Magnetic tunnel junction, magnetic tunnel junction manufacturing method, and camshaft sensor

Abstract

The present application discloses a magnetic tunnel junction, a magnetic tunnel junction manufacturing method, and a camshaft sensor. The magnetic tunnel junction comprises: a free magnetic layer, a reference magnetic layer, an insulating barrier layer, and an intermediate layer; and the intermediate layer is provided on the side of the reference magnetic layer facing away from the insulating barrier layer, the intermediate layer comprises a stable layer, and the stable layer is provided close to the reference magnetic layer, wherein the reference magnetic layer is composed of N types of elements, the N types of elements comprise an unstable element, the stable layer is composed of M types of elements, and the M types of elements comprises an unstable element. The technical solution provided in the present application can prevent the unstable element of the reference magnetic layer from diffusing to the insulating barrier layer, thereby ensuring that performance of the insulating barrier layer is not affected by diffusion of the unstable element.

Description

Magnetic tunnel junction, method of manufacturing magnetic tunnel junction, and camshaft sensor Cross-reference to Related Applications

[0001] This application claims priority to Chinese Patent Application No. 202410834420.3, filed on June 26, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application belongs to the technical field of sensors, and particularly relates to a magnetic tunnel junction, a method of manufacturing a magnetic tunnel junction, and a camshaft sensor. BACKGROUND

[0003] A magnetic tunnel junction (MTJ) refers to a junction element mainly comprising:

[0004] A ferromagnetic layer / tunnel magnetoresistance / ferromagnetic layer, which is an important component for implementing various sensors, such as an important component for a camshaft sensor. The camshaft sensor is used to detect a camshaft position signal, so that a controller can perform engine control based on the signal provided by the camshaft sensor.

[0005] At present, the stability of the ferromagnetic layer with a fixed magnetic moment direction in the magnetic tunnel junction can be poor, thereby affecting the overall performance of the magnetic tunnel junction. SUMMARY

[0006] The technical solution of the present application provides a magnetic tunnel junction, a method of manufacturing a magnetic tunnel junction, and a camshaft sensor, thereby preventing, at least to some extent, the diffusion of non-stable elements of the reference magnetic layer to the insulating barrier layer, ensuring that the performance of the insulating barrier layer is not affected by the diffusion of non-stable elements, and thereby ensuring that the overall performance of the magnetic tunnel junction is relatively good.

[0007] Other characteristics and advantages of the present application will become apparent from the following detailed description, or will be learned by practice of the present application.

[0008] According to a first aspect of the technical solution of the present application, a magnetic tunnel junction is provided, comprising:

[0009] a free magnetic layer;

[0010] a reference magnetic layer;

[0011] an insulating barrier layer, disposed between the free magnetic layer and the reference magnetic layer;

[0012] and an intermediate layer disposed on a side of the reference magnetic layer away from the insulating barrier layer, the intermediate layer comprising a stabilizing layer disposed proximate to the reference magnetic layer, wherein a composition of the reference magnetic layer comprises N elements, the N elements comprising a non-stable element, and a composition of the stabilizing layer comprises M elements, the M elements comprising the non-stable element, N and M each being an integer greater than 1.

[0013] In some preferred embodiments of the present application, based on the foregoing, the composition of the free magnetic layer and the reference magnetic layer is Co x Fe y Re z wherein the Re element is the non-stable element, the Re element comprising at least one of aluminum (Al), boron (B), selenium (Si), and manganese (Mn), and x, y, and z represent the proportions of the Co element, the Fe element, and the Re element, respectively.

[0014] In some preferred embodiments of the present application, based on the foregoing, the thickness of the reference magnetic layer is greater than the thickness of the free magnetic layer.

[0015] In some preferred embodiments of the present application, based on the foregoing, the composition of the stabilizing layer comprises the Re element.

[0016] In some preferred embodiments of the present application, based on the foregoing, the method further comprises:

[0017] a pinning layer disposed on a side of the intermediate layer away from the reference magnetic layer, the pinning layer comprising at least one of cobalt-iron-boron (CoFeB), cobalt-iron (CoFe), nickel-iron (NiFe), iron-gallium-boron (FeGaB), cobalt (Co), iron (Fe), nickel-iron-cobalt (NiFeCo), and cobalt-niobium-zirconium (CoNbZr);

[0018] an anti-ferromagnetic layer disposed on a side of the pinning layer away from the intermediate layer, the anti-ferromagnetic layer comprising at least one of platinum-manganese alloy (PtMn), iridium-manganese alloy (IrMn), and iron-manganese alloy (FeMn).

[0019] In some preferred embodiments of the present application, based on the foregoing, the intermediate layer further comprises:

[0020] a coupling layer disposed between the stabilizing layer and the pinning layer, the coupling layer comprising at least one of ruthenium (Ru) and tantalum (Ta).

[0021] In some optimized technical solutions of the present application, based on the foregoing scheme, the thickness of the insulating barrier layer ranges from 0.8 to 1.2 nanometers, and the composition material of the insulating barrier layer includes at least one of magnesium borate (Mg3B2O6), aluminum trioxide (Al2O3), and magnesium oxide (MgO).

[0022] In some technical solutions of the present application, based on the foregoing scheme, the method further comprises:

[0023] The first isolation layer is arranged on the side of the free magnetic layer away from the insulating barrier layer, and the composition material of the first isolation layer includes at least one of tantalum (Ta) and ruthenium (Ru);

[0024] The second isolation layer is arranged on the side of the first isolation layer away from the free magnetic layer, and the composition material of the second isolation layer includes magnesium (Mg);

[0025] The conductive layer is arranged on the side of the second isolation layer away from the first isolation layer, and the composition material of the conductive layer includes at least one of platinum (Pt), gold (Au), tungsten (W), aluminum (Al), copper (Cu), silver (Ag), ruthenium (Ru), tantalum (Ta), and titanium (Ti);

[0026] The buffer layer is arranged on the side of the intermediate layer away from the reference magnetic layer, and the composition material of the buffer layer includes at least one of platinum (Pt), gold (Au), tungsten (W), aluminum (Al), copper (Cu), and titanium (Ti).

