JP2009218611A - Magneto-resistance effect element, magnetic memory device, and method of manufacturing magneto-resistance effect element and magnetic memory device - Google Patents

Abstract

A magnetoresistive element having good magnetic characteristics by controlling magnetic anisotropy of a ferromagnetic layer is provided.
A magnetoresistive element 1 having a configuration in which a pair of ferromagnetic layers are opposed to each other through an intermediate layer, and a change in magnetoresistance is obtained by passing a current perpendicular to the film surface. One of the layers is a magnetization fixed layer 5, the other is a magnetization free layer 7, the ferromagnetic layers 5 and 7 have an amorphous or microcrystalline structure, and the ferromagnetic layers 5 and 7 have a magnetization free of 300 ° C. or more. A magnetoresistive element 1 that is heat-treated in a magnetic field below the crystallization temperature of the layer 7 is formed.
[Selection] Figure 1

Description

  The present invention relates to a magnetoresistive effect element configured to obtain a magnetoresistive change by flowing a current perpendicular to a film surface and a magnetic memory device including the magnetoresistive effect element. The present invention also relates to a method for manufacturing the magnetoresistive effect element and a method for manufacturing the magnetic memory device.

  With the rapid spread of information communication devices, especially small personal devices such as portable terminals, the elements such as memory and logic that compose this device have higher performance such as higher integration, higher speed, and lower power consumption. Is required. In particular, increasing the density and capacity of non-volatile memory is becoming increasingly important as a technology for replacing hard disks and optical discs that are essentially impossible to miniaturize due to the presence of moving parts.

Examples of the nonvolatile memory include a flash memory using a semiconductor and an FRAM (Ferro electric Random Access Memory) using a ferroelectric.
However, the flash memory has a drawback that the writing speed is as slow as the order of μ seconds. On the other hand, in FRAM, a problem that the number of rewritable times is small has been pointed out.

  As a non-volatile memory free from these drawbacks, MRAM (Magnetic Random Access Memory) as described in, for example, “Wang et al., IEEE Trans. Magn. 33 (1997), 4498” is attracting attention. It is a magnetic memory called. Since this MRAM has a simple structure, it can be easily integrated and has a large number of rewritable times in order to perform recording by rotating a magnetic moment. The access time is also expected to be very high, and it has already been confirmed that it can operate in the nanosecond range.

  The magnetoresistive effect element used in this MRAM, in particular, the tunnel magnetoresistive effect (TMR) element, is basically composed of a ferromagnetic tunnel junction composed of a laminate of a ferromagnetic layer / tunnel barrier layer / ferromagnetic layer. The In this element, when an external magnetic field is applied between the ferromagnetic layers with a constant current flowing between the ferromagnetic layers, a magnetoresistive effect appears according to the relative angle of magnetization of both magnetic layers. When the magnetization directions of both ferromagnetic layers are antiparallel, the resistance value is maximized, and when they are parallel, the resistance value is minimized. The function as a memory element is brought about by creating an antiparallel and parallel state by an external magnetic field.

  In particular, in a spin valve type TMR element, one of the ferromagnetic layers is antiferromagnetically coupled to an adjacent antiferromagnetic layer, thereby forming a magnetization fixed layer in which the magnetization direction is always constant. The other ferromagnetic layer is a magnetization free layer whose magnetization is easily reversed by an external magnetic field or the like. This magnetization free layer becomes an information recording layer in the magnetic memory.

In the spin valve type TMR element, the rate of change in resistance value is expressed by the following formula (A), where the spin polarizabilities of the respective ferromagnetic layers are P1 and P2.
2P1P2 / (1-P1P2) (A)
Thus, the resistance change rate increases as the respective spin polarizabilities increase.

  Incidentally, the basic configuration of the MRAM is, for example, as disclosed in JP-A-10-116490, a plurality of bit write lines (so-called bit lines) and a plurality of words orthogonal to the plurality of bit write lines. A write line (so-called word line) is provided, and a TMR element is arranged as a magnetic memory element at the intersection of the bit write line and the word write line. When recording with such an MRAM, selective writing is performed on the TMR element using the asteroid characteristic.

In MRAM, if the magnetic characteristics of the TMR element vary from element to element, or if there are variations when the same element is used repeatedly, there is a problem that selective writing using the asteroid characteristic becomes difficult.
Accordingly, the TMR element is also required to have a magnetic characteristic for drawing an ideal asteroid curve.
In order to draw an ideal asteroid curve, there is no noise such as Barkhausen noise in the RH (resistance-magnetic field) loop when TMR measurement is performed, the squareness of the waveform is good, and the magnetization state Must be stable and have little variation in coercive force Hc.

  Barkhausen noise, deterioration of squareness, and variation in coercive force are mainly caused by the magnetic anisotropy of the material. If the direction and strength of magnetic anisotropy are dispersed in the plane of the film, these problems may occur, and thus the direction control of magnetic anisotropy is very important.

  In order to solve the above-described problems, in the present invention, a magnetoresistive effect element having good magnetic characteristics by controlling the magnetic anisotropy of the ferromagnetic layer, and an excellent writing provided with the magnetoresistive effect element are provided. It is an object of the present invention to provide a magnetic memory device having characteristics, a magnetoresistive effect element, and a method of manufacturing the magnetic memory device.

