JP2003168834A - Magnetoresistive element, method of manufacturing the same, and magnetic memory device - Google Patents

Abstract

(57) [PROBLEMS] To provide a magnetoresistive effect type memory element with good characteristics even in a multilayer film structure. SOLUTION: In a magnetoresistive element having a multilayer structure including two ferromagnetic layers 14c and 16 and a non-magnetic layer 15 interposed therebetween, at least one of the ferromagnetic layers 14c and 16 is provided. Is made of a material containing an element exhibiting ferromagnetism and boron. Then, the nonmagnetic layer 15
Is composed of an oxide film, and even if oxygen is diffused from the nonmagnetic layer 15, the oxygen is preferentially bonded to boron to prevent the magnetic properties of the ferromagnetic element from being impaired.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a so-called MR (Ma
The present invention relates to a magnetoresistive effect element that produces a gnetoResistive effect, a method of manufacturing the same, and a magnetic memory device configured as a memory device that stores information using the magnetoresistive effect element.

[0002]

2. Description of the Related Art In recent years, MRAM (Magnetic Random Random) has been used as one of magnetic memory devices functioning as memory devices.
m Access Memory) is attracting attention. MRAM is a giant magnetoresistive effect (Giant MagnetoResistive; GMR) type or a tunnel magnetoresistive effect (Tunnel MagnetoResistiv).
e; TMR) type magnetoresistive effect element is used, and information is stored by utilizing the reversal of the magnetization direction in the magnetoresistive effect element.

If the magnetoresistive effect element used in the MRAM is, for example, of the TMR type, a free layer made of a ferromagnetic material, a non-magnetic material layer made of an insulator, and a fixed layer made of a ferromagnetic material, An antiferromagnetic layer for directly or indirectly fixing the magnetization direction of the fixed layer is sequentially stacked, and the resistance value of the tunnel current is changed depending on the magnetization direction of the free layer. This allows MR
In the AM, it is possible to store information such as "1" when the magnetization is oriented in one direction and "0" when the magnetization is oriented in the other direction, depending on the magnetization direction of the free layer in the magnetoresistive effect element. On the other hand, the stored information is read by extracting the difference in the magnetization direction of the free layer as a voltage signal through the change in the resistance value of the tunnel current.

In such an MRAM, in order to suppress information reading error, for example, when a TMR type magnetoresistive effect element is used, the resistance value of the tunnel current according to the difference in the magnetization direction of the free layer. It is effective to increase the so-called MR ratio, which is the change amount of. This MR ratio is greatly influenced by the spin polarizability of the ferromagnetic material forming the tunnel junction, and becomes larger as the spin polarizability of the ferromagnetic material layers (free layer and fixed layer) arranged on both sides of the nonmagnetic layer increases. Is known to be.

Spin polarizability is an electron (a unit of a very small magnet) that rotates (spins) upward in a solid.
And the number of electrons that spin downward, the size of which is specified mainly by the composition of the magnetic material forming the ferromagnetic layer. Therefore, if the ferromagnetic material layer is formed by using a magnetic material having a composition with a high spin polarization, the MR ratio of the magnetoresistive effect element including the ferromagnetic material layer can be increased, and as a result, a good MRAM can be obtained. It can be expected that information can be read out.

[0006]

However, even if the ferromagnetic layer exhibits a high spin polarizability in the state of a single material film, the magnetoresistive effect element has a multilayer film structure,
The MR ratio does not always increase in accordance with the spin polarizability. For example, in the case of a TMR type magnetoresistive effect element, a nonmagnetic layer is arranged adjacent to a free layer which is a ferromagnetic layer, and an aluminum (Al) oxide film is used as the nonmagnetic layer. It is common to be done. Therefore, depending on the method of forming the oxide film,
After formation or during heat treatment, oxygen (O) taken into the oxide film may move from the oxide film to an adjacent layer. However, if the oxygen that has moved from the oxide film diffuses into the ferromagnetic layer adjacent to it, the oxygen reacts with the magnetic material that forms the ferromagnetic layer, and the magnetic material originally has it. The spin polarizability may be impaired. Therefore, in the multi-layered film structure, for example, the diffusion property from the non-magnetic material layer causes a change in the magnetic characteristics of the ferromagnetic material layer, which makes it impossible to obtain a large MR ratio, resulting in a good MRAM. It is conceivable that such a good read characteristic cannot be realized.

