CN1703780A - Memory device and memory - Google Patents

Memory device and memory Download PDF

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Publication number
CN1703780A
CN1703780A CN 200380100824 CN200380100824A CN1703780A CN 1703780 A CN1703780 A CN 1703780A CN 200380100824 CN200380100824 CN 200380100824 CN 200380100824 A CN200380100824 A CN 200380100824A CN 1703780 A CN1703780 A CN 1703780A
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spin
memory element
layer
ferromagnetic
ferromagnetic layer
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角野宏治
阿多誠文
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Sony Corp
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Sony Corp
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Abstract

A memory element wherein a spin conduction layer having a sufficient spin coherence length and a uniform spin field can be obtained, and thereby practical use is attained and a memory device are provided. A spin conduction layer (paramagnetic layer) ( 24 ) is a fullerene thin film being from 0.5 nm to 5 mum thick, for example. The fullerene has a hollow sized, for example, from 0.1 nm to 50 nm. A paramagnetic material is included in this hollow. A fermi vector of the fullerene thin film well laps over small number of spin band or plenty of spin band of a ferromagnetic fixed layer ( 23 ) and a ferromagnetic free layer ( 25 ). Further, spin orientations of the included paramagnetic material are random. Further, electron spin in the fullerene is in a quantized state in a pseudo zero dimensional space. Thereby, a spin coherence length becomes long in the fullerene thin film, and scatteration of spin-polarized conduction electrons goes away.

Description

Memory element and storage device
Technical field
The present invention relates to a kind of being used for writes the memory element of recorded information by injecting spinning polarized electron, and the storage device that adopts this memory element.
Background technology
Under the situation that express network society has arrived, popularize rapidly at mobile device such as mobile phone such as laptop computer, need the exploitation permanent memory especially.Permanent storage is can preserve data need not often it to be provided under the situation of electrical power.So, in using permanent memory, after power connection, just can turn round at once.And, can reduce power consumption.
A kind of MAGNETIC RANDOM ACCESS MEMORY of noticing recently (MRAM) comprises the high density of the high speed characteristics of SRAM (static RAM (SRAM)) and DRAM (dynamic ram) and characteristics cheaply, and the permanent character of instantaneous (flash) memory.So, in fact can regard MRAM as the standard of following memory likely.MRAM is a kind of memory that utilizes magnetic effect.In MRAM, known have the spin threshold type memory that utilizes giant magnetoresistance effect and utilize spin correlation type tunnel effect memory.In these MRAM, be added to switching current corresponding to the wiring of Destination Storage Unit and produce magnetic field, changed the magnetized state of recording layer in the unit and write unit information by this magnetic field.Come sense information by utilizing magnetic effect by the magnetized state of probe unit.As mentioned above, MRAM is a kind of solid-state memory.So, there is not the danger of damage, it can be present in the magnetic recording media, is used for writing and reading by utilizing magnetic head mechanically to finish.MRAM also is good at writing and reading of repetition.
But, concerning the practicality of MRAM, stayed the problem that the high density by memory causes simultaneously.Be used to write the required magnetic intensity and the width of recording layer, promptly the size of a unit is inversely proportional to.So when making the memory cell miniaturization, it is very big that power consumption but becomes.And, exist the danger of the cross interference that causes by immediate stray field between adjacent cells.For example, concerning the wide memory cell of 0.2 μ m, it is several mA that write current becomes.And concerning its cell distance was contracted to the memory of about 0.1 μ m, when being the object element induced field, the magnetic field with its 80% intensity was added to its adjacent unit.
As a kind of technology that solves the front problem, proposed to adopt the MRAM (with reference to flat 11-120758 Japanese unexamined patent bulletin) of the new wiring method that is called polarization spin injection method.This memory element is built into as shown in Figure 22.In other words, the ferromagnetic layer (free layer) that changes according to binary bit information of the always fixing ferromagnetic layer (fixed bed) 111 of its direction of magnetization and its direction of magnetization 112 is separated by paramagnetic layer 113. Paramagnetic metal layer 114 and 115 is electrode layers, is used at laminating direction electric current being added to ferromagnetic layer 111 and 112.In the polarization spin injection method, polarized electron is injected in ferromagnetic layer 111 and 112, and transmits spin angular momentaum by applying spin polarized current at laminating direction.Thereby in ferromagnetic layer 112, magnetic moment is by the mutual effect back.This mechanism is called spin flip conversion.In wiring method, wherein magnetization be by as above-mentioned injection spinning current come conversion, need not to revolve and add external magnetic field.So it is not subjected to the interference between memory cell, but and limit dissipation power.The further feature of polarization spin injection is that also its write time is only relevant with the spin conductivity.So, can improve responsiveness.
But, in this technology, a problem is arranged also in actual applications.Be configured in the paramagnetic layer 113 between ferromagnetic layer 111 and 112, except effect, also have method, be used for there be not the polarization spin of conduction electron under the situation of relaxation as the spin conduction as the magnetic liner.So paramagnetic layer 113 is necessary to have long spin coherence length, and a kind of material that ferromagnetic layer 111 and 112 has a very little scattering made.
In other words, when spin orientation by, for example, when the scattering of the spin polarization conduction electron in paramagnetic layer 113 was changed, the spin information of conduction electron lost.So the paramagnetic material with long spin coherence length is desirable.So far, passed through to adopt the paramagnetic metal material about the research of paramagnetic layer spin conduction, the material of semi-conducting material and the like is implemented.
But, when top material is used as the paramagnetic layer, but be difficult to generate uniform film and control spin coherence length.So, in the paramagnetic layer, exist to obtain enough spin coherence lengths and even problem from curl field.As a result,, significant characteristic can be obtained, enough characteristics can not be obtained in practice though point out in theory to compare with the magnetic field method of inducting of routine about the memory element of spin injection method.So, can not obtain actual application.
Because aforementioned, purpose of the present invention is exactly will provide a kind of can obtain enough spin coherence lengths and even memory element from curl field in the paramagnetic layer, and realizes the application of its reality thus and adopt its a kind of storage device.
Summary of the invention
Memory element according to the present invention is a kind of memory element that writes recorded information wherein by the electronics that injects spin polarization, comprise: the spin conducting shell of making by spherical shell with hollow or column type molecular material, and wherein the electronics of spin polarization conducts by the spin conducting shell.
More precisely, memory element of the present invention is a kind of memory element, and it mainly comprises: the direction of magnetization is first ferromagnetic layer of fixing therein; Hollow spherical shell molecular material makes by having, and is formed on the spin conducting shell above first ferromagnetic layer, comprises paramagnetic material and has known spin coherence length in this spin conducting shell; And second ferromagnetic layer that on the spin conducting shell of the first ferromagnetic layer opposite, one side, forms, wherein the direction of magnetization is changed by spinning polarized electron, wherein writes recorded information by the direction of magnetization that changes second ferromagnetic layer.
In this memory element, when spinning electron being injected in second ferromagnetic layer, just change the direction of magnetization of second ferromagnetic layer, and write recorded information.Then, spinning polarized electron stream is dirty in this paramagnetic layer that comprises that paramagnetic material (for example, fullerene) is made in the situation of the scattering of not spinning, and this paramagnetic layer has enough spin coherence lengths and evenly from curl field.In other words, this injects electronics by the conduction of paramagnetic layer, keeps their spin polarization degree simultaneously.
Secondly, memory element of the present invention is a kind of memory element, comprising: first and second ferromagnetic layers, wherein its at least the change of the direction of magnetization of one deck induct by injecting spinning polarized electron; And by setting its hollow cylindrical molecule that axially disposes by the laminating direction of aiming at first and second ferromagnetic layers (for example, carbon nano-tube) the spin conducting shell that at least a portion in constitutes, this conducting shell is set between first ferromagnetic layer and second ferromagnetic layer shielding the mutual effect of its magnetic, and the conduction spinning polarized electron.
In storage device, electric current scrolls up at the hollow, the cylindrical molecular axis that play a part the spin conducting shell.Therefore, spinning polarized electron conducts between first ferromagnetic layer and second ferromagnetic layer.In the spin conducting shell, electronics is not having under the situation of spin relaxation, conducted according to cylindrical molecule or the spin coherence length that is included in the material of its hollow bulb, and to first ferromagnetic layer and given its angular momentum of second ferromagnetic layer.
Storage device of the present invention constitutes by arranging a plurality of the invention described above memory elements.
