Method for manufacturing magnetic storage element

Abstract

The purpose of the present invention is to manufacture a fine-patterned magnetic storage element with high precision.　A magnetic storage element (1) includes: a magnetic tunnel junction layer (30) having a structure in which an insulating layer (32) is sandwiched between two magnetic layers (31) and (33), and in which the resistance state changes in accordance with the magnetization direction of one of the magnetic layer (31) and the magnetic layer (33); and a metal layer (40) provided on the magnetic tunnel junction layer (30). A method for manufacturing the magnetic storage element (1) includes a step for forming a resist film (50) having an opening (50a) on a substrate (10) on which an electrode layer (20) is formed, a step for forming a magnetic tunnel junction layer (30) on the electrode layer (20) exposed in the opening (50a), a step for forming a metal layer (40) on the magnetic tunnel junction layer (30), and a step for removing the resist film (50).

Description

Method for manufacturing a magnetic memory element

[0001] The present invention relates to a method for manufacturing a magnetic memory element.

[0002] 2. Description of the Related Art There is known a technique for applying a magnetic tunnel junction (MTJ) element, which utilizes a resistance change due to a difference in magnetization direction, to a magnetic memory element such as a magnetoresistive random access memory (MRAM).

[0003] An MTJ element used in a magnetic memory element includes, for example, a fixed layer (magnetic layer) whose magnetization direction is fixed, a free layer (magnetic layer) whose magnetization direction is variable, and a tunnel barrier layer (insulating layer) disposed between the two. Here, the resistance of the MTJ element is low when the magnetization directions of the free layer and the fixed layer are parallel and high when they are antiparallel. In a magnetic memory element using an MTJ element, the parallel and antiparallel states correspond to binary data of "0" and "1."

[0004] Known magnetic memory elements include, for example, write wiring type and spin injection type magnetic memory elements. In a write wiring type magnetic memory element, the magnetization direction of the free layer is controlled based on a magnetic field generated by a current flowing through a write word line. In a spin injection type magnetic memory element, the magnetization direction of the free layer is controlled by the spin transfer effect generated when a current is passed through the MTJ element. Magnetic memory elements that change the magnetization direction of the free layer by a voltage instead of a current are also known. Conventionally, various methods have been proposed for manufacturing magnetic memory elements using MTJ elements.

[0005] Japanese Patent Application Laid-Open No. 2006-060044 Japanese Patent Application Laid-Open No. 2002-305290 Japanese Patent Application Laid-Open No. 2002-038285 International Publication No. 2009 / 096328 Pamphlet

[0006] Incidentally, when manufacturing a magnetic memory element, a patterning method using reactive ion etching (RIE), which is used in microfabrication, may be employed.

[0007] However, in RIE, the etching rate decreases as the aspect ratio of the object to be processed increases (microloading effect). Therefore, the etching time becomes longer, and if a thick resist is used, there is a risk of the resist collapsing. On the other hand, if the resist is thinned, there is a risk that the object to be processed will be scraped in the resist width direction due to long etching. Therefore, it may be difficult to manufacture a magnetic memory element with a fine pattern with high precision using RIE.

[0008] In one aspect, the present invention aims to manufacture a finely patterned magnetic memory element with high precision.

[0009] In one aspect, there is provided a method for manufacturing a magnetic memory element including a magnetic tunnel junction layer having a structure in which an insulating layer is sandwiched between two magnetic layers, and a resistance state of which changes depending on the magnetization direction of one of the magnetic layers, and a metal layer provided on the magnetic tunnel junction layer, the method including the steps of forming a resist film having an opening on a substrate on which an electrode layer is formed, forming the magnetic tunnel junction layer on the electrode layer exposed in the opening, forming the metal layer on the magnetic tunnel junction layer, and removing the resist film.

[0010] In one aspect, it becomes possible to manufacture magnetic memory elements with fine patterns with high precision.

[0011] The above and other objects, features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings illustrating preferred embodiments of the present invention.

[0012] FIG. 1 is a diagram illustrating an example of a magnetic memory element; FIG. 2 is a diagram (part 1) illustrating an example of a method for manufacturing a magnetic memory element; FIG. 3 is a diagram (part 3) illustrating an example of a method for manufacturing a magnetic memory element; FIG. 4 is a diagram illustrating a first modified example of a method for manufacturing a magnetic memory element; and FIG. 5 is a diagram illustrating a second modified example of a method for manufacturing a magnetic memory element.

[0013] 1A and 1B are diagrams illustrating an example of a magnetic memory element. Fig. 1A is a schematic cross-sectional view of a main part of an example of a magnetic memory element. Fig. 1B is a schematic view of a main part (memory cell) of a magnetic memory device using the magnetic memory element.

[0014] 1A includes a substrate 10, an electrode layer 20, a magnetic tunnel junction layer 30, and a metal layer 40. The substrate 10 may be made of various materials. For example, the substrate 10 may be a semiconductor substrate, a ceramic substrate, a glass substrate, a resin substrate, or the like.

[0015] The electrode layer 20 is provided on the substrate 10. The electrode layer 20 is made of various metal materials. For example, the electrode layer 20 is made of at least one metal selected from Pt (platinum), Ta (tantalum), W (tungsten), Mn (manganese), etc. Furthermore, the electrode layer 20 may be made of a metal material that exhibits the so-called spin Hall effect, a phenomenon in which, when a current is passed through it, a spin current is generated in a direction perpendicular to the current due to scattering caused by spin-orbit interaction. In this case, the electrode layer 20 may be made of, for example, Mn ３ An antiferromagnetic material such as Sn (manganese tin) or a material obtained by laminating a ferromagnetic material such as NiFe (nickel iron) on such an antiferromagnetic material can be used.

