JP2012124185A - Magnetoresistive element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetoresistive element having an MR ratio higher than the conventional MR ratios.SOLUTION: The present invention relates to a magnetoresistive element used for a magnetic reproducing head for a magnetic disc driving device, a storage element for magnetic random access memory, and a magnetic sensor, and preferably to a tunnel magnetoresistive element (more preferably, a spin-valve-type tunnel magnetoresistive element). The magnetoresistive element comprises: a substrate; a tunnel barrier layer; a ferromagnetic layer comprising a Co (cobalt)-Fe (iron) alloy; and a nonmagnetic metal layer containing B (boron).

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 (more preferably, a spin valve type tunnel magnetoresistive element). About.

Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, Patent Document 6, Non-Patent Document 1, and Non-Patent Document 2 include a tunnel barrier layer and a first installed on both sides of the tunnel barrier layer. A TMR (Tunneling Magneto Resistance) element (hereinafter referred to as a TMR element) composed of one and second ferromagnetic layers is described, and the first and / or second ferromagnetic layers constituting this element are described. CoFeB alloys containing Co (cobalt) atoms, Fe (iron) atoms, and B (boron) atoms are used. Moreover, the thing of a polycrystalline structure is described as the above-mentioned CoFeB alloy layer.

JP 2002-204004 A International publication number is WO2005 / 088745 JP 2003-304010 A JP 2006-080116 A US 2006/0056115 publication US Pat. No. 7,252,852

D. D. “Applied Physics Letters”, 86,092502 (2005) by Djayapraira et al. "Japan Journal of Applied Physics" by Shinji Yuasa et al., Vol. 43, no. 48, pp 588-590, issued April 2, 2004

An object of the present invention is to provide a magnetoresistive element (tunnel magnetoresistive element, more preferably a spin valve tunnel magnetoresistive element, etc.) having a further improved high MR ratio compared to the prior art. is there.

  The present invention firstly features a magnetoresistive element having a nonmagnetic metal layer containing a substrate, a tunnel barrier layer, a ferromagnetic layer, and B (boron; hereinafter referred to as “B”).

Secondly, the present invention provides a magnetization fixed layer having a substrate, an antiferromagnetic layer, a ferromagnetic layer, and a nonmagnetic metal layer containing B, a magnetic free layer having a magnetic layer and a nonmagnetic metal containing B, and The magnetoresistive element has a tunnel barrier layer containing a metal oxide located between the magnetization fixed layer and the magnetization free layer.

According to the present invention, the MR ratio achieved with the conventional TMR element can be greatly improved.

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 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. It is a cross-sectional schematic diagram of another example of the magnetoresistive element of this invention. It is a cross-sectional schematic diagram of another example of the magnetoresistive element of this invention.

A ferromagnetic layer can be used for the magnetization free layer and the magnetization fixed layer of the present invention. As the ferromagnetic material used in the ferromagnetic layer, an alloy composed of Co, Fe and B (hereinafter referred to as CoFeB) and an alloy of Co and Fe (hereinafter referred to as CoFe) are preferably used. Further, an alloy composed of Co, Fe and Ni (hereinafter referred to as CoFeNi) and an alloy composed 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.

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

FIG. 6 is a schematic perspective view of a polycrystalline structure composed of aggregates 61 of columnar crystals 62 of Mg oxide used as a tunnel barrier layer. The polycrystalline structure also includes a structure of a polycrystalline-amorphous mixed region including a partial amorphous region in the polycrystalline region. The column crystal is preferably a single crystal in which (001) crystal planes are preferentially oriented in the film thickness direction for each column. The average diameter of the columnar single crystal is preferably 10 nm or less, more preferably in the range of 2 nm to 5 nm, and the film thickness is preferably 10 nm or less, more preferably 0.5 nm. It is in the range of 5 nm.

