CN111725386A - Magnetic memory device and manufacturing method thereof, memory and neural network system - Google Patents
Magnetic memory device and manufacturing method thereof, memory and neural network system Download PDFInfo
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- CN111725386A CN111725386A CN201910897594.3A CN201910897594A CN111725386A CN 111725386 A CN111725386 A CN 111725386A CN 201910897594 A CN201910897594 A CN 201910897594A CN 111725386 A CN111725386 A CN 111725386A
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Abstract
The invention relates to a magnetic memory device and a manufacturing method thereof, a memory and a neural network system, wherein the magnetic memory device comprises a free layer; the free layer comprises at least two ferromagnetic layers with variable magnetic moment directions and at least one decoupling layer, each decoupling layer in the at least one decoupling layer is arranged between two ferromagnetic layers in the at least two ferromagnetic layers, and the decoupling layer between the two ferromagnetic layers enables no coupling effect between the two ferromagnetic layers. According to the magnetic storage device, when the magnetic moment direction of the ferromagnetic layer in the free layer changes, the magnetic storage device is caused to have four or more magnetic moment states, and each magnetic moment state can represent binary logic information, so that multi-value storage can be realized; in addition, the magnetic storage device is applied to a neural network system, and various weight coefficients in convolution calculation can be realized.
Description
Technical Field
The invention relates to the technical field of nonvolatile storage and neural networks, in particular to a magnetic storage device, a manufacturing method thereof, a storage and a neural network system.
Background
As shown in fig. 1, a magnetic memory device in the related art is generally composed of a buffer layer 110, a pinned layer 210, a reference layer 310, a barrier layer 410 (or a space layer), a free layer 510, and a hard mask layer 610. Magnetic memory devices can be classified into two categories according to the difference in magnetic anisotropy: in-plane magnetic anisotropic magnetic memory devices and perpendicular magnetic anisotropic magnetic memory devices.
The reference layer of the magnetic memory device is composed of a single-layer or multi-layer ferromagnetic layer and a coupling layer positioned between the ferromagnetic layers, the magnetic moment of the ferromagnetic material is firmly pinned, and the direction is fixed and unchanged; the free layer is composed of a single-layer or double-layer ferromagnetic layer and a coupling layer between the ferromagnetic layers, and usually the magnetic moments of all the ferromagnetic layers in the free layer can be regarded as a whole, and the direction of the magnetic moment of the whole can be changed. Magnetic memory devices have two main magnetic moment states: when the magnetic moment directions of the free layer and the reference layer are consistent, the device presents a low-resistance state; when the magnetic moments of the free layer and the reference layer are opposite, the device presents a high resistance state. Due to the above characteristics, the low resistance state is used to represent a binary logic state "0" and the high resistance state is used to represent a binary logic state "1" which is commonly used as a core device of a Magnetic Random Access Memory (MRAM). This means that one magnetic memory device can only have one bit of information storage, and how to increase the information storage of each magnetic memory device is very important to improve the read/write efficiency and the information storage density of the MRAM.
Disclosure of Invention
The embodiment of the application provides a magnetic storage device, a manufacturing method thereof, a storage and a neural network system.
In one aspect, the present application provides a magnetic memory device comprising a free layer; the free layer comprises at least two ferromagnetic layers with variable magnetic moment directions and at least one decoupling layer, and each decoupling layer in the at least one decoupling layer is arranged between two ferromagnetic layers in the at least two ferromagnetic layers; the decoupling layer between the two ferromagnetic layers ensures that the two ferromagnetic layers have no coupling effect; wherein any two of the at least two ferromagnetic layers differ in composition and/or thickness; or, the free layer comprises two or more decoupling layers, and the thickness and/or composition of any two decoupling layers in the two or more decoupling layers are different.
In another aspect, the present application provides a method of fabricating a magnetic memory device, including depositing a buffer layer, a pinning layer, a reference layer, and a barrier layer in sequence; depositing a free layer on the barrier layer; the free layer comprises at least two ferromagnetic layers with variable magnetic moment directions and at least one decoupling layer, and the compositions and/or thicknesses of any two ferromagnetic layers in the at least two ferromagnetic layers are different; or the free layer comprises two or more decoupling layers, and the thicknesses and/or compositions of any two decoupling layers in the two or more decoupling layers are different; annealing the free layer; a hard mask layer is deposited over the free layer.
In another aspect, the present application provides a method of fabricating a magnetic memory device, including depositing a buffer layer, a pinning layer, a reference layer, and a barrier layer in sequence; depositing a first ferromagnetic layer and a first decoupling layer on the barrier layer, and performing first annealing on the first ferromagnetic layer and the first decoupling layer; depositing a second ferromagnetic layer on the first decoupling layer, and annealing the second ferromagnetic layer for the second time; wherein the annealing conditions of the first annealing and the second annealing are different, and the annealing conditions comprise annealing temperature, annealing time and annealing atmosphere; a hard mask layer is deposited on the second ferromagnetic layer.
In another aspect, the present application provides a memory comprising a conductive line for generating a magnetic field, the above-described magnetic memory device, and a magnetic sensing device; the magnetic storage device is used for presenting a plurality of magnetic moment states according to a magnetic field generated by the wire; the magnetic sensing device is used to obtain the magnetic moment state of the magnetic memory device.
