JPWO2010064564A1 - Magnetoresistive element, manufacturing method thereof, and storage medium used in the manufacturing method - Google Patents

Abstract

The present invention provides a magnetoresistive element having a higher MR ratio than before. One embodiment of the present invention includes a substrate (11), a first ferromagnetic layer (123) formed on the substrate (11), and a B atom formed on the first ferromagnetic layer (123). And a tunnel barrier layer (122) having a crystal structure of a metal oxide containing Mg atoms, and a magnetoresistive element comprising a second ferromagnetic layer (121) formed on the tunnel barrier layer (122). .

Description

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

JP 2003-318465 A International Publication No. 2005/088745 Pamphlet JP 2006-80116 A US Patent Application Publication No. 2006/0056115

D. D. “Applied Physics Letters”, 86,092502 (2005) by Djayapraira et al. C. L. Platt et al., “J. Appl. Phys.” 81 (8), 15 April 1997. W. H. Butler et al., “The American Physical Society” (Physical Review Vol. 63, 0544416) 8, January 2001. "Japan Journal of Applied Physics" by Shinji Yuasa et al., Vol. 43, no. 48, pp 588-590, issued April 2, 2004 S. P. Published by Parkin et al., "2004 Nature Publishing Group" Letters, pp 862-887, published October 31, 2004.

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

  In order to solve such a problem, the present invention provides a magnetoresistive element comprising 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 facing 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, wherein a first step of forming a first ferromagnetic layer on a substrate using a sputtering method and the first strong element using a sputtering method are provided. A second step of forming a crystal layer containing a metal oxide containing B atoms and Mg atoms on the magnetic layer, and a sputtering method is used to form a crystal layer containing the metal oxide on the crystal layer containing the metal oxide. And a third step of forming a second ferromagnetic layer.

  Furthermore, the present invention is a storage medium for storing a control program for causing a computer to execute a method of manufacturing a magnetoresistive element, wherein the manufacturing method forms a first ferromagnetic layer on a substrate. A sputtering step, a second sputtering step of forming 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 for forming a second ferromagnetic layer.

  According to the present invention, the MR ratio achieved by a conventional tunnel magnetoresistive element (hereinafter referred to as a TMR element) can be greatly improved. Further, the present invention can be mass-produced and has high practicality. Therefore, by using the present invention, a memory element of MRAM (Magnetic Resistive Random Access Memory) capable of 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. FIG. 3 is a block diagram of the apparatus of FIG. It is a model perspective view of MRAM comprised using the magnetoresistive element of this invention. It is an equivalent circuit diagram of MRAM comprised using the magnetoresistive element of this invention. It is sectional drawing of another tunnel barrier layer of this invention. It is a model perspective view of the columnar crystal structure concerning 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 repeated description thereof is omitted.
The magnetoresistive element of the present invention includes 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. Furthermore, you may provide the antiferromagnetic material layer located on this crystalline 2nd ferromagnetic material layer. 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 interfaced with each other. 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 typified by a metal layer (eg, Cu layer, Mg layer, Ru layer, etc.) or a metal oxide layer (eg, MgO layer, TiO ₂ layer, Al ₂ O ₃ layer, etc.). A layer may be sufficient, and the metal layer and / or the laminated body layer which laminated | stacked the metal oxide layer one layer or more may be sufficient.
In the magnetoresistive element of the present invention, the tunnel barrier layer includes 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). 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 Mg layer may be a single layer or a plurality of layers of two or more. In the case of two or more layers, a crystalline BMg oxide layer is provided between each layer.

  As described above, in the present invention, since the tunnel barrier layer of the TMR element has a crystal structure of a metal oxide containing B atoms and Mg atoms, the MR ratio is significantly higher than that of the conventional TMR element. 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) <. 1.0). In the present invention, it is preferable to use a stoichiometric amount of BMg oxide, but a high MR ratio can be obtained even if an oxygen-deficient BMg oxide is used.

  In the magnetoresistive element of the present invention, Mg layer or Mg atom was 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 Mg alloy layer) may be provided. As the Mg alloy layer, BMg is preferably used.

