JP5398669B2 - Magnetic level shifter - Google Patents

Description

  The present invention relates to a level shift technique, and more particularly to a magnetic level shifter using a magnetoresistive effect element.

  The magnetoresistive (MR) effect is a phenomenon in which an electric resistance changes when a magnetic field is applied to a magnetic material, and is used for operations of a magnetic field sensor, a magnetic head, and the like. Non-patent Documents 1 and 2 below disclose artificial lattice films such as Fe / Cr and Co / Cu as giant magnetoresistance (GMR) effect materials that exhibit a very large magnetoresistance effect.

  In addition, a magnetic layer using a laminated structure comprising a ferromagnetic layer / nonmagnetic layer / ferromagnetic layer / antiferromagnetic layer including a nonmagnetic metal layer (nonmagnetic layer) that is thick enough to eliminate the exchange coupling action between the ferromagnetic layers. Resistive effect elements have been proposed. In this stacked structure, one ferromagnetic layer (pinned layer) exchange-couples with the antiferromagnetic layer and its magnetic moment is fixed, and only the spin of the other ferromagnetic layer (free layer) is easily caused by an external magnetic field. Invert. This is an element known as a so-called “spin valve film”.

  In a magnetoresistive element using a spin valve film, since the exchange coupling between two ferromagnetic layers is weak, the spin of the free layer can be reversed by a small external magnetic field. For this reason, a magnetoresistive element using a spin valve film can obtain higher sensitivity than an element using an exchange coupling film.

  The spin valve film is used in a reproducing head for high-density magnetic recording, and a current flows in the in-plane direction when used. As antiferromagnetic materials used for the spin valve film, FeMn, IrMn, PtMn and the like are known. On the other hand, Non-Patent Document 3 below shows that a larger magnetoresistance effect can be obtained by using a perpendicular magnetoresistance effect in which a current flows in a direction perpendicular to the film surface.

  Non-Patent Document 4 below shows a tunneling magneto-resistive (TMR) effect by a ferromagnetic tunnel junction. The tunnel magnetoresistance is a film surface perpendicular direction when the spins of two ferromagnetic layers are made parallel and antiparallel to each other by an external magnetic field in a three-layer film composed of a ferromagnetic layer / insulating layer / ferromagnetic layer. This utilizes the difference in the magnitude of the tunnel current.

  Studies are also underway to use GMR elements and TMR elements as magnetic field detectors. In this case, the use of a pseudo spin valve type in which a nonmagnetic metal layer is sandwiched between two ferromagnetic layers having different coercive forces, or the above-described spin valve type magnetoresistive effect element has been studied.

  When a GMR element or a TMR element is used for a magnetic field detector, the relative angle between two magnetic layers of each element is configured to change in response to an external magnetic field. Since the resistance value of each element changes according to the relative angle between the two magnetic layers, for example, a magnetic field can be detected by detecting a change in voltage by applying a constant current to each element. This voltage signal is read using the GMR effect or the TMR effect. A magnetic field detector using a GMR element or a TMR element has a feature that it can perform not only high-precision magnetic field detection but also stable operation even at high temperatures.

  It is also known that a high-performance magnetic field detector can be realized by configuring a bridge circuit using a plurality of magnetoresistance effect elements and combining elements whose magnetization directions of the fixed layer are opposite (for example, Patent Document 1) below.

  When a current is passed through the wiring, a magnetic field is generated around it. If the magnetic field is detected using a magnetoresistive element, the current flowing through the wiring is used as an input signal, and the voltage output of the magnetoresistive element is used as an output signal. A level shifter can be configured. A level shift technique using magnetism is disclosed, for example, in Patent Document 2 below.

  As a level shift technique, a technique using an optical system is well known. A level shifter based on an optical system requires a light emitting element that converts an input electrical signal into light and a light receiving element that receives the optical signal and converts it back into an electrical signal. However, since these are mounted externally, the level shifter can be downsized. Difficult and mechanical reliability issues are a concern. Further, due to the temperature characteristics of the light emitting element and the light receiving element, it is difficult to operate at high temperatures.

  As another level shift technique, a technique using capacitive coupling is known (Patent Document 3 below). The capacitively coupled level shift element has a feature that it can be easily monolithically formed on an IC chip. However, since there is a limit to the thickness of the insulating layer to ensure the necessary capacity, it is difficult to increase the breakdown voltage, and the strength against surge noise may be a problem.

  On the other hand, in the magnetic level shift technology, a wiring for inputting a signal and a magnetoresistive effect element for outputting a signal are required. However, since they can be formed on the same substrate by using a semiconductor device manufacturing process, monolithic formation is possible. Easy. Further, since the magnetic field can maintain a constant intensity even at spatially separated positions like light, an electrical connection is not required between the input side and the output side, and a level shifter having high insulation can be realized.

Japanese Patent No. 3017061 JP 2005-515667 A Japanese Patent Laid-Open No. 11-136293

D. H. Mosca et al., "Oscillatory composite coupling and giant magnetoresistance in Co / Cu multilayers", Journal of Magnetism and Magnetic Materials 94 (1991) pp.L1-L5 S. S. P. Parkin et al., "Oscillatory Magnetic Exchange Coupling through Thin Copper Layers", Physical Review Letters, vol.66, No.16, 22 April 1991, pp.2152-2155 W. P. Pratt et al., "Perpendicular Giant Magnetoresistances of Ag / Co Multilayers", Physical Review Letters, vol.66, No.23, 10 June 1991, pp.3060-3063 T. Miyazaki et al., "Giant magnetic tunneling effect in Fe / Al2O3 / Fe junction", Journal of Magnetism and Magnetic Materials 139 (1995), pp.L231-L234

  As described above, the magnetic level shift element has the advantage of being easily monolithic like the capacitive coupling element. However, if a bridge circuit is configured for reliable and stable operation, at least four magnetoresistive elements are required. Thus, since the required element area on the substrate (chip) increases, it is difficult to reduce the size.

  In particular, if a multi-channel level shifter using a bridge circuit is configured on the same substrate, the chip size becomes large, and not only the features of miniaturization and high functionality due to monolithicization are lost, but also the chip cost increases. Therefore, a practical magnetic level shifter that fully utilizes the merits of magnetoresistive elements such as operation stability at high temperatures, high withstand voltage, and high surge noise resistance has not been realized.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a magnetic level shifter capable of suppressing an increase in formation area even when the number of channels is increased.

  The magnetic level shifter according to the present invention is a magnetoresistive effect element that outputs a detection signal in which an input wiring to which an input signal is applied and the input wiring) takes a value corresponding to a magnetic field generated according to the input signal. And a reference element that outputs a fixed reference voltage, and generates an output signal based on a difference between the detection signal and the reference voltage. Is.

  According to the magnetic level shifter according to the present invention, the number of time resistance effect elements required for multi-channeling can be suppressed as compared with the configuration using the conventional bridge circuit. Therefore, the formation area of the magnetic level shifter can be reduced, which can contribute to the downsizing of the device and the reduction of the manufacturing cost.

It is a figure for demonstrating the magnetic field detection operation | movement of a magnetoresistive effect element. It is a graph which shows the relationship between the resistance value of a magnetoresistive effect element, and a magnetic field. 3 is a diagram illustrating a basic configuration of a level shifter according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating a laminated structure of magnetoresistive elements in the level shifter according to the first embodiment. 4 is a partial cross-sectional view of the level shifter according to Embodiment 1. FIG. 3 is a cross-sectional view showing a wiring structure of the level shifter according to the first embodiment. FIG. FIG. 10 is a partial cross-sectional view showing a modification of the level shifter according to the second embodiment. FIG. 10 is a diagram illustrating a basic configuration of a level shifter according to a third embodiment. FIG. 6 is a schematic configuration diagram of a multi-channel type level shifter according to a fourth embodiment. FIG. 10 is a schematic configuration diagram of a multi-channel type level shifter according to a fifth embodiment. FIG. 10 is a schematic configuration diagram of a multi-channel type level shifter according to a sixth embodiment. FIG. 10 is a schematic configuration diagram of a multi-channel type level shifter according to a seventh embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, prior to the description of the magnetic level shifter according to the present invention, the magnetic field detection operation in the magnetoresistive effect element will be described with reference to FIG. As shown in FIG. 1, the spin valve magnetoresistive element 100 includes a laminated structure of a fixed layer 101 (magnetic layer), a nonmagnetic layer 102, and a free layer 103 (magnetic layer).

