Probabilistic bit element

Abstract

To provide a probabilistic bit element having a memory cell based on spin-orbit torque that generates random numbers.SOLUTION: A probabilistic bit element according to the present invention includes: a spin-orbit torque pattern having a stacked combination of a ferromagnetic pattern exhibiting horizontal magnetic anisotropy and a conductive pattern on the ferromagnetic pattern; a magnetic tunnel junction pattern having a stacked combination of a free magnetic pattern with perpendicular magnetic anisotropy, a barrier pattern, and a fixed magnetic pattern with perpendicular magnetic anisotropy on a spin-orbit torque pattern; and a control unit configured to provide a plane current with a predetermined first magnitude and a magnetic field with a predetermined second magnitude applied horizontally in the plane of the spin-orbit torque pattern on the upper surface of the ferromagnetic pattern, and the first and second magnitudes correspond to the probability that the magnetization direction of the free magnetic pattern aligns with a specific direction, as predetermined.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a stochastic bit device that includes a memory cell based on Spin Orbit Torque (SOT). [Background technology]

[0002] A magnetic memory device such as a magnetic random access memory (MRAM) stores data using the resistance change of a magnetic tunnel junction element. The resistance of the magnetic tunnel junction element changes depending on the magnetization direction of the free layer. For example, when the magnetization direction of the free layer is the same as that of the pinned layer, the magnetic tunnel junction element has a low resistance, and when the magnetization directions are opposite, the magnetic tunnel junction element has a high resistance. When this characteristic is utilized in a memory device, for example, a magnetic tunnel junction element with a low resistance indicates data "0" and a magnetic tunnel junction element with a high resistance indicates data "1."

[0003] A magnetic memory element that uses spin transfer torque for the write operation to determine the direction of the free layer is called STT-MRAM (Spin Transfer Torque MRAM), and a magnetic memory element that uses spin orbit torque is called SOT-MRAM (Spin Orbit Torque MRAM).

[0004] STT-MRAM has an operating speed of approximately 50 to 100 nsec and excellent data retention of more than 10 years. SOT-MRAM has a spin polarization direction perpendicular to the magnetization direction, so it has an extremely fast operating speed of less than 10 nsec, which is faster than STT-MRAM. In addition, SOT-MRAM has different paths for the write current and the read current, so it has more stable durability. Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present invention to provide a probabilistic bit device that includes a spin-orbit torque-based memory cell that generates random numbers.

[0006] The technical problems of the present invention are not limited to those described above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0007] In order to achieve the above object, one aspect of the present invention provides a probabilistic bit element comprising: a spin-orbit torque pattern including a stacked combination of a ferromagnetic pattern with horizontal magnetic anisotropy and a conductive pattern on the ferromagnetic pattern; a magnetic tunnel junction pattern including a stacked combination of a free magnetic pattern with perpendicular magnetic anisotropy, a barrier pattern, and a fixed magnetic pattern with perpendicular magnetic anisotropy on the spin-orbit torque pattern; and a control unit configured to provide an in-plane current having a predetermined first magnitude and a magnetic field having a predetermined second magnitude to the spin-orbit torque pattern in a horizontal direction parallel to the top surface of the ferromagnetic pattern, wherein the first magnitude and the second magnitude correspond to a predetermined probability that the magnetization direction of the free magnetic pattern is in a specific direction.

[0008] In order to achieve the above object, another aspect of the present invention provides a probabilistic bit element including a memory cell including a ferromagnetic pattern, a conductive pattern, a free magnetic pattern, a barrier pattern, and a fixed magnetic pattern, which are stacked in sequence, and a control unit configured to provide an in-plane current and a magnetic field to the ferromagnetic pattern, wherein the magnetization direction of the ferromagnetic pattern is horizontal, the magnetization direction of the fixed magnetic pattern is fixed in the vertical direction, and the magnetization direction of the free magnetic pattern is vertical and is variable by the in-plane current and magnetic field.

[0009] In order to achieve the above object, a probabilistic bit element according to yet another aspect of the present invention includes a memory cell including a spin-orbit torque pattern and a magnetic tunnel junction pattern stacked in sequence, and a control unit configured to provide an in-plane current having a predetermined first magnitude and a magnetic field having a predetermined second magnitude to the spin-orbit torque pattern, wherein the first magnitude and the second magnitude correspond to a probability that the resistance of the magnetic tunnel junction pattern will have a particular resistance value. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a probabilistic bit element that can generate truly unpredictable random numbers and that can operate at high speed. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 illustrates a probabilistic bit element according to some embodiments. [Figure 2] 2 is a diagram for explaining measurement of an anomalous Hall effect (AHE) voltage in the memory cell of FIG. 1. FIG. [Figure 3] FIG. 3 is a diagram showing the relationship between the magnitude of the in-plane current and the normalized Hall resistance in the memory cell of FIG. [Figure 4] 4 is a diagram showing the relationship between the magnitude of the in-plane current in the memory cell of FIG. 3 and the probability that the magnetic tunnel junction pattern of the memory cell is in a parallel state. FIG. [Figure 5] FIG. 3 is a diagram showing the relationship between the magnitude of the magnetic field and the normalized Hall resistance in the memory cell of FIG. 2. [Figure 6] 6 is a diagram showing the relationship between the magnitude of the magnetic field in the memory cell of FIG. 5 and the probability that the magnetic tunnel junction pattern of the memory cell is in a parallel state. FIG. [Figure 7] FIG. 3 shows the normalized Hall resistance in the memory cell of FIG. 2. [Figure 8]FIG. 3 shows NIST (national institute of standards and technology) test results for normalized Hall resistance in the memory cell of FIG. 2. [Figure 9] FIG. 2 is a diagram for explaining a stochastic state of the magnetic tunnel junction structure of FIG. [Figure 10] FIG. 1 illustrates a probabilistic bit element according to some embodiments. [Figure 11] FIG. 1 illustrates a probabilistic bit element according to some embodiments. [Figure 12] FIG. 1 illustrates a probabilistic bit element according to some embodiments. [Figure 13] FIG. 1 illustrates a probabilistic bit element according to some embodiments. [Figure 14] FIG. 1 illustrates a probabilistic bit element according to some embodiments. [Figure 15] FIG. 1 illustrates a probabilistic bit element according to some embodiments. [Figure 16] 1 is a diagram illustrating a cell array of a magnetic memory device according to some embodiments. [Figure 17] 1 is a diagram illustrating a cell array of a magnetic memory device according to some embodiments. [Figure 18] 1 is a diagram illustrating a cell array of a magnetic memory device according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0012] FIG. 1 is a diagram illustrating a probabilistic bit element according to some embodiments.