  The first ferromagnetic layer and the second ferromagnetic layer used in the present invention are preferably an alloy of Co, Fe, and B (hereinafter referred to as CoFeB), an alloy of Co and Fe (hereinafter referred to as CoFe). Is preferably used. Further, an alloy of Co, Fe and Ni (hereinafter referred to as CoFeNi) and an alloy of Co, Fe, Ni and B (hereinafter referred to as CoFeNiB) are also preferably used. Further, an alloy of Ni and Fe (hereinafter referred to as NiFe) is also preferably used. In the present invention, at least one kind 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 alloys different from each other.

  In the magnetoresistive element of the present invention, preferably, the first ferromagnetic layer, the tunnel barrier layer, and the second ferromagnetic layer are each composed of aggregates of columnar crystals (including needle crystals, columnar crystals, etc.). It has a polycrystalline structure formed.

FIG. 7 is a schematic perspective view of a polycrystalline structure composed of aggregates 71 of columnar crystals 72 of BMg oxide. The polycrystalline structure also includes a structure of a polycrystalline-amorphous mixed region including a partial amorphous region in the polycrystalline region. The columnar crystal is preferably a single crystal having a (001) crystal plane preferentially oriented in the film thickness direction for each column. The average diameter of the columnar single crystal is preferably 10 nm or less, and more preferably in the range of 2 nm to 5 nm. The film thickness is preferably 10 nm or less, and 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, the manufacturing method of the magnetoresistive element of this invention is demonstrated. The manufacturing method of the present invention includes the following steps. First step: A first ferromagnetic layer having an amorphous structure is formed by sputtering. Second step: A crystal layer of BMg oxide is formed on the first ferromagnetic layer by sputtering. Third step: A second ferromagnetic layer having an amorphous structure is formed on the BMg oxide crystal layer by sputtering. Fourth step: The amorphous structure of the first ferromagnetic layer and the second ferromagnetic layer is converted into a crystal structure.

  In the present invention, the first step, the second step, and the third step can each be performed using an independent sputtering apparatus (for example, a film forming chamber). For example, the first step is performed using the first sputtering device, and then the substrate is carried from the first sputtering device to the second sputtering device, where the second step is performed. Subsequently, the substrate is carried into the third sputtering apparatus from the second sputtering apparatus, and the third step is performed here. In particular, in the present invention, it is preferable that the step of forming the BMg oxide layer and the step of forming the first and second ferromagnetic layers are performed 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 a target.

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

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

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

  Next, the storage medium of the present invention will be described. The storage medium stores a control program for manufacturing the magnetoresistive element by causing the computer to execute the following steps. First sputtering step: A first ferromagnetic layer having an amorphous structure is formed. Second sputtering step: A BMg oxide crystal layer is formed on the first ferromagnetic layer. Third sputtering step: A second ferromagnetic layer having an amorphous structure is formed on the crystal 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, the second sputtering step is preferably a reactive sputtering step using a target made of the BMg oxide and an oxidizing gas. As the oxidizing gas, oxygen gas, ozone gas, water vapor or the like is preferably used.

  Examples of the storage medium of the present invention include a hard disk medium, a magneto-optical disk medium, a floppy (registered trademark) disk medium, and non-volatile memories such as flash memory and MRAM, and includes a medium that can store a program.

Hereinafter, preferred embodiments of the present invention will be described in detail.
FIG. 1 shows an example of the laminated structure of the top type magnetoresistive element 10 of the present invention, and shows the laminated structure of the magnetoresistive element 10 using the TMR element 12. The magnetoresistive element 10 includes the TMR element 12 formed on the substrate 11. The top type magnetoresistive element 10 includes, for example, a nine-layer multilayer film including the TMR element 12. This nine-layered multilayer film has a multilayered film structure that is directed from the lowermost first layer (Ta layer) to the uppermost ninth layer (Ru layer). Specifically, the magnetic layer and the nonmagnetic Ru layer in the order of CoFeB layer, nonmagnetic BMg oxide layer, CoFeB layer, nonmagnetic Ru layer, CoFe layer, antiferromagnetic material layer PtMn layer, nonmagnetic Ta layer, and nonmagnetic Ru layer. A magnetic layer is laminated. In addition, the numerical value in the bracket | parenthesis of each layer shows the thickness of each layer, and a unit is nm. The said thickness is an example and is not limited to this. 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 having a first ferromagnetic layer 123, a tunnel barrier layer 122, and a second ferromagnetic layer 121. Reference numeral 13 denotes a lower electrode layer (underlayer) of the first layer (Ta layer), and reference numeral 14 denotes an antiferromagnetic layer of a seventh layer (PtMn layer). Reference numeral 15 denotes a ferromagnetic layer of the sixth layer (CoFe layer), reference numeral 16 denotes a nonmagnetic material layer for exchange coupling of the fifth layer (Ru layer), and reference numeral 121 denotes a fourth layer (crystalline CoFeB layer). This is a ferromagnetic layer. A layer including the fourth layer 121, the fifth layer 16, and the sixth layer 15 is a magnetization fixed layer 19. The substantial magnetization fixed layer 19 is a ferromagnetic layer 121 made of a fourth crystalline CoFeB layer, and corresponds to the second ferromagnetic layer according to the present invention.