The magnetoresistive effect element according to the present invention has a configuration in which a pair of ferromagnetic layers are opposed to each other via an intermediate layer, and a magnetoresistance change is obtained by flowing a current perpendicular to the film surface. One of them is a magnetization fixed layer and the other is a magnetization free layer, the ferromagnetic layer has an amorphous or microcrystalline structure, and the ferromagnetic layer is heat-treated in a magnetic field at a temperature of 300 ° C. or more and below the crystallization temperature of the magnetization free layer. It is what.

The magnetic memory device of the present invention includes a magnetoresistive element having a configuration in which a pair of ferromagnetic layers are opposed to each other through an intermediate layer, and a magnetoresistance change is obtained by flowing a current perpendicular to the film surface, A word line and a bit line sandwiching the resistive element in the thickness direction, one of the ferromagnetic layers is a magnetization fixed layer and the other is a magnetization free layer, the ferromagnetic layer has an amorphous or microcrystalline structure, The ferromagnetic layer is heat-treated in a magnetic field at a temperature not lower than 300 ° C. and not higher than the crystallization temperature of the magnetization free layer.

The method of manufacturing a magnetoresistive effect element according to the present invention has a configuration in which a pair of ferromagnetic layers are opposed to each other through an intermediate layer, and a magnetoresistance change is obtained by flowing a current perpendicular to the film surface. One of the magnetic layers is a magnetization fixed layer and the other is a magnetization free layer. When manufacturing a magnetoresistive effect element having a ferromagnetic layer having an amorphous or microcrystalline structure, at least after forming the magnetization free layer, 300 A step of performing a heat treatment in a magnetic field at a temperature not lower than ℃ and not higher than the crystallization temperature of the magnetization free layer is performed.

The method for manufacturing a magnetic memory device of the present invention has a configuration in which a pair of ferromagnetic layers are opposed to each other through an intermediate layer, and a magnetoresistance change is obtained by passing a current perpendicular to the film surface. One of the layers is a magnetization fixed layer, the other is a magnetization free layer, and the ferromagnetic layer has an amorphous or microcrystalline structure, and a word line and a bit line sandwiching the magnetoresistive element in the thickness direction When a magnetic memory device including the above is manufactured, at least a magnetization free layer is formed, and then a step of performing a heat treatment in a magnetic field at 300 ° C. or more and below the crystallization temperature of the magnetization free layer is performed.

According to the configuration of the magnetoresistive effect element of the present invention described above, one of the ferromagnetic layers is a fixed magnetization layer and the other is a magnetization free layer, the ferromagnetic layer has an amorphous or microcrystalline structure, and is ferromagnetic. Since the magnetic anisotropy of the ferromagnetic layer is controlled by the heat treatment in the magnetic field because the layer is heat-treated in the magnetic field at a temperature of 300 ° C. or more and the crystallization temperature of the magnetization free layer, the resistance of the magnetoresistive effect element—the external magnetic field It becomes possible to improve the squareness of the curve and to improve the variation in coercive force.

  According to the above-described configuration of the magnetic memory device of the present invention, the magnetoresistive effect element includes the magnetoresistive effect element, and the word line and the bit line sandwiching the magnetoresistive effect element in the thickness direction. Due to the configuration of the effect element, the magnetic anisotropy of the ferromagnetic layer is controlled by the heat treatment in the magnetic field, the squareness of the resistance-external magnetic field curve of the magnetoresistive effect element is improved, and the coercivity variation is improved. Therefore, the shape of the asteroid curve of the magnetoresistive element is improved, and the selective writing of information in the magnetic memory device can be performed easily and stably.

  According to the above-described method of manufacturing a magnetoresistive element of the present invention, at least the magnetization free layer is formed and then subjected to a heat treatment in a magnetic field at a crystallization temperature of 300 ° C. or higher and lower than the crystallization temperature of the magnetization free layer. By controlling the magnetic anisotropy of the free layer, it becomes possible to manufacture a magnetoresistive effect element in which the squareness of the resistance-external magnetic field curve of the magnetoresistive effect element and the variation in coercive force are improved.

  According to the above-described method for manufacturing a magnetic memory device of the present invention, at least a magnetization free layer is formed by performing a heat treatment in a magnetic field at 300 ° C. or more and below the crystallization temperature of the magnetization free layer after forming at least the magnetization free layer. The magnetic anisotropy of the layer is controlled to improve the squareness of the resistance-external magnetic field curve of the magnetoresistive effect element and the variation in coercive force, and the magnetic memory device capable of easily and stably writing information selectively is manufactured. It becomes possible.

According to the magnetoresistive effect element and the manufacturing method thereof according to the present invention described above, it is possible to improve the squareness of the RH curve and the variation in coercive force.
As a result, when the magnetoresistive effect element is applied to a magnetic memory device, write errors can be reduced and excellent write characteristics can be obtained.

  Moreover, according to the magnetic memory device and the manufacturing method thereof of the present invention, excellent write characteristics can be realized.