[0013] Referring to FIG. 1, a probabilistic bit device according to some embodiments includes a memory cell 10 and a control unit 20.

[0014] The memory cell 10 includes a spin-orbit torque pattern SOT and a magnetic tunnel junction pattern MTJ.

[0015] The spin-orbit torque pattern SOT includes a ferromagnetic pattern 110 and a conductive pattern 120 that are stacked in sequence.

[0016] In some embodiments, the spin-orbit torque pattern SOT has a linear shape extending in a first direction X. The first direction X is a direction parallel to the top surface of the spin-orbit torque pattern SOT. Hereinafter, the first direction X and the second direction Y are parallel to the top surface of the spin-orbit torque pattern SOT and intersect each other at right angles. The third direction Z is a direction perpendicular to the top surface of the spin-orbit torque pattern SOT and intersects the first direction X and the second direction Y at right angles. The top surface, upper and lower directions are defined with reference to the third direction Z. The upper direction means the positive third direction Z, and the lower direction means the negative third direction Z.

[0017] The ferromagnetic pattern 110 has in-plane magnetic anisotropy (IMA). The magnetization direction 110M of the ferromagnetic pattern 110 is an in-plane direction that is a direction parallel to the top surface of the ferromagnetic pattern 110. Hereinafter, the in-plane direction refers to the direction parallel to the top surface of the ferromagnetic pattern 110. The magnetization direction 110M of the ferromagnetic pattern 110 is a first direction X.

[0018] The ferromagnetic pattern 110 includes a ferromagnetic material, such as at least one of iron (Fe), cobalt (Co), nickel (Ni), boron (B), silicon (Si), zirconium (Zr), platinum (Pt), terbium (Tb), palladium (Pd), copper (Cu), tungsten (W), and a mixture thereof.

[0019] The conductive pattern 120 includes, for example, a non-magnetic metal, such as at least one of platinum (Pt), tantalum (Ta), titanium (Ti), copper (Cu), tungsten (W), palladium (Pd), and a mixture thereof.

[0020] The magnetic tunnel junction pattern MTJ is formed on the spin-orbit torque pattern SOT. The magnetic tunnel junction pattern MTJ includes a free magnetic pattern 210, a barrier pattern 220, and a fixed magnetic pattern 230, which are stacked in sequence. The conductive pattern 120 extends between the ferromagnetic pattern 110 and the free magnetic pattern 210.

[0021] The fixed magnetic pattern 230 has perpendicular magnetic anisotropy (PMA). The magnetization direction 230M of the fixed magnetic pattern 230 is perpendicular to the in-plane direction. The magnetization direction 230M of the fixed magnetic pattern 230 is a perpendicular direction, for example, a third direction Z. The fixed magnetic pattern 230 has a fixed magnetization direction 230M regardless of an external magnetic field or an external electric field.

[0022] The free magnetic pattern 210 has perpendicular magnetic anisotropy. The free magnetic pattern 210 has two stable magnetization directions 210M parallel to the third direction Z. The two magnetization directions 210M are opposite to each other. The free magnetic pattern 210 has a magnetization direction 210M parallel to the magnetization direction 230M of the fixed magnetic pattern 230 (e.g., the magnetization direction 210M of the positive third direction Z or the magnetization direction 210M of the upward direction) or an anti-parallel to the magnetization direction 230M of the fixed magnetic pattern 230 (e.g., the magnetization direction 210M of the negative third direction Z or the magnetization direction 210M of the downward direction). The magnetization direction 210M of the free magnetic pattern 210 can be changed by an external magnetic field or an external electric field.

[0023] The magnetic tunnel junction pattern MTJ stores data using a difference in electrical resistance depending on the magnetization direction 230M of the fixed magnetic pattern 230 and the magnetization direction 210M of the free magnetic pattern 210. For example, when the magnetization direction 230M of the fixed magnetic pattern 230 and the magnetization direction 210M of the free magnetic pattern 210 are parallel, the magnetic tunnel junction pattern MTJ has a relatively low resistance value and stores data 0. Conversely, when the magnetization direction 210M of the free magnetic pattern 210 is antiparallel, the magnetic tunnel junction pattern MTJ has a relatively high resistance value and stores data 1.