  Reference numeral 122 denotes a tunnel barrier layer of a third layer (polycrystalline BMg oxide), which is an insulating layer. The tunnel barrier layer 122 according to the present invention may be a single polycrystalline BMg oxide layer.

  Further, as illustrated in FIG. 6, the present invention includes a polycrystalline BMg oxide layer as the tunnel barrier layer 122, such as a crystalline BMg layer such as a microcrystal, a polycrystal, or a single crystal, or an Mg layer 1222. An alloy layer containing Mg atoms and Mg atoms or Mg atoms may be provided. In this case, a stacked structure in which polycrystalline BMg oxide layers 1221 and 1223 are provided on both sides of the BMg layer or the Mg layer 1222 is employed. Furthermore, the BMg layer or the Mg layer 1222 illustrated in FIG. 6 can be formed into a plurality of layers of two or more layers, and an alternate layer in which the BMg oxide layers are alternately stacked.

  FIG. 8 is an example of another TMR element 12 of the present invention. Reference numerals 12, 121, 122, and 123 in FIG. 8 are the same members as in FIG. In this example, the tunnel barrier layer 122 is a laminated film in which a BMg oxide layer 82 and BMg layers or Mg layers 81 and 83 on both sides of the layer 82 are laminated. 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 a Mg layer and the layer 83 may be a layer BMg layer. In the present invention, the use of the above-described layer 81 can be omitted, and the layer 82 can be disposed adjacent to the crystalline ferromagnetic layer 123. Alternatively, the use of the above-described layer 83 can be omitted, and the layer 82 can be replaced with the second layer 82. The ferromagnetic layer 121 can be disposed adjacent to the ferromagnetic layer 121. As described above, in the embodiment shown in FIG. 8, either one between the first ferromagnetic layer 123 and the BMg oxide layer 82 and between the second ferromagnetic layer 121 and the BMg oxide layer 82. Further, a metal layer made of Mg atoms or an alloy layer containing Mg atoms is provided.

  In FIG. 1, reference numeral 123 denotes a second layer (CoFeB layer) crystalline ferromagnetic 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 using 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 laminated without breaking the vacuum.

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

  Among the magnetization fixed layers, the ferromagnetic layer 121 (CoFeB layer) which is the fourth layer, the third layer (polycrystalline BMg oxide layer) which is the tunnel barrier layer 122, and the second layer which is the magnetization free layer are strong. 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 columnar crystal structure 71 shown in FIG.

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

  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 a sputtering method. In this apparatus 200, a transfer chamber 202 provided with a robot transfer apparatus (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 magnetoresistive element, and the substrate (for example, silicon substrate) 11 is carried in and out, respectively. . By alternately loading and unloading the substrate by these 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 film forming magnetron sputtering chambers 201 </ b> A to 201 </ b> C and one etching chamber 203 are provided around a transfer chamber 202. In the etching chamber 203, a required surface of the TMR element 10 is etched. A gate valve 204 that can be opened and closed is provided between each of the chambers 201A to 201C and 203 and the transfer chamber 202. Each chamber 201A to 201C and 202 is provided with an unillustrated evacuation mechanism, gas introduction mechanism, power supply mechanism, and the like. The film forming magnetron sputtering chambers 201A to 201C can sequentially deposit the above-described first to ninth layers on the substrate 11 without breaking the vacuum using a high-frequency sputtering method. it can.

