JP2004221463A - Magnetic memory - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic memory wherein an MRAM element is shielded magnetically more than enough from a large external magnetic field too, and the operation of the MRAM element can be ensured without any trouble for the magnetic field effected from the applied environment thereof, and further, its contributions to miniaturizing and lightening are made possible too. <P>SOLUTION: This magnetic storage comprises a TMR element 60 wherein magnetization fastening layers 54, 56 having fastened magnetizing directions and a magnetic layer (storage layer) 2 having a variable magnetizing direction are laminated, and it is constituted as a magnetic random access memory (MRAM) 30 wherein this memory element 60 is shielded magnetically by a magnetic shield layer. Further, the magnetic shield layer 48 so comprises a lamination structure including at least two soft-magnetic body layers that this lamination structure includes a high-permeability material layer 41 and a highly saturated magnetization material layer 33. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides an MRAM (Magnetic Random Access), which is a magnetic random access memory composed of a memory element in which a magnetization fixed layer whose magnetization direction is fixed and a magnetic layer whose magnetization direction can be changed are stacked. (Memory) or a magnetic memory device including a memory element having a magnetizable magnetic layer.
[0002]
[Prior art]
With the rapid spread of information and communication devices, especially small personal devices such as mobile terminals, devices such as memories and logics have higher performance such as higher integration, higher speed and lower power consumption. Is required.
[0003]
In particular, nonvolatile memories are considered to be indispensable in the ubiquitous era. The nonvolatile memory can protect important information including personal information even when power consumption or trouble occurs, or when the server and the network are disconnected due to some kind of failure.
[0004]
Also, recent portable devices are designed to minimize power consumption by placing unnecessary circuit blocks in standby mode. However, if a non-volatile memory that can serve as both high-speed work memory and large-capacity storage memory can be realized, In addition, power consumption and waste of memory can be eliminated.
[0005]
Also, if a high-speed, large-capacity nonvolatile memory can be realized, an “instant-on” function that can be started immediately when the power is turned on will be possible.
[0006]
Examples of the non-volatile memory include a flash memory using a semiconductor and an FRAM (Ferroelectric Random Access Memory) using a ferroelectric.
[0007]
However, the flash memory has a drawback that the writing speed is as slow as the order of microsecond. On the other hand, in the FRAM, the number of rewritable times is 10 ¹² -10 ¹⁴ However, it has been pointed out that the endurance is small and it is difficult to finely process the ferroelectric capacitor in order to completely replace the SRAM (Static Random Access Memory) or the DRAM (Dynamic Random Access Memory) with a static random access memory.
[0008]
Therefore, high-speed, large-capacity (high-integration), low-power-consumption non-volatile memories that do not have these drawbacks have been noted, for example, in Wang et al. , IEEE Trans. Magn. 33 (1997), 4498, which is a magnetic memory called an MRAM (Magnetic Random Access Memory), which has attracted attention due to recent improvements in the characteristics of TMR (Tunnel Magnetoresistance) materials. ing.
[0009]
In particular, the MRAM is a semiconductor magnetic memory using a magnetoresistance effect based on a spin-dependent conduction phenomenon peculiar to a nanomagnetic material, and is a non-volatile memory capable of holding data without supplying power from the outside.
[0010]
In addition, the MRAM has a simple structure, so that high integration is easy. In addition, since recording is performed by rotating a magnetic moment, the number of rewritable times is large, and the access time is very high. It is expected that R.O. Schuerlein et al, ISSCC Digest of Technical Papers, pp. 128-129, Feb. 2000 reported.
[0011]
The MRAM will be described in more detail. As illustrated in FIG. 21, a TMR element 60 serving as a storage element of a memory cell of the MRAM is provided on a support substrate 59 and has a magnetization layer that rotates relatively easily. 52 and fixed magnetization layers 54 and 56.
[0012]
The fixed magnetization layer has two fixed magnetization layers, a first fixed magnetization layer 54 and a second fixed magnetization layer 56, between which the fixed magnetic layers are antiferromagnetically coupled. A conductor coupling layer 55 is provided. For the storage layer 52 and the magnetization fixed layers 54 and 56, a ferromagnetic material made of nickel, iron, cobalt, or an alloy thereof is used as a material.
[0013]
Further, as a material of the conductor coupling layer 55, ruthenium, copper, chromium, gold, silver, or the like can be used. The second magnetization fixed layer 56 is in contact with the antiferromagnetic material layer 57, and the second magnetization fixed layer 56 has strong unidirectional magnetic anisotropy due to exchange interaction acting between these layers. . As a material of the antiferromagnetic layer 57, a manganese alloy such as iron, nickel, platinum, iridium, and rhodium, cobalt, and nickel oxide can be used.
[0014]
The tunnel barrier layer 3 made of an insulator made of an oxide or a nitride of aluminum, magnesium, silicon, or the like is sandwiched between the storage layer 52, which is a magnetic layer, and the first magnetization fixed layer 54. In addition, it plays a role of cutting magnetic coupling between the storage layer 52 and the first magnetization fixed layer 54 and flowing a tunnel current. These magnetic layers and conductor layers are mainly formed by a sputtering method. The tunnel barrier layer 53 can be obtained by oxidizing or nitriding a metal film formed by sputtering.
[0015]
The top coat layer 51 has a role of preventing interdiffusion between the TMR element 60 and a wiring connected to the TMR element 60, reducing contact resistance, and preventing oxidation of the storage layer 52, and is usually made of Cu, Ta, TiN, or the like. Material can be used. The base electrode layer 58 is used for connection with a switching element connected in series with the TMR element 60. The base electrode layer 58 may also serve as the antiferromagnetic layer 57.
[0016]
In the memory cell configured as described above, information is read out by detecting a change in tunnel current due to the magnetoresistance effect, as described later. The effect depends on the relative magnetization direction between the storage layer and the magnetization fixed layer.
[0017]
FIG. 22 is an enlarged perspective view showing a part of a general MRAM in a simplified manner. Here, a read circuit portion and the like are omitted for simplicity, but include, for example, nine TMR elements (memory cells) 60, and have a bit line 61 and a write word line 62 that cross each other. At these intersections, a TMR element 60 is arranged, and when writing to this TMR element 60, a current flows through the bit line 61 and the write word line 62, and a bit line is generated by a combined magnetic field generated from these. Writing is performed with the magnetization direction of the storage layer 52 of the TMR element 60 at the intersection of the write word line 61 and the write word line 62 being parallel or anti-parallel to the magnetization fixed layer.
[0018]
FIG. 23 schematically shows a cross section of the memory cell, for example, a gate insulating film 65, a gate electrode 66, and a source region 67 formed in a p-type well region 64 formed in a p-type silicon semiconductor substrate 63. An n-type read field effect transistor (selection transistor) 69 comprising a drain region 68 and a write word line 62, a TMR element 60, and a bit line 61 are disposed thereon.