[0024] In the following, the parallel state of the magnetic tunnel junction pattern MTJ means when the magnetization direction 230M of the fixed magnetic pattern 230 and the magnetization direction 210M of the free magnetic pattern 210 are parallel (when the magnetization direction 210M of the free magnetic pattern 210 is in the upward direction), and the anti-parallel state of the magnetic tunnel junction pattern MTJ means when the magnetization direction 230M of the fixed magnetic pattern 230 and the magnetization direction 210M of the free magnetic pattern 210 are anti-parallel (when the magnetization direction 210M of the free magnetic pattern 210 is in the downward direction).

[0025] The fixed magnetic pattern 230 includes a ferromagnetic material, such as at least one of iron (Fe), cobalt (Co), nickel (Ni), boron (B), silicon (Si), zirconium (Zr), platinum (Pt), terbium (Tb), palladium (Pd), copper (Cu), tungsten (W), and a mixture thereof.

[0026] The free magnetic pattern 210 includes a ferromagnetic material, such as at least one of iron (Fe), cobalt (Co), nickel (Ni), boron (B), silicon (Si), zirconium (Zr), platinum (Pt), terbium (Tb), palladium (Pd), copper (Cu), tungsten (W), and a mixture thereof.

[0027] The barrier pattern 220 extends between the free magnetic pattern 210 and the fixed magnetic pattern 230. The barrier pattern 220 includes an insulating metal oxide, such as at least one of aluminum oxide (AlOx), magnesium oxide (MgOx), tantalum oxide (TaOx), and zirconium oxide (ZrOx).

[0028] The electrode EL is formed on the magnetic tunnel junction pattern MTJ. The electrode EL includes, for example, at least one of a metal (e.g., tungsten, titanium, and / or tantalum) and a conductive metal nitride (e.g., titanium nitride, tantalum nitride, and / or tungsten nitride).

[0029] The control unit 20 is connected to the memory cell 10. The control unit 20 is connected to a first node N1, a second node N2, and a third node N3 of the memory cell 10. Opposite ends of the spin-orbit torque pattern SOT in the first direction X are connected to the first node N1 and the second node N2, respectively. For example, opposite ends of the ferromagnetic pattern 110 in the first direction X are connected to the first node N1 and the second node N2, respectively. An electrode EL is formed on the magnetic tunnel junction pattern MTJ. The electrode EL is connected to the third node N3. The control unit 20 is connected to the first node N1, the second node N2, and the third node N3.

[0030] Additional electronic elements may be disposed between the control unit 20 and the first node N1, between the control unit 20 and the second node N2, and between the control unit 20 and the third node N3, respectively. The electronic elements may include at least one of a transistor and a diode.

[0031] The control unit 20 applies a voltage or a current to the first to third nodes N1, N2, and N3 to perform write and read operations on the memory cells 10.

[0032] The control unit 20 applies an in-plane current I to the spin-orbit torque pattern SOT in the in-plane direction. SWFor example, the control unit 20 may apply an in-plane current I to the ferromagnetic pattern 110 in an in-plane direction parallel to the top surface of the ferromagnetic pattern 110. SW The control unit 20 applies an in-plane current I to the ferromagnetic pattern 110 in the first direction X. SW to provide.

[0033] In-plane current I SW flows in the spin-orbit torque pattern SOT. When the electrical conductivity of the conductive pattern 120 is larger than that of the ferromagnetic pattern 110, an in-plane current I SW mainly flows in the conductive pattern 120. The in-plane current I SW A spin current I with polarization in the third direction Z is generated by S A spin current I S includes a spin current generated in the ferromagnetic pattern 110 by the spin Hall effect and an interface spin current generated at the interface between the ferromagnetic pattern 110 and the conductive pattern 120.

[0034] Spin current I S The spin current I flows in a direction perpendicular to the interface between the spin-orbit torque pattern SOT and the magnetic tunnel junction pattern MTJ (for example, the third direction Z) and is applied to the free magnetic pattern 210. S applies a spin-orbit torque to the free magnetic pattern 210, inducing magnetization reversal of the free magnetic pattern 210. That is, the magnetic tunnel junction pattern MTJ becomes parallel or antiparallel. This causes a write operation to the memory cell 10.

[0035] The control unit 20 applies a magnetic field B X provides the magnetic field B X is provided to the spin-orbit torque pattern SOT in various ways. The control unit 20 applies a magnetic field B to the ferromagnetic pattern 110 in the first direction X. X provides the magnetic field B X induces a magnetization reversal in the free magnetic pattern 210. This causes a write operation to be performed in the memory cell 10.

[0036] The control unit 20 provides a constant voltage between the second node N2 and the third node N3, and controls a read current I to flow from the third node N3 to the second node N2. R The value of is measured and a read operation is performed on the memory cell 10.

[0037] FIG. 2 is a diagram for explaining the measurement of the anomalous Hall effect voltage in the memory cell of FIG.

[0038] 2, the ferromagnetic pattern 110 is made of iron (Fe) having a thickness of 2 nm, the conductive pattern 120 is made of titanium (Ti) having a thickness of 3 nm, and the free magnetic pattern 210 is made of CoFeB having a thickness of 1 nm, where the thicknesses are defined based on the third direction Z.