[0027] According to a second aspect of the technical solutions of the present application, a method for preparing a magnetic tunnel junction is provided, which comprises:

[0028] providing a substrate layer;

[0029] forming an intermediate layer, a reference magnetic layer, an insulating barrier layer, and a free magnetic layer on the substrate layer in sequence by using a magnetron sputtering process;

[0030] The intermediate layer includes a stabilizing layer, the stabilizing layer is arranged close to the reference magnetic layer, the composition material of the reference magnetic layer includes N kinds of elements, one of the N kinds of elements is a non-stable element, the composition material of the stabilizing layer includes M kinds of elements, the M kinds of elements include the non-stable element, and N and M are both integers greater than 1.

[0031] In some optimized technical solutions of the present application, based on the foregoing scheme, after the intermediate layer, the reference magnetic layer, the insulating barrier layer, and the free magnetic layer are formed on the substrate layer in sequence by using the magnetron sputtering process, the method further comprises:

[0032] anneal the intermediate layer, the reference magnetic layer, the insulating barrier layer and the free magnetic layer in a first temperature range for a first time length;

[0033] raise the first temperature range to a second temperature range, anneal the intermediate layer, the reference magnetic layer, the insulating barrier layer and the free magnetic layer in the second temperature range for a second time length, and apply a preset magnetic field intensity to the reference magnetic layer.

[0034] According to a third aspect of the technical scheme of the application, a camshaft sensor is provided, comprising the magnetic tunnel junction according to any one of the first aspect.

[0035] In some optimized technical schemes of the application, based on the foregoing scheme, the rising edge time of the camshaft sensor ranges from 0.4 to 2.6 μs, and the falling edge time of the camshaft sensor ranges from 0.2 to 1.2 μs.

[0036] In some optimized technical schemes of the application, based on the foregoing scheme, a sensor shell is further included, the sensor shell is internally provided with a sensor chip comprising the magnetic tunnel junction, and the sensor chip is arranged on the bottom of the sensor shell.

[0037] In some optimized technical schemes of the application, based on the foregoing scheme, a magnet piece is further included, the magnet piece is arranged on the side of the sensor chip away from the bottom of the sensor shell, and the magnetic field intensity of the magnet piece has a corresponding relationship with the sensitivity parameter of the sensor chip.

[0038] In some optimized technical schemes of the application, based on the foregoing scheme, the sensitivity parameter comprises a signal edge time and / or a magnetoresistance change rate, the signal edge time is positively correlated with the magnetic field intensity, and the magnetoresistance change rate is negatively correlated with the magnetic field intensity.

[0039] In some optimized technical schemes of the application, based on the foregoing scheme, the magnet piece adopts a samarium-cobalt magnet, and the magnetic field intensity of the magnet piece ranges from 200 to 355 mT.

[0040] One or more technical schemes provided by the technical scheme of the application at least achieve the following technical effects or advantages:

[0041] The application sets an intermediate layer on the side of the reference magnetic layer of the magnetic tunnel junction away from the insulating barrier layer, and sets a stable layer of the intermediate layer close to the reference magnetic layer. Since the composition material of the stable layer has the same non-stable element as the composition material of the reference magnetic layer, when the non-stable element of the reference magnetic layer diffuses due to the influence of temperature and the like, the stable layer can absorb and inhibit the non-stable element in the reference magnetic layer, thereby preventing the non-stable element from diffusing upward to the insulating barrier layer, thereby affecting the performance of the insulating barrier layer, and further affecting the magnetic resistance change rate, and further affecting the overall performance of the magnetic tunnel junction.

[0042] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the application. BRIEF DESCRIPTION OF DRAWINGS

[0043] The drawings incorporated into the specification and constituting a part of the specification show the technical solutions consistent with the application, and are used together with the specification to explain the principles of the application. Obviously, the drawings in the following description are only some technical solutions of the application, and other drawings can be obtained by those skilled in the art without creative labor. In the drawings:

[0044] Fig. 1 shows a structure diagram of a magnetic tunnel junction of the technical solutions of the application;

[0045] Fig. 2 shows another structure diagram of a magnetic tunnel junction of the technical solutions of the application;

[0046] Fig. 3 shows a flowchart of a magnetic tunnel junction preparation method of the technical solutions of the application;

[0047] Fig. 4 shows a perspective structure diagram of a camshaft sensor of the technical solutions of the application;

[0048] Fig. 5 shows an exploded view of a camshaft sensor of the technical solutions of the application;

[0049] Fig. 6 shows a partial enlarged view of A in Fig. 5;

[0050] Fig. 7 shows a circuit schematic diagram inside a sensor chip of the technical solutions of the application.

[0051] Explanation of reference signs;

[0052] 1-free magnetic layer; 2-reference magnetic layer; 3-insulating barrier layer; 4-intermediate layer; 41-stable layer; 42-coupling layer; 5-pinning layer; 6-anti-ferromagnetic layer; 7-first isolation layer; 8-second isolation layer; 9-conductive layer; 10-buffer layer; 11-substrate layer; 12-sensor housing; 13-sensor chip; 14-receiving cavity; 15-magnet piece. DETAILED DESCRIPTION

[0053] The technical solutions in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described technical solutions are only some of the technical solutions in the present application, but not all the technical solutions in the present application. Based on the technical solutions in the present application, all other technical solutions obtained by those skilled in the art without creative effort belong to the scope of protection of the present application.

[0054] In addition, the described features, structures or characteristics can be combined in any suitable way in one or more technical solutions. In the following description, many specific details are provided to give a full understanding of the technical solutions of the present application. However, those skilled in the art will realize that the technical solutions of the present application can be practiced without one or more of the specific details, or can employ other methods, components, devices, steps, etc. In other cases, well-known methods, devices, implementations or operations are not shown or described in detail to avoid obscuring the aspects of the present application.

[0055] The block diagrams shown in the drawings are only functional entities, and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0056] The flowcharts shown in the drawings are only exemplary illustrations, and do not necessarily include all contents and operations / steps, nor do they necessarily have to be executed in the described order. For example, some operations / steps can be further decomposed, and some operations / steps can be combined or partially combined, so the actual execution order can be changed according to the actual situation.

[0057] It should also be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the objects thus used can be interchanged under appropriate circumstances, so that the technical solutions of the present application described herein can be implemented in an order other than that illustrated or described.

[0058] In order to facilitate understanding of the technical solutions of the present application, the concept of a magnetic tunnel junction involved in the technical solutions of the present application will first be described.