[0019]
A sense line 71 is connected to the source region 67 via a source electrode 70. The field effect transistor 69 functions as a switching element for reading, and a read wiring 72 drawn out between the word line 62 and the TMR element 60 is connected to a drain region 68 via a drain electrode 73. Note that the transistor 69 may be an n-type or p-type field-effect transistor, but various switching elements such as a diode, a bipolar transistor, and a MESFET (Metal Semiconductor Field Effect Transistor) can be used.
[0020]
FIG. 24 shows an equivalent circuit diagram of the MRAM, which includes, for example, six memory cells, and has a bit line 61 and a write word line 62 that intersect each other. Along with 60, a field effect transistor 69 and a sense line 71 connected to the storage element 60 and performing element selection at the time of reading are provided. The sense line 71 is connected to the sense amplifier 73 and detects stored information. In the figure, 74 is a bidirectional write word line current drive circuit, and 75 is a bit line current drive circuit.
[0021]
FIG. 25 is an asteroid curve showing the write condition of the MRAM, showing the applied magnetic field H in the easy axis direction. _EA And the hard magnetic field H _HA Of the magnetization direction of the storage layer is shown in FIG. When a corresponding resultant magnetic field vector is generated outside this asteroid curve, a magnetic field reversal occurs, but the resultant magnetic field vector inside the asteroid curve does not reverse the cell from one of its current bistable states. Further, even in cells other than the intersection of the word line and the bit line through which a current flows, a magnetic field generated by the word line or the bit line alone is applied, and thus the magnitude of the magnetic field generated by the unidirectional switching magnetic field H _K In the above case, since the magnetization directions of the cells other than the intersections are also reversed, the selected cells can be selectively written only when the combined magnetic field is in the gray area in the figure.
[0022]
As described above, in the MRAM, by using the two write lines of the bit line and the word line, only the designated memory cell is selectively written by reversing the magnetic spin using the asteroid magnetization reversal characteristic. That is common. The resultant magnetization in a single storage area is determined by the magnetic field H _EA And the magnetic field in the hard axis direction H _HA Is determined by the vector composition with The write current flowing through the bit line applies a magnetic field H in the easy axis direction to the cell. _EA And a current flowing through the word line is applied to the cell by a magnetic field H in the hard axis direction. _HA Is applied.
[0023]
FIG. 26 illustrates the read operation of the MRAM. Here, the layer configuration of the TMR element 60 is schematically illustrated, the above-described magnetization fixed layer is illustrated as a single layer 76, and illustrations other than the storage layer 52 and the tunnel barrier layer 53 are omitted.
[0024]
That is, as described above, the information is written by reversing the magnetic spin of the cell by the synthetic magnetic field at the intersection of the bit line 61 and the word line 62 wired in a matrix, and changing the direction to “1” or “0”. Record as information. Reading is performed using the TMR effect that applies the magnetoresistance effect. The TMR effect is a phenomenon in which the resistance value changes depending on the direction of the magnetic spin. The information "1" and "0" are detected based on the low resistance state in which the magnetic spins are parallel. In this reading, a reading current (tunnel current) flows between the word line 62 and the bit line 61, and an output corresponding to the level of the resistance is read out to the sense line 71 via the reading field effect transistor 69 described above. By doing.
[0025]
As described above, the MRAM is expected to be a high-speed and nonvolatile large-capacity memory. However, since a magnetic material is used for holding data, information is erased or rewritten due to an external magnetic field. Problem. The switching field in the easy axis direction and the switching field H in the hard axis direction described in FIG. _SW Is 20 to 200 Oe (Oe), depending on the material, and is converted into a current of several mA (RH Koch et al., Phys. Rev. Lett. 84, 5419 (2000), JZ. Sun et al., 2001 8 ^th This is because it is as small as Joint Magnetics and Magnetic Material. In addition, since the coercive force (Hc) at the time of writing is, for example, about several Oe to 10 Oe, it is impossible to selectively write into a predetermined memory cell if an internal leakage magnetic field due to an external magnetic field exceeding that value acts. It may be.
[0026]
Therefore, as a step toward practical use of the MRAM, there is a long-awaited need for measures against external magnetism, that is, establishment of a magnetic shield structure for shielding the element from external electromagnetic waves.
[0027]
The environment in which the MRAM is mounted and used is mainly on a high-density mounting substrate and inside an electronic device. Depending on the type of electronic equipment, due to the recent development of high-density mounting, semiconductor elements, communication elements, micro motors, etc. are densely mounted on high-density mounting boards. , An antenna element, various mechanical components, a power supply, and the like are mounted at a high density to constitute one device.
[0028]
The fact that the mixed mounting is possible is one of the features of the MRAM as a nonvolatile memory. However, in an environment where a magnetic field component in a wide frequency range from DC to a low frequency to a high frequency is mixed around the MRAM. Therefore, in order to ensure the reliability of recording and holding of the MRAM, it is required to improve the resistance to an external magnetic field by devising a mounting method of the MRAM itself and a shield structure.
[0029]
As the magnitude of such an external magnetic field, for example, it is specified that a magnetic card such as a credit card or a bank cash card has resistance to a magnetic field of 500 to 600 Oe. For this reason, in the field of magnetic cards, Co-coated γ-Fe ₂ O ₃ And a magnetic material having a large coercive force such as Ba ferrite. Also, in the field of prepaid cards, it is necessary to have resistance to a magnetic field such as 350 to 600 Oe. Since the MRAM element is a device that is mounted in an electronic device housing and is also assumed to be carried, it is necessary to have resistance to a strong external magnetic field equivalent to that of magnetic cards. The magnitude of the magnetic field needs to be suppressed to 30 Oe or less, preferably 20 Oe or less.
[0030]
As a magnetic shield structure of an MRAM, it has been proposed to use an insulating ferrite (MnZn and NiZn ferrite) layer for a passivation film of an MRAM element to provide magnetic shield characteristics (see Patent Document 1 described later). A proposal has been made to attach a high-permeability magnetic material such as permalloy from above and below the package to provide a magnetic shielding effect and prevent magnetic flux from entering an internal element (see Patent Document 2 described later). Further, there is disclosed a structure in which a shield lid is placed on an element with a magnetic material such as soft iron (see Patent Document 3 described later).
[0031]
[Patent Document 1]
U.S. Pat. No. 5,902,690 and drawings (column 5, FIG. 1 and FIG. 3)
[Patent Document 2]
U.S. Pat. No. 5,939,772 and drawings (column 2, FIGS. 1 and 2).
[Patent Document 3]
JP 2001-250206 A (page 5, right column, FIG. 6)
[0032]
[Problems to be solved by the invention]
In order to prevent the external magnetic flux from entering the memory cell of the MRAM, it is most important to provide a magnetic path having a high magnetic permeability around the element to prevent the magnetic flux from entering inside.
[0033]
However, when the passivation film of the element is formed of ferrite as in Patent Document 1 (US Pat. No. 5,902,690), the saturation magnetization of ferrite itself is low (0.2 to 0.5 in a general ferrite material). Tesla (T)), it is impossible to completely prevent the invasion of an external magnetic field. The saturation magnetization of the ferrite itself is about 0.2 to 0.35 T for NiZn ferrite and about 0.35 to 0.47 T for MnZn ferrite. However, since the magnitude of the external magnetic field penetrating the MRAM element is as large as several hundred Oe, At a degree of saturation magnetization, the magnetic permeability of the ferrite becomes almost 1 due to the magnetic saturation of the ferrite, and the ferrite does not function.
[0034]
Although there is no description of the film thickness in Patent Document 1, the effect is hardly expected because the passivation film is usually at most about 0.1 μm, which is too thin for a magnetic shield layer. Moreover, when ferrite is used for the passivation film, since the ferrite is an oxide magnetic material, oxygen deficiency is likely to occur when the film is formed by the sputtering method, and it is difficult to use complete ferrite as the passivation film.
[0035]
Patent Document 2 (U.S. Pat. No. 5,939,772) describes a structure in which the upper and lower portions of a package are covered with a permalloy layer. By using permalloy, a higher shielding performance than a ferrite passivation film can be obtained. However, although the permeability of Mu Metal disclosed in Patent Document 2 is as high as about μi = 100,000, the saturation magnetization is as low as 0.7 to 0.8 T, and is easily affected by an external magnetic field. Since the saturation occurs and μ = 1, there is a disadvantage that the thickness of the shield layer must be considerably large in order to obtain a complete magnetic shielding effect.
[0036]
Therefore, in practice, the structure for preventing the penetration of a magnetic field of several hundred Oe is incomplete as a magnetic shield layer because the saturation magnetization of permalloy is too small and its thickness is too thin.
[0037]
Patent Document 3 (Japanese Patent Application Laid-Open No. 2001-250206) discloses a magnetic shield structure using soft iron or the like. However, since this only covers the upper part of the element, the magnetic shield becomes incomplete and Soft iron has a saturation magnetization of 1.7 T and a magnetic permeability of about 300 μi, which is insufficient magnetic properties. Therefore, even if the magnetic shield is performed by the structure described in Patent Document 3, it is extremely difficult to completely prevent the invasion of the external magnetic field.
[0038]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has as its object to magnetically shield an MRAM element or the like more than sufficiently even with a large external magnetic field, and to apply the MRAM element or the like. An object of the present invention is to make it possible to guarantee operation that does not cause a problem with respect to a magnetic field from the environment, and to contribute to miniaturization and weight reduction.
[0039]
[Means for Solving the Problems]
That is, the present invention is configured as a magnetic random access memory including a memory element in which a magnetization fixed layer having a fixed magnetization direction and a magnetic layer capable of changing the magnetization direction are stacked, wherein the memory element is a magnetic shield. A magnetic memory device magnetically shielded by a layer, or a magnetic memory device in which a memory element having a magnetizable magnetic layer is magnetically shielded by a magnetic shield layer, wherein the magnetic shield layer has at least two soft magnetic materials. The present invention relates to a magnetic memory device comprising a laminated structure including layers, wherein the laminated structure includes a high magnetic permeability material layer and a high saturation magnetization material layer.
[0040]
In the process of devising the present invention, the present inventor has shown in FIG. 27 a magnetic shield structure for shielding a high-sensitivity magnetometer, MRI (Magnetic Resonance Image), etc. from a large external magnetic field of about several hundred Oe. We noticed that such a shield structure is known. This is a structure in which the working space 80 is first covered with a high magnetic permeability material layer 78, and the outside thereof is further covered with a high saturation magnetization material layer 77 (for example, Keizo Ota, "Points for Selecting Magnetic Materials", published by the Japan Standards Association). See).
[0041]
With a normal shield structure, when a large magnetic field of several hundred Oe is applied from the outside, a magnetic material having a small saturation magnetization is used. Therefore, the magnetic material is easily magnetically saturated and a large magnetic field is generated inside. Invade. However, in the structure of FIG. 27, first, a high saturation magnetization material layer 77, which is a magnetic material having a large saturation magnetization, is arranged to absorb and weaken an external magnetic field. With the high permeability material layer 78 having a high magnetic permeability, the internal magnetic field strength can be reduced and the magnetic shielding effect can be enhanced.
[0042]
The present invention effectively applies such a magnetic shield structure to an MRAM or the like that requires an extremely low internal magnetic field strength. That is, in the MRAM, since the magnetic shield layer is formed by the laminated structure including at least two soft magnetic layers, the external magnetic field is weakened by being absorbed by the high saturation magnetization material layer and weakened. Since the external magnetic field can be further reduced by transmitting the external magnetic field to the outside by the high magnetic permeability material layer, the internal magnetic field strength of the magnetic memory device can be particularly reduced to 30 Oe or less, which is suitable for MRAM. A magnetic shielding effect can be obtained. Therefore, by applying such a magnetic shield layer to an MRAM element, an extremely useful and high-performance magnetic shield effect can be obtained for an MRAM which is particularly susceptible to an externally applied magnetic field (in particular, a coercive force at the time of writing is 10 Oe or less). Can be realized.
[0043]
BEST MODE FOR CARRYING OUT THE INVENTION
In the magnetic memory device of the present invention, in order to exhibit a magnetic shielding effect, it is preferable that the high magnetic permeability material layer and the high saturation magnetization material layer are arranged in order from the memory element side, This order can be reversed.
[0044]
Further, the laminated structure including the high magnetic permeability material layer and the high saturation magnetization material layer effectively exerts its magnetic shielding effect, and considering the mounting on a mounting substrate, seals the memory element. Preferably, it is arranged on the upper and / or lower part of the package, and / or on the upper and / or lower part of the memory element in the package.
[0045]
In order to effectively exhibit the magnetic shielding effect, it is preferable that the thickness ratio between the high saturation magnetization material layer and the high magnetic permeability material layer is 4: 1 to 3: 7.
[0046]
In addition, it is desirable to have a magnetic shielding effect against a DC external magnetic field and / or an AC external magnetic field.
[0047]
The high permeability material layer is composed of 75 to 78% by weight of Ni, 2 to 3% by weight of Cr, 4 to 6% by weight of Cu, and the balance of Fe; 75 to 80% by weight of Ni, 3 to 5% by weight of Mo, 1 to 6% by weight of Cu, Balance: 79 to 82% by weight of Ni, 3.5 to 6% by weight of Mo, the balance of Fe; and 75 to 78% by weight of Ni, 3 to 4.5% by weight of Mo, 4 to 6% by weight of Cu, and the balance of Fe. Desirably, it is formed of at least one kind of soft magnetic material.
[0048]
Further, the high saturation magnetization material layer is composed of 2 to 3% by weight of Si, the balance of Fe: 47 to 50% by weight of Co, the balance of Fe: 35 to 40% by weight of Co, the balance of Fe: 23 to 27% by weight of Co, the balance of Fe; % By weight, V1 to 3% by weight, and the balance of Fe; desirably formed of at least one soft magnetic material selected from the group consisting of:
[0049]
Further, in addition to the high-saturation magnetic material layer having a flat film shape or plate shape, in order to more effectively suppress the magnetic saturation, a film or plate shape with irregularities, or a mesh or slit It is desirable to have a shape with through holes such as.
[0050]
Further, the present invention is suitable for an MRAM. In such an MRAM, an insulator layer or a conductor layer is sandwiched between the magnetization fixed layer and the magnetic layer, and provided on the upper and lower surfaces of the memory element. Information is written by magnetizing the magnetic layer in a predetermined direction with a magnetic field induced by flowing a current through each of the wirings serving as the bit line and the word line, and the written information is written in the tunnel magnetoresistance effect between the wirings ( It may be configured to read out by the TMR effect).
[0051]
Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.
[0052]
1 to 3 exemplify MRAM packages having various magnetic shield structures according to the present embodiment.
[0053]
In these examples, the MRAM elements (chips including the memory cell section and the peripheral circuit section) 30 shown in FIGS. 21 to 23 are provided on the die pad 40 and external leads connected to a mounting board (not shown). Except for the MRAM 31, it is sealed with a sealing material 32 such as a mold resin (for example, epoxy resin). (Here, the MRAM element 30 has the same structure and operation principle as the MRAM described above. (Abbreviated and the lead frame including the die pad 40 is simply illustrated).
[0054]
FIG. 1A shows an example in which a magnetic shield layer 48 in which a high magnetic permeability material layer 41 and a high saturation magnetization material layer 33 are sequentially laminated is disposed on the upper surface and the lower surface of the sealing material 32, respectively, and FIG. FIG. 1C shows an example in which the stacking order of the high magnetic permeability material layer 41 and the high saturation magnetization material layer 33 is exchanged, and FIG. 1C shows the middle between the high magnetic permeability material layer 41 and the high saturation magnetization material layer 33. An example in which the magnetic permeability material layer 27 and the medium saturation magnetization material layer 26 are formed into a magnetic shield layer 48 composed of four layers will be described.
[0055]
FIG. 2 shows an example in which a laminate of a high magnetic permeability material layer 41 and a high saturation magnetization material layer 33 is embedded in an upper portion of an MRAM element 30 and a lower portion of a die pad 40 in a sealing material 32 in a non-contact manner. 3 shows an example in which a laminated body of a high magnetic permeability material layer 41 and a high saturation magnetization material layer 33 is embedded in the sealing material 32 in contact with the upper part of the MRAM element 30 and the lower part of the die pad 40, respectively.
[0056]
Here, in order to fix the magnetic shield layer 48 including the high magnetic permeability material layer 41 and the high saturation magnetization material layer 33, for example, the magnetic shield layer 48 is bonded to the upper surface and the lower surface of the sealing material 32 after sealing with the sealing material 32. Alternatively, at the time of sealing, it may be arranged in a mold above the MRAM element 30 and below the die pad 40 or bonded in advance.
[0057]
In any case, the MRAM element 30 has a sandwich structure arranged between the magnetic shield layers, and the magnetic shield layer is integrated with the MRAM package. This takes into consideration the mounting on the mounting board (circuit board). This is the most desirable structure, and any of the magnetic shield structures shown in FIGS. 1 to 3 has an effect of magnetically shielding the MRAM element 30 more than an externally applied magnetic field.
[0058]
In any of the above examples, the magnetic shield layer does not form a closed magnetic circuit between itself and the outside, but even in this state, the magnetic field can be effectively shielded by effectively collecting the externally applied magnetic field. . The magnetic shield layer is preferably provided above and below the MRAM element 30, respectively. However, even if it exists on at least one (particularly, on the surface side of the MRAM element 30), the magnetic shield effect can be exhibited.
[0059]
Further, the magnetic shield layer 48 shown in FIGS. 1 to 3 is made of a flat film, foil, or flat plate, but is not limited thereto. As shown in FIG. 4B, or a shape in which a through hole 36 such as a mesh or a slit is provided in the high saturation magnetization material layer 33 as shown in FIG. 4B.
[0060]
As described above, in the magnetic shield layer having the highly-saturated magnetic material layer 33 having the shape shown in FIGS. 4A and 4B, the shape anisotropy not only at the peripheral end but also at the irregularities 35 and the through holes 36. Due to the nature, a demagnetizing field with respect to an externally applied magnetic field is generated, magnetic saturation is unlikely to occur, and a high-performance shielding effect is obtained.
[0061]
Each of the magnetic shield structures shown in FIGS. 1 to 4 has a magnetic shield layer 48 composed of a high magnetic permeability material layer 41 and a high saturation magnetization material layer 33. Of these layers, the high saturation magnetization The external magnetic field is absorbed and weakened by the material layer 33 (further, the medium-saturated magnetic material layer 26), and the weakened external magnetic field is further outwardly transmitted by the high-permeability material layer 41 (further, the medium-permeability material layer 27). Since the light can be transmitted, the intensity of the internal magnetic field acting on the MRAM element 30 can be sufficiently reduced, and the magnetic shield effect can be sufficiently exhibited.
[0062]
In addition, since the magnetic shield layer 48 can be easily and accurately arranged in the sealing material 32 or at a predetermined position on the sealing material 32, even if an externally applied magnetic field of 300 Oe to 500 Oe acts, for example, the MRAM The internal magnetic field with respect to the element 30 is always suppressed to 30 Oe or less, and the normal operation condition can be sufficiently satisfied.
[0063]
Further, it is possible to supply a product whose operation can be guaranteed without any problem with respect to a magnetic field from an environment to which the MRAM element is applied. Further, since the product can be made thin, the structure is suitable for high-density mounting. Further, a magnetic shielding effect can be provided not only for a DC magnetic field but also for an AC magnetic field.
[0064]
Next, in order to guarantee the normal operation of the above-mentioned MRAM element 30, the present inventor, for example, even if a large external magnetic field of 100 Oe or more is applied to the inside of the MRAM element 30, the internal magnetic field of the MRAM element 30 is reduced. An experiment was conducted for the purpose of achieving a performance of 30 Oe or less, and was studied.
[0065]
FIG. 5 shows a schematic diagram during the experiment. For example, two magnetic shield layers 28 of 10 mm × 10 mm are arranged at an interval of 0.4 mm, and a Gauss meter 37 is arranged at the center (cavity). By applying a DC magnetic field of 300 Oe and 500 Oe in parallel with the magnetic shield layer and moving the Gauss meter 37 in parallel with the magnetic shield layer, the internal magnetic field strength from the end to the center (leakage magnetic field from the magnetic shield layer) Strength) was measured, and an effective magnetic shield material was examined.
[0066]
In this experiment, first, a magnetic shield layer 28 composed of a single layer of only the high magnetic permeability material layer 41 was formed using permalloy, which is an Fe—Ni alloy known as a high magnetic permeability alloy.
[0067]
In practice, the MRAM element 30 is used by being assembled into a multi-pin type QFP package (Quad Flat Package) or the like. The package has a thickness of about 3.45 mm for the 160-pin QFP type and about 3.6 mm for the 208-pin QFP type, and the package has a length of 28 mm and a distance between the package lower surface and the substrate of about 30 mm. It is 300 μm. Therefore, in practice, the thickness of the magnetic shield layer is about 300 μm at the maximum, but it is preferable to suppress the thickness to 150 μm or less in consideration of easy handling in the mounting process.
[0068]
From the constraints of such actual conditions, various studies have been made on a magnetic shield structure that is the thinnest and the magnetic shield is effective.
[0069]
For example, as shown in FIG. 6A and FIG. 6B, the front surface when mounting 79% by weight of Ni as the high magnetic permeability material layer 41 and a permalloy foil (thickness of 200 μm) of the remaining Fe on the upper and lower parts of the package. The figure is shown. Here, in FIG. 6A, the high magnetic permeability material layer 41 is omitted, but the external leads 31 on the front side are shown, and in FIG. 6B, the high magnetic permeability material layer is shown. Although 41 is shown, the external lead 31 on the front side is omitted.
[0070]
FIG. 7 is a graph showing the characteristics of the internal magnetic field strength (Oe) and the measurement distance (shield length mm). The graph shows the Fe—Ni-based high permeability material layer 41 as the magnetic shield layer. 5 shows a magnetic field intensity distribution inside the MRAM package when an externally applied magnetic field is set to 500 Oe using an MRAM package using only (high μ material).
[0071]
When a strong magnetic field of 500 Oe is applied from the outside, the high magnetic permeability material layer 41 made of permalloy foil (thickness: 200 μm) with 79% by weight of Ni and the balance of Fe absorbs the external magnetic field to reach magnetic saturation. It was found that the internal magnetic field strength became 400 Oe or more at the center of the MRAM package, and the internal magnetic shielding effect almost disappeared.
[0072]
Therefore, for example, even if a structure in which a Mu Metal layer is disposed as a material of the high magnetic permeability material layer 41 as shown in Patent Document 2 (US Pat. No. 5,939,772), a magnetic shielding effect is practically used. It was difficult to expect.
[0073]
On the other hand, FIG. 8 shows that the MRAM package is magnetically shielded only with a high saturation magnetization material (high Ms material: Co49%, V2%, Fe balance) 33 which is a material having high saturation magnetization to prevent magnetic saturation. The distribution of the magnetic field inside the package in the case of the above is shown. Here, the intensity of the externally applied magnetic field was 300 Oe, 500 Oe, and 700 Oe.
[0074]
Since the high saturation magnetization material layer 33 is made of a permendur alloy (200 μm in thickness) of Co 49%, V 2%, and the balance of Fe, the magnetic saturation state can be slightly prevented, but 300 Oe inside the MRAM element 30. Even at the time of application, the magnetic field intensity is 47 Oe, becomes magnetically saturated when an external magnetic field of 500 Oe is applied, becomes 282 Oe, and becomes 488 Oe when 700 Oe is applied. It is applied inside.
[0075]
Therefore, in order to obtain a more effective shield structure, as shown in FIGS. 9A and 9B, a magnetic shield layer having a two-layer structure was manufactured based on the present invention. In FIG. 9A, the high saturation magnetization material layer 33 and the high magnetic permeability material layer 41 are omitted, but the external leads 31 on the front side are shown. In FIG. 9B, the high saturation magnetization material layer is shown. Although the layer 33 and the high magnetic permeability material layer 41 are shown, the external leads 31 on the front side are omitted.
[0076]
For the outermost layer, a 49% Co, V2%, Fe-permendur alloy (saturation magnetization Ms = 2.3T) is used as the high saturation magnetization material layer 33, and the high magnetic permeability material layer 41 is Ni 75% inside. , Mo 5%, Cu 1%, and the balance of Fe were used as a supermalloy alloy (initial magnetic permeability μi = 100,000).
[0077]
Here, the actual manufacturing process is as follows. First, in order to form a magnetic shield layer 48 composed of the high magnetic permeability material layer 41 and the high saturation magnetization material layer 33, the respective magnetic shield foils adjusted to a predetermined thickness are overlapped with each other by, for example, a pressing step. After being pressed by, for example, or bonded using a thin adhesive film (thickness: about 10 μm), this is cut into a predetermined size.
[0078]
Subsequently, in the case of forming a magnetic shield layer of a QFP 160 pin type package, a mold package was formed in accordance with a normal manufacturing process of the sealing material 32. Then, a magnetic shield layer including the high magnetic permeability material layer 41 and the high saturation magnetization material layer 33 was bonded to the upper and lower surfaces with a thin adhesive film (for example, about 10 μm thick).
[0079]
Here, even if the distance between the upper and lower portions of the magnetic shield layer fluctuates slightly, the magnetic shield effect is hardly affected, so that the influence of the thickness of the adhesive layer on the magnetic shield effect can be neglected.
[0080]
The MRAM package with the magnetic shield layer manufactured in this manner was mounted on a circuit board or the like by a normal mounting device, and then soldered to the circuit board through a reflow process or the like. Since the heating in this reflow step is usually about 260 ° C., it does not deteriorate the magnetic properties of the magnetic shield material.
[0081]
FIG. 10 shows 49% Co, V2% forming the outer layer of the magnetic shield layer, and the permendur alloy layer 33 of the remaining Fe, and Ni75%, Mo5%, Cu1% forming the inner layer, and the supermalloy alloy of the remaining Fe. The internal magnetic field strength inside the MRAM package when the thickness of the layer 41 is 100 μm and the total thickness of the magnetic shield layer is 200 μm is shown. The externally applied magnetic field strength was 300 Oe.
[0082]
As a result, the internal magnetic field intensity is 17.2 Oe, which is lower than the target value of 30 Oe. Compared with the results of FIGS. 7 and 8 in which each magnetic material layer 41 or 33 is a magnetic shield layer alone, It was found that the magnetic shielding effect was greatly improved.
[0083]
In FIG. 11, the inner layer of the magnetic shield layer is formed of 49% of Co, 2% of V, and the permendur alloy layer 33 of the balance of Fe, and the outer layer is formed of 75% of Ni, 5% of Mo, 1% of Cu, and the supermalloy alloy layer 41 of the balance of Fe. The figure shows the internal magnetic field strength inside the MRAM package when the thickness is 100 μm and the total thickness of the magnetic shield layer is 200 μm. The external magnetic field application strength was set to 300 Oe.
[0084]
As a result, the internal magnetic field strength is 19.4 Oe, which is slightly lower than the target value of 30 Oe, although the magnetic shield performance is slightly inferior to the internal magnetic field strength (17.2 Oe) shown in FIG. Also in this example, it was found that the magnetic shielding effect was greatly improved as compared with the results shown in FIGS. 7 and 8 in which each magnetic material layer 41 or 33 was used alone as a magnetic shielding layer.
[0085]
Subsequently, in order to investigate a more effective magnetic shield structure, the outer layer was made of 49% Co, 2% V, a permendur alloy layer 33 of the remaining Fe (saturation magnetization Ms = 2.3T), and the inner layer was made of Ni75. %, Mo 5%, Cu 1%, and the balance of superalloy in the superalloy alloy layer 41 (initial magnetic permeability μi = 100,000), and the total thickness of these is fixed at 200 μm, and the thickness of the two layers is fixed. The experiment was performed while changing only the amount. Table 1 in FIG. 12 shows the internal magnetic field strength at the package center at that time (hereinafter the same).
[0086]
From this result, when the thickness of the inner high-permeability material layer 41 increases, the magnetic shielding effect increases once. However, when most of the magnetic shield layer is replaced with the high-permeability material layer 41, the outer high-permeability material layer 41 has a high saturation. It has been found that since the magnetic material layer 33 is almost eliminated, the saturation magnetization decreases, the internal magnetic field intensity exceeds 30 Oe, and the magnetic shielding effect deteriorates.
[0087]
In this example, since the target is to reduce the internal magnetic field strength to 30 Oe or less, in order to realize this, the thickness ratio between the high saturation magnetization material layer 33 and the high magnetic permeability material layer 41 must be: It was found that the ratio was preferably from 4: 1 (160 μm: 40 μm, 30 Oe) to 3: 7 (60 μm: 140 μm, 30 Oe), and more preferably around 3: 2 (120 μm: 80 μm, 15 Oe).
[0088]
Subsequently, while keeping the thickness ratio between the high saturation magnetization material layer 33 and the high magnetic permeability material layer 41 constant, the internal magnetic field when the total thickness of these two layers is changed and reduced. The strength was measured. The results are shown in Table 2 of FIG.
[0089]
From this result, when the external applied magnetic field is 300 Oe, the magnetic shielding effect tends to be improved as the total thickness increases. For example, the thickness of the high saturation magnetization material layer 33 is set to 100 μm, and the thickness of the high magnetic permeability material layer is increased. Even when the thickness of 41 was 67 μm and the total thickness was 167 μm, the internal magnetic field strength was 19 Oe, indicating that a relatively good magnetic shielding effect could be secured.
[0090]
From the results, a 49% high saturation magnetization Co2%, V2%, Fe-remaining permendur alloy was used on the outside of the magnetic shield layer having the two-layer structure, and Ni75%, Mo5%, Cu1%, and Fe remaining on the inside. It was found that when a supermalloy alloy was used, the magnetic shielding effect could be exhibited even when the thickness was 100 μm and 67 μm, respectively, and the total thickness was 200 μm or less.
[0091]
Subsequently, while maintaining the magnetic shield structure, the effect when the package size was variously changed was measured.
[0092]
With the recent development of high-density packaging, package structures include not only QFPs but also SOPs (Single Outline Packages), LQFPs (Low Profile Quad Flat Packages), BGAs (Ball Grid Array Packages), and LFBGAs (Low Profile Packages). The density and the number of pins have been increased as in the case of LPG (Package) and LFLGA (Low Profile Fine Pitch Land Grid Array Package).
[0093]
Regarding the size of various packages, various package forms, for example, from 10 mm on one side to 40 mm at the maximum, have been put to practical use. These packages are variously applied according to the application form of the MRAM element. At this time, it is necessary to take care that the magnetic shield performance is not deteriorated by the package size.
[0094]
Normally, as shown in FIG. 8, the state of the magnetic field from the end to the center of the package tends to be highest at both ends of the package, and tends to decrease toward the inside. However, when the magnetic shield layer is magnetically saturated, the magnetic field intensity increases again from a certain distance, and reaches a maximum value at the center of the package. Since such a profile exists, it is considered that the internal magnetic field intensity actually varies variously depending on the length of one side of the magnetic shield layer.
[0095]
The experiments and examinations so far have been carried out by assuming a QFP160 pin package, fixing the length of one side of the magnetic shield layer to 28 mm, and fixing the distance between the upper and lower magnetic shield layers to 3.45 mm. As a result, the outermost layer was made of a 49% Co, V2% having a high saturation magnetization property, a permendur alloy layer of the balance of Fe, and a 75% Ni, 5% of Mo, 1% of Cu, and a supermalloy of 100% each of the balance of Fe, respectively. It was found that the structure having a thickness of 67 μm has good shielding performance and can be made thin.
[0096]
Next, Table 3 in FIG. 14 shows the magnetic field intensity distribution at the center of the package when the length of one side is changed from 10 mm to 40 mm while the thickness of each of the magnetic material layers 33 and 41 is maintained.
[0097]
As a result, when the length of one side of the magnetic shield layer is 30 mm or less, the internal magnetic field strength is 30 Oe or less, and almost effective magnetic shield characteristics can be maintained. However, when the length is 40 mm or more, the magnetic field exceeds 100 Oe. It has been found that an external magnetic field penetrates inside due to magnetic saturation at the center of the layer.
[0098]
Therefore, by using the magnetic shield structure of this example, in a normal package, under the condition that the thickness of the high saturation magnetization material layer 33 is 100 μm and the thickness of the high magnetic permeability material layer 41 is 67 μm, one side does not exceed 30 mm. It has been found that the range is applicable to almost all package structures.
[0099]
That is, the present invention can be applied to all conventional packages such as SOP, QFP, LQFP, BGA, LFBGA, and LFLGA without any problem. However, when the condition of the package changes, the condition such as the allowable length of one side also changes, so that it is not necessary to be 30 mm or less in all situations.
[0100]
On the other hand, the thickness of the package has been remarkably reduced in recent years. The thickness of the package is 3.5 mm to 4 mm, and the thickness of the package is 1 mm to 1.5 mm. Therefore, the distance between the magnetic shield layers may also vary from 1 mm to 4 mm.
[0101]
Therefore, in a normal package, under the condition where the thickness of the high saturation magnetization material layer 33 is 100 μm and the high magnetic permeability material layer 41 is 67 mm and the best magnetic shield characteristics are obtained, the length of one side of the magnetic shield layer is small. The relationship between the internal magnetic field strength and the distance between the magnetic shield layers (1 mm to 4 mm) at a constant value of 10 mm was examined. The results are shown in Table 4 of FIG.
[0102]
As a result, even if the distance between the magnetic shield layers is reduced from 4 mm to 1 mm, the magnetic field intensity at the center of the package becomes, for example, 14 Oe to 9 Oe when the externally applied magnetic field intensity is 300 Oe, and becomes 30 Oe. With the following, it became clear that there was not much change.
[0103]
Among them, as shown in FIG. 16, even if the distance between the magnetic shield layers is 4 mm, the internal magnetic field strength is reduced to 14 Oe in the magnetic field strength profile from the package end when the external magnetic field strength is 300 Oe. I was able to.
[0104]
Further, as shown in FIG. 17, if the distance between the magnetic shield layers was 1 mm, the internal magnetic field could be reduced to 9 Oe in the magnetic field intensity profile from the package end when the external magnetic field intensity was 300 Oe. .
[0105]
A comparison between the results of FIG. 16 and the results of FIG. 17 shows that when the distance between the magnetic shield layers is reduced, the internal magnetic field strength is more likely to be further reduced, and the effective length of the portion where the magnetic field is magnetically shielded is slightly longer. It turned out to be an advantage.
[0106]
From the above results, it is effective to structurally configure the magnetic shield with two layers, arrange the high saturation magnetization material layer 33 on the outside, and arrange the high magnetic permeability material layer 33 on the inside. It became clear.
[0107]
Here, in consideration of the practical use of the magnetic shield layer, various characteristics such as cost, ease of processing, presence / absence of heat treatment, and coefficient of thermal expansion are considered to influence the selection of the material. The results of various examinations of the materials used for each layer are as follows. First, the inner layer is made of Ni75%, Mo5%, Cu1%, and the super-alloy alloy of the balance of Fe, and the outer layer is made of pure iron with high saturation magnetization, FeSiB. Alternatively, the characteristics and results of the materials used are shown in Table 5 in FIG.
[0108]
Subsequently, the material of the outer high-saturation magnetization material layer 33 is fixed with Co49%, V2%, and the remainder of Fe with a permendur alloy, and the material of the inner high-permeability material layer 41 is made of permalloy or Co-based amorphous. The properties and results of the materials used are shown in Table 6 in FIG.
[0109]
As a result, according to Table 5 in FIG. 18, when the outer layer is made of pure iron, FeSiB, silicon steel plate, or the like having a high saturation magnetization, the internal magnetic field strength is 30 Oe or less in any of the examples. It can be said that it is appropriate.
[0110]
According to Table 6 in FIG. 19, even with permalloy, the internal magnetic field strength is 30 Oe or less, and sufficient characteristics can be obtained. However, not only the above Co-based amorphous but also Sendust, Finemet (registered trademark), etc. It was found that the magnetic field strength was 30 Oe or less, and the same effect was sufficiently obtained.
[0111]
Next, FIG. 20 shows the characteristics of the permeability (arbitrary unit) and the frequency (Hz) of Permalloy. ⁴ Assuming that the magnetic permeability is good from DC to around several kHz, the adaptive frequency of the magnetic shield structure of this example using permalloy can be applied not only to DC magnetic fields but also to AC magnetic fields.
[0112]
It is effective to dispose the high saturation magnetization material layer 33 on the outside, but the present invention is not limited to this. Having a sufficient magnetic shielding effect can be understood from the results shown in FIG.
[0113]
The embodiments described above can be variously modified based on the technical idea of the present invention.
[0114]
For example, the number of each magnetic material layer constituting the magnetic shield layer may not be limited to two layers, but may be three or more layers (for example, four layers) as shown in FIG. Good.
[0115]
SUMMARY OF THE INVENTION An object of the present invention is to provide an MRAM shield structure for sufficiently reducing an internal invasion magnetic field even when a large magnetic field of several hundred Oe acts on an MRAM element. It has a structure in which a laminate including a layer and a magnetic material layer having high magnetic permeability is arranged. Therefore, the magnetic material to be used is not limited to the above-mentioned materials, and any magnetic material having a different magnetic composition but a similar composition can be used.
[0116]
Further, the composition and type of the high saturation magnetization material and the high magnetic permeability material, the thickness and arrangement of the magnetic shield layer, the structure of the MRAM, and the like may be variously changed. The magnetic shield layer is located not only at the top and bottom of the MRAM device or package, but also at the top and / or bottom of the MRAM device on the outer surface of the package, and / or at the top and / or bottom of the MRAM device in the package. May be.
[0117]
Although the present invention is suitable for an MRAM, it is also applicable to other magnetic memory devices including a memory element having a magnetizable magnetic layer.
[0118]
Effects of the Invention
As described above, according to the present invention, the magnetic shield layer has a laminated structure including at least two soft magnetic layers, and the laminated structure includes the high saturation magnetization material layer and the high magnetic permeability material layer. By these layers, the external magnetic field is effectively weakened and transmitted to the outside, the internal magnetic field intensity of the magnetic memory device can be reduced, and the magnetic shielding effect is sufficiently exhibited. By applying such a magnetic shield layer to an MRAM element, an extremely useful and high-performance magnetic shield is particularly effective for an MRAM which is particularly susceptible to an externally applied magnetic field (in particular, a coercive force at the time of writing is 10 Oe or less). The effect can be realized.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of various MRAM packages according to an embodiment of the present invention.
FIG. 2 is a schematic sectional view of another MRAM package.
FIG. 3 is a schematic sectional view of another MRAM package.
FIG. 4 is a schematic sectional view of still another MRAM package.
FIG. 5 is a schematic cross-sectional view when the internal magnetic field strength between the magnetic shield layers is measured.
6A and 6B are front views (a) and (b) of a specific example of an MRAM package having a single magnetic shield layer.
FIG. 7 is a distribution diagram of an internal magnetic field intensity when an externally applied magnetic field is 500 Oe when a high magnetic permeability material having a thickness of 200 μm is used for a magnetic shield layer (shield foil).
FIG. 8 is a distribution diagram of an internal magnetic field intensity when an externally applied magnetic field is 300 Oe, 500 Oe, and 700 Oe when a high saturation magnetization material having a thickness of 200 μm is used for a magnetic shield layer (shield foil).
FIGS. 9A and 9B are schematic front views (a) and (b) of a specific example of the MRAM package according to the embodiment of the present invention;
FIG. 10 shows a case where a magnetic shield layer (shield foil) made of a high magnetic permeability material and a high saturation magnetic material having a thickness of 100 μm is used. It is arrange | positioned outside and is a distribution diagram of the internal magnetic field intensity in case the external applied magnetic field is 300 Oe.
FIG. 11 shows that when a magnetic shield layer (shield foil) made of a high magnetic permeability material and a high saturation magnetic material having a thickness of 100 μm is used, the high magnetic permeability material is applied outside and the high saturation magnetic material is used. FIG. 9 is a distribution diagram of the internal magnetic field intensity when the externally applied magnetic field is set to 300 Oe and arranged inside.
FIG. 12 shows the relationship between the thickness of the high magnetic permeability material and the high saturation magnetization material and the internal magnetic field strength for each externally applied magnetic field strength when the total thickness of the high magnetic permeability material and the high saturation magnetization material is fixed. It is a table shown in FIG.
FIG. 13 is a table showing the relationship between the total thickness of the high magnetic permeability material and the high saturation magnetization material and the internal magnetic field strength for each externally applied magnetic field strength.
FIG. 14 is a table showing the relationship between the length of the magnetic shield layer and the internal magnetic field strength for each externally applied magnetic field strength when the total thickness of the high magnetic permeability material and the high saturation magnetization material is fixed.
FIG. 15 shows the relationship between the distance between the magnetic shield layers and the internal magnetic field strength when the total thickness of the high magnetic permeability material and the high saturation magnetization material and the length of the magnetic shield layer are fixed. It is a table shown for each.
FIG. 16 is a distribution diagram of an internal magnetic field intensity when an externally applied magnetic field is 300 Oe when a magnetic shield layer (shield foil) in which the distance between the magnetic shield layers is 4 mm is used.
FIG. 17 is a distribution diagram of internal magnetic field strength when an externally applied magnetic field is 300 Oe when a magnetic shield layer (shield foil) having a magnetic shield layer spacing of 1 mm is used.
FIG. 18 is a table showing the relationship between the material of the high saturation magnetization material and the internal magnetic field strength for each externally applied magnetic field strength when the material of the high magnetic permeability material is fixed.
FIG. 19 is a table showing the relationship between the material of the high magnetic permeability material and the internal magnetic field strength for each externally applied magnetic field strength when the material of the high saturation magnetization material is fixed.
FIG. 20 is a graph showing a correlation characteristic between frequency and magnetic permeability.
FIG. 21 is a schematic perspective view of a TMR element of an MRAM according to a conventional example.
FIG. 22 is a schematic perspective view of a part of the memory cell unit of the MRAM.
FIG. 23 is a schematic sectional view of a memory cell of the MRAM.
FIG. 24 is an equivalent circuit diagram of the MRAM.
FIG. 25 is a magnetic field response characteristic diagram of the MRAM at the time of writing.
FIG. 26 is a diagram illustrating the principle of a read operation of the MRAM.
FIG. 27 is a schematic sectional view of a shield structure covered with a high magnetic permeability material and a high saturation magnetization material.
[Explanation of symbols]
28, 48: magnetic shield layer, 30, 60: MRAM element (with built-in TMR element), 31: external lead, 32: sealing material, 33: high saturation magnetization material layer, 35: unevenness,
36: through hole, 37: Gauss meter, 40: die pad,
41: high magnetic permeability material layer, 51: top coat layer, 52: storage layer,
53: tunnel barrier layer, 54: first magnetization fixed layer, 55: antiferromagnetic coupling layer,
56: second magnetization fixed layer, 57: antiferromagnetic layer, 58: underlayer,
59: support substrate, 60: memory cell (TMR element), 61: bit line,
62: write word line, 63: silicon substrate, 64: well region,
65: gate insulating film, 66: gate electrode, 67: source region,
68 ... Drain region,
69 ... read-out field effect transistor (selection transistor),
70 ... source electrode, 71 ... sense line, 72 ... readout wiring,
73: drain electrode, 76: fixed magnetization layer

Claims (10)

It is configured as a magnetic random access memory including a memory element in which a magnetization fixed layer having a fixed magnetization direction and a magnetic layer capable of changing the magnetization direction are stacked, and the memory element is magnetically shielded by a magnetic shield layer. Wherein the magnetic shield layer has a laminated structure including at least two soft magnetic layers, and the laminated structure includes a high magnetic permeability material layer and a high saturation magnetization material layer. Magnetic memory device. In a magnetic memory device in which a memory element having a magnetizable magnetic layer is magnetically shielded by a magnetic shield layer, the magnetic shield layer has a laminated structure including at least two soft magnetic layers. A magnetic memory device comprising a magnetic permeability material layer and a high saturation magnetization material layer. 3. The magnetic memory device according to claim 1, wherein the high magnetic permeability material layer and the high saturation magnetization material layer are arranged in order from the side of the memory element. The stacked structure including the high magnetic permeability material layer and the high saturation magnetization material layer includes an upper part and / or a lower part of a package enclosing the memory element, and / or an upper part of the memory element in the package The magnetic memory device according to claim 1, wherein the magnetic memory device is disposed at a lower portion of the magnetic memory device. 3. The magnetic memory device according to claim 1, wherein a thickness ratio between the high saturation magnetization material layer and the high magnetic permeability material layer is 4: 1 to 3: 7. The magnetic memory device according to claim 5, wherein an internal magnetic field in the magnetic memory device is equal to or less than 30 Oe. 3. The magnetic memory device according to claim 1, wherein the magnetic memory device has a magnetic shielding effect against a DC external magnetic field and / or an AC external magnetic field. The high magnetic permeability material layer,
Ni 75 to 78% by weight, Cr 2 to 3% by weight, Cu 4 to 6% by weight, Fe balance;
Ni 75 to 80% by weight, Mo 3 to 5% by weight, Cu 1 to 6% by weight, Fe balance;
79 to 82% by weight of Ni, 3.5 to 6% by weight of Mo, and the balance of Fe; and 75 to 78% by weight of Ni, 3 to 4.5% by weight of Mo, 4 to 6% by weight of Cu and the balance of Fe;
Wherein the high saturation magnetization material layer is formed of at least one soft magnetic material selected from the group consisting of
2-3% by weight of Si, balance of Fe;
47-50% by weight of Co, balance of Fe;
35-40% by weight of Co, balance of Fe;
Co 23 to 27% by weight, Fe balance; and Co 48 to 50% by weight, V1 to 3% by weight, Fe balance;
The magnetic memory device according to claim 1, wherein the magnetic memory device is formed of at least one soft magnetic material selected from the group consisting of: 3. The magnetic memory device according to claim 1, wherein the high saturation magnetization material layer has a flat or uneven film or plate shape, or a shape having a through hole such as a mesh or a slit. 4. An insulator layer or a conductor layer is sandwiched between the magnetization fixed layer and the magnetic layer, and the magnetic layer is generated by a magnetic field induced by flowing a current through wirings provided on an upper surface and a lower surface of the memory element, respectively. 2. The magnetic memory device according to claim 1, wherein the information is written by magnetizing the data in a predetermined direction, and the written information is read out by a tunnel magnetoresistance effect between the wirings.

Images