[0016] The magnetic tunnel junction layer 30 is provided on the electrode layer 20. The magnetic tunnel junction layer 30 includes a magnetic layer 31, an insulating layer 32, and a magnetic layer 33. The magnetic layer 31 is stacked on the electrode layer 20. The insulating layer 32 is stacked on the magnetic layer 31. The magnetic layer 33 is stacked on the insulating layer 32. The magnetic tunnel junction layer 30 has a structure in which the insulating layer 32 is sandwiched between two magnetic layers 31 and 33. The magnetic tunnel junction layer 30 is one form of an MTJ element.

[0017] The magnetic tunnel junction layer 30 (MTJ element) is classified into a so-called in-plane magnetization type and a perpendicular magnetization type. In the in-plane magnetization type magnetic tunnel junction layer 30, one of the magnetic layers 31 and 33 is a layer in which the magnetization in a direction parallel to the plane is reversible, and the other is a layer in which the magnetization in a direction parallel to the plane is fixed. In the perpendicular magnetization type magnetic tunnel junction layer 30, one of the magnetic layers 31 and 33 is a layer in which the magnetization in a direction perpendicular to the plane is reversible, and the other is a layer in which the magnetization in a direction perpendicular to the plane is fixed. Of the magnetic layers 31 and 33, the layer in which the magnetization direction is reversible is also referred to as a "free layer" or a "free layer." Of the magnetic layers 31 and 33, the layer in which the magnetization direction is fixed is also referred to as a "fixed layer" or a "pinned layer."

[0018] The insulating layer 32 of the magnetic tunnel junction layer 30 is a layer interposed between the magnetic layer 31 and the magnetic layer 33. The insulating layer 32 is also called a "barrier layer" or a "tunnel barrier layer." For example, the insulating layer 32 may be made of magnesium oxide (MgO), Al ２ O ３ An insulator such as aluminum oxide is used.

[0019] Various magnetic materials are used for the magnetic layers 31 and 33 of the magnetic tunnel junction layer 30 depending on the specifications required for the magnetic memory element 1, the data writing and reading method, etc. For example, ferromagnetic materials such as CoFeB (cobalt iron boron), CoFe (cobalt iron), NiFe, etc. are used for the magnetic layers 31 and 33, or one of them. In addition, Mn, which can control the magnetization direction by utilizing the anomalous Hall effect, is used for the magnetic layers 31 and 33, or one of them. ３ An antiferromagnetic metal compound such as Sn may be used. At least one of the magnetic layers 31 and 33 may be made of a metal compound containing Mn, such as those represented by the following formula (1):

[0020] [Chemical formula 1] Mn ３＋ｒ X １－ｒ(1) (In formula (1), X represents Sn (tin), Ge (germanium), Ga (gallium), Pt, Rh (rhodium), Ir (iridium), or Pd (palladium), and r represents a numerical value of −0.2 or more and 0.2 or less.)

[0021] Furthermore, of the magnetic layers 31 and 33, the layer (fixed layer) whose magnetization direction is fixed may include magnetic materials such as ferromagnetic materials and antiferromagnetic materials, as well as other material layers (single-layer or multi-layer metal films, magnetic films, non-magnetic films, etc.) for fixing the magnetic anisotropy.

[0022] The metal layer 40 is provided on the magnetic tunnel junction layer 30. The metal layer 40 is also called a "cap layer" or the like. Various metal materials are used for the metal layer 40. For example, the metal layer 40 is made of at least one metal selected from Al (aluminum), W, Ti (titanium), Ru (ruthenium), Ta, etc.

[0023] A magnetic memory device 100 (its memory cell) as shown in Fig. 1(B) is realized by using a magnetic memory element 1 as shown in Fig. 1(A). For convenience, in Fig. 1(B), of the magnetic layers 31 and 33 of the magnetic tunnel junction layer 30 in the magnetic memory element 1, the magnetic layer 31 is shown as a layer (free layer) whose magnetization direction is reversible, and the magnetic layer 33 is shown as a layer (fixed layer) whose magnetization direction is fixed. Fig. 1(B) shows a perpendicular magnetization type magnetic tunnel junction layer 30 as an example, in which the magnetization M11 of the magnetic layer 31, which is the free layer, is represented by a bidirectional thick arrow, and the magnetization M13 of the magnetic layer 33, which is the fixed layer, is represented by a unidirectional thick arrow.

[0024] The magnetic memory device 100 includes a memory cell array including a number of magnetic memory elements 1 (memory cells) corresponding to its capacity. For convenience, Fig. 1B shows a schematic diagram of one memory cell included in the memory cell array, i.e., one magnetic memory element 1.

[0025] As shown in FIG. 1B, a transistor 110, a wiring 120, and a wiring 130 are connected to the magnetic memory element 1 of each memory cell in the magnetic memory device 100. The transistor 110 is a selection transistor for selecting a specific memory cell in the memory cell array of the magnetic memory device 100. The transistor 110 is connected in series between the wiring 120 and the electrode layer 20 of the magnetic memory element 1. The on / off operation of the transistor 110 is controlled by applying a predetermined potential between the wiring 120 and the electrode layer 20 (between the source and drain) and applying a predetermined signal (voltage) to the control terminal (gate). In addition, the wiring 130 is connected to the metal layer 40 of the magnetic memory element 1.

