WO2010064564A1

WO2010064564A1 - Magnetoresistive element, method of producing same, and storage medium used in method of producing same

Info

Publication number: WO2010064564A1
Application number: PCT/JP2009/069864
Authority: WO
Inventors: 正樹栗林; ダビッドジュリアントジャヤプラウィラ
Original assignee: キヤノンアネルバ株式会社
Priority date: 2008-12-01
Filing date: 2009-11-25
Publication date: 2010-06-10
Also published as: JPWO2010064564A1

Abstract

A magnetoresistive element having an MR ratio higher than those of prior arts. The magnetoresistive element is provided with a substrate (11), a first ferromagnetic layer (123) formed on top of the substrate (11), a tunnel barrier layer (122) formed on top of the first ferromagnetic layer (123) and having a crystal structure of a metal oxide containing B and Mg atoms, and a second ferromagnetic layer (121) formed on top of the tunnel barrier layer (122).

Description

Magnetoresistive element, method of manufacturing the same, and storage medium used in the method of manufacturing

The present invention relates to a magnetic reproducing head of a magnetic disk drive, a storage element of a magnetic random access memory, and a magnetoresistive element used for a magnetic sensor, preferably a tunnel magnetoresistive element (in particular, a spin valve tunnel magnetoresistive element). Furthermore, the present invention relates to a method of manufacturing a magnetoresistive element and a storage medium used in the method.

Patent Documents 1 to 4 and Non-patent Documents 1 to 5 describe TMR (Tunneling Magneto Resistance) effect elements using a crystalline magnesium oxide film made of single crystal or polycrystal as a tunnel barrier film. There is.

JP 2003-318465 A WO 2005/088745 pamphlet JP, 2006-80116, A US Patent Application Publication No. 2006/0056115

An object of the present invention is to provide a magnetoresistive element having a further improved MR ratio as compared with the prior art, a method of manufacturing the same, and a storage medium used in the method of manufacturing.

In order to solve such problems, the present invention is a magnetoresistive element, which comprises a substrate, a crystalline first ferromagnetic layer located on the substrate, and the crystalline first ferromagnetic layer. A tunnel barrier layer having a crystal structure of a metal oxide containing B atoms and Mg atoms, located on the side facing the substrate, and the crystalline first ferromagnetic layer of the tunnel barrier layer And a crystalline second ferromagnetic layer located on the side.

The present invention also relates to a method of manufacturing a magnetoresistive element, which comprises a first step of forming a first ferromagnetic layer on a substrate by sputtering, and the first step of sputtering using a sputtering method. A second step of forming a crystalline layer containing a metal oxide containing B atoms and Mg atoms on a magnetic layer, and a sputtering method, using the sputtering method, on the crystalline layer containing the metal oxide, And forming a second ferromagnetic layer.

Furthermore, the present invention is a storage medium storing a control program for causing a computer to execute a method of manufacturing a magnetoresistive element, wherein the manufacturing method forms a film of a first ferromagnetic layer on a substrate. A second sputtering step of depositing a crystal layer containing a metal oxide containing B atoms and Mg atoms on the first ferromagnetic layer, and a crystal layer containing the metal oxide And a third sputtering step of depositing a second ferromagnetic layer thereon.

According to the present invention, the MR ratio achieved by the conventional tunnel magnetoresistive effect element (hereinafter referred to as TMR element) can be significantly improved. In addition, the present invention can be mass-produced and highly practical. Therefore, by using the present invention, a memory element of MRAM (Magnetoresistive Random Access Memory: ferroelectric memory) capable of achieving ultra-high integration can be efficiently provided. .

It is a cross-sectional schematic diagram of an example of the magnetoresistive element of this invention. It is a figure which shows typically the structure of an example of the film-forming apparatus which manufactures the magnetoresistive element of this invention. Figure 3 is a block diagram of the device of Figure 2; It is a model perspective view of MRAM comprised using the magnetoresistive element of this invention. It is an equivalent circuit schematic of MRAM comprised using the magnetoresistive element of this invention. FIG. 6 is a cross-sectional view of another tunnel barrier layer of the present invention. It is a model perspective view of the column-like crystal structure which concerns on the magnetoresistive element of this invention. It is sectional drawing of the TMR element of the other structure of the magnetoresistive element of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings described below, components having the same function are denoted by the same reference numerals, and the repetitive description thereof is omitted.
A magnetoresistive element according to the present invention comprises a substrate, a crystalline first ferromagnetic layer located on the substrate side, a tunnel barrier layer located on the crystalline first ferromagnetic layer, and the tunnel barrier layer. And a crystalline second ferromagnetic layer located on the top of the first magnetic layer. Furthermore, an antiferromagnet layer located on the crystalline second ferromagnetic layer may be provided. The tunnel barrier layer has a crystal structure of a metal oxide containing B (boron) atoms and Mg atoms (hereinafter referred to as BMg oxide). The upper surface of the crystalline second ferromagnetic layer and the lower surface of the antiferromagnetic layer may be interface-connected to each other. In addition, an intermediate layer may be provided between the crystalline second ferromagnetic layer and the antiferromagnetic layer. The intermediate layer is, for example, a nonmagnetic material represented by a metal layer (for example, Cu layer, Mg layer, Ru layer, etc.) or a metal oxide layer (for example, MgO layer, TiO ₂ layer, Al ₂ O ₃ layer, etc.) It may be a layer, or may be a laminate layer in which the metal layer and / or the metal oxide layer are laminated as one layer or two or more layers.
In the magnetoresistive element of the present invention, the tunnel barrier layer is an alloy layer containing B atoms and Mg atoms (hereinafter referred to as BMg layer) or a metal layer composed of Mg atoms (hereinafter referred to as Mg layer). Note) may be included. In this case, a laminated film having a BMg oxide crystal layer is formed on both sides of the BMg layer or Mg layer. The BMg layer or the Mg layer may be a single layer or a plurality of two or more layers, and in the case of two or more layers, a crystalline BMg oxide layer is provided between the respective layers.

