JP2009295642A - Magneto-resistance effect element, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce variations in magneto-resistance effect elements. <P>SOLUTION: The magneto-resistance effect element includes: a magnetization fixed layer 1 having extension portions 1A, 1B extending along at least two directions respectively and having a plurality of magnetization facilitation axes which are different from one another along the extending directions of the respective extension portions 1A, 1B; a tunnel barrier layer 2 formed on the magnetization fixed layer 1; and a magnetization free layer 3 formed on the tunnel barrier layer 2 and having variable magnetization direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetoresistive effect element, and more particularly to the shape of a magnetization fixed layer. The present invention also relates to a method for manufacturing a magnetoresistive effect memory.

  In recent years, many semiconductor memories that store information based on a new principle have been proposed. One of them is a magnetoresistive random access memory (MRAM) using a magnetoresistive effect.

  In the MRAM, an element using a magnetic tunnel junction (hereinafter referred to as an MTJ element) is used as a memory element. One memory cell configuring the MRAM has a 1Tr + 1MTJ type configuration including, for example, one MTJ element and one MIS (Metal-Insulator-Semiconductor) transistor. A plurality of the memory cells are arranged in the memory cell array.

  In an MTJ element, an insulating film is sandwiched between two ferromagnetic layers, the magnetization direction of one ferromagnetic layer (magnetization fixed layer) is fixed, and the magnetization direction of the other ferromagnetic layer (magnetization free layer) is free. The structure that can be reversed is a basic structure. The MTJ element stores “1” or “0” data by using a magnetoresistive effect in which the resistance value changes according to the relative magnetization direction of the magnetization fixed layer and the magnetization free layer (for example, Patent Document 1). reference).

  In the spin injection MRAM, a spin injection method using magnetization reversal by polarized spin current injection is adopted as a data writing method for the MTJ element. In this method, the amount of current necessary for spin transfer magnetization reversal (reversal threshold current) is defined by the current density flowing through the MTJ element. This means that the inversion threshold current can also be scaled along with the scaling of the MTJ element, which is a factor that promotes miniaturization of the MTJ element in order to increase the storage capacity of the MRAM.

On the other hand, with the miniaturization of the MTJ element, due to the proximity effect in the manufacturing process, variations in exposure and processing become conspicuous, and the characteristics of the MTJ element vary. In an MTJ element using a crystalline magnetic material for a ferromagnetic layer, as the miniaturization progresses, the element size and the size of the crystal grain become approximately the same, and the orientation of the crystals contained in one element, Variations in device characteristics due to the shape and number are also a problem.
JP 2005-535125 A

  The present invention proposes a technique for reducing variation in characteristics of magnetoresistive elements.

  The magnetoresistive effect element according to the example of the present invention has a plurality of extending portions extending along at least two directions, and has a plurality of different easy axes along the extending direction of the extending portions. A magnetization fixed layer, a tunnel barrier layer provided on the magnetization fixed layer, and a magnetization free layer provided on the tunnel barrier layer and having a variable magnetization direction.

  A method of manufacturing a magnetoresistive effect memory according to an example of the present invention requires a step of forming a plurality of magnetoresistive effect elements on a semiconductor substrate, testing the plurality of magnetoresistive effect elements, and adjusting characteristics. A step of detecting a magnetoresistive effect element, a step of performing a substrate heating process on the semiconductor substrate after performing the test, and passing a current through the magnetoresistive effect element that requires adjustment of the characteristics. A step of applying a Joule heat generated by the current to the magnetoresistive effect element through which the current is passed, and applying a magnetic field in a state where the heat of the substrate heating process and the Joule heat are applied to the magnetoresistive effect element that requires adjustment of the characteristics. And adjusting the element characteristics by changing the magnetization direction of the magnetoresistive effect element that needs to be adjusted.

  According to the present invention, variation in characteristics of the magnetoresistive element can be reduced.

  Hereinafter, some embodiments for carrying out examples of the present invention will be described in detail with reference to the drawings.

1. Embodiment
(1) First embodiment
A first embodiment of the present invention will be described with reference to FIGS.

(A) MTJ element
The structure of the magnetoresistive effect element according to the first embodiment of the present invention will be described with reference to FIGS. The magnetoresistive effect element according to the present embodiment is an MTJ (Magnetic Tunnel Junction) element.
FIG. 1 is a perspective view of an MTJ element according to this embodiment. 2 illustrates a planar structure of the MTJ element illustrated in FIG. 1, and FIG. 3 illustrates a cross-sectional structure along the first direction of FIG.

  As shown in FIGS. 1 to 3, the MTJ element according to this embodiment includes a magnetization fixed layer 1, a tunnel barrier layer 2 provided on the magnetization fixed layer 1, and a magnetization provided on the tunnel barrier layer 2. It is composed of a free layer 3. That is, the magnetization free layer 3 is laminated on the magnetization fixed layer 1 in the third direction via the tunnel barrier layer 2. The MTJ element may further include an exchange bias layer, and the pinned magnetization layer 1 may be sandwiched between the exchange bias layer and the tunnel barrier layer 2.

  1 to 3, for example, the lower electrode 7 is connected to the magnetization fixed layer 1, and the upper electrode 8 is connected to the magnetization free layer 3.