In another aspect, the present application provides a neural network system, including a computing unit, the computing unit including a conductive line for generating a magnetic field, the above-mentioned magnetic memory device, a magnetic detecting device, and a resistive coupling device; one end of the resistive coupling device is connected with one end of the magnetic detection device, and the other end of the resistive coupling device is connected with the other end of the magnetic detection device; the magnetic storage device can present various magnetic moment states according to a magnetic field generated by a wire, and the synapse weight of the neural network system corresponds to one magnetic moment state of the various magnetic moment states; the magnetic detection device is used for acquiring the magnetic moment state of the magnetic storage device so as to acquire the synaptic weight corresponding to the magnetic moment state.
The magnetic memory device, the manufacturing method thereof, the memory and the neural network system provided by the embodiment of the application have the following technical effects:
a magnetic memory device includes a free layer; the free layer comprises at least two ferromagnetic layers with variable magnetic moment directions and at least one decoupling layer, and each decoupling layer in the at least one decoupling layer is arranged between two ferromagnetic layers in the at least two ferromagnetic layers; wherein any two of the at least two ferromagnetic layers differ in composition and/or thickness; or, the free layer comprises two or more decoupling layers, and the thickness and/or composition of any two decoupling layers in the two or more decoupling layers are different. According to the magnetic storage device provided by the application, when the magnetic moment direction of the ferromagnetic layer in the free layer changes, the magnetic storage device is caused to have four or more magnetic moment states, each magnetic moment state can represent binary logic information, and taking the case that the free layer comprises two ferromagnetic layers, the magnetic storage device can present four magnetic moment states which can represent binary logic information of '00', '01', '10' and '11', and binary storage of one device can be realized. The magnetic memory device provided by the application can present four or more magnetic moment states, and each magnetic moment state can represent different binary logic information, so that multi-value storage can be realized; in addition, the magnetic storage device is applied to a neural network system, and various weight coefficients in convolution calculation can be realized.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a prior art magnetic memory device;
FIG. 2 is a schematic diagram of a magnetic memory device according to an embodiment of the present application;
FIG. 3 is a schematic diagram illustrating magnetic moment states of a magnetic memory device according to an embodiment of the present application;
FIG. 4 is a schematic diagram illustrating magnetic moment states of another magnetic memory device provided by an embodiment of the present application;
fig. 5 is a schematic structural diagram of an decoupling layer provided in an embodiment of the present application;
FIG. 6 is a schematic structural diagram of another decoupling layer provided in an embodiment of the present application;
FIG. 7 is a schematic structural diagram of a free layer provided in an embodiment of the present application;
fig. 8 is a schematic diagram illustrating a relationship between a magnetic field direction of an oersted magnetic field and a voltage pulse according to an embodiment of the present application;
FIG. 9 is a schematic diagram of magnetic moment states of a magnetic memory device as a function of voltage pulses according to an embodiment of the present application;
FIG. 10 is a schematic diagram of the relationship between the magnetic field direction and the voltage pulse of another Oersted magnetic field provided by the embodiment of the present application;
FIG. 11 is a schematic diagram of magnetic moment states of another magnetic memory device provided by an embodiment of the present application as a function of voltage pulses;
FIG. 12 is a schematic structural diagram of a memory cell in a memory according to an embodiment of the present disclosure;
FIG. 13 is a schematic structural diagram of a memory cell in a memory according to an embodiment of the present disclosure;
FIG. 14 is a schematic structural diagram of a neural network computing module according to an embodiment of the present disclosure;
the following is a supplementary description of the drawings:
110-a buffer layer; 210-a pinning layer; 310-a reference layer; 410-barrier layer;
510 a free layer; 511-ferromagnetic layer; 512-ferromagnetic layer; 513-decoupling layer; 5131-first inducing layer; 5132-a second inducing layer;
610-hard mask layer;
1200-a magnetic memory device; 1201-SQUID device; 1202-solenoid; 1203-word line; 1204-word line; 1205-write/read bit line; 1206-write/read bit line;
1300-a magnetic memory device; 1301-SQUID device; 1302 a write bit line; 1303-write bit line; 1304-word line; 1305-read bit lines; 1306-a read bit line;
1401-input conductors; 1402-output leads, 1403-magnetic storage device; 1404 — a conductive line; 1405-magnetic detection device; 1406-resistive type coupling elements.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic may be included in at least one implementation of the present application. In the description of the present application, it is to be understood that the terms "upper", "lower", "top", "bottom", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred devices or elements must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein.
Referring to fig. 2, fig. 2 is a schematic structural diagram of a magnetic memory device according to an embodiment of the present application, including a free layer 510;
the free layer 510 includes at least two ferromagnetic layers having a variable magnetic moment direction and at least one decoupling layer, each decoupling layer of the at least one decoupling layer being disposed between two ferromagnetic layers of the at least two ferromagnetic layers; the decoupling layer between the two ferromagnetic layers ensures that the two ferromagnetic layers have no coupling effect; wherein any two of the at least two ferromagnetic layers differ in composition and/or thickness; or, the free layer comprises two or more decoupling layers, and the thickness and/or composition of any two decoupling layers in the two or more decoupling layers are different.
