US20200294566A1 - Magnetoresistive memory device and method of manufacturing magnetoresistive memory device - Google Patents
Magnetoresistive memory device and method of manufacturing magnetoresistive memory device Download PDFInfo
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- US20200294566A1 US20200294566A1 US16/565,316 US201916565316A US2020294566A1 US 20200294566 A1 US20200294566 A1 US 20200294566A1 US 201916565316 A US201916565316 A US 201916565316A US 2020294566 A1 US2020294566 A1 US 2020294566A1
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- ferromagnet
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- 238000004519 manufacturing process Methods 0.000 title claims description 9
- 239000012212 insulator Substances 0.000 claims abstract description 48
- 239000000463 material Substances 0.000 claims abstract description 41
- 238000005530 etching Methods 0.000 claims abstract description 40
- 238000010884 ion-beam technique Methods 0.000 claims abstract description 38
- 239000004020 conductor Substances 0.000 claims abstract description 36
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 18
- 229910052715 tantalum Inorganic materials 0.000 claims description 18
- 229910052721 tungsten Inorganic materials 0.000 claims description 18
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 16
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 14
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 14
- 239000010937 tungsten Substances 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 11
- 229910052782 aluminium Inorganic materials 0.000 claims description 10
- 229910052735 hafnium Inorganic materials 0.000 claims description 10
- 229910052750 molybdenum Inorganic materials 0.000 claims description 10
- 229910052742 iron Inorganic materials 0.000 claims description 9
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 claims description 8
- 229910052697 platinum Inorganic materials 0.000 claims description 8
- 229910052707 ruthenium Inorganic materials 0.000 claims description 8
- 239000000758 substrate Substances 0.000 claims description 8
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 7
- 229910017052 cobalt Inorganic materials 0.000 claims description 7
- 239000010941 cobalt Substances 0.000 claims description 7
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 7
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 claims description 7
- 239000011733 molybdenum Substances 0.000 claims description 7
- 230000001678 irradiating effect Effects 0.000 claims 2
- 239000010410 layer Substances 0.000 description 68
- 230000005415 magnetization Effects 0.000 description 12
- 230000006870 function Effects 0.000 description 10
- 230000000694 effects Effects 0.000 description 6
- 239000011229 interlayer Substances 0.000 description 6
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- ZGDWHDKHJKZZIQ-UHFFFAOYSA-N cobalt nickel Chemical compound [Co].[Ni].[Ni].[Ni] ZGDWHDKHJKZZIQ-UHFFFAOYSA-N 0.000 description 3
- OQCGPOBCYAOYSD-UHFFFAOYSA-N cobalt palladium Chemical compound [Co].[Co].[Co].[Pd].[Pd] OQCGPOBCYAOYSD-UHFFFAOYSA-N 0.000 description 3
- GUBSQCSIIDQXLB-UHFFFAOYSA-N cobalt platinum Chemical compound [Co].[Pt].[Pt].[Pt] GUBSQCSIIDQXLB-UHFFFAOYSA-N 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 229910019236 CoFeB Inorganic materials 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 2
- 230000005389 magnetism Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- ZDZZPLGHBXACDA-UHFFFAOYSA-N [B].[Fe].[Co] Chemical compound [B].[Fe].[Co] ZDZZPLGHBXACDA-UHFFFAOYSA-N 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- ZDVYABSQRRRIOJ-UHFFFAOYSA-N boron;iron Chemical compound [Fe]#B ZDVYABSQRRRIOJ-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000013077 target material Substances 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
- G11C11/161—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
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- H01L27/222—
-
- H01L43/08—
-
- H01L43/10—
-
- H01L43/12—
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B61/00—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N50/00—Galvanomagnetic devices
- H10N50/01—Manufacture or treatment
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N50/00—Galvanomagnetic devices
- H10N50/10—Magnetoresistive devices
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N50/00—Galvanomagnetic devices
- H10N50/80—Constructional details
- H10N50/85—Magnetic active materials
Definitions
- Embodiments described herein relate generally to a magnetoresistive memory device and a method of manufacturing the magnetoresistive memory device.
- a magnetoresistive memory device using a magnetoresistive effect element is known.
- FIG. 1 shows functional blocks of a magnetoresistive memory device of a first embodiment
- FIG. 2 is a circuit diagram of one memory cell of the first embodiment
- FIG. 3 shows a structure of part of the memory cell array of the first embodiment
- FIG. 4 shows an example of the state of magnetization of an MTJ element of the first embodiment
- FIG. 5 shows a state during a manufacturing process of part of the magnetoresistive memory device of the first embodiment
- FIG. 6 shows a state following that of FIG. 5 ;
- FIG. 7 shows a state following that of FIG. 6 ;
- FIG. 8 shows a state following that of FIG. 7 ;
- FIG. 9 shows a structure of part of a magnetoresistive memory device for reference.