[0026] In the magnetic memory device 100, when writing data, the on / off operation of the transistor 110 is controlled, for example, to control the current flowing from the wiring 120 to the electrode layer 20 and then to the magnetic tunnel junction layer 30, or the current flowing from the wiring 130 to the magnetic tunnel junction layer 30 and then to the electrode layer 20 (in the case of a spin injection type magnetic memory element 1). Alternatively, when writing data, the on / off operation of the transistor 110 is controlled, for example, to control the current flowing from the wiring 120 to the electrode layer 20 and its direction (in the case of a spin orbit torque type magnetic memory element 1 in which an antiferromagnetic material is used for the electrode layer 20). By controlling the current flowing in the magnetic tunnel junction layer 30 of the magnetic memory element 1 or the current flowing in the electrode layer 20 of the magnetic memory element 1 by the transistor 110, the magnetization M11 of the magnetic layer 31 of the magnetic tunnel junction layer 30 is made parallel or antiparallel to the magnetization M13 of the magnetic layer 33.

[0027] The magnetic tunnel junction layer 30 is in a low resistance state when the magnetization directions of the magnetic layer 31 and the magnetic layer 33 are parallel. The magnetic tunnel junction layer 30 is in a high resistance state when the magnetization directions of the magnetic layer 31 and the magnetic layer 33 are antiparallel. The magnetic memory element 1 functions as a memory element that stores binary data of "0" and "1" depending on the resistance state of the magnetic tunnel junction layer 30.

[0028] In the magnetic memory device 100, when reading data, the on / off operation of the transistor 110 is controlled, and a current is detected that flows from the wiring 120 through the electrode layer 20 to the magnetic tunnel junction layer 30 and is output from the metal layer 40. For example, when the magnetic tunnel junction layer 30 is in a low resistance state (the magnetization directions of the magnetic layer 31 and the magnetic layer 33 are parallel), the output is read as "0," and when the magnetic tunnel junction layer 30 is in a high resistance state (the magnetization directions of the magnetic layer 31 and the magnetic layer 33 are antiparallel), the output is read as "1."

[0029] Next, a method for manufacturing the magnetic memory element 1 having the above-described configuration will be described. One known method for manufacturing the magnetic memory element 1 employs a process using RIE. That is, the electrode layer 20, the magnetic tunnel junction layer 30, and the metal layer 40 are sequentially stacked on the substrate 10, a resist is formed thereon, and after the resist is patterned, the metal layer 40, the magnetic tunnel junction layer 30, and the electrode layer 20 are etched (patterned) by RIE. However, with such a method using RIE, it may be difficult to manufacture a magnetic memory element 1 with a fine pattern with high precision.

[0030] When the planar dimensions (e.g., diameter) of the magnetic memory element 1 are in the range of 40 nm to 60 nm, the write performance can be improved, or the number or capacity of the magnetic memory elements 1 (memory cells) mounted in the magnetic memory device 100 can be increased. Furthermore, due to its stacked structure, the magnetic memory element 1 may have a height perpendicular to the surface of at least approximately 100 nm. Therefore, in the above-described method using RIE, patterning with a relatively high aspect ratio may be required for the performance or structure of the magnetic memory element 1 to be manufactured. However, patterning with a relatively high aspect ratio requires a long RIE etching time. In this case, if a thick resist is used, there is a risk of the resist collapsing. On the other hand, if the resist is thinned, there is a risk that the target to be processed will be removed in the width direction of the resist due to long etching times. Therefore, it may be difficult to manufacture a magnetic memory element 1 with a fine pattern with high precision using RIE.

[0031] In view of these points, the magnetic memory element 1 is manufactured by, for example, a method as shown in the following FIGS. 2 to 4 , to obtain a magnetic memory element 1 with a fine pattern with high precision. FIGS. 2 to 4 are diagrams illustrating an example of a manufacturing method for a magnetic memory element. FIG. 2 shows an example of a manufacturing flow for a magnetic memory element. FIG. 3A shows a schematic cross-sectional view of a main part of an example of an electrode layer forming process. FIG. 3B shows a schematic cross-sectional view of a main part of an example of a resist film forming process. FIG. 3C shows a schematic cross-sectional view of a main part of an example of a resist film exposure process. FIG. 3D shows a schematic cross-sectional view of a main part of an example of a resist film development process. FIG. 4A shows a schematic cross-sectional view of a main part of an example of a magnetic tunnel junction layer forming process. FIG. 4B shows a schematic cross-sectional view of a main part of an example of a metal layer forming process. FIG. 4C shows a schematic cross-sectional view of a main part of an example of a planarization process. FIG. 4D is a schematic cross-sectional view of a main part of an example of the resist film removal step.

[0032] As described above, the magnetic memory element 1 has the electrode layer 20 provided on the substrate 10, the magnetic tunnel junction layer 30 provided on the electrode layer 20, and the metal layer 40 provided on the magnetic tunnel junction layer 30. The magnetic tunnel junction layer 30 has a structure in which an insulating layer 32 is sandwiched between two magnetic layers 31 and 33, and is a form of an MTJ element in which the resistance state changes depending on the magnetization direction of one of the magnetic layers 31 and 33.

[0033] 2, the manufacturing method of the magnetic memory element 1 includes a step of forming a resist film having an opening on the substrate 10 on which the electrode layer 20 has been formed (step S1), a step of forming a magnetic tunnel junction layer 30 on the electrode layer 20 exposed in the opening of the resist film (step S2), a step of forming a metal layer 40 on the magnetic tunnel junction layer 30 (step S3), and a step of removing the resist film (step S4).

[0034] The manufacturing method of such a magnetic memory element 1 will be further explained with reference to Fig. 3 and Fig. 4. In manufacturing the magnetic memory element 1, first, a substrate 10 as shown in Fig. 3(A) is prepared. Various substrates such as a semiconductor substrate, a ceramic substrate, a glass substrate, a resin substrate, etc. are used as the substrate 10. An electrode layer 20 is formed on the prepared substrate 10 as shown in Fig. 3(A). A metal material such as Pt, Ta, W, or Mn is used for the electrode layer 20. For example, Mn is used for the electrode layer 20. ３ An antiferromagnetic material such as Sn, or a ferromagnetic material such as NiFe laminated on such an antiferromagnetic material, may be used. The electrode layer 20 is formed by, for example, a sputtering method. Alternatively, the electrode layer 20 may be formed by a vapor deposition method, a plating method, or the like. The thickness of the electrode layer 20 is set to, for example, several tens of nanometers.