It is a schematic block diagram of the TMR element of one embodiment of this invention. It is the figure which compared the resistance-external magnetic field curve of a TMR element in the case where the temperature of the heat processing in a magnetic field is 300 degreeC, and 250 degreeC. It is a figure which shows one form of the heat processing furnace used for the heat processing in a magnetic field. It is a schematic block diagram of the TMR element which has a laminated ferri structure. It is a schematic block diagram which shows the principal part of the crosspoint type | mold MRAM array which has the TMR element of this invention as a memory cell. FIG. 6 is an enlarged cross-sectional view of the memory cell shown in FIG. 5 . FIGS. 4A and 4B are diagrams showing a process flow when manufacturing an MRAM according to the present invention. FIGS. It is a top view of TEG for evaluation of a TMR element. It is sectional drawing in AA of FIG. It is a figure which shows the relationship between the heat processing temperature and the dispersion | variation in coercive force Hc.

The present invention relates to a magnetoresistive effect element having a configuration in which a pair of ferromagnetic layers are opposed to each other through an intermediate layer, and a magnetoresistive effect is obtained by flowing a current perpendicular to the film surface. One of them is a magnetization fixed layer and the other is a magnetization free layer, the ferromagnetic layer has an amorphous or microcrystalline structure, and the ferromagnetic layer is heat-treated in a magnetic field at a temperature of 300 ° C. or more and below the crystallization temperature of the magnetization free layer. This is a magnetoresistive effect element.

  According to the present invention, in the magnetoresistive element, the magnetization free layer is made of a material selected from FeCoB, FeCoNiB, and FeCoSiB.

  According to the present invention, the magnetoresistive element is a tunnel magnetoresistive element using a tunnel barrier layer made of an insulator or a semiconductor as the intermediate layer.

  According to the present invention, the magnetoresistive element has a laminated ferri structure.

According to the present invention, a magnetoresistive effect element having a configuration in which a pair of ferromagnetic layers are opposed to each other through an intermediate layer and a change in magnetoresistance is obtained by flowing a current perpendicular to the film surface, and a magnetoresistive effect element A word line and a bit line sandwiched in the thickness direction, one of the ferromagnetic layers being a magnetization fixed layer and the other being a magnetization free layer, the ferromagnetic layer having an amorphous or microcrystalline structure, The magnetic memory device is heat-treated in a magnetic field at a temperature of 300 ° C. or higher and lower than the crystallization temperature of the magnetization free layer.

  According to the present invention, in the above magnetic memory device, the magnetization free layer is made of a material selected from FeCoB, FeCoNiB, and FeCoSiB.

  According to the present invention, in the above magnetic memory device, the magnetoresistive effect element is a tunnel magnetoresistive effect element using a tunnel barrier layer made of an insulator or a semiconductor as an intermediate layer.

  According to the present invention, in the magnetic memory device, the magnetoresistive element has a laminated ferrimagnetic structure.

  First, FIG. 1 shows a schematic configuration diagram of an embodiment of a magnetoresistive element of the present invention. The embodiment shown in FIG. 1 shows a case where the present invention is applied to a tunnel magnetoresistive element (hereinafter referred to as a TMR element).

The TMR element 1 includes a base layer 3, an antiferromagnetic layer 4, a magnetization fixed layer 5 that is a ferromagnetic layer, a tunnel barrier layer 6, and a magnetization that is a ferromagnetic layer on a substrate 2 made of silicon or the like. The free layer 7 and the top coat layer 8 are laminated in this order.
That is, a so-called spin-valve type TMR element is formed in which one of the ferromagnetic layers is a magnetization fixed layer 5 and the other is a magnetization free layer 7. A ferromagnetic tunnel junction 9 is formed by sandwiching the tunnel barrier layer 6 with the magnetization free layer 7.
When the TMR element 1 is applied to a magnetic memory device or the like, the magnetization free layer 7 becomes an information recording layer, and information is recorded there.

The antiferromagnetic layer 4 is antiferromagnetically coupled to the magnetization fixed layer 5 that is one of the ferromagnetic layers, so that the magnetization of the magnetization fixed layer 5 is not reversed even by a current magnetic field for writing, and the magnetization is fixed. This is a layer for always keeping the magnetization direction of the layer 5 constant. That is, in the TMR element 1 shown in FIG. 1, only the magnetization free layer 7 which is the other ferromagnetic layer is reversed in magnetization by an external magnetic field or the like. The magnetization free layer 7 is also referred to as an information recording layer because it becomes a layer on which information is recorded when the TMR element 1 is applied to, for example, a magnetic memory device or the like.
As a material constituting the antiferromagnetic layer 4, an Mn alloy containing Fe, Ni, Pt, Ir, Rh, Co oxide, Ni oxide, or the like can be used.

  In the spin valve TMR element 1 shown in FIG. 1, the magnetization fixed layer 5 is antiferromagnetically coupled to the antiferromagnetic layer 4 so that the magnetization direction is made constant. For this reason, the magnetization of the magnetization fixed layer 5 is not reversed even by a current magnetic field at the time of writing.

The tunnel barrier layer 6 is a layer for magnetically separating the magnetization fixed layer 5 and the magnetization free layer 7 and flowing a tunnel current.
As a material constituting the tunnel barrier layer 6, for example, an insulating material such as an oxide such as Al, Mg, Si, Li, or Ca, a nitride, or a halide can be used.

