is performed with difference of direction
of the lines of the magnetic force. The switching is made, for
example, in such a manner that the polarity of the fine particles
is controlled while adjusting the coercive force and the magnetic
anisotropy of the magnetic fine particles provided at the
conductive tube.
[0370] Note that, in the CASE A to the CASE E, the thickness or
planar shape of the magnetic layer 11d may be different from the
magnetic layer 11b. For example, a shape as a whole of the magnetic
field generation section is made to be trapezoid, and the planar
shape may become small gradually with heading toward the second
electrode 11e from the first electrode 11a.
[0371] 6. Manufacturing Method There will be described about an
example of a manufacturing method.
[0372] In the example, the case of manufacturing the magnetic
switching element of FIGS. 6 and 7 according to the second
embodiment will be described.
[0373] In FIGS. 6 and 7, the magnetic element within the magnetic
field generation section 11 is composed of CoFe (6 nm)/Cu (8
nm)/CoFeB (8 nm). That is, the magnetic layer 11b is defined as the
magnetization fixed section, and is composed of CoFe with thickness
of 6 nm. Further, the magnetic layer 11d is defined as the
magnetization free section, and is composed of CoFeB with thickness
of 8 nm. The non-magnetic layer (intermediate layer) 11c is
composed of Cu with thickness of 8 nm.
[0374] The switching element is formed by the following
manufacturing method.
[0375] First, the first electrode 11a is formed on a wafer, and
then, the wafer is arranged in an ultra vacuum sputtering device.
Then, after forming a lamination layer composed of CoFe (6 nm)/Cu
(8 nm)/CoFeB (8 nm), the second electrode 11e is formed on the
lamination layer.
[0376] Next, electron beam (EB) resist is applied thereon, and EB
exposure is performed. As a result, a four-sided mask with size of,
for example, 70 mm.times.100 nm is formed. Here, assume that the
long side of the four-sided figure is in parallel to the direction
of the axis of easy magnetization (direction with magnetic
anisotropy) of the magnetic layers 11b, 11d.
[0377] Further, using an ion milling device, the first and second
electrodes 11a, 11e in the region not covered with the mask and the
lamination layer composed of CoFe (6 nm)/Cu (8 nm)/CoFeB (8 nm) are
etched to form the magnetic field generation section 11.
Thereafter, the mask is separated.
[0378] Next, the magnetic field generation section 11 is covered
with, for example, an insulating layer made of SiO.sub.2, and a
surface of the insulating layer is smoothed by the ion milling to
expose an upper surface of the second electrode 11e of the magnetic
field generation section 11 from the insulating layer. A lead layer
is connected to the exposed second electrode 11e.
[0379] Similarly, for example, the third electrode 13 made of Ni
with column shape of diameter 20 nm is formed due to the EB
exposure and the etching. Then, the wafer is arranged in a vacuum
chamber, and alcohol gas is introduced toward the wafer at
temperature of 40.degree. C. As a result, the carbon nanotube grows
on the third electrode 13.
[0380] The magnetic switching element is formed by the above
manufacturing method.
[0381] 7. Application
[0382] The magnetic switching element according to the example of
the present invention can be applied to a signal processing device
composed of logic circuits.
[0383] (1) First Application
[0384] FIG. 36 shows an example of a case where the magnetic
switching element according to the example of the invention is used
as an inverter circuit.
[0385] In the case where the magnetic switching element according
to the example of the invention is used as an inverter circuit, one
switch unit may be prepared.
[0386] When an input signal Vin is "0", no voltage is applied
between the first electrode 11a and the second electrode 11e, while
when the input signal Vin is "1", voltage is applied between the
first electrode 11a and the second electrode 11e. In the state that
the voltage is applied between the first electrode 11a and the
second electrode 11e, the spin injection current of 50 .mu.A flows
into the magnetic element.
[0387] In the first application, in order to cause the magnetic
switching element to function as the inverter circuit, a channel of
the input signal Vin and a channel of an output signal Iout are
separated, and further, the magnetic switching element is made to
be, for example, the normally-on-type to which the CASE B of the
switching principle is applied.
[0388] As shown in, for example, FIGS. 38 and 39, the magnetization
fixed section and the magnetization free section within the
magnetic field generation section 11 are ferromagnetically coupled
(parallel state in the initial state) by controlling materials,
thickness and the like of the non-magnetic layer (intermediate
layer).
[0389] Here, as the non-magnetic layer, Cu with thickness of 1.5 nm
is used, and as the magnetization free section, CoFeB with
thickness of 4 nm is used. The magnetization fixed section is
composed of CoFe with thickness of 3 nm functioning as a pinned
layer and PtMn serving as an antiferromagnetic layer for fixing
magnetization of the pinned layer.
[0390] In such a switching element, as shown in waveform diagram of
FIG. 37, the magnetic element is in the parallel state when the
input signal Vin is "0", and the magnetic field is generated from
the magnetic field generation section 11. As a consequence, the
terminal A and the terminal B are short circuited, the switch is
made ON, and the output signal Iout becomes "1".