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: An antiferromagnetic layer is formed by sputtering. Second step: A sputtering method is used to form an amorphous ferromagnetic layer on the antiferromagnetic layer, and a B-containing nonmagnetic metal layer is formed on the ferromagnetic layer. A ferromagnetic layer having an amorphous structure is formed on the nonmagnetic metal layer, and a magnetization fixed layer formed of a multilayer film composed of a plurality of these layers is formed. Third step: A sputtering method is used to form a tunnel barrier layer made of a crystalline layer of Mg oxide on the magnetization fixed layer. Fourth step: Using a sputtering method, a ferromagnetic layer having an amorphous structure is formed on the tunnel barrier layer, and a non-magnetic metal layer containing B is formed on the ferromagnetic layer. A ferromagnetic layer having an amorphous structure is formed on the nonmagnetic metal layer, and a magnetization free layer formed of a multilayer film composed of a plurality of these layers is formed. Fifth step: After the fourth step, an annealing process using a heater such as a lamp heater device or an ultrasonic heating device is applied to fix the magnetic field of the magnetization fixed layer. The body layer can be converted to a crystalline ferromagnetic layer. As a result, the MR ratio could be greatly improved.

The annealing process used in the present invention is performed at 200 ° C. to 300 ° C. (preferably 230 ° C. to 250 ° C.) for 1 hour to 6 hours (preferably 2 hours 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 third step according to the present invention is preferably a step of forming a crystalline layer of Mg oxide by sputtering using a target made of Mg oxide. 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. In the present invention, in the third step, a metal Mg target can be used instead of the target made of Mg oxide. The metal Mg layer formed by sputtering can obtain an Mg oxide layer by oxidizing metal Mg under an oxidizing gas such as oxygen gas, ozone gas or water vapor. The Mg oxide layer can contain a trace amount of B.

Next, another method for manufacturing the magnetoresistive element of the present invention will be described. Another manufacturing method of the present invention includes the following steps. First step: An antiferromagnetic layer is formed by sputtering. Second step: Using a sputtering method, a ferromagnetic layer having an amorphous structure is formed on the antiferromagnetic layer, a nonmagnetic metal layer is formed on the ferromagnetic layer, and the nonmagnetic metal is formed. On the layer, a B-containing ferromagnetic layer having an amorphous structure is formed, and a magnetization fixed layer formed of a multilayer film composed of a plurality of these layers is formed. Third step: A sputtering method is used to form a tunnel barrier layer made of a crystalline layer of Mg oxide on the magnetization fixed layer. Fourth step: A sputtering method is used to form a B-containing ferromagnetic layer having an amorphous structure on the tunnel barrier layer, and a nonmagnetic metal layer is formed on the ferromagnetic layer. Then, a ferromagnetic layer having an amorphous structure is formed on the nonmagnetic metal layer, and a magnetization free layer formed of a multilayer film composed of a plurality of these layers is formed. Fifth step: After completion of the fourth step, an annealing process (200 ° C. to 300 ° C., preferably 230 ° C.) using a heater such as a lamp heater device or an ultrasonic heating device to fix the magnetic field of the magnetization fixed layer. At 250 ° C. for 1 hour to 6 hours, preferably 2 hours to 5 hours), during this annealing, the amorphous structure ferromagnetic layer is converted to a crystalline structure ferromagnetic layer. Sixth step: After completion of the fifth step, annealing sufficient for solid-phase diffusion of B in the ferromagnetic layer to the nonmagnetic metal layer (at a temperature of 340 ° C. or higher, preferably at a high temperature of 350 ° C. to 360 ° C., (Several minutes to several hours, preferably 30 minutes to 2 hours).

Hereinafter, preferred embodiments of the present invention will be described in detail.

FIG. 1 shows an example of the laminated structure of the magnetoresistive element 10 of the present invention, and shows the laminated structure of the magnetoresistive element 10 using the TMR element 12. According to the magnetoresistive element 10, a TMR element 12 is used on a substrate 11, and for example, a multilayer film including nine layers is formed 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, a magnetic layer and a nonmagnetic layer in the order of a PtMn layer, a CoFe layer, a nonmagnetic BRu alloy layer, a CoFe alloy layer, a nonmagnetic Mg oxide layer, a CoFe alloy layer, a nonmagnetic BTa alloy layer, and a nonmagnetic Ru layer. Layers are stacked. 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 PtMn layer is an alloy layer containing Pt and Mn.

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

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

FIG. 7 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 including the Mg oxide layer 72 and the metal Mg layers 71 and 73 on both sides of the layer 72. In the present invention, the use of the above-described layer 71 can be omitted, and the layer 72 can be disposed adjacent to the crystalline ferromagnetic layer 123. Alternatively, the use of the above-described layer 73 can be omitted, and the layer 72 can be replaced with the second layer 72. The ferromagnetic layer 121 can be disposed adjacent to the ferromagnetic layer 121.