The accompanying drawing summary
Fig. 1 illustrates the figure of the construction profile figure of memory element first society according to the present invention;
Fig. 2 is the figure of memory cell figure;
Fig. 3 is the view for the crystal structure of the fullerene thin film of explaining purposes spin conducting shell (paramagnetic layer);
Fig. 4 A is the figure figure that is written to the operation in the memory cell for explanation to 4C;
Fig. 5 A also is for explaining the figure figure of write operation to 5C;
Fig. 6 A is the figure figure that illustrates the memory cell read output signal to 6B;
Fig. 7 A also is the figure figure that illustrates the memory cell read output signal to 7B;
Fig. 8 is for explaining the view of memory cell addressing scheme;
Fig. 9 also is for explaining the view of addressing scheme;
Figure 10 is a vertical view of making the memory element step that is shown in Fig. 1 for explaining;
Figure 11 A is a cross-sectional view with the step after Figure 10 to 11C;
Figure 12 is the cross-sectional view with the step after Figure 11 C;
Figure 13 is the vertical view of Figure 12;
Figure 14 A is a cross-sectional view with the step after Figure 12 to 14C;
Figure 15 A is a cross-sectional view with the step after Figure 14 C to 15C;
Figure 16 is Figure 15 C vertical view;
Figure 17 is the view that the modification of memory cell is shown;
Figure 18 is the view that another modification of memory cell is shown;
Figure 19 is the topology view of memory element second society according to the present invention;
Figure 20 is by being shown in the structure outline figure that Figure 19 memory element assembles the storage device that integral body constitutes;
Figure 21 is the view that the modification of this memory element is shown; And
Figure 22 is the topology view of conventional spin injection type memory element.
Embodiment
(first embodiment)
Fig. 1 illustrates the structure of the first enforcement memory element according to the present invention.Memory element MM1 is a kind of " spin injection type " element of causing magnetization inversion to finish to write by the spinning electron by injecting and polarizing of being used for.Fig. 2 illustrates the extraction memory cell 20 that constitutes memory element MM1.
Memory element MM1 is state (for example, the capable array as the N row of M: the MXN array) that therein a plurality of memory cell 20 is arranged in square formation.The recorded information of memory cell 20 writes (spin injection method) by spinning polarized electron stream being injected into each memory cell 20.Preferably, this memory cell 20 planar is of a size of from 0.5mm 2To 5 μ m 2When the size of memory cell is hour, can cause cross interference.Write current owing to arrive each memory cell 20 adjacent one another are by the size that is set to the front might become the influence that suppresses magnetic field.
Memory cell 20 comprises substrate 21.In substrate 21, form electrode layer 22.The ferromagnetic fixed layer that formation is made by ferromagnetic material (first ferromagnetic layer) 23.In ferromagnetic fixed layer 32, the direction of magnetization is fixed in given direction.On ferromagnetic fixed layer 23, form spin conducting shell 24.In this embodiment, spin conducting shell 24 is made by the spherical shell molecular material that comprises paramagnetic material, for example, and carbon molecule fullerene.Its detailed description will be in providing after a while.On spin conducting shell 24, form the ferromagnetic spin of making by layer (second ferromagnetic layer) 25 by ferromagnetic material.Ferromagnetic free layer 25 has two stable direction of magnetizations, and is oriented to a direction in two direction of magnetizations.The direction of magnetization of ferromagnetic free layer 25 changes according to the spin of conduction electron.On ferromagnetic free layer 25, form electrode layer 26.
Substrate 21 be by, for example, silicon (Si) is made.Electrode layer 22 and 26 is by making such as the paramagnetic metal of gold (An).As paramagnetic material, can adopt and the different any material of gold, as long as use this material, by sedimentation, sputtering method and similar method thereof can easily be fabricated into lead on electrode layer 22 and 26 just.
Spin conducting shell 24 is a kind of fullerene thin film of being made by fullerene 24a above mentioned, that comprise paramagnetic material 24b.Its thickness is that for example, to 5 μ m, this fullerene thin film has crystal structure as shown in Figure 3 from 0.5nm.In general fullerene has the lattice structure of fcc (face-centered cubic).But, in this figure, for convenience it is expressed as the simple lattice of bidimensional.
Fullerene 24a has, for example, and the hollow size from 0.1nm to 50nm.At this hollow space, comprise paramagnetic material 24b.The example of fullerene 24a comprises C 36, C 60, C 70, C 72, C 74, C 76And C 82, the example of paramagnetic material 24b comprises such as lanthanum (La), caesium (Cs), dysprosium (Dy), europium (Eu), and the rare earth element of gadolinium (Gd); With nonmetalloid such as N (nitride) and P (phosphorus).
In addition, in this fullerene thin film, the spin orientation of included paramagnetic material 24b is at random.So this fullerene thin film has stable paramagnetism.And the electron spin in fullerene 24a is the quantization state in pseudo-zero dimensional space.So in fullerene thin film, the relaxation time of spin becomes long, in other words, the coherence length of spin is elongated.As a result, when electronics conducted by fullerene 24a, spin will never be scattered.For example, when electronics during in the conduction of as shown in the figure longitudinal direction, electronics can be conducted when keeping the spin polarization degree.
In this embodiment, as shown in Figure 2, the direction of magnetization of ferromagnetic fixed layer 23 is to be fixed on direction of magnetization S 1On.Simultaneously, the direction of magnetization of ferromagnetic free layer 25 is two stable direction of magnetization S 1And S 2In one, be S for example 2In ferromagnetic free layer 25, when fashionable the spinning polarized electron streamer, the direction of magnetization is rotated.Two direction of magnetizations of ferromagnetic free layer 25 are corresponding to two types recorded information in memory cell 20.This recorded information of two types is read out as signal " 1 " and " 0 ".In Fig. 2, direction of magnetization S 1And S 2By the paintings orthogonal axis.
In this embodiment, the ferromagnetic material below adopting selectively, so that ferromagnetic fixed layer 23 has different functions each other with ferromagnetic free layer 25.
Simple material:
(110) direction bcc (body-centered cubic) Fe
(001) direction bce Fe
The C axle is direction hcp (hexagonal closs packing) Co planar
(111) direction fcc Co
(110) direction Fcc Co
(001) direction fcc Co
Bianry alloy:
Fe 1-xCo x(0＜x＜1) *
Ni xFe 1-x(0＜x＜0.75)
Ni 79Fe 21(permalloy)
Ternary alloy three-partalloy:
MnFeCo
FeCoNi
Select the ferromagnetic material of front herein, according to following conditions.For example, when ferromagnetic fixed layer 23 adopts identical ferromagnetic material with ferromagnetic free layer 25, can form ferromagnetic fixed layer 23 thicklyer than ferromagnetic free layer 25.When as the material of ferromagnetic fixed layer 23 when having any different as the material of ferromagnetic free layer 25, the selection of being done is to make the material of purposes ferromagnetic fixed layer 23, compares with the material as ferromagnetic free layer 25, has bigger gilbert attenuation coefficient.
In addition, when ferromagnetic fixed layer 23 had different current polarizing efficient each other as the layers of material of ferromagnetic free layer 25, then can be this thing of different values at required write current from the writing of recorded information " 0 " to " 1 " or from " 1 " to " 0 " each other with the write time became possibility.In the circuit of constructing, be favourable if having the write current of antisymmetry hypothesis, for example, when memory cell all on chip 20 is eliminated simultaneously, can select to reduce the polarization of the required electric current in every unit.
In addition, as mentioned above, because ferromagnetic free layer 25 has two stable magnetization direction, be important so ferromagnetic free layer 25 has uniaxial anisotropy in this layer.In other words, ferromagnetic free layer 25 must have and have＞the magnetic field H u of the uniaxial anisotropy of 100Oe (oersted), and it is not to be heated or influence that magnetic field rises and falls.In addition, the uniaxial anisotropy of ferromagnetic fixed layer 23 must be greater than the uniaxial anisotropy of ferromagnetic free layer 25.When having ferromagnetic material that magnetic field H u has a little uniaxial anisotropy, be easy to change at S as ferromagnetic free layer 25 1And S 2Between the direction of magnetization.But, be used for the meticulous experiment condition of CCP voltage measurement needs of this system.In other words, have the memory cell that the material of little uniaxial anisotropy makes and be not suitable for by having magnetic field H u as practical device.This uniaxial anisotropy can be by the component of control ferromagnetic material, shape, and crystal orientation, and lattice strain, or obtain by added magnetic field in forming these thin layers.More precisely, as ferromagnetic thin film, can enumerate following situation with uniaxial anisotropy:
For example, by magnetic anisotropy decision, magnetic field H u with high polarization and high uniaxial anisotropy is arranged along (110) mask of the magnetized bcc structural iron of magnetisable direction of principal axis.In addition, for example, has magnetic field H u with best polarization efficiency and little uniaxial anisotropy at the permalloy that has deposit and possess the magnetic anisotropy that the single shaft that is parallel to magnetic field inducts of bias magnetic field.In addition, for example, comprise the high polarization efficiency of hcp cobalt tool of uniaxial anisotropy and the magnetic field H u of high uniaxial anisotropy in the direction in c one axial plane.In addition, the Fe that has the bcc structure 1-xCo xAlloy passes through, and for example, the Co with X% on the lattice point position of Fe replaces, and has the pellicular front of their (110), and＜100〉direction have magnetizable axle with the uniaxial magnetic anisotropy in the plane.This Fe 1-xCo xAlloy has the magnetic field H u with maximum polarization efficiency and big uniaxial anisotropy.