In the embodiment of the present application, the free layer 510 includes two or more ferromagnetic layers and an decoupling layer located between the ferromagnetic layers, and the thickness of the decoupling layer between the two ferromagnetic layers is greater than or equal to 5 nm, so that there is no coupling effect between the two ferromagnetic layers, and when the magnetic moment direction of a certain ferromagnetic layer changes, the magnetic moment direction of other ferromagnetic layers may not be affected. Wherein, the compositions and/or thicknesses of any two ferromagnetic layers are different, so that the magnetic anisotropies of each ferromagnetic layer are different; alternatively, the free layer includes two or more decoupling layers, and the two or more decoupling layers have different thicknesses and/or compositions, so that the magnetic anisotropy of each ferromagnetic layer can be different. The magnetic memory device may exhibit four or more magnetic moment states, each of which may represent a binary logic information, according to a change in the direction of the magnetic moment of the ferromagnetic layer in the free layer 510.
In the embodiment of the present application, the magnetic memory device further includes a buffer layer 110, a pinned layer 210, a reference layer 310, a barrier layer 410, and a hard mask layer 610, and the magnetic memory device is sequentially ordered from bottom to top as the buffer layer 110, the pinned layer 210, the reference layer 310, the barrier layer 410, a free layer 510, and the hard mask layer 610. The magnetic memory device may have a shape of a cylinder, an elliptical cylinder, an irregular cylinder, a cube, and a rectangular parallelepiped.
Referring to fig. 3, fig. 3 is a schematic diagram illustrating magnetic moment states of a magnetic memory device according to an embodiment of the present application, in which the magnetic memory device has perpendicular magnetic anisotropy, and two ferromagnetic layers 511 and 512 are present in a free layer 510. The magnetic memory device can present four magnetic moment states, which respectively represent binary logic information of '00', '01', '10', '11', so that binary storage of one device can be realized. Fig. 4 is a schematic diagram of magnetic moment states of another magnetic memory device provided in this embodiment of the present application, which is a magnetic memory device with in-plane magnetic anisotropy, and the two ferromagnetic layers 511 and 512 are present in the free layer 510 as an example, and the principle is the same as that of the magnetic memory device with perpendicular magnetic anisotropy. The magnetic memory device provided by the application can present four or more magnetic moment states, and each magnetic moment state can represent different binary logic information, so that multi-value storage can be realized. Note that the arrows in the ferromagnetic layers in the drawings have different lengths, which indicate that the magnitude of the magnetic anisotropy of the ferromagnetic layers is different.
In the embodiment of the present application, the material of the decoupling layer 513 includes a metal material and/or an oxide material; the metal material comprises a metal material doped with impurity particles and a metal material doped with no impurity particles.
The above metal material may include any one of Al, Cr, Mn, Cu, Zn, Ag, and Au;
the oxide material may include MgO, Al2O3、AlOx、BiFeO3、NiO、CoO、Ni0.5Co0.5O、GdOyAnd MgAl2O4Any one or more.
Referring to fig. 5, fig. 5 is a schematic structural diagram of an decoupling layer according to an embodiment of the present disclosure.
Alternatively, as shown in fig. 5(a), the decoupling layer 513 may have a single-layer structure composed of only any one of the above-described metal materials.
Alternatively, as shown in fig. 5(b), the decoupling layer 513 may have a single-layer structure formed only of any one of the above-described oxide materials.
Alternatively, as shown in fig. 5(c), the decoupling layer 513 may have a multilayer structure formed of the metal material doped with the impurity-free particles and the oxide material.
Alternatively, as shown in fig. 5(d), the decoupling layer 513 may have a single-layer structure formed by doping impurity particles with any of the above-described metal materials.
In the embodiment of the present application, the thickness of each decoupling layer 513 is greater than or equal to 5 nanometers, so that the coupling strength between different ferromagnetic layers is substantially zero, and when the magnetic moment direction of one of the ferromagnetic layers changes, the magnetic moment directions of the other ferromagnetic layers are not affected.
Referring to fig. 6, fig. 6 is a schematic structural diagram of another decoupling layer according to an embodiment of the present disclosure.
In the embodiment of the present application, the decoupling layer 513 of the at least one decoupling layer includes the first inducing layer 5131 and/or the second inducing layer 5132; wherein the first inducing layer 5131 is located at the first surface of the decoupling layer 513 comprising the first inducing layer 5131, and the second inducing layer 5132 is located at the second surface of the decoupling layer 513 comprising the second inducing layer 5132; the first inducing layer 5131 and the second inducing layer 5132 are different in composition and/or thickness.
Alternatively, the decoupling layer 513 includes a first inducing layer 5131 and a second inducing layer 5132, the first surface of the decoupling layer 513 is adjacent to the ferromagnetic layer 511, the second surface of the decoupling layer 513 is adjacent to the ferromagnetic layer 512, and the first inducing layer 5131 and the second inducing layer 5132 have different compositions but the same thickness, so that the magnitude of the magnetic anisotropy of the ferromagnetic layer 512 adjacent to the first inducing layer 5131 and the ferromagnetic layer adjacent to the second inducing layer can be made different.
In an embodiment of the present application, the thickness of the first inducing layer and the thickness of the second inducing layer are both less than 2 nm.