[0039] The ferromagnetic pattern 110 is formed by an epitaxial growth process. The ferromagnetic pattern 110 is deposited by a sputtering process on a MgO (001) oriented single crystal substrate at a temperature of about 200° C. The conductive pattern 120, the free magnetic pattern 210, and the barrier pattern 220 are deposited by a sputtering process at room temperature.

[0040] The spin-orbit torque pattern SOT has a cross shape (hall bar shape). The spin-orbit torque pattern SOT has a width of 5 μm in the first direction X and a width of 5 μm in the second direction Y, and extends long in the first direction X and the second direction Y. The magnetic tunnel junction pattern MTJ has an island structure with a width of 4 μm in the first direction X and a width of 4 μm in the second direction Y.

[0041] The opposite ends of the spin-orbit torque pattern SOT in the second direction Y are connected to a fourth node N4 and a fifth node N5, respectively. An in-plane current I flows from the first node N1 to the second node N2. SW and magnetic field B X is applied, and the Hall resistance (R H ) is measured.

[0042] Fig. 3 is a diagram showing the relationship between the magnitude of the in-plane current and the normalized Hall resistance in the memory cell of Fig. 2. Fig. 4 is a diagram showing the relationship between the magnitude of the in-plane current in the memory cell of Fig. 3 and the probability that the magnetic tunnel junction pattern of the memory cell is in a parallel state. Fig. 5 is a diagram showing the relationship between the magnitude of the magnetic field in the memory cell of Fig. 2 and the normalized Hall resistance. Fig. 6 is a diagram showing the relationship between the magnitude of the magnetic field in the memory cell of Fig. 5 and the probability that the magnetic tunnel junction pattern of the memory cell is in a parallel state.

[0043] When the magnetic tunnel junction pattern MTJ of FIG. 2 is in the parallel state, the normalized Hall resistance of FIG. 3 and FIG. 5 is 1, and when the magnetic tunnel junction pattern MTJ of FIG. 2 is in the antiparallel state, the normalized Hall resistance of FIG. 3 and FIG. 5 is −1. The probability P UP means that the magnetization direction of the free magnetic pattern 210 is in the upward direction.

[0044] 2 to 4, a magnetic field B applied to the ferromagnetic pattern 110 in an in-plane direction X X When the magnitude of the current I is fixed at 15 mT, the in-plane current I is applied to the ferromagnetic pattern 110 in the in-plane direction X. SW The probability P that the magnetization direction of the free magnetic pattern 210 is the upward direction is determined depending on the magnitude of UP changes.

[0045] Therefore, as shown in Figure 3, the in-plane current I SW When the magnitude of the current is 5.7mA, the probability that the magnetic tunnel junction pattern MTJ is in the parallel state is P UP is 0%, and the in-plane current I SW is 6.2 mA, the probability P UP is 6.5%, and the in-plane current I SW When the magnitude of the current is 6.5 mA, the probability P UP is 52.8%, and the in-plane current I SWWhen the magnitude of the current is 6.7 mA, the probability P UP is 87%, and the in-plane current I SW is 7.4 mA, the probability P UP is 100%. In-plane current I SW The probability P that the magnetization direction of the free magnetic pattern 210 is the upward direction according to the magnitude of UP have a sigmoid function relationship.

[0046] Therefore, an in-plane current I applied to the ferromagnetic pattern 110 in the in-plane direction X SW The probability P UP can be controlled from 0% to 100%.

[0047] 2, 5 and 6, an in-plane current I is applied to the ferromagnetic pattern 110 in an in-plane direction X. SW When the magnitude of the magnetic field B is fixed to 6.6 mA, the magnetic field B is applied to the ferromagnetic pattern 110 in the in-plane direction X. X The probability P that the magnetization direction of the free magnetic pattern 210 is the upward direction is determined depending on the magnitude of UP changes.

[0048] Therefore, as shown in Figure 5, the magnetic field B X When the magnitude of 1 mT, the probability P UP is 0%, and the magnetic field B X When the magnitude of the magnetic field is 10 mT, the probability P UP is 16.7%, and the magnetic field B X When the magnitude of the magnetic field is 14 mT, the probability P UP is 59.3%, and the magnetic field B X When the magnitude of the magnetic field is 16 mT, the probability P UP is 86.9%, and the magnetic field B XWhen the magnitude of the magnetic field is 20 mT, the probability P UP is 100%. Magnetic field B X The probability P that the magnetization direction of the free magnetic pattern 210 is the upward direction according to the magnitude of UP has a sigmoid function relationship.

[0049] Therefore, the magnetic field B applied to the ferromagnetic pattern 110 in the in-plane direction X X The probability P UP can be controlled from 0% to 100%.

[0050] In the probabilistic bit element according to some embodiments, the control unit 20 applies an in-plane current I to the ferromagnetic pattern 110 in an in-plane direction X. SW and the magnitude of the magnetic field B applied to the ferromagnetic pattern 110 in the in-plane direction X. X In other words, the magnetization direction of the free magnetic pattern 210 is determined by the in-plane current I SW and magnetic field B X The control unit 20 controls the ferromagnetic pattern 110 to supply an in-plane current I having a predetermined first magnitude. SW and a magnetic field B having a second predetermined magnitude. X The first magnitude and the second magnitude may be predetermined to correspond to a specific probability that the magnetization direction of the free magnetic pattern 210 is in the upward direction.