In addition, when in the layer plane of ferromagnetic free layer 25, changing the direction of magnetization, might be the slenderness ratio of 1 μ m or littler rectangle by selecting its minor face, Hu becomes optimization anisotropy field.Simultaneously, when changing the direction of magnetization in the plane of ferromagnetic free layer 25 and between perpendicular to the direction in this plane, preferably the thickness of ferromagnetic free layer 25 is 5 atomic layers or still less, so that obtain sufficient longitudinal flux anisotropy.In other words, preferably, the thickness of ferromagnetic free layer 25 is about 1nm.This thickness is to become perpendicular to the transition region between the situation in this cheek in the situation and the direction of magnetization that the direction of magnetization becomes direction planar.In addition, as the polarized electron source that is used for ferromagnetic fixed layer 23 and ferromagnetic free layer 25, can adopt whistle to disturb (whistler) alloy such as PtMnSb or metalloid material.
Then, will the memory element MM1 with this structure be discussed hereinafter.In memory element MM1, the direction of magnetization of ferromagnetic fixed layer 23 is fixed to given S 1Direction.Simultaneously, ferromagnetic free layer 25 has two stable direction of magnetization S 1And S 2, and be located in a direction (S in addition, in these two magnetic directions 2).In such memory element MM1, two direction of magnetizations of ferromagnetic free layer 25, in each memory cell 20 corresponding to two recorded informations.Recorded information " 1 " or " 0 " are written into by the electron stream of spin polarization being injected into ferromagnetic free layer 25 and changing the direction of magnetization.Simultaneously, reading this recorded information is to realize by longitudinally apply the giant magnetoresistance effect (GMR) that electric current produces on memory cell 20.
When recorded information is written into, adopts pulse current so that change the direction of magnetization of ferromagnetic free layer 25, and finish the magnetic conversion (magnetic inversion) of ferromagnetic free layer 25.For example, be under the parallel magnetic situation of aiming at (Fig. 4 A) at initial state, write following finishing.In other words, have and electronics particle density pulse J in the spin of the spin equidirectional of ferromagnetic free layer 25 pFlow to ferromagnetic fixed layer 23 from ferromagnetic free layer 25.Then, ferromagnetic fixed layer 23 just with electronics particle density pulse J pSpin state in the identical direction.So, be injected into electronics particle density pulse J in the ferromagnetic fixed layer 23 pSpin be inverted according to Pauli's exclusion principle.Electron stream with this counter-rotating spin is at electronics particle density pulse J pRightabout flow as current density pulse Je (switching current I), so the spin direction of ferromagnetic free layer 25 is inverted.Shown in Fig. 4 B, in a bonding land, switching current I is greater than critical value Jt (A), and pulse then maintains in the unit of several nanoseconds.
As mentioned above, the direction of magnetization of ferromagnetic free layer 25 is converted the electric current I counter-rotating, and it is opposite with the direction of ferromagnetic fixed layer 23 that the direction of magnetization of ferromagnetic free layer 25 becomes, and it becomes the state (Fig. 4 C) that antiparallel magnetization is aimed at.Thus, write end.The direction of magnetization that " parallel magnetization is aimed at " refers to ferromagnetic free layer 25 and ferromagnetic fixed layer 23 is identical.In addition, " antiparallel magnetization aligning " to refer to the direction of magnetization of ferromagnetic free layer 25 and ferromagnetic fixed layer 23 be opposite.
In addition, in writing situation about being done, when, for example, when initial state is antiparallel magnetization aligning (Fig. 5 A), electronics particle density pulse J pWith current density pulse J eFlow direction separately become reciprocal.Electronics particle density pulse J pFlow to ferromagnetic free layer 25 from ferromagnetic fixed layer 23, and electron density pulse Je (switching current I) is at electronics particle density pulse J pRightabout flow, thus, write beginning.In other words, has the electronics particle density pulse J that spins with spin equidirectional in ferromagnetic fixed layer 23 pFlow to ferromagnetic free layer 25 from ferromagnetic fixed layer 23.
Then, the spin that its direction is different with the spin in ferromagnetic free layer 23 is injected into ferromagnetic free layer 23.The spin that the spin of ferromagnetic free layer 23 is injected into is reversed, and is inverted.Electric current with this counter-rotating spin with electronics particle density pulse J pOpposite direction flows as current density pulse Je (switching current I).Shown in Fig. 5 B, in the bonding land.Switching current I is greater than critical current Jt (A), and pulse still maintains the unit of several nanoseconds.As mentioned above, the direction of magnetization of ferromagnetic free layer 25 is converted electric current I counter-rotating, and the direction of magnetization of ferromagnetic free layer 25 becomes the same with ferromagnetic fixed layer 23, and it becomes the state (Fig. 5 C) of parallel magnetization aligning.Thus, write end.
Simultaneously, when recorded information is read out, for example, disposes setting among the CPP that in memory cell 20, applies longitudinal current, and utilize giant magnetoresistance effect.For example, under the situation of parallel magnetization alignment (Fig. 6 A), when applying critical value Jt or littler read current pulse, can obtain low voltage pulse V corresponding to logical zero LIW(Fig. 6 B).In addition, for example, under the situation of antiparallel magnetization alignment (Fig. 7 A), when applying critical value Jt or littler read current pulse, can obtain high voltage pulse V corresponding to logical one High(Fig. 7 B).
When adopting so a kind of reading method, in order to obtain, for example, 5% or more GMR during than (Δ R/R), preferably, constitute thin layer separately, ferromagnetic fixed layer 23 and ferromagnetic free layer 25, the electronic polarization Pol of material 1And Pol 2, the mathematical formulae 1 below satisfying.
(mathematical formulae 1)
∂ · P o l 1 · P o l 2 1 - P o l 1 · P o l 2 > 0.3
As the addressing scheme that is used for a kind of like this memory element MM1, used the simplest method.For example, as shown in Figure 8, can exemplify a kind of method, therein a usefulness that only writes wiring 41 for a memory cell 20.In addition, for example, as shown in Figure 9, can exemplify a kind of so-called xy addressing scheme, wherein wiring 42 and 43 is assembled into wiring 42 and 43 is intersected, memory cell 20 is configured in the joining of these wiring 42 and 43, and make addressing by the sets of signals of butted line 42 and 43 is incompatible.
Under situation, be used for the required leads of a memory cell 20 and connect and be in a place of electrode layer 22 and make, and finish the measurement of pseudo-4 end points in two places of electrode 26 with addressing scheme of only writing wiring 41.Under some occasion, the measurement of finishing two-end-point is enough, and wherein the lead connection is made in a place in electrode layer 22 and 26 respectively.
Under the situation of xy addressing scheme, only when pulse is added to these two wiring 43 of x and y and 44 simultaneously, just apply electric current above critical current, thus, memory cell 20 is chosen.Then, might one in x wiring and the y wiring (for example, the x wiring) be given a long pulse, and give another wiring (y wiring) short pulse in order to guarantee to finish therein the correspondence of pulse in the memory cell 20 that writes.
Then, with reference to Figure 10 to 16, will be described below the method for the memory element MM1 that makes the front.Figure 10 is the vertical view of Figure 11 A; Figure 13 is the vertical view of Figure 12; And Figure 16 is the vertical view of Figure 15 c.
At first, shown in Figure 10 and 11A, prepared by, for example silicon substrate 21 of making.Substrate 21 and need not mixing prepares, and, for example, overall diameter be 4 inches and thick be 0.01 inch.In addition, because nicking goes out the formation district of electrode 22 in step subsequently, so with spark point nicking substrate 21.After a surface of polishing substrate 21, flushing substrate 21 is also made oxidation processes.Then, usefulness, for example, sedimentation substrate 21 (for example, be of a size of in the plane of 2cm * 2cm) near the zone the central authorities deposition by, for example, the electrode layer of making entirely 22.The thickness of electrode layer 22 is set to, for example, and 0.5 μ m.
