True random number generator and method for generating true random numbers

Abstract

The present invention discloses a true random number generator comprising a multilayer film structure, comprising: a conductive layer configured to pass a first current; a first magnetic layer located above the conductive layer, having an easy magnetization direction perpendicular to the interface between the conductive layer and the first magnetic layer, and configured such that, under the Joule heating effect of the first current, the magnetic moment of the first magnetic layer overcomes a reversal energy barrier and randomly flips in an upward or downward direction perpendicular to the interface; and a spin current cancellation layer located above the first magnetic layer, configured to cancel the spin-orbit moment generated by the spin current generated at the interface between the conductive layer and the first magnetic layer on the magnetic moment of the first magnetic layer. The true random number generator provided by the present invention, by adding the spin current cancellation layer to cancel the spin-orbit moment from the conductive layer, overcomes the problem that the magnetic moment of a perpendicular magnetization heterojunction device, under the spin-orbit coupling effect, has difficulty in flipping upward and downward with equal probability.

Description

Technical Field

[0001] The present invention relates to the technical field of information security and cryptography, and in particular to a true random number generator and a method for generating true random numbers. Background Art

[0002] Random numbers play an important role in cryptographic protocols, key management, digital signatures, and identity authentication. In the prior art, random number generators include pseudorandom number generators (PRNGs) and true random number generators (TRNGs). Pseudorandom number generators use software algorithms to generate random numbers, such as using programming languages ​​to generate random numbers, and have predictable regularity and determinism. True random number generators, on the other hand, generally use hardware to generate random numbers, for example, using the natural randomness of some physical sources, including thermal noise, radioactive decay, electronic circuit noise, light source noise, electronic oscillator frequency jitter, quantum noise, and other physical sources. These have unpredictable natural random properties and offer greater security in cryptographic applications. Currently, the true random number generators built into computer central processing units (CPUs) mostly use thermal noise as their entropy source. Due to the need to shield non-random noise (such as power supply noise) and design a low-pass amplifier circuit for random noise, they occupy a large circuit area and cause energy consumption. Moreover, the efficiency of generating random numbers by a single true random number generator is far from meeting the demand. Therefore, a true random number generator and a pseudo-random number generator are often used in combination, which in turn reduces security.

[0003] In the prior art, there are also magnetic information devices based on nanometer-thick multilayer film structures as true random number generators. They have the advantages of being electrically driven, non-volatile, radiation-resistant, and compatible with existing semiconductor integration processes. The prior art magnetic information device true random number generators include those based on the spin-transfer torque effect (STT), the spin-orbit torque effect (SOT), and low-barrier nanomagnet technology (LBNM).

[0004] Among them, the true random number generator based on the spin transfer torque effect (STT) uses a spin valve or a magnetic tunnel junction (MTJ), such as Figure 1As shown in the figure, a magnetic tunnel junction (MTJ) is a multilayer structure consisting of a free layer, an insulating layer, a reference layer, a pinned layer, and a cap layer stacked in sequence. Under thermal noise, the magnetic moment of the free layer of the MTJ is disturbed. When a spin-polarized current flows perpendicularly through the layers, the magnetic moment of the free layer is affected by a spin transfer torque. When the spin transfer torque is large enough, it induces a random reversal of the magnetic moment of the free layer. When the magnetic moment of the free layer is parallel to that of the reference layer, the MTJ exhibits a low-resistance state (logical "0"). When the magnetic moment of the free layer is antiparallel to that of the reference layer, the MTJ exhibits a high-resistance state (logical "1"), resulting in a digital string with "0" and "1" randomly distributed with equal probability.

[0005] True random number generators based on the spin transfer torque effect (STT) require a spin-polarized current to pass through a fragile oxide tunneling layer, resulting in a shorter service life. In addition, true random number generators based on the spin transfer torque effect (STT) require the write current to have precise pulse amplitude and pulse width. Therefore, the conditions for its stable generation of true random numbers are relatively harsh.

[0006] A true random number generator based on the spin-orbit coupling (SOT) effect consists of a perpendicularly magnetized heterojunction composed of a heavy metal, ferromagnetic, and non-magnetic structure. In this perpendicular heterojunction, when an in-plane current flows horizontally through the heavy metal layer, a horizontally polarized pure spin current accumulates at the interface between the ferromagnetic and heavy metal layers due to the spin-orbit coupling (SOT) effect. This generates a torque (spin-orbit torque) on the magnetic moment of the ferromagnetic layer, pulling it horizontally in the plane. Due to thermal perturbations, when the horizontal current is removed, the magnetic moment of the ferromagnetic layer of the perpendicular heterojunction randomly flips upward or downward with equal probability (50% each). Because the anomalous Hall resistance is related to the magnetic moment, the perpendicular heterojunction exhibits a high-resistance state (logical "1") and a low-resistance state (logical "0") due to the magnetic moment flipping of the ferromagnetic layer, thereby generating a random digital string with equal probability of "0" and "1".

[0007] In the process of pulling the magnetic moment of the ferromagnetic layer to the horizontal direction based on the spin-orbit coupling effect (SOT), the direction of the magnetic moment is offset to a certain extent. When the horizontal current is removed, the magnetic moment of the ferromagnetic layer in the perpendicular magnetization heterojunction is difficult to maintain an equal probability (50% each) of flipping upward or downward. Therefore, the true random number generator based on the spin-orbit coupling effect (SOT) has poor randomness. In addition, the true random number generator based on the spin-orbit coupling effect (SOT) requires the preparation of a magnetic stack device without shape offset, which has high process requirements. The current density required to generate true random numbers is also large (the horizontal current must be large enough to pull the magnetic moment of the ferromagnetic layer to the difficult-to-magnetize horizontal direction): often 10 7 -10 8 A / cm 2Above the current density, the large current passing through the perpendicular magnetized heterojunction will not only lead to excessive energy consumption, but also the thermal effect will greatly reduce the service life of the device.