[0051] For example, the first magnitude and the second magnitude correspond to a random probability of 50% that the magnetization direction of the free magnetic pattern 210 is in a specific direction (e.g., upward direction). The control unit 20 controls the ferromagnetic pattern 110 to supply an in-plane current I having a first magnitude to the ferromagnetic pattern 110 so that the probability that the magnetization direction of the free magnetic pattern 210 is in the upward direction becomes 50%. SW and a magnetic field B having a second magnitude XThis provides a 50% probability that the magnetic tunnel junction pattern MTJ is in a specific state (e.g., parallel state), i.e., a 50% probability that the magnetic tunnel junction pattern MTJ has specific data (e.g., 0) (or a 50% probability that the magnetic tunnel junction pattern MTJ has a specific resistance value (e.g., low resistance value)).

[0052] The probabilistic bit element generates logic 0 or 1 depending on the magnetization direction 210M of the free magnetic pattern 210. For example, the probabilistic bit element generates logic 0 when the magnetization direction 210M of the free magnetic pattern 210 is in a downward direction, and generates logic 1 when the magnetization direction 210M of the free magnetic pattern 210 is in an upward direction. Therefore, the probabilistic bit element outputs logic 0 or 1 with a 50% probability.

[0053] At least one of the first magnitude and the second magnitude varies depending on the ferromagnetic pattern 110, the conductive pattern 120, and the free magnetic pattern 210. At least one of the first magnitude and the second magnitude can be predetermined based on at least one of, for example, the material of the ferromagnetic pattern 110, the magnetization strength of the ferromagnetic pattern 110, the thickness of the ferromagnetic pattern 110, the material of the conductive pattern 120, the thickness of the conductive pattern 120, the material of the free magnetic pattern 210, the magnetization strength of the free magnetic pattern 210, the thickness of the free magnetic pattern 210, etc. For example, when the ferromagnetic pattern 110 is made of iron (Fe) having a thickness of 2 nm, the conductive pattern 120 is made of titanium (Ti) having a thickness of 3 nm, and the free magnetic pattern 210 is made of CoFeB having a thickness of 1 nm, the first magnitude is 6.6 mA and the second magnitude is 13.5 mT.

[0054] The probabilistic bit element according to some embodiments can adjust the first magnitude and the second magnitude by adjusting the ferromagnetic pattern 110, the conductive pattern 120, and the free magnetic pattern 210, thereby operating at low power.

[0055] Additionally, probabilistic bit devices according to some embodiments are produced at temperatures that are highly compatible with common semiconductor processes (eg, logic fabrication processes).

[0056] Figure 7 shows the normalized Hall resistance of the memory cell of Figure 2. Figure 8 shows the results of a NIST (National Institute of Standards and Technology) test of the normalized Hall resistance of the memory cell of Figure 2.

[0057] 2 and 7, a magnetic field B of 13.5 mT is applied to the ferromagnetic pattern 110 in the in-plane direction X. X and an in-plane current I of 6.6 mA is applied to the ferromagnetic pattern 110 in the in-plane direction X. SW 2, the state in which the magnetization direction 210M of the free magnetic pattern 210 is in the upward direction and the state in which the magnetization direction 210M of the free magnetic pattern 210 is in the downward direction are output at a ratio of approximately 50:50. That is, the probability that the magnetization direction 210M of the free magnetic pattern 210 is in the upward direction is 50%. The probabilistic bit element including the memory cell 10 of FIG. 2 outputs 0 or 1 with a 50% probability.

[0058] 8, the normalized Hall resistance of the memory cell 10 of FIG. 2 passes all of the NIST tests. Therefore, the probabilistic bit element according to some embodiments including the memory cell 10 of FIG. 2 is used as a random number generation element.

[0059] Some embodiments of the probabilistic bit device can generate truly random numbers that guarantee perfect randomness, and some embodiments of the probabilistic bit device can operate at higher speeds because they include memory cells 10 based on spin-orbit torque.

[0060] FIG. 9 is a diagram for explaining the stochastic state of the magnetic tunnel junction structure of FIG.

[0061] Fig. 9 is a diagram showing the energy of the free magnetic pattern 210 in a stable state in Fig. 1. In Fig. 9, either one of the downward arrow and the upward arrow indicates a state in which the magnetization direction 210M of the free magnetic pattern 210 is parallel to the magnetization direction 230M of the fixed magnetic pattern 230 (a state in which the magnetic tunnel junction pattern MTJ is parallel), and the other indicates a state in which the magnetization direction 210M of the free magnetic pattern 210 is antiparallel to the magnetization direction 230M of the fixed magnetic pattern 230 (a state in which the magnetic tunnel junction pattern MTJ is antiparallel).

[0062] Referring to FIGS. 1 and 9, there is an energy barrier between the parallel and antiparallel states of the magnetic tunnel junction pattern MTJ.

[0063] When the free magnetic pattern 210 is in an unstable state, a low energy barrier exists between the parallel and antiparallel states of the magnetic tunnel junction pattern MTJ. Therefore, the parallel and antiparallel states of the magnetic tunnel junction pattern MTJ randomly fluctuate and are converted every very short time of several ms to several ns. In addition, the energy barrier changes sensitively depending on the thickness of the free magnetic pattern 210, the size of the magnetic tunnel junction pattern MTJ, the operating temperature of the memory cell 10, etc.