Then, shown in Figure 11 B, for example, use photoetching process, forming thick on electrode layer 22 is 50nm or thicker film against corrosion 31.Then, make the figure of resist film 31 according to the shape of memory cell 20.
Subsequently, shown in Figure 11 C, by, for example, it is Ni that sedimentation deposits by having component 81Fe 19The ferromagnetic fixed layer 23 made of perm gold.The thickness of ferromagnetic fixed layer 23 is set to, for example, and 4nm.In addition, when deposition ferromagnetic fixed layer 23, when applying the magnetic field of 100De, generate uniaxial anisotropy.
Then, by, for example, plasma-deposited method deposit by, for example, comprise the C of La 82(La @C 82) make thick in the spin conducting shell 24 of 20nm.C 82Have, for example, the La that is of a size of the aperture from 01nm to 50nm is included in this aperture.Then, the single shaft of ferromagnetic fixed layer 23 is held constant to anisotropy.More specifically, in plasma-deposited method, for example adopted the plasma polymerization equipment (for example, criticizing the patent application issue) that the combined one-tenth parallel plate electrode of external electrode ability ability is combined with reference to the H08-59220 Japanese unexamined.This plasma polymerization equipment is equipped with the molybdenum boat that is connected to the plasma power source in reactive tank.C 82Powder be contained in this molybdenum boat, the substrate 21 that deposits ferromagnetic fixed layer 23 thereon is arranged on the position of the molybdenum boat in reactive tank.
By using this plasma polymerization equipment, and the plasma energy is set to, for example, AC 13.56MHz and output to 150W produces the cation plasma of La, the C in molybdenum boat in the system of steady flow 82Powder is distilled in several Baidu, and by La C 82The spin conducting shell of making 24 is deposited on the ferromagnetic fixed layer 23 of substrate 21.In this embodiment, spin passes layer by layer 24 by comprising paramagnetic material (for example, La @ C 82) fullerene deposit.So, the uniform thin layer of might growing, and the coherence length of control spin.
Then, by, for example, sedimentation is deposition on spin conducting shell 24, for example, makes the thick ferromagnetic free layer 25 of 1nm that is by permalloy.Then,, apply the magnetic field that is similar to deposited iron magnetosphere 23 simultaneously by finishing deposition, the uniaxial anisotropy of in ferromagnetic free layer 25, inducting, so that the C axle of ferromagnetic free layer 25 becomes the magnetization that is parallel to ferromagnetic fixed layer 23.Thus, ferromagnetic free layer 25 has two stable direction of magnetization S 1And S 2, and be positioned this two direction of magnetization S 1And S 2In a direction.
Subsequently, deposit by for example by sedimentation, gold is made thickly is the electrode layer 26 of 25nm.Then, shown in Figure 12 and 13, by dissolving and remove film 31 against corrosion and finish and peel off.Form memory cell part 32a and earth terminal part 32b thus selectively.
Then, shown in Figure 14 A, form in substrate 21 by, polymethyl methacrylate and make, for example, thick be the insulating barrier 33 of 60nm, with covering memory cell part 32a and earth terminal part 32b.Insulating barrier 33 plays a part planarization films.Then, as shown in Figure 14B, by, for example, the oxygen plasma etch exposes to the open air the end face of memory cell part 32a and earth terminal part 32b out.
Subsequently, form resist film 34 shown in Figure 14 C selectively.Resist 34 has the figure that covers earth terminal part 32b and expose storage area 32a to the open air.The thickness setting of resist film 34 is arrived, for example, 0.2 μ m.Then, shown in Figure 15 A, the deposition by, for example, the metal 35 that Au makes is to cover film 34 against corrosion.
Subsequently, shown in Figure 15 B, by dissolving with remove film 34 against corrosion and finish and peel off, and remove metal 35 selectively.Metal 35 becomes electrically contacting of memory cell 20 and is electrically connected with electrode layer 26.When film against corrosion 34 dissolvings with when mobile, just earth terminal part 32b is exposed to the open air out.But earth terminal part 32b is electrically connected to another electrode layer 22.
Then, shown in Figure 15 C, by pressure welding the hunting 36 that is used for voltage signal and 37 and the lead 38 and 39 that is used for current impulse be connected to these and electrically contact (earth terminal part 32b and metal 35).At last, the substrate 21 that forms memory cell 20 thereon is fixedly secured on the radiator (not shown) of being made by copper (Cu).Thus, finished memory element MM1.
In the memory element MM1 that as above constructs, two direction of magnetization S of ferromagnetic free layer 25 1And S 2Corresponding to two recorded informations in each memory cell 20.By spin polarized current being injected into ferromagnetic free layer 25, and the conversion direction of magnetization, just finish writing " 1 " or " 0 ".
Then, the electron stream of spin polarization flow through the spin conducting shell 24.In this embodiment, spin passes layer 24 and makes (Fig. 3) by fullerene thin film.In this fullerene thin film, the spin orientation of included paramagnetic material 24b is at random.So this fullerene thin film has stable paramagnetic characteristic.And the electron spin in fullerene thin film is to be in quantized state in pseudo-zero dimensional space.In addition, by construct spin conducting shell 24 by fullerene thin film, can easily finish the coherence length of uniform film of growth and control spin.Thus, in spin conducting shell 24, can obtain enough spin coherence lengths and uniformly from curl field, and can prevent the scattering of spinning.In other words, electronics conducts by spin conducting shell 24, and still keeps its spin polarization degree.
As mentioned above, in this embodiment, spin conducting shell 24 has the aperture that is of a size of from 0.1nm to 50nm, and is made by the fullerene that comprises paramagnetic material in this aperture.So it becomes and is easy to grow the coherence length of uniform film and control spin, and can obtain enough spin coherence lengths and uniformly from curl field.So, its scattering of the conduction electron that might prevent spin polarization that becomes, and improve reliability.Thus, can drop into practical application to spin injection type memory element MM1.Especially, when the field type of inducting with routine is made comparisons, the upper limit of the packing density that can be greatly improved, and can reduce readout time and power consumption.
Reference example is described the present invention.But the present invention is not limited to the embodiment of front, and can make various modifications.For example, for the fixing given direction of the direction of magnetization to of ferromagnetic fixed layer 23, might on ferromagnetic fixed layer 23, form by, for example, the ferromagnetic fixed layer 51 (with reference to Figure 17) that antiferromagnet is made.As a kind of antiferromagnet, can exemplify FeMn, IrMn, NiMn, RhMn, CrMnPt, the material of FeMnPt and the like.In the material of front, even because NiMn at high temperature (for example 650De is until T=450k) still can obtain big pinning (pinning), so NiMn suits.
The magnetic moment of ferromagnetic fixed layer 23 is lockable by such magnetization fixed layer 51, and its direction of magnetization is fixed to the given direction of magnetization.When magnetization fixed layer 51 when making as the metal of antiferromagnet, magnetization fixed layer 51 also can play a part electrode.In addition,, be used for a kind of method of read-out recording information among the embodiment in front, for example, can utilize the magnetic Kerr effect that produces when illuminating ferromagnetic free layer 25 when using up though utilize the GMR effect.
In addition, as shown in figure 18, except that the spin conducting shell 24 of front, can prepare the spin array layer 52 that comprises low magnetic alloy.This low magnetic alloy is a kind of the metal-doped a kind of alloy in semiconductor of magnetic material.On the joint interface between the low magnetic material, keeping semi-conductive characteristic therein and existing magnetic order.And feeromagnetic metal, magnetization becomes non-equilibrium, and can produce the electronics (source: R.Fiederling of spin polarization, M.Keim, G.Reuscher, W.Ossau G.Schemidt, A.WAAG T L.WMolenkamp, Nature 402,787-790 (1999), " Injection and detection of aspin-poiarized current in a light-emi lting diode ").
So, adopt this low magnetic alloy can obtain higher spin polarization degree as spin array layer 52, this spin array layer also has the function as the spin conducting shell.
Can exemplify, for example, (In, Mn) As, (Ga, Mn) As, (Cd, Mn) Te, (Zn, Mn) Te, and (Zn, Cr) Te is as low magnetic material alloy.
The position that comprises the spin array layer 52 of low magnetic alloy is quite general between two-layer ferromagnetic thin layer (ferromagnetic fixed layer 23 and ferromagnetic free layer 25).But conduction spin polarization degree in the spin injection and can be improved more preferably between the original position and spin conducting shell (spin conducting shell 24) of ferromagnetic fixed layer 23 thus in the position of spin array layer 52 that comprises low magnetic alloy.