The material of the first inducing layer and the material of the second inducing layer may include: any one metal of Mo, Ru, Rh, Pd, Hf, Ta, W, Ir, Pt and Tb; or any alloy of IrMn, FeMn and PdMn; or MgO, AlOxAny one of the oxides; or a graphene material; alternatively, other two-dimensional materials that readily undergo orbital hybridization with adjacent magnetic particles are also possible.
In an embodiment of the present application, the composition of the ferromagnetic layer includes a mixed-metal material; the mixed metal material comprises at least two of Co, Fe, Ni, Mn, Rh, Pd, Pt, Gd, Tb, Dy, Ho, B, Al, Si, Ga and Ge. The magnitude of the magnetic anisotropy of each ferromagnetic layer is made different from each other by adjusting the composition and/or thickness of each ferromagnetic layer in the free layer 510. Referring to fig. 7, fig. 7 is a schematic structural diagram of a free layer according to an embodiment of the present disclosure.
Alternatively, as shown in FIG. 7(a), the ferromagnetic layer 511 and the ferromagnetic layer 512 have different compositions, and specifically, the ferromagnetic layer 511 may be Co20Fe60B20The ferromagnetic layer 512 may be Co40Fe40B20。
Alternatively, as shown in fig. 7(b), the ferromagnetic layer 511 and the ferromagnetic layer 512 have the same composition but different thicknesses.
Alternatively, as shown in fig. 7(c) and (d), the ferromagnetic layer 511 and the ferromagnetic layer 512 are different in composition and thickness.
The present application also provides a method of manufacturing a magnetic memory device, comprising: depositing a buffer layer, a pinning layer, a reference layer and a barrier layer in sequence; depositing a free layer on the barrier layer; the free layer comprises at least two ferromagnetic layers with variable magnetic moment directions and at least one decoupling layer, and the compositions and/or thicknesses of any two ferromagnetic layers in the at least two ferromagnetic layers are different; or the free layer comprises two or more decoupling layers, and the thicknesses of any two decoupling layers in the two or more decoupling layers are different; annealing the free layer; a hard mask layer is deposited over the free layer.
In the embodiment of the present application, the deposition manner may include physical vapor deposition and chemical vapor deposition, and specifically, the deposition manner may include magnetron sputtering, pulsed laser deposition, and molecular beam epitaxy.
In an alternative embodiment in which the free layer is deposited on the barrier layer, the free layer may include a first ferromagnetic layer, a first decoupling layer, and a second ferromagnetic layer, the first ferromagnetic layer and the second ferromagnetic layer differing in thickness and/or composition; the first ferromagnetic layer, the first decoupling layer, and the second ferromagnetic layer are sequentially deposited on the barrier layer. Specifically, the first ferromagnetic layer may be Co20Fe60B20The second ferromagnetic layer may be Co40Fe40B20The thicknesses of the first and second ferromagnetic layers are the same, such that the magnitudes of the magnetic anisotropies of the first and second ferromagnetic layers are different.
In another alternative embodiment of depositing a free layer on the barrier layer, the free layer may include a first ferromagnetic layer, a first decoupling layer, a second ferromagnetic layer, a second decoupling layer, and a third ferromagnetic layer, the first decoupling layer and the second decoupling layer having different thicknesses and/or compositions; the first ferromagnetic layer, the first decoupling layer, the second ferromagnetic layer, the second decoupling layer, and the third ferromagnetic layer are sequentially deposited on a barrier layer. Specifically, the thickness of the first decoupling layer is 7 nm, the thickness of the second decoupling layer is 6 nm, the first decoupling layer includes a first inducing layer, the composition of the first decoupling layer may include Al and Mo, and the composition of the second decoupling layer may include Cr.
The present application also provides a method of manufacturing a magnetic memory device, comprising: depositing a buffer layer, a pinning layer, a reference layer and a barrier layer in sequence; depositing a first ferromagnetic layer and a first decoupling layer on the barrier layer, and performing first annealing on the first ferromagnetic layer and the first decoupling layer; depositing a second ferromagnetic layer on the first decoupling layer, and annealing the second ferromagnetic layer for the second time; wherein the annealing conditions of the first annealing and the second annealing are different, and the annealing conditions comprise annealing temperature, annealing time and annealing atmosphere; a hard mask layer is deposited on the second ferromagnetic layer.
Note that, the first ferromagnetic layer, the first decoupling layer, and the second ferromagnetic layer all belong to a free layer, and the free layer in the embodiment of the present application may further include two or more ferromagnetic layers and one or more decoupling layers. The structure of the free layer is different from that of the free layer in the embodiment of the present application, but the quality (roughness, crystallization degree, interface atomic diffusion degree, etc.) of the interface between the decoupling layer and the ferromagnetic layer is also controlled by changing the annealing condition, so as to achieve the technical effects that the magnetic anisotropies of the ferromagnetic layers are different in magnitude, and the method belongs to the protection scope of the present application.
Specifically, the annealing temperature of the first annealing is higher than that of the second annealing, the time required by the first annealing is longer than that of the second annealing, different atmosphere gases can be introduced during the first annealing and the second annealing, and the gases can include H2Ar and H in different proportions2and/Ar mixed gas.