[0064] In addition, the energy E of the free magnetic pattern 210 of the magnetic tunnel junction pattern MTJ according to some embodiments is 20 kT or more, and has a stable state. Therefore, the magnetic tunnel junction pattern MTJ can stably maintain the parallel state and the antiparallel state. That is, the probabilistic bit element according to some embodiments can stably generate and output data.

[0065] 10 to 13 are diagrams illustrating probabilistic bit elements according to some embodiments. For convenience of explanation, parts that overlap with the contents explained with reference to FIGS. 1 to 8 will be briefly explained or omitted.

[0066] 10 to 13, in a probabilistic bit element according to some embodiments, the spin-orbit torque pattern SOT further includes an antiferromagnetic pattern 130. The ferromagnetic pattern 110 is disposed between the conductive pattern 120 and the antiferromagnetic pattern 130.

[0067] The antiferromagnetic pattern 130 has horizontal magnetic anisotropy. The magnetization direction 130M of the antiferromagnetic pattern 130 is the in-plane direction X. The antiferromagnetic pattern 130 fixes the magnetization direction 110M of the ferromagnetic pattern 110.

[0068] The antiferromagnetic pattern 130 includes an antiferromagnetic material, such as at least one of PtMn, IrMn, MnO, MnS, MnTe, MnF2, FeCl2, FeO, CoCl2, CoO, NiCl2, NiO, and Cr, or at least one selected from rare metals, such as ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), or silver (Ag).

[0069] Referring to FIG. 10, in a probabilistic bit element according to some embodiments, the antiferromagnetic pattern 130 extends in a first direction X.

[0070] 11 , in a probabilistic bit element according to some embodiments, an antiferromagnetic pattern 130 and a ferromagnetic pattern 110 are disposed on a portion of a conductive pattern 120. The antiferromagnetic pattern 130 and the ferromagnetic pattern 110 are aligned with the magnetic tunnel junction pattern MTJ. The antiferromagnetic pattern 130 and the ferromagnetic pattern 110 overlap the magnetic tunnel junction pattern MTJ in the third direction Z.

[0071] 12 , in a probabilistic bit element according to some embodiments, an antiferromagnetic pattern 130 and a ferromagnetic pattern 110 are disposed on a portion of a conductive pattern 120. The antiferromagnetic pattern 130 and the ferromagnetic pattern 110 are aligned with the magnetic tunnel junction pattern MTJ. The antiferromagnetic pattern 130 and the ferromagnetic pattern 110 overlap the magnetic tunnel junction pattern MTJ in the third direction Z. The conductive pattern 120 covers the side surfaces of the ferromagnetic pattern 110 and the antiferromagnetic pattern 130.

[0072] 13 is a diagram illustrating a probabilistic bit element according to some embodiments. For convenience of explanation, parts that overlap with the contents explained with reference to FIGS. 1 to 8 will be explained briefly or omitted.

[0073] 13, in a probabilistic bit device according to some embodiments, the spin-orbit torque pattern SOT further includes a ferrimagnetic pattern 140. The ferromagnetic pattern 110 is disposed between the conductive pattern 120 and the ferrimagnetic pattern 140.

[0074] The ferrimagnetic pattern 140 has horizontal magnetic anisotropy. The magnetization direction 140M of the ferrimagnetic pattern 140 is the in-plane direction X. The ferrimagnetic pattern 140 includes, for example, at least one of CoGd, CoFeGd, CoTb, CoFeTb, iron oxides, and yttrium iron garnet (YIG).

[0075] 14 is a diagram illustrating a probabilistic bit element according to some embodiments. For convenience of explanation, parts that overlap with the contents explained with reference to FIGS. 1 to 8 will be explained briefly or omitted.

[0076] 14, in a probabilistic bit element according to some embodiments, the spin-orbit torque pattern SOT further includes a composite antiferromagnetic pattern 150. The ferromagnetic pattern 110 is disposed between the conductive pattern 120 and the composite antiferromagnetic pattern 150.

[0077] The composite antiferromagnetic pattern 150 includes a first ferromagnetic pattern 151, a non-magnetic conductive pattern 152, and a second ferromagnetic pattern 153, which are stacked in order. The second ferromagnetic pattern 153 is disposed between the non-magnetic conductive pattern 152 and the ferromagnetic pattern 110.

[0078] The first ferromagnetic pattern 151 and the second ferromagnetic pattern 153 have horizontal magnetic anisotropy. The magnetization direction 151M of the first ferromagnetic pattern 151 is the same in-plane direction as the magnetization direction 110M of the ferromagnetic pattern 110. The magnetization direction 151M of the first ferromagnetic pattern 151 is the negative first direction X, and the magnetization direction 153M of the second ferromagnetic pattern 153 is the positive first direction X. The strength of the magnetization direction 151M of the first ferromagnetic pattern 151 is the same as the strength of the magnetization of the second ferromagnetic pattern 153.

[0079] The nonmagnetic conductive pattern 152 contains, for example, Ru.

[0080] 15 is a diagram illustrating a probabilistic bit element according to some embodiments. For convenience of explanation, parts that overlap with the contents explained with reference to FIGS. 1 to 8 will be explained briefly or omitted.

[0081] 15, in a probabilistic bit device according to some embodiments, the spin-orbit torque pattern SOT further includes a synthetic ferrimagnetic pattern 160. The ferromagnetic pattern 110 is disposed between the conductive pattern 120 and the synthetic ferrimagnetic pattern 160.