[0059] Magnetic Tunnel Junction (MTJ): is an important component to realize various sensors, for example, is an important component of camshaft sensor. Mainly includes free magnetic layer / insulating barrier layer / ferromagnetic layer, wherein the free magnetic layer and the reference magnetic layer are usually composed of ferromagnetic material, the reference magnetic layer has a fixed magnetization direction, the magnetization direction of the free magnetic layer can be reversed, and the magnetization direction of the free magnetic layer is different from or the same as the magnetization direction of the reference magnetic layer. The resistance of the corresponding insulating barrier layer is different. Specifically, when the magnetization direction of the free magnetic layer is the same (parallel) as the magnetization direction of the reference magnetic layer, the insulating barrier layer presents a low resistance state, and when the magnetization direction of the free magnetic layer is opposite (antiparallel) to the magnetization direction of the reference magnetic layer, the insulating barrier layer presents a high resistance state.

[0060] The magnetic tunnel junction of the technical scheme of the present application is described below.

[0061] Referring to FIG. 1 and FIG. 2, FIG. 1 shows a structure diagram of the magnetic tunnel junction of the technical scheme of the present application; FIG. 2 shows another structure diagram of the magnetic tunnel junction of the technical scheme of the present application.

[0062] According to a first aspect of the present application, a magnetic tunnel junction is provided, comprising: a free magnetic layer 1; a reference magnetic layer 2; an insulating barrier layer 3 disposed between the free magnetic layer 1 and the reference magnetic layer 2; and an intermediate layer 4 disposed on the side of the reference magnetic layer 2 away from the insulating barrier layer 3, the intermediate layer 4 comprising a stabilizing layer 41 disposed close to the reference magnetic layer 2, wherein the composition material of the reference magnetic layer 2 comprises N kinds of elements, one of which is a non-stable element, and the composition material of the stabilizing layer 41 comprises M kinds of elements, one of which is the non-stable element, and N and M are both integers greater than 1.

[0063] It can be understood that detection sensitivity is the performance factor that the magnetic tunnel junction prioritizes, therefore, the free magnetic layer 1 and the reference magnetic layer 2 of the magnetic tunnel junction will usually adopt ferromagnetic materials that can improve the magnetoresistance change rate (i.e. improve the detection sensitivity), but these ferromagnetic materials may include non-stable elements, such as aluminum elements, etc. Non-stable elements may diffuse to the insulating barrier layer 3 under the influence of environmental temperature, etc., thereby affecting the performance of the insulating barrier layer 3, and further affecting the magnetoresistance change rate, ultimately leading to a decrease in the detection sensitivity of the magnetic tunnel junction.

[0064] Based on the above, the application sets the intermediate layer 4 on the side of the reference magnetic layer 2 of the magnetic tunnel junction away from the insulating barrier layer 3, and sets the stable layer 41 of the intermediate layer 4 close to the reference magnetic layer 2. Since the composition material of the stable layer 41 has the same non-stable element as the composition material of the reference magnetic layer 2, when the non-stable element of the reference magnetic layer 2 diffuses due to the influence of temperature and the like, the stable layer 41 can absorb and inhibit the non-stable element in the reference magnetic layer 2, thereby preventing the non-stable element from diffusing upward to the insulating barrier layer 3, thereby affecting the performance of the insulating barrier layer 3, and further affecting the magnetic resistance change rate, and further affecting the overall performance of the magnetic tunnel junction.

[0065] In some embodiments, the composition material of the free magnetic layer 1 and the reference magnetic layer 2 is CoxFeyRez, wherein Re element is the non-stable element, the Re element includes at least one of aluminum (Al), boron (B), selenium (Si) and manganese (Mn), and x, y and z respectively represent the proportions of Co element, Fe element and Re element.

[0066] In some embodiments, in the composition material CoxFeyRez of the free magnetic layer 1, the proportions of Co element, Fe element and Re element are x1:y1:z1, wherein x1+y1+z1=100, the value range of x1 is 40-80, the value range of y1 is 10-40, and the value range of z1 is 10-30.

[0067] In some embodiments, in the composition material CoxFeyRez of the reference magnetic layer 2, the proportions of Co element, Fe element and Re element are x2:y2:z2, wherein x2+y2+z2=100, the value range of x2 is 20-60, the value range of y2 is 20-60, and the value range of z2 is 10-30.

[0068] In some embodiments, the thickness of the reference magnetic layer 2 is greater than the thickness of the free magnetic layer 1.

[0069] It can be understood that when the thickness of the reference magnetic layer 2 is greater than the thickness of the free magnetic layer 1, and the thickness of the reference magnetic layer 2 and the thickness of the free magnetic layer 1 have a proper ratio relationship, the reference magnetic layer 2 itself can realize the fixation of the magnetization direction, and is not affected by the free magnetic layer 1. For example, when the ratio between the thickness of the reference magnetic layer 2 and the thickness of the free magnetic layer 1 is in the range of 1.2-2.5, the reference magnetic layer 2 itself can realize the fixation of the magnetization direction, and is not affected by the free magnetic layer 1.

[0070] In some embodiments, the composition of the stabilizing layer 41 includes at least one of the Re element, i.e., aluminum (Al), boron (B), selenium (Si), and manganese (Mn), which is adapted to the Re element in the reference magnetic layer 2, so as to absorb and inhibit the Re element in the reference magnetic layer 2 when the Re element in the reference magnetic layer 2 diffuses, and prevent the Re element in the reference magnetic layer 2 from diffusing to the insulating barrier layer 3 and affecting the performance of the insulating barrier layer 3.

[0071] In some embodiments, the content of the Re element in the stabilizing layer 41 in the M elements is 5% to 20%.

[0072] It can be understood that the specific content of the Re element in the stabilizing layer 41 in the M elements can be determined according to the content of the Re element in the reference magnetic layer 2 in the N elements. The absorption capacity of the Re element in the stabilizing layer 41 for the Re element in the reference magnetic layer 2 should have an absorption threshold. When the absorption threshold is reached, the Re element in the stabilizing layer 41 and the Re element in the reference magnetic layer 2 can reach a dynamic balance, so as to prevent the Re element in the reference magnetic layer 2 from diffusing upward to the insulating barrier layer 3 on the one hand, and ensure that the diffusion amplitude of the Re element in the reference magnetic layer 2 is small and does not affect the performance of the reference magnetic layer 2 itself on the other hand.