When low magnetic alloy was included in the fullerene that is contained in spin conducting shell 24, spin conducting shell 24 played the function of spin array layer and spin conducting shell.
In addition, for to transport other circuit with according to recorded information read as a result the completion logic operation, for example, the permanent RAM that can be attached to the front to the amplifying circuit of read output signal is possible.In addition, though among the embodiment in front, electrode layer 22, ferromagnetic fixed layer 23, spin conducting shell 24, ferromagnetic free layer 25, and electrode layer 26 is to be formed in this order in the substrate 21, the sedimentary sequence of relevant each layer can with the order of front be opposite,
[example]
In this example, made permanent RAM with following array structure.In addition, will the structure of electrode 26 to substrate 21 be shown.
＜sample structure 〉
Electrode layer: Au film (25nm is thick)
Ferromagnetic free layer: by Ni 81Fe 19Permalloy film (the 1nm that makes
Thick, and have uniaxial anisotropy, so that the C axle
Become the magnetization that is parallel to ferromagnetic fixed layer)
Paramagnetic layer: La @ C 82Film (20nm is thick)
Ferromagnetic fixed layer: by Ni 81Fe 19The permalloy of making (4nm is thick, and
Has uniaxial anisotropy)
Electrode layer: Au film (500nm is thick)
Substrate: silicon base
The measurement result of the sample structure of this example will be shown hereinafter.
＜calculated value 〉
Polarization efficiency: reach 90%
Effective each Hu=+2Ku/Ms in the plane of ferromagnetic free layer is reached 10Oe
Anisotropy magnetic field:
Spin population density: reach 1.9 * 10 15Cm 2
Lucky attenuation coefficient: 0.005
Critical value Jt: reach 8 * 10 3A/cm 2
Resistance: 16m Ω
Noise voltage (10Hz BW, 77k): 0.2nV
＜measured value 〉
By testing the switching current density of coming: reach 2 * 10 4A/cm 2
θ change-over time (0 to π): reach 0.05 μ sec
Peak power consumption in reading: reach 0.1pW
Read current density: reach 3 * 10 4A/cm 2
Read current pulse: reach 5.0 μ A, 1Hz
CPP GMR4% Δ R/R: reach (800 μ Ω/20m Ω)
Average read-out voltage: reach 5nV
In addition, as the comparative example to this example, for the Au film of 20nm is used as the paramagnetic layer, other is the same with this example has made permanent RAM, and the measurement result of this comparative example will be shown hereinafter except thick.
＜calculated value 〉
Polarization efficiency: reach 30%
To in the free layer plane effectively each reaches 10Oe to different Hu=+2Ku/Ms
Property magnetic field:
Spin population density reaches 1.9 * 10 15Cm 2
Gilbert attenuation coefficient: 0.01
Critical value Jt: reach 8 * 10 3A/cm 2
Resistance: 16m Ω
Noise voltage (10Hz BW, 77K): reach 0.3nV
＜measured value 〉
The switching current density that obtains by experiment: reach 2 * 10 4A/cm 2
θ change-over time (o-π): reach 0.1 μ Sec
Peak power consumption in reading: reach 0.1pw
Read current density reaches 4 * 10 3A/cm 2
The read current pulse reaches 6.4 μ A, 1Hz
CPP GMR 4% Δ R/R: reach (800 μ Ω/16m Ω)
Average read-out voltage: reach 5nV
Prove as the front, in this example, by adopting La @ C 82Film is used for the paramagnetic layer and replaces the Au film, can improve polarization efficiency significantly.In other words, found as La @ C 82When film replaces the Au film as the paramagnetic layer, can improve the performance of permanent RAM.
In addition, as comparative example, the measurement structure of conventional induced magnetism type memory element will be shown hereinafter to this example.
＜measured value 〉
Switching current density: reach 5.8 * 10 6A/cm 2
θ change-over time (o-π): reach 0.08 μ Sec
Peak power consumption in reading: reach 1.0pw
Read current density reaches 1 * 10 5A/cm 2
The read current pulse reaches 5.0 μ A, 1Hz
CPP GMR 4% Δ R/R: reach (800 μ Ω/20m Ω)
Average read-out voltage: reach 4nV
Compare with conventional induced magnetism field pattern memory element, the related characteristics that is enhanced is as follows: being used to change as writing required electric current increases the magnitude of two unitss; Increase the magnitude of a units change-over time; And power consumption increases the magnitude of a units.In other words, found to compare with conventional induced magnetism field pattern memory element, spin injection type memory element can reduce readout time and power consumption.
Then, another embodiment of the present invention will be described.
(second embodiment)
Figure 19 illustrates the structure according to second embodiment of the invention.This memory element MM2 also is " a spin injection type ", and wherein writing is to produce magnetization inversion by the spinning electron by injecting and polarizing to realize.Its basic structure is at two-layer ferromagnetic thin layer, and promptly in fixed bed 1, its magnetization orientation is to be fixed on certain direction, and in free layer 2, and its magnetization orientation is that the spinning electron by injecting and polarizing changes, between make spin and pass layer by layer 3.
These relevant thin layers are the thin layers of inside that are formed at the carbon nano-tube 10 of a molecule.In other words, carbon nano-tube 10 is crossed at the axial setting middle body to spin conducting shell 3, and comprises that at two end fixed bed 1 and free layer 2 constitute a component units of memory.In addition, fixed bed 1 and free layer 2 are equipped with electrode layer 4A and 4B respectively.Individual other magnetic memory element MM2 is connected to wiring layer 5A and 5B by electrode layer 4A and 4B.
Make spin conducting shell 3 by a part of structure in the carbon nano-tube 10 of hollow.Constitute spin conducting shell 3 with the magnetic interaction of shielding between fixed bed 1 and free layer 2 by nonmagnetic substance.In addition, the spin coherence length of spin conducting shell 3 should be greater than the thickness of one deck at least of itself, so as between fixed bed 1 and free layer 2 spinning electron of conduction polarization.About carbon nano-tube, the various reports of the impact conduction that proposes it have been made.Recently, rich experimentally its spin coherence length of confirmation is 200nm or more (K.Tsukagoshi, B.W.Alphenaar and H.Ago, " Spin coherent transport ina ferromagnetically cmtacted carbon nanotube; " Nature 401,572-574 (1999)).Simultaneously, the thickness of the spin conducting shell 3 here (length of carbon nano-tube) be as usage range approximately from 0.5nm to 5 μ m.So spin conducting shell 3 satisfies two conditions of front simultaneously.
As mentioned above, in this embodiment, (1) utilizes the part in the carbon nano-tube 10 to pass layer 3 as spin, and (2) carbon nano-tube 10 constitutes the shell of whole element.
In No. 2546114 Japan Patent issue, disclosed the technology that in the aperture of a hollow that is arranged at carbon nano-tube central authorities, comprises various different materials.About comprising the carbon nano-tube of magnetic material, provided following description: (1) since the internal diameter of pipe (5 to 10nm) less than the domain size of magnetic material usually, such carbon nano-tube is considered to a simple magnetic domain particle, and (2) are when arranging pipe like this, so that their major axis is set longitudinally, because anisotropy can realize having very highdensity perpendicular magnetic recording medium.But, in No. 2546114 Japan Patent issue in front, be not applied to the description of memory about the carbon mitron.
The most important significance that shell obtained that is used as element from carbon nano-tube 10 is to prevent owing to the influence of the magnetic screening effect that is gone by its pi-electron to contiguous magnetic field, its inside.The magnetic memory element MM2 of present embodiment shows out its feature by current drive-type.But,, may disturb the magnetization of adjacent unit by the leakage field of read current generation if its size (cell size) becomes nanoscale.But, because magnetic nanotube 10 has covered magnetosphere at element internal, and from exterior shield magnetic disturbance.So, always stably keeping the direction of magnetization of fixed bed 1 and free layer 2.Thus, magnetic memory element MM2 becomes element fine size, that can be integrated and drive in practicality.
In addition, the interior diameter of carbon nano-tube 10 is very little, is about from 1 to 10nm.In other words, meticulous like this element can form under the situation that does not rely on conventional semiconductor process techniques.Simultaneously, its size is significantly less than the common domain size of magnetic material.So, can imagine to have a simple domain structure in the inside of carbon nano-tube 10.As a result, owing to do not follow magnetic domain to transport to magnetized, so the retentivity expectation of magnetic material can become bigger.