[0035] The electrode layer 20 may be formed in a predetermined pattern on the substrate 10. For example, after forming the electrode layer 20 on the entire surface of the substrate 10 using a sputtering method or the like, a predetermined resist pattern is formed, and etching is performed using the resist pattern as a mask, thereby forming the electrode layer 20 having the predetermined pattern on the substrate 10. Alternatively, after forming a predetermined resist pattern on the substrate 10, the electrode layer 20 is formed using a sputtering method or the like, and the resist pattern is removed (lift-off), thereby forming the electrode layer 20 having the predetermined pattern on the substrate 10.

[0036] After the electrode layer 20 is formed on the substrate 10, a resist material 50A is formed on the substrate 10 on which the electrode layer 20 is formed, as shown in FIG. 3B. Various photosensitive positive or negative resist materials are used for the resist material 50A. For example, at least one of an acrylic resist or a styrene resist is used for the resist material 50A. For the resist material 50A, a material with excellent heat resistance, such as at least one selected from an organometallic resist, a polysiloxane resist, a polyimide resist, and a novolac resin resist, may be used. Usable resists are listed below, but are not limited to these.

[0037] Examples of acrylic resists that can be used include resists described in JP 2010-217884 A, JP 2012-027436 A, JP 2012-068544 A, and JP 2012-073402 A. Examples of styrene resists that can be used include resists described in JP 2016-533532 A, JP 2020-8842 A, and JP 2003-076019 A. Examples of organometallic resists that can be used include resists described in JP 2016-530565 A, JP 2023-025059 A, and the like. Examples of polysiloxane-based resists that can be used include resists described in JP 2003-173027 A, JP 2007-154047 A, JP 2012-224770 A, etc. Examples of polyimide-based resists that can be used include resists described in JP 2009-9934 A, Japanese Patent No. 7056808, Japanese Patent No. 7201024, etc. Examples of novolac resin-based resists that can be used include resists described in Japanese Patent No. 3452206, Japanese Patent No. 10-207057, Japanese Patent No. 2002-278067, etc.

[0038] A predetermined material is used and a coating film of the material is formed on the electrode layer 20 provided on the substrate 10 by spin coating or the like, thereby forming a resist material 50A as shown in FIG. 3B. The formed coating film of the resist material 50A may be pre-baked. The thickness of the resist material 50A is set to be equal to or greater than the total thickness of the magnetic tunnel junction layer 30 and the metal layer 40 of the magnetic memory element 1 to be finally manufactured. The thickness of the resist material 50A is set taking into consideration thickness fluctuations due to shrinkage during baking or hardening, dissolution during development, and the like, for example.

[0039] After the resist material 50A is formed, as shown in FIG. 3C , an exposure mask 60 having light-transmitting portions 61 and light-shielding portions 62 in a predetermined pattern is used to expose the resist material 50A. Here, exposure of a negative resist material 50A is shown as an example. For example, an exposure mask 60 having light-transmitting portions 61 and light-shielding portions 62 in a dot pattern corresponding to the memory cell array (each magnetic memory element 1) of the magnetic memory device 100 is used to expose the negative resist material 50A. The exposure light 70 may be g-line, i-line, excimer laser, ultraviolet light, electron beam, or other light selected according to the type and components of the resist material 50A. In an example where the resist material 50A is negative, the portions of the resist material 50A irradiated with the exposure light 70 that passes through the light-transmitting portions 61 of the exposure mask 60 become hydrophilic portions 51, and the portions shielded by the light-shielding portions 62 of the exposure mask 60 become hydrophobic portions 52. The exposed resist material 50A may be subjected to a post-bake.

[0040] In an example where the resist material 50A is a negative type, after the resist material 50A is exposed, negative tone development using an organic solvent or the like is performed, and the hydrophobic portions 52 (portions where the exposure light 70 is blocked) are removed as shown in Fig. 3(D) . Negative tone development results in a resist pattern with excellent low roughness performance, and can form a good pattern that is particularly resistant to collapse when forming a fine line and space pattern and has excellent etching resistance.

[0041] A negative pattern in which the unexposed portions dissolve is formed on the substrate by developing using an organic solvent developer for 10 seconds to 3 minutes, preferably 30 seconds to 2 minutes, by a conventional method such as dipping, puddling, or spraying. Examples of the developer include ketones such as 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, and methylacetophenone; propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, butenyl acetate, isoamyl acetate, propyl formate, butyl formate, isobutyl formate, amyl formate, isoamyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, and methyl propionate. Esters such as butyl lactate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, amyl lactate, isoamyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, ethyl phenylacetate, and 2-phenylethyl acetate can be preferably used.

[0042] At the end of development, rinsing is performed. A solvent that is miscible with the developer but does not dissolve the resist film is preferred as the rinsing solution. Preferred examples of such solvents include alcohols having 3 to 10 carbon atoms, ether compounds having 8 to 12 carbon atoms, alkanes, alkenes, alkynes, and aromatic solvents having 6 to 12 carbon atoms.