As described above, in the present invention, the tunnel barrier layer of the TMR element is made to have the crystal structure of the metal oxide containing B atoms and Mg atoms, so that the MR ratio is significantly larger than that of the conventional TMR element. It can be improved.

In the tunnel barrier layer according to the present invention, the content of B atoms in the metal oxide is preferably 30 atomic% or less, more preferably in the range of 0.01 atomic% to 20 atomic%.

Further, the BMg oxide used in the present invention has a general formula B _x Mg _y O _z (0.7 ≦ Z / (X + Y) ≦ 1.3, preferably 0.8 ≦ Z / (X + Y) < It is indicated by 1.0). In the present invention, although it is preferable to use a stoichiometric amount of BMg oxide, a high MR ratio can be obtained by using an oxygen deficient BMg oxide.

In the magnetoresistive element of the present invention, an Mg layer or Mg atoms are contained between the first ferromagnetic layer and the tunnel barrier layer and / or between the second ferromagnetic layer and the tunnel barrier layer. An alloy layer (hereinafter referred to as a Mg alloy layer) may be provided. As the Mg alloy layer, BMg is preferably used.

In the first ferromagnetic layer and the second ferromagnetic layer used in the present invention, preferably, an alloy of Co, Fe and B (hereinafter referred to as CoFeB), an alloy of Co and Fe (hereinafter, CoFe) Is preferably used. Further, alloys of Co, Fe and Ni (hereinafter referred to as CoFeNi) and alloys of Co, Fe, Ni and B (hereinafter referred to as CoFeNiB) are also preferably used. Furthermore, an alloy of Ni and Fe (hereinafter referred to as NiFe) is also preferably used. In the present invention, at least one type can be selected from the above alloy group.

Further, the first ferromagnetic layer and the second ferromagnetic layer according to the present invention may be the same alloy, or may be an alloy different from each other.

In the magnetoresistive element of the present invention, preferably, each of the first ferromagnetic layer, the tunnel barrier layer, and the second ferromagnetic layer is an aggregate of columnar crystals (including needle crystals, columnar crystals, and the like). It has a polycrystalline structure formed.

FIG. 7 is a schematic perspective view of a polycrystalline structure composed of an aggregate 71 of column-like crystals 72 of BMg oxide. The polycrystalline structure also includes the structure of a polycrystalline-amorphous mixed region including a partially amorphous region in the polycrystalline region. The column-like crystal is preferably a single crystal in which the (001) crystal plane is preferentially oriented in the film thickness direction in each column. The average diameter of the column-like single crystals is preferably 10 nm or less, more preferably in the range of 2 nm to 5 nm. The film thickness is preferably 10 nm or less, more preferably in the range of 0.5 nm to 5 nm.
As the antiferromagnetic layer used in the present invention, for example, an alloy such as PtMn, PdMn, IrMn, RhMn or RuOsMn can be used.
Next, a method of manufacturing the magnetoresistive element of the present invention will be described. The production method of the present invention comprises the following steps. First step: A first ferromagnetic layer of amorphous structure is formed by sputtering. Second step: A crystalline layer of BMg oxide is deposited on the first ferromagnetic layer by sputtering. Third step: A second ferromagnetic layer of an amorphous structure is formed on the BMg oxide crystal layer by sputtering. Fourth step: converting the amorphous structure of the first ferromagnetic layer and the second ferromagnetic layer into a crystal structure.

In the present invention, each of the first step, the second step and the third step can be carried out using an independent sputtering apparatus (for example, a film forming chamber). For example, the first step is performed using a first sputtering apparatus, and then the substrate is carried from the first sputtering apparatus to the second sputtering apparatus, where the second process is performed. Subsequently, the substrate is carried from the second sputtering apparatus to the third sputtering apparatus, where the third step is performed. In particular, in the present invention, the film forming process of the BMg oxide layer and the film forming process of the first and second ferromagnetic layers are preferably carried out using different sputtering apparatuses.