  In the example of FIG. 1, the magnetization direction 100 b of the free layer 103 in the absence of a magnetic field is set to form an angle of approximately 90 degrees with respect to the magnetization direction 100 a of the fixed layer 101. When a magnetic field is applied in a direction along the magnetization direction 100a of the fixed layer 101, the magnetization direction of the free layer 103 changes to a new direction 100c. At this time, the resistance value of the magnetoresistive effect element 100 is determined according to the angle formed by the magnetization direction 100 b of the free layer 103 and the magnetization direction 100 a of the fixed layer 101.

  That is, when the magnetization direction 100a of the fixed layer 101 is a reference (0 degree) and the angle formed by the magnetization direction 100c of the free layer 103 and the magnetization direction 100a of the fixed layer 101 when a magnetic field is applied is θ, the magnetoresistive element 100 The amount of change in the resistance value R is proportional to cos θ. When the free layer 103 is a soft magnetic film having uniaxial anisotropy, cos θ = H / | Hk |. H is an applied magnetic field, and Hk is an anisotropic magnetic field of the free layer 103.

  FIG. 2 is a graph showing the relationship between the resistance value R of the magnetoresistive effect element 100 and the applied magnetic field H. As shown in the figure, the relationship R = Rm + (ΔR / 2) · (H / | Hk |) is obtained. Here, Rm is an intermediate value between the maximum value and the minimum value of the resistance that the magnetoresistive effect element 100 can take, and is the resistance value of the magnetoresistive effect element 100 when there is no magnetic field. ΔR is the magnetoresistance change rate of the magnetoresistive element 100. Since the resistance value R of the magnetoresistive element 100 is proportional to the magnetic field H, the magnitude of the magnetic field H can be known by measuring the resistance value R. Further, the range of the magnetic field that can be detected in the direction along the magnetization direction 100a of the fixed layer 101, that is, the operation region of the magnetoresistive effect element 100 is H ≦ | Hk |.

<Embodiment 1>
FIG. 3 is a top view showing a basic configuration of the magnetic level shifter according to Embodiment 1 of the present invention. The level shifter is expressed as one detection magnetoresistance effect element 11 (hereinafter referred to as “detection element”) and a pair of reference magnetoresistance effect elements 21 and 31 (hereinafter referred to as “reference elements”). )have.

  Each of the detection element 11 and the reference elements 21 and 31 includes a stacked structure similar to that of the magnetoresistive effect element 100 of FIG. 1, and FIG. 4 shows a specific example of the structure. As shown in FIG. 4, each of the detection element 11 and the reference elements 21 and 31 includes a first electrode layer 105, an antiferromagnetic layer 106, a fixed layer (first magnetic layer) 101, a nonmagnetic layer 102, The free layer (second magnetic layer) 103 and the second electrode layer 107 can be stacked in this order. The magnetization direction of the fixed layer 101 is fixed by the antiferromagnetic layer 106, and the magnetization direction of the free layer 103 changes according to the magnetic field.

  The stacking order of the antiferromagnetic layer 106, the fixed layer 101, the nonmagnetic layer 102, and the free layer 103 is opposite to that in FIG. 4, and the free layer 103, nonmagnetic layer 102, nonmagnetic layer 102, and antiferromagnetic layer 106 are stacked. It may be in order. Further, the antiferromagnetic layer 106 is not necessarily used as long as the same function as the fixed layer 101 in this embodiment can be exhibited. In addition, each of the fixed layer 101, the free layer 103, and the first and second electrode layers 105 and 107 may have a multilayer structure.

  In FIG. 3, the areas of the detection element 11 and the reference elements 21 and 31 are the same, and their element resistances are made equal. Here, when the detection element 11 and the reference elements 21 and 31 have a shape magnetic anisotropy and the shape has a long direction (for example, a rectangle or an ellipse), or the detection element 11 and the reference element When the direction of the easy axis of the elements 21 and 31 is the longitudinal direction of the shape, the magnetization directions 11b, 21b, and 31b in the free layers of the detection element 11 and the reference elements 21 and 31 when there is no magnetic field are This is the longitudinal direction of the element.

  In the present embodiment, the magnetization directions 11b, 21b, 31b in the free layers of the detection element 11 and the reference elements 21, 31 in the absence of a magnetic field are the longitudinal directions of the elements, and as shown in FIG. 11 and the reference elements 21 and 31 are arranged such that the longitudinal direction of the reference elements 21 and 31 forms an angle of 90 degrees with respect to the longitudinal direction of the detection element 11. That is, when there is no magnetic field, the magnetization direction 11b of the free layer of the detection element 11 and the magnetization directions 21b and 31b of the free layers of the reference elements 21 and 31 are different from each other by 90 degrees. The longitudinal directions of the reference elements 21 and 31 are the same, and the magnetization directions 21b and 31b of the free layers in the absence of a magnetic field are the same.

  On the other hand, with respect to the magnetization directions 11 a, 21 a, and 31 a of the fixed layer of each of the detection element 11 and the reference elements 21 and 31, the magnetization direction 11 a of the fixed layer of the detection element 11 and the magnetization direction of the fixed layer of the reference element 21. The magnetization direction 21a of the fixed layer of the reference element 21 and the magnetization direction 31a of the fixed layer of the reference element 31 are antiparallel (parallel and opposite directions) to each other. Is set.

  Therefore, in the detection element 11, the magnetization direction 11b of the free layer in the absence of a magnetic field is orthogonal to the magnetization direction 11a of the fixed layer in the element plane. In the reference element 21, the magnetization direction 21b of the free layer in the absence of a magnetic field is parallel to the magnetization direction 21a of the fixed layer. Further, in the reference element 31, the magnetization direction 31b of the free layer when no magnetic field is applied is antiparallel to the magnetization direction 31a of the fixed layer.

  A signal detection wiring 111 for extracting an output voltage (detection signal) is connected to the free layer and the fixed layer of the detection element 11. Similarly, a signal detection wiring 211 is connected to the free layer and the fixed layer of the reference element 21, and a signal detection wiring 311 is connected to the free layer and the fixed layer of the reference element 31. The signal detection wirings 111, 211, and 311 are connected to a detection circuit (not shown). These signal detection wirings 111, 211, and 311 function as output wirings of the level shifter.

  Further, a magnetic field generating wiring 112 that functions as an input wiring for inputting an input signal of the level shifter is disposed in the vicinity of the detection element 11. The magnetic field generation wiring 112 is electrically isolated from the detection element 11 via an insulating film. For example, the magnetization direction 11b of the free layer of the detection element 11 in the absence of a magnetic field is directly above or below the detection element. Arranged parallel to When a current or voltage as an input signal of the level shifter is applied to the magnetic field generation wiring 112, a magnetic field is generated around it, but the magnetic field generation wiring 112 is arranged at a position where the detection element 11 can detect the generated magnetic field. Established.

The fixed layer and the free layer of each of the detection element 11 and the reference elements 21 and 31 are ferromagnetic materials. Examples of ferromagnetic materials include Co, Fe, Co—Fe alloys, Co—Ni alloys, Co—Fe—Ni alloys, Fe—Ni alloys, and the like, alloys containing Co, Ni, and Fe as main components, and Ni. -mn-Sb, there are Heusler alloys such as Co ₂ -Mn-Ge. Further, the nonmagnetic layer may be an insulator such as an oxide, fluoride, or nitride of a metal such as Al, Ta, Si, or Mg, or may have a laminated structure thereof.