[0073] In some embodiments, when the composition of the reference magnetic layer 2 is CoxFeyAlz, the composition of the stabilizing layer 41 is an aluminum-magnesium alloy material for absorbing and inhibiting the diffusion of Al in CoxFeyAlz and improving the temperature stability of the magnetoresistance change rate. For example, the thickness of the aluminum-magnesium alloy material is not higher than 0.5 nm.

[0074] It can be understood that when the thickness of the reference magnetic layer 2 is greater than the thickness of the free magnetic layer 1, and the thickness of the reference magnetic layer 2 has an appropriate ratio relationship with the thickness of the free magnetic layer 1, the reference magnetic layer 2 itself can realize the fixation of the magnetization direction without being affected by the free magnetic layer 1. For example, when the ratio between the thickness of the reference magnetic layer 2 and the thickness of the free magnetic layer 1 is in the range of 1.2 to 2.5, the reference magnetic layer 2 itself can realize the fixation of the magnetization direction without being affected by the free magnetic layer 1. At this time, it is not necessary to set the film layer structure of the pinning layer 5 and the anti-ferromagnetic layer 6 to fix the magnetization direction of the reference magnetic layer 2. At this time, the film layer structure of the magnetic tunnel junction is shown in FIG. 1.

[0075] When the thickness of the reference magnetic layer 2 is greater than the thickness of the free magnetic layer 1, but the difference between the thickness of the reference magnetic layer 2 and the thickness of the free magnetic layer 1 is small, for example, the thickness of the free magnetic layer 1 is in the range of 0.8-6 nm, and the thickness of the reference magnetic layer 2 is in the range of 2-8 nm, the reference magnetic layer 2 itself cannot realize the fixation of the magnetization direction, and is affected by the free magnetic layer 1, so it is still necessary to set the film layer structure of the pinning layer 5 and the anti-ferromagnetic layer 6 to fix the magnetization direction of the reference magnetic layer 2. At this time, the film layer structure of the magnetic tunnel junction is shown in FIG. 2.

[0076] In some embodiments, the method further comprises:

[0077] The pinning layer 5 is arranged on the side of the intermediate layer 4 away from the reference magnetic layer 2, and the composition material of the pinning layer 5 includes at least one of cobalt-iron-boron (CoFeB), cobalt-iron (CoFe), nickel-iron (NiFe), iron-gallium-boron (FeGaB), Co (cobalt), Fe (iron), nickel-iron-cobalt (NiFeCo), and cobalt-niobium-zirconium (CoNbZr), for example, Cox3Fey3 is used, wherein x3+y3=100, and the value range of x3 is 40-80.

[0078] The anti-ferromagnetic layer 6 is arranged on the side of the pinning layer 5 away from the intermediate layer 4, and the composition material of the anti-ferromagnetic layer 6 includes at least one of platinum-manganese alloy (PtMn), iridium-manganese alloy (IrMn), and iron-manganese alloy (FeMn).

[0079] In some embodiments, the thickness of the pinning layer 5 is in the range of 2-5 nm.

[0080] In some embodiments, the thickness of the anti-ferromagnetic layer 6 is in the range of 5-20 nm.

[0081] In some embodiments, the intermediate layer 4 further comprises:

[0082] The coupling layer 42 is arranged between the stabilizing layer 41 and the pinning layer 5, and the composition material of the coupling layer 42 includes at least one of ruthenium (Ru) and tantalum (Ta).

[0083] Specifically, the coupling layer 42 isolates the reference magnetic layer 2 and the pinning layer 5, while enabling the anti-ferromagnetic exchange coupling between the reference magnetic layer 2 and the pinning layer 5. For example, the coupling layer 42 is a ruthenium layer. Since ruthenium has anti-ferromagnetic properties, the magnetic field generated by the current passes through the ruthenium layer to magnetize the pinning layer 5, and then magnetize the reference magnetic layer 2 and the pinning layer 5 in opposite directions, so that they attract each other and are locked, thereby realizing the stability of the magnetic field of the reference magnetic layer 2.

[0084] In some embodiments, the thickness of the insulating barrier layer 3 is in the range of 0.8 to 1.2 nm, and the insulating barrier layer 3 is made of at least one of magnesium borate (Mg3B2O6), aluminum trioxide (Al2O3) and magnesium oxide (MgO).

[0085] In some embodiments, the device further comprises:

[0086] The first isolation layer 7 is disposed on the side of the free magnetic layer 1 away from the insulating barrier layer 3, and the first isolation layer 7 is made of at least one of tantalum (Ta) and ruthenium (Ru).

[0087] The second isolation layer 8 is disposed on the side of the first isolation layer 7 away from the free magnetic layer 1, and the second isolation layer 8 is made of magnesium (Mg).

[0088] The conductive layer 9 is disposed on the side of the second isolation layer 8 away from the first isolation layer 7, and the conductive layer 9 is made of at least one of platinum (Pt), gold (Au), tungsten (W), aluminum (Al), copper (Cu), silver (Ag), ruthenium (Ru), tantalum (Ta) and titanium (Ti).

[0089] The buffer layer 10 is disposed on the side of the intermediate layer 4 away from the reference magnetic layer 2, and the buffer layer 10 is made of at least one of platinum (Pt), gold (Au), tungsten (W), aluminum (Al), copper (Cu) and titanium (Ti).

[0090] It should be noted that the first isolation layer 7 has good oxidation resistance and good density, which can prevent the nano-multilayer film structure from being contaminated during the deposition of the thin film, thereby avoiding the influence on the performance of the device. The thickness of the first isolation layer 7 is in the range of 2 to 10 nm.

[0091] It should be noted that the second isolation layer 8 is used to stabilize the structure of the free magnetic layer 1 during the annealing process of the magnetic tunnel junction preparation process, and to reduce the temperature fluctuation of the magnetic resistance change rate of the magnetic tunnel junction at different temperatures. The thickness of the second isolation layer 8 is in the range of 0.5 to 1 nm.

[0092] It should be noted that the conductive layer 9 can be the above-mentioned metal material, or a topological insulator, or other conductor materials.