The sputtering apparatus used in the present invention is preferably a magnetron sputtering apparatus that applies high frequency power (for example, RF power) to the target.

In the present invention, an annealing process, an ultrasonic wave application process, and the like can be used as the fifth process performed after the fourth process, but it is particularly preferable to use an annealing process using an infrared irradiation method. During the annealing step, the amorphous structure of the first ferromagnetic material and the second ferromagnetic material located at the interface of the BMg oxide crystal layer starts epitaxial growth from the interface to the crystal structure. As a result, columnar crystals are formed in the layer thickness direction of the first ferromagnetic layer and the second ferromagnetic layer from the interface.

The annealing step used in the present invention is performed at 200 ° C. to 500 ° C. (preferably 230 ° C. to 400 ° C.) for 1 hour to 6 hours (preferably 2 hours to 5 hours). Depending on the temperature and heating time of this annealing step, the crystallinity of the produced crystals can be changed. In the present invention, the degree of crystallinity can be 90% or more per total volume, and in particular, the degree of crystallinity can be 100%.

The second step according to the present invention is preferably a step of forming a crystalline layer of BMg oxide by sputtering using a target made of BMg oxide. In particular, reactive sputtering using the target and an oxidizing gas is preferable, and oxygen gas, ozone gas, water vapor and the like are preferably used as the oxidizing gas.

Next, the storage medium of the present invention will be described. The control program for making a computer perform the following process and manufacturing a magnetoresistive element is memorize | stored in the storage medium which concerns. First sputtering step: A first ferromagnetic layer of amorphous structure is deposited. Second sputtering step: A crystalline layer of BMg oxide is formed on the first ferromagnetic layer. Third sputtering step: A second ferromagnetic layer of an amorphous structure is formed on the crystalline layer of the metal oxide (BMg oxide). Fourth sputtering step: An antiferromagnetic layer is formed on the second ferromagnetic layer. Crystallization step: The amorphous structure of the first ferromagnetic layer and the second ferromagnetic layer is converted into a crystal structure.

The crystallization step is preferably an annealing step. The second sputtering step is preferably a sputtering step using a target made of BMg oxide. In particular, as the second sputtering step, a reactive sputtering step using a target composed of the BMg oxide and an oxidizing gas is preferable. Further, as the oxidizing gas, oxygen gas, ozone gas, water vapor and the like are preferably used.

Examples of the storage medium of the present invention include hard disk media, magneto-optical disk media, floppy (registered trademark) disk media, nonvolatile memories such as flash memory and MRAM, and the like, and include media capable of storing programs.

Hereinafter, preferred embodiments of the present invention will be described in more detail.
FIG. 1 shows an example of the laminated structure of the top type magnetoresistance element 10 of the present invention, and shows the laminated structure of the magnetoresistance element 10 using the TMR element 12. According to the magnetoresistive element 10, the TMR element 12 formed on the substrate 11 is provided. The top type magnetoresistive element 10, including the TMR element 12, has, for example, a multilayer film of nine layers. The nine-layer multilayer film has a multilayer film structure from the lowermost first layer (Ta layer) to the uppermost ninth layer (Ru layer). Specifically, a magnetic layer and a nonmagnetic layer are sequentially formed of a CoFeB layer, a nonmagnetic BMg oxide layer, a CoFeB layer, a nonmagnetic Ru layer, a CoFe layer, an antiferromagnetic layer PtMn layer, a nonmagnetic Ta layer and a nonmagnetic Ru layer. A magnetic layer is laminated. The numerical values in the parentheses of each layer indicate the thickness of each layer, and the unit is nm. The said thickness is an example, Comprising: It is not limited to this. Further, the antiferromagnetic material layer PtMn layer is an alloy layer containing Pt atoms and Mn atoms.

In FIG. 1, reference numeral 11 denotes a substrate such as a wafer substrate, a glass substrate or a sapphire substrate. Reference numeral 12 denotes a TMR element, which includes a first ferromagnetic layer 123, a tunnel barrier layer 122, and a second ferromagnetic layer 121. Reference numeral 13 denotes a lower electrode layer (base layer) of the first layer (Ta layer), and reference numeral 14 denotes an antiferromagnetic layer of a seventh layer (PtMn layer). Reference numeral 15 is a ferromagnetic layer of a sixth layer (CoFe layer), reference numeral 16 is a nonmagnetic layer for exchange coupling of the fifth layer (Ru layer), and reference numeral 121 is a fourth layer (crystalline CoFeB layer). Ferromagnetic layer. A layer including the fourth layer 121, the fifth layer 16 and the sixth layer 15 is the magnetization fixed layer 19. The substantial magnetization fixed layer 19 is a ferromagnetic layer 121 composed of the crystalline CoFeB layer of the fourth layer, and corresponds to the above-mentioned second ferromagnetic layer according to the present invention.