Such a tunnel barrier layer 6 can be obtained by oxidizing or nitriding a metal film formed by sputtering or vapor deposition.
It can also be obtained by a CVD method using an organic metal and oxygen, ozone, nitrogen, halogen, halogenated gas, or the like.

In the present embodiment, the ferromagnetic tunnel junction 9 including the magnetization fixed layer 5 and the magnetization free layer 7 which are particularly ferromagnetic layers is subjected to a heat treatment in a magnetic field at 300 ° C. or higher.
With such a configuration, the squareness of the RH curve can be improved, and the variation in coercive force can be reduced.

  The direction of the magnetic field in this heat treatment in a magnetic field is preferably parallel to the easy axis of magnetization of the ferromagnetic layers 5 and 7.

  For the ferromagnetic layer, in particular, the magnetization free layer 7, any one of Fe, Co, and Ni, or an amorphous or microcrystalline material containing a plurality of these as a main component is preferable.

  Note that an alloy mainly composed of Fe, Co, and Ni, such as FeCo, is crystalline in a normal film thickness, but when it is very thin, for example, about 1 nm, it becomes close to an amorphous state. The effect of the heat treatment at 300 ° C. or higher is obtained. However, this alloy has crystal magnetic anisotropy, and since this crystal magnetic anisotropy is difficult to control by heat treatment, the effect is less than that of an amorphous material.

Here, the spin-valve type TMR element in which the magnetization free layer 7 is made of an amorphous ferromagnetic material having a composition of Co72Fe8B20 (atomic%) is subjected to heat treatment in a static magnetic field at 300 ° C., and at 250 ° C. FIG. 2 shows the results obtained by actually producing the samples subjected to the heat treatment in the static magnetic field and measuring the resistance-external magnetic field curve (RH curve) for these.
As is clear from FIG. 2, the TMR element heat-treated at 300 ° C. improved the squareness of the RH curve and also reduced Barkhausen noise as compared with the TMR element heat-treated at 250 ° C. Therefore, according to the present invention, the shape of the asteroid curve is also improved, the writing characteristics are improved, and the writing error can be reduced.

  The reason why the characteristics are improved under the heat treatment conditions of 300 ° C. or higher is not clear, but is considered to be related to a temperature lower than the crystallization temperature of the material and close to the Curie temperature.

A heat treatment furnace for performing heat treatment in a magnetic field is configured as shown in FIG. 3, for example.
This heat treatment furnace has a heater 32 disposed outside the vacuum chamber 31 and a magnet 33 disposed further outside.

In this heat treatment furnace, heat treatment in a magnetic field is performed as follows.
First, the wafer 30 on which the TMR element is formed is placed on the rack 34 in the vacuum chamber 31 so that the main surface 30A of the wafer 30 is parallel to the direction of the magnetic field 35 by the magnet 33.
The TMR element of the wafer 30 can be heat-treated in the magnetic field by heating with the heater 32 and applying a magnetic field with the magnet 33.

  In addition, the upper limit of the temperature of the heat treatment in the magnetic field is determined by the crystallization temperature of the amorphous or microcrystalline material used for the ferromagnetic layer, and is at most 400 ° C. or less in consideration of the heat resistance of the TMR element. .

Since the heat treatment in the magnetic field is performed for the purpose of improving the magnetization reversal characteristics of the ferromagnetic layer, at least the magnetization free layer 7 and more preferably both the magnetization free layer 7 and the magnetization fixed layer 5 are processed. .
Thereby, the effect of improving the magnetic characteristics of the TMR element 1 can be obtained more remarkably.

  For example, in order to make the above-described heat treatment more effective, it is desirable that the film thickness of the amorphous or microcrystalline material used for the magnetization free layer 7 is 1 nm or more and 15 nm or less. By being in this range, good magnetic properties can be secured. When the thickness of the magnetization free layer 7 is less than 1 nm, the magnetic characteristics are greatly impaired due to mutual diffusion due to heat. Conversely, when the thickness of the magnetization free layer 7 exceeds 15 nm, the TMR element 1 Since the coercive force becomes excessively high, there is a possibility that it becomes inappropriate for practical use.

  Similarly, when an amorphous or microcrystalline material is used for the magnetization fixed layer 5, in order to make the above-described heat treatment more effective, the amorphous or microcrystalline material used for the magnetization fixed layer 5 is also changed. The film thickness is desirably 0.5 nm or more and 6 nm or less. By being in this range, good magnetic properties can be secured. When the thickness of the magnetization pinned layer 5 is less than 0.5 nm, the magnetic characteristics are greatly impaired due to mutual diffusion due to heat. Conversely, when the thickness of the magnetization pinned layer 5 exceeds 6 nm, There is a possibility that a sufficient exchange coupling magnetic field with the magnetic layer 4 cannot be obtained.

  According to the TMR element 1 of the present embodiment described above, the magnetic layers 5 and 7 are magnetically different from each other by being subjected to a heat treatment in a magnetic field at 300 ° C. or higher and below the crystallization temperature of the magnetization free layer 7. By controlling the directionality, the squareness of the RH curve can be improved, and Barkhausen noise can be reduced. Further, it is possible to improve the shape of the asteroid curve of the TMR element 1 by suppressing variations in the coercive force Hc.