Therefore, in view of the above conventional circumstances, the present invention provides a magnetoresistive effect element capable of obtaining a large MR ratio even in a multilayer film structure and realizing good read characteristics, a method of manufacturing the same, and a magnetic element. An object is to provide a memory device.

[0008]

The present invention has been devised to achieve the above object, and has a multilayer film structure including two ferromagnetic layers and a non-magnetic layer sandwiched therebetween. In the magnetoresistive effect element, at least one of the ferromagnetic layers is made of a material containing an element exhibiting ferromagnetism and boron.

According to the magnetoresistive element having the above-mentioned structure, since at least one ferromagnetic layer contains boron, for example, in the ferromagnetic layer, the adjacent nonmagnetic layer is made of an oxide film. Even when oxygen diffuses from the non-magnetic layer, boron preferentially bonds with the oxygen. Therefore, for the other elements, the magnetic characteristics are not impaired in response to oxygen diffusion and the like, and the original magnetic characteristics are maintained.

The manufacturing method of the present invention is a method for manufacturing a magnetoresistive effect element having a multilayer film structure including two ferromagnetic layers and a non-magnetic layer sandwiched between the ferromagnetic layers. The method is characterized by including a film forming step of forming a film of at least one of the materials by using a material containing an element exhibiting ferromagnetism and boron.

According to the method of manufacturing a magnetoresistive effect element of the above procedure, the ferromagnetic layer after the film formation in the film formation step contains boron. Therefore, for example, even when the adjacent non-magnetic layer is made of an oxide film and oxygen diffuses from the non-magnetic layer, the oxygen is preferentially bound to boron. Therefore, for the other elements, the magnetic characteristics are not impaired in response to oxygen diffusion and the like, and the original magnetic characteristics are maintained.

Further, the present invention has been devised to achieve the above object, and has a magnetoresistive effect of a multilayer film structure including two ferromagnetic layers and a nonmagnetic layer sandwiched therebetween. In a magnetic memory device comprising an element and configured to record information by utilizing a change in the magnetization direction of the ferromagnetic layer, at least one of the ferromagnetic layers is an element exhibiting ferromagnetism. And a material containing boron.

According to the magnetic memory device having the above structure, since the ferromagnetic material layer in the magnetoresistive effect element for recording information contains boron, the ferromagnetic material layer has, for example, an adjacent nonmagnetic material. Even when the body layer is made of an oxide film and oxygen diffuses from the nonmagnetic layer, boron preferentially bonds with the oxygen. Therefore, for the other elements, the magnetic characteristics are not impaired in response to oxygen diffusion and the like, and the original magnetic characteristics are maintained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetoresistive effect element, a method of manufacturing the same, and a magnetic memory device according to the present invention will be described below with reference to the drawings. Here, a TMR type spin valve element (hereinafter simply referred to as “TMR element”) as a magnetoresistive effect element and an MRAM having a TMR element as a magnetic memory device will be described as examples.

[Outline of Magnetic Memory Device] First, a schematic configuration of the entire magnetic memory device according to the present invention will be described. FIG. 1 is a schematic diagram showing a basic configuration example of the MRAM, and FIG. 2 is an enlarged perspective view of the main part thereof.

As shown in FIG. 1, the MRAM includes a plurality of TMR elements 1 arranged in a matrix. Further, word lines 2 and bit lines 3 intersecting each other are provided so as to cross each TMR element 1 group vertically and horizontally so as to correspond to each row and column in which these TMR elements 1 are arranged. . These word line 2 and bit line 3
Is formed using a well-known method such as conductive or chemical deposition of Al, Cu (copper) or alloys thereof, and then selective etching.

As a result, each TMR element 1 is sandwiched between the word line 2 and the bit line 3 from above and below as shown in FIG.
Each will be arranged. With such a configuration, in the MRAM, a combined current magnetic field is generated by causing a current to flow through both the word line 2 and the bit line 3 from the voltage terminals 2a and 3a provided respectively. Then, by changing the magnetization direction in the TMR element 1 using the combined current magnetic field, information is written in the TMR element 1.