The example that is used as the ferromagnetic material of fixed bed 1 and free layer 2 comprises the simple material of Fe and Co, its binary alloy, NiFe alloy, MnFeCo and FeCoNi.In each example of front, effectively the ferromagnetic material of the high polarization of electron gain is the FeCo alloy with high Fe content rate.The repetition d electronics of 3d ferromagnetic material has isotropic wave vector as the free electron state.So, necessary would rather not consideration crystal orientation.Preferably, fixed bed 1 optional self-contained Ni, the hard magnetic material of Co and element like that, and free layer 2 can be selected from such as pure iron and permalloy (Ni 79Fe 21) soft magnetic material.In addition, can adopt such as its main component is the spinelle type gas magnetic particle that contains the iron oxide of cobalt nickel, and its high-remanece is in just being known crystal grain diameter recently:  reaches 30nm, coercive force: HcJ reaches 6k Oe), and FeO 2The metal nano particle material of particle ( reaches 5nm for ignition temperature 023k, crystal grain diameter, and HcJ reaches 1K Oe).
To fixed bed 1, for the direction of magnetization that remains unchanged, preferably adopt its gilbert attenuation factor, or the component by regulating it and its thickness (thicker than free layer 2) apply the uniaxial anisotropy greater than free layer 2 significantly greater than the material of free layer 2.In addition, might contact inverse ferric magnetosphere with fixed bed 1 to pin magnetization.When this inverse ferric magnetosphere was made by metal, inverse ferric magnetosphere also had the function of electrode layer 4A.The example of this antiferromagnetic metal material comprises FeMn, IrMn, NiMn and RhMn.
Simultaneously, fluctuating for the direction of magnetization (storage attitude) that prevents to cause owing to heating or influence of magnetic field, preferably, by making its component, thickness, the parameter of cross-sectional area (diameter of carbon nano-tube 10) and the like becomes the most appropriate uniaxial anisotropy that free layer 2 has anisotropic magnetic field H u＞100Oe for preparing.Planar change the direction of magnetization of free layer 2 on the both direction, or direction that can be planar and be changed perpendicular to the direction on this plane.In the latter case, preferably, the thickness of free layer 2 is 5 atomic layers or still less, and in other words, about 1nm obtains enough perpendicular magnetic anisotropics with example.
Can adopt the electrode layer 4A and the 4B of any kind, as long as electrode layer 4A and 4B are made by the paramagnetic metal with conductivity.And not to its thickness and the special in addition restriction of shape.This magnetic memory element MM2 is included in the shell of carbon nano-tube.The size of magnetic memory element MM2 is less than common memory element, and its thickness is than the cross section that then is higher than it.So, can adopt conventional semiconductor process techniques to form electrode layer 4A, 4B and wiring layer 5A and 5B, or can come structure to do by molecular wire such as carbon nano-tube.
In magnetic memory apparatus MM2,, write and read the two and all realize by applying electric current as describing after a while.So the wiring that can sharedly write and read is enough and use two-layer wiring layer 5A and 5B.Write structure is so simply to be a advantage in its all advantage.
In addition, in magnetic memory element MM2, magnetic nanotube 10 is used as the shell of element.So magnetic memory element MM2 is also shown out its feature by integral body.In general, carbon nano-tube forms the conglomerate that is called a bundle easily.The shell of magnetic memory element MM2 is made of carbon nano-tube 10.So, by the close poly-integral body of making easily.For example, as shown in figure 20, when magnetic memory element MM2 was arranged in the state of square formation, this well-regulated arrangement was kept by dispersion force (power that is used for close dimerization carbon nano-tube 10), and the memory bank of magnetic memory apparatus is by becoming whole magnetic cell MM2 to constitute.Thus, the storage device that can to make its unit storage unit be a carbon nano-tube, have high density and high reliability.
Can pass through, for example, through adopting directed carbon nanotube production process (Jeong et al., Chem.Mater., Vol 14, No.4 pp1859-1862 (2002)), inserts magnetic metal, and finish the electricity joint in the end and make this magnetic memory element MM2 and magnetic memory apparatus thereof to produce an oriented carbon nano-tube at the hollow space of this pipe.To provide special description after a while as this method of example.
Then, hereinafter its method of operation will be described.In magnetic memory element MM2, information is to be that the state aiming at of parallel magnetization and the direction of magnetization of 2 pairs of fixed beds 1 of free layer are the states that antiparallel magnetization is aimed at by the direction of magnetization that causes 2 pairs of fixed beds 1 of free layer, and they write down corresponding to two data such as " 0 " and " 1 ".Data are to write by the direction of magnetization by the current reversal free layer 2 that is added to the direction (CPP: current vertical is in the plane) perpendicular to lamina plane.For example, aim at from parallel magnetization when the magnetization of 2 pairs of fixed beds 1 of free layer and to change to antiparallel magnetization on time, the current density pulse is added to free layer 2 from fixed bed 1, and spinning polarized electron is injected into fixed bed 1. then from free layer 2, must in free layer 2, produce magnetic inversion greater than the electric current of critical current density value with its amplitude.During the applying of this pulse,, and the state that the parallel magnetization of free layer 2 and fixed bed 1 is aimed at is changed into the state of its antiparallel magnetization aligning the counter-rotating of the direction of magnetization of free layer 2.
In contrast, when the state of antiparallel magnetization aligning is changed into the state of parallel magnetization aligning, apply electric current in opposite direction.In other words, electric current is added to fixed bed 1 from free layer 2, and spinning polarized electron is injected into free layer 2 from fixed bed 1.
In addition, because spin conducting shell 3 is made of carbon nano-tube, so polarized electron conducts by this layer under the situation of spin relaxation not having.So electronics is injected in the fixed bed 1, and free layer 2 is in the maintained state of their spin angular momentaum, reads so can finish effectively.
Sense data, in other words, by adopting, for example, (CPP-GMR: giant magnetoresistance effect giant magnetoresistance) can be finished two magnetized states of identification front in the direction perpendicular to aspect.In addition, a kind of method that adopts the magnetic Kerr effect is arranged.
As mentioned above, spin injection type magnetic memory element MM2 at this embodiment, two ferromagnetic layers, in other words, two ends at a molecular carbon nanotube 10, stop up fixed bed 1 and free layer 2 respectively, so and it is the hollow space of the central authorities conducting shell 3. that is set to spin itself, the spin coherence that spin conducting shell 3 has good carbon nano-tube.Polarized electron is not having to inject fixed bed 1 under the situation of spin relaxation as free layer 2.So, can finish writing effectively, and can realize that low-power consumption drives.
And the main body of memory element is the enclosure that is contained in carbon nano-tube 10.So, under the situation that does not rely on conventional micro-fabrication technology, can realize the element of nano-scale.So,, might obtain very highdensity storage device by adopting this magnetic memory element MM2.If like this, can imagine that fixed bed 1 and free layer 2 have single domain structure, and can keep stable magnetization orientation.In addition, can always stably keep this magnetization orientation also is that promptly the pi-electron of carbon nano-tube 10 removes to be covered with fixed bed 1 and free layer 2, and magnetic disturbance from exterior shield owing to this fact.In addition, carbon nano-tube 10 has the shape of one dimension and the dispersion force that works between pipe.So, realized close poly-in this direction.As a result, can be stably and high orientation magnetic memory element MM2 easily, and can obtain the magnetic memory apparatus of height combination.
In addition, except the spin of front passes layer by layer 3,, the thin layer 11 of lining up the spin array that comprises the low magnetic alloy the same with first embodiment can obtain higher spin polarization degree by being provided.The position of lining up the thin layer 11 of spin array is quite general between two ferromagnetic layers (ferromagnetic fixed layer 1 and ferromagnetic free layer 2).But more preferably this position is between the original position and spin conducting shell 3 of ferromagnetic fixed layer 1.Thus, can improve in injection conduction spin polarization degree.
In addition, will describe special-purpose example of the present invention hereinafter in detail.
(example 1)
At first,, and wash high-purity aluminium flake (99.999%) degreasing with acetone with alcoholic solution.The aluminium flake electropolishing that in the mixed solution of perchloric acid and alcohol, will obtain at last.Subsequently, in the oxalic acid of 0.3M, use 40V, in the time of 150 ℃, it was carried out anodized 12 hours.Obtained to have the anodised alumina substrate of fine pores thus.These fine pores are gathered certainly as the loose structure of nano-scale magnitude, and form orderly array on distance.The actual fine pores that obtains is passed alumina substrate (in other words, fine pores is all to be in the state of opening in its two ends), and its diameter is that the density of 80 and it is 1/0 * 10 10Micropore/cm 2
Then, at CoSo 27H 2With the alumina base bottom sediments, and apply 18VAC1 minute in the solution of O.Thus, the Co catalyst is deposited on the fine pores bottom of substrate by electrochemical method.By from the teeth outwards Co particle being exposed to 10% H at 500 ℃ 2With in the mist of 90% Ar 1 hour and make its reduction.This Co catalyst is a kind of catalyst that is used for producing carbon nano-tube, and will become thin magnetic layer's (fixed bed) of magnetic memory element.