[0008] The principle of generating true random numbers using low-barrier nanomagnet technology (LBNM) is that, in the presence of ambient thermal noise, the magnetic moment of a low-barrier nanoperpendicular magnet undergoes a continuous, uncontrollable, random upward or downward flip. The frequency of this flip depends on the frequency of the ambient thermal noise, and the ability to flip depends on the energy amplitude of the thermal noise. The occurrence of this flip is interpreted as a logical "1" or a logical "0." True random number generators based on LBNM technology cannot store generated random numbers in situ, which affects data reuse. Furthermore, random number generation passively relies on ambient noise, resulting in slow generation and an unstable frequency. Summary of the Invention

[0009] In view of at least one drawback of the prior art, the present invention provides a true random number generator comprising a multi-layer film structure, wherein the multi-layer film structure comprises:

[0010] a conductive layer configured to pass a first current;

[0011] a first magnetic layer located on the conductive layer, having an easy magnetization direction perpendicular to an interface between the conductive layer and the first magnetic layer, and configured such that, under the action of Joule heat of the first current, the magnetic moment of the first magnetic layer overcomes a reversal energy barrier and randomly flips in an upward or downward direction perpendicular to the interface;

[0012] The spin current compensation layer is located on the first magnetic layer and is used to compensate the spin-orbit moment generated by the spin current generated at the interface between the conductive layer and the first magnetic layer on the magnetic moment of the first magnetic layer.

[0013] According to one aspect of the present invention, the multilayer film structure further comprises:

[0014] substrate; the conductive layer is located on the substrate;

[0015] A cap layer is located above the spin current compensation layer and is used to protect the layers below it;

[0016] The conductive layer is in a cross shape, the first magnetic layer, the spin current compensation layer and the cap layer are thin films with the same cross-sectional shape, and the first magnetic layer, the spin current compensation layer and the cap layer are stacked in the central area of ​​the cross shape.

[0017] According to one aspect of the present invention, with the geometric center of the cross as the plane rectangular coordinate origin, one extending direction of the cross as the X-axis, and the other extending direction as the Y-axis, the conductive layer is further configured as follows:

[0018] Electrodes are respectively connected to both ends of the conductive layer along the X-axis for passing the first current;

[0019] Electrodes are respectively connected to both ends of the conductive layer along the Y axis for detecting Hall voltage.

[0020] According to one aspect of the present invention, the first current comprises a pulse current.

[0021] Furthermore, the Hall voltage is detected between adjacent pulse periods of the pulse current to obtain a random number sequence.

[0022] According to one aspect of the present invention, in the true random number generator:

[0023] The substrate comprises a silicon substrate;

[0024] The conductive layer is made of heavy metal material or topological insulator material;

[0025] The first magnetic layer is made of ferromagnetic material;

[0026] The spin current compensation layer is made of the same material as the conductive layer; and / or

[0027] The cap layer is made of non-ferrous conductive metal material.

[0028] According to one aspect of the present invention, the multilayer film structure further comprises:

[0029] a substrate, the conductive layer being located on the substrate;

[0030] a second magnetic layer, located on the spin current compensation layer, and having an easy magnetization direction perpendicular to an interface between the spin current compensation layer and the second magnetic layer;

[0031] a pinning layer, located on the second magnetic layer, for fixing the magnetic moment direction of the second magnetic layer;

[0032] A capping layer is located above the pinning layer and is used to protect the layers below it;

[0033] The conductive layer is in the shape of a strip, the first magnetic layer, the spin current compensation layer, the second magnetic layer, the pinning layer and the capping layer are thin films with the same cross-sectional shape, and the first magnetic layer, the spin current compensation layer, the second magnetic layer, the pinning layer and the capping layer are stacked in the central area of ​​the strip.

[0034] According to one aspect of the present invention, the geometric center of the strip is taken as the origin of the three-dimensional rectangular coordinate, the extending direction of the strip is taken as the X-axis, and the Z-axis is perpendicular to the X-axis and along the stacking direction of the multilayer film structure.

[0035] Electrodes are respectively connected to both ends of the conductive layer along the X-axis for passing the first current;

[0036] An electrode is connected to one end of the cap layer along the Z axis for passing a second current.

[0037] According to one aspect of the present invention, the first current comprises a pulse current with a preset interval,

[0038] The second current is passed at the preset interval to measure the magnetoresistance of the multilayer film structure, and a random number sequence is obtained according to the magnetoresistance.

[0039] According to one aspect of the present invention, in the true random number generator:

[0040] The substrate comprises a silicon substrate;

[0041] The conductive layer is made of heavy metal material or topological insulator material;

[0042] The first magnetic layer is made of soft magnetic material;

[0043] The spin current compensation layer is made of the same material as the conductive layer;

[0044] The second magnetic layer is made of ferromagnetic material;

[0045] The pinning layer is made of antiferromagnetic material; and / or

[0046] The cap layer is made of non-ferrous conductive metal material.

[0047] According to one aspect of the present invention, in the true random number generator:

[0048] The current intensity and / or pulse width of the first current is determined according to the switching energy barrier of the first magnetic layer.

[0049] According to one aspect of the present invention, in the true random number generator:

[0050] The pulse period of the first current determines the rate of generating true random numbers.