  As described above, the pinned layers of the detection element 11 and the reference elements 21 and 31 are laminated on the antiferromagnetic layer to fix the magnetization direction. That is, the antiferromagnetic layer fixes the spin direction of the fixed layer, so that the magnetization direction of the fixed layer is kept constant. As a material of the antiferromagnetic layer, a ferromagnetic material such as Fe having a large coercive force, a noble metal, a compound of at least one of Fe and Ni and manganese or oxygen (for example, Ir—Mn, Ni—Mn, Ni—O, Fe— Mn, Pt—Mn, etc.).

  Each layer constituting the laminated structure of the detection element 11 and the reference elements 21 and 31 is formed by DC magnetron sputtering. Alternatively, it may be formed by molecular beam epitaxy (MBE), various sputtering methods, chemical vapor deposition (CVD), or vapor deposition.

  The patterning of the detection element 11 and the reference elements 21 and 31 can be performed using, for example, a photolithography technique. In the case of using a photolithography technique, after forming a film to be a free layer, a nonmagnetic layer, and a fixed layer, a desired pattern is formed thereon with a photoresist. A desired element shape can be obtained by performing ion milling or reactive ion etching using the photoresist as a mask. Alternatively, a patterning method using electron beam lithography or a focused ion beam may be used.

  The signal detection wirings 111, 211, and 311 are made of a material containing a low resistance metal such as Al, Al alloy, Cu, or Cu alloy.

  It is desirable that the detection element 11 and the reference elements 21 and 31 are simultaneously formed on the same substrate by the same process. When the above-described various film forming methods and photolithography methods are performed simultaneously, variations in film thickness and dimensions of each layer can be extremely reduced, and variations in magnetoresistance in the detection element 11 and the reference elements 21 and 31 can be suppressed. it can. The shapes of the detection element 11 and the reference elements 21 and 31 are not limited to a rectangle, and may be an isotropic shape such as a disk shape as long as the magnetization direction of the free layer can be defined in a desired direction. Although the spin valve film detection element 11 and the reference elements 21 and 31 are shown here, they may be TMR elements. If a TMR element is used, a large output signal can be obtained and each element can be miniaturized.

  The magnetization directions of the fixed layers of the detection element 11 and the reference elements 21 and 31 are set by the following method, for example. First, the device is heated to near the blocking temperature (preferably above the blocking temperature) where the apparent exchange interaction between the antiferromagnetic layer and the pinned layer is weakened, and an external magnetic field that saturates the pinned layer is applied in the desired direction. To do. If the device is cooled in this state, the magnetization direction of the fixed layer is fixed in a fixed direction.

  In this method, it is necessary to locally generate external magnetic fields in different directions in the respective formation regions of the detection element 11 and the reference elements 21 and 31 (in the example of FIG. 3, the detection element 11 and the reference element 21). Since the magnetization directions 11a and 21a of the fixed layer are the same, the direction of the external magnetic field applied to them may be the same). For example, the present invention can be implemented by providing wirings directly above or directly below the detection element 11 and the reference elements 21 and 31, and generating an external magnetic field by supplying currents in different directions to the wirings while the device is heated.

  Alternatively, an external time in the same direction is generated in the entire region where the detection element 11 and the reference elements 21 and 31 are formed, and the detection element 11 and the reference elements 21 and 31 are each subjected to heat treatment near the blocking temperature. A local method may be used. For example, in the case of FIG. 3, in a state where an external magnetic field of the same direction is applied to the entire detection element 11 and reference elements 21 and 31, the detection element 11 and the reference element 21 are subjected to local heat treatment to fix them. The magnetization directions 11a and 21a of the layers are determined, and then the direction of the external magnetic field is reversed, and the reference element 31 is subjected to local heat treatment to determine the magnetization direction 31a of the fixed layer.

  In the present embodiment, a magnetic shield 5 that shields an external magnetic field may be provided around the reference elements 21 and 31. The magnetic shield 5 can be made of a high magnetic permeability material. As the high magnetic permeability material, for example, a Ni—Fe alloy is well known, but other alloys mainly containing Co, Ni, Fe, or the like may be used. When the magnetic shield 5 is provided, since the reference elements 21 and 31 are not affected by the external magnetic field, the magnetization directions 21a and 21b of the fixed layer and the free layer of the reference element 21 are parallel to each other. As long as the magnetization directions 31a and 31b of the fixed layer and the free layer are antiparallel to each other, their directions may be arbitrary.

  Next, the operation of the magnetic level shifter of FIG. 3 will be described. During the operation of the level shifter, a constant current I flows through the detection element 11 and the reference elements 21 and 31 through the signal detection lines 111, 211, and 311, respectively.

  In this state, when a known current or voltage is applied as an input signal to the magnetic field generation wiring 112, the magnetic field H generated by the magnetic field generation wiring 112 is applied to the detection element 11. Thereby, the magnetization direction of the free layer of the detecting element 11 rotates as indicated by an arrow 11c.

The resistance value R of the detection element 11 when the detection element 11 generates the magnetic field H is:
R ₁₁ = Rm + ΔR / 2 × H / | Hk | (1)
Therefore, the output voltage V ₁₁ (detection signal) appearing in the signal detection wiring 111 of the detection element 11 is
V ₁₁ = I × (Rm + ΔR / 2 × H / | Hk |) (2)
It becomes. Here, Rm is the element resistance when a saturation magnetic field is applied to the detection element 11, ΔR is the magnetoresistance change rate of the detection element 11, and Hk is the intensity of the saturation magnetic field.

  In the reference element 21, the magnetization direction 21a of the fixed layer and the magnetization direction 21b of the free layer are always parallel. In the reference element 31, the magnetization direction 31a of the fixed layer and the magnetization direction 31b of the free layer are always constant. Antiparallel. The reference elements 21 and 31 are formed in the same area as the detection element 11, and the magnetoresistance change rate ΔR and the element resistance Rm when a saturation magnetic field is applied are the same as those of the detection element 11. . Therefore, the resistance values of the reference elements 21 and 31 are the same as the resistance values when the positive and negative saturation magnetic fields are respectively applied to the detection element 11.

Therefore, the output voltage V ₂₁ (reference signal) appearing on the signal detection wiring 211 of the reference element 21 and the output voltage V ₃₁ (reference signal) appearing on the signal detection wiring 311 of the reference element 31 are respectively
V ₂₁ = I × (Rm−ΔR / 2) (3)
V ₃₁ = I × (Rm + ΔR / 2) (4)
It becomes.

Therefore, the differential signal [Delta] V ₂₁ obtained by the difference between the output voltage V ₁₁ of the detection element 11 and the output voltage V ₂₁ of the reference element 21,
ΔV ₂₁ = I × (1 + H / | Hk |) × ΔR / 2 (5)
It becomes. Similarly, the differential signal [Delta] V ₃₁ obtained by the difference between the output voltage V ₁₁ of the output voltage V ₃₁ and the detection element 11 of the reference element 31,
ΔV ₃₁ = I × (1−H / | Hk |) × ΔR / 2 (6)
It is expressed.

Furthermore, taking the difference between ΔV ₂₁ and ΔV ₃₁ ,
ΔV ₂₁ −ΔV ₃₁ = I × ΔR × H / | Hk | (7)
It becomes.

Here, the value of ΔR can be obtained each time from the difference between the output signals V ₂₁ and V ₃₁ of the two reference elements ₂₁ and ₃₁ . This is because in this embodiment, the saturation magnetic fields of the detection element 11 and the reference elements 21 and 31 are constant known values, and the resistance change rate can be calculated from the magnetic resistance in the saturation magnetic field. Therefore, even when the resistance value varies between devices or the resistance value changes due to temperature characteristics, the resistance change rate ΔR can be obtained every time measurement is performed, and the accurate resistance change rate ΔR in an actual use environment can be obtained. Can be used to detect the magnetic field H.