Accordingly, for example, when the TMR element 1 is applied to a magnetic memory device having a large number of TMR elements, the write error is improved by improving the shape of the asteroid curve of the TMR element 1 and improving the write characteristics. Can be reduced.
In addition, when applied to a magnetic head or a magnetic sensor having a TMR element, it is possible to suppress a deviation from the design value of the reversal magnetic field to improve manufacturing yield and prevent malfunction. Become.

In the present invention, the magnetization fixed layer 5 and the magnetization free layer 7 as shown in FIG. 1 are not limited to the TMR element 1 constituted by a single layer.
For example, as shown in FIG. 4, the magnetization fixed layer 5 has a laminated ferrimagnetic structure in which a nonmagnetic conductor layer 5c is sandwiched between a first magnetization fixed layer 5a and a second magnetization fixed layer 5b. However, the effect of the present invention can be obtained.

  In the TMR element 10 shown in FIG. 4, the first magnetization fixed layer 5 a is in contact with the antiferromagnetic layer 4, and the first magnetization fixed layer 5 a has a strong unidirectional magnetic force due to the exchange interaction acting between these layers. Has anisotropy. The second magnetization fixed layer 5b is opposed to the magnetization free layer 7 through the tunnel barrier layer 6, and the spin direction is compared with the magnetization free layer 7 to become a ferromagnetic layer directly related to the MR ratio. Also called a layer.

  Examples of the material used for the nonmagnetic conductor layer 5c having the laminated ferrimagnetic structure include Ru, Rh, Ir, Cu, Cr, Au, and Ag. In the TMR element 10 of FIG. 4, the other layers have substantially the same configuration as the TMR element 1 shown in FIG. 1, and thus the same reference numerals as those in FIG.

  Also in the TMR element 10 having this laminated ferrimagnetic structure, by performing a heat treatment in a magnetic field at 300 ° C. or more and below the crystallization temperature of the magnetization free layer 7, similarly to the TMR element 1 shown in FIG. The squareness of the RH curve can be improved and Barkhausen noise can be reduced. Further, the variation of the coercive force Hc can be suppressed, and the shape of the asteroid curve of the TMR element 10 can be improved.

In the above-described embodiment, the TMR elements (tunnel magnetoresistive effect elements) 1 and 10 are used as the magnetoresistive effect element. However, in the present invention, the pair of ferromagnetic layers are opposed to each other through the intermediate layer. The present invention can also be applied to other magnetoresistive elements having a configuration in which a current flows perpendicularly to the surface to obtain a magnetoresistance change.
For example, a giant magnetoresistive effect element (GMR element) using a nonmagnetic conductive layer such as Cu as an intermediate layer, and a structure in which a current flows perpendicularly to the film surface to obtain a magnetoresistive effect, that is, a so-called CPP type GMR element The present invention can also be applied to.

  Furthermore, the material of the magnetization fixed layer and the antiferromagnetic material, the presence or absence of the laminated ferri structure on the magnetization fixed layer side, and the like can be variously modified without impairing the essence of the present invention.

The range of the strength of the magnetic field in the heat treatment in the magnetic field is 300 ° C. in the configuration in which the magnetization free layer 7 is on the upper layer side than the magnetization fixed layer 5 (so-called bottom spin type) as in the TMR element 1 of the above-described embodiment. Since the above heat treatment in a magnetic field also serves as a heat treatment for determining a bias applied from the antiferromagnetic layer 4 to the magnetization fixed layer 5, it varies depending on the structure, film thickness, and characteristics of the magnetization fixed layer 5.
For example, when the magnetization fixed layer 5 is composed of only a CoFe film having a thickness of 2 nm (single layer) and the material of the antiferromagnetic layer 4 is FeMn, RhMn, IrMn, or the like, a magnetic field of about 1 kOe is sufficient.
Even in a configuration in which the magnetization fixed layer 5 is only a CoFe film having a thickness of 2 nm (single layer), when the material of the antiferromagnetic layer 4 is PtMn or the like, about 3 kOe is required.
Further, in the case where a strong antiferromagnetic coupling is formed by the magnetization fixed layer 5 having a laminated ferrimagnetic structure, such as the TMR element 10 shown in FIG. 4, a plurality of the antiferromagnetic couplings are formed. It is necessary to make all the magnetic layers have magnetization in the same direction. For example, in the case of the magnetization fixed layer 5 having a structure of CoFe (2 nm) / Ru (0.8 nm) / CoFe (2 nm), a magnetic field of about 10 kOe is required.
On the other hand, there is no particular upper limit on the magnitude of the magnetic field, but the magnetic field applying means needs to be enlarged in order to increase the magnetic field.

  Magnetoresistive elements such as the above-described TMR elements 1 and 10 are suitable for use in magnetic memory devices such as MRAM, for example. Hereinafter, the MRAM using the TMR element of the present invention will be described with reference to the drawings.

  FIG. 5 shows a cross-point type MRAM array having the TMR element of the present invention. This MRAM array has a plurality of word lines WL and a plurality of bit lines BL orthogonal to the word lines WL, and the TMR element of the present invention is arranged at the intersection of the word lines WL and the bit lines BL. And a memory cell 11. That is, in this MRAM array, 3 × 3 memory cells 11 are arranged in a matrix.