[0051] The present invention also provides a method for generating true random numbers using the true random number generator as described above, wherein the multilayer film structure further comprises:

[0052] a substrate, the conductive layer being located on the substrate;

[0053] A cap layer is located above the spin current compensation layer and is used to protect the layers below it;

[0054] The conductive layer is in a cross shape, the first magnetic layer, the spin current cancellation layer, and the cap layer are thin films with the same cross-sectional shape, and the first magnetic layer, the spin current cancellation layer, and the cap layer are stacked in the central area of ​​the cross shape;

[0055] With the geometric center of the cross as the plane rectangular coordinate origin, one extending direction of the cross as the X-axis, and the other extending direction as the Y-axis, the conductive layer is further configured as follows:

[0056] Electrodes are respectively connected to both ends of the conductive layer along the X-axis for passing the first current;

[0057] Electrodes are respectively connected to both ends of the conductive layer along the Y axis for detecting the Hall voltage;

[0058] The method comprises:

[0059] A pulse current is introduced along the X-axis direction;

[0060] A Hall voltage is detected between adjacent pulse periods of the pulse current along the Y-axis direction, and a random number sequence is obtained according to the Hall voltage.

[0061] The present invention also provides a method for generating true random numbers using the true random number generator as described above, wherein the multilayer film structure further comprises:

[0062] a substrate, the conductive layer being located on the substrate;

[0063] a second magnetic layer, located on the spin current compensation layer, and having an easy magnetization direction perpendicular to an interface between the spin current compensation layer and the second magnetic layer;

[0064] a pinning layer, located on the second magnetic layer, for fixing the magnetic moment direction of the second magnetic layer;

[0065] A capping layer is located above the pinning layer and is used to protect the layers below it;

[0066] The conductive layer is in a strip shape, the first magnetic layer, the spin current cancellation layer, the second magnetic layer, the pinning layer, and the capping layer are thin films having the same cross-sectional shape, and the first magnetic layer, the spin current cancellation layer, the second magnetic layer, the pinning layer, and the capping layer are stacked in a central region of the strip;

[0067] The geometric center of the strip is taken as the origin of the three-dimensional rectangular coordinate, the extending direction of the strip is taken as the X-axis, and the Z-axis is perpendicular to the X-axis and along the stacking direction of the multilayer film structure.

[0068] Electrodes are respectively connected to both ends of the conductive layer along the X-axis for passing the first current;

[0069] An electrode is connected to one end of the cap layer along the Z axis for passing a second current;

[0070] The method comprises:

[0071] A pulse current with a preset interval is introduced along the X-axis direction;

[0072] The second current is passed along the Z axis at the preset interval to measure the magnetoresistance of the multilayer film structure, and a random number sequence is obtained according to the magnetoresistance.

[0073] According to one aspect of the present invention, in the method for generating true random numbers:

[0074] The Joule heat generated by the first current in one pulse period is greater than the energy required for the magnetic moment of the first magnetic layer to be switched.

[0075] According to one aspect of the present invention, in the method for generating true random numbers:

[0076] The Joule heat generated by the second current within the preset interval is smaller than the energy required for the magnetic moment of the first magnetic layer to be switched.

[0077] According to one aspect of the present invention, the method further comprises:

[0078] By controlling the pulse period of the first current, the rate of generating true random numbers is controlled.

[0079] The present invention provides a true random number generator comprising a multilayer film structure and a method for generating true random numbers. The Joule heating effect of an electric current is used to drive the magnetic moment of a magnetic layer to undergo random reversal. One reversal cycle can generate a random bit, and the magnetic moment can maintain its state after the current is removed. The generated random bit is non-volatile and readable. By adding a spin current cancellation layer, the spin-orbit moment from the conductive layer is offset, overcoming the problem that the magnetic moment of a perpendicular magnetized heterojunction device under the spin-orbit coupling effect is difficult to flip upward and downward with equal probability, and the stability of the generated random numbers is higher. Compared with low-barrier nanomagnet technology, the moment of magnetic moment reversal is actively controlled by applying a small current, and the rate of random number generation is controlled by adjusting the current pulse width, which is more proactive. The true random number generator provided by the present invention has a simple structure, a small device size, low energy consumption, is easy to integrate into various portable devices, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without exceeding the scope of protection required by this application.

[0081] Figure 1 A true random number generator based on the spin transfer effect in the prior art is shown;

[0082] Figure 2 The multilayer film structure in the true random number generator provided by one embodiment of the present invention is shown;

[0083] Figure 3A The multilayer film structure in the true random number generator provided by one embodiment of the present invention is shown;

[0084] Figure 3B Shown Figure 3A A top view of the conductive layer in the multilayer film structure shown;

[0085] Figure 4 FIG. 1 shows the pulse current passed into the true random number generator provided by one embodiment of the present invention;

[0086] Figure 5A The multilayer film structure in the true random number generator provided by one embodiment of the present invention is shown;

[0087] Figure 5B Shown Figure 5A A top view of the conductive layer in the multilayer film structure shown;

[0088] Figure 6 A method for generating true random numbers provided by an embodiment of the present invention is shown;

[0089] Figure 7 A method for generating true random numbers provided by an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0090] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0091] The embodiments of the present application are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only intended to help understand the method and core ideas of the present application. At the same time, changes or modifications made by those skilled in the art based on the ideas of the present application, the specific implementation methods, and the scope of application of the present application, all fall within the scope of protection of the present application. In summary, the contents of this specification should not be construed as limiting the present application.

[0092] This invention provides a true random number generator with a multilayer film structure. By adding a spin current cancellation layer, the spin-orbit coupling effect produced by conventional magnetic stack structures is offset. In a multilayer film structure without spin-orbit coupling, Joule heating is generated by applying a small current to overcome the reversal energy barrier of the magnetic layer's magnetic moment, thereby actively controlling the reversal moment and state of the magnetic moment.