Then, 10% C 2H 2The Ar that covers carry in the gas, this is carried the alumina wafer that gas supplies to the front, be grown in the carbon nano-tube in the fine pores of substrate by thermolysis process.
By the sonicated of 40k Hz is provided, cut away the part of the extraneous growth of carbon nano-tube for whole substrate in acetone soln.Thus, obtained to have equal length, directed in the axial direction nanotube.
Then, the whole substrate that has carbon nano-tube immersed comprise iron ion as in the hypophosphites of reducing agent sour molten, and pure iron is received in the carbon nano-tube, till when adopting chemical plating method demonstration metal color.Thus, each other carbon nano-tube has obtained the basic structure of spin injection type magnetic memory element.In other words, formed hard magnetic material Co layer, as the hollow nanotube of spin conducting shell 3, as Fe layer as free layer as fixed bed.By Atomic Manipulation method (atom maniputation method) nanotube with thin diameter is comprised that at this place, two ends of nanotube of magnetic material is joined together as electrode and draws wiring.
In addition, the whole alumina substrate of these nanotubes is spread upon by SiO 2On the dielectric base of making, and immersed among 70 ℃ the NaOH of 0.1M 3 hours, alumina substrate is decomposed and removes thus.Then, the bundle structure that constitutes by the nanotube that comprises magnetic material and become electrode and the pipe of wiring is still stayed on this insulating barrier.
Then, the signal wiring is welded to the introducing wiring, this signal wiring comes address acquisition as the wiring of bidimensional lattice point.At last, this dielectric base is fixed firmly to copper radiator.Thus, finished magnetic memory apparatus.
In addition, measured the characteristic of the magnetic memory apparatus of made.Hereinafter the result will be shown.
＜calculated value 〉
Polarization efficiency: reach 50%
To in the free layer plane effectively each reaches 10Oe to different Hu=+2Ku/Ms
Property magnetic field:
Spin population density reaches 5.0 * 10 15Cm 2
Gilbert attenuation coefficient: 0.01
Critical value Jt: reach 8 * 10 3A/cm 2
Resistance: 16m Ω
Noise voltage (10Hz BW, 77K): reach 0.2nV
＜measured value 〉
The switching current density that obtains by experiment: reach 1 * 10 4A/cm 2
θ change-over time (o-π): reach 0.05 μ sec
Peak power consumption in reading: reach 0.1pw
Read current density reaches 3 * 10 3A/cm 2
The read current pulse reaches 6.4 μ A, 1Hz
CPP GMR 4% Δ R/R: reach (800 μ Ω/16m Ω)
Average read-out voltage: reach 5nV
Magnetic recording density: reach 6.5Gbit/inch 2
Can pass through the fine pores diameter of the anodised alumina substrate of control, and make the nanotube diameter, promptly the diameter of magnetic memory element is that optimum value is improved the packing density that records.By to the aluminium substrate of electropolishing by, for example, use Ar, the ion sputtering method of Ga and suchlike element is controlled the starting point of fine pores growth, might control the fine pores diameter tens in the scope of hundreds of nm.
(example 2)
By making be used for by arc discharge method and suchlike method synthetic contain metallic ferromagnetic graphite electrode, can obtain to comprise this metallic ferromagnetic carbon nano-tube.In this example, magnetic memory apparatus is by assembling with the carbon nano-tube of top the same acquisition.
At first, prepare a kind of mixture, in this mixture, Ni, the powder of Y and permalloy (NiFe alloy) is put into powdered graphite by weight 4%, 1% and 4%.In addition, carbon resin is joined in the mixture, this mixture be heated to 900 ℃ 6 hours.Under the He of 200Torr atmosphere, realize with the arc discharge that contacts the arc light method as cathode electrode by adopting this synthetic.
The carbon pipe that is obtained is dispersed in the magnetic field, and thus, the nanotube that comprises magnetic material is chosen out.Because Ni uses as the catalyst that is used to produce carbon nano-tube, so Ni is an end that is included in nearly all pipe.So, must choose the pipe of inserting permalloy at the other end out.Then, in the magnetic nanotube that is obtained by venerating with the scanning electron microscopy visual inspection comprising that at one end the ferromagnetic Ni and the other end comprise that the pipe of permalloy puts together.
In these carbon nano-tube that put together each all has the basic structure as spin injection type magnetic memory element.In other words, formed hard magnetic material Ni layer, as the hollow nanotube of spin conducting shell with as the permalloy layer of free layer as fixed bed.These carbon nano-tube are gathered so that the spacing of apart about 0.3nm is close by Van der Waals for.
By the Atomic Manipulation method nanotube with diameter is comprised that at this place, two ends of nanotube of magnetic material is joined together as electrode and seeks out wiring.After this, finish magnetic memory apparatus by the subsequent step that is similar to example 1.
The present invention is not limited to the embodiment and the example of front, can make various modifications.For example, in a second embodiment, the part in the spin conducting shell 3 of carbon nano-tube 10 is used as hollow space.But, might comprise conduction paramagnetic material with long spin coherence length, its example comprises the material with carbon element such as fullerene, is different from the 3d metal such as the antiferromagnetic metal of Ag and Au, and the 4d metal.
In a second embodiment, describe its major part and be formed at magnetic memory element in the carbon nano-tube 10.But, might carbon nano-tube 10 be used other cylindrical molecule to replace such as boron nitride (BN) pipe and peptide nanotube.If like this, might in the part of conducting shell 3 that is equivalent to spin, improve characteristic by material with carbon element or the metal of inserting the front.
In addition, in a second embodiment, carbon nano-tube 10 comprises fixed bed 1 and free layer 2, might carbon nano-tube 10 comprises the part among electrode layer 4A and the 4B, so that improve welding characteristic.Magnetic memory element in, the spin conducting shell that is provided with between fixed bed and free layer at least is to be quite general by the situation that the cylindrical molecule with carbon nano-tube feature constitutes.Whether comprise that other assembly that is used for element can select.But as above-mentioned, the cylindrical molecule of expectation conduction touches the generation magnetic screening effect, so as required, this structure that is included can preferentially be selected for use.
According to memory element of the present invention or storage device, the spin conducting shell is to be made of spherical molecule with aperture or cylindrical molecule.So it becomes and is easy to control spin coherence length, and can obtain enough spin coherence lengths and uniformly from curl field.So, might prevent the scattering of the spin polarization conduction electron in the paramagnetic layer, improving reliability, and obtain its actual use thus.In addition, compare, can improve the upper limit of packing density significantly, and can reduce readout time and power consumption with the magnetic field method of inducting of routine.Especially, by the spin conducting shell that forms by the spherical shell molecular material that the comprises paramagnetic material uniform film of can growing.
In addition, the spin conducting shell is made of cylindrical molecule, and this cylindrical molecule axially in middle body play the function of spin conducting shell.In addition, first ferromagnetic layer is an end that is included in this cylindrical molecule, and second ferromagnetic layer is to be included in its other end.Thus, obtained holding the structure of element body at the hollow space of this cylindrical molecule.So, under the situation that does not rely on conventional micro-fabrication technology,, can realize the injection type memory cell of nano-scale by selecting the cylindrical molecule of nano-scale.In other words, fine size that let it be can obtain the element that its size is thoroughly controlled by simple manufacturing method.If like this, can imagine that because the diameter dimension of cylindrical molecule, first and second ferromagnetic layers have simple domain structure.In addition, owing to these thin layers are included in the cylindrical molecule, from the magnetic disturbance conductively-closed of outside.So, can stably keep the direction of magnetization.Because magnetic screening effect, in fact fine size that let it be becomes and can realize integrated integral body.
In addition, by adopting carbon nano-tube, in this spin conducting shell as cylindrical molecule, polarized electron is conducted, and because the good spin of carbon nano-tube is relevant, it is weakened almost not spin, and polarized electron is injected in first ferromagnetic layer or second ferromagnetic layer.So, might realize having the spin injection type memory element of the nano-scale that well writes efficient.