  Four or five cathodes 31 to 35, 41 to 45, 51 to 54 are arranged on an appropriate circumference on the ceiling of the magnetron sputtering chambers 201A to 201C for film formation. Further, the substrate 11 is disposed on a substrate holder located coaxially with the circumference. Further, a magnetron sputtering apparatus in which a magnet is disposed behind the targets mounted on the cathodes 31 to 35, 41 to 45, 51 to 54 is preferable.

  In the apparatus, high-frequency power such as a 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 the high frequency power, a frequency in the range of 0.3 MHz to 10 GHz, preferably a frequency in the range of 5 MHz to 5 GHz and a power in the range of 10 W to 500 W, preferably in the range of 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 is attached to the cathode 32, a CoFeB target is attached to the cathode 33, a CoFe target is attached to the cathode 34, and a Ru target is attached to the cathode 35. 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 together with an oxidizing gas can be connected to the transfer chamber 202.

  Further, after forming a polycrystalline BMg layer by sputtering using a BMg target, the polycrystalline BMg oxide is formed in an oxidation chamber (not shown) using an oxidizing gas (for example, oxygen gas, ozone gas, water vapor, etc.). Chemical changes can be made to the layer.

  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, no target can 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 mounted on the cathode 51, and a Ta target is mounted on the cathode 52. The cathode 53 is not mounted with a target. In addition, the cathode 54 has no target mounted on it.

  The in-plane directions 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 this non-parallel arrangement and sputtering while rotating a target having a diameter smaller than the substrate diameter, a magnetic film and a nonmagnetic film having the same composition as the target composition can be deposited with high efficiency. 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, or preferably 0.2 times. Or 0.5 times.

  In the non-parallel arrangement, for example, they 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 °. Further, the substrate at this time can use a rotation speed of 10 rpm to 500 rpm, preferably a rotation 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 film forming magnetron sputtering chamber 201A, and reference numeral 303 denotes a film forming chamber corresponding to the film forming magnetron sputtering chamber 201B. 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 / unload lock chamber corresponding to the load lock / unload lock chambers 205 and 206. Reference numeral 306 denotes a central processing unit (CPU) having a storage medium 312 built therein. Reference numerals 309 to 311 denote bus lines that connect 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. This substrate carry-out process is calculated based on a control program as a computer-executable program stored in the storage medium 312 by the CPU 306. The CPU 306 transmits a control signal based on the calculation result to the various devices mounted on the load lock / unload lock chamber 305 and the transfer chamber 301 through the bus lines 307 and 311. That is, the substrate carry-out process is performed by the CPU 306 controlling the execution of the various apparatuses by the control signal. Examples of the various devices include a gate valve (not shown), a robot mechanism, a transport mechanism, and a drive system, and the storage medium 312 corresponds to the storage medium of the present invention described above.

  The substrate transferred to the transfer chamber 301 is transferred to the film formation 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 above-described stacking process, the CPU 306 has various control signals calculated based on the control program stored in the storage medium 312 in the CPU 306 mounted on the transfer chamber 301 and the film forming chamber 304 through the bus lines 307 and 310. Send to device. That is, the CPU 306 controls the execution of the various apparatuses by the control signal in the transfer of the substrate to the film forming chamber 304 by the transfer chamber 301 and the film formation of the first layer 13 and the second layer 123 by the film forming chamber 304. It is carried out. Examples of such various devices include a power supply 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, and a drive system.
As described above, the CPU 306 controls the film forming chamber 304 according to the control program 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 once returned to the transfer chamber 301 and then transferred into the film formation chamber 303. In the film formation 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 film formation of the third layer 122, the CPU 306 sends a control signal calculated based on a control program stored in the storage medium 312 in the CPU 306 through the bus lines 307 and 309 and the transfer chamber 301 and the film formation chamber. The information is transmitted to various devices mounted on the terminal 303. That is, the transfer of the substrate to the film formation chamber 303 by the transfer chamber 301 and the film formation of the third layer 122 by the film formation chamber 303 are performed by the CPU 306 controlling the execution of the various apparatuses by 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, and a drive system.
As described above, the CPU 306 controls the film forming chamber 303 according to the control program to form the third layer 122 as the tunnel barrier layer on the second layer 123.