[0093] It should be noted that the buffer layer 10 is a transition from the insulating substrate to the functional magnetic tunnel structure, and also serves as the bottom electrode of the functional magnetic tunnel structure. The thickness of the buffer layer 10 is in the range of 5-15 nm. When the thickness of the reference magnetic layer 2 is greater than the thickness of the free magnetic layer 1, and the thickness of the reference magnetic layer 2 has an appropriate ratio relationship with the thickness of the free magnetic layer 1, the reference magnetic layer 2 itself can realize the fixation of the magnetization direction, and the buffer layer 10 is arranged on the side of the intermediate layer 4 away from the reference magnetic layer 2. When the thickness of the reference magnetic layer 2 is greater than the thickness of the free magnetic layer 1, but the difference between the thickness of the reference magnetic layer 2 and the thickness of the free magnetic layer 1 is small, the magnetization direction of the reference magnetic layer 2 needs to be fixed by setting the pinning layer 5 and the antiferromagnetic layer 6 and other film layer structures, and the buffer layer 10 is arranged on the side of the antiferromagnetic layer 6 away from the pinning layer 5.

[0094] It can be understood that the magnetic tunnel junction also includes a substrate layer 11, which can be a semiconductor substrate, a bare chip (a chip that has not been packaged), or other substrate structures, which are not limited by the technical solutions of the present application. The composition material of the substrate layer 11 can be at least one of SiO2, MgO, Al2O3, Si, SiN, SiC, GaAs (gallium arsenide), InP (indium phosphide), SrTiO3 (strontium titanate), LaAlO3 (lanthanum aluminate crystal), and SrRuO3 (strontium ruthenate).

[0095] Referring to FIG. 3, a flowchart of a magnetic tunnel junction preparation method according to the technical solutions of the present application is shown.

[0096] According to the second aspect of the technical solutions of the present application, a magnetic tunnel junction preparation method is provided, which includes:

[0097] Step S1. Providing a substrate layer;

[0098] Step S2. Forming an intermediate layer, a reference magnetic layer, an insulating barrier layer, and a free magnetic layer on the substrate layer in sequence by using a magnetron sputtering process.

[0099] The intermediate layer includes a stabilizing layer, the stabilizing layer is arranged close to the reference magnetic layer, the composition material of the reference magnetic layer includes N kinds of elements, one of the N kinds of elements is a non-stable element, the composition material of the stabilizing layer includes M kinds of elements, the M kinds of elements include the non-stable element, and N and M are both integers greater than 1.

[0100] Based on the above disclosure, the magnetic tunnel junction prepared by the magnetron sputtering process has the stable layer of the intermediate layer close to the reference magnetic layer. Since the stable layer has the same non-stable element as the reference magnetic layer, when the non-stable element of the reference magnetic layer diffuses due to the influence of temperature, etc., the stable layer can absorb and inhibit the non-stable element in the reference magnetic layer, thereby preventing the non-stable element from diffusing upward to the insulating barrier layer, thereby affecting the performance of the insulating barrier layer, and further affecting the magnetic resistance change rate, and further affecting the overall performance of the magnetic tunnel junction.

[0101] It should be noted that when the substrate layer is provided, the substrate layer needs to be treated, including: the surface roughness of the substrate is ≤5Å, first, ultrasonic cleaning with anhydrous ethanol for a period of time to remove surface oil, for example, cleaning for 30 minutes; then, ultrasonic cleaning with acetone for a period of time, for example, 30 minutes, and ultrasonic cleaning with isopropyl alcohol for a period of time, for example, 30 minutes; finally, ultrasonic cleaning with deionized water twice, each for 15 minutes.

[0102] It can be understood that since when the thickness of the reference magnetic layer is greater than the thickness of the free magnetic layer, and the thickness of the reference magnetic layer has a proper ratio relationship with the thickness of the free magnetic layer, the reference magnetic layer itself can realize the fixation of the magnetization direction, then the magnetic tunnel junction to be prepared includes the buffer layer, the intermediate layer, the reference magnetic layer, the insulating barrier layer, the free magnetic layer, the first isolation layer, the second isolation layer and the conductive layer formed in sequence on the substrate layer. In addition, since when the thickness of the reference magnetic layer is greater than the thickness of the free magnetic layer, but the difference between the thickness of the reference magnetic layer and the thickness of the free magnetic layer is small, the magnetization direction of the reference magnetic layer needs to be fixed by setting the film layer structure of the pinning layer and the anti-ferromagnetic layer, then the magnetic tunnel junction to be prepared includes the buffer layer, the anti-ferromagnetic layer, the pinning layer, the intermediate layer, the reference magnetic layer, the insulating barrier layer, the free magnetic layer, the first isolation layer, the second isolation layer and the conductive layer formed in sequence on the substrate layer. The preparation process of each film layer will be described below.

[0103] The buffer layer has a deposition chamber gas pressure of 0.1-0.5 Pa, a direct current power of 5-20 W, and a deposition rate controlled at 0.05-0.15 nm / s.

[0104] The anti-ferromagnetic layer has a deposition chamber gas pressure of 0.1-0.5 Pa, a direct current power of 5-20 W, and a deposition rate controlled at 0.05-0.15 nm / s.

[0105] The pinning layer has a deposition chamber gas pressure of 0.5-1 Pa, a direct current power of 5-20 W, and a deposition rate controlled at 0.05-0.15 nm / s.

[0106] The middle layer is deposited at a pressure of 0.1-0.5 Pa in a deposition chamber, a power of 5-20 W of a direct current power supply, and a deposition rate of 0.05-0.1 nm / s.

[0107] The reference magnetic layer is deposited at a pressure of 0.1-0.5 Pa in a deposition chamber, a power of 15-25 W of a radio frequency power supply, and a deposition rate of 0.05-0.1 nm / s.

[0108] The insulating barrier layer is deposited at a pressure of 0.1-0.5 Pa in a deposition chamber, a power of 60-100 W of a radio frequency power supply, and a deposition rate of 0.05-0.1 nm / s, and the deposition process is performed in an O2 flow including 1-5 sccm.

[0109] The free magnetic layer is deposited at a pressure of 0.1-0.5 Pa in a deposition chamber, a power of 15-25 W of a radio frequency power supply, and a deposition rate of 0.05-0.1 nm / s.

[0110] The first and second isolation layers are deposited at a pressure of 0.1-0.5 Pa in a deposition chamber, a power of 5-20 W of a direct current power supply, and a deposition rate of 0.05-0.1 nm / s.

[0111] The conductive layer is deposited at a pressure of 0.1-0.5 Pa in a deposition chamber, a power of 5-20 W of a direct current power supply, and a deposition rate of 0.1-0.15 nm / s.