[0043] Specifically, examples of alkanes having 6 to 12 carbon atoms include hexane, heptane, octane, nonane, decane, undecane, dodecane, methylcyclopentane, dimethylcyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, cycloheptane, cyclooctane, cyclononane, etc. Examples of alkenes having 6 to 12 carbon atoms include hexene, heptene, octene, cyclohexene, methylcyclohexene, dimethylcyclohexene, cycloheptene, cyclooctene, etc. Examples of alkynes having 6 to 12 carbon atoms include hexyne, heptine, octyne, etc. Examples of alcohols having 3 to 10 carbon atoms include n-propyl alcohol, isopropyl alcohol, 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, tert-amyl alcohol, neopentyl alcohol, 2-methyl-1-butanol, 3-methyl-1-but ... 1-butanol, 3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol, cyclohexanol, 1-octanol, and the like.

[0044] Examples of the ether compound having 8 to 12 carbon atoms include one or more solvents selected from di-n-butyl ether, diisobutyl ether, di-sec-butyl ether, di-n-pentyl ether, diisopentyl ether, di-sec-pentyl ether, di-tert-amyl ether, and di-n-hexyl ether. In addition to the above-mentioned solvents, aromatic solvents such as toluene, xylene, ethylbenzene, isopropylbenzene, tert-butylbenzene, and mesitylene can also be used.

[0045] To form a resist pattern using negative tone development, acrylic resists, styrene resists, organometallic resists, polysiloxane resists, polyimide resists, and novolac resin resists can be used. Specific examples of acrylic resists are described in detail in JP-A-2016-533532, JP-A-2013-137513, JP-A-2016-147979, etc. When heat resistance is required for the resist pattern, organometallic resists, polysiloxane resists, polyimide resists, and novolac resin resists are particularly suitable. In this case, the organometallic resists described in JP-A-2023-25059 are particularly suitable. Among organometallic resists, resist compositions containing alkyltin compounds are particularly suitable.

[0046] The hydrophilic portions 51 (portions irradiated with the exposure light 70) remaining after development become the resist film 50 that functions as a mask in subsequent processes. That is, by the above-described exposure and development, the resist film 50 having openings 50a is formed. The openings 50a are formed in the resist film 50 so as to communicate with the electrode layer 20 on the substrate 10, i.e., so that the electrode layer 20 is exposed in the openings 50a. The openings 50a are formed in regions where the magnetic tunnel junction layer 30 and the metal layer 40 of the magnetic memory element 1 are to be formed. The openings 50a have planar dimensions (e.g., diameters) ranging from 40 nm to 60 nm, for example. The type of resist material 50A ( FIG. 3B ) and the conditions for its exposure ( FIG. 3C ) and development ( FIG. 3D ) are adjusted so that the openings 50a having predetermined planar dimensions are formed in the resist film 50.

[0047] In the resist film 50, openings 50a can be formed with high planar dimensional accuracy by exposing and developing a coating of the resist material 50A. Note that, although an example of forming the resist film 50 having openings 50a using a negative resist material 50A has been shown here, the resist film 50 having openings 50a can also be formed using a positive resist material 50A. In this case, an exposure mask for the positive resist material 50A is used, and the portions of the resist material 50A irradiated with exposure light are removed by development, thereby forming the resist film 50 having openings 50a.

[0048] For example, the process shown in Figures 3(A) to 3(D) realizes step S1 shown in Figure 2 above, i.e., the process of forming a resist film 50 having an opening 50a on the substrate 10 on which the electrode layer 20 is formed.

[0049] After forming the resist film 50 having the opening 50a, as shown in FIG. 4A, the magnetic tunnel junction layer 30 is formed on the electrode layer 20 exposed in the opening 50a. The magnetic tunnel junction layer 30 includes a magnetic layer 31, an insulating layer 32, and a magnetic layer 33. The magnetic layer 31 and the magnetic layer 33 are made of a ferromagnetic material such as CoFeB or Mn ３ A metal compound containing Mn, such as Sn, as shown in the above formula (1) is used. An insulator such as MgO is used for the insulating layer 32. The magnetic tunnel junction layer 30 is formed on the electrode layer 20 exposed in the opening 50 a by, for example, sputtering (sputtering process).

[0050] In forming the magnetic tunnel junction layer 30, first, a magnetic layer 31 is formed on the electrode layer 20 in the opening 50 a of the resist film 50 by sputtering. For example, the thickness of the magnetic layer 31 formed by sputtering is set in the range of 10 nm to 70 nm. Next, an insulating layer 32 is formed on the magnetic layer 31 in the opening 50 a by sputtering. For example, the thickness of the insulating layer 32 formed by sputtering is set in the range of 0.1 nm to 10 nm. Next, a magnetic layer 33 is formed on the insulating layer 32 in the opening 50 a by sputtering. For example, the thickness of the magnetic layer 33 formed by sputtering is set in the range of 10 nm to 70 nm. The magnetic tunnel junction layer 30 is formed to a height such that it does not protrude from the opening 50 a of the resist film 50. In other words, the thickness of the resist film 50 when it is formed, or the thickness of the resist material 50A for forming the resist film 50 when it is formed, is adjusted so that the magnetic tunnel junction layer 30 to be formed does not protrude from the opening 50a.

[0051] In forming the magnetic layer 31, the insulating layer 32, and the magnetic layer 33 by sputtering, a sputtering target for each layer is prepared, and the target is used to form each layer. In the sputtering process, conditions (temperature, pressure, etc.) suitable for forming the magnetic layer 31, the insulating layer 32, and the magnetic layer 33 are set.