According to the level shifter of FIG. 3, the voltage signals V ₁₁ , V ₂₁ , V ₃₁ appearing on the signal detection wirings 111, 211, 311 of the detection element 11 and the reference elements ₂₁ , _31, and the above formulas (5) to (5) By using any one of (7), an output signal corresponding to the input signal input to the magnetic field generation wiring 112 can be obtained. That is, a reference signal is generated from the output voltages V ₂₁ and V ₃₁ of the reference elements ₂₁ and ₃₁ , and an output signal can be obtained by comparing the reference signal with the voltage signal V ₁₁ of the detection element 11.

  As described above, in the level shifter of the present embodiment, the output signal corresponding to the input signal input to the magnetic field generation wiring 112 is detected by the detection element 11 and the reference element 21 that are electrically separated from the magnetic field generation wiring 112. , 31 can be obtained. With this configuration, it is possible to increase the withstand voltage by increasing the thickness of the insulating film between the magnetic field generating wiring 112 and the detection element 11, and a level shifter having excellent surge resistance can be obtained.

The differential signals represented by the above equations (5) to (7) are calculated by quantifying the output voltages V ₁₁ , V ₂₁ , V ₃₁ of the detection element 11 and the reference elements ₂₁ , _31. It may be obtained by processing. The above ΔV ₂₁ and ΔV ₃₁ can also be obtained by configuring a bridge circuit using the detection element 11 and the reference elements 21 and 31, but it should be noted that the formation area increases. is there.

  In the present embodiment, it has been described that a constant current flows through each of the detection element 11 and the reference elements 21 and 31, but may not be constant as long as the ratio of the magnitudes of the respective currents is known. If the ratio of the magnitudes of the currents flowing through the detection element 11 and the reference elements 21 and 31 is known, the magnetic field H generated by the magnetic field generation wiring 112 can be detected by the same calculation as described above. Further, here, in the detection element 11, the magnetization direction 11a of the fixed layer and the magnetization direction 11b of the free layer in the absence of a magnetic field are orthogonal to each other in the element plane. If the relationship between the two is not parallel or antiparallel, the magnetic field H generated by the magnetic field generation wiring 112 can be detected using the detection element 11.

According to the present embodiment, a large output signal can be obtained because the differential signals obtained from the output voltages V ₁₁ , V ₂₁ and V _{31 of} the detection element 11 and the reference elements 21 and ₃₁ are used. Furthermore, since the resistance change rate ΔR of the detection element 11 and the reference elements 21 and 31 can be obtained from the output signals of the reference elements 21 and 31 each time, the detection element 11 and the reference elements 21 and 31 Even when the resistance value varies from device to device or when the resistance value changes due to a temperature change in the use environment, a highly reliable output signal can be stably obtained. Further, if both the maximum value and the minimum value of the output voltage of the detection element 11 are known from the output voltages V ₂₁ and V _{31 of} the reference elements ₂₁ and ₃₁ , and they are used for arithmetic processing, high reliability and accuracy can be obtained. Can be expected.

  Next, the structure of the detection element 11 will be described. FIG. 5 is a diagram showing an example of the structure of the level shifter according to the first embodiment. A part of the formation region of the detection element 11 (detection element portion) and the formation region of the logic integrated circuit (logic circuit portion) are shown. It is a fragmentary sectional view shown.

  As shown in FIG. 5, the level shifter is formed on the same substrate 400. The substrate 400 may be Si that has been widely used in power devices conventionally, but SiC, GaN, oxide semiconductors that have been attracting attention in recent years as semiconductor materials that can realize power devices with high breakdown voltage, low loss, and high heat resistance, A wide band gap semiconductor such as a diamond semiconductor can also be used.

  In the logic circuit region, a transfer gate transistor 501 including a gate insulating film 411, a gate electrode 412, and a sidewall 413 is formed. The transfer gate transistor 501 is covered with an interlayer insulating film 410.

  A contact 414 that connects the transfer gate transistor 501 and the upper wiring 425 is formed in the interlayer insulating film 410. The contact (connection member) 414 is formed by forming a contact hole penetrating the interlayer insulating film 410, forming a tungsten film on the interlayer insulating film 410 so as to fill the hole, and performing CMP (Chemical) on the tungsten film. This is performed by performing an etch back process using a mechanical polishing (RIE) process or an RIE (Reactive Ion Etching) method. As a material for the contact 414, in addition to tungsten, silicon, metals such as aluminum, copper, titanium, and tantalum, alloys of these metals, nitrides, and the like can be used. In addition to the above method, the contact 414 may be formed by a plating method, a sputtering method, a CVD method, or the like.

  On the other hand, in the detection element portion, the detection element 11 is formed on the interlayer insulating film 410. The detection element 11 is formed by forming a predetermined multilayer film structure (see FIG. 4) on the interlayer insulating film 410 and patterning it into a predetermined shape. As described above, the detection element 11 may be a TMR element using a tunnel insulating film as a nonmagnetic layer, or a GMR element using a nonmagnetic conductive layer and utilizing the GMR effect in the direction perpendicular to the film surface.

  In FIG. 5, as means for obtaining an output voltage from the detection element 11 (corresponding to the detection element 11 in FIG. 3), wirings 421 and 424 respectively connected to the upper and lower sides of the detection element 11 are provided. Although the contact 423 is interposed between the detection element 11 and the wiring 424 thereon, the contact 423 may be directly connected therebetween.

  Conversely, in FIG. 5, the detection element 11 and the wiring 421 thereunder are directly connected, but a contact (connection member) may be interposed therebetween. The contact provided in that case is preferably formed using a low-resistance metal such as ruthenium, copper, aluminum, or tantalum. Further, the thickness is preferably 300 nm or less so that the flatness of each layer constituting the detection element 11 is not impaired.

  Further, the detection element 11 and the wirings 421 and 424 may be formed in a layer immediately above the substrate 400 as shown in FIG.

As a ferromagnetic material for each magnetic layer of the detection element 11 (corresponding to the fixed layer 101 and the free layer 103 in FIG. 4), a magnetic material mainly composed of nickel, iron, and / or cobalt is preferable. For the purpose of improving characteristics and thermal stability, additives such as boron, nitrogen and silicon may be introduced. For example, when a half metal material such as NiMnSb or Co ₂ MnGe is used, since the energy gap exists in one spin band, the half metal can obtain a larger magnetoresistance effect, thereby obtaining a large signal output. Can do. The thickness of each magnetic layer is preferably about 0.3 to 50 nm.

  The magnetic layer serving as the fixed layer of the detection element 11 is not limited to a single layer structure, and may be a ferromagnetic / nonmagnetic / ferromagnetic laminated structure such as CoFe / Ru / CoFe. If such a laminated structure is used to design a film structure that can suppress leakage components due to magnetization of the fixed layer, a more stable magnetic detection operation can be performed.

  Examples of the nonmagnetic material that becomes the nonmagnetic layer of the detection element 11 (corresponding to the nonmagnetic layer 102 in FIG. 4) include metals such as aluminum, silicon, tantalum, and magnesium, and alloys thereof, oxides of these metals and alloys, or Nitride is used. The nonmagnetic layer is formed as thin as about 0.3 to 5 nm. The thickness of the antiferromagnetic layer (corresponding to the antiferromagnetic layer 106 in FIG. 4) varies depending on the material used and is preferably in the range of 0.3 nm to 50 nm.

  In this embodiment, a platinum manganese alloy with a thickness of 20 nm as an antiferromagnetic layer, a cobalt iron alloy with a thickness of 3 nm as a fixed layer (ferromagnetic layer), an aluminum oxide with a thickness of 1 nm as a nonmagnetic layer (tunnel insulating layer), a free layer As the layer (ferromagnetic layer), a nickel iron alloy having a thickness of 3 nm was used. Each of these layers can be formed by using a normal thin film forming technique such as a molecular beam epitaxy (MBE) method, various sputtering methods, a chemical vapor deposition (CVD) method, or an evaporation method. .