In FIG. 1, reference numeral 123 denotes a seventh layer (CoFe alloy layer) crystalline ferromagnetic layer, which is a magnetization free layer and corresponds to the second ferromagnetic layer according to the present invention. In addition to the above, the seventh layer 123 may be a crystalline ferromagnetic layer using polycrystalline NiFe made of an aggregate of columnar crystals. The ferromagnetic layer 123 of the magnetization free layer can function as a recording layer when applied as an MRAM.

The crystalline ferromagnetic layers 121 and 123 are preferably provided adjacent to the tunnel barrier layer 122 located in the middle. In the manufacturing apparatus, these three layers are sequentially laminated without breaking the vacuum.

Reference numeral 17 denotes a nonmagnetic metal layer of an eighth layer (BTa alloy layer), which can also function as an electrode. The 18th (9th Ru layer) is hard when a multilayer film composed of layer 13, layer 14, layer 15, layer 16, layer 121, layer 122, layer 123 and layer 17 is used for pattern formation by dry etching. It is a mask layer. The ninth layer hard mask may be removed from the magnetoresistive element.

The ferromagnetic layer 121 (CoFe alloy layer) which is the fifth layer of the magnetization fixed layer, the sixth layer (polycrystalline Mg oxide layer) which is the tunnel barrier layer 122, and the seventh layer which is the magnetization free layer The TMR element 12 is formed by the ferromagnetic layer 123 (CoFe alloy layer).

The tunnel barrier layer 122 (Mg oxide layer), the crystalline ferromagnetic layer 121 (CoFe alloy layer), and the crystalline ferromagnetic layer 123 may have the columnar crystal structure 61 illustrated in FIG. preferable.

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 between these load lock / unload lock chambers 205 and 206, the tact time is shortened and a 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 includes
A vacuum exhaust mechanism, a gas introduction mechanism, a power supply mechanism, and the like (not shown) are attached. 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 mounted on the cathode 31, a PtMn target is mounted on the cathode 32, a CoFe alloy target is mounted on the cathode 33, a CoFe alloy target is mounted on the cathode 34, and a BRu alloy target is mounted on the cathode 35. The The cathode 41 is equipped with an Mg oxide target or an Mg target. When using the Mg target, a reactive sputtering chamber (not shown) for performing reactive sputtering together with an oxidizing gas can be connected to the transfer chamber 202.

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

A CoFe alloy target is mounted on the cathode 51, a BTa alloy target is mounted on the cathode 52, and a BRu alloy target is mounted on the cathode 53. Further, the cathode 54 can be unmounted with a target, or can be appropriately mounted with a CoFe alloy target, Ta target, or Ru target for reserve.

The in-plane directions of the targets mounted on the cathodes 31 to 35, 41 to 45, and 51 to 54 are preferably arranged non-parallel to the in-plane direction of the substrate. By using the non-parallel arrangement, sputtering can be performed while rotating a target having a diameter smaller than the substrate diameter, so that a magnetic film and a nonmagnetic film having the same composition as the target composition can be deposited.

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, 301 is a transfer chamber corresponding to the transfer chamber 202 in FIG. 2, 302 is a film forming chamber corresponding to the film forming magnetron sputtering chamber 201A, and 303 is a film forming chamber corresponding to the film forming magnetron sputtering chamber 201B. is there. 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 built-in storage medium 312. 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 unloading step is calculated based on a control program stored in the storage medium 312 by the CPU 306. A control signal based on the calculation result is executed by controlling the execution of various devices mounted in the load lock / unload lock chamber 305 and the transfer chamber 301 through the bus lines 307 and 311. 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, the second layer 14, the third layer 15, the fourth layer 16, and the fifth layer 121 of FIG. 1 are sequentially stacked on the substrate carried into the deposition chamber 302. The CoFe alloy layer of the fifth layer 121 at this stage preferably has an amorphous structure, but may have a polycrystalline structure.

In the stacking process, control signals calculated based on the control program stored in the storage medium 312 in the CPU 306 execute various apparatuses mounted on the transfer chamber 301 and the film forming chamber 302 through the bus lines 307 and 308. Implemented by controlling. 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.