[0052] When the magnetic layer 31, the insulating layer 32, and the magnetic layer 33 of the magnetic tunnel junction layer 30 are formed by sputtering, a heat treatment is performed in a temperature range of 100° C. to 500° C. to form the magnetic layer 31, the insulating layer 32, and the magnetic layer 33. For example, the magnetic layer 31 is sputtered while being heated at a temperature in this temperature range, or is sputtered and then heated at a temperature in this temperature range to improve crystallinity, etc. The insulating layer 32 is sputtered while being heated at a temperature in this temperature range, or is sputtered and then heated at a temperature in this temperature range to improve crystallinity, etc. The magnetic layer 33 is sputtered while being heated at a temperature in this temperature range, or is sputtered and then heated at a temperature in this temperature range to improve crystallinity, etc. It can also be said that the sputtering process of the magnetic layer 31, the insulating layer 32, and the magnetic layer 33 of the magnetic tunnel junction layer 30 includes a heat treatment process in a temperature range of 100° C. to 500° C.

[0053] When such a heat treatment is performed to form the magnetic layer 31, the insulating layer 32, and the magnetic layer 33 of the magnetic tunnel junction layer 30, it is preferable to use a heat-resistant material such as an organic metal resist, a polysiloxane resist, a polyimide resist, or a novolac resin resist for the resist film 50 (its resist material 50A). Using such a material can suppress deterioration of the resist film 50, dimensional fluctuation of the opening 50a, inclusion of components of the resist film 50 into the magnetic tunnel junction layer 30, and resulting deterioration of the characteristics of the magnetic tunnel junction layer 30, even in the sputtering process of the magnetic tunnel junction layer 30, which is performed at a relatively high temperature.

[0054] 4A, the magnetic tunnel junction layer 30 can be formed by using a deposition method or the like. For example, the process shown in FIG. 4A achieves step S2 shown in FIG. 2, that is, the process of forming the magnetic tunnel junction layer 30 on the electrode layer 20 exposed in the opening 50a of the resist film 50.

[0055] After the formation of the magnetic tunnel junction layer 30, as shown in FIG. 4B , a metal layer 40 is formed on the magnetic tunnel junction layer 30 (the magnetic layer 33 thereof) formed in the opening 50 a of the resist film 50. The metal layer 40 is made of a metal such as Al, W, Ti, Ru, or Ta. The metal layer 40 is formed on the magnetic tunnel junction layer 30 in the opening 50 a of the resist film 50 by, for example, a sputtering method. For example, the thickness of the metal layer 40 formed by the sputtering method is set to a range of 1 nm to 30 nm. The metal layer 40 is formed on the magnetic tunnel junction layer 30 so that its upper surface is at the same height as the upper surface of the resist film 50 or is higher than the upper surface of the resist film 50. In other words, the thickness of the resist film 50 when formed or the thickness of the resist material 50A when formed for forming the resist film 50 is adjusted so that the metal layer 40 to be formed has such a height.

[0056] In forming the metal layer 40 by sputtering, a sputtering target for the metal layer 40 is prepared, and the target is used to form the metal layer 40. In the sputtering process, conditions (temperature, pressure, etc.) suitable for forming the metal layer 40 are set.

[0057] When forming the metal layer 40 using a sputtering method, a heat treatment is performed in a temperature range of 100° C. to 500° C. to form the metal layer 40. For example, the metal layer 40 is sputtered while being heated at a temperature in this temperature range, or is heated at a temperature in this temperature range after being sputtered to improve crystallinity, etc. The sputtering process of the metal layer 40 can also be said to include a heat treatment process in a temperature range of 100° C. to 500° C.

[0058] When the metal layer 40 is formed by such a heat treatment, it is preferable that the resist film 50 (its resist material 50A) be made of a heat-resistant material such as an organic metal resist, a polysiloxane resist, a polyimide resist, or a novolac resin resist. Using such a material can suppress deterioration of the resist film 50, dimensional fluctuations of the opening 50a, incorporation of components of the resist film 50 into the magnetic tunnel junction layer 30, and resulting deterioration of the characteristics of the magnetic tunnel junction layer 30, even during the sputtering process of the metal layer 40, which is performed at a relatively high temperature.

[0059] The metal layer 40 can be formed by a method other than sputtering, such as vapor deposition, etc. For example, the process shown in Fig. 4B achieves step S3 shown in Fig. 2, i.e., the process of forming the metal layer 40 on the magnetic tunnel junction layer 30.

[0060] After the metal layer 40 is formed, planarization is performed by CMP (Chemical Mechanical Polishing) or the like, as shown in FIG. 4C . This planarization removes excess metal components formed on the upper surface of the resist film 50 and a portion of the metal layer 40 formed to protrude above the upper surface of the resist film 50. The planarization may be performed under conditions such that the surface portion of the resist film 50 is also polished. The planarization may adjust the thickness of the metal layer 40, and may adjust the height of the magnetic memory element 1 including the electrode layer 20, the magnetic tunnel junction layer 30, and the metal layer 40 relative to the substrate 10. The planarization forms the magnetic memory element 1 having a predetermined height.

[0061] 4A to 4C, it can be said that the steps S2 and S3 shown in FIG. 2 above, i.e., the steps of forming the magnetic tunnel junction layer 30 on the electrode layer 20 exposed in the opening 50 a of the resist film 50 and forming the metal layer 40 on the magnetic tunnel junction layer 30, are realized.

[0062] After planarization, the resist film 50 is removed as shown in FIG. 4D . For example, the resist film 50 is removed using a resist stripper. Examples of resist strippers include organic solvents such as aminoethanol, aminopropanol, aminoisopropanol, aminobutanol, aminopentanol, aminohexanol, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, cyclohexanone, acetone, N-methyl-2-pyrrolidone, ethyl lactate, and methyl amyl ketone, or strippers made from combinations thereof. Furthermore, to strip resists formed using organometallic resists, for example, a liquid containing cerium ammonium nitrate as a main component, a liquid containing potassium ferricyanide or sodium ferricyanide as a main component, or a liquid containing aluminum chloride as a main component, which are used in wet etching methods, can be used. Alternatively, the resist film 50 is removed using a gas such as plasma or ozone.