  The TMR element used in the MRAM array is not limited to the TMR element 1 shown in FIG. 1, and a current flows perpendicularly to the film surface, such as the TMR element 10 shown in FIG. 4 having a laminated ferri structure. In the magnetoresistive effect element having a configuration in which the magnetoresistance change is obtained by the above, any configuration may be used as long as it is heat-treated in a magnetic field at 300 ° C. or higher and at least the ferromagnetic layer including the magnetization free layer 7 is made of an amorphous material. Absent.

One memory cell is taken out from a large number of memory cells in the memory element, and a cross-sectional structure is shown in FIG.
As shown in FIG. 6, each memory cell 11 includes a transistor 16 including a gate electrode 13, a source region 14, and a drain region 15 on, for example, a silicon substrate 12. The gate electrode 13 constitutes a read word line WL1. A write word line (corresponding to the above-described word write line) WL2 is formed on the gate electrode 13 via an insulating layer. A contact metal 17 is connected to the drain region 15 of the transistor 16, and a base layer 18 is connected to the contact metal 17. The TMR element 1 of the present invention is formed on the base layer 18 at a position corresponding to the upper side of the write word line WL2. On the TMR element 1, bit lines (corresponding to the bit write lines described above) BL orthogonal to the word lines WL1 and WL2 are formed. The underlayer 18 is also referred to as a bypass because of the role of electrical connection between the TMR element 1 and the drain region 15 having different planar positions.
Further, it includes an interlayer insulating film 19 and an insulating film 20 for insulating each word line WL1, WL2 and the TMR element 1, and a passivation film (not shown) for protecting the whole.

  Since this MRAM uses the TMR element 1 in which the magnetic anisotropy of the magnetization free layer 7 is controlled by a heat treatment in a magnetic field of 300 ° C. or more and a crystallization temperature or less, noise is reduced in the RH curve, and asteroid Since the characteristics are improved, write errors can be reduced.

Here, FIG. 7A and FIG. 7B each show a process flow in the case of manufacturing the MRAM by the manufacturing method of the present invention.
After a CMOS circuit (for example, the transistor 16 in FIG. 6) is formed on the substrate, a word line (for example, W2 in FIG. 6) is formed, the word line is embedded, the surface is planarized, and a TMR film is formed. The processes up to the process are the same in FIGS. 7A and 7B.

In the process flow shown in FIG. 7A, after the TMR film is formed, heat treatment in a magnetic field is performed immediately, and then the bypass forming step, that is, the patterning of the underlayer 18 in FIG. 6, the element portion forming step, that is, the patterning of the TMR element 1, The embedding step, that is, the step of embedding the TMR element 1 with an insulating film, the bit line forming step, and the bit line embedding step are performed.
Further, in the process flow shown in FIG. 7B, after the TMR film is formed and then the bypass formation step, the element portion formation step, the element embedding step, the bit line formation step, and the bit line embedding step are performed, Heat treatment is performed in a magnetic field.

  In any case, it is desirable to perform a heat treatment in a magnetic field after forming the TMR film, but it is necessary to at least after forming the magnetization free layer 7 of the TMR film.

For example, a configuration in which the arrangement of the magnetization fixed layer and the magnetization free layer is opposite to the configuration of the above-described embodiment (so-called bottom spin type), that is, the magnetization fixed layer and the antiferromagnetic layer on the substrate side Is formed above the magnetization free layer (so-called top spin type), after forming the ferromagnetic film of the magnetization free layer, after performing heat treatment in a magnetic field at 300 ° C. or higher, It is conceivable to perform a heat treatment in a magnetic field at less than 300 ° C. to form a magnetic layer and then to regularize the antiferromagnetic layer (determine the bias described above).
In this case, the heat treatment in the magnetic field is performed twice. Compared with the case where the heat treatment in the magnetic field at 300 ° C. or higher is performed after forming the magnetization fixed layer and the antiferromagnetic layer, the magnetization fixed near the surface of the TMR film. The layer and the antiferromagnetic layer have the advantage that they are not affected by a temperature of 300 ° C. or higher.

(Example)
Hereinafter, specific examples to which the present invention is applied will be described based on experimental results.
As shown in FIG. 6, the MRAM includes a switching transistor 16 in addition to the TMR element 1. In this embodiment, in order to investigate the TMR characteristic, ferromagnetic elements as shown in FIGS. The characteristics were measured and evaluated using a wafer on which only a tunnel junction was formed.
First, the heat treatment temperature dependence when various materials were used for the magnetization free layer of the ferromagnetic tunnel junction was investigated.

<Sample 1>
As shown in a plan view in FIG. 8 and a cross-sectional view taken along line AA in FIG. 8, a word line WL and a bit line BL are orthogonally crossed on a substrate 21 as a characteristic evaluation element TEG (Test Element Group). Thus, a structure in which the TMR element 22 is formed at a portion where the word line WL and the bit line BL intersect is manufactured. In this TEG, the TMR element 22 has an elliptical shape with a minor axis of 0.5 μm and a major axis of 1.0 μm, and terminal pads 23 and 24 are formed at both ends of the word line WL and the bit line BL, respectively. The line BL is electrically insulated from each other by insulating films 25 and 26 made of Al ₂ O ₃ .