  In the present embodiment, the detection element 11 (and reference elements 21 and 31 (not shown)) are covered with the protective film 422 (in other words, the insulating film on the detection element 11 is replaced with the protective film 422. The interlayer insulating film 410 has a two-layer structure). The protective film 422 functions to protect the magnetoresistive effect element from damage in a dry etching process and a cleaning process performed after the detection element 11 is formed.

  For example, when a silicon oxide film is formed on the detection element 11 as the interlayer insulating film 420, the magnetic layer is oxidized in an oxidizing atmosphere at about 400 ° C. May deteriorate. For the purpose of preventing oxidation of the magnetic layer, the protective film 422 may be a thin film that can be formed in a non-oxidizing atmosphere such as a silicon nitride film. By covering the surface of the detection element 11 with a protective film 422 made of a silicon nitride film, the detection element 11 is protected from oxidation.

  As the protective film 422, at least one of an insulating metal nitride, an insulating metal carbide, a metal oxide formed by oxidation of a metal having a lower free energy of oxide generation than Fe, or an organic film such as polyimide is used. It is good that contains. When the protective film 422 made of such a material is used, oxidation of the detection element 11 can be suppressed in the manufacturing process of the detection element 11 using the magnetic layer containing at least Fe. As a result, a magnetic level shifter that is easy to manufacture and has stable operating characteristics can be obtained. In addition, since the interlayer insulating film 430 can be formed thick while preventing damage to the detection element 11, it can also contribute to the high breakdown voltage of the level shifter.

  However, when the protective film 422 having a relatively high dielectric constant such as a silicon nitride film is used, the following should be noted. In the logic circuit section, it is necessary to set the capacitance between the wirings and the wiring resistance in consideration of the operation speed and access timing of the circuit. Therefore, when an insulating film having a high dielectric constant is formed in the logic circuit portion, the inter-wiring capacitance in the logic circuit portion may deviate from the design parameters, and the circuit may malfunction. Therefore, the protective film 422 having a high dielectric constant is preferably not provided in the logic circuit portion unless necessary.

  The wiring 421 is formed on the interlayer insulating film 410, and the detection element 11 is formed thereon. The contact 423 is formed by forming a protective film 422 and an interlayer insulating film 420 on the detection element 11, and then forming a contact hole reaching the detection element 11 in the protective film 422 and the interlayer insulating film 420. It is formed by embedding. A wiring 424 having a predetermined pattern is formed on the interlayer insulating film 420.

  An interlayer insulating film 430 is further formed on the interlayer insulating film 420. In the example of FIG. 5, a contact 431 connected to the wiring 441 on the interlayer insulating film 430 in the logic circuit portion is illustrated. The contact 431 can be formed using a material and a formation method similar to those of the contact 414 described above.

  On the other hand, in the detection element portion, a magnetic field generating wiring 112 is formed on the interlayer insulating film 430. Here, a configuration is shown in which the magnetic field generation wiring 112 is provided above the detection element 11 (on the side far from the substrate 400), but the magnetic field generation wiring 112 applies a magnetic field corresponding to the input signal to the detection element 11. For example, it may be disposed below the detection element 11 (on the side close to the substrate 400). In order to efficiently apply a magnetic field to the detection element 11, the magnetic field generation wiring 112 is preferably disposed immediately above or immediately below the detection element.

  In this embodiment, the upper surface and both side surfaces of the magnetic field generating wiring 112 formed above the detection element 11 are coated with a high magnetic permeability material 112a (magnetic material) as shown in FIG. Thereby, the leakage magnetic field from the magnetic field generating wiring 112 upward and laterally can be suppressed, and the magnetic field generated by the magnetic field generating wiring 112 can be efficiently applied to the detection element 11. As a result, malfunction of the detection element 11 is suppressed, and a level shifter that operates stably in various environments can be obtained. In addition, since the magnetic field is efficiently applied from the magnetic field generation wiring 112 to the detection element 11, the interlayer insulating film 430 therebetween can be made thicker, which can contribute to the high withstand voltage of the level shifter.

  The high magnetic permeability material 112a is desirably formed on three sides other than the surface facing the detection element 11 of the magnetic field generating wiring 112. For example, when the magnetic field generation wiring 112 is disposed below the detection element 11, the lower surface and both side surfaces of the magnetic field generation wiring 112 may be covered with a high permeability material 112a.

  In the present embodiment, only one magnetic field generating wiring 112 for applying a magnetic field according to an input signal to the detection element 11 is provided, but two or more magnetic wirings may be provided. For example, if a plurality of detection elements 11 are arranged in parallel, the strength of the magnetic field applied to the detection elements 11 can be increased, and the application range of the magnetic field can be expanded. Further, if leakage current flows through a part of the plurality of magnetic field generation wirings 112, a part of the leakage magnetic field can be canceled.

  Here, the material of each wiring will be described. Copper, metal such as tantalum, silicon, tungsten, aluminum, titanium, ruthenium, alloys thereof, compounds, or the like can be applied to the wiring 421 directly connected to the detection element 11. The same applies to the other wirings 424, 425, 441 and the magnetic field generating wiring 112, but when copper is used, it is formed using a damascene method, and a metal such as tantalum, silicon, tungsten, aluminum, titanium, ruthenium, or the like is formed. When these alloys, compounds, and the like are applied, a thin film is formed by sputtering or the like, and then patterned by performing a photolithography technique and dry etching.

  If it is assumed that the product will be exposed to a high temperature atmosphere during the manufacturing process or device use, and there is a concern about mutual diffusion between the wiring and the member in contact with the heat, a diffusion prevention layer is provided on the surface of the wiring. It is good to leave. As the diffusion preventing layer, metals such as titanium, tantalum, and ruthenium, and alloys and nitrides thereof can be used.

  In the present embodiment, the output signals (detection signal and reference signal) of the detection element 11 and the reference elements 21 and 31 have been described as voltage signals, but these may be current signals. The same applies to the following embodiments.

<Embodiment 2>
In the second embodiment, a modification example of the configuration of the level shifter shown in FIG. 5 is shown. FIG. 7 is a partial cross-sectional view showing the structure of the level shifter according to the second embodiment. In this embodiment mode, the wiring 421 connected to the detection element 11 is connected to the source or drain of the transfer gate transistor 502. In FIG. 7, elements having the same functions as those shown in FIG. 5 are denoted by the same reference numerals, and description thereof is omitted here.

  In FIG. 5, the detection element 11, the wirings 421 and 424 and the contacts 423 connected to the detection element 11, and the protective film 422 covering the detection element 11 are formed on the lowermost interlayer insulating film 410. In the embodiment, they are formed on the second-layer interlayer insulating film 420. Since the interlayer insulating film 450 that covers the detection element 11 is provided above the interlayer insulating film 420, two layers of interlayer insulating films 430 and 450 exist between the wiring 441 and the wiring 425 in the logic circuit portion. Become. Therefore, the contact 431 connecting the wiring 441 and the wiring 425 is formed so as to penetrate the interlayer insulating films 430 and 450.

  An element isolation insulating film 401 and a transfer gate transistor 502 are provided on the substrate 400 of the detection element portion. The transfer gate transistor 502 has a structure including a gate insulating film 415, a gate electrode 416, and a sidewall 417, similarly to the transfer gate transistor 501 in the logic circuit portion. The wiring 421 connected to the detection element 11 is connected to the source or drain of the transfer gate transistor 502 through the wiring 426 and the contact 418 formed in the lower layer.

<Embodiment 3>
FIG. 8 is a diagram illustrating a basic configuration of the level shifter according to the third embodiment. The level shifter includes a magnetic field generation wiring (compensation wiring) 113 capable of applying a known magnetic field (compensation magnetic field) in order to compensate the resistance value of the detection element 11 separately from the magnetic field generation wiring 112. ing. The compensation wiring 113 can apply a compensation electric field Hc to the detection element 11 by flowing a current (compensation current) different from the input signal of the level shifter.