A tunnel barrier layer 122 is a third layer (polycrystalline BMg oxide) and is an insulating layer. The tunnel barrier layer 122 according to the present invention may be a single polycrystalline BMg oxide layer.

In the present invention, as illustrated in FIG. 6, B as a crystalline BMg layer or Mg layer 1222 such as microcrystalline, polycrystalline or single crystal in a polycrystalline BMg oxide layer as a tunnel barrier layer 122 An alloy layer containing atoms and Mg atoms or Mg atoms may be provided. In this case, a layered structure in which polycrystalline

BMg oxide layers

1221 and 1223 are provided on both sides of the BMg layer or Mg layer 1222 is adopted. Furthermore, the BMg layer or Mg layer 1222 illustrated in FIG. 6 can be a plurality of layers including two or more layers, and can be alternate layers stacked alternately with the BMg oxide layer.

FIG. 8 is an example of another TMR element 12 of the present invention.

Reference numerals

12, 121, 122 and 123 in FIG. 8 denote the same members as those in FIG. In this example, the tunnel barrier layer 122 is a laminated film in which a BMg oxide layer 82 and a BMg layer or Mg layers 81 and 83 on both sides of the layer 82 are laminated. In addition, the layer 81 in the above example may be a BMg layer and the layer 83 may be a Mg layer, or the layer 81 in the above example may be an Mg layer and the layer 83 may be a layer BMg layer. Also, in the present invention, the use of the layer 81 described above may be omitted, and the layer 82 may be disposed adjacent to the crystalline ferromagnetic layer 123, or the use of the layer 83 described above may be omitted and the layer 82 It can be disposed adjacent to the ferromagnetic layer 121. Thus, in the embodiment shown in FIG. 8, either one of the first ferromagnetic layer 123 and the BMg oxide layer 82 and the second ferromagnetic layer 121 and the BMg oxide layer 82. A metal layer of Mg atoms or an alloy layer containing Mg atoms is provided.

In FIG. 1, reference numeral 123 denotes a crystalline ferromagnetic layer of a second layer (CoFeB layer), which is a magnetization free layer, and corresponds to the first ferromagnetic layer according to the present invention. In addition to the above, the second layer 123 may be a crystalline ferromagnetic layer made of polycrystalline NiFe made of an aggregate of columnar crystals.

The crystalline

ferromagnetic layers

121 and 123 are preferably provided adjacent to the tunnel barrier layer 122 located between them. In the manufacturing apparatus, these three layers are sequentially stacked without breaking the vacuum.

Reference numeral 17 denotes an electrode layer of an eighth layer (Ta layer), and reference numeral 18 denotes a hard mask layer of a ninth layer (Ru layer). The ninth layer may be removed from the magnetoresistive element when used as a hard mask.

The ferromagnetic layer 121 (CoFeB layer) which is the fourth layer among the above-mentioned magnetization fixed layers, the third layer (polycrystalline BMg oxide layer) which is the tunnel barrier layer 122, and the second layer which is the magnetization free layer The TMR element 12 is formed by the magnetic layer 123 (CoFeB layer).

The tunnel barrier layer 122 (BMg oxide layer), the crystalline ferromagnetic layer 121 (CoFeB layer), and the crystalline ferromagnetic layer 123 preferably have the column-like crystal structure 71 shown in FIG. 7 described above.

Next, with reference to FIG. 2, an apparatus and a method of manufacturing the magnetoresistive element 10 having the above-described laminated structure will be described. FIG. 2 is a schematic plan view of an apparatus for manufacturing the magnetoresistive element 10. This apparatus is an apparatus capable of producing a multilayer film including a plurality of magnetic layers and a nonmagnetic layer, and mass production type sputtering film formation It is an apparatus.

The magnetic multilayer film manufacturing apparatus 200 shown in FIG. 2 is a cluster type manufacturing apparatus, and includes three film forming chambers based on the sputtering method. In the present apparatus 200, a transfer chamber 202 including a robot transfer device (not shown) is installed at a central position. Two load lock / unload

lock chambers

205 and 206 are provided in the transfer chamber 202 of the manufacturing apparatus 200 for manufacturing the magnetoresistance element, and loading and unloading of the substrate (for example, silicon substrate) 11 is performed by each of them. . By alternately carrying in and out the substrate by the load lock / unload

lock chambers

205 and 206, the tact time can be shortened, and the magnetoresistive element can be manufactured with high productivity.

In the manufacturing apparatus 200 for manufacturing a magnetoresistive element, three deposition magnetron sputtering chambers 201A to 201C and one etching chamber 203 are provided around the transfer chamber 202. In the etching chamber 203, the required surface of the TMR element 10 is etched. A gate valve 204 which can be opened and closed is provided between each of the chambers 201A to 201C and 203 and the transfer chamber 202. Each of the chambers 201A to 201C and 202 is provided with an evacuation mechanism, a gas introduction mechanism, a power supply mechanism, and the like (not shown). In the magnetron sputtering chambers 201A to 201C for film formation, the respective films from the first layer to the ninth layer described above can be sequentially deposited on the substrate 11 using high frequency sputtering without breaking the vacuum. it can.