[0093] According to one embodiment of the present invention, Figure 2 As shown, the present invention provides a true random number generator including a multilayer film structure 100, wherein the multilayer film structure 100 includes a conductive layer 110, a first magnetic layer 120 and a spin current compensation layer 130.

[0094] The conductive layer 110 is configured to pass a first current of a predetermined intensity.

[0095] The first magnetic layer 120 is located on the conductive layer 110, and its easy magnetization direction is perpendicular to the interface between the conductive layer 110 and the first magnetic layer 120. The first magnetic layer 120 is configured such that, under the action of Joule heat of the first current, the magnetic moment of the first magnetic layer 120 overcomes the reversal energy barrier and randomly flips in an upward or downward direction perpendicular to the interface.

[0096] The spin current compensation layer 130 is located on the first magnetic layer 120 and is used to compensate the spin-orbit moment of the first magnetic layer 120 caused by the spin current generated at the interface between the conductive layer 110 and the first magnetic layer 120 .

[0097] The first magnetic layer 120 is made of magnetocrystalline material with magnetic anisotropy, and the magnetization curve varies with the direction of the crystal axis. The external magnetic field required to reach the saturation magnetization state in some directions is the smallest, which is called the easy magnetization direction. When the magnetocrystalline material is magnetized in the easy magnetization direction, the magnetic potential energy is the lowest; the external magnetic field required to reach the saturation magnetization state in other directions is the largest, which is called the difficult magnetization direction. When the magnetocrystalline material is magnetized in the difficult magnetization direction, the magnetic potential energy is the highest.

[0098] When formed into a thin film, the first magnetic layer 120 is primarily affected by shape anisotropy (demagnetization energy), with its easy magnetization direction parallel to the film surface. When the first magnetic layer 120 is combined with the conductive layer 110 (optionally, the conductive layer 110 is made of a heavy metal or a topological insulator), due to the interface effect, the conductive layer 110 induces the easy magnetization direction of the first magnetic layer 110 to be perpendicular to the interface between the first magnetic layer 120 and the conductive layer 110.

[0099] After a first current is passed through the conductive layer 110, the Joule heating effect of the first current causes the magnetic moment of the first magnetic layer 120 to randomly flip. The magnetic moment of the first magnetic layer 120 flips toward the direction of lowest magnetic potential energy, i.e., it randomly flips upward or downward along the easy magnetization direction, perpendicular to the interface between the conductive layer 110 and the first magnetic layer 120. Optionally, the first magnetic layer 120 is fabricated as a single-domain two-state magnetic device, i.e., the magnetic moment of the first magnetic layer 120 is oriented in the same direction at the same time. Using the magnetic moment direction of the first magnetic layer 120 as the information carrier, true random numbers are generated through the randomness of magnetic moment flipping. Thermal disturbances are a true random entropy source in nature. Therefore, the probability of the magnetic moment of the first magnetic layer 120 flipping to either the upward or downward direction, perpendicular to the interface between the conductive layer 110 and the first magnetic layer 120, is 50%. Different magnetic moment directions correspond to different Hall resistances. By measuring the Hall resistance, a true random number sequence can be obtained.

[0100] However, at the interface between the first magnetic layer 120 and the conductive layer 110, electrons are asymmetrically scattered due to the spin-orbit coupling effect (SOT), accumulating single-spin electrons at the interface between the first magnetic layer 120 and the conductive layer 110. These single-spin electrons, through their spin-orbit moment, change the direction of the magnetic moment of the first magnetic layer 120, pulling the magnetic moment of the first magnetic layer 120 from perpendicular to the interface between the first magnetic layer 120 and the conductive layer 110 to parallel to the interface. During this process, the magnetic moment of the first magnetic layer 120 shifts, resulting in the inability to flip to an upward or downward direction perpendicular to the interface with equal probability (50% each) even after the first current is removed.

[0101] The above-described embodiment of the present invention incorporates a spin current cancellation layer 130 to offset the torque generated by electron spin. The spin current cancellation layer 130 is fabricated on the first magnetic layer 120. When a first current flows through the conductive layer 110, current also flows through the spin current cancellation layer 130. Due to the spin-orbit coupling effect (SOT), electrons are asymmetrically scattered, and electrons with a single spin direction accumulate at the interface between the first magnetic layer 120 and the spin current cancellation layer 130. Optionally, the spin current cancellation layer 130 is made of the same material as the conductive layer 110. By adjusting the growth thickness of the spin current cancellation layer 130, the spin-orbit moments generated at the upper and lower interfaces of the first magnetic layer 120 are equal in magnitude and opposite in direction. This allows the spin-orbit moments at the upper and lower interfaces to cancel each other out, resulting in the magnetic moment of the first magnetic layer 120 undergoing random flipping only under thermal disturbances.

[0102] According to one embodiment of the present invention, Figure 3A As shown, in the true random number generator provided by the present invention, the multilayer film structure 100 further includes a substrate 140 and a cap layer 150.

[0103] The capping layer 150 is located on the spin current compensation layer 130 and is used to protect the multi-layer film structure 100 .

[0104] like Figure 3B As shown ( Figure 3B (Figure 1 is a top view of the multilayer film structure 100 of this embodiment.) The conductive layer 110 is in a cross-shaped (Hall Bar structure), and the first magnetic layer 120, spin current compensation layer 130, and cap layer 150 are thin films with the same cross-sectional shape. The conductive layer 110, first magnetic layer 120, spin current compensation layer 130, and cap layer 150 are sequentially fabricated on a substrate 140. These layers are then etched to form a stacked structure in the center of the cross-shaped structure.