In the embodiment of the application, the magnetic moment direction of the ferromagnetic layer in the free layer is regulated and controlled by the Oersted magnetic field. Specifically, a solenoid or two mutually perpendicular and non-intersecting long straight wires are arranged near the magnetic memory device, and voltage pulses with different amplitudes or polarities are introduced into the solenoid or the two long straight wires to generate an Oersted magnetic field perpendicular to the surface of the thin film or parallel to the surface of the free layer around the solenoid or the two long straight wires so as to regulate and control the magnetic memory device to present different magnetic moment states.
Referring to FIG. 2, the free layer 510 in FIG. 2(a) is illustrated as including two ferromagnetic layers 511 and 512, wherein the ferromagnetic layers 511 and 512 have perpendicular magnetic anisotropy. A solenoid is disposed near the magnetic memory device to generate a vertical Oersted magnetic field, and the solenoid may be Cu or Nb.
Referring to fig. 8 and 9, fig. 8 is a schematic diagram illustrating a relationship between a magnetic field direction of an oersted magnetic field and a voltage pulse according to an embodiment of the present application, and fig. 9 is a schematic diagram illustrating a magnetic moment state of a magnetic memory device according to an embodiment of the present application varying with a voltage pulse.
Assuming that the solenoid is energized with a voltage pulse V to generate an Oersted magnetic field Hp, HP points from the lower side to the upper side when V is positive, and Hp points from the upper side to the lower side when V is negative; the direction of the magnetic moment of the reference layer 310 is fixed in a direction pointing from the lower side to the upper side and parallel to the free layer easy axis, as indicated by the bold arrow M. At time t0, the magnetic memory device is initialized such that the direction of magnetic moment M1 of ferromagnetic layer 511 and the direction of magnetic moment M2 of ferromagnetic layer 512 both coincide with the direction of magnetic moment M of the reference layer, which may represent "magnetic moment state 1"; in a period t1, a small negative voltage pulse is applied to the solenoid coil, the M2 with a small magnetic anisotropy field starts to turn over, and the M1 with a large magnetic anisotropy field still points to the upper side from the lower side; time period t2, no current in the solenoid, M2 pointing from the top to the bottom and M1 still pointing from the bottom to the top, may represent "moment state 2"; in a period t3, a large negative voltage pulse is applied to the solenoid coil, and M1 starts to turn over; time period t4, no current in the solenoid, M1 and M2 both pointing from the top to the bottom, which may represent "magnetic moment state 3"; in a period t5, a small positive voltage pulse is applied to the solenoid coil, and M2 with a small magnetic anisotropy field starts to turn over; time period t6, no current in the solenoid, M2 pointing from the bottom to the top and M1 pointing from the top to the bottom, may represent "moment state 4"; in a period t7, a large positive voltage pulse is applied to the solenoid coil, and M1 with a large anisotropic field starts to turn over; at time t8, no current in the solenoid, M1 and M2 pointing from the bottom to the top, may represent "moment state 1".
The following description will be given taking as an example that the free layer 510 in fig. 2(b) includes two ferromagnetic layers 511 and 512, and the ferromagnetic layers 511 and 512 have in-plane magnetic anisotropy. Two long straight wires are arranged around the magnetic memory device to generate parallel oersted magnetic fields, the two wires are perpendicular to each other and are not connected, and the magnetic memory device exists near the intersection point of the two wires.
Referring to fig. 10 and 11, fig. 10 is a schematic diagram illustrating a relationship between a magnetic field direction of another oersted magnetic field and a voltage pulse according to an embodiment of the present application, and fig. 11 is a schematic diagram illustrating a magnetic moment state of another magnetic memory device according to an embodiment of the present application varying with a voltage pulse.
Assuming that a voltage pulse V1 is applied to the wire 1 of the two wires, an oersted magnetic field H1 is generated, when V1 is positive, H1 is directed from the lower side to the upper side; wire 2 of the two wires applies a voltage pulse V2, generating an oersted magnetic field H2, H2 pointing from the left to the right when V2 is positive, and it is possible to flip the magnetic moment directions of ferromagnetic layers 511, 512 in the magnetic memory device near the intersection only when both wires have a voltage pulse present; the magnetic moment M of the reference layer is parallel to the easy axis of the free layer and its direction is fixed from left to right. At time t0, the magnetic memory device is initialized such that the direction of magnetic moment M1 of ferromagnetic layer 511 and the direction of magnetic moment M2 of ferromagnetic layer 512 both coincide with the direction of magnetic moment M of the reference layer, which may represent "magnetic moment state 1"; in a period t1, a small positive voltage pulse is applied to the lead 1, a small negative voltage pulse is applied to the lead 2, the M2 with small magnetic anisotropy field starts to turn over, and the M1 is slightly deviated from the easy axis; during time t2, when neither lead 1 nor lead 2 has a pulse voltage, M2 points to the left from the right, and M1 still returns to the easy axis closest to it, which points to the right from the left, which may indicate "moment state 2"; in a period t3, when a larger positive voltage pulse is applied to the lead 1 and a larger negative voltage pulse is applied to the lead 2, the M1 with a larger magnetic anisotropy field starts to turn over, and the M2 slightly deviates from the easy axis direction; during time t4, when neither lead 1 nor lead 2 has a pulse voltage, M1 points to the left from the right, and M2 will eventually return to its easy axis, also pointing to the left from the right, which may indicate "moment state 3"; in the period t5, when the lead 1 applies a small positive voltage pulse and the lead 2 applies a small positive voltage pulse, the M2 with small magnetic anisotropy field starts to turn over, and the M1 is slightly deviated from the easy axis; during time t6, when neither lead 1 nor lead 2 has a pulse voltage, M2 points to the right from the left, and M1 still returns to the easy axis closest to it, which points to the left from the right, which may indicate "moment state 4"; in the period t7, when the lead 1 applies a large positive voltage pulse and the lead 2 applies a large positive voltage pulse, the M1 with large magnetic anisotropy field starts to turn over, and the M2 is slightly deviated from the easy axis; during time t8, when neither lead 1 nor lead 2 has a pulse voltage, M1 points to the right from the left, and M2 eventually returns to its easy axis, also pointing in the right from the left, which may indicate "moment state 1". It should be noted that the amplitude of the pulse voltage in the two wires can be adjusted according to the actual performance of the magnetic memory device, and the amplitude of the voltage pulse in the wire 1 can be larger than the amplitude of the voltage pulse in the wire 2 or smaller than the amplitude of the voltage pulse in the wire 2.