The substrate having the laminated film up to the fifth layer is once returned to the transfer chamber 301 and then transferred into the film formation chamber 303. In the film forming chamber 303, a polycrystalline Mg oxide layer is formed as the sixth layer 122 on the amorphous CoFe alloy layer of the fifth layer 121. In the film formation of the sixth layer 122, a control signal calculated based on the control program stored in the storage medium 312 in the CPU 306 is mounted on the transfer chamber 301 and the film formation chamber 303 through the bus lines 307 and 309. Implemented by controlling the execution of various devices. 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.

The substrate stacked up to the sixth layer 122 is once again returned to the transfer chamber 301 and then transferred into the film formation chamber 304. In the deposition chamber 304, the seventh layer 123, the eighth layer 17, and the ninth layer 18 are sequentially stacked on the polycrystalline Mg oxide layer of the sixth layer 122. The CoFe alloy layer of the seventh layer 123 at this stage preferably has an amorphous structure, but may have a polycrystalline structure.

In the stacking up to the ninth layer, various control signals calculated based on the control program stored in the storage medium 312 in the CPU 306 are mounted on the transfer chamber 301 and the film forming chamber 304 through the bus lines 307 and 310. This is done by controlling the execution of the device. 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.

Examples of the storage medium 312 of the present invention include hard disk media, magneto-optical disk media, flexible disk media, and non-volatile memories such as flash memory and MRAM as described above, and include media that can store programs. .

In order to promote polycrystallization by annealing the amorphous CoFe alloy layers of the fifth layer 121 and the seventh layer 123, and to promote the magnetic application of the PtMn layer of the second layer 14, the first layer to the ninth layer are formed. The laminated film 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.

In the present invention, as the fifth layer 121 and the seventh layer 123, other alloy layers can be used instead of the above-mentioned CoFe alloy layer. Specifically, a polycrystalline ferromagnetic layer such as a CoFeB layer, 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, the same effect was obtained even when a nonmagnetic transition metal containing B such as a BRh layer or a BIr layer was used instead of the BRu layer of the fourth layer 16, but in addition to these, Even if at least one selected from the group of non-magnetic transition metals comprising B, Ti, V, Cu, Y, Zr, Nb, Mo, Pd, Hf, Ta, W, Ta, Te and the like is used. The effect of was obtained. In the present invention, the B content in the fourth layer 16 can be set in the range of 10 atomic% to 40 atomic%. Further, in place of the BTa alloy layer of the eighth layer 17, a nonmagnetic transition metal comprising Ru, Rh, Ir, Y, Ti, Zr, Hf, V, Mo, W, Te, Ta and Ru containing B The same effect was obtained even when at least one selected from the group was used. In the present invention, the B content in the eighth layer 17 can be set in the range of 10 atomic% to 40 atomic%.

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 instead of the PtMn layer of the second layer 14. The film thickness is preferably 10 to 30 nm.

In the present invention, the fifth layer 121 can be a laminated film including a polycrystalline CoFe alloy layer and a polycrystalline CoFeB layer (located on the substrate side).

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, 402 is a memory element of the present invention, 403 is a word line, and 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 including the TMR element 10 that stores 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.

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 121 was formed by magnetron DC sputtering (chamber 201A) at a Ar gas pressure of 0.03 Pa using a target having a CoFe composition ratio (atomic ratio) of 60/40. Subsequently, the sputtering apparatus (chamber 201B) was changed. A target having an MgO composition ratio (atomic ratio) of 50/50 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 Mg oxide layer was formed by magnetron RF sputtering (13.56 MHz). At this time, the Mg 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 201C), a ferromagnetic layer 123 that is a magnetization free layer (seventh CoFe alloy layer) was formed.

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

As a comparative example of the present invention, a similar magnetoresistive element was prepared except that the fourth layer 16 was replaced with a metal Ru layer and the tenth layer 17 was replaced with a metal Ta layer.

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.

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).