[0112] It should be noted that when each film layer is prepared by using a magnetron sputtering process, if the composition material of the film layer includes multiple elements, the target material used to prepare the film layer can be a target material including only a single element, or a mixed target material including each element of the composition material.

[0113] For example, when the reference magnetic layer is prepared, the composition material of the reference magnetic layer is Co x2 Fe y2 Re z2 Therefore, the target material used can be a CO element target, an Fe element target, and an Re element target, and then the CO element target, the Fe element target, and the Re element target are impacted in a ratio of x2:y2:z2 by using a magnetron sputtering process to deposit a reference magnetic layer of Co x2 Fe y2 Re z2 Alternatively, the target material used can be a mixed target of CO elements, Fe elements, and Re elements mixed into one body in advance in a ratio of x2:y2:z2, and then the mixed target is impacted by using a magnetron sputtering process to deposit a reference magnetic layer of Co x2 Fe y2 Re z2a reference magnetic layer.

[0114] In some embodiments, after the intermediate layer, the reference magnetic layer, the insulating barrier layer and the free magnetic layer are sequentially formed on the base layer by the magnetron sputtering process, the method further comprises:

[0115] Step S3. Annealing heat pretreatment is performed on the intermediate layer, the reference magnetic layer, the insulating barrier layer and the free magnetic layer in a first temperature range for a first time length.

[0116] It can be understood that after the deposition of each film layer on the base layer, the performance of different film layers can be quite different. By performing annealing heat pretreatment on each film layer, the lattice adaptability between layers can be improved.

[0117] In some embodiments, the first temperature range is 200-250℃, and the first time length is 0.5-1 hour.

[0118] Step S4. The first temperature range is raised to a second temperature range, annealing heat treatment is performed on the intermediate layer, the reference magnetic layer, the insulating barrier layer and the free magnetic layer in the second temperature range for a second time length, and a preset magnetic field strength is applied to the reference magnetic layer.

[0119] In some embodiments, the second temperature range is 350-550℃, the heating rate from the first temperature range to the second temperature range is 10-50℃ / min, the second time length is 1-2 hours, and the preset magnetic field strength is 400-500 Oe.

[0120] In order to facilitate the understanding of the technical solutions of the present application, first, the concept of camshaft sensor involved in the technical solutions of the present application is described.

[0121] The camshaft sensor, also known as camshaft position sensor, camshaft angle sensor, camshaft phase sensor, camshaft cylinder position sensor, camshaft synchronous signal sensor or cylinder identification (cylinder position) sensor, etc., functions to detect the position and angle of the camshaft, so as to determine the top dead center position of the first cylinder piston. At the time of starting, the controller can identify the position and stroke of each cylinder piston according to the signal provided by the camshaft sensor, so as to control the fuel injection and ignition sequence.

[0122] At present, in the related art, the camshaft sensor mainly adopts a differential Hall sensor. The signal output by the Hall effect of the Hall sensor is affected by temperature, and thus there is a certain temperature drift phenomenon. In addition, the Hall sensor needs a magnetic ring structure to amplify the magnetic field, so as to improve the sensitivity of the Hall signal output. However, this way will cause the Hall effect to have a large power consumption. In addition, the output signal of the Hall sensor is easily disturbed by the external magnetic field, thereby affecting the measurement accuracy. Furthermore, due to the poor sensitivity of the Hall sensor, the air gap between the sensor head detection chip and the camshaft signal disc (i.e. the distance between the sensor chip and the signal disc) needs to be closer, because the sensor chip realizes signal detection by sensing the size of the magnetic field around the signal disc. The larger the air gap between the sensor head detection chip and the camshaft signal disc, the weaker the influence of the rotation of the signal disc on the magnetic field around the sensor. Furthermore, the Hall sensor has a higher requirement for the magnetic field strength, and the sensor chip needs to be closely assembled with the magnet. When the magnet is in a high-temperature environment for a long time, the magnetic material will decay, the magnetic field strength of the magnet will weaken, and the output signal of the sensor will weaken, and even the signal will be lost.

[0123] Referring to FIGS. 4 to 6, FIG. 4 shows a perspective view of the camshaft sensor of the technical scheme of the present application;

[0124] FIG. 5 shows an exploded view of the camshaft sensor of the technical scheme of the present application; and FIG. 6 shows a partial enlarged view of A in FIG. 5.

[0125] As known from the above, the existing camshaft sensor at least has the problem of poor detection sensitivity. Based on this, the third aspect of the technical scheme of the present application provides a camshaft sensor, which comprises the magnetic tunnel junction of any one of the first aspect. The magnetic tunnel junction can be one or more.

[0126] In some technical schemes, the camshaft sensor comprises at least one magnetic induction unit, each magnetic induction unit adopts a push-pull Wheatstone bridge structure, that is, the push-pull Wheatstone bridge structure comprises four resistors, each resistor is a magnetic tunnel junction. For the convenience of understanding, the magnetic tunnel junction is also called a magnetic resistor.

[0127] It can be understood that when the Wheatstone bridge structure composed of multiple magnetic tunnel junctions is used for camshaft signal disc signal detection, based on the characteristics of the Wheatstone bridge structure itself, the temperature drift of the camshaft sensor can be effectively compensated, and because the output signal is a differential signal, it has good anti-interference performance.

[0128] It should be noted that, during the rotation of the camshaft signal disc, the camshaft signal disc cuts the magnetic field around the magnetic resistance camshaft sensor, thereby changing the resistance of the insulating barrier layer in each magnetic tunnel junction inside the sensor, and then outputting the corresponding voltage signal. Since the voltage signal output by the camshaft sensor has a corresponding logical relationship with the position of the signal disc (tooth top and tooth valley), for example, when the sensor detects the tooth top of the signal disc, a low-level signal is output, and when the sensor detects the tooth valley of the signal disc, a high-level signal is output, the position detection of the signal disc can be realized.

[0129] In some embodiments, the rising edge time of the camshaft sensor is 0.4-2.6 μs, and the falling edge time of the camshaft sensor is 0.2-1.2 μs.

[0130] It should be noted that, since the camshaft sensor adopts the magnetic tunnel junction of any one of the first aspect, the film layer structure adopted by the magnetic tunnel junction has good detection sensitivity, thereby making the rising edge time of the camshaft sensor reach 0.4-2.6 μs, and the falling edge time of the camshaft sensor reach 0.2-1.2 μs, so the detection sensitivity of the camshaft sensor to the position change of the signal disc is greatly improved.