- a magnetoresistive memory device includes a layer stack.
- the layer stack includes a first ferromagnet, an insulator on the first ferromagnet, and a second ferromagnet on the insulator.
- a nonmagnet is provided above the layer stack.
- a first conductor is provided on the nonmagnet.
- a hard mask is provided above the first conductor.
- the nonmagnet includes a material that is removed at a first etching rate against a first ion beam.
- the first conductor includes a material that is removed at a second etching rate against the first ion beam. The first etching rate is lower than the second etching rate.
- any step in a flow of a method of an embodiment is not limited to any illustrated order, and can occur in an order different from an illustrated order and/or can occur concurrently with another step.
- a phrase of a particular first component being “coupled” to another second component includes the first component being coupled to the second component either directly or via one or more components which are always or selectively conductive.
- FIG. 1 shows functional blocks of the magnetoresistive memory device according to the first embodiment.
- a magnetoresistive memory device 1 includes a memory cell array 11 , an input/output circuit 12 , a control circuit 13 , a row selection circuit 14 , a column selection circuit 15 , a write circuit 16 , and a read circuit 17 .
- the memory cell array 11 includes memory cells MC, word lines WL, bit lines BL, and bit lines /BL.
- One bit line BL and one bit line /BL constitute one bit line pair.
- the memory cell MC can store data in a non-volatile manner.
- Each memory cell MC is coupled to one word line WL and a pair of bit lines BL and /BL.
- Each word line WL is associated with a row.
- Each pair of bit lines BL and /BL is associated with a column. Selection of one row and selection of one or more columns specify one or more memory cells MC.
- the input/output circuit 12 receives various types of a control signal CNT, various types of a command CMD, an address signal ADD, and data (write data) DAT, for example, from a memory controller 2 , and transmits data (read data) DAT to, for example, the memory controller 2 .
- the row selection circuit 14 receives the address signal ADD from the input/output circuit 12 , and brings one word line WL corresponding to the row that is based on the received address signal ADD into a selected state.
- the column selection circuit 15 receives the address signal ADD from the input/output circuit 12 and brings bit lines BL corresponding to the column that is based on the received address signal ADD into a selected state.
- the control circuit 13 receives the control signal CNT and the command CMD from the input/output circuit 12 .
- the control circuit 13 controls the write circuit 16 and the read circuit 17 based on control instructed by the control signal CNT and the command CMD. Specifically, the control circuit 13 supplies voltages used for data writing to the write circuit 16 during the data writing to the memory cell array 11 . Further, the control circuit 13 supplies voltages used for data reading to the read circuit 17 during the reading of data from the memory cell array 11 .
- the write circuit 16 receives write data DAT from the input/output circuit 12 and supplies the voltages used for data writing to the column selection circuit 15 based on the control by the control circuit 13 and the write data DAT.
- the read circuit 17 includes a sense amplifier, and based on the control of the control circuit 13 , uses the voltages used for data reading to determine data stored in the memory cells MC. The determined data is supplied to the input/output circuit 12 as the read data DAT.
- FIG. 2 is a circuit diagram of one memory cell MC of the first embodiment.
- the memory cell MC includes a variable resistance element VR and a select transistor ST.
- the variable resistance element VR can be in a selected resistance state of two resistance states, and the resistance of one of the two resistance states is higher than the resistance of the other.
- the variable resistance element VR can switch between the low resistance state and the high resistance state, and can store one bit of data using the difference between the two resistance states.
- the variable resistance element VR exhibits, for example, a magnetoresistive effect, and includes, for example, a magnetic tunnel junction (MTJ) element.
- the MTJ element refers to a structure including an MTJ.
- the select transistor ST can be, for example, an n-type metal oxide semiconductor field effect transistor (MOSFET).
- MOSFET metal oxide semiconductor field effect transistor
- a variable resistance element VR is coupled to one bit line BL at its first end, and is coupled to a first end of the select transistor ST at its second end.
- a second end of the select transistor ST is coupled to the bit line /BL.
- the gate of the select transistor ST is coupled to one word line WL, and the source is coupled to the bit line /BL.
- Any switching element can be used as long as it can select the memory cell MC and allow for writing and reading data to and from the selected memory cell MC.
- Such a switching element includes, for example, a switching element having a two-terminal switching function.
- variable resistance element VR includes an MTJ element.
- FIG. 3 shows a structure of part of the memory cell array 11 of the first embodiment. More specifically, FIG. 1 shows the resistance change element VR of each of two adjacent memory cells MC and the periphery thereof.
- Two independent bottom electrodes 21 are provided above a substrate 20 .