The present application also provides a memory comprising a conductive line for generating a magnetic field, the above magnetic memory device and a magnetic sensing device; a magnetic memory device for exhibiting a plurality of magnetic moment states according to a magnetic field generated by the conductive line; and a magnetic detection device for acquiring a magnetic moment state of the magnetic memory device.
In the embodiment of the present application, when writing data into the memory: the magnetic moment states of the magnetic memory device are regulated and controlled through a perpendicular or parallel Oersted magnetic field generated by the solenoid or two perpendicular and non-intersecting long straight wires, so that the magnetic memory device has four or more than four magnetic moment states and can represent multi-bit binary logic information.
When reading data from the memory: the magnetic moment state of the magnetic memory device is acquired by a magnetic sensing device.
In the embodiment of the present application, the memory may be an MRAM. The MRAM comprises a plurality of magnetic storage devices, and the magnetic storage devices, a writing bit line, a reading bit line, a word line, an MOS tube and a magnetic detection device jointly form a storage array of the MRAM, so that the MRAM with large storage capacity and capable of working in an ultralow temperature region can be realized.
In the embodiment of the application, the magnetic detection device can be a superconducting quantum interference device (SQUID) and a Nano-superconducting quantum interference device (Nano-SQUID) based on a josephson section or a Nano-bridge section. When the magnetic moment state of the magnetic storage device is obtained, a bias current is applied to the two ends of the SQUID device to enable the device to work normally, when the magnetic moment state of the magnetic storage device changes, magnetic flux of the SQUID device changes, voltage at the two ends of the SQUID device jumps, and the current magnetic moment state of the magnetic storage device can be obtained by measuring the voltage at the two ends of the SQUID device.
The following description is made in terms of a magnetic memory device in a memory having perpendicular magnetic anisotropy. Referring to fig. 12, fig. 12 is a schematic structural diagram of a memory cell in a memory according to an embodiment of the present disclosure, where the memory cell includes a magnetic memory device 1200, a SQUID device 1201, a solenoid 1202, a word line 1203, a word line 1204, a write/read bit line 1205, a write/read bit line 1206, a MOS1, and a MOS 2. The memory array of the memory comprises a plurality of memory cells. The write/read bit line 1205 and the write/read bit line 1206 may be made of Cu, Au, Al, or other high conductivity metal materials, or Nb, NbN, NbTi, NbTiN, Nb3Sn, high temperature superconductor, or other superconducting materials. The magnetic memory device 1200 includes a free layer 510, the free layer 510 including two ferromagnetic layers, and the ferromagnetic layers having perpendicular magnetic anisotropy.
When writing data to the memory: the write/read bit line 1205, the write/read bit line 1206, and the word line 1203 corresponding to the memory address of the memory cell are energized according to an external address decoding circuit, at this time, the MOS1 is turned on, the solenoid 1202 is energized to generate an oersted magnetic field, and by applying a voltage pulse to the solenoid 1202, the magnetic memory device 1200 can exhibit different magnetic moment states according to the magnitude and the positive and negative polarities of the voltage pulse, and respectively represent different information.
When reading data from the memory: a bias current is applied to the word line 1204, the write/read bit line 1205 and the write/read bit line 1206 corresponding to the memory address of the memory cell obtained by the external address decoding circuit, at this time, the MOS2 is turned on, and the current magnetic moment state of the magnetic memory device 1200, that is, the information corresponding to the current magnetic moment state, is obtained by measuring the voltage across the SQUID device 1201. For example, "magnetic moment state 1", "magnetic moment state 2", "magnetic moment state 3", and "magnetic moment state 4" represent "00", "01", "10", and "11", respectively.