[0105] According to one embodiment of the present invention, Figure 3B As shown, with the geometric center of the cross as the plane rectangular coordinate origin, one extending direction of the cross as the X axis, and the other extending direction as the Y axis, the conductive layer 110 is further configured as follows:

[0106] Electrodes are connected to both ends of the conductive layer 110 along the X-axis for supplying the first current. The Joule heat generated by the first current causes the magnetic moment of the first magnetic layer 120 to overcome the reversal energy barrier and randomly flip upward or downward perpendicular to the interface between the first magnetic layer 120 and the conductive layer 110.

[0107] Electrodes are connected to both ends of the conductive layer 110 along the Y-axis to detect the Hall voltage. The resistance of the multilayer film structure 100 in the Y-axis direction (Hall resistance) is related to the direction of the magnetic moment of the first magnetic layer 120. After the magnetic moment of the first magnetic layer 120 is randomly flipped, two different Hall voltages can be detected along the Y-axis. The ratio of the detected Hall voltage to the first current is the Hall resistance value. The two different Hall resistance values ​​are defined as logic "0" and logic "1", respectively. Repeating this operation can output a random number sequence.

[0108] According to one embodiment of the present invention, the true random number generator provided by the present invention is further configured to:

[0109] Along Figure 3B The X-axis shown in FIG is a pulse current with high amplitude and a pulse current with low amplitude that are periodically alternating (e.g. Figure 4 As shown). The Joule heat generated by a high-amplitude pulse current during a pulse period T is greater than the energy required for the magnetic moment of the first magnetic layer 120 to undergo a random reversal; the Joule heat generated by a low-amplitude pulse current during a pulse period T is less than the energy required for the magnetic moment of the first magnetic layer 120 to undergo a random reversal. Within a pulse period T, a high-amplitude pulse current is applied to cause the magnetic moment of the first magnetic layer 120 to overcome the reversal energy barrier and undergo a random reversal, either upward or downward, perpendicular to the interface. Due to the characteristics of the first magnetic layer 120, the direction of the magnetic moment does not change after the first magnetic layer 120 is magnetized. Within this pulse period T, a low-amplitude pulse current is applied again to detect the Hall voltage in the Y-axis direction. By measuring the Hall voltage in the Y-axis direction, the Hall resistance value can be obtained, and a random number can be output. Within the next pulse period T, a high-amplitude pulse current is applied to magnetize the first magnetic layer 120 again, causing the direction of the magnetic moment to undergo a random reversal. Subsequently, a low-amplitude current is applied to detect the Hall voltage in the Y-axis direction. This repeated operation periodically outputs a random number sequence.

[0110] According to one embodiment of the present invention, in the multilayer film structure 100 of a true random number generator, the substrate 140 comprises a silicon substrate or other material with low surface roughness. The conductive layer 110 is made of a material with a strong spin coupling effect, optionally including heavy metal materials such as Pt, Ta, and W; topological insulator materials such as Bi2Se3, Sb2Te3, and Bi2Te3; and novel materials such as MoS2 and PtTe2. The first magnetic layer 120 is made of a material with a low damping coefficient, low coercivity, and magnetic anisotropy, optionally including a ferromagnetic material. The spin current cancellation layer 130 is made of a material with the same spin Hall angle as the conductive layer 110, and the spin torque generated by the conductive layer 110 is offset by adjusting the growth thickness. The cap layer 150 is made of a non-ferrous conductive metal material, optionally including Ta, Ti, or Cu.

[0111] According to one embodiment of the present invention, Figure 5A As shown, in the true random number generator provided by the present invention, the multilayer film structure 100 further includes: a substrate 140, a cap layer 150, an insulating barrier layer 160, a second magnetic layer 170 and a pinning layer 180.

[0112] The insulating barrier layer 160 is located on the spin current compensation layer 130. The first magnetic layer 120, the insulating barrier layer 160, and the second magnetic layer 170 form a "sandwich" structure of a magnetic tunnel junction (MTJ), which is used to generate the magnetic resistance of the magnetic tunnel junction (MTJ).

[0113] The second magnetic layer 170 is located on the insulating barrier layer 160, and its easy magnetization direction is perpendicular to the interface between the insulating barrier layer 160 and the second magnetic layer 170. The pinning layer 180 is located on the second magnetic layer 170 and is used to fix the magnetic moment direction of the second magnetic layer 170.

[0114] The capping layer 150 is located on the pinning layer 180 and is used to protect the multi-layer film structure 100 .

[0115] The conductive layer 110 is in the shape of a strip, and the first magnetic layer 120, the spin current compensation layer 130, the insulating barrier layer 160, the second magnetic layer 170, the pinned layer 180, and the capping layer 150 are thin films with the same cross-sectional shape. The conductive layer 110, the first magnetic layer 120, the spin current compensation layer 130, the insulating barrier layer 160, the second magnetic layer 170, the pinned layer 180, and the capping layer 150 are sequentially fabricated on a substrate 140. These layers are then etched so that the first magnetic layer 120, the spin current compensation layer 130, the insulating barrier layer 160, the second magnetic layer 170, the pinned layer 180, and the capping layer 150 are stacked in the center of the strip.

[0116] According to one embodiment of the present invention, Figure 5A As shown, with the geometric center of the strip as the origin of the three-dimensional rectangular coordinate, the extending direction of the strip as the X-axis, and the Z-axis perpendicular to the X-axis and along the stacking direction of the multilayer film structure 100 as the Z-axis, the multilayer film structure 100 is further configured as follows:

[0117] Electrodes are connected to both ends of the conductive layer 110 along the X axis for passing the first current; and an electrode is connected to one end of the cap layer 150 along the Z axis for passing the second current.