[0391] Further, when the input signal Vin is "1", the magnetic
element is in the anti-parallel state, and the magnetic field is
not generated from the magnetic field generation section 11. For
this reason, the terminal A is separated from the terminal B, the
switch is made OFF, and the output signal Iout becomes "0".
[0392] Thus, according to the example of the invention, it is
possible to constitute the inverter circuit by using one switch
unit.
[0393] (2) Second Application
[0394] FIG. 40 shows an example of a case where the magnetic
switching element according to the example of the invention is used
as an AND gate circuit.
[0395] In the case where the magnetic switching element according
to the example of the invention is used as the AND gate circuit,
two switch units connected in series may be used.
[0396] In the respective switch units, no voltage is applied
between the first electrode 11a and the second electrode 11e when
the input signals V1, V2 are "0", while voltage is applied between
the first electrode 11a and the second electrode 11e when the input
signals V1, V2 are "1". In the state that the voltage is applied
between the first electrode 11a and the second electrode 11e, the
spin injection current of 50 .mu.A flows into the magnetic
element.
[0397] In the second application, in order to cause the magnetic
switching element to function as the AND gate circuit, a channel of
the input signals V1, V2 and a channel of the output signal Iout
are separated, and further, the magnetic switching element is made
to be, for example, the normally-off-type to which the CASE D of
the switching principle is applied.
[0398] For example, assume that, in the respective switch units,
the magnetization fixed section within the magnetic field
generation section 11 has the SAF structure (refer to FIG. 34).
That is, two ferromagnetic layers within the magnetization fixed
section are antiferromagnetically coupled by controlling materials,
thickness and the like of the non-magnetic layer within the
magnetization fixed section.
[0399] Here, an antiferromagnetically coupled film made of
CoFe/Ru/CoFe is used as the magnetization fixed section. Further,
PtMn is arranged between the antiferromagnetically coupled film and
the first electrode, the magnetization direction is fixed firmly
due to exchange bias. In addition, assume that the magnetization
free section is made of NiFe, and has a size to become heat
fluctuation state at room temperature.
[0400] As shown in a waveform diagram of FIG. 41, when the input
signals V1, V2 are "00", "01", "10" in such a switching element,
the magnetization free section of at least one of two switch units
is in the heat fluctuation state, so that the state is established
in which no magnetic field is generated from the magnetic field
generation section 11.
[0401] For this reason, at least one of the two switch units is in
the OFF state, so that the input signal Iout becomes "0".
[0402] Further, when the input signals V1, V2 are "11", the
magnetization direction of the magnetization free section within
the two switch units is determined. Consequently, the two switch
units are in the ON state, so that the output signal Iout becomes
"1".
[0403] Thus, according to the example of the invention, it is
possible to constitute the AND gate circuit by using two switch
units.
[0404] (3) Third Application
[0405] FIG. 42 shows an example of a case where the magnetic
switching element according to the example of the invention is used
as OR gate circuit.
[0406] In the case where the magnetic switching element according
to the example of the invention is used as the OR gate circuit, two
switch units connected in parallel may be used.
[0407] In the respective switch units, no voltage is applied
between the first electrode 11a and the second electrode 11e when
the input signals V1, V2 are "0", while voltage is applied between
the first electrode 11a and the second electrode 11e when the input
signals V1, V2 are "1". In the state that the voltage is applied
between the first electrode 11a and the second electrode 11e, the
spin injection current of 50 .mu.A flows into the magnetic
element.
[0408] In the third application, in order to cause the magnetic
switching element to function as the OR gate circuit, a channel of
the input signals V1, V2 and a channel of the output signal Iout
are separated, and further, the magnetic switching element is made
to be, for example, the normally-off-type to which the CASE D of
the switching principle is applied.
[0409] For example, assume that, in the respective switch units,
the magnetization fixed section within the magnetic field
generation section 11 has the SAF structure (refer to FIG. 34).
That is, two ferromagnetic layers within the magnetization fixed
section are antiferromagnetically coupled by controlling materials,
thickness and of the non-magnetic layer within the magnetization
fixed section.
[0410] Here, like the second application, an antiferromagnetically
coupled film made of CoFe/Ru/CoFe is used as the magnetization
fixed section. Further, PtMn is arranged between the
antiferromagnetically coupled film and the first electrode, and the
magnetization direction is fixed firmly due to exchange bias. In
addition, assume that the magnetization free section is made of
NiFe, and has a size to become heat fluctuation state at room
temperature.
[0411] As shown in a waveform diagram of FIG. 43, when the input
signals V1, V2 are "00" in such a switching element, the
magnetization free sections of two switch units are in the heat
fluctuation state, so that the state is established in which no
magnetic field is generated from the magnetic field generation
section 11.
[0412] For this reason, the two switch units are in the OFF state,
so that the input signal Iout becomes "0".
[0413] In addition, when the input signals V1, V2 are "01", "10"
and "11", the magnetization direction of the magnetization free
section within at least one of two switch units is determined. As a
consequence, the at least one switch unit is in the ON state, so
that the output signal Iout becomes "1".
[0414] Thus, according to the example of the invention, it is
possible to constitute the OR gate circuit by using two switch
units.