  The magnetization fixed layer 1 and the magnetization free layer 3 are formed using, for example, a crystalline magnetic material. For the magnetization fixed layer 1 and the magnetization free layer 3, for example, a ferromagnetic metal containing at least one of atoms such as cobalt (Co), iron (Fe), nickel (Ni), ruthenium (Ru) is used. . Further, boron (B) added to these ferromagnetic metals may be used.

  The tunnel barrier layer 2 is made of an insulator such as magnesium oxide (MgO) or aluminum oxide (AlOx) (x is a natural number), or a paramagnetic metal such as gold (Au), silver (Ag), or copper (Cu). It is done.

  In the MTJ element according to the first embodiment of the present invention, the planar shape of the magnetization fixed layer 1 has a plurality of extending portions 1A and 1B extending in different directions, and the extension The magnetic anisotropy is provided in a plurality of easy axis directions along the extending direction of the portion. In the example shown in FIGS. 1 to 3, the magnetization fixed layer 1 has two extending portions, and the extending portions extend in two different directions (first and second directions), respectively. Is shown. This is for simplification of explanation, and the magnetization fixed layer 1 may have extending portions extending in three or more directions, respectively, and each extending direction may have an easy magnetization axis direction. Of course.

  The magnetization pinned layer 1 having a planar shape as shown in FIGS. 1 to 3 has shape magnetic anisotropy, and the first direction in which the first extending portion 1A extends becomes the first easy magnetization axis direction, and the second The second direction in which the extending part 1B extends is the second easy axis direction.

  On the other hand, the magnetization free layer 3 has an elliptical shape, for example. The magnetization free layer 3 is laminated on the magnetization fixed layer 1 via the tunnel barrier layer 2 so that the major axis direction is along the first direction and the minor axis direction is along the direction perpendicular to the first direction. Yes. In such a magnetic layer having an elliptical shape, the long axis direction is the easy magnetization axis direction, and the short axis direction is the hard magnetization axis, so the easy magnetization axis direction of the magnetization free layer 3 is the first direction. The size of the magnetization free layer 3 is formed to be smaller than the size of the magnetization fixed layer 1.

  When the magnetization fixed layer 1 and the magnetization free layer 3 are formed using, for example, a crystalline magnetic material, with the miniaturization of the element, the orientation of crystals contained in the element, the difference in the shape and number of crystal grains, and the like Therefore, the magnetization directions of the layers 1 and 3 tend to vary.

  Since the resistance value of the MTJ element is determined by the relative magnetization directions of the magnetization fixed layer 1 and the magnetization free layer 3, the variation in the magnetization direction causes variation in the characteristics of each element.

  In the present embodiment, the magnetization fixed layer 1 of the MTJ element has a plurality of shape magnetic anisotropies in the easy axis directions, so that the magnetization direction of the magnetization fixed layer 1 is selected from the plurality of easy axes. It can be a direction along one easy magnetization axis.

  Therefore, the resistance value of the MTJ element determined by the relative magnetization direction between the magnetization fixed layer 1 and the magnetization free layer 3 is within a predetermined range, or the MR ratio of the MTJ element is a predetermined value. For example, the magnetization direction of the magnetization fixed layer 1 can be changed by applying an external magnetic field. That is, the characteristics of the MTJ element can be adjusted so that the characteristics are within a predetermined range.

  As described above, in this embodiment, variations in element characteristics due to variations in crystals included in the magnetization fixed layer or the magnetization free layer are given to the magnetization fixed layer with shape magnetic anisotropy so that the magnetization direction can be changed. This can be solved.

  Therefore, according to the first embodiment of the present invention, variation in element characteristics of a plurality of MTJ elements used in the MRAM can be reduced.

(B) Manufacturing method
As a method for manufacturing the MRAM (magnetoresistance effect memory) according to the first embodiment of the present invention, an element characteristic adjusting method for the MTJ element will be described with reference to FIGS.

  FIG. 4 illustrates each step of the method for adjusting the element characteristics of the MTJ element constituting the MRAM, specifically, the method for adjusting the magnetization direction of the magnetization fixed layer of the MTJ element. FIG. 5 schematically shows the cross-sectional structure of the memory cell array region of the MRAM according to the present embodiment, and FIG. 5 also shows the planar shape and magnetization direction of the magnetization fixed layer of each MTJ element. Yes. In FIG. 5, the interlayer insulating film formed on the semiconductor substrate is not shown for the sake of simplicity. In FIG. 5, the same members as those in FIGS. 1 to 3 are denoted by the same reference numerals, and detailed description will be given as necessary.

  First, an MRAM configured as shown in FIG. 5 is formed on a semiconductor substrate by using a thin film deposition technique such as a CVD (Chemical Vapor Deposition) method or a sputtering method, a photolithography technique, a RIE (Reactive Ion Etching) method, or the like. (ST1).

  In the example shown in FIG. 5, each of the memory cells MC1 to MC4 included in the MRAM includes, for example, one MTJ element MTJ1 to MTJ4 and one MIS transistor Tr1 to Tr4 that functions as a selection switch element for the MTJ element. (Hereinafter referred to as a select transistor), so-called 1Tr + 1MTJ. A plurality of word lines and a plurality of bit lines are formed so as to be connected to the plurality of memory cells MC1 to MC4, respectively. The specific formation order of the MRAM having this configuration is as follows.