The following description will be made in terms of a magnetic memory device in a memory having in-plane magnetic anisotropy. Referring to fig. 13, fig. 13 is a schematic structural diagram of a memory cell in a memory according to an embodiment of the present disclosure, where the memory cell includes a magnetic memory device 1300, a SQUID device 1301, a write bit line 1302, a write bit line 1303, a word line 1304, a read bit line 1305, a read bit line 1306, and a MOS 3. The write bit line 1302 and the write bit line 1303 are perpendicular to each other and do not cross for generating an oersted magnetic field. Write bit line 1302, write bit line1303. The read bit lines 1305 and 1306 can be Cu, Au, Al or other high conductivity metal material, and can also be Nb, NbN, NbTi, NbTiN, Nb3Sn, high temperature superconducting, or other superconducting material.
When writing data to the memory: the write bit line 1302 and the write bit line 1303 corresponding to the memory address of the memory cell are energized according to an external address decoding circuit to generate an oersted magnetic field, and by applying voltage pulses to the write bit line 1302 and the write bit line 1303, respectively, the magnetic memory device 1300 can present different magnetic moment states according to the magnitude and the positive and negative polarities of the two voltage pulses, and represent different information, respectively.
When reading data from the memory: the word line 1304, the read bit line 1305 and the read bit line 1306 corresponding to the memory address of the memory cell are energized by the external address decoding circuit, the MOS3 is turned on, a bias current is applied to the read bit line 1305 and the read bit line 1306 at the same time, and the current magnetic moment state of the magnetic memory device 1300, that is, the information corresponding to the current magnetic moment state, is obtained by measuring the voltage across the SQUID device 1301. For example, "magnetic moment state 1", "magnetic moment state 2", "magnetic moment state 3", and "magnetic moment state 4" represent "00", "01", "10", and "11", respectively.
The embodiment of the application also provides a neural network system. Referring to fig. 14, fig. 14 is a schematic structural diagram of a neural network system according to an embodiment of the present application, including a computing unit, where the computing unit includes a magnetic memory device 1403, a conducting wire 1404 for generating an oersted magnetic field, a magnetic detection device 1405, and a resistive coupling element 1406; one end of the resistive coupling device 1406 is connected to one end of the magnetic detection device 1405, and the other end of the resistive coupling device 1406 is connected to the other end 1405 of the magnetic detection device; wherein the magnetic memory device 1405 is capable of exhibiting a plurality of magnetic moment states according to a magnetic field generated by the wire 1404, and a synaptic weight of the neural network system corresponds to one of the plurality of magnetic moment states; the magnetic sensing device 1406 is used to obtain a magnetic moment state of the magnetic memory device 1405 to determine a synaptic weight corresponding to the magnetic moment state.
In the embodiment of the application, the magnetic storage device is applied to a computing unit of a neural network system, and the synaptic behaviors required in the learning and computing processes of the human brain are simulated.
Assuming that four neurons A1, A2, A3 and A4 exist at the input end and two neurons B1 and B2 exist at the output end of the neural network system, the input end and the output end of the neural network satisfy the formula: b isj＝σ(∑iAi·Wi,j) Wherein σ is expressed as a nonlinear equation; w is expressed as a synaptic weight; i represents 1, 2, 3 or 4; j represents 1 or 2. In the embodiment of the present application, there are four or more magnetic moment states of the magnetic memory device, i.e., there may be four or more synaptic weights for the same computation path, e.g., a1 through B1, so that various weight coefficients in the convolution calculation can be realized.
In the embodiment of the present application, the neural network system further includes four input wires 1401 and two output wires 1402, where the four input wires 1401 are respectively connected to the input ports a1, a2, A3, and a4, and the two output wires 1402 are respectively connected to the output ports B1 and B2; one end of the magnetism detecting device 1405 is connected to the input wiring 1401, and the other end of the magnetism detecting device 1405 is connected to the output wiring 1402.
Specifically, the calculation process of the calculation unit of the neural network system includes:
energizing the wire 1404, sequentially modulating or simultaneously modulating the plurality of magnetic memory devices 1403 using the oersted magnetic field generated by the wire 1404 such that all of the magnetic memory devices 1404 are in a determined magnetic moment state, i.e., there is a determined synaptic weight in the overall neural network calculation;
when a calculation instruction is received, analog voltages are applied to the four input wires 1401 as input data through the digital-analog converter, and bias current is supplied to the magnetic detection device 1405 at the same time; the input lead 1404, the magnetic detector 1405, the resistive coupling element 1406, and the output lead 1402 form a loop, and a current analog signal of the loop is measured; the current analog signal is converted to a digital signal by an analog-to-digital converter and output to the peripheral circuit over output conductor 1402. Wherein the output voltage of the magnetic sensing device 1405 can be changed by changing the magnetic moment state of the magnetic memory device 1404, and the current analog signal measured in the circuit will change under the condition that the amplitude and polarity of the voltage pulses on the input lead and the output lead are not changed; that is, the synaptic weights in the neural network calculation process vary with the magnetic moment states of the magnetic storage devices 1404, and four or more synaptic weights can be represented for the magnetic storage devices 1404 having four or more magnetic moment states, so that various weight coefficients in the convolution calculation can be realized.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (10)
1. A magnetic memory device, comprising a free layer;
the free layer comprises at least two ferromagnetic layers with variable magnetic moment directions and at least one decoupling layer, and each decoupling layer in the at least one decoupling layer is arranged between two ferromagnetic layers in the at least two ferromagnetic layers; a decoupling layer between the two ferromagnetic layers such that there is no coupling between the two ferromagnetic layers;
wherein any two of the ferromagnetic layers of the at least two ferromagnetic layers differ in composition and/or thickness; or, the free layer comprises two or more decoupling layers, and the thickness and/or the composition of any two decoupling layers in the two or more decoupling layers are different.