FIG. 3 shows a single TMR constituting the MRAM.
It is a schematic diagram which shows an example of the cross-sectional structure of an element part. In each of the TMR element portions, a field effect transistor including a gate electrode 5, a source region 6 and a drain region 7 is arranged on a semiconductor substrate 4, and a word line 2, a TMR element 1 and a bit line 3 are provided above the field effect transistor. Are arranged in order. As a result, information can be read from the TMR element 1 by selecting the TMR element 1 using the field effect transistor and extracting the magnetization direction of the TMR element 1 as a voltage signal.

[Configuration of Magnetoresistive Effect Element] Next, the configuration of the TMR element 1 itself used in such an MRAM will be described. The TMR element 1 includes a free layer made of a ferromagnetic material, a non-magnetic layer made of an insulator, a fixed layer made of a ferromagnetic material, and an antiferromagnetic material for directly or indirectly fixing the magnetization direction of the fixed layer. A so-called ferromagnetic tunnel junction (MT) in which layers and layers are sequentially stacked.
J) has a structure called J), which is configured to record information by utilizing the change of the magnetization direction in the free layer and to change the resistance value of the tunnel current depending on the magnetization direction.

FIG. 4 is a side sectional view showing a specific example of the laminated structure of the TMR element. As shown in the figure, the TMR element 1 includes, for example, a 3 nm thick Ta (tantalum) film 12 and a 30 nm thick PtMn (platinum manganese) film on a substrate 11.
Film 13 and CoFe (cobalt iron) film 1 with a thickness of 1.5 nm
4a and a Ru (ruthenium) film 14b having a thickness of 0.8 nm
2 nm thick CoFe film 14c and 1 nm thick Al-
Ox (aluminum oxide) film 15 and 3 nm thick CoF
An example is a film structure in which an eB (cobalt iron boron) film 16 and a Ta film 17 having a thickness of 5 nm are sequentially stacked. The respective film thicknesses are merely examples and are not limited to these.

In such a film structure, the Ta film 12 functions as a base layer and the PtMn film 13 functions as an antiferromagnetic layer. In addition, two CoFe films 14a and 14c are formed via the Ru film 14b which is a non-magnetic layer.
The laminated ferri-structure part 14 in which the layers are laminated has a function as a fixed layer. Further, the Al-Ox film 15 functions as a non-magnetic layer, and the Ta film 17 functions as a protective film.

By the way, in the TMR element 1 mentioned here, the CoFeB film 16 functions as a free layer capable of reversing the magnetization direction, but the CoFeB film 16 is a ferromagnetic element such as Co (cobalt) and Fe. It has a great feature that it is made of a material containing B (boron) in addition to (iron). That is, the CoFeB film 16 is formed by adding B.

[Manufacturing Method of Magnetoresistive Element] Next, a manufacturing method of the TMR element 1 having the above configuration will be briefly described. In manufacturing the TMR element 1, for example, a magnetron sputtering apparatus in which back pressure is exhausted to an ultrahigh vacuum region is used. Then, on the substrate 11, the Ta film 12,
PtMn film 13, CoFe film 14a, Ru film 14b, C
The oFe film 14c and the Al film are sequentially stacked. Then Al
The film is placed under high pressure or in plasma to promote oxidation from the upper surface, and a uniform Al—Ox film 15 is obtained. Al-Ox
After the film 15 is obtained, the CoFeB film 16 and the Ta film 17 are sequentially formed again using, for example, a magnetron sputtering device. Finally, heat treatment for ordered alloying of the PtMn film 13 is performed in a magnetic field at 280 ° C. for 1 hour.

However, when the CoFeB film 16 is formed, B, which is an element of a different type from Co, and Fe, which are ferromagnetic elements, is added, and the film is formed. The design composition of the CoFeB film 16 at this time may be, for example, (Co90Fe10) 80B20 (atomic%). That is, the target, the sputter rate, etc. are adjusted so that the addition ratio of B becomes a predetermined amount or more (for example, 15% or more, preferably about 20%).

[Characteristics of Magnetoresistive Effect Element] Next, regarding the characteristics of the TMR element 1 manufactured including the film forming step of adding B as described above, a comparative example TM will be described.
It will be described together with the characteristics of the R element. As a comparative example, the free layer was made of CoF without the film forming step of adding B.
Although it is composed of an e-film, the other structure is similar to the TMR element 1 described above.