  The substrate stacked up to the third layer 122 is once again returned to the transfer chamber 301 and then transferred into the film formation chamber 302. In the deposition 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 stacking up to the ninth layer, the CPU 306 sends a control signal calculated based on a control program stored in the storage medium 312 in the CPU 306 through the bus lines 307 and 308 and the transfer chamber 301 and the film forming chamber 302. It is transmitted to various devices mounted on. That is, the transfer of the substrate to the film forming chamber 302 by the transfer chamber 301 and the film formation from the fourth layer 121 to the ninth layer 18 by the film forming chamber 302 are controlled by the CPU 306 according to 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, and a drive system.

  As described above, the CPU 306 controls the film forming chamber 302 according to the control program to form the fourth layer 121 as the second ferromagnetic layer on the third layer 122, and further, the fourth layer 121. A fifth layer 16 to a ninth layer 18 are sequentially formed thereon.

  Examples of the storage medium 312 of the present invention include a hard disk medium, a magneto-optical disk medium, a floppy (registered trademark) disk medium, and non-volatile memories such as flash memory and MRAM as described above, and can store programs. Includes media.

  In order to promote polycrystallization by annealing the amorphous CoFeB layers of the fourth layer 121 and the second layer 123, and to promote magnetism of the antiferromagnetic material PtMn layer of the seventh layer 14, the first to ninth layers The laminated film composed 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, various devices in the annealing furnace (for example, a heater mechanism, an exhaust mechanism, a transport mechanism, etc., not shown) are controlled by the control signal obtained by the calculation of the CPU 306 based on the control program, and the annealing process is executed. Can do. 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 control the second layer 123 and / or the amorphous structure of the fourth layer 121 can be converted into a crystal structure.

  In the present invention, as the fourth layer 121 and the second layer 123, other alloy layers can be used 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, a FeTaN layer, or a FeC layer can be used.

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

  Furthermore, in the present invention, each alloy layer such as an IrMn layer, an IrMnCr layer, a NiMn layer, a PdPtMn layer, a RuRhMn layer or an OsMn layer is preferably used in place of the PtMn layer of the seventh layer 14. 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-layer film of a polycrystalline CoFeB layer and a polycrystalline CoFe layer (located on the antiferromagnetic layer 14 side). In this case, the polycrystalline CoFe layer located on the antiferromagnetic layer 14 side can be deposited in a polycrystalline state on the fourth BMgO layer by sputtering.

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

  FIG. 4 is a schematic diagram 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 a plurality of word lines 403 and a plurality of bit lines 404, and is arranged in a lattice-like positional relationship. Each of the large number of memory elements 402 can store 1-bit information.

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

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

  The ferromagnetic layer 123 is formed by using a target having a CoFeB composition ratio (atomic ratio) of 60/20/20, an Ar gas pressure of 0.03 Pa, and a sputtering rate of 0.64 nm / sec by magnetron DC sputtering (chamber 201C). Filmed. The CoFeB layer (ferromagnetic material layer 123) at this time had an amorphous structure. Subsequently, the sputtering apparatus (chamber 201B) was changed. A target having a BMgO composition ratio (atomic ratio) of 25/25/50 was used, and the pressure of the sputtering gas was set to 0.2 Pa in the pressure range of 0.01 to 0.4 Pa. Under this condition, a tunnel barrier layer 122 which is a sixth BMg oxide 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. Further, the deposition rate of magnetron RF sputtering (13.56 MHz) at this time was 0.14 nm / sec.

Subsequently, instead of the sputtering apparatus (chamber 201A), a ferromagnetic layer 121 that is a magnetization fixed layer (fourth CoFeB layer) was formed. The fourth CoFeB layer (ferromagnetic material layer 121) was confirmed to have an amorphous structure.
Subsequently, the fifth layer Ru layer 16, the sixth layer CoFe layer 15, the seventh layer PtMn layer 14, the eighth layer Ta layer 17 and the fourth layer 121 are formed on the fourth layer 121. Nine Ru layers 18 were continuously formed in the chamber 201A without breaking the vacuum state to form a laminate film.