Four or five cathodes 31 to 35, 41 to 45, 51 to 54 disposed on suitable circumferences are disposed on the ceilings of the film forming magnetron sputtering chambers 201A to 201C, respectively. Furthermore, the substrate 11 is disposed on a substrate holder located coaxially with the circumference. Moreover, it is preferable to set it as the magnetron sputtering apparatus which has arrange | positioned the magnet behind the target with which said cathodes 31 to 35, 41 to 45, 51 to 54 were mounted.

In the above apparatus, high frequency power such as radio frequency (RF frequency) is applied to the cathodes 31 to 35, 41 to 45, 51 to 54 from the power input means 207A to 207C. As high frequency power, power in the range of 0.3 MHz to 10 GHz, preferably in the range of 5 MHz to 5 GHz and in the range of 10 W to 500 W, preferably 100 W to 300 W can be used.

In the above, for example, a Ta target is attached to the cathode 31, a PtMn target to the cathode 32, a CoFeB target to the cathode 33, a CoFe target to the cathode 34, and a Ru target to the cathode 35, respectively. Further, a BMg oxide target or a BMg target is attached to the cathode 41. When a BMg target is used, a reactive sputtering chamber (not shown) for performing reactive sputtering with an oxidizing gas can be connected to the transfer chamber 202.

In addition, after a polycrystalline BMg layer is formed by sputtering using a BMg target, polycrystalline BMg oxide is formed in an oxidation chamber (not shown) using an oxidizing gas (eg, oxygen gas, ozone gas, water vapor, etc.) It can be chemically changed into layers.

Further, as another embodiment, a BMg oxide target can be attached to the cathode 41 and a BMg target can be attached to the cathode 42. At this time, targets can not be attached to the cathodes 43 to 45. Further, a BMg oxide target or a BMg target can also be attached to the cathodes 43 to 45.

A CoFeB target is attached to the cathode 51 and a Ta target is attached to the cathode 52. The cathode 53 has no target attached. Also, the cathode 54 has no target attached.

The in-plane direction of each of the targets mounted on the cathodes 31 to 35, 41 to 45, and 51 to 52 and the in-plane direction of the substrate are preferably arranged non-parallel to each other. By using the non-parallel arrangement and sputtering while rotating a target smaller than the substrate diameter, magnetic films and nonmagnetic films can be deposited with high efficiency and the same composition as the target composition. The diameter of the target mounted on the cathodes 31 to 35, 41 to 45, and 51 to 52 is 0.1 to 0.9 times the diameter of the substrate, preferably 0.2 times the diameter of the substrate. To 0.5 times.

In the non-parallel arrangement, for example, both can be arranged non-parallel so that the crossing angle between the target central axis and the substrate central axis is 45 ° or less, preferably 5 ° to 30 °. Also, the substrate at this time can use a rotational speed of 10 rpm to 500 rpm, preferably, a rotational speed of 50 rpm to 200 rpm.

FIG. 3 is a block diagram of a film forming apparatus used in the present invention. In the figure, reference numeral 301 denotes a transfer chamber corresponding to the transfer chamber 202 in FIG. 2, reference numeral 302 denotes a film forming chamber corresponding to the magnetron sputtering chamber 201A for film formation, and reference numeral 303 denotes a film corresponding to the magnetron sputtering chamber 201B for film formation. It is a membrane chamber. Reference numeral 304 denotes a film forming chamber corresponding to the film forming magnetron sputtering chamber 201C, and reference numeral 305 denotes a load lock and unload lock chamber corresponding to the load lock and unload

lock chambers

205 and 206. Further, reference numeral 306 denotes a central processing unit (CPU) incorporating the storage medium 312. Reference numerals 309 to 311 are bus lines connecting the CPU 306 and the processing chambers 301 to 305, and control signals for controlling the operations of the processing chambers 301 to 305 are transmitted from the CPU 306 to the processing chambers 301 to 305.

In the manufacture of the magnetoresistive element of the present invention, for example, a substrate (not shown) in the load lock / unload lock chamber 305 is carried out to the transfer chamber 301. The substrate unloading step is calculated based on a control program as a computer-executable program stored in the storage medium 312 by the CPU 306. Then, the CPU 306 transmits control signals based on the calculation result to the various devices mounted on the load lock / unlock chamber 305 and the transfer chamber 301 through the

bus lines

307 and 311. That is, the substrate unloading step is performed by the CPU 306 controlling the execution of the various devices according to the control signal. Examples of the various devices include a gate valve (not shown), a robot mechanism, a transport mechanism, a drive system, etc., and the storage medium 312 corresponds to the storage medium of the present invention described above.

The substrate transported to the transport chamber 301 is carried out to the film forming chamber 302. Here, the first layer 13 and the second layer 123 of FIG. 1 are sequentially stacked on the substrate carried into the film forming chamber 302. The CoFeB layer of the second layer 123 at this stage preferably has an amorphous structure, but may have a polycrystalline structure.