[0063] 2, that is, the process of removing the resist film 50. By the above-described processes, the magnetic memory element 1 having the structure shown in FIG. 4D, that is, the magnetic memory element 1 having the structure in which the electrode layer 20, the magnetic tunnel junction layer 30, and the metal layer 40 are stacked on the substrate 10, is manufactured.

[0064] As described above, in the method for manufacturing the magnetic memory element 1 of the present invention, it is possible to form the fine openings 50a in the resist film 50 with high precision. The magnetic layer 31, the insulating layer 32, and the magnetic layer 33 of the magnetic tunnel junction layer 30, and the metal layer 40 are formed in the fine openings 50a formed with high precision. Therefore, the magnetic memory element 1 having a fine pattern is manufactured with high precision. In the method for manufacturing the magnetic memory element 1 of the present invention, it is possible to omit patterning of the magnetic tunnel junction layer 30 and the metal layer 40 by RIE.

[0065] The manufacturing method of the magnetic memory element 1 of the present invention can be advantageous in manufacturing a fine-patterned magnetic memory element 1 with high precision compared to a manufacturing method using RIE. For example, compared to a method of manufacturing the magnetic memory element 1 by sequentially stacking the magnetic tunnel junction layer 30 and the metal layer 40 on the substrate 10 on which the electrode layer 20 has been formed, forming a resist thereon, patterning the resist, and then patterning the metal layer 40 and the magnetic tunnel junction layer 30 by RIE, the method has the following advantages: That is, it is possible to suppress the etching time that would be prolonged when RIE is performed on a stacked structure of the metal layer 40 and the magnetic tunnel junction layer 30 that has a certain thickness or more, which would result in the collapse of the resist or the progression of etching in the width direction of the stacked structure, and as a result, the reduction in the dimensional precision of the magnetic memory element 1.

[0066] According to the manufacturing method of the magnetic memory element 1 of the present invention, it is possible to manufacture with high precision a fine-patterned magnetic memory element 1. Using the manufacturing method as described above, it is possible to manufacture, for example, a magnetic memory element 1 having the following configuration.

[0067] (First Configuration Example) For example, the electrode layer 20 on the substrate 10 includes at least one metal selected from Pt, Ta, W, Mn, etc. The magnetic tunnel junction layer 30 includes magnetic layers 31 and 33 using a ferromagnetic material such as CoFeB, and an insulating layer 32 using an insulator such as MgO. The fixed layers of the magnetic layers 31 and 33 may include another material layer for fixing the magnetic anisotropy. The metal layer 40 includes at least one metal selected from Al, W, Ti, Ru, Ta, etc.

[0068] Using the electrode layer 20, magnetic tunnel junction layer 30, and metal layer 40, the magnetic memory element 1 is manufactured according to the example method shown in FIGS. 2 to 4. Specifically, a resist film 50 having an opening 50a is formed on a substrate 10 on which an electrode layer 20 containing Pt, Ta, W, Mn, or the like is formed (Step S1). A magnetic tunnel junction layer 30 including a magnetic layer 31 such as CoFeB, an insulating layer 32 such as MgO, and a magnetic layer 33 such as CoFeB is formed on the electrode layer 20 exposed through the opening 50a of the resist film 50 (Step S2). A metal layer 40 including Al, W, Ti, Ru, Ta, or the like is formed on the magnetic tunnel junction layer 30 (Step S3). Then, the resist film 50 is removed (Step S4). In this manner, the magnetic memory element 1 of the first configuration example is manufactured.

[0069] (Second Configuration Example) For example, the electrode layer 20 on the substrate 10 contains at least one metal selected from Pt, Ta, W, Mn, etc. The magnetic tunnel junction layer 30 is made of a metal compound containing Mn as shown in the above formula (1), for example, Mn ３ The magnetic tunnel junction layer 30 includes magnetic layers 31 and 33 using an antiferromagnetic material such as Sn, and an insulating layer 32 using an insulator such as MgO. Alternatively, one of the magnetic layers 31 and 33 may be made of a metal compound containing Mn as shown in formula (1) above, and the other may be made of another magnetic material. The fixed layers of the magnetic layers 31 and 33 may include another material layer for fixing the magnetic anisotropy. The metal layer 40 includes at least one metal selected from Al, W, Ti, Ru, Ta, and the like.

[0070] The magnetic memory element 1 is manufactured using the electrode layer 20, the magnetic tunnel junction layer 30, and the metal layer 40, according to the example of the method shown in Figures 2 to 4. That is, a resist film 50 having an opening 50a is formed on a substrate 10 on which an electrode layer 20 containing Pt, Ta, W, Mn, or the like is formed (step S1). ３ A magnetic layer 31 such as Sn, an insulating layer 32 such as MgO, and Mn３ A magnetic tunnel junction layer 30 including a magnetic layer 33 such as Sn is formed (step S2). A metal layer 40 including Al, W, Ti, Ru, Ta, or the like is formed on the magnetic tunnel junction layer 30 (step S3). Then, the resist film 50 is removed (step S4). In this manner, the magnetic memory element 1 of the second configuration example is manufactured.

[0071] (Third Configuration Example) For example, the electrode layer 20 on the substrate 10 may be formed of a metal compound containing Mn as shown in the above formula (1), for example, Mn ３ The magnetic tunnel junction layer 30 may include an antiferromagnetic material such as Sn, or a ferromagnetic material such as NiFe laminated thereon. The magnetic tunnel junction layer 30 includes magnetic layers 31 and 33 using a ferromagnetic material such as CoFeB, and an insulating layer 32 using an insulating material such as MgO. The fixed layers of the magnetic layers 31 and 33 may include another material layer for fixing the magnetic anisotropy. The metal layer 40 may include at least one metal selected from Al, W, Ti, Ru, Ta, and the like.