  Since the first to fourth selection transistors Tr1 to Tr4 have substantially the same configuration, the structure and formation method thereof will be described below by taking the first selection transistor Tr1 as an example. Since the first to fourth MTJ elements MTJ1 to MTJ4 have substantially the same configuration, the structure and formation method thereof will be described below using the first MTJ element MTJ1 as an example.

  First, the element isolation insulating film 15 is formed in the semiconductor substrate 10, and one island-shaped active region surrounded by the element isolation insulating film 15 is formed. In one active region, the first memory cell MC1 including the first MTJ element MTJ1 and the first selection transistor Tr1, and the second memory including the second MTJ element MTJ2 and the second selection transistor Tr2 are included. A cell MC2 is formed. Similarly, the third and fourth memory cells MC3 and MC4 are formed in one island-like active region.

Gate electrode 12 ₁ of the first selection transistor Tr1 is formed on the gate insulating film 11 ₁ on the semiconductor substrate 10. Gate electrode 12 ₁ of the selection transistor Tr1 is, for example, a word line. Then, a gate electrode 12 ₁ of the formed selection transistor Tr1 as a mask, a diffusion layer serving as the source / drain regions (hereinafter, referred to as a source / drain diffusion _layer) 13 1, 13 _3, for example, by ion implantation And formed in the semiconductor substrate 1. Thus, a selection transistor that functions as a selection switch element is formed for the MTJ element.

On the source / drain diffusion layers ₁₃ 1, 13 _3, and the lower electrode ₇₁ and the contact C1 of the MTJ element is formed, respectively. The source / drain diffusion layer 13 ₃ contact C1 is connected is shared with the source / drain diffusion layer of the second selection transistor Tr2, a common node of the two memory cells MC1, MC2.

The first MTJ element MTJ1 is formed so as to be located on _one source / drain diffusion layer 131 of the first selection transistor Tr1. First MTJ element MTJ1, the so magnetization fixed layer _{1 1} is connected to one source / drain diffusion layer 13 ₁ of the select transistors Tr1 through the lower electrode _71, the magnetization fixed layer _{1 1,} a tunnel barrier layer 2 ₁ and the magnetization free layer 3 ₁ are sequentially stacked, is formed.

In this case, the magnetization fixed layer 1 ₁ is to have two extending portions which each extend in a first direction and a second direction, are formed by patterning. Thus, the magnetization fixed layer 1 ₁ has a shape magnetic anisotropy, having an axis of easy magnetization in the extending direction of the extending portion (first and second directions).
Further, the magnetization free layer 3 ₁ is, for example, such that an elliptical shape is formed by patterning. Magnetization free layer 3 ₁ of the elliptical shape is formed such that the first direction becomes the long axis. Further, the magnetization free layer 3 ₁ is formed in a size smaller than the magnetization fixed layer 1 _1.

The magnetization fixed layer _{1 1} and the magnetization free layer _{3 1,} for example, Co, Fe, Ni, the crystallinity of magnetic material such as Ru is used. In FIG. 5, the magnetization extending portion of the fixed layer 1 ₁ to 1 ₄ extends in two directions, but provided with three or more extending portion extending in different directions, respectively, three or more It may be an MTJ element having an easy magnetization axis.

  A set of bit line pairs BL1 and BL2 connected to the memory cell includes a first bit line BL1 and a second bit line BL2 located on the semiconductor substrate 10 side with respect to the first bit line BL1. Yes. In FIG. 5, the second bit line BL2 is indicated by a broken line because it is formed in the front direction or the depth direction with respect to the cross section in FIG. 5.

The second bit line BL2 is connected to the shared node (source / drain diffusion layer 13 ₃ ) of the two selection transistors Tr1 and Tr2 via the via V1, the intermediate wiring layer M1, and the contact C1.

The first bit line BL1 is formed above the second bit line BL2, through the upper electrode ₈₁ is connected to the magnetization free layer _{3 1} of the MTJ element MTJ1.

Second to fourth MTJ elements MTJ2～MTJ4, the second to fourth select transistors Tr1~Tr4 also in the first MTJ element MTJ1 and the first selection transistor Tr1 ₁ respectively simultaneously process, on the semiconductor substrate 1 It is formed.

  In addition, a control circuit for controlling the memory cell is formed in the peripheral circuit region adjacent to the memory cell array region in substantially the same process as the formation of the memory cell.

  The manufactured MRAM is, for example, a spin injection MRAM. That is, during the write operation, “0” or “1” data is written to the MTJ elements MTJ1 to MTJ4 by changing the direction of the write current flowing through the MTJ elements MTJ1 to MTJ4. During the read operation, “0” or “1” data is discriminated based on the resistance values of the MTJ elements MTJ1 to MTJ4.

  Next, a test process is performed on the manufactured MRAM, and the characteristics of the MTJ elements MTJ1 to MTJ4 are examined (ST2). In this test process, for example, resistance values corresponding to “0” or “1” data of each formed MTJ element are inspected, and whether the resistance values are within a predetermined range centered on the reference value. It is investigated whether or not.