Specifically, the TEG shown in FIGS. 8 and 9 was produced as follows.
First, a substrate 21 made of silicon having a thickness of 0.6 mm having a thermal oxide film (thickness: 2 μm) formed on the surface was prepared.
Next, a word line material was formed on the substrate 21, masked by photolithography, and then portions other than the word lines were selectively etched by Ar plasma to form word lines WL. At this time, regions other than the word line WL were etched to a depth of 5 nm of the substrate 21.
Thereafter, an insulating film 26 was formed to cover the word line WL, and the surface was flattened.

Subsequently, a TMR element 22 having the following layer structure (1) was produced by a known lithography method and etching. In the layer structure (1), the left side of / is the substrate side, and the inside of () indicates the film thickness.
Ta (3 nm) / Cu (100 nm) / PtMn film (20 nm) / CoFe (3 nm) / Ru (0.8 nm) / CoFe (2.5 nm) / Al (1 nm) -Ox / magnetization free layer (tnm) / Ta (5 nm)-(1)

In the layer configuration (1), the composition of the magnetization free layer was Co72Fe8B20 (atomic%), and the film thickness t of the magnetization free layer was 4 nm.
The composition of each CoFe film was Co75Fe25 (atomic%).

  The Al—Ox film of the tunnel barrier layer 6 is formed by first depositing a metal Al film by 1 nm by DC sputtering, and then setting the oxygen / argon flow ratio to 1: 1, the chamber gas pressure to 0.1 mTorr, and ICP (inductive coupling). The metal Al film was formed by plasma oxidation with plasma from (plasma). Although the oxidation time depends on the ICP plasma output, it was set to 30 seconds in this embodiment.

  Further, films other than the Al—Ox film of the tunnel barrier layer 6 were formed by a DC magnetron sputtering method.

Next, in a magnetic field heat treatment furnace, heat treatment is performed at 200 to 360 ° C. in a magnetic field of 10 kOe for 5 hours, and regularization heat treatment is performed on the PtMn layer that is an antiferromagnetic layer, thereby forming the ferromagnetic tunnel junction 9. did.
Subsequently, the TMR element 22 and the insulating film 26 thereunder are patterned to form the TMR element 22 having a planar pattern shown in FIG.
Further, an insulating layer 25 having a thickness of about 100 nm is formed by sputtering Al ₂ O _3, and further, the bit line BL and the terminal pad 24 are formed by photolithography, and the TEG shown in FIGS. Obtained.

<Sample 2>
A TEG was obtained in the same manner as Sample 1 except that the composition of the magnetization free layer 7 was Co70.5Fe4.5Si15B10 (atomic%) and the thickness of the magnetization free layer 7 was 4 nm.

<Sample 3>
A TEG was obtained in the same manner as Sample 1 except that the composition of the magnetization free layer 7 was Co35Ni35Fe10B20 (atomic%) and the thickness of the magnetization free layer 7 was 4 nm.

<Sample 4>
A TEG was obtained in the same manner as Sample 1 except that the composition of the magnetization free layer 7 was Co75Fe25 (atomic%) and the thickness of the magnetization free layer 7 was 2 nm.

<Sample 5>
A TEG was obtained in the same manner as Sample 1 except that the composition of the magnetization free layer 7 was Co90Fe10 (atomic%) and the thickness of the magnetization free layer 7 was 2 nm.

  And the RH curve was measured as follows with respect to the obtained TEG of each sample 1 to sample 5, and the variation in coercive force was further obtained from the RH curve.

(Measurement of RH curve)
In a normal magnetic memory device such as an MRAM, information is written by reversing the magnetization of the magnetoresistive effect element with a current magnetic field, but in this embodiment, the resistance value is measured by magnetizing the magnetoresistive effect element with an external magnetic field. went. That is, first, an external magnetic field for reversing the magnetization of the magnetization free layer of the TMR element 22 was applied so as to be parallel to the easy axis of magnetization of the magnetization free layer. The magnitude of the external magnetic field for measurement was 500 Oe.

  Next, sweeping from −500 Oe to +500 Oe as viewed from one side of the easy axis of the magnetization free layer, and at the same time, the bias voltage applied to the terminal pad 23 of the word line WL and the terminal pad 24 of the bit line BL becomes 100 mV. The tunnel current was passed through the ferromagnetic tunnel junction. The resistance value with respect to each external magnetic field at this time was measured, and the RH curve was obtained.

(Variation in coercive force Hc)
The RH curve is measured by the above measurement method, and from the RH curve, the resistance value in the state where the magnetization of the magnetization fixed layer and the magnetization free layer is antiparallel and the resistance is high, The average value with the resistance value in a state where the magnetization of the magnetization free layer is parallel and low in resistance is obtained, and the value of the external magnetic field when the resistance value of this average value is obtained is defined as the coercive force Hc. The coercive force Hc was applied to 500 similarly manufactured elements (TEG), and the standard deviation ΔHc was obtained. Then, ΔHc / (average value of Hc) was used as a value of variation in coercive force Hc.
Note that the variation in the coercive force Hc is preferably 6% or less from the viewpoint of improving the writing characteristics.

  For each of Samples 1 to 5, the composition and thickness of the magnetization free layer 7 are shown in Table 1, the heat treatment temperature is taken on the horizontal axis, the variation in coercive force Hc is taken on the vertical axis, and plotted in FIG. Show.