In the stacking process, various control signals are loaded in the transfer chamber 301 and the film forming chamber 304 through the

bus lines

307 and 310 by the CPU 306 in the CPU 306 based on the control program stored in the storage medium 312. Send to device. That is, the transfer of the substrate to the film forming chamber 304 by the transfer chamber 301 and the film forming of the first layer 13 and the second layer 123 by the film forming chamber 304 are controlled by the CPU 306 based on the control signal. To be implemented. As various devices which concern, for example, a power input mechanism to a cathode (not shown), a substrate rotation mechanism, a gas introduction mechanism, an exhaust mechanism, a gate valve, a robot mechanism, a transport mechanism, a drive system and the like can be mentioned.
Thus, according to the control program, the CPU 306 controls the film forming chamber 304 to form the second layer 123 as the first ferromagnetic layer on the first layer 13.

The substrate having the laminated film up to the second layer is temporarily returned to the transfer chamber 301 and then carried into the film forming chamber 303. In the film forming chamber 303, a polycrystalline BMg oxide layer is formed as the third layer 122 on the amorphous CoFeB layer of the second layer 123. In the film formation of the third layer 122, the CPU 306 controls the control signal calculated based on the control program stored in the storage medium 312 in the CPU 306 through the

bus lines

307 and 309 to the transfer chamber 301 and the film forming chamber. It transmits to various devices mounted in 303. That is, the transfer of the substrate to the deposition chamber 303 by the transfer chamber 301 and the deposition of the third layer 122 by the deposition chamber 303 are performed by the CPU 306 controlling the execution of the various devices according to the control signal. . Examples of the various devices include a power input mechanism to a cathode (not shown), a substrate rotation mechanism, a gas introduction mechanism, an exhaust mechanism, a gate valve, a robot mechanism, a transport mechanism, a drive system and the like.
As described above, the CPU 306 controls the film forming chamber 303 to form the third layer 122 as a tunnel barrier layer on the second layer 123 according to the control program.

The substrate stacked up to the third layer 122 is once returned again to the transfer chamber 301, and is then carried into the deposition chamber 302. In the film forming chamber 304, the fourth layer 121, the fifth layer 16, the sixth layer 15, the seventh layer 14, the eighth layer 17, and the ninth layer are formed on the polycrystalline BMg oxide layer of the third layer 122. Layers 18 are sequentially stacked. The CoFeB layer of the fourth layer 121 at this stage preferably has an amorphous structure, but may have a polycrystalline structure.

In the stack up to the ninth layer, the CPU 306 controls the control signal calculated based on the control program stored in the storage medium 312 in the CPU 306 through the

bus lines

307 and 308 to the transfer chamber 301 and the film forming chamber 302. Send to various devices installed in That is, the transfer of the substrate to the film forming chamber 302 by the transfer chamber 301 and the film forming of the fourth layer 121 to the ninth layer 18 by the film forming chamber 302 are controlled by the CPU 306 by the control signal. It is carried out by doing. Examples of the various devices include a power input mechanism to a cathode (not shown), a substrate rotation mechanism, a gas introduction mechanism, an exhaust mechanism, a gate valve, a robot mechanism, a transport mechanism, a drive system and the like.

Thus, according to the control program, the CPU 306 controls the film forming chamber 302 to form the fourth layer 121 as the second ferromagnetic layer on the third layer 122, and further, the fourth layer 121. The fifth layer 16 to the ninth layer 18 are sequentially formed on the top.

As described above, the storage medium 312 of the present invention can be any of non-volatile memory such as hard disk medium, magneto-optical disk medium, floppy (registered trademark) disk medium, flash memory and MRAM, and can store programs. It includes the medium.

In order to promote the polycrystallization of the amorphous CoFeB layer of the fourth layer 121 and the second layer 123 by annealing, and to promote the magnetic application of the antiferromagnetic PtMn layer of the seventh layer 14, the first to ninth layers are described. The laminated film consisting of layers can be carried into an annealing furnace (not shown).

The storage medium 312 stores a control program for performing the process in the annealing furnace. Therefore, according to a control signal obtained by the operation of the CPU 306 based on the control program, various devices in the annealing furnace (for example, a heater mechanism, an exhaust mechanism, a transport mechanism, etc. not shown) are controlled to execute the annealing process. Can. That is, when at least one of the second layer 123 as the first ferromagnetic layer and the fourth layer 121 as the second ferromagnetic layer has an amorphous structure, the CPU 306 controls the annealing furnace to form the second layer. The amorphous structure of 123 and / or the fourth layer 121 can be transformed into a crystalline structure.

In the present invention, other alloy layers can be used as the fourth layer 121 and the second layer 123 instead of the above-described CoFeB layer. Specifically, a polycrystalline ferromagnetic layer such as a CoFeTaZr layer, a CoTaZr layer, a CoFeNbZr layer, a CoFeZr layer, a FeTaC layer, an FeTaN layer, or an FeC layer can be used.