  An MTJ element whose resistance value does not fall within a predetermined range is detected as an MTJ element that requires adjustment of element characteristics. Hereinafter, an MTJ element that requires characteristic adjustment is referred to as an adjusted MTJ element. With respect to this adjusted MTJ element, the element characteristics are adjusted in the following steps so that the resistance value falls within a predetermined range. In the present embodiment, the element characteristics are adjusted by changing the magnetization direction of the magnetization fixed layer.

  First, heat treatment is performed on the semiconductor substrate on which the MRAM is manufactured, and heat is applied to the MTJ element (ST3). Subsequently, a current is supplied to the adjusted MTJ element (ST4). Hereinafter, a specific description will be given of a method for adjusting element characteristics using the second MTJ element MTJ2 shown in FIG. 5 as an adjustment MTJ element. In FIG. 5, the current that flows through the adjustment MTJ element MTJ2 is indicated by a white arrow.

As shown in FIG. 5, the second MTJ element MTJ2, due to the orientation or crystal grains in the form of crystals magnetization fixed layer 1 ₂ includes a resistance value of the element is within the range of predetermined resistance value The second MTJ element MTJ2 is detected as an adjusted MTJ element by the test process (ST2).

After the heat treatment (ST3) is performed on the semiconductor substrate 10, the potential of the word line (gate electrode 12 ₂ ) to which the second selection transistor Tr2 is connected is set to a high potential, and the selection transistor Tr2 is turned on. The state becomes “ON”.
On the other hand, since the resistance values of the other MTJ elements MTJ1, MTJ3, and MTJ4 are within a predetermined range, it is not necessary to adjust the magnetization direction. The select transistors Tr1, Tr3, Tr4 that constitute the memory cell together with the MTJ elements MTJ1, MTJ3, MTJ4 are set to the OFF state “OFF” by setting the word line to which they are connected to a low potential. .

After the selection transistor Tr2 to which the adjustment MTJ element MTJ2 is connected is turned on, the current I flows through the adjustment MTJ element MTJ2. In Figure 5, the current I, via a current path of the select transistor Tr2 (channel), flows from the magnetization fixed layer _{1 2} of the MTJ element MTJ2 to the magnetization free layer _{3 2.} In this case, the second bit line BL2 is set to a high potential, and the first bit line BL1 is set to a low potential.

By current I flows through the adjustment MTJ element MTJ2, the magnetization fixed layer _{1 second} adjustment MTJ element MTJ2 is heated by Joule heat due to the current I. Therefore, the adjustment MTJ element MTJ2 is given a heat quantity by the substrate heating and a heat quantity by the Joule heat of the current I. In contrast, the MTJ elements MTJ1, MTJ3, and MTJ4 that do not require adjustment of the magnetization direction are given only the amount of heat due to substrate heating.

Usually, the coercive force of a magnetic material tends to decrease with increasing temperature. In the present embodiment, since the current I flows only through the adjustment MTJ element MTJ2, the amount of heat applied to the adjustment MTJ element is sufficiently larger than the amount of heat applied to the MTJ elements MTJ1, MTJ3, and MTJ4 that do not require adjustment. Thus, the coercivity of the magnetization fixed layer _{1 second} adjustment MTJ element MTJ2, the other MTJ elements MTJ1, MTJ3, magnetization fixed layer ₁ 1 of _MTJ4, 1 3, than _{1 4} coercivity is reduced, the magnetization fixed layer only 1 ₂ magnetization direction can selectively change.
In this way, only the magnetization direction of the adjustment MTJ element MTJ2 can be adjusted by selectively applying to the MTJ element that needs adjustment the amount of heat that makes the magnetization direction of the magnetization fixed layer variable by the substrate heating and current application. become.

The heating temperature by substrate heating is preferably a temperature at which the coercivity of the magnetization fixed layer of the MTJ element that does not require adjustment of the magnetization direction is sufficiently maintained. In view of such a substrate heating temperature, the current value and energization time of the current I are set so that the magnetization direction of the magnetization fixed layer is variable depending on the value of the current injected into the adjusted MTJ element and the energization time thereof. It is preferable. Further, the substrate heating temperature is preferably lower than a temperature (for example, 400 ° C. to 500 ° C.) at which deterioration of element characteristics such as mutual diffusion of a magnetic material and a tunnel barrier material constituting the MTJ element occurs.
Incidentally, MTJ elements MTJ1~MTJ4 shown in FIG. 5, the magnetization fixed layer ₁ 1 to 1 ₄ are provided on the semiconductor substrate side, the magnetization free layer has a configuration provided on the bit line side. In this case, to provide efficient Joule heat generated by the current to the magnetization fixed layer 1 ₁ to 1 _4, it is preferable to flow the current I from the semiconductor substrate 10 side (bit line BL2 side) to the bit line BL1 side. To the contrary, when the magnetization pinned layer 1 ₁ to 1 ₄ becomes a structure which is provided on the bit line side is preferably flowed from the bit line BL1 side to the semiconductor substrate 10 side (bit line BL2 side).

  Subsequently, an external magnetic field is applied to the semiconductor substrate 10 (MRAM chip) in a state where heat from the substrate heating process and Joule heat by energization are applied to the adjusted MTJ element MTJ2 (ST5). For example, the external magnetic field is applied along the second direction (second easy magnetization axis direction).