[0118] According to one embodiment of the present invention, a pulse current with a preset interval is introduced along the X-axis direction. At both ends of the strip-shaped conductive layer 110, as shown in FIG. Figure 5A The T1 and T2 terminals shown in the figure are connected to electrodes respectively for passing a first current with a preset interval. The heat generated by the first current in one pulse cycle is greater than the energy required for random reversal of the magnetic moment of the first magnetic layer 120.

[0119] The second current is passed along the Z-axis direction at the preset interval to measure the magnetoresistance of the multilayer film structure 100 and obtain a random number sequence based on the magnetoresistance. Figure 5A As shown in the figure, a second current is applied to the T1 terminal of the conductive layer 110 and the T3 terminal of the cap layer 150. The Joule heat generated by the second current within one cycle (the preset interval of the first current) is insufficient to cause the magnetic moment of the first magnetic layer 120 to overcome the reversal energy barrier and reverse, that is, the direction of the magnetic moment of the first magnetic layer 120 remains unchanged. The second magnetic layer 170 has magnetic anisotropy. Under the guidance of the pinning layer 180, the magnetic moment of the second magnetic layer 170 is fixed in an upward or downward direction perpendicular to the interface between the second magnetic layer 170 and the pinning layer 180. When the first current is applied, the magnetic moment of the first magnetic layer 120 randomly reverses in an upward or downward direction perpendicular to the interface between the first magnetic layer 120 and the conductive layer 110. At this time, the magnetic moments of the first magnetic layer 110 and the second magnetic layer 170 are either parallel or antiparallel. Due to the tunneling magnetoresistance effect, a lower magnetoresistance is measured when the magnetic moments of the first magnetic layer 110 and the second magnetic layer 170 are parallel; a higher magnetoresistance is measured when the magnetic moments of the first magnetic layer 110 and the second magnetic layer 170 are antiparallel. During the interval between the removal of the first current, the second current is passed through a preset interval, and the magnetoresistance of the multilayer film structure 100 is measured. The two different magnetoresistance values ​​are defined as logic "0" and logic "1," respectively, to output a random number sequence.

[0120] Figure 5B FIG. 1 shows a top view of the conductive layer 110 in the above embodiment of the present invention.

[0121] According to one embodiment of the present invention, Figure 5AIn the multilayer film structure 100 of the true random number generator shown, the substrate 140 includes a silicon substrate or other material with low surface roughness. The conductive layer 110 is made of a metal material with low spin-orbit coupling, optionally including metal materials Cu and Zr. The first magnetic layer 120 is made of a material with a small damping coefficient, low coercivity, and magnetic anisotropy, and a low magnetic moment reversal energy barrier, optionally including Co, CoFe alloy, CoNiCo, or CoAuCo multilayer soft magnetic material. The spin current cancellation layer 130 is made of a material with the same spin Hall angle as the conductive layer 110, and offsets the spin-orbit coupling generated by the conductive layer 110 by generating spin-orbit moments of equal magnitude and opposite direction. The insulating barrier layer 160 is made of a metal oxide material, optionally including Al2O3. On the one hand, the insulating barrier layer 160 induces the first ferromagnetic layer 120 to have magnetic anisotropy perpendicular to the interface through the interface effect; on the other hand, it also serves as the insulating layer of the magnetic tunnel junction (MTJ) (a "sandwich" structure consisting of the first magnetic layer, the insulating layer, and the second magnetic layer). The second magnetic layer 170 is made of a material with a large damping coefficient, high coercive force, and magnetic anisotropy, optionally including a ferromagnetic material. The pinning layer 180 is made of an antiferromagnetic material, optionally including IrMn or NiMn. The cap layer 150 is made of a non-ferrous conductive metal material, optionally including Ta, Ti, or Cu.

[0122] According to one embodiment of the present invention, the heat generated by the first current in one pulse period is greater than the energy required for random reversal of the magnetic moment of the first magnetic layer 120. Therefore, the current intensity and pulse width of the first current are determined according to the reversal energy barrier of the magnetic moment of the first magnetic layer 120.

[0123] According to one embodiment of the present invention, when the first current is applied, the magnetic moment of the first magnetic layer 120 is randomly flipped. Between two pulses or during the interval when the pulse current is removed, a random number can be obtained by detecting the Hall voltage or the magnetic resistance of the magnetic tunnel junction. Therefore, by controlling the pulse interval of the first current, the rate of generating true random numbers can be controlled.

[0124] The true random number generator provided by the present invention, which includes a multilayer film structure, uses the Joule heating effect of the current to drive the magnetic moment of the magnetic layer to randomly flip. One flip cycle can generate a random bit, and the magnetic moment can still maintain its state after the current is removed. The generated random bit is non-volatile and readable. By adding a spin current cancellation layer, the spin-orbit moment from the conductive layer is offset, overcoming the problem that the magnetic moment of the perpendicular magnetized heterojunction device under the spin-orbit coupling effect is difficult to flip up and down with equal probability, and the stability of the generated random numbers is higher. Compared with low-barrier nanomagnet technology, the moment of magnetic moment flipping is actively controlled by applying a small current, and the rate of random number generation is controlled by adjusting the current pulse width, which is more proactive. The true random number generator provided by the present invention has a simple structure, small device size, low energy consumption, and is easy to integrate into various portable devices, with good application prospects.