In the present invention, in place of the Ru layer of the fifth layer 16, an Rh layer or an Ir layer can be used.

Furthermore, in the present invention, instead of the PtMn layer of the seventh layer 14, alloy layers such as IrMn layer, IrMnCr layer, NiMn layer, PdPtMn layer, RuRhMn layer and OsMn layer are preferably used. The film thickness is preferably 10 to 30 nm.

In the present invention, the polycrystalline CoFeB layer of the fourth layer 121 can be a two-layered film of a polycrystalline CoFeB layer and a polycrystalline CoFe layer (located on the side of the antiferromagnetic layer 14). In this case, the polycrystalline CoFe layer located on the side of the antiferromagnetic layer 14 can be deposited in a polycrystalline state on the BMgO layer of the fourth layer by sputtering.

The present inventors confirmed that the CoFeB layer following the film formation of the polycrystalline CoFe layer has an amorphous structure immediately after the sputtering film formation (before the annealing step). Therefore, by annealing the CoFeB layer of the amorphous structure, it is possible to change the phase to an epitaxial polycrystalline structure.

FIG. 4 is a schematic view of an MRAM 401 using the magnetoresistive element of the present invention as a memory element. In the MRAM 401, reference numeral 402 is a memory element of the present invention, reference numeral 403 is a word line, and reference numeral 404 is a bit line. Each of the large number of memory elements 402 is arranged at each intersection position of the plurality of word lines 403 and the plurality of bit lines 404, and is arranged in a lattice-like positional relationship. Each of the multiple memory elements 402 can store one bit of information.

FIG. 5 is an equivalent circuit diagram including the TMR element 10 storing 1-bit information and the transistor 501 having a switch function at the intersection of the word line 403 and the bit line 404 of the MRAM 401.

(Example)
The magnetoresistive element shown in FIG. 1 was manufactured using the film forming apparatus shown in FIG. The film formation conditions of the TMR element 12 which is the main part are as follows.

The ferromagnetic layer 123 is formed at a sputtering rate of 0.64 nm / sec by magnetron DC sputtering (chamber 201C) at an Ar gas pressure of 0.03 Pa using a target having a CoFeB composition ratio (atomic: atomic ratio) of 60/20/20. I made a film. The CoFeB layer (ferromagnetic layer 123) at this time had an amorphous structure. Subsequently, it was changed to a sputtering apparatus (chamber 201B). Using a target having a BMgO composition ratio (atomic: atomic ratio) of 25/25/50, the pressure of the sputtering gas was set to 0.2 Pa within the pressure range of 0.01 to 0.4 Pa in a preferable range. Under this condition, the tunnel barrier layer 122 which is a BMg oxide layer of the sixth layer was formed by magnetron RF sputtering (13.56 MHz). At this time, the BMg oxide layer (tunnel barrier layer 122) had a polycrystalline structure composed of aggregates of columnar crystals. Moreover, the film-forming rate of magnetron RF sputtering (13.56 MHz) at this time was 0.14 nm / sec.

Subsequently, instead of the sputtering apparatus (chamber 201A), the ferromagnetic layer 121, which is the magnetization fixed layer (the fourth CoFeB layer), was formed. It was confirmed that the fourth CoFeB layer (ferromagnetic layer 121) had an amorphous structure.
Next to the fourth layer 121, the fifth Ru layer 16, the sixth CoFe layer 15, the seventh PtMn layer 14, the eighth Ta layer 17 and the eighth layer forming the magnetization fixed layer are formed. A Ru layer 18 of nine layers was continuously formed by the chamber 201A without breaking the vacuum state to form a laminated film.

In this example, the film forming speed of the BMg oxide layer is 0.14 nm / sec, but there is no problem if the film is formed in the range of 0.01 nm to 1.0 nm / sec.

Annealing treatment is performed in a magnetic field of 8 kOe at about 300 ° C. and 4 hours in a heat treatment furnace with respect to the magnetoresistive element 10 in which lamination is completed by performing sputtering film formation in each of the film forming magnetron sputtering chambers 201A to 201C. Carried out. As a result, it was confirmed that the CoFeB layers of the second layer and the fourth layer of the amorphous structure had a polycrystalline structure composed of the aggregate 71 of the column-like crystals 72 shown in FIG. By this annealing step, the magnetoresistive element 10 can act as a magnetoresistive element having a TMR effect. Moreover, predetermined magnetization was given to the antiferromagnetic material layer 14 which is a PtMn layer of a 7th layer by this annealing process.

As a comparative example of the present invention, in place of the tunnel barrier layer 122 made of a polycrystalline BMg oxide layer, a magnetoresistive element using a polycrystalline Mg oxide layer in which the use of B atoms is omitted was produced.