2. The magnetic memory device of claim 1,
the material of the decoupling layer comprises a metal material and/or an oxide material;
wherein the metal material comprises a metal material doped with impurity particles and a metal material doped without impurity particles.
3. The magnetic memory device of claim 2, wherein:
the metal material comprises any one of Al, Cr, Mn, Cu, Zn, Ag and Au;
the oxide material comprises MgO and Al2O3、AlOx、BiFeO3、NiO、CoO、Ni0.5Co0.5O、GdOyAnd MgAl2O4Any one or more.
4. The magnetic memory device of claim 1,
an decoupling layer of the at least one decoupling layer comprises a first inducing layer and/or a second inducing layer;
wherein the first inducing layer is located at a first surface of an decoupling layer comprising the first inducing layer and the second inducing layer is located at a second surface of the decoupling layer comprising the second inducing layer;
the first and second inducing layers are different in composition and/or thickness.
5. The magnetic memory device of claim 4, wherein the material of the first inducing layer and the material of the second inducing layer comprise:
any one metal of Mo, Ru, Rh, Pd, Hf, Ta, W, Ir, Pt and Tb; or;
any one alloy of IrMn, FeMn, PdMn; or;
MgO、AlOxany one of the oxides; or;
a graphene material.
6. The magnetic memory device of claim 1,
the composition of the ferromagnetic layer comprises a mixed-metal material; the mixed metal material comprises at least two of Co, Fe, Ni, Mn, Rh, Pd, Pt, Gd, Tb, Dy, Ho, B, Al, Si, Ga and Ge.
7. A method of fabricating a magnetic memory device, comprising:
depositing a buffer layer, a pinning layer, a reference layer and a barrier layer in sequence;
depositing a free layer on the barrier layer; the free layer comprises at least two ferromagnetic layers with variable magnetic moment directions and at least one decoupling layer, and the compositions and/or thicknesses of any two ferromagnetic layers in the at least two ferromagnetic layers are different; or, the free layer comprises two or more decoupling layers, and the thicknesses and/or compositions of any two decoupling layers in the two or more decoupling layers are different;
annealing the free layer;
and depositing a hard mask layer on the free layer.
8. A method of fabricating a magnetic memory device, comprising:
depositing a buffer layer, a pinning layer, a reference layer and a barrier layer in sequence;
depositing a first ferromagnetic layer and a first decoupling layer on the barrier layer, and annealing the first ferromagnetic layer and the first decoupling layer for a first time;
depositing a second ferromagnetic layer on the first decoupling layer, and annealing the second ferromagnetic layer a second time; wherein the annealing conditions of the first annealing and the annealing conditions of the second annealing are different, and the annealing conditions comprise annealing temperature, annealing time and annealing atmosphere;
a hard mask layer is deposited on the second ferromagnetic layer.
9. A memory comprising conductive lines for generating a magnetic field, magnetic storage means and magnetic detection means;
the magnetic memory device includes a free layer; the free layer comprises at least two ferromagnetic layers with variable magnetic moment directions and at least one decoupling layer, and each decoupling layer in the at least one decoupling layer is arranged between two ferromagnetic layers in the at least two ferromagnetic layers; a decoupling layer between the two ferromagnetic layers such that there is no coupling between the two ferromagnetic layers; wherein any two of the ferromagnetic layers of the at least two ferromagnetic layers differ in composition and/or thickness; or, the free layer comprises two or more decoupling layers, and the thicknesses and/or compositions of any two decoupling layers in the two or more decoupling layers are different;
the magnetic storage device is used for presenting a plurality of magnetic moment states according to the magnetic field generated by the wire;
the magnetic detection device is used for acquiring the magnetic moment state of the magnetic storage device.
10. A neural network system, comprising a computing unit; the computing unit comprises a lead wire for generating a magnetic field, a magnetic storage device, a magnetic detection device and a resistance type coupling device;
one end of the resistive coupling device is connected with one end of the magnetic detection device, and the other end of the resistive coupling device is connected with the other end of the magnetic detection device;
the magnetic memory device includes a free layer; the free layer comprises at least two ferromagnetic layers with variable magnetic moment directions and at least one decoupling layer, and each decoupling layer in the at least one decoupling layer is arranged between two ferromagnetic layers in the at least two ferromagnetic layers; a decoupling layer between the two ferromagnetic layers such that there is no coupling between the two ferromagnetic layers; wherein any two of the ferromagnetic layers of the at least two ferromagnetic layers differ in composition and/or thickness; or, the free layer comprises two or more decoupling layers, and the thicknesses and/or compositions of any two decoupling layers in the two or more decoupling layers are different;
wherein the magnetic storage device is capable of assuming a plurality of magnetic moment states according to a magnetic field generated by the wire, and a synaptic weight of the neural network system corresponds to one of the plurality of magnetic moment states;
the magnetic detection device is used for acquiring the magnetic moment state of the magnetic storage device so as to determine the synaptic weight corresponding to the magnetic moment state.
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