[0125] According to one embodiment of the present invention, Figure 6 As shown, the present invention also provides a method 10 for generating random numbers using the true random number generator as described above, wherein the multilayer film structure further comprises:

[0126] substrate;

[0127] A capping layer is located on the spin current compensation layer and is used to protect the multilayer film structure; wherein

[0128] The conductive layer is in a cross shape, and the first magnetic material layer, the spin current compensation layer, and the cap layer are thin films with the same cross-sectional shape. The conductive layer, the first magnetic material layer, the spin current compensation layer, and the cap layer are sequentially prepared on the substrate, and the first magnetic material layer, the spin current compensation layer, and the cap layer are stacked in the center area of ​​the cross shape by etching;

[0129] With the geometric center of the cross as the plane rectangular coordinate origin, one extending direction of the cross as the X-axis, and the other extending direction as the Y-axis, the conductive layer is further configured as follows:

[0130] Electrodes are respectively connected to both ends of the conductive layer along the X-axis for passing the first current;

[0131] Electrodes are respectively connected to both ends of the conductive layer along the Y axis for detecting the Hall voltage;

[0132] Method 10 includes step S101 and step S102, wherein:

[0133] In step S101, a pulse current is introduced along the X-axis direction, wherein the pulse current includes a high-amplitude pulse current and a low-amplitude pulse current that alternate periodically.

[0134] In step S102, Hall voltages are detected between adjacent pulse periods of the pulse current along the Y-axis, and a random number sequence is obtained based on the Hall voltages. The adjacent pulse periods include adjacent pulse periods of a high-amplitude pulse current that causes the magnetic moment of the first magnetic layer to flip (i.e., the Hall voltage is detected during the intervals between the high-amplitude pulse currents). By passing a high-amplitude pulse current to randomly flip the magnetic moment of the first magnetic layer, and by passing a low-amplitude pulse current to detect the Hall voltage along the Y-axis, a Hall resistance value is obtained, and a random number is output.

[0135] According to one embodiment of the present invention, Figure 7 As shown, the present invention also provides a method 20 for generating random numbers using the true random number generator as described above, wherein the multilayer film structure further comprises:

[0136] substrate;

[0137] a second magnetic material layer, located on the spin current compensation layer, and having an easy magnetization direction perpendicular to an interface between the spin current compensation layer and the second magnetic material layer;

[0138] a pinning layer, located on the second magnetic material layer, for fixing the magnetic moment direction of the second magnetic material layer;

[0139] A capping layer is located on the pinning layer and is used to protect the multilayer film structure;

[0140] The conductive layer is in a strip shape, and the first magnetic material layer, the spin current cancellation layer, the second magnetic material layer, the pinning layer, and the capping layer are thin films having the same cross-sectional shape. The conductive layer, the first magnetic material layer, the spin current cancellation layer, the second magnetic material layer, the pinning layer, and the capping layer are sequentially prepared on the substrate, and the first magnetic material layer, the spin current cancellation layer, the second magnetic material layer, the pinning layer, and the capping layer are stacked in the center area of ​​the strip by etching;

[0141] The geometric center of the strip is taken as the origin of the three-dimensional rectangular coordinate, the extending direction of the strip is taken as the X-axis, and the Z-axis is perpendicular to the X-axis and along the stacking direction of the multilayer film structure.

[0142] Writing electrodes are respectively connected to both ends of the conductive layer along the X axis for passing the first current;

[0143] A reading electrode is connected to one end of the cap layer along the Z axis for passing a second current;

[0144] Method 20 includes step S201 and step S202, wherein:

[0145] In step S201, a pulse current with a preset interval is introduced along the X-axis direction;

[0146] In step S202, the second current is passed along the Z-axis direction at the preset interval to measure the magnetoresistance of the multilayer film structure, and a random number sequence is obtained according to the magnetoresistance.

[0147] According to one embodiment of the present invention, in the method for generating true random numbers provided by the present invention, the Joule heat generated by the first current in one pulse period is greater than the energy required for the magnetic moment of the first magnetic material layer to be reversed.

[0148] According to an embodiment of the present invention, in the method for generating true random numbers provided by the present invention, the Joule heat generated by the second current within the preset interval is less than the energy required for the magnetic moment of the first magnetic material layer to be flipped.

[0149] According to one embodiment of the present invention, the method for generating true random numbers provided by the present invention further includes:

[0150] By controlling the preset interval, the frequency of random number generation is controlled.

Claims

1. A true random number generator comprising a multilayer film structure, characterized in that: The multilayer film structure comprises: a conductive layer configured to pass a first current; a first magnetic layer located on the conductive layer, having an easy magnetization direction perpendicular to an interface between the conductive layer and the first magnetic layer, and configured such that, under the action of Joule heat of the first current, the magnetic moment of the first magnetic layer overcomes a reversal energy barrier and randomly flips in an upward or downward direction perpendicular to the interface; A spin current compensation layer is located above the first magnetic layer. The spin current compensation layer is made of the same material as the conductive layer and is used to offset the spin-orbit moment generated by the spin current generated at the interface between the conductive layer and the first magnetic layer on the magnetic moment of the first magnetic layer.

2. The true random number generator of claim 1 , wherein the multilayer film structure further comprises: a substrate, the conductive layer being located on the substrate; a cap layer, located on the spin current compensation layer and used to protect the layers thereunder; in The conductive layer is in a cross shape, the first magnetic layer, the spin current compensation layer and the cap layer are thin films with the same cross-sectional shape, and the first magnetic layer, the spin current compensation layer and the cap layer are stacked in the central area of ​​the cross shape.

3. The true random number generator of claim 2 , wherein the geometric center of the cross is used as the plane rectangular coordinate origin, one extending direction of the cross is used as the X-axis, and the other extending direction of the cross is used as the Y-axis, and the conductive layer is further configured as follows: Electrodes are respectively connected to both ends of the conductive layer along the X-axis for passing the first current; Electrodes are respectively connected to both ends of the conductive layer along the Y axis for detecting the Hall voltage.