When the MR ratio of the magnetoresistive element of the example and the magnetoresistive element of the comparative example was measured and compared, the MR ratio of the example was 1.2 to 1.5 times or more the MR ratio of the comparative example. It has been improved. As described above, according to this embodiment, since the crystal structure of the metal oxide containing B atoms and M atoms is used as the tunnel barrier layer of the TMR element, the MR ratio can be increased.

Incidentally, BMg oxide tunnel barrier layer used in this example was BMg oxide oxygen deficiency represented by the general formula _{_{_{B x Mg y O z (Z}}} / (X + Y) = 0.95).

The MR ratio is a parameter related to the magnetoresistance effect in which the electric resistance of the film also changes as the magnetization direction of the magnetic film or magnetic multilayer film changes in response to an external magnetic field. The rate of change in resistance (MR ratio) is used.

Claims

A substrate,
A crystalline first ferromagnetic layer located on the substrate;
A tunnel barrier layer having a crystal structure of a metal oxide containing B atoms and Mg atoms, which is located on the side of the crystalline first ferromagnetic layer facing the substrate;
A magnetoresistive element comprising: a crystalline second ferromagnetic layer positioned on the side facing the crystalline first ferromagnetic layer of the tunnel barrier layer.
The magnetoresistive element according to claim 1, further comprising an antiferromagnetic layer located on the side facing the tunnel barrier layer of the crystalline second ferromagnetic layer.
2. The magnetoresistive element according to claim 1, wherein the content of B atoms in the metal oxide in the tunnel barrier layer is 30 atomic% or less.
The tunnel barrier layer is
And an alloy layer containing B atoms and Mg atoms or a metal layer composed of Mg atoms,
The magnetoresistive element according to claim 1, wherein the magnetoresistive element is a laminated film having a crystal layer of a metal oxide containing B atoms and Mg atoms on both sides of the alloy layer or the metal layer.
2. A magnetoresistive element according to claim 1, further comprising a metal layer made of Mg atoms or an alloy layer containing Mg atoms between the crystalline first ferromagnetic layer and the tunnel barrier layer.
The magnetoresistive element according to claim 5, wherein the alloy layer containing Mg atoms is an alloy layer containing Mg atoms and B atoms.
The magnetoresistive element according to claim 1, further comprising a metal layer made of Mg atoms or an alloy layer containing Mg atoms between the crystalline second ferromagnetic layer and the tunnel barrier layer.
The magnetoresistive element according to claim 7, wherein the alloy layer is an alloy layer containing Mg atoms and B atoms.
The magnetic device according to claim 1, wherein each of the first ferromagnetic layer, the tunnel barrier layer, and the second ferromagnetic layer has a polycrystalline structure formed by an assembly of columnar crystals. Resistance element.
A first step of forming a first ferromagnetic layer on a substrate using a sputtering method;
A second step of forming a crystalline layer containing a metal oxide containing B atoms and Mg atoms on the first ferromagnetic layer using a sputtering method;
A third step of depositing a second ferromagnetic layer on the crystalline layer containing the metal oxide using a sputtering method;
A manufacturing method of a magnetoresistive element characterized by having.
At least one of the first ferromagnetic layer and the second ferromagnetic layer has an amorphous structure,
11. The method of manufacturing a magnetoresistive element according to claim 10, further comprising the step of converting the amorphous structure into a crystal structure after the third step.
The method of manufacturing a magnetoresistive element according to claim 11, wherein the converting step includes an annealing step.
11. The magnetic resistance according to claim 10, further comprising the step of forming an antiferromagnet layer on the second ferromagnetic layer using a sputtering method after the third step. Method of manufacturing a device
The second step is a step of forming a crystal layer of a metal oxide containing B atoms and Mg atoms by sputtering using a target consisting of a metal oxide containing B atoms and Mg atoms. The method of manufacturing a magnetoresistive element according to claim 10, wherein
The second step is a step of forming a crystalline layer of a metal oxide containing B atoms and Mg atoms by reactive sputtering using a target consisting of an alloy containing B atoms and Mg atoms and an oxidizing gas. 11. The method of manufacturing a magnetoresistive element according to claim 10, wherein
A storage medium storing a control program for causing a computer to execute a method of manufacturing a magnetoresistive element,
The manufacturing method is
A first sputtering step of forming a first ferromagnetic layer on a substrate;
A second sputtering step of forming a crystal layer containing a metal oxide containing B atoms and Mg atoms on the first ferromagnetic layer;
A third sputtering step of forming a second ferromagnetic layer on the crystal layer containing the metal oxide.
At least one of the first ferromagnetic layer and the second ferromagnetic layer has an amorphous structure,
The storage medium according to claim 16, further comprising a crystallization step of converting the amorphous structure into a crystal structure after the third sputtering step.
The storage medium according to claim 17, wherein the crystallization step comprises an annealing step.
The storage medium according to claim 16, wherein the second sputtering process is a sputtering process using a target composed of a metal oxide containing B atoms and Mg atoms.
The storage medium according to claim 16, wherein the second sputtering process is a reactive sputtering process using a target made of an alloy containing B atoms and Mg atoms and an oxidizing gas.