FIG. 5 is an explanatory diagram showing a specific example of the measurement result of the MR ratio. As shown in the figure, the MR ratio of the comparative example was 38%.
Regarding the TMR element 1 having the FeB film 16 as a free layer,
An MR ratio measurement result of 49% was obtained. That is,
It can be seen that the TMR element 1 having the CoFeB film 16 in the free layer has a larger MR ratio than the TMR element similar to the conventional one. This is presumably because B tends to precipitate at the grain boundaries rather than reacting with elements such as Co and Fe, and B reacts with O more easily than elements such as Co and Fe.

Explaining this point in more detail,
In general, the MR ratio is greatly affected by the spin polarizability of the ferromagnetic material forming the tunnel junction. However, in the above-mentioned film structure, the Al-Ox film 15 serving as the tunnel barrier is an oxide film, and therefore the Al- O diffused from the Ox film 15 may react with the ferromagnetic material forming the free layer, and the spin polarizability originally possessed by the ferromagnetic material may be impaired. However, in the TMR element 1, the Al--O
B is added to the CoFeB film 16 adjacent to the x film 15. As a result, in the CoFeB film 16, crystal grains are mainly formed of Co and Fe exhibiting ferromagnetism, and crystal grain boundaries are mainly formed of B having high bondability with O. Therefore, in the CoFeB film 16, even when O diffuses from the Al—Ox film 1, the B is preferentially bonded to O, so that Co and Fe are prevented from reacting with O. You can That is, CoFe
In the B film 16, since B is bound to the diffused O, the magnetic characteristics of Co and Fe are not impaired, and the original spin polarizability is maintained.

As described above, in the TMR element 1 of this embodiment, the CoFeB film 16 functioning as a free layer is B
Therefore, even if oxygen is diffused from the Al—Ox film 15 adjacent thereto, the B is preferentially bonded to O and the region where the spin polarizability is not lowered in the CoFeB film 16 ( It is considered that a high MR ratio was realized because of the remaining (inside the crystal grains).

Therefore, if the MRAM is constructed by using the TMR element 1 of this embodiment, a high MR ratio can be realized, so that a good read characteristic can be realized, which results in a large signal output and a high S / S ratio. It becomes possible to deal with N ratio and the like.

As described above, the Al-Ox film 15 is formed by forming the Al film and then placing the Al film under high pressure or in plasma to promote the oxidation from the upper surface. Therefore, immediately after formation, Al-
The oxygen concentration on the upper surface side of the Ox film 15 becomes high. And A
More O migrates to the adjacent layer on the upper surface side of the l-Ox film 15. From this, the addition of B was Al-
The adjacent layer on the upper surface side of the Ox film 15, that is, the Al-Ox film 1
It is very effective to work on the ferromagnetic layer deposited after 5. From this, in the TMR element 1 of this embodiment, the CoF adjacent to the upper surface side of the Al—Ox film 15 is adjacent.
That is, B is added to the eB film 16.

The film structure of the TMR element is not limited to the example described in this embodiment. For example, in the present embodiment, since the so-called bottom type TMR element 1 in which the free layer is located on the upper surface side of the Al—Ox film 15 is taken as an example, B is added to the CoFeB film 16, but Al—O.
In the case of a so-called top-type TMR element in which the fixed layer is located on the upper surface side of the x film 15, it is very effective to add B to the ferromagnetic layer that functions as the fixed layer.

The ferromagnetic layer to which B is added is not necessarily located on the upper surface side of the Al-Ox film 15, but B may be added to the ferromagnetic layer on the lower surface side or A
B may be added to both of the two ferromagnetic layers sandwiching the l-Ox film 15. That is, if B is added to at least one of the two ferromagnetic layers, Al-O is added.
Since the influence of oxygen diffusion from the x film 15 can be suppressed, high M
Realization of R ratio can be expected.