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

  The magnetoresistive element 10 that has been deposited by sputtering in each of the film forming magnetron sputtering chambers 201A to 201C is subjected to an annealing process in a magnetic field of 8 kOe in a heat treatment furnace at about 300 ° C. for 4 hours. Carried out. As a result, it was confirmed that the second and fourth CoFeB layers having an amorphous structure had a polycrystalline structure composed of aggregates 71 of columnar crystals 72 shown in FIG. By this annealing step, the magnetoresistive element 10 can act as a magnetoresistive element having a TMR effect. In addition, by the annealing process, predetermined magnetization was imparted to the antiferromagnetic material layer 14 which is the seventh PtMn layer.

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

  The MR ratio of the magnetoresistive element of the example and the magnetoresistive element of the comparative example was measured and compared. As a result, the MR ratio of the example was a numerical value that was 1.2 to 1.5 times the MR ratio of the comparative example. It was improved with. Thus, according to the present example, the MR ratio can be increased because the crystal structure of the metal oxide containing B atoms and M atoms is used as the tunnel barrier layer of the TMR element.

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).

  MR ratio is a parameter related to the magnetoresistive effect in which the electrical 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. Resistance change rate (MR ratio).

Claims (20)

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 located on the side of the crystalline first ferromagnetic layer facing the substrate;
A magnetoresistive element comprising: a crystalline second ferromagnetic layer located on a side of the tunnel barrier layer facing the crystalline first ferromagnetic layer.   The magnetoresistive element according to claim 1, further comprising an antiferromagnetic material layer positioned on a side of the crystalline second ferromagnetic layer facing the tunnel barrier layer.   2. The magnetoresistive element according to claim 1, wherein in the tunnel barrier layer, a content of B atoms in the metal oxide is 30 atomic% or less. The tunnel barrier layer is
Furthermore, it has an alloy layer containing B atoms and Mg atoms or a metal layer made of Mg atoms,
2. The magnetoresistive element according to claim 1, wherein the magnetoresistive element is a laminated film having a metal oxide crystal layer containing B atoms and Mg atoms on both sides of the alloy layer or the metal layer.   2. The magnetoresistive element according to claim 1, wherein a metal layer made of Mg atoms or an alloy layer containing Mg atoms is provided between the crystalline first ferromagnetic layer and the tunnel barrier layer.   6. The magnetoresistive element according to claim 5, wherein the alloy layer containing Mg atoms is an alloy layer containing Mg atoms and B atoms.   2. The magnetoresistive element according to claim 1, wherein a metal layer made of Mg atoms or an alloy layer containing Mg atoms is provided 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.   2. The magnetism 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 aggregate 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 crystal layer containing a metal oxide containing B atoms and Mg atoms on the first ferromagnetic layer using a sputtering method;
A third step of forming a second ferromagnetic layer on the crystal layer containing the metal oxide using a sputtering method;
A method of manufacturing a magnetoresistive element, comprising: At least one of the first ferromagnetic layer and the second ferromagnetic layer has an amorphous structure,
The method of manufacturing a magnetoresistive element according to claim 10, further comprising a 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 magnetoresistive device according to claim 10, further comprising a step of forming an antiferromagnetic layer on the second ferromagnetic layer by sputtering after the third step. Device manufacturing method.   The second step is a step of forming a metal oxide crystal layer containing B atoms and Mg atoms by sputtering using a target made of a metal oxide containing B atoms and Mg atoms. The method of manufacturing a magnetoresistive element according to claim 10.   The second step is a step of forming a metal oxide crystal layer containing B atoms and Mg atoms by reactive sputtering using a target composed of an alloy containing B atoms and Mg atoms and an oxidizing gas. The method of manufacturing a magnetoresistive element according to claim 10, wherein the magnetoresistive element is provided. A storage medium for storing a control program for causing a computer to execute a method of manufacturing a magnetoresistive element,
The manufacturing method includes:
A first sputtering step of forming a first ferromagnetic layer on the 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;
And 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 includes an annealing step.   The storage medium according to claim 16, wherein the second sputtering step is a sputtering step using a target made of a metal oxide containing B atoms and Mg atoms.   The storage medium according to claim 16, wherein the second sputtering step is a reactive sputtering step using a target made of an alloy containing B atoms and Mg atoms and an oxidizing gas.

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