[0131] In some embodiments, a sensor housing 12 is provided, the sensor housing 12 is provided with a sensor chip 13 including the magnetic tunnel junction, and the sensor chip 13 is attached to the bottom of the sensor housing 12.

[0132] For example, the bottom of the sensor housing 12 is provided with a receiving cavity 14, and the sensor chip 13 is embedded in the receiving cavity 14.

[0133] It can be understood that the receiving cavity 14 is integrally formed with the sensor housing 12, and the sensor chip 13 is embedded in the receiving cavity 14 to be fixed, so that the sensor chip 13 is as close to the edge of the housing as possible, and the magnetic induction unit in the sensor chip 13 is as close to the signal disc as possible, thereby reducing the air gap between the sensor chip 13 and the signal disc, and the sensor chip 13 is more sensitive to the induction of the signal disc cutting magnetic field, so that the output signal measured is more stable and reliable.

[0134] In some embodiments, a magnet piece 15 is further provided, the magnet piece 15 is arranged on the side of the sensor chip 13 away from the bottom of the sensor housing 12, and the magnetic field strength of the magnet piece 15 has a corresponding relationship with the sensitivity parameter of the sensor chip 13.

[0135] It can be understood that the magnet piece 15 is arranged opposite to the sensor chip 13, so that the sensor chip 13 and the magnet piece 15 are on the same central axis, that is, they are in a symmetrical magnetic field, thereby improving the inductive capacity of the signal disc cutting magnetic field change. It should be noted that the sensor chip 13 and the magnet piece 15 of the technical scheme of the present application do not need to be closely assembled, thereby delaying the magnetic material attenuation of the magnet piece 15 to a certain extent, and improving the service life of the magnet piece 15.

[0136] In some technical solutions, the sensitivity parameter includes a signal time and / or a magnetic resistance change rate, the signal time is positively correlated with the magnetic field strength, and the magnetic resistance change rate is negatively correlated with the magnetic field strength.

[0137] It can be understood that in the case of determining the signal time and / or the magnetic resistance change rate of the sensor chip 13, the magnetic field strength of the ferromagnetic piece is too high or too low, which is not conducive to ensuring the detection accuracy of the sensor chip 13. Therefore, by establishing the corresponding relationship between the signal time and / or the magnetic resistance change rate and the magnetic field strength of the magnet piece 15, the magnet piece 15 with the corresponding magnetic field strength can be configured according to the sensitivity parameter of the sensor chip 13, thereby ensuring the detection accuracy of the sensor chip 13.

[0138] In some technical solutions, the magnet piece 15 adopts a samarium-cobalt magnet, and the magnetic field strength of the ferromagnetic piece ranges from 200 to 355 mT.

[0139] It should be noted that the samarium-cobalt magnet has a high demagnetization temperature, thereby preventing the change of the magnetic field strength of the sensor in a high-temperature use environment, further delaying the magnetic material attenuation of the magnet piece 15, and improving the service life of the magnet piece 15.

[0140] In some technical solutions, the sensor housing 12 is provided with a circuit board, and the circuit board adopts a flexible circuit board, for example, an FPC flexible circuit board with a polyimide film as a substrate, thereby improving the anti-vibration capacity of the module.

[0141] It should be noted that the flexible circuit board is provided with the sensor chip 13, the pins of the sensor chip 13 are welded on the flexible circuit board, the other end of the flexible circuit board is welded on the pin metal terminal, and the metal terminal further extends out of the housing to realize signal connection. It can be understood that the sensor chip 13 is provided with three pin metal terminal output ports, which correspond to the power supply end VDD, the output end OUT and the ground end GND of the cam phase sensor, respectively.

[0142] It can be understood that the pin metal terminal can be injection molded with the sensor chip 13 as an insert, and matched with the existing connector. The terminal material is tin-plated brass, which can increase the solderability of the terminal, prevent the plug from oxidizing in a humid environment for a long time, and has good corrosion resistance.

[0143] It can be understood that the sensor chip 13 includes a peripheral signal processing circuit in addition to each magnetic induction unit. The signal processing circuit is used to process (for example, amplify or filter) the voltage change detected by the magnetic induction unit, and then output to the flexible circuit board, and then output to the controller through the flexible circuit board.

[0144] Referring to FIG. 7, a circuit schematic diagram inside the sensor chip of the technical scheme is shown.

[0145] For example: in FIG. 7, U1 represents a sensor chip, and resistors R1, and chip capacitors C1 and C2 constitute a signal processing circuit of the sensor chip.

[0146] In some technical schemes, the model of the sensor chip is SD208, the output pin includes a power supply end VDD, an output end OUT, and a ground end GND, and the on-chip voltage regulator contained in the chip can withstand the change and fluctuation of the external power supply within 4.5~24V. However, when applied in an environment with large stray noise, a basic RC low-pass filter needs to be added to the power supply line. The RC low-pass filter includes resistor R1 and capacitor C1.

[0147] It should be noted that the resistor needs to be able to withstand current and meet power requirements to ensure the stability and reliability of chip power supply. Based on this, the resistor R1 of the technical scheme adopts a thick film resistor 100 with an accuracy of ±1% and a power of 250mW. In addition, the capacitor C1 absorbs the noise of the power supply, and the capacitor C1 has a capacity of 100nF and an accuracy of ±10%. In addition, the capacitor C2 filters out the ripple of the output end OUT, and the capacitor C2 adopts a 1nF capacitor.

[0148] In some technical schemes, the preparation method of the camshaft sensor can include:

[0149] Injection molding of the sensor housing;

[0150] Assembling the flexible circuit board, the sensor chip and the ferromagnetic piece on the sensor housing;

[0151] Coating epoxy glue on the sensor chip and the flexible circuit board;

[0152] Filling epoxy glue in the housing;

[0153] Butt joint assembly of the sensor chip, the flexible circuit board and the sensor housing;

[0154] Baking the integrated structure assembled at a preset temperature, for example, 120 degrees;

[0155] Setting a sealing ring on the integrated structure.