FIG. 8 shows an example of a laminated structure of the top type magnetoresistive element 80 of the present invention. The laminated structure of the magnetoresistive element 80 using the TMR element 82 is shown and is the same as the TMR element 12 of FIG. According to this magnetoresistive element 80, a TMR element 82 is used on a substrate 81, and for example, a multilayer film of nine layers is formed including the TMR element 82. This nine-layered multilayer film has a multilayered film structure from the lowermost first layer (BTa alloy layer) 83 to the uppermost ninth layer (Ru layer) 88. Specifically, the CoFe layer 823, the nonmagnetic Mg oxide layer 822, the CoFe layer 821, the nonmagnetic BRu alloy layer 86, the CoFe layer 85, the antiferromagnetic material layer PtMn layer 84, the nonmagnetic Ta layer 87, and the nonmagnetic Ru A magnetic layer and a nonmagnetic layer are laminated in the order of the layer 88. 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. 8, reference numeral 81 denotes a substrate such as a wafer substrate, a glass substrate, or a sapphire substrate. A TMR element 82 is constituted by a first ferromagnetic layer 823, a tunnel barrier layer 822, and a second ferromagnetic layer 821. Reference numeral 83 denotes an alloy layer of the first layer (BTa layer), which can be used as a lower electrode layer (underlayer). Reference numeral 84 denotes an antiferromagnetic layer of the seventh layer (PtMn layer). 85 is a ferromagnetic layer of the sixth layer (CoFe layer), 86 is a nonmagnetic layer for exchange coupling of the fifth layer (BRu alloy layer), and 121 is a ferromagnetic body of the fourth crystalline CoFe layer) The layer composed of the fourth layer 821, the fifth layer 86, and the sixth layer 85 is a magnetization fixed layer 89. The substantial magnetization fixed layer 89 is a ferromagnetic layer 821 made of a fourth crystalline CoFe layer, and corresponds to the second ferromagnetic layer according to the present invention.

Reference numeral 822 denotes a tunnel barrier layer of a third layer (polycrystalline Mg oxide), which is an insulating layer. The tunnel barrier layer 822 according to the present invention may be a single polycrystalline BMg oxide layer. Further, even when the second layer CoFe layer 823 is a CoFeB alloy layer and the fourth layer CoFe821 is a CoFeB alloy layer, the same effect as that of the element of FIG. 8 can be obtained.

  FIG. 9 shows an example of the laminated structure of the magnetoresistive element 90 according to the present invention, and shows the laminated structure of the magnetoresistive element 90 using the TMR element 92. According to the magnetoresistive element 90, for example, a 12-layer multilayer film including the TMR element 92 is formed on the substrate 91. This 12-layer multilayer film has a multilayer film structure from the lowermost first layer (Ta layer) to the uppermost twelfth layer (Ru layer). Specifically, a PtMn layer 94, a CoFe layer 95, a nonmagnetic metal layer (BRu alloy) layer 961, a CoFe layer 921 as a first ferromagnetic layer, and a nonmagnetic polycrystalline Mg oxide layer 922 as a tunnel barrier layer. Are stacked. Furthermore, a polycrystalline CoFe layer 9233 that is a second ferromagnetic layer, a nonmagnetic BTa alloy layer 962, a polycrystalline CoFe layer 9232 that is a third ferromagnetic layer, and a polycrystalline NiFe layer 9231 are stacked thereon. . Furthermore, a nonmagnetic Ta layer 97 and a nonmagnetic Ru layer 98 are stacked in this order. 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.

  In the present invention, the first ferromagnetic layer 921 may have a laminated structure of two or more layers in which a CoFe layer and another ferromagnetic layer (for example, a CoFeB alloy, a CoFeNi alloy, etc.) are added.

  Reference numeral 91 denotes a substrate such as a wafer substrate, a glass substrate, or a sapphire substrate.

  Reference numeral 92 denotes a TMR element, which is composed of a laminated structure of a first ferromagnetic layer 921, a tunnel barrier layer 922, a second ferromagnetic layer 9233, and third ferromagnetic layers 9232 and 9231 made of polycrystalline CoFe. . The tunnel barrier layer 922 has a polycrystalline Mg oxide layer or a polycrystalline Mg oxide layer, and is composed of a second ferromagnetic layer 9232 polycrystalline CoFe layer. The third ferromagnetic layer is composed of a laminated film of a polycrystalline CoFe layer 9232 and a polycrystalline NiFe layer 9231.