Further, in the present embodiment, CoFe is taken as an example of the ferromagnetic material to which B is added, but other materials may of course be used as long as it is a material made of an element exhibiting ferromagnetism. Is. That is, as an element exhibiting ferromagnetism, for example, Ni (nickel) is known in addition to Co and Fe, but a magnetic material (Ni
MTJ by adding B to Fe, NiFeCo, etc.)
It is also conceivable to construct a free layer or a fixed layer in the structure.

[0034]

As described above, according to the present invention, the ferromagnetic layer in the magnetoresistive effect element is made of a material containing an element exhibiting ferromagnetism and boron. For example, even when the non-magnetic layer adjacent to the ferromagnetic layer is made of an oxide film and oxygen diffuses from the non-magnetic layer, boron preferentially bonds with the oxygen. Therefore, for other elements,
Since the magnetic characteristics are not impaired by reacting with oxygen diffusion, etc., the original magnetic characteristics are maintained.
As a result, a high MR ratio can be realized, and good read characteristics with a low error rate can be realized when a magnetic memory device is constructed using the magnetoresistive effect element.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic configuration example of an MRAM.

FIG. 2 is an enlarged perspective view of a main part in a basic configuration example of an MRAM.

FIG. 3 is a schematic diagram showing a configuration example of a single TMR element portion which constitutes the MRAM.

FIG. 4 is a side sectional view showing a specific example of a laminated structure of a TMR element having an MTJ structure.

FIG. 5 is an explanatory diagram showing a specific example of the measurement result of the MR ratio in the TMR element to which the present invention is applied.

[Explanation of symbols]

1 ... TMR element, 11 ... Substrate, 12 ... Ta film, 13 ... P
tMn film, 14a, 14c ... CoFe film, 14b ... Ru
Film, 15 ... Al-Ox film, 16 ... CoFeB film, 17 ...
Ta film

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 43/12 H01L 27/10 447 (72) Inventor Masafumi Hosomi 6-7 Kitashinagawa, Shinagawa-ku, Tokyo No.35 Sony Corporation (72) Inventor Kazuhiro Oba 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Tetsuya Yamamoto 6-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Hiroshi Kano 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo F-Term (Sony Corporation) 5D034 BA03 BA04 BA15 CA00 CA08 DA07 5E049 AA04 AA09 AC05 BA16 CB02 DB12 5F083 FZ10 JA02 JA36 JA37 JA38 JA39 JA60

Claims (8)

[Claims] 1. In a magnetoresistive effect element having a multilayer film structure including two ferromagnetic layers and a non-magnetic layer sandwiched therebetween, at least one of the ferromagnetic layers is ferromagnetic. A magnetoresistive effect element comprising a material containing the element shown and boron. 2. The magnetoresistive element according to claim 1, wherein the boron is bound to oxygen diffused in the ferromagnetic layer to which the boron belongs. 3. The two ferromagnetic layers and a non-magnetic layer sandwiched therebetween are sequentially stacked, and at least the ferromagnetic layer formed on the upper surface side of the non-magnetic layer is formed. The magnetoresistive effect element according to claim 1, wherein the magnetoresistive effect element is formed by including the boron. 4. A method of manufacturing a magnetoresistive effect element having a multilayer film structure, comprising two ferromagnetic layers and a non-magnetic layer sandwiched therebetween, wherein at least one of the ferromagnetic layers is A method of manufacturing a magnetoresistive element, comprising a film forming step of forming a film using a material containing an element exhibiting ferromagnetism and boron. 5. The method of manufacturing a magnetoresistive element according to claim 4, wherein a ferromagnetic material layer is formed next to the non-magnetic material layer in the film forming step. 6. A magnetoresistive effect element having a multilayer film structure including two ferromagnetic layers and a non-magnetic layer sandwiched therebetween, and utilizing a change in the magnetization direction of the ferromagnetic layers. A magnetic memory device configured to record information by using at least one of the ferromagnetic layers made of a material containing an element exhibiting ferromagnetism and boron. 7. The magnetic memory device according to claim 6, wherein the boron is bonded to oxygen diffused in the ferromagnetic layer to which the boron belongs. 8. The two ferromagnetic layers and a non-magnetic layer sandwiched therebetween are sequentially stacked, and at least the ferromagnetic layer formed on the upper surface side of the non-magnetic layer is formed. 7. The magnetic memory device according to claim 6, wherein the magnetic memory device is formed to contain the boron.