As described above, the adjustment MTJ element MTJ2 is the coercive force of the magnetization fixed layer 1 ₂ is applied is sufficiently weaker heat, the magnetization direction of the magnetization fixed layer is adjusted in a direction that matches with the first direction . On the other hand, the other MTJ elements MTJ1, MTJ3, and MTJ4 are not affected by the external magnetic field. This is because the amount of heat given to the MTJ elements MTJ1, MTJ3, MTJ4 does not reach the amount of heat that can change the magnetization direction of the magnetization fixed layer, and has sufficient coercive force with respect to the external magnetic field. .

By application of an external magnetic field along the second direction, the magnetization direction of the magnetization fixed layer 1 _second adjustment MTJ element MTJ2 is changed from a first direction of axis of easy magnetization in the second magnetic easy axis.

After the magnetization direction of the magnetization fixed layer 1 ₂ is in a direction that coincides with the second easy axis direction, the supply voltage for the bit line pairs BL1, BL2 and the word line is stopped. Since the injection of current into the adjusted MTJ element MTJ2 is stopped, Joule heat due to the current does not occur. At the same time, the substrate heating process for the semiconductor substrate 10 is also stopped.
Therefore, since the amount of heat which has been added to adjust the MTJ element MTJMTJ2 is eliminated, the coercivity of the magnetization fixed layer 1 ₂ returns to the original state, the magnetization direction of the magnetization fixed layer 1 ₂ and the second direction (second axis of easy magnetization Direction). Thereafter, the application of the external magnetic field is stopped. The order of stopping the energization of the adjustment MTJ element and stopping the substrate heating process is not limited to the above order, and the order can be changed as appropriate.
As described above, the MTJ element whose magnetization direction is adjusted can obtain a predetermined resistance value.

  Thereafter, a magnetic shield is formed on the semiconductor substrate (MRAM chip) on which the MRAM is formed, and a packaging process for the MRAM is executed (ST6). As a result, the MRAM is not affected by the external magnetic field.

In the above-described process, the external magnetic field is applied so that the magnetization direction of the magnetization fixed layer of the adjustment MTJ element is changed from the first direction to the second direction. However, the invention is not limited to this, and the element characteristics are within a predetermined range. In this case, the device characteristics may be adjusted by applying an external magnetic field along the first direction so as to change from the second direction to the first direction.
In addition, the above-described method for adjusting the element characteristics of the MTJ element adjusts the magnetization direction of an element whose characteristics have deteriorated, such as a resistance value corresponding to “0” or “1” being small compared to other elements. It is not limited to performing. In other words, due to the crystallinity of the magnetization fixed layer and the magnetization free layer, even for MTJ elements whose characteristics are too good, such as elements whose element characteristics are too high compared to other elements and elements whose reversal current density is too low. The magnetization direction of the magnetization fixed layer is selectively adjusted so that the magnetization easy axis direction (second direction) changes from the first magnetization easy axis direction (first direction), for example. It is also possible to prevent the element and characteristics from varying.

  The MRAM according to the embodiment of the present invention is completed through the above steps.

  FIG. 6 shows the frequency with respect to the resistance value of the MTJ element before and after adjusting the magnetization direction of the magnetization fixed layer by the MRAM manufacturing method of the present embodiment shown in FIG.

  As shown in FIG. 6, the MTJ element whose magnetization direction has been adjusted is based on the resistance value having the highest frequency in each of the resistance value corresponding to “0” data and the resistance value corresponding to “1” data. The distribution range of the resistance value as a value is narrower than that of the MTJ element before the magnetization direction is adjusted. That is, variation in characteristics of a plurality of MTJ elements included in the MRAM is reduced.

  In this way, the magnetization direction of the magnetization fixed layer is changed stepwise so that the resistance value of the MTJ element falls within a predetermined range due to the magnetization fixed layer having magnetic anisotropy on a plurality of easy axes. be able to.

  Moreover, although the element characteristic adjustment method of the MTJ element described in the present embodiment has been described for the case where the magnetization direction is adjusted with respect to one adjustment MTJ element, a plurality of adjustments are performed using an external magnetic field having the same magnetization direction. The magnetization characteristics can be adjusted simultaneously by appropriately selecting the word line and bit line pair for the MTJ element. That is, in this embodiment, the manufacturing period of the MRAM can be shortened.

  As described above, according to the first embodiment of the present invention, variations in element characteristics of a plurality of MTJ elements used in an MRAM can be reduced.

(2) Second embodiment
A second embodiment of the present invention will be described with reference to FIG. In addition, about the same member as 1st Embodiment, the same code | symbol is attached | subjected and detailed description is performed as needed.

  The second embodiment of the present invention is characterized in that, in addition to the configuration of the first embodiment, write word lines WWL1 to WWL4 are provided in the plurality of memory cells MC1 to MC4, respectively.

Hereinafter, the first memory cell MC1 will be described as an example. On the magnetization free layer _{3 1} of the first MTJ element MTJ1 is the upper electrode ₈₁ is formed, whereby one end of the MTJ element MTJ1 is connected to the first bit line BL1.