A BTa alloy intermediate layer 962 made of a nonmagnetic metal containing B is disposed between the second ferromagnetic layer 9233 and the third ferromagnetic layer 9232.
Also, the second PtMn layer 94 may be a PtMnB alloy layer, the third and fifth CoFe layers 95 and the CoFe layer 921 may be CoFeB alloy layers, and the sixth MgO layer 922. 9 may be a BMgO alloy oxide layer, and even if the seventh CoFe layer 9233 is a CoFeB alloy layer, the same effects as those of the device of FIG. 9 can be obtained.

In the present invention, as the nonmagnetic transition metal used in the intermediate layers 16, 86, 961 and 992, Ti, V, Cu, Y, Zr, Nb, Mo, Rh, Pd, Hf, Ta, W, Ta , At least one selected from the group of nonmagnetic transition metals consisting of Ir, Te and Ru. In the present invention, the nonmagnetic transition metal used in the underlayer 83 includes Ti, V, Cu, Y, Zr, Nb, Mo, Rh, Pd, Hf, Ta, W, Ta, Ir, Te, and Ru. And at least one selected from the group of nonmagnetic transition metals. The tunnel barrier layers 122, 822, and 922 may be equivalent to the polycrystalline Mg oxide layer containing B (boron) instead of the polycrystalline Mg oxide layer described above. it can.

10, 80, 90 Magnetoresistive element 11, 81, 91 Substrate 12, 82, 92 TMR element 121, 821, 921 Ferromagnetic layer 122, 822, 922 Tunnel barrier layer 123, 823, 9233 Ferromagnetic layer (magnetization free) Layer) 13, 93 Underlayer (electrode) 83 B (boron) -containing underlayer (electrode) 14, 84, 94 Antiferromagnetic layer 15, 85, 95 Ferromagnetic layer 16, 86, 961 Nonmagnetic BRu alloy layer ( Non-magnetic layer for exchange coupling) 17 Non-magnetic BTa alloy layer (electrode) 87, 97 Electrode 18, 88, 98 Hard mask layer 19, 89, 99 Magnetization fixed layer 200 Magnetoresistive element creation apparatus 201A to 201C Film formation chamber 202 Transport Chamber 203 Etching chamber 204 Gate valve 205, 206 Load lock / unload Lock chamber 31 to 35, 41 to 45, 51 to 54 Cathode 207A to 207C Power supply unit 301 Transfer chamber 302 to 304 Film forming chamber 305 Load lock / unload lock chamber 306 Central processing unit (CPU) 307 to 311 Bus line 312 Storage medium 401 MRAM 402 Memory element 403 Word line 404 Bit line 501 Transistor 61 Aggregation of columnar crystal group 62 Columnar crystal 71 Metal Mg layer 72 Mg oxide layer 73 Metal Mg layer

Claims (7)

  A magnetoresistive element comprising a substrate, a tunnel barrier layer, a ferromagnetic layer, and a nonmagnetic metal layer containing B.   The magnetoresistive element according to claim 1, wherein the nonmagnetic metal layer contains a nonmagnetic transition metal. The nonmagnetic transition metal is at least selected from the group of nonmagnetic transition metals consisting of Ti, V, Cu, Y, Zr, Nb, Mo, Rh, Pd, Hf, Ta, W, Ta, Ir, Te and Ru. The magnetoresistive element according to claim 2, comprising one kind.   The magnetoresistive element according to claim 1, wherein the tunnel barrier layer includes a crystalline magnesium oxide-containing layer. substrate,
A magnetization fixed layer having an antiferromagnetic layer, a ferromagnetic layer, and a nonmagnetic metal layer containing B;
A magnetic free layer having a ferromagnetic layer and a nonmagnetic metal containing B, and a tunnel barrier layer containing a metal oxide located between the magnetization fixed layer and the magnetization free layer,
The magnetoresistive element characterized by the above-mentioned.   The magnetoresistive element according to claim 5, wherein the nonmagnetic metal layer contains a nonmagnetic transition metal. The nonmagnetic transition metal was selected from the group of nonmagnetic transition metals consisting of Ti, V, Cu, Y, Zr, Nb, Mo, Rh, Pd, Hf, Ta, W, Ta, Ir, Te, and Ru. The magnetoresistive element according to claim 6, comprising at least one kind.