4. The true random number generator of claim 3, wherein the first current comprises a pulse current, and the Hall voltage is detected between adjacent pulse periods of the pulse current to obtain a random number sequence.

5. A true random number generator as claimed in any one of claims 2 to 4, wherein The substrate comprises a silicon substrate; The conductive layer is made of heavy metal material or topological insulator material; The first magnetic layer is made of ferromagnetic material; and / or The cap layer is made of non-ferrous conductive metal material.

6. The true random number generator of claim 1 , wherein the multilayer film structure further comprises: a substrate, the conductive layer being located on the substrate; a second magnetic layer, located on the spin current compensation layer, and having an easy magnetization direction perpendicular to an interface between the spin current compensation layer and the second magnetic layer; a pinning layer, located on the second magnetic layer, for fixing the magnetic moment direction of the second magnetic layer; a capping layer, located on the pinning layer and used to protect the layers thereunder; in The conductive layer is in the shape of a strip, the first magnetic layer, the spin current compensation layer, the second magnetic layer, the pinning layer and the capping layer are thin films with the same cross-sectional shape, and the first magnetic layer, the spin current compensation layer, the second magnetic layer, the pinning layer and the capping layer are stacked in the central area of ​​the strip.

7. The true random number generator according to claim 6, wherein the geometric center of the strip is the origin of the three-dimensional rectangular coordinate, the extending direction of the strip is the X-axis, and the Z-axis is perpendicular to the X-axis and along the stacking direction of the multilayer film structure. Electrodes are respectively connected to both ends of the conductive layer along the X-axis for passing the first current; An electrode is connected to one end of the cap layer along the Z axis for passing a second current.

8. The true random number generator of claim 7, wherein the first current comprises a pulse current having a preset interval, the second current is passed at the preset interval to measure the magnetoresistance of the multilayer film structure, and a random number sequence is obtained based on the magnetoresistance.

9. A true random number generator as claimed in any one of claims 6 to 8, wherein The substrate comprises a silicon substrate; The conductive layer is made of heavy metal material or topological insulator material; The first magnetic layer is made of soft magnetic material; The spin current compensation layer is made of the same material as the conductive layer; The second magnetic layer is made of ferromagnetic material; The pinning layer is made of antiferromagnetic material; and / or The cap layer is made of non-ferrous conductive metal material.

10. The true random number generator according to claim 4 or 8, wherein The current intensity and / or pulse width of the first current is determined according to the switching energy barrier of the first magnetic layer.

11. The true random number generator of claim 4 or 8, wherein The pulse period of the first current determines the rate of generating true random numbers.

12. A method for generating true random numbers using the true random number generator according to any one of claims 1 to 11, characterized in that: The multilayer film structure further comprises: a substrate, the conductive layer being located on the substrate; A cap layer is located above the spin current compensation layer and is used to protect the layers below it; The conductive layer is in a cross shape, the first magnetic layer, the spin current cancellation layer, and the cap layer are thin films with the same cross-sectional shape, and the first magnetic layer, the spin current cancellation layer, and the cap layer are stacked in the central area of ​​the cross shape; With the geometric center of the cross as the plane rectangular coordinate origin, one extending direction of the cross as the X-axis, and the other extending direction as the Y-axis, the conductive layer is further configured as follows: Electrodes are respectively connected to both ends of the conductive layer along the X-axis for passing the first current; Electrodes are respectively connected to both ends of the conductive layer along the Y axis for detecting the Hall voltage; The method comprises: A pulse current is introduced along the X-axis direction; A Hall voltage is detected between adjacent pulse periods of the pulse current along the Y-axis direction, and a random number sequence is obtained according to the Hall voltage.

13. A method for generating true random numbers using the true random number generator according to any one of claims 1 to 11, characterized in that: The multilayer film structure further comprises: a substrate, the conductive layer being located on the substrate; a second magnetic layer, located on the spin current compensation layer, and having an easy magnetization direction perpendicular to an interface between the spin current compensation layer and the second magnetic layer; a pinning layer, located on the second magnetic layer, for fixing the magnetic moment direction of the second magnetic layer; A capping layer is located above the pinning layer and is used to protect the layers below it; The conductive layer is in a strip shape, the first magnetic layer, the spin current cancellation layer, the second magnetic layer, the pinning layer, and the capping layer are thin films having the same cross-sectional shape, and the first magnetic layer, the spin current cancellation layer, the second magnetic layer, the pinning layer, and the capping layer are stacked in a central region of the strip; The geometric center of the strip is taken as the origin of the three-dimensional rectangular coordinate, the extending direction of the strip is taken as the X-axis, and the Z-axis is perpendicular to the X-axis and along the stacking direction of the multilayer film structure. Electrodes are respectively connected to both ends of the conductive layer along the X-axis for passing the first current; An electrode is connected to one end of the cap layer along the Z axis for passing a second current; The method comprises: A pulse current with a preset interval is introduced along the X-axis direction; The second current is passed along the Z axis at the preset interval to measure the magnetoresistance of the multilayer film structure, and a random number sequence is obtained according to the magnetoresistance.

14. The method of claim 12 or 13, wherein The Joule heat generated by the first current in one pulse period is greater than the energy required for the magnetic moment of the first magnetic layer to be switched.

15. The method of claim 13, wherein The Joule heat generated by the second current in the preset interval is smaller than the energy required for the magnetic moment of the first magnetic layer to be switched.

16. The method of claim 12 or 13, further comprising: By controlling the pulse period of the first current, the rate of generating true random numbers is controlled.

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