[0072] The electrode layer 20, the magnetic tunnel junction layer 30, and the metal layer 40 are used to manufacture the magnetic memory element 1 according to the example of the method shown in FIGS. ３ A resist film 50 having an opening 50a is formed on a substrate 10 on which an electrode layer 20 such as Sn is formed (Step S1). A magnetic tunnel junction layer 30 including a magnetic layer 31 such as CoFeB, an insulating layer 32 such as MgO, and a magnetic layer 33 such as CoFeB is formed on the electrode layer 20 exposed through the opening 50a of the resist film 50 (Step S2). A metal layer 40 including Al, W, Ti, Ru, Ta, or the like is formed on the magnetic tunnel junction layer 30 (Step S3). Then, the resist film 50 is removed (Step S4). In this manner, the magnetic memory element 1 of the third configuration example is manufactured.

[0073] Furthermore, a modified example of the manufacturing method of the magnetic memory element 1 will be described. Figure 5 is a diagram illustrating a first modified example of the manufacturing method of the magnetic memory element. Figure 5(A) shows a schematic cross-sectional view of a main part of an example of a magnetic tunnel junction layer forming step. Figure 5(B) shows a schematic cross-sectional view of a main part of an example of a metal layer forming step.

[0074] After forming the resist film 50 having the opening 50a as shown in FIG. 3D, the magnetic tunnel junction layer 30 may be formed on the electrode layer 20 in the opening 50a and on the resist film 50 as shown in FIG. 5A. After forming the magnetic tunnel junction layer 30, the metal layer 40 may be formed on the magnetic tunnel junction layer 30 in the opening 50a and on the magnetic tunnel junction layer 30 formed on the resist film 50 as shown in FIG. 5B. Then, the excess magnetic tunnel junction layer 30 and the metal layer 40 formed on the resist film 50, i.e., above the position indicated by the dotted line L1 in FIG. 5B, are removed by planarization such as CMP. This results in the state shown in FIG. 4C, and the magnetic memory element 1 shown in FIG. 4D may be formed by removing the resist film 50.

[0075] 6A and 6B are diagrams illustrating a second modified example of the method for manufacturing a magnetic memory element. Fig. 6A is a schematic cross-sectional view of a main part of an example of a magnetic tunnel junction layer and metal layer formation step. Fig. 6B is a schematic cross-sectional view of a main part of an example of a resist film removal step.

[0076] 3D, the magnetic tunnel junction layer 30 and the metal layer 40 may be formed on the electrode layer 20 in the opening 50a and on the resist film 50, as shown in FIG. 6A. Then, by lift-off, the excess magnetic tunnel junction layer 30 and the metal layer 40 formed on the resist film 50 are removed together with the resist film 50. Using this method, the magnetic memory element 1 shown in FIG. 6B may be formed.

[0077] The foregoing merely illustrates the principles of the present invention. Further, since numerous modifications and changes will be apparent to those skilled in the art, the present invention is not limited to the exact construction and application shown and described above, and all corresponding modifications and equivalents are deemed to be within the scope of the present invention as defined by the appended claims and their equivalents.

[0078] REFERENCE SIGNS LIST 1 magnetic memory element 10 substrate 20 electrode layer 30 magnetic tunnel junction layer 31, 33 magnetic layer 32 insulating layer 40 metal layer 50 resist film 50a opening 50A resist material 51 hydrophilic portion 52 hydrophobic portion 60 exposure mask 61 light-transmitting portion 62 light-shielding portion 70 exposure light 100 magnetic memory device 110 transistor 120, 130 wiring M11, M13 magnetization

Claims

1. A method for manufacturing a magnetic memory element including a magnetic tunnel junction layer having a structure in which an insulating layer is sandwiched between two magnetic layers, and whose resistance state changes depending on the magnetization direction of one of the magnetic layers, and a metal layer provided on the magnetic tunnel junction layer, the method including the steps of: forming a resist film having an opening on a substrate on which an electrode layer is formed; forming the magnetic tunnel junction layer on the electrode layer exposed in the opening; forming the metal layer on the magnetic tunnel junction layer; and removing the resist film.

2. The method for manufacturing a magnetic memory element according to claim 1, wherein the magnetic tunnel junction layer and the metal layer are formed by laminating them by a sputtering process.

3. The method for manufacturing a magnetic memory element according to claim 1, wherein the step of forming the resist film having the opening comprises the steps of: forming a coating film on the substrate using at least one of an acrylic resist or a styrene resist; and exposing the coating film to light and then developing it to form the opening.

4. The method for producing a magnetic memory element according to claim 3, wherein an organic solvent developer is used for the development.

5. The method for producing a magnetic memory element according to claim 1, wherein the metal layer contains at least one metal selected from the group consisting of Al, W, Ti, Ru and Ta.

6. The method for producing a magnetic memory element according to claim 1, wherein at least one of the two magnetic layers of the magnetic tunnel junction layer is one selected from the metal compounds represented by the following formula (1): [Chemical formula 1] Mn ３＋ｒ X １－ｒ (In the formula (1), X represents Sn, Ge, Ga, Pt, Rh, Ir, or Pd. r represents a numerical value of -0.2 or more and 0.2 or less.) 7. The method for manufacturing a magnetic memory element according to claim 2, wherein the sputtering step includes a heat treatment step in a temperature range of 100° C. or more and 500° C. or less.

8. The method for producing a magnetic memory element according to claim 7, wherein the resist film having the opening is made of at least one type selected from an organometallic resist, a polysiloxane resist, a polyimide resist, and a novolac resin resist.

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