[0415] (4) The Others
[0416] In the case of realizing an information processing device by
using the magnetic switching element according to the example of
the invention, two methods are available as the method in which
plural switch units are related to each other.
[0417] One is a method in which an output signal of the front-stage
switch unit is used as a control signal of the rear-stage switch
unit.
[0418] For example, in the information processing device shown in
FIG. 44, the CASE A is used as the switching principle of the
front-stage switch unit, while the CASE A and the CASE B are used
as the switching principle of the rear-stage switch unit, whereby
it is possible to realize a multiplexer (selection circuit) which
outputs output signals V2, V3 selectively based on the value of the
control signal V1.
[0419] Further, in the information processing device shown in FIG.
45, it is possible to realize a delay circuit composed of three
stages of a buffer in such a manner that the CASE A or the CASE D
is used as the switching principle of each switching unit, and
these are caused to function as the buffer.
[0420] The other is a method in which terminals A or terminals B
are connected with each other, or the terminal A is connected to
the terminal B with respect to the plural switch units.
[0421] According to this method, it is possible to realize the
logic circuit such as the AND gate circuit or the OR gate circuit
as shown in the second and third applications.
[0422] 7. Application Example
[0423] There will be described an application example.
[0424] Because of characteristic of capable of being formed on the
silicon substrate, the magnetic switching element according to the
example of the invention can be applied to a semiconductor
integrated circuit such as a semiconductor memory, a logic LSI or a
memory mixed logic LSI.
[0425] Further, the example of the invention can be also applied to
discrete products in which only one function (for example, an
inverter, a multiplexer or the like) is formed in one chip.
[0426] Hereinafter, there will be described a case where the
example of the invention is applied to a semiconductor memory.
[0427] FIG. 46 shows a semiconductor memory in which a memory cell
array is laminated.
[0428] As elements composing the semiconductor memory, there are
roughly a memory cell array and a peripheral circuit. In the
two-dimensional layout in which the memory cell array and the
peripheral circuit are arranged flatly on a chip 28, limits already
take place in realization of high density of elements due to micro
miniaturization.
[0429] Accordingly, realization of 3D of the semiconductor memory
is investigated. However, although the laminated structure in
connection with the memory cell array is realized relatively easy,
realization of 3D is very difficult with respect to the peripheral
circuit serving as the logic circuit. This is caused by the fact
that laminating the MOS transistor as the switch is difficult.
[0430] In the example of the invention, the peripheral circuit is
composed of the magnetic switching elements instead of the MOS
transistor. Therefore, also concerning the peripheral circuit, the
laminated structure can be realized relatively easy. Consequently,
according to the example of the invention, true realization of 3D
can be realized.
[0431] FIG. 47 shows an image of the laminated structure of the
semiconductor memory with 3D shaped.
[0432] On the surface region of the semiconductor substrate (chip)
28, a CMOS circuit is formed. In the memory cell array region, a
memory cell (magnetoresistance effect element) is stacked, and in
the peripheral circuit region, the switch unit according to the
example of the invention is stacked.
[0433] Although a wiring is also stacked, the periphery of the
wiring is made to be the cavity by utilizing the cavity necessary
for the switch unit, and it is possible to realize a so-called
aerial wiring structure. In this case, since parasitic capacitance
produced between the wirings is reduced, it is possible to
contribute to further high speed operation.
[0434] Note that application of the example of the invention is not
limited to kind of the semiconductor memory. For example, the
application to a programmable random access memory (PRAM), a
magnetic random access memory (MRAM) or the like is possible.
[0435] Furthermore, according to the example of the invention, it
is possible to scheme realization of 3D concerning signal
processing devices, such as, for example, a micro computer, a micro
processor, a graphic processor, a DSP, and an operation processing
circuit.
[0436] The greatest benefit of realization of 3D in these signal
processing devices is that the information transmitting speed can
be improved, in other words, it is possible to widen a band width.
This is because, in the three-dimensional layout, circuit blocks
are adjacent to each other with not a line but a face, so that in
comparison with the two-dimensional layout, it is possible to
shorten a bus for connecting the circuit blocks with each other and
to increase the number of such buses.
[0437] In addition, the non-volatile switching element of the
present invention can be applied to a programmable logic such as a
field programmable gate allay (FPGA).
[0438] FIG. 48 shows a structure image of FPGA.
[0439] Within the chip 28, wiring channels 30 are arranged
vertically and horizontally in advance together with plural logical
blocks 29. As a switching matrix necessary for connection between
the logical blocks 29, the present example uses the magnetic
switching element (switch unit) 31 instead of anti-fuse or SRAM. In
this case, rewriting to the switching element becomes possible, and
even though the power supply is turned off, the nonvolatile state
can remain, which makes it possible to contribute to the power
saving.
[0440] 8. The Others
[0441] According to the examples of the present invention, it is
possible to provide a magnetic switching element in which the
ON/OFF resistance is infinity, the ON resistance is very small, and
miniaturization is possible, and further the magnetic switching
element is based on new principle capable of maintaining the switch
state in nonvolatile, and also a signal processing device using the
same.
[0442] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *