WO2003083939A1 - Magnetic shield package and seal material of magnetic non-volatile memory element - Google Patents

Abstract

A magnetic shield package and seal material of a magnetic non-volatile memory element for improving the record holding reliability of an MRAM element. A soft magnetic material containing resin composite material containing soft magnetic material mixed in resin is used as a seal resin (14) for sealing the MRAM element (11) so as to form a magnetic shield package (10). Thus, with respect to a low-frequency magnetic field, it is possible to suppress intrusion of magnetic flux into the MRAM element (11) thanks to the contribution of the real part μ’ term of the permeability. Moreover, with respect to the high-frequency magnetic field, thanks to the imaginary part μ” term, the magnetic field is absorbed as thermal energy and intrusion of the magnetic flux to the MRAM element (11) is suppressed. Furthermore, by sealing the MRAM element (11) so as to surround it, it is possible to effectively suppress intrusion of magnetic flux from various directions. Accordingly, it is possible to improve the record holding reliability of the MRAM element (11) with respect to the external magnetic field of a wide frequency range.

Description

Magnetic shield package and sealing material for magnetic nonvolatile memory element

Technical field

 Light

 The present invention relates to a magnetic shield package and a sealing material for a magnetic nonvolatile memory element, and more particularly to a magnetic shield package and a sealing material for a magnetic nonvolatile memory element for suppressing the influence of an external magnetic field on the magnetic nonvolatile memory element. About.

Background art

 In recent years, as a semiconductor memory, for example, as reported in the materials of the 116th meeting of the Japan Society of Applied Magnetics, etc., the development of magnetic random access memory (MRAM) has been advanced. I have.

 MRAM devices are semiconductor memories that use the magnetoresistive effect based on the spin-dependent conduction phenomenon peculiar to nanomagnets, and are non-volatile memories that can retain memory without external power supply.

 Information is written in this MRAM element by reversing the magnetic spins of the crossed cells by the synthetic magnetic field at the intersection of the bit line and the lead line arranged in a matrix, and changing the direction to "1", "0". Is stored as information. For reading, TMR (Tunneling

MagnetoResistance) effect. The TMR effect is a phenomenon in which the resistance value changes depending on the direction of the spin, and detects "1" and "0" of information according to the level of the resistance. MRAM devices are expected to be power-saving, high-speed, and nonvolatile large-capacity memories.

 However, since MRAM elements use a magnetic material for storing data, the problem is that information is erased or rewritten by an external magnetic field.

 MRAM elements are actually used mainly on high-density mounting boards inside electronic devices. On such a high-density mounting board, semiconductor elements, communication elements, ultra-small motors, etc. are mounted at high density due to the recent development of mounting technology. Also, inside the electronic equipment, antenna elements, various mechanical components, power supplies, etc. are mounted at high density to constitute one device.

 The magnetic field formed by each element and the like acts as an external magnetic field on the MRAM element where these elements and components are arranged close to each other.

 Fig. 8 is a diagram showing an example of the magnetic field intensity assumed to act on the MRAM element from the outside.

 For example, an AC magnetic field with a magnetic field strength of about 200 Oe to 300〇e and a frequency of about 50 Hz to 60 Hz from the motor arranged on the mounting board, It is assumed that an AC magnetic field having a magnetic field strength of about 100 Oe to 300 Oe and a frequency of about 50 Hz to several MHz acts on the MRAM element. A relatively low-frequency magnetic field component is constantly generated from the power supply and the power supply.

In addition, a permanent magnet or the like may be arranged near the MRAM element. In this case, for example, a direct current (DC) magnetic field having a magnetic field strength of about 100 OOe may act on the MRAM element. Further, the magnetic field formed near the mounting substrate (magnetic field near the substrate) is, for example, a magnetic field intensity of about 100〇e and a frequency Is expected to act as a high-frequency magnetic field exceeding several MHz and act on the MRAM element.

 In this way, a DC magnetic field component or an AC magnetic field component in a wide frequency range from low to high frequencies is mixed around the mounted MRAM element. On the other hand, the switching field strength of the MR AM element is about 30 3e to 50〇e, and in order to secure the record retention reliability of the MR AM element, the magnetic Is essential.

 The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a magnetic shield package of an MR AM element in which the influence of an external magnetic field on the MR AM element is suppressed and record retention reliability is improved. And

 Still another object of the present invention is to provide a sealing material for forming a magnetic shield package of an MRAM element. Disclosure of the invention

 According to the present invention, in an MR AM element magnetic shield package that suppresses the influence of an external magnetic field on the MR AM element, the MRAM element is sealed using a soft magnetic material-containing resin composite in which a soft magnetic material is mixed with a resin. A magnetic shield package of an MRAM element characterized by being provided.

 According to such a magnetic shield package of the MRAM element, the MRAM element is sealed using a soft magnetic material-containing resin composite containing a soft magnetic material such as a soft magnetic fiber. As a result, the magnetic flux of the external magnetic field is redirected or weakened by absorption in the magnetic shield package. As a result, the entry of magnetic flux into the MRAM element is suppressed.

In addition, such a soft magnetic material-containing resin composite may be used as a sealing material. As a result, the formation of the magnetic shield package of the MRAM element can be simplified. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a schematic sectional view of a magnetic shield package of an MRAM element.

 FIG. 2 is a diagram showing a second package structure.

 FIG. 3 is a diagram showing a third package structure.

 FIG. 4 is a diagram showing a fourth package structure.

 FIG. 5 is a diagram showing a fifth package structure.

 FIG. 6 is an explanatory view of forming a magnetic shield package by a transfer molding method.

 FIG. 7 is an explanatory view of forming a magnetic shield package by the potting method.

 FIG. 8 is a diagram showing an example of a magnetic field intensity assumed to act on the MRAM element from the outside. BEST MODE FOR CARRYING OUT THE INVENTION

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

 Fig. 1 is a schematic cross-sectional view of the magnetic shield package of the MR AM element. In the magnetic shield package 10, the MRAM element 11 is connected to the lead frame 13 by wire 12 The periphery of the element 11 is sealed with a sealing resin 14. The magnetic shield package 10 is connected to the substrate 20 by leads 13 a extending from the lead frame 13.

In the present invention, a soft magnetic material is used as a resin for the encapsulant of the MRAM element 11. Is used. As described above, by protecting the MR AM element 11 with the sealing resin 14 containing the soft magnetic material, it is possible to suppress the influence of the external magnetic field on the MR AM element 11.

 In other words, conventionally, for low-frequency magnetic fields, a substance with high magnetic permeability is placed near the MRAM element, and more magnetic flux flows through the substance, so that the magnetic flux to the MRAM element is reduced. A method was adopted to curb the entry of traffic. For high-frequency magnetic fields, a method has been adopted in which an electromagnetic wave absorbing material is arranged near the MRAM element, and the magnetic flux that has entered the material is converted into thermal energy and absorbed.

 In contrast, in the present invention, the MRAM element 11 is protected by using a soft magnetic material-containing resin composite as a sealing material. Thus, for a low-frequency magnetic field, the path of the magnetic flux is changed by the contribution of the real part / x ′ term of the magnetic permeability, and the entry of the magnetic flux into the MRAM element 11 is suppressed. Also, with respect to a high-frequency magnetic field, the magnetic field is absorbed as thermal energy by the contribution of the “imaginary part” of the magnetic permeability, and the entry of the magnetic flux into the MRAM element 11 is suppressed.

 In addition, since the MR AM element 11 is surrounded by a resin composite containing a soft magnetic material, the magnetic shield package 10 is capable of handling magnetic flux from various directions. Protect 1 effectively.

 Thereby, the record retention reliability of the MRAM element 11 can be improved. Further, generation of noise due to switching of the transistor can be suppressed beforehand.

In the magnetic shield package 10, since the entire MRAM element 11 is protected from an external magnetic field, for example, a soft magnetic plate may be formed on the MRAM element 11 or the MRAM element 1 It is not necessary to form a soft magnetic insulating film as a passivation film on itself. for that reason, The magnetic shield package 10 can be manufactured without changing the flow of the conventional semiconductor manufacturing process.

 If the magnetic shield package 10 shown in FIG. 1 is used as the first package structure, for example, the package structure of the MRAM element is, for example, the second to fifth packages shown in FIGS. 2 to 5 below. Here, in FIGS. 2 to 5, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

 FIG. 2 is a diagram showing a second package structure. In the second package structure, a lead frame 13 to which the MRAM element 11 is connected by a wire 12 is connected to the substrate 20 via a plurality of pole electrodes 15. Then, the entire MR AM element 11, the wire 12, the lead frame 13 and the pole electrode 15 on the substrate 20 are protected from the outside by the sealing resin 14 to form the magnetic shield package 10a. Have been.

 FIG. 3 is a diagram showing a third package structure. In the third package structure, as in the second package structure, a lead frame 13 in which the MRAM element 11 is connected with a wire 12 is connected via a plurality of pole electrodes 15. Connected to substrate 20. Then, the entire MRAM element 11 and the wire 12 on the lead frame 13 are protected from the outside by the sealing resin 14 to form the magnetic shield package 10b.

 FIG. 4 is a diagram showing a fourth package structure. In the fourth package structure, the MRAM element 11 is connected to the substrate 20 via the pole electrode 15. Then, the whole of the MRAM element 11 and the pole electrode 15 on the substrate 20 is protected from the outside by the sealing resin 14 to form the magnetic shield package 10c.

FIG. 5 is a diagram showing a fifth package structure. In this fifth package structure, the lead frame in which the MRAM element 11 is connected by the wire 12 is used. The arm 13 is connected by inserting a plurality of pins 16 extending therefrom into the board 20. Then, the entire MRAM element 11 and the wire 12 on the lead frame 13 are protected from the outside by the sealing resin 14 to form a magnetic shield package 10d.

 In this way, by encapsulating the MRAM element 11 in a state of surrounding it, it is possible to effectively suppress the entry of magnetic flux from various directions. Therefore, in addition to the mounting form in which the MRAM element 11 is electrically connected to the substrate 20 through the lead 13a, as described above, the MRAM element 11 is connected to the substrate 2 through the pole electrode 15 and the pin 16 as described above. Magnetic shielding against external magnetic fields is possible even in mounting forms such as BGA (Ball Grid Array) and PGA (Pin Grid Array) that are electrically connected to zero.

 In the magnetic shield packages 10, 10 a, 10 b, 10 c, and 10 d as described above, the soft magnetic material-containing resin composite used as the sealing material includes various soft magnetic materials. Can be used.

 Examples of the soft magnetic material of the soft magnetic material-containing resin composite include NiZn ferrite, MnZn ferrite, MgMn ferrite, NiZnCu ferrite, NiZnCo ferrite, and the like. Generally, a soft magnetic ferrite having a spinel structure is preferably used. As described above, such a soft magnetic ferrite has an effect of suppressing the entry of the magnetic flux by changing the course of the magnetic flux or absorbing the energy with respect to the low-frequency magnetic field and the high-frequency magnetic field due to its soft magnetic characteristics. Express. In addition, soft magnetic ferrite has a high electric resistance and, when used as a sealing material, can prevent a short circuit even if the particles enter between wirings.

Also, soft magnetic metal powders such as Fe, Co, and Ni, or FeNi, FeCo, FeA1, FeSi, FeSiAl, FeSiB the soft magnetic alloy powder of high magnetic permeability, such as C o S i B, absolute and more at S i 0 ₂ and highly insulating resin The coated material can be used as a soft magnetic material. This insulating coating is applied for the purpose of preventing a short circuit when particles enter between wirings, as in the case of soft magnetic ferrite.

As an insulation coating method, for example, first, a soft magnetic metal powder or a soft magnetic alloy powder and a silane coupling agent (for example, vinylmethoxytrisilane) are mixed and stirred, and a thin silane coupling layer is formed on the surface thereof. Is formed. Next, this powder is sealed in a vacuum container and heated to about 450 ° C., and the silane coupling layer is subjected to a thermal decomposition reaction to form a thin Si ₂ coating layer on the surface. Thereby, a soft magnetic material on which insulation coating has been performed can be obtained.

Furthermore, as the soft magnetic material, the soft magnetic metal powder or soft magnetic alloy powder of the above, to form a F e ₂ 0 ₃ or C o O is an oxide of the metal itself or alloy itself on the particle surfaces, the oxide It is also possible to use an insulating coating.

 In addition, as the resin used for the soft magnetic material-containing resin composite, an epoxy resin is usually preferably used. In addition, liquid crystal polymers, polyethylenes, polyamides, Ni-based resins, and the like are also preferably used in consideration of moldability.

 The soft magnetic material-containing resin composite has a composition in which a certain amount of soft magnetic material capable of suppressing the entry of magnetic flux is mixed with the resin, or a composition in which only the soft magnetic material is mixed with the resin. Is also good. The content of the soft magnetic material in the soft magnetic material-containing resin composite can be appropriately changed according to the mounting environment of the MRAM element 11.

The particle shape of the soft magnetic material may be of various shapes in consideration of the filling factor necessary for suppressing the entry of magnetic flux and the fluidity of the soft magnetic material-containing resin composite. As the soft magnetic ferrite, crushed particles having a diameter of several m to several tens of m, which are produced by a known method and are commercially available, can be used. Further, in order to further increase the filling rate and ensure fluidity, spherical particles formed by a granulation method such as a spray drying method can be used.

 Examples of the soft magnetic material coated with an insulating material include those having a crushed shape and a spherical shape as described above, and those having a flat shape to a thickness (skin depth) at which a high-frequency electromagnetic field enters the particle skin. Alternatively, a disc-shaped or elliptical one may be used.

 When a magnetic shield package is formed from a soft magnetic material-containing resin composite using such a soft magnetic material and a resin, a transfer mold method or a potting method can be used. Here, the filling ratio of the soft magnetic material of the soft magnetic material-containing resin composite is 50% by volume or more. The maximum filling rate of ordinary soft magnetic material powder is about 85% by volume, but the filling rate is less than 85% by volume in order to develop the particle shape, required viscosity and particle size Often.

 Hereinafter, a method for forming the magnetic shield package will be described with reference to specific examples.

 In forming a magnetic shield package, first, a soft magnetic material and a resin are mixed using an ender and three rolls to form a resin composite containing a soft magnetic material. At this time, the filling rate is 60% by volume to 80% by volume for transfer molding, and 50% by volume to "(0% by volume" for potting requiring low viscosity.

 FIG. 6 is an explanatory view of forming a magnetic shield package by the transfer molding method.

In the case of the transfer molding method, first, the soft magnetic material-containing resin composite 31 after mixing is processed into a tablet by a known method. Then 643

10 This tablet-shaped soft magnetic material-containing resin composite 31 is set in a mold 32 of a molding machine, and is heated to a temperature of 150 ° C. (approximately 180 ° C.). The soft magnetic material-containing resin composite 31 is extruded at a predetermined extrusion pressure by a jaw 33 to seal the MRAM element 11.

 FIG. 7 is an explanatory view of forming a magnetic shield package by the potting method.

 In the case of the potting method, first, the soft magnetic material-containing resin composite 41 after mixing is injected into a dispenser 42. Then, the MRAM element 11 on the substrate 20 is partitioned by the dam 43, and the soft magnetic material-containing resin composite 41 is placed above the target MRAM element 11 at a constant extrusion pressure from the transducer 42. And seal the MRAM element 11.

 In this manner, the soft magnetic material is mixed with the resin to form a soft magnetic material-containing resin composite, and the MRAM element 11 is sealed using the soft magnetic material-containing resin composite. Therefore, the soft magnetic material-containing resin composite can be easily adjusted, and the magnetic shield package can be formed inexpensively and easily without changing the flow of the conventional semiconductor manufacturing process. Industrial applicability

 As described above, in the present invention, the MRAM element is sealed with a soft magnetic material-containing resin composite in which a soft magnetic material is mixed with a resin to form a magnetic shield package. As a result, entry of magnetic flux into the MRAM element against an external magnetic field ranging from a low frequency to a high frequency is suppressed, and the record retention reliability thereof can be improved.

In addition, the soft magnetic material-containing resin composite used as the sealing material of the magnetic shield package is easy to adjust, and the use of such a sealing material makes it possible to form the magnetic shield package at low cost and simply. Can do it can.

Claims

The scope of the claims 1. In a magnetic non-volatile memory element magnetic shield package that suppresses the influence of an external magnetic field on the magnetic non-volatile memory element,  A magnetic shield package for a magnetic nonvolatile memory element, wherein the magnetic nonvolatile memory element is sealed using a soft magnetic material-containing resin composite in which a soft magnetic material is mixed with a resin.  2. The magnetic nonvolatile memory element according to claim 1, wherein the magnetic nonvolatile memory element is sealed with its periphery surrounded by the soft magnetic material-containing resin composite. Shield package. 3. The magnetic shield package for a magnetic nonvolatile memory element according to claim 1, wherein the soft magnetic material is formed by insulating coating of soft magnetic ferrite, soft magnetic metal or soft magnetic alloy. 4. In the encapsulant for forming the magnetic shield package of the magnetic nonvolatile memory element,  A sealing material comprising a soft magnetic material-containing resin composite obtained by mixing a soft magnetic material with a resin.  5. The sealing material according to claim 4, wherein the soft magnetic material is made of soft magnetic ferrite or a soft magnetic metal or a soft magnetic alloy.