When a compensation magnetic field Hc is applied to the detection element 11 from the compensation wiring 113 while a constant current I is supplied to the detection element 11 and the reference element 21, the output voltage V11 of the detection element ₁₁ is
V ₁₁ = I × (Rm + ΔR / 2 × Hc / | Hk |) (8)
It becomes. On the other hand, the output voltage V ₂₁ of the reference device 21 is above equation (3), the differential signal obtained by the difference between the output voltage V ₁₁ of the detection element 11 and the output voltage V ₂₁ of the reference device 21 ΔV ₂₁ is,
ΔV ₂₁ = V ₁₁ −V ₂₁ = I × (1 + Hc / | Hk |) × ΔR / 2 (9)
It becomes. Here, ΔR can be obtained from, for example, the difference between the output voltage of the detection element 11 and the output voltage of the reference element 21 when there is no magnetic field, and further uses the current I and the compensation magnetic field Hc that are known values. Thus, the saturation magnetic field Hk of the detection element 11 can be calculated. For example, when the temperature changes during the operation of the level shifter, if the saturation magnetic field Hk is compensated as necessary, an error due to the fluctuation of the saturation magnetic field Hk can be compensated, and the operation reliability of the level shifter is improved. Further, it is not necessary to use an external magnetic field generator to compensate the saturation magnetic field Hk. According to the present embodiment, since the relationship between the resistance of the detecting element 11 and the magnetic field can be determined, high-precision operation including level shift of the analog signal is possible, and further multi-function of the magnetic level shifter can be expected. .

  In the absence of an external magnetic field, the saturation magnetic field Hk can be calculated by measuring only one compensation magnetic field Hc with the detection element 11. If the external magnetic field exists and is constant, the saturation magnetic field Hk can be calculated by measuring two compensation magnetic fields Hc (for example, −Hc and + Hc) with the detecting element 11.

  Similar to the magnetic field generation wiring 112, it is preferable to provide a high permeability material on the surface of the compensation wiring 113 except for the surface facing the detection element 11. Thereby, the compensation magnetic field Hc can be efficiently applied from the compensation wiring 113 to the detection element 11.

Further, since the magnetization rotation speed of the magnetoresistive effect element is as high as nanosecond order, without providing the compensation wiring 113, the operation of the level shifter is divided in time to provide a period for compensation of the saturation magnetic field Hk, A compensation operation for the saturation magnetic field Hk may be performed using the magnetic field generation wiring 112. That is, flow alternating with current and compensation current of the input signal to the magnetic field generating wire 112, from the output voltage V ₁₁ of the detection element 11 at the timing of flowing the compensation current by performing calculation of the saturation magnetic field Hk Good.

  Further, in the present embodiment, the configuration in which the saturation magnetic field Hk is compensated using the output voltage of the detection element 11 used for the normal operation of the level shifter has been described. However, a magnetoresistive effect element dedicated to the saturation magnetic field Hk compensation is separately provided. You may also receive. In this case, the saturation magnetic field Hk can be performed simultaneously with the normal operation, and the value of the compensated saturation magnetic field Hk can be fed back at any time, so that higher performance and higher accuracy can be achieved. However, it should be noted that the formation area increases because the required magnetoresistive effect element increases.

<Embodiment 4>
When the level shifter according to the present invention is multi-channeled, it can be easily reduced in size as compared with the conventional magnetic level shifter. In the following embodiments, configuration examples of the multi-channel type level shifter according to the present invention will be shown.

  For example, the level shifter (FIG. 3) of the first embodiment is configured by using three magnetoresistive elements, and the element area is reduced to 4 minutes with respect to a general bridge circuit using four magnetoresistive elements. It can be reduced to about 3.

  FIG. 9 is a schematic configuration diagram of a multi-channel type level shifter according to the fourth embodiment, in which the level shifter of the first embodiment is made into four channels. Four detection elements 11, 12, 13, and 14 and four magnetic field generation wirings 112, 122, 132, and 142 are provided for each channel. The detection elements 11, 12, 13, and 14 are connected to signal detection lines 111, 121, 131, and 141, respectively, so that the output voltage of each channel can be obtained. FIG. 9 shows a state in which the input signal of the magnetic field generation wiring 142 is activated.

  Since the level shifter according to the present invention only needs to have one set of reference elements 21 and 31 regardless of the number of channels, the four-channel type level shifter has four detection elements 11 to 14 and two reference elements. A total of six magnetoresistive effect elements 21 and 31 can be used. On the other hand, when a four-channel type level shifter is configured using a conventional bridge circuit, four magnetoresistive effect elements are used for each channel, so a total of 24 magnetoresistive effect elements are required. That is, in the 4-channel type level shifter of the present embodiment, the element area can be reduced to about one-fourth of the conventional one.

<Embodiment 5>
FIG. 10 is a schematic configuration diagram of the multi-channel type level shifter according to the fifth embodiment, which is a modification of the 4-channel type level shifter of FIG. In the level shifter, the arrangement direction and the magnetization direction of the reference elements 21 and 31 are the same as those of the detection elements 11 to 14 with respect to FIG. A folded magnetic field generating wiring 212 for applying a magnetic field is provided.

  As described above, when the magnetoresistive effect element has shape magnetic anisotropy and the shape has a longitudinal direction, or the direction of the easy axis of magnetization of the magnetoresistive effect element is the longitudinal direction of the shape In some cases, the magnetization direction in the free layer when no magnetic field is applied is the longitudinal direction of the element. In the present embodiment, the magnetization direction in the absence of a magnetic field in each of the free layers of the detection elements 11 to 14 and the reference elements 21 and 31 is the longitudinal direction of the elements, and as shown in FIG. Aligned. Thereby, the magnetization directions of the free layers of the detection elements 11 to 14 and the reference elements 21 and 31 in the absence of a magnetic field are all the same. The direction is 90 degrees different from the magnetization direction of the fixed layers of the detection elements 11 to 14 and the reference elements 21 and 31. FIG. 10 shows a state where the input signals of the magnetic field generation wirings 112 and 142 are activated.

  A constant current flows through the magnetic field generating wiring 212 that applies a magnetic field to the reference elements 21 and 31 when the input signal of each channel is activated. As a result, a magnetic field having the same magnitude in the opposite direction is applied to the reference elements 21 and 31. Therefore, the center value (midpoint signal) can be generated from the difference (differential output) between the output voltages of the reference elements 21 and 31 at this time. The midpoint signal corresponds to the output voltage of the magnetoresistive element (resistance value Rm) when there is no magnetic field. Using this midpoint signal as a reference signal, a level shift operation can be performed by comparing the midpoint signal with the output voltages of the detection elements 11 to 14 of each channel.

  Here, the magnetic field generating wirings 112, 122, and 132 that apply the magnetic field to the detecting elements 11 to 14 when the respective input signals are activated are the currents that flow through the magnetic field generating wiring 212 that applies the magnetic field to the reference elements 21 and 31. , 142 is set to the same current. Since the detection elements 11 to 14 and the reference elements 21 and 31 have the same configuration, for example, as shown in FIG. 10, when the input signals of the magnetic field generation wirings 112 and 142 are activated, the detection elements 11 and 14 The magnetization direction of the free layer and the magnetization direction of the free layer of one signal detection wiring 211 are the same.

  In this embodiment, since the magnetization directions of the detection elements 11 to 14 and the reference elements 21 and 31 may all be the same, the manufacturing process is simplified.

  In FIG. 10, each of the detection elements 11 to 14 and the reference elements 21 and 31 has a shape with rounded corners, but the shape may be arbitrary as long as the magnetization direction of the element can be determined. The dimensions of the reference elements 21 and 31 and the detection elements 11 to 14 are not necessarily the same. If the area ratio is known, the vertical and horizontal dimension ratios of the elements may be different.