[0156] It should be noted that the inside of the sensor shell is filled with epoxy resin to achieve dustproof and waterproof sealing, and the combination of the core and the shell (filling requirements: fill the epoxy resin into the sensor shell, vertically assemble the core into the shell from top to bottom, and bake at 120 DEG C for 1H after assembly to make the epoxy resin fully cured, during which the core and the shell cannot be loose, and the epoxy resin cannot overflow during the assembly process of the core and the shell. ) Epoxy resin filling can prevent the risk of circuit board vibration caused by high-speed rotation of the engine. The outside of the sensor shell is sealed with an O-shaped silica gel sealing ring and the engine mounting seat is installed with interference.

[0157] The camshaft sensor prepared based on the above method has the advantages of high precision, high sensitivity, good temperature stability, strong anti-interference, anti-vibration, low power consumption, etc.

[0158] The above only describes the technical solutions of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the scope of the claims of the present application.

Claims

1. A magnetic tunnel junction, comprising: Free magnetic layer; Reference magnetic layer; An insulating barrier layer is disposed between the free magnetic layer and the reference magnetic layer; And an intermediate layer, the intermediate layer being disposed on the side of the reference magnetic layer away from the insulating barrier layer, the intermediate layer including a stabilizing layer disposed close to the reference magnetic layer, wherein the constituent material of the reference magnetic layer includes N elements, the N elements including one unstable element, the constituent material of the stabilizing layer includes M elements, the M elements including the unstable element, and N and M are both integers greater than 1.

2. The magnetic tunnel junction according to claim 1, wherein, The free magnetic layer and the reference magnetic layer are composed of Co. x Fe y Re z The Re element is the unstable element, and the Re element includes at least one of aluminum (Al), boron (B), selenium (Si) and manganese (Mn). x, y and z represent the proportions of Co, Fe and Re elements, respectively.

3. The magnetic tunnel junction according to claim 2, wherein, The thickness of the reference magnetic layer is greater than the thickness of the free magnetic layer.

4. The magnetic tunnel junction according to claim 2, wherein, The stabilizing layer is composed of the Re element.

5. The magnetic tunnel junction according to claim 1 or 2, wherein, Also includes: A pinning layer is disposed on the side of the intermediate layer opposite to the reference magnetic layer, and the constituent material of the pinning layer includes at least one of cobalt iron boron (CoFeB), cobalt iron (CoFe), nickel iron (NiFe), iron gallium boron (FeGaB), Co (cobalt), iron (Fe), nickel iron cobalt (NiFeCo), and cobalt niobium zirconium (CoNbZr). An antiferromagnetic layer is disposed on the side of the pinning layer opposite to the intermediate layer, and the constituent material of the antiferromagnetic layer includes at least one of platinum manganese alloy (PtMn), iridium manganese alloy (IrMn), and iron manganese alloy (FeMn).

6. The magnetic tunnel junction according to claim 5, wherein, The intermediate layer also includes: A coupling layer is disposed between the stabilizing layer and the pinning layer, and the constituent material of the coupling layer includes at least one of ruthenium (Ru) and thallium (Ta).

7. The magnetic tunnel junction according to claim 1, wherein, The thickness of the insulating barrier layer ranges from 0.8 to 1.2 nanometers, and the constituent materials of the insulating barrier layer include at least one of magnesium borate (Mg3B2O6), aluminum oxide (Al2O3), and magnesium oxide (MgO).

8. The magnetic tunnel junction according to claim 1, wherein, Also includes: A first isolation layer is disposed on the side of the free magnetic layer away from the insulating barrier layer, and the constituent material of the first isolation layer includes at least one of tantalum (Ta) and ruthenium (Ru); The second isolation layer is disposed on the side of the first isolation layer away from the free magnetic layer, and the constituent material of the second isolation layer includes magnesium (mg). A conductive layer is disposed on the side of the second isolation layer opposite to the first isolation layer, and the constituent material of the conductive layer includes at least one of platinum (Pt), gold (Au), tungsten (W), aluminum (Al), copper (Cu), silver (Ag), ruthenium (Ru), thallium (Ta), and titanium (Ti); A buffer layer is disposed on the side of the intermediate layer opposite to the reference magnetic layer, and the buffer layer is composed of at least one of platinum (Pt), gold (Au), tungsten (W), aluminum (Al), copper (Cu) and titanium (Ti).

9. A method for preparing a magnetic tunnel junction, comprising: Provide a base layer; An intermediate layer, a reference magnetic layer, an insulating barrier layer, and a free magnetic layer are sequentially formed on the substrate layer using a magnetron sputtering process. The intermediate layer includes a stabilizing layer disposed close to the reference magnetic layer. The reference magnetic layer is composed of N elements, one of which is an unstable element. The stabilizing layer is composed of M elements, including the unstable element. N and M are both integers greater than 1.

10. The method according to claim 9, wherein after sequentially forming an intermediate layer, a reference magnetic layer, an insulating barrier layer, and a free magnetic layer on the substrate layer using a magnetron sputtering process, the method further comprises: Annealing heat pretreatment is performed on the intermediate layer, the reference magnetic layer, the insulating barrier layer and the free magnetic layer within a first temperature range for a first duration; The temperature range is increased from the first temperature range to the second temperature range. Within the second temperature range, the intermediate layer, the reference magnetic layer, the insulating barrier layer, and the free magnetic layer are subjected to annealing heat treatment for a second duration. A preset magnetic field strength is applied to the reference magnetic layer.

11. A camshaft sensor comprising a magnetic tunnel junction as described in any one of claims 1-8.

12. The camshaft sensor according to claim 11, wherein the rising edge time range of the camshaft sensor is 0.4~2.6μs, and the falling edge time range of the camshaft sensor is 0.2~1.2μs.

13. The camshaft sensor according to claim 11, comprising a sensor housing, wherein a sensor chip including the magnetic tunnel junction is disposed within the sensor housing, and the sensor chip is disposed in contact with the bottom of the sensor housing.

14. The camshaft sensor according to claim 13 further includes a magnet, the magnet being disposed on the side of the sensor chip away from the bottom of the sensor housing, and the magnetic field strength of the magnet having a corresponding relationship with the sensitivity parameter of the sensor chip.

15. The camshaft sensor of claim 14, wherein the sensitivity parameters include signal time and / or magnetoresistive rate of change, wherein the signal time is positively correlated with the magnetic field strength, and the magnetoresistive rate of change is negatively correlated with the magnetic field strength.

16. The camshaft sensor according to claim 14 or 15, wherein the magnet is a samarium cobalt magnet, and the magnetic field strength of the ferromagnetic element is in the range of 200~355mT.

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