  As is clear from FIG. 10, as in Samples 1 to 3, the amorphous material is used for the magnetization free layer 7 and the temperature of the heat treatment in the magnetic field is set to 300 ° C. or more, thereby suppressing the variation in the coercive force Hc. You can see that

  Therefore, by using an amorphous material for the magnetization free layer 7 and performing a heat treatment in a magnetic field of 300 ° C. or higher, the effect of improving the write characteristics of the MRAM can be obtained by suppressing variation in the coercive force Hc of the TMR element. I understand that.

  In addition, when Sample 1 and Sample 3 are compared with Sample 2, Sample 2 has a higher Curie temperature and crystallization temperature, but the variation in coercive force Hc in FIG. It can be seen that sample 2 requires a slightly higher temperature.

  The magnetoresistive effect element (TMR element or the like) of the present invention is not limited to the magnetic memory device described above, but also a magnetic head, a hard disk drive equipped with the magnetic head, a magnetic sensor, an integrated circuit chip, a personal computer, and a portable terminal. The present invention can be applied to various electronic devices such as mobile phones, electronic devices, and the like.

  The present invention is not limited to the above-described embodiment, and various other configurations can be taken without departing from the gist of the present invention.

  1, 10, 22 Tunnel magnetoresistive effect element (TMR element), 2, 21 substrate, 3 underlayer, 4 antiferromagnetic layer, 5 magnetization fixed layer, 5a first magnetization fixed layer, 5b second magnetization fixed layer (Reference layer), 5c nonmagnetic conductor layer, 6 tunnel barrier layer, 7 magnetization free layer, 9 ferromagnetic tunnel junction, 11 memory cell, 23, 24 pad, 30 wafer, 32 heater, 33 magnet, WL, WL1, WL2 Word line, BL bit line

Claims (10)

A magnetoresistive element having a configuration in which a pair of ferromagnetic layers are opposed to each other through an intermediate layer, and a change in magnetoresistance is obtained by passing a current perpendicular to the film surface,
One of the ferromagnetic layers is a magnetization fixed layer, the other is a magnetization free layer,
The ferromagnetic layer has an amorphous or microcrystalline structure;
The magnetoresistive element, wherein the ferromagnetic layer is heat-treated in a magnetic field at a temperature of 300 ° C. or higher and lower than a crystallization temperature of the magnetization free layer.   The magnetoresistive element according to claim 1, wherein the magnetization free layer is made of a material selected from FeCoB, FeCoNiB, and FeCoSiB.   The magnetoresistive effect element according to claim 1, which is a tunnel magnetoresistive effect element using a tunnel barrier layer made of an insulator or a semiconductor as the intermediate layer.   The magnetoresistive effect element according to claim 1 having a laminated ferri structure. A magnetoresistive element having a configuration in which a pair of ferromagnetic layers are opposed to each other through an intermediate layer, and a magnetoresistive change is obtained by passing a current perpendicular to the film surface;
A word line and a bit line sandwiching the magnetoresistive effect element in the thickness direction;
One of the ferromagnetic layers is a magnetization fixed layer, the other is a magnetization free layer,
The ferromagnetic layer has an amorphous or microcrystalline structure;
A magnetic memory device, wherein the ferromagnetic layer is heat-treated in a magnetic field at a temperature of 300 ° C. or higher and lower than a crystallization temperature of the magnetization free layer.   6. The magnetic memory device according to claim 5, wherein the magnetization free layer is made of a material selected from FeCoB, FeCoNiB, and FeCoSiB.   6. The magnetic memory device according to claim 5, wherein the magnetoresistive effect element is a tunnel magnetoresistive effect element using a tunnel barrier layer made of an insulator or a semiconductor as the intermediate layer.   The magnetic memory device according to claim 5, wherein the magnetoresistive effect element has a laminated ferrimagnetic structure. A method of manufacturing a magnetoresistive element having a configuration in which a pair of ferromagnetic layers are opposed to each other through an intermediate layer and a change in magnetoresistance is obtained by passing a current perpendicular to the film surface,
In the magnetoresistive element, one of the ferromagnetic layers is a fixed magnetization layer, the other is a magnetization free layer, and the ferromagnetic layer has an amorphous or microcrystalline structure,
A method of manufacturing a magnetoresistive effect element, comprising performing a heat treatment in a magnetic field at a temperature of 300 ° C. or higher and lower than a crystallization temperature of the magnetization free layer after forming at least the magnetization free layer. A magnetoresistive effect element having a configuration in which a pair of ferromagnetic layers are opposed to each other through an intermediate layer and a magnetoresistive effect element is obtained by flowing a current perpendicular to the film surface, and the magnetoresistive effect element is arranged in the thickness direction. A method of manufacturing a magnetic memory device having sandwiched word lines and bit lines,
In the magnetoresistive element, one of the ferromagnetic layers is a fixed magnetization layer, the other is a magnetization free layer, and the ferromagnetic layer has an amorphous or microcrystalline structure,
A method for manufacturing a magnetic memory device, comprising performing a heat treatment in a magnetic field at least 300 ° C. and below a crystallization temperature of the magnetization free layer after forming at least the magnetization free layer.

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