  Further, the detection elements 11 to 14 and the reference elements 21 and 31 are not necessarily arranged in a line as shown in FIG. 10, and their arrangement may be arbitrary as long as normal operation is possible. Further, the detection elements 11 to 14 and the reference elements 21 and 31 and the arrangement as viewed from the device cross section may be arbitrary as long as normal operation is possible. For example, the detection elements 11 to 14 and the reference elements 21 and 31 may be arranged in different layers. Further, for example, when the reference elements 21 and 31 are arranged in the upper and lower layers with the magnetic field generation wiring 212 interposed therebetween, the reference elements 21 and 31 are opposite to each other without forming the magnetic field generation wiring 212 in a folded shape. Can be applied.

  The current to the magnetic field generating wiring 212 may be supplied from an independent power supply circuit or may be supplied from the power supply circuit for the magnetic field generating wirings 112, 122, 132, 142 via a switching element or the like. When an independent power supply circuit is used, currents of different magnitudes are used in the magnetic field generation wiring 212 of the reference elements 21 and 31 and the magnetic field generation wirings 112, 122, 132, and 142 of the detection elements 11 to 14, respectively. May be supplied. For example, if a current for applying a saturation magnetic field to the reference elements 21 and 31 is passed through the magnetic field generating wiring 212, the reference elements 21 and 31 are saturated and the level shifter of FIG. 10 is substantially the same as the level shifter of FIG. Can be operated.

<Embodiment 6>
FIG. 11 is a schematic configuration diagram of a multi-channel type level shifter according to the sixth embodiment, which is a modification of the 4-channel type level shifter of FIG. In the level shifter, the arrangement direction of the reference elements 21 and 31 is rotated by 90 degrees with respect to FIG. That is, the longitudinal direction of the reference elements 21 and 31 is 90 degrees different from the longitudinal direction of the detection elements 11 to 14. Therefore, in the present embodiment, the detection elements 11 to 14 and the reference elements 21 and 31 have the magnetization directions of the free layer in the absence of a magnetic field different from each other by 90 degrees.

  On the other hand, the magnetization directions of the detection elements 11 to 14 and the reference elements 21 and 31 fixed layer are the same as those in FIG. Therefore, in the absence of a magnetic field, the magnetization directions of the fixed layer and the free layer of the reference element 21 are the same, and the magnetization directions of the fixed layer and the free layer of the reference element 31 are opposite to each other. Also in the level shifter of FIG. 11, the reference elements 21 and 31 are provided with a folded magnetic field generating wiring 212.

  In the present embodiment, the direction of the magnetic field applied from the magnetic field generating wiring 212 to the reference elements 21 and 31 is the direction along the magnetization direction of those free layers when there is no magnetic field, that is, the reference elements 21 and 31. It is the longitudinal direction (magnetization easy axis direction). However, as described above, the magnetic fields applied from the magnetic field generating wiring 212 to the reference elements 21 and 31 are opposite to each other.

  Therefore, if a magnetic field having a strength that causes magnetization reversal of the free layers of the reference elements 21 and 31 is applied from the magnetic field generating wiring 212, the relationship between the magnetization directions of the fixed layer and the free layer of the reference elements 21 and 31 is In the same direction and the other in the opposite direction. Accordingly, the level shifter of FIG. 11 can be operated substantially in the same manner as the level shifter of FIG.

  In addition, since the reference elements 21 and 31 are equal to the maximum resistance state or the minimum resistance state of the detection elements 11 to 14, even if the resistance change rate of the detection elements 11 to 14 changes due to a temperature change, The resistance change rate can be calculated from the output voltages of the reference elements 11 and 21. Therefore, not only stable operation from low temperature to high temperature is possible, but also the external magnetic field can be detected with high accuracy using the resistance change rate in the actual use environment, and a highly reliable level shifter can be obtained.

<Embodiment 7>
FIG. 12 is a schematic configuration diagram of a multi-channel type level shifter according to the seventh embodiment, showing an example of a 4-channel type level shifter. The level shifter of the present embodiment includes four detection elements 11 to 14 for each channel and four reference elements 21 to 24 for each channel. The detection elements 11 to 14 and the reference elements 21 to 24 are all set to have the same magnetization direction. Further, signal detection wirings 211 to 224 are connected to the reference elements 21 to 24, respectively.

  As described above, when the magnetoresistive effect element has shape magnetic anisotropy and the shape has a longitudinal direction, or the direction of the easy axis of magnetization of the magnetoresistive effect element is the longitudinal direction of the shape In some cases, the magnetization direction in the free layer when no magnetic field is applied is the longitudinal direction of the element. In the present embodiment, the magnetization direction in the absence of a magnetic field in each of the free layers of the detection elements 11 to 14 and the reference elements 21 to 24 is the longitudinal direction of the elements, and as shown in FIG. Aligned. As a result, the magnetization directions of the free layers of the detection elements 11 to 14 and the reference elements 21 to 24 in the absence of a magnetic field are all the same. The direction is 90 degrees different from the magnetization direction of the fixed layers of the detection elements 11 to 14 and the reference elements 21 to 24.

  The detection element 11 and the reference element 21 corresponding to the first channel are provided with the same magnetic field generation wiring 112, and the magnetic field generation wiring 112 is connected to the detection element 11 and the reference element 21 with respect to each other. It is configured to apply different magnetic fields. Specifically, the direction of the magnetic field applied to the detection element 11 by the magnetic field generation wiring 112 is 90 degrees different from the magnetization direction of the free layer of the detection element 11 in the absence of a magnetic field, and the magnetic field generation wiring 112 is used for detection. The direction of the magnetic field applied to the element 11 is the same as the magnetization direction of the free layer of the reference element 21 when there is no magnetic field.

  Similarly, magnetic fields different from each other by 90 degrees are applied to the detection element 12 and the reference element 22 corresponding to the second channel from the magnetic field generation wiring 122. Magnetic fields different from each other by 90 degrees are applied to the detection element 13 and the reference element 23 corresponding to the third channel from the magnetic field generation wiring 132, and the detection element 14 and the reference element corresponding to the fourth channel are applied. Magnetic fields different from each other by 90 degrees are applied to 24 from the magnetic field generating wiring 142.

  FIG. 12 shows a state where the input signal of the magnetic field generating wiring 132 is activated. In this state, the magnetic field generated by the magnetic field generating wiring 132 rotates the spin direction of the free layer of the detection element 13. In addition, the magnetic field generated by the magnetic field generating wiring 132 is applied to the reference element 23 in a direction along the magnetization direction of the free layer when there is no magnetic field, so that the magnetization direction of the reference element 23 is stabilized. Is done. The output voltage of the reference element 23 to which the magnetic field in the direction along the magnetization direction of the free layer when no magnetic field is applied is equal to the output voltage (that is, the midpoint signal) when there is no magnetic field. Therefore, a stable level shift operation can be performed by using a stable midpoint signal output from the reference element 23 as a reference signal and comparing the reference signal with the output voltage of the reference element 31.

  In this embodiment, two magnetoresistive elements are provided per channel, so that a level shifter of three or more channels requires more magnetoresistive elements than the configurations of the fourth to sixth embodiments. Compared to a conventional level shifter using a bridge circuit using four magnetoresistive elements, the formation area can be halved.

  In FIG. 12, the shapes of the detection elements 11 to 14 and the reference elements 21 to 24 are elliptical, but the shapes may be arbitrary as long as the magnetization direction of the elements can be determined. The dimensions of the reference elements 21 and 31 and the detection elements 11 to 14 are not necessarily the same. If the area ratio is known, the vertical and horizontal dimension ratios of the elements may be different.

  Further, the detection elements 11 to 14 and the reference elements 21 and 31 are not necessarily arranged in a line as shown in FIG. 10, and their arrangement may be arbitrary as long as normal operation is possible. Further, the detection elements 11 to 14 and the reference elements 21 and 31 and the arrangement as viewed from the device cross section may be arbitrary as long as normal operation is possible.

  In each of the above embodiments, the magnetic field applied to the detection element and the reference element is an induction magnetic field generated by applying a current or voltage to the wiring. However, the magnetic field generation source is not limited to this, and is formed on a substrate, for example. A coil or the like may be used. The bias magnetic field may be generated from a thin film magnet or the like.