The magnetization fixed layer 11 of the _first MTJ element MTJ1 is formed on the intermediate wiring layer M3. Further, on the source / drain diffusion layer 13 ₁ of the first selection transistor Tr1, contact C2 functions as MTJ elements MTJ1 lower electrode, the intermediate wiring layers M2 and vias _{9 1} is provided, through them, the first magnetization pinned layer _{1 1} of the MTJ elements MTJ1 between the source / drain diffusion layer 13 ₁ of the first selection transistor Tr1 is connected.

  The first write word line WWL1 is provided below the first MTJ element MTJ1. The write word line WWL1 extends, for example, in the same direction as the word line. By supplying a current to the write word line WWL1 from the near side to the depth side of the drawing or from the depth side to the near side, a magnetic field is generated in the memory cell MC1 including the write word line WWL1.

Thus, when equipped with the write word line WWL1～WWL4, by supplying a current to the write word line WWL1～WWL4 selected, the magnetic field for the magnetization direction of the adjustment magnetization fixed layer _{1 1,} the MTJ element Can be applied individually.

That is, according to the present embodiment, a magnetic field can be applied only to the adjustment MTJ element (for example, the second MTJ element MTJ2) by selectively passing a current through the write word line. Therefore, it is possible to eliminate the influence of the magnetic field on the MTJ element that does not require adjustment.
Therefore, according to the second embodiment of the present invention, variation in element characteristics of a plurality of MTJ elements used in the MRAM can be reduced, and the write word lines WWL1 to WWL4 are provided for each memory cell. The magnetization direction can be adjusted with high accuracy.

(3) Third embodiment
A third embodiment of the present invention will be described with reference to FIG. In addition, about the same member as 1st and 2nd embodiment, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted. 8, along with showing a sectional structure taken along the extending direction of the bit lines, illustrates the magnetization plane structure of the fixed layer ₅ 1-5 ₄ for each MTJ element MTJa～MTJd.

  The element characteristic adjusting method (manufacturing method) of the MTJ element described in the first embodiment is applied only to an MTJ element having shape magnetic anisotropy in a plurality of easy axis directions as shown in FIGS. However, the present invention can be used for MTJ elements having other structures.

For example, as in the example shown in FIG. 8, the element characteristics can be adjusted even for the MTJ element in which the exchange bias layers 4 ₁ to 4 ₄ are provided below the magnetization fixed layers 5 _{1 to} 5 ₄ . Hereinafter, the structure of the MTJ elements MTJa to MTJd shown in FIG. 8 will be described. Since the MTJ elements MTJa to MTJd have the same configuration, the structure thereof will be described below using the first MTJ element MTJa as an example.

In the MTJ element MTJa, the magnetization fixed layer _{5 1} is provided on the exchange bias layer _{4 1.} Magnetization free layer 3 _1, through the tunnel barrier layer 2 ₁ is provided on the magnetization fixed layer 5 _1.
As shown in FIG. 8, the planar shape of the magnetization fixed layer _{5 first} MTJ element MTJa~MTJd in this embodiment has an elliptical shape. In the case of this shape, the major axis direction of the ellipse is the easy magnetization axis direction, and the minor axis direction of the ellipse is the hard magnetization axis.

The planar shape of the magnetization free layer 3 ₁ is, for example, an elliptical shape, as the major axis of the ellipse becomes long axis of the magnetization fixed layer 5 ₁ (easy magnetization axis direction) in the same direction, the magnetization fixed It is stacked over the layer 5 _1. Further, the dimensions of the magnetization free layer 3 _1, for example, is formed to be smaller than the size of the magnetization fixed layer 5 _1.

Magnetization fixed layer _{5 1} and the magnetization free layer _{3 1} is, for example, a crystalline-based magnetic material, Co, Fe, Ni, Ru, is a ferromagnetic metal comprising either used.

Exchange biasing layer _{4 1} comprises an antiferromagnetic material, e.g., Fe-Mn, Pt-Mn , Pt-Cr-Mn, Ni-Mn, Ir-Mn, NiO, of such _Fe 2 _{O 3,} or 1 One is used.

Tunnel barrier layer _{2 1} is, for example, MgO, AlOx (x is a natural number) of an insulating material such as, or, Au, Ag, or paramagnetic metal such as Cu is used.

In the MTJ element MTJa configured as above, the magnetization direction of the magnetization fixed layer 5 ₁ is fixed by the exchange bias that occurs between the exchange bias layer 4 ₁ and the magnetization fixed layer 5 _1.
Exchange bias, the temperature of the exchange bias layer 4 ₁ is known to be lost and become more blocking temperature Tb. In addition, when a magnetic field is applied to the magnetization fixed layer 51 in the disappearance state of the exchange bias and cooled to the blocking temperature Tb or less during the magnetization application, the magnetization direction of the magnetization fixed layer 51 is fixed in the direction of the applied magnetic field. Is also known.
By utilizing this principle, even in the MTJ element MTJa comprising an exchange bias layer 4 ₁ as in this embodiment, it is possible to adjust the direction of magnetization of the magnetization fixed layer 5 _1.

  That is, the magnetization direction of the magnetization fixed layer of the MTJ element can be adjusted by a process substantially similar to the process shown in FIG. The method for adjusting the element characteristics of the MTJ element in the present embodiment is specifically as follows.