In addition, according to storage device of the present invention, a plurality of memory elements of the present invention are arranged.So, can finish writing effectively, and can realize that low-power consumption drives.Especially, when adopting cylindrical molecule to constitute other memory element, can obtain columniform three-dimensional structure, it is different with the element that forms on bidimensional by conventional thin film fabrication technology.So, can play this memory element at longitudinal direction and assemble integral body.In addition, this memory element is a spin injection type memory element, compares with other magnetic memory, accepts the influence in contiguous magnetic field hardly.So, can further narrow down the distance between memory cell, and enable to realize the highdensity integral body that assembles.

Claims (36)

1. a memory element wherein writes recorded information by the electronics that injects spin polarization, comprising:
The spin conducting shell is made by spherical shell with hollow or cylindrical molecular material, and wherein
The electronics of spin polarization is by this spin conducting shell conduction.
2. according to the described memory element of claim 1, comprising:
First ferromagnetic layer, wherein a direction of magnetization is fixed;
The spin conducting shell is formed on above first ferromagnetic layer, is made by spherical shell with hollow or cylindrical molecular material, comprises paramagnetic material therein, and has given spin coherence length; And
Second ferromagnetic layer is formed on the spin conducting shell on one side of the first ferromagnetic layer opposite, wherein changes a direction of magnetization by spinning polarized electron, wherein
Write recorded information by the direction of magnetization that changes second ferromagnetic layer.
3. according to the described memory element of claim 2, it is characterized in that the spherical shell material that wherein constitutes the spin conducting shell is a carbon molecule fullerene.
4. according to the described memory element of claim 3, it is characterized in that wherein the spherical shell molecular material is the carbon molecule fullerene with the hollow size from 0.1nm to 50nm.
5. according to the described memory element of claim 2, it is characterized in that the thickness of the conducting shell that wherein spins is to 5 μ m from 0.5nm.
6. memory element according to claim 2 is characterized in that, is lanthanum (la), caesium (Cs) comprising the paramagnetic material in the spherical shell molecular material, dysprosium (Dy), europium (Eu), or gadolinium (Gd).
7. according to the described memory element of claim 2, it is characterized in that, is nitrogen (N) or phosphorus (P) comprising the paramagnetic material in the spherical shell molecular material.
8. according to the described memory element of claim 2, it is characterized in that, between first ferromagnetic layer and second ferromagnetic layer, comprise a spin alignment layer.
9. described according to Claim 8 memory element is characterized in that, wherein this spin alignment layer comprises low magnetic material.
10. according to the described memory element of claim 9, it is characterized in that, wherein should hang down the magnetic material by (In, Mn) As, (Ga, Mn) As, (Cd, Mn) Te, (Zn, Mn) Te and (Zn, Cr) at least a the making among the Te.
11., it is characterized in that wherein the spherical shell molecular material comprises low magnetic material according to the described memory element of claim 2, and this spin conducting shell also plays a part the spin alignment layer.
12., it is characterized in that wherein the thickness of first ferromagnetic layer is thicker than the thickness of second ferromagnetic layer according to the described memory element of claim 2.
13., it is characterized in that according to the described memory element of claim 2, comprise magnetization fixed layer, this magnetization fixed layer is used for fixing in the direction of magnetization of first ferromagnetic layer to first ferromagnetic layer of spin conducting shell opposite one side.
14., it is characterized in that wherein this magnetization fixed layer is to be made by antiferromagnet according to the described memory element of claim 13.
15., it is characterized in that wherein this magnetization fixed layer also plays a part electrode according to the described memory element of claim 13.
16., it is characterized in that wherein the thickness of second ferromagnetic layer is 5 atomic layers or still less according to the described memory element of claim 2.
17., it is characterized in that wherein electrode is formed respectively on two faces according to the described memory element of claim 2, and these two electrodes are made by the paramagnetic metal material.
18., it is characterized in that the writing line that wherein is used to inject spinning polarized electron is connected to second ferromagnetic layer according to the described memory element of claim 1.
19., it is characterized in that wherein a cellar area is from 0.5nm according to the described memory element of claim 2 2To 5 μ m 2
20., it is characterized in that wherein this recorded information is read out by utilize the giant magnetoresistance effect that produces in applying electric current according to the described memory element of claim 2.
21., it is characterized in that wherein this recorded information illuminates second ferromagnetic layer by using up according to the described memory cell of claim 2, and to be used in be the magnetic Kerr effect that produces and being read out.
22., comprising according to the described memory cell of claim 1:
First and second ferromagnetic layers, wherein the change of the direction of magnetization of its one deck is inducted by the electronics that injects spin polarization at least; And
The spin conducting shell, constitute by at least a portion of the hollow cylindrical molecule of axially arranging to the laminating direction of first and second ferromagnetic layers by setting it, this spin conducting shell is set between first ferromagnetic layer and second ferromagnetic layer shielding the mutual effect of its magnetic, and the electronics of its conduction spin polarization.
23. according to the described memory element of claim 22, it is characterized in that, wherein cylindrical molecular axis to middle body play a part the spin conducting shell, and first ferromagnetic layer and second ferromagnetic layer are included in respectively in an end and another end.
24., it is characterized in that wherein cylindrical molecule molecule is the component units of element according to the described memory element of claim 22.
25. according to the described memory element of claim 22, it is characterized in that, wherein the spin conducting shell of making by cylindrical molecule its direction of principal axis have one than it in working temperature the time the short length of spin coherence length.
26., it is characterized in that wherein the spin conducting shell of being made by cylindrical molecule comprises other molecule or atom at hollow space according to the described memory element of claim 22.
27. memory element according to claim 22 comprises spin arrangement thin layer between first ferromagnetic layer and second ferromagnetic layer.
28., it is characterized in that wherein this spin alignment layer comprises low magnetic material according to the described memory element of claim 27.
29., it is characterized in that wherein low magnetic material is by (In, Mn) As, (Ga, Mn) As, (Cd, Mn) Te, (Zn, Mn) Te and (Zn, Cr) at least a the making among the Te according to the described memory element of claim 28.
30. memory element according to claim 26 is characterized in that, and is comprising the spin coherence length at the molecule or the atom of hollow space, when working temperature, longer than the length of the spin conducting shell that makes progress at cylindrical molecular axis.
31., it is characterized in that wherein this cylindrical molecule is a carbon nano-tube according to the described memory element of claim 22.
32. a storage device that is made of a plurality of memory elements of arranging is characterized in that, wherein
Memory element comprises by spherical shell with aperture or cylindrical molecular material makes the spin conducting shell, and the electronics of spin polarization is conducted by this spin conducting shell.
33., it is characterized in that wherein this memory element comprises according to the described storage device of claim 32:
First ferromagnetic layer, wherein a direction of magnetization is fixed;
The spin conducting shell is formed on above first ferromagnetic layer, is made by the spherical shell molecular material with aperture, comprises paramagnetic material in this aperture, and has given spin phase length; And
Second ferromagnetic layer is formed on the spin conducting shell of the first ferromagnetic layer opposite, one side mouth, wherein changes the direction of magnetization by spinning polarized electron, wherein writes recorded information by the direction of magnetization that changes this second ferromagnetic layer.
34., it is characterized in that the spherical shell molecular material that wherein constitutes the spin conducting shell is this molecule fullerene according to the described storage device of claim 33.
35., it is characterized in that wherein this memory element comprises according to the described storage device of claim 32:
First and second ferromagnetic layers, wherein its at least one the direction of magnetization changes by injecting spinning polarized electron and inducts; And
The spin conducting shell, by constituting by at least a portion in the hollow cylindrical molecule that its laminating direction that axially is set to first and second ferromagnetic layers is arranged, this spin conducting shell is set between first ferromagnetic layer and second ferromagnetic layer, shielding the interaction of its magnetic, and conduct the electronics of this spin polarization.
36., it is characterized in that wherein this memory element is assembled integral body by the axially-aligned of quasi-cylindrical molecule is got up according to the described storage device of claim 35.
CN 200380100824 2002-10-03 2003-10-02 Memory device and memory Pending CN1703780A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP290732/2002 2002-10-03
JP290731/2002 2002-10-03
JP2002290731 2002-10-03

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103827969A (en) * 2011-09-15 2014-05-28 国际商业机器公司 Antiferromagnetic storage device

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103827969A (en) * 2011-09-15 2014-05-28 国际商业机器公司 Antiferromagnetic storage device
US9437269B2 (en) 2011-09-15 2016-09-06 Globalfoundries Inc. Antiferromagnetic storage device
CN103827969B (en) * 2011-09-15 2017-05-31 国际商业机器公司 Anti-ferromagnetism storage device

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