  In addition, each magnetoresistive element may be replaced with a plurality of magnetoresistive elements having the same function connected in series or in parallel. In this case, an improvement in accuracy can be expected by averaging the signals of a plurality of magnetoresistive elements.

  As the magnetoresistive effect element used in the present invention, a tunnel magnetoresistive effect element is preferable, but other magnetoresistive effect elements including a ferromagnetic layer whose magnetization direction is fixed, such as a giant magnetoresistive effect element, can be used. Further, the magnetoresistive effect element in the structure of the level shifter may be a laminate of them.

  Furthermore, it has been explained that the wiring for applying a magnetic field to the magnetoresistive effect element is disposed in the upper layer or the lower layer of the magnetoresistive effect element via an interlayer insulating film. You may arrange | position in the same layer as it.

  Further, since the level shifter of the present invention uses a magnetoresistive effect element, it can operate stably at a higher temperature than a level shifter using an optical system or capacitive coupling. Further, by combining with a wide band gap semiconductor substrate such as SiC, GaN, oxide semiconductor or diamond, stable operation in a high temperature range exceeding 200 ° C. is possible. Further, even in the case of a conventional Si semiconductor substrate, it can be used in a temperature range exceeding 150 ° C.

  11-14 Detection element, 21-24, 31, 32 Reference element, 5 Magnetic shield, 112, 122, 132, 142 Magnetic field generation wiring, 112a High permeability material, 113 Compensation wiring, 212 Reference element Magnetic field generating wiring, 400 substrate, 401 element isolation insulating film, 410 interlayer insulating film, 414, 418, 423, 431 contact, 420, 430, 440 interlayer insulating film, 421, 424, 425, 426, 441, 450 wiring, 422 Protective film, 501, 502 Transfer gate transistor.

Claims (32)

Input wiring to which an input signal is applied;
A detection element that is a magnetoresistive effect element that outputs a detection signal in which the input wiring takes a value corresponding to a magnetic field generated according to the input signal;
A magnetoresistive effect element having the same structure as the detection element, and a reference element that outputs a reference signal having a constant value;
A magnetic level shifter that generates an output signal based on a difference between the detection signal and the reference signal. The magnetic level shifter according to claim 1, wherein a surface of the input wiring is covered with a magnetic material except for a surface facing the detection element. An interlayer insulating film covering the detection element and the reference element;
3. The magnetism according to claim 1, further comprising: a protective film disposed between the detection element and the reference element and the interlayer insulating film and protecting the detection element and the reference element. Level shifter. The magnetic level shifter according to any one of claims 1 to 3, further comprising a compensation wiring capable of applying a known magnetic field to the detection element in order to compensate the resistance value of the detection element. . The magnetic level shifter according to claim 4, wherein a surface of the compensation wiring is covered with a magnetic material except a surface facing the detection element. Each of the detection element and the reference element is
A fixed layer that is a magnetic layer with a fixed magnetization direction;
A free layer that is a magnetic layer whose magnetization direction is changed by an external magnetic field;
The magnetic level shifter according to claim 1, further comprising a nonmagnetic layer disposed between the fixed layer and the free layer. Having two reference elements,
One reference element has the same magnetization direction of the fixed layer and the magnetization direction of the free layer when there is no magnetic field,
7. The magnetic level shifter according to claim 6, wherein in the other reference element, the magnetization direction of the fixed layer is opposite to the magnetization direction of the free layer when no magnetic field is applied. The detection element and the reference element have shape magnetic anisotropy,
The magnetic level shifter according to claim 7, wherein the detection element and the reference element are arranged so that their longitudinal directions are different by 90 degrees. The magnetic level shifter according to claim 7, wherein the detection element and the reference element differ in the direction of the easy axis of magnetization by 90 degrees. The magnetic level shifter according to claim 7, wherein a magnetic shield that blocks an external magnetic field is provided around the reference element. The magnetic level shifter according to any one of claims 7 to 10, wherein the input wiring and the detection element are provided for each channel to be multi-channeled. The magnetic level shifter according to any one of claims 1 to 5, further comprising a magnetic field generating wiring for applying a constant magnetic field to the reference element. Each of the detection element and the reference element is
A fixed layer that is a magnetic layer with a fixed magnetization direction;
A free layer that is a magnetic layer whose magnetization direction is changed by an external magnetic field;
The magnetic level shifter according to claim 12, further comprising a nonmagnetic layer disposed between the fixed layer and the free layer. Having two reference elements,
The two reference elements have the same magnetization direction of the fixed layer, and the magnetization directions of the free layer when no magnetic field is also the same direction,
The magnetic level shifter according to claim 13, wherein the magnetic field generating wiring applies magnetic fields in opposite directions to the two reference elements. 15. The magnetic level shifter according to claim 14, wherein the magnetic field generating wiring is a single wiring that is folded back so as to apply magnetic fields in opposite directions to the two reference elements. The detection element and the reference element have shape magnetic anisotropy,
16. The magnetic level shifter according to claim 14, wherein the detection element and the reference element are arranged so that their longitudinal directions are the same. The magnetic level shifter according to claim 14 or 15, wherein the detection element and the reference element have the same easy axis direction. The magnetization direction of the free layer of the detecting element when a magnetic field is applied from the input wiring by the activation of the input signal, and one of the reference elements when the magnetic field is applied from the magnetic field generating wiring The magnetic level shifter according to claim 16 or 17, wherein the magnetization direction of the free layer is the same direction. The detection element and the reference element have shape magnetic anisotropy,
The magnetic level shifter according to claim 14 or 15, wherein the detection element and the reference element are arranged so that their longitudinal directions are different by 90 degrees. The magnetic level shifter according to claim 14 or 15, wherein the detection element and the reference element have directions of easy magnetization different from each other by 90 degrees. 21. The magnetic level shifter according to claim 19, wherein the magnetization directions of the free layers of the two reference elements are opposite to each other when a magnetic field is applied from the magnetic field generating wiring. 21. The magnetic level shifter according to claim 19, wherein, in one of the reference elements in a state where a magnetic field is applied from the magnetic field generating wiring, the magnetization direction of the free layer and the magnetization direction of the fixed layer are opposite to each other. . The magnetic level shifter according to any one of claims 14 to 22, wherein the input wiring and the detection element are provided for each channel to be multi-channeled. 24. The magnetic level shifter according to claim 12, wherein the current flowing through the magnetic field generating wiring and the current flowing through the input wiring are supplied from different power sources. The magnetic level shifter according to any one of claims 12 to 23, wherein the current flowing through the magnetic field generating wiring and the current flowing through the input wiring are respectively supplied from the same power source via a switching element. The magnetic field generated by the input wiring is also given to the reference element,
The magnetic level shifter according to claim 6, wherein the direction of the magnetic field applied to the reference element by the input wiring is the same as the magnetization direction of the free layer of the reference element when there is no magnetic field. The detection element and the reference element have the same magnetization direction of the fixed layer, and the magnetization direction of the free layer when no magnetic field is the same direction,
27. The magnetic level shifter according to claim 26, wherein the direction of the magnetic field applied to the detection element by the input wiring differs from the direction of the magnetic field applied to the reference element by the input wiring by 90 degrees. The detection element and the reference element have shape magnetic anisotropy,
28. The magnetic level shifter according to claim 27, wherein the detection element and the reference element are arranged so that their longitudinal directions are the same. 28. The magnetic level shifter according to claim 27, wherein the detection element and the reference element have the same easy axis direction. 21. The magnetic level shifter according to claim 19, wherein, in the reference element when a magnetic field from the input wiring is applied, an angle between the magnetization direction of the free layer and the magnetization direction of the fixed layer is 90 degrees. The magnetic level shifter according to any one of claims 26 to 30, wherein the input wiring, the detection element, and the reference element are provided for each channel to be multi-channeled. The magnetic level shifter according to any one of claims 1 to 31, wherein the magnetic level shifter is formed using a wide band gap semiconductor substrate.

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