  First, similarly to the process shown in FIG. 4, a magnetic layer, a conductive layer, and an insulating layer are deposited using a CVD method, a sputtering method, and the like, and a deposited layer is formed using a photolithography technique and an RIE method. Processed. Through this step (ST1), the MRAM having the structure shown in FIG. Then, a test process is performed on the manufactured MRAM, and the element characteristic (resistance value) of the MTJ element is examined. As a result, an MTJ element (adjusted MTJ element) that requires adjustment of element characteristics is detected (ST2).

After the test process, a substrate heating process is performed on the semiconductor substrate on which the MRAM is manufactured (ST3). The substrate heat treatment, using a heating temperature lower than the blocking temperature of the exchange bias layer ₄₁ to _4, is performed.

Subsequently, in order to pass a current I through the adjustment MTJ element (for example, the second MTJ element MTJb) during the substrate heat treatment, a bit line pair and a word line connected to the memory cell MC2 including the adjustment MTJ element MTJb Is controlled. As a result, the selection transistor Tr2 constituting the memory cell MC2 is turned on, and the current I flows through the adjustment MTJ element MTJb (ST4). By current I flows through the adjustment MTJ element MTJb, Joule heat is generated in the exchange bias layer _{4 2.} Values and energization time of the current I, the sum of the amount of heat by heat treatment and its Joule heat, the temperature of the exchange bias layer 4 ₂ so that the above blocking temperature is set, respectively. The blocking temperature is determined depending on the materials used for the exchange bias layer and the magnetization fixed layer (ferromagnetic layer). Also in this embodiment, the amount of heat applied to the adjusted MTJ element is a temperature lower than the deterioration temperature of the element.

The adjusted MTJ element MTJb is given a heat amount equal to or higher than the blocking temperature by the heat amount by the heat treatment and the heat amount by Joule heat caused by the current I. Thus, the exchange bias acting on between the exchange bias layer 4 ₂ and the magnetization fixed layer 5 ₂ disappears, the magnetization fixing force of the magnetization fixed layer 5 ₂ is reduced. On the other hand, no current is passed to the MTJ elements MTJa, MTJc, and MTJd that do not require adjustment. Therefore, these MTJ elements MTJa, MTJc, and MTJd are only given heat by substrate heating, and are not given Joule heat by current I. Therefore, since the temperature of the exchange bias layers 4 ₁ , 4 ₃ , and 4 ₄ of the MTJ elements MTJa, MTJc, and MTJd that do not require adjustment is lower than the blocking temperature, the magnetization fixed layers 5 ₁ , 5 ₃ , and 5 ₄ and the exchange bias layer The exchange bias acting between 4 ₁ , 4 ₃ and 4 ₄ is not lost. Therefore, the magnetization pinning force of the magnetization pinned layers 5 ₁ , 5 ₃ , 5 ₄ is higher than the magnetization pinning force of the magnetization pinned layer of the adjustment MTJ element MTJb.

Subsequently, an external magnetic field is applied to the fabricated MRAM while the substrate heating process and the energized state of the adjusted MTJ element are maintained (ST5). The magnetization direction of the external magnetic field is, for example, the easy axis direction of the MTJ element.
The magnetization fixed layer 5 _second adjustment MTJ element MTJb, since magnetization fixing force by the exchange bias is reduced, the magnetization direction of the magnetization fixed layer 5 ₂ inclined to the hard magnetization axis direction, coincides with the magnetization direction of the external magnetic field Direction, that is, the direction of the easy axis of magnetization. On the other hand, the exchange bias of the MTJ elements MTJa, MTJc, and MTJd that do not require adjustment is not lost, and the magnetization pinned force of the magnetization fixed layers 5 ₁ , 5 ₃ , and 5 ₄ is sufficiently large. Therefore, the MTJ elements MTJa, MTJc, and MTJd that do not require adjustment are not affected by the external magnetic field, and the magnetization directions of the magnetization fixed layers 5 ₁ , 5 ₃ , and 5 ₄ do not change.

Then, for example, while applying an external magnetic field, heat treatment and energizing the adjustment MTJ element MTJb to the semiconductor substrate 10 is completed, the exchange bias layer 4 ₂ of adjustment MTJ element is cooled. Then, the exchange bias between the exchange bias layer 4 ₂ and the magnetization fixed layer 5 ₂ is restored, the magnetization direction of the magnetization fixed layer 5 _second adjustment MTJ element MTJb the magnetic field direction (magnetization easy axis direction) of the external magnetic field It is fixed to. Thereafter, application of the external magnetic field is terminated.

  Through the above steps, the magnetization direction of the adjusted MTJ element MTJb is adjusted, and the element characteristics (for example, resistance value) of the MTJ element MTJb fall within a predetermined range.

In the present embodiment, the magnetization direction of the magnetization fixed layer 5 _second adjustment MTJ element MTJb is, to match the magnetization easy axis, and applying an external magnetic field. However, not limited thereto, as long as the device characteristic of the adjustment MTJ element in order to fit in a predetermined range, the magnetization direction of the magnetization fixed layer 5 _2, the direction of the external magnetic field that changes from the direction of the easy magnetization axis to the direction of hard magnetization May be applied.