[0082] The composite ferrimagnetic pattern 160 includes a first ferromagnetic pattern 161, a non-magnetic conductive pattern 162, and a second ferromagnetic pattern 163, which are stacked in order. The second ferromagnetic pattern 163 is disposed between the non-magnetic conductive pattern 162 and the ferromagnetic pattern 110.

[0083] The first ferromagnetic pattern 161 and the second ferromagnetic pattern 163 have horizontal magnetic anisotropy. The magnetization direction 161M of the first ferromagnetic pattern 161 is the same in-plane direction as the magnetization direction 110M of the ferromagnetic pattern 110. The magnetization direction 161M of the first ferromagnetic pattern 161 is the negative first direction X, and the magnetization direction 163M of the second ferromagnetic pattern 163 is the positive first direction X. The strength of the magnetization direction 161M of the first ferromagnetic pattern 161 is different from the strength of the magnetization of the second ferromagnetic pattern 163.

[0084] The nonmagnetic conductive pattern 162 includes, for example, Ru.

[0085] 16 is a diagram illustrating a cell array of a magnetic memory device according to some embodiments. For convenience of explanation, parts that overlap with the contents described with reference to FIGS. 1 to 15 will be briefly described or omitted.

[0086] Referring to FIG. 16, a cell array of a magnetic memory device according to some embodiments includes a plurality of write word lines WWL, a plurality of read word lines RWL, a plurality of bit lines BL, a plurality of source lines SL, and a plurality of memory cells 10.

[0087] The memory cells 10 are arranged along a plurality of rows and a plurality of columns. The memory cells 10 in each row are connected to a pair of read word lines RWL and write word lines WWL. The memory cells 10 in each column are connected to a pair of source lines SL and bit lines BL.

[0088] In some embodiments, the memory cell 10 includes a magnetic tunnel junction pattern MTJ, a spin-orbit torque pattern SOT, a first electronic element ED1, and a second electronic element ED2.

[0089] The first electronic elements ED1 of the memory cells 10 in each row are commonly connected to a corresponding read word line RWL, the second electronic elements ED2 of the memory cells 10 in each row are commonly connected to a corresponding write word line WWL, the spin-orbit torque patterns SOT of the memory cells 10 in each column are commonly connected to a corresponding source line SL, and the first electronic elements ED1 and second electronic elements ED2 of the memory cells 10 in each column are commonly connected to a corresponding bit line BL.

[0090] The first electronic element ED1 is connected between the magnetic tunnel junction pattern MTJ and the bit line BL. The gate electrode of the first electronic element ED1 is connected to and controlled by the read word line RWL. The second electronic element ED2 is connected between a first end of the spin-orbit torque pattern SOT and the bit line BL. The gate electrode of the second electronic element ED2 is connected to and controlled by the write word line WWL. The source line SL is connected to a second end of the spin-orbit torque pattern SOT.

[0091] The first and second electronic elements ED1, ED2 each include at least one of a transistor and a diode, hi some embodiments, the first and second electronic elements ED1, ED2 each include a transistor.

[0092] The memory cell 10 corresponds to the memory cell 10 described with reference to Figures 1 to 15. For example, the first node N1 of the spin-orbit torque pattern SOT described with reference to Figures 1 to 15 is connected to the source / drain of the second electronic element ED2, the second node N2 of the spin-orbit torque pattern SOT described with reference to Figures 1 to 15 is connected to the source line SL, and the third node N3 described with reference to Figures 1 to 15 is connected to the source / drain of the first electronic element ED1.

[0093] During a read operation of the selected memory cell 10, the first electronic element ED1 is turned on and the second electronic element ED2 is turned off via the read word line RWL. During the read operation, a read current (I R) flows from the bit line BL to the source line SL. R flows through a part of the spin-orbit torque pattern SOT and the magnetic tunnel junction pattern MTJ. The read current (I in Figure 1) R ) flows through the magnetic tunnel junction pattern MTJ in a direction perpendicular to the interface where the spin-orbit torque pattern SOT and the magnetic tunnel junction pattern MTJ meet.

[0094] During a write operation of the selected memory cell 10, the second electronic element ED2 is turned on and the first electronic element ED1 is turned off via the write word line WWL. This causes an in-plane current (I SW ) flows through the spin-orbit torque pattern SOT.

[0095] 17 is a diagram illustrating a cell array of a magnetic memory device according to some embodiments. For convenience of explanation, parts that overlap with the contents described with reference to FIGS. 1 to 16 will be briefly described or omitted.

[0096] 17, in a cell array of a magnetic memory device according to some embodiments, a second electronic element ED2 is connected between a magnetic tunnel junction pattern MTJ and a first end of a spin-orbit torque pattern SOT, and a gate electrode of the second electronic element ED2 is connected to and controlled by a write word line WWL.

[0097] The first electronic elements ED1 of the memory cells 10 in each column are commonly connected to the corresponding bit line BL.

[0098] The memory cell 10 corresponds to the memory cell 10 described with reference to Figures 1 to 15. For example, the first node N1 of the spin-orbit torque pattern SOT described with reference to Figures 1 to 15 is connected to the source / drain of the second electronic element ED2, the second node N2 of the spin-orbit torque pattern SOT described with reference to Figures 1 to 15 is connected to the source line SL, and the third node N3 described with reference to Figures 1 to 15 is connected to the source / drain of the first electronic element ED1 and the source / drain of the second electronic element ED2.