In this embodiment, similarly to the second embodiment, a write word line is further provided in each of the memory cells MC1 to MC4, and a magnetic field is generated by passing a current through the write word line. , may be adjusted magnetization direction of the magnetization fixed layer ₅ 1-5 _4.

  Further, the MTJ elements MTJa to MTJd of the present embodiment have a structure having an elliptical planar shape, but are not limited thereto, but are square, rectangular, elliptical, circular, hexagonal, diamond-shaped, parallel. It may be a quadrilateral shape, a cross shape, a bean shape (concave shape), or the like. Of course, an MTJ element having such a planar shape can achieve the same effect.

  As described above, also in the third embodiment of the present invention, it is possible to reduce variations in element characteristics of a plurality of MTJ elements used in the MRAM, as in the first embodiment.

2. Other
According to each embodiment of the present invention, variations in element characteristics of magnetoresistive elements (MTJ elements) can be reduced.

  The example of the present invention is not limited to the above-described embodiment, and can be embodied by modifying each component without departing from the gist thereof. Various inventions can be configured by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments. For example, some constituent elements may be deleted from all the constituent elements disclosed in the above-described embodiments, or constituent elements of different embodiments may be appropriately combined.

The perspective view which shows the structure of the magnetoresistive effect element which concerns on the 1st Embodiment of this invention. The top view which shows the structure of the magnetoresistive effect element which concerns on the 1st Embodiment of this invention. 1 is a cross-sectional view showing a structure of a magnetoresistive effect element according to a first embodiment of the present invention. FIG. 3 is a step diagram illustrating a method for adjusting element characteristics of the MRAM according to the first embodiment of the present invention. 1 is a diagram schematically showing the structure of an MRAM according to a first embodiment of the present invention. The figure for demonstrating the effect of the 1st Embodiment of this invention. The schematic diagram for showing the structure of MRAM for demonstrating the 2nd Embodiment of this invention. The schematic diagram for showing the structure of MRAM for demonstrating the 3rd Embodiment of this invention.

Explanation of symbols

1, 1 ₁ to 1 ₄ : magnetization fixed layer, 2, 2 ₁ to 2 ₄ :: tunnel barrier layer, 3, 3 _{1 to} 3 ₄ : magnetization free layer, 4 ₁ to 4 ₄ : exchange bias layer (antiferromagnetic) Layer), 5 _{1 to} 5 ₄ : magnetization fixed layer, 7, 7 _{1 to} 7 ₄ : lower electrode, 8, 8 ₁ to 8 ₄ : upper electrode, 10: semiconductor substrate, 11 _{1 to} 11 ₄ : gate insulating film, 12 _{1 to} 12 ₄ : gate electrode (word line), 13 _{1 to} 13 ₆ : source / drain diffusion layer, 15: element isolation insulating film, MTJ1 to MTJ4: MTJ element, Tr1 to Tr4: selection transistor, BL1, BL2: Bit lines, WWL1 to WWL4: write word lines, C1: contacts, V1: vias, M1 to M3: intermediate wiring layers.

Claims (5)

A magnetization pinned layer having a plurality of extending portions extending respectively along at least two directions and having a plurality of different easy axes along the extending direction of the extending portions;
A tunnel barrier layer provided on the magnetization fixed layer;
A magnetization free layer provided on the tunnel barrier layer and having a variable magnetization direction;
A magnetoresistive effect element comprising: Forming a plurality of magnetoresistive elements on a semiconductor substrate;
Testing the plurality of magnetoresistive elements and detecting magnetoresistive elements that require characteristic adjustment; and
Performing the substrate heat treatment on the semiconductor substrate after performing the test;
Applying a current to the magnetoresistive effect element that requires adjustment of the characteristics, and providing Joule heat generated by the current to the magnetoresistive effect element that has passed the current;
A magnetic field is applied to the magnetoresistive effect element that needs to be adjusted for characteristics, and the magnetization direction of the magnetoresistive effect element that needs to be adjusted is changed by applying a magnetic field in a state where the heat from the substrate heating process and the Joule heat are applied. Adjusting the element characteristics,
A method of manufacturing a magnetoresistive effect memory. The magnetoresistive effect element formed on the semiconductor substrate is the magnetoresistive memory element according to claim 1,
3. The magnetoresistive effect memory according to claim 2, wherein the magnetization direction of the magnetization fixed layer is changed to any one of a plurality of easy axis directions of the magnetization fixed layer by the magnetic field. Manufacturing method. The magnetoresistive effect element formed on the semiconductor substrate includes an exchange bias layer, a magnetization fixed layer formed on the exchange bias layer, a tunnel barrier layer formed on the magnetization fixed layer, and the tunnel barrier. A magnetoresistive element having a magnetization free layer formed on the layer,
The heating temperature of the substrate heat treatment is lower than the blocking temperature of the exchange bias layer,
The exchange bias layer of the magnetoresistive element that requires adjustment of the characteristics is subjected to a heat amount equal to or higher than a blocking temperature by the Joule heat and the heat of the substrate heating process.
The method of manufacturing a magnetoresistive memory according to claim 2.   5. The method of manufacturing a magnetoresistive effect memory according to claim 2, wherein the magnetic field is generated by a write word line formed on the semiconductor substrate.

Images