[0099] 18 is a diagram illustrating a cell array of a magnetic memory device according to some embodiments. For convenience of explanation, parts that overlap with the contents described with reference to FIGS. 1 to 16 will be briefly described or omitted.

[0100] Referring to FIG. 18, in a cell array of a magnetic memory device according to some embodiments, the first electronic element ED1 includes a transistor and the second electronic element ED2 includes a diode.

[0101] Conventional software-based random number generators generate random numbers using the mid-square method, linear congruential method, etc. These random numbers are pseudo-random numbers that are periodic and have correlations between them, and can be predicted using machine learning, making conventional software-based random number generators vulnerable to security issues.

[0102] The probabilistic bit elements according to some embodiments described with reference to Figures 1 to 18 can generate truly random numbers that are unpredictable. The probabilistic bit elements according to some embodiments described with reference to Figures 1 to 18 are used in probabilistic computing elements. The probabilistic computing elements can be used to solve problems that cannot be solved by computing elements using conventional deterministic bits, such as NP-complete / hard problems, optimization using a Boltzmann machine in machine learning, the classical annealing problem, invertible Boolean logic, or the quantum Boltzmann law, using probabilistic bits generated by the probabilistic bit elements according to some embodiments.

[0103] Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to the above embodiments and can be manufactured in various different forms, and a person skilled in the art to which the present invention pertains can understand that the present invention can be embodied in other specific forms without changing the technical concept or essential features of the present invention. Therefore, the above embodiments should be understood to be illustrative in all respects and not limiting. [Explanation of symbols]

[0104] 10 memory cells 20 Control Unit 110 Ferromagnetic Pattern 120 Conductive Pattern 130 Antiferromagnetic Pattern 140 Ferrimagnetic Pattern 150 Synthetic Antiferromagnetic Patterns 160 Synthetic Ferrimagnetic Patterns 210 Free Magnetic Pattern 220 Barrier Pattern 230 Fixed magnetic pattern

Claims

1. a spin-orbit torque pattern including a stacked combination of a ferromagnetic pattern having horizontal magnetic anisotropy and a conductive pattern on the ferromagnetic pattern; a magnetic tunnel junction pattern including a stacked combination of a free magnetic pattern having perpendicular magnetic anisotropy, a barrier pattern, and a fixed magnetic pattern having perpendicular magnetic anisotropy on the spin orbit torque pattern; a control unit configured to provide an in-plane current having a predetermined first magnitude and a magnetic field having a predetermined second magnitude to the spin-orbit torque pattern in a horizontal direction parallel to a top surface of the ferromagnetic pattern, The probabilistic bit element, wherein the first magnitude and the second magnitude correspond to a predetermined probability that the magnetization direction of the free magnetic pattern is in a specific direction.

2. 2. The probabilistic bit element of claim 1, wherein the control unit is configured to provide the in-plane current having the first magnitude and the magnetic field having the second magnitude to the ferromagnetic pattern so that the magnetization direction of the free magnetic pattern has a 50% probability of being in the specific direction.

3. the spin-orbit torque pattern further includes an antiferromagnetic pattern; 2. The stochastic bit device of claim 1, wherein the ferromagnetic pattern extends between the antiferromagnetic pattern and the conductive pattern.

4. 4. The stochastic bit element according to claim 3, wherein the conductive pattern covers at least a part of the side surfaces of the ferromagnetic pattern and the antiferromagnetic pattern.

5. the conductive pattern extends in the horizontal direction; 4. The stochastic bit element of claim 3, wherein the conductive pattern and the antiferromagnetic pattern extend over a portion of the conductive pattern and overlap the magnetic tunnel junction pattern.

6. the spin-orbit torque pattern further includes a ferrimagnetic pattern; 2. The stochastic bit device of claim 1, wherein the ferromagnetic pattern extends between the ferrimagnetic pattern and the conductive pattern.

7. the spin-orbit torque pattern further comprises a composite antiferromagnetic pattern; 2. The probabilistic bit device of claim 1, wherein the ferromagnetic pattern extends between the composite antiferromagnetic pattern and the conductive pattern.

8. the spin-orbit torque pattern further comprises a synthetic ferrimagnetic pattern; 2. The stochastic bit device of claim 1, wherein the ferromagnetic pattern extends between the synthetic ferrimagnetic pattern and the conductive pattern.

9. a memory cell including a ferromagnetic pattern, a conductive pattern, a free magnetic pattern, a barrier pattern, and a fixed magnetic pattern, which are sequentially stacked; a control unit configured to provide an in-plane current and a magnetic field to the ferromagnetic pattern; the magnetization direction of the ferromagnetic pattern is horizontal; The magnetization direction of the fixed magnetic pattern is fixed in a vertical direction, A stochastic bit element, wherein the magnetization direction of the free magnetic pattern has the perpendicular direction and is variable by the in-plane current and the magnetic field.

10. a memory cell including a spin-orbit torque pattern and a magnetic tunnel junction pattern stacked in sequence; a controller configured to provide an in-plane current having a predetermined first magnitude and a magnetic field having a predetermined second magnitude to the spin-orbit torque pattern; The probabilistic bit element, wherein the first magnitude and the second magnitude correspond to a probability that the resistance of the magnetic tunnel junction pattern has a particular resistance value.

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