- An inter-layer insulator 22 is provided in the area between the bottom electrodes 21 .
- the inter-layer insulator 22 fills, for example, the area between the bottom electrodes 21 .
- Each variable resistance element VR is provided on the upper face of each bottom electrode 21 .
- Each variable resistance element VR includes a layer stack 24 , a nonmagnet 35 , and a conductor 37 .
- the layer stack 24 exhibits a tunnel magnetoresistive effect and can function as an MTJ element.
- the layer stack 24 includes a ferromagnet 31 , an insulator 32 , and a ferromagnet 33 .
- the layer stack 24 may include an additional layer.
- the ferromagnet 31 is located on the upper face of the bottom electrode 21 and includes, for example, one or more of cobalt platinum (CoPt), cobalt nickel (CoNi), and cobalt palladium (CoPd), or is made of any one of CoPt, CoNi, and CoPd.
- CoPt cobalt platinum
- CoNi cobalt nickel
- CoPd cobalt palladium
- the insulator 32 is located on the upper face of the ferromagnet 31 .
- the insulator 32 includes a nonmagnetic insulator or is made of a nonmagnetic insulator.
- the insulator 32 includes or is made of magnesium oxide (MgO).
- the ferromagnet 33 is located on the upper face of the insulator 32 , and includes, for example, one or more of cobalt iron boron (CoFeB) and iron boride (FeB), or is made of any one of CoFeB and FeB.
- CoFeB cobalt iron boron
- FeB iron boride
- the variable resistance element VR may include an additional layer.
- a layer includes, for example, one or more conductors between the ferromagnet 31 and the bottom electrode 21 .
- the conductor has a function of facilitating the crystallinity of one or more of the ferromagnet 31 , the insulator 32 , and the ferromagnet 33 , for example, and can function as a so-called base layer or a buffer layer.
- the ferromagnets 31 and 33 have magnetization, as shown in FIG. 4 , and have for example, a magnetization easy axis along a direction passing through the interfaces of the ferromagnet 31 , the insulator 32 , and the ferromagnet 33 (indicated by arrows).
- the ferromagnets 31 and 32 may have a magnetization easy axis along the interfaces of the ferromagnet 31 , the insulator 32 , and the ferromagnet 33 .
- the direction of magnetization of the ferromagnet 31 remains unchanged by the normal operation of the magnetoresistive memory device 1 , that is, even by reading and writing of data, and can function as a so-called reference layer.
- the direction of magnetization of the ferromagnet 33 is variable, and can function as a so-called storage layer.
- the insulator 32 can function as a tunnel barrier.
- the layer stack 24 when the directions of magnetization of the ferromagnets 31 and 32 are parallel, the layer stack 24 exhibits a resistance value Rp. On the other hand, when the directions of magnetization of the ferromagnets 31 and 32 are antiparallel, the layer stack 24 exhibits a resistance value Rap.
- the resistance value Rap is higher than the resistance value Rp. States indicating two different resistance values can be assigned to two types of binary data, respectively.
- the side face of the layer stack 24 is tapered. That is, the diameter of a top face 24 T of the layer stack 24 is smaller than the diameter of a bottom face 24 B of the layer stack 24 . Alternatively, the area of the upper face 24 T of the layer stack 24 is smaller than the area of the bottom face 24 B of the layer stack 24 .
- the term “diameter” is not necessarily used for a circle, and does not require that the component for which the diameter is used be a circle. It refers to, for example, the linear distance from one end to another end in a shape close to a circle, and in the example of FIG. 3 , it indicates the length of the component along the x axis. As an example, it indicates the length on an imaginary straight line passing through the center, and can be used interchangeably with the width.
- the side face of the layer stack 24 has an inclination of, for example, an angle ⁇ 1 with respect to the z axis.
- a conductive nonmagnet 35 is provided on the top face of the layer stack 24 , that is, on the top face of the ferromagnet 33 , for example.
- the material of the nonmagnet 35 will be described later.
- the side face of the nonmagnet 35 is tapered.
- the side face of the nonmagnet 35 has an inclination of, for example, an angle ⁇ 2 with respect to the z axis. The angle ⁇ 2 is larger than the angle ⁇ 1 .
- the conductor 37 is provided on the top face of the nonmagnet 35 .
- the conductor 37 functions as a cap layer.
- the conductor 37 may be hereinafter referred to as a cap layer 37 .
- the cap layer 37 includes, for example, one or more of platinum (Pt), tungsten (W), tantalum (Ta), and ruthenium (Ru), or is made of any one of platinum (Pt), tungsten (W), tantalum (Ta), and ruthenium (Ru).
- the side face of the cap layer 37 extends, for example, along the z axis.
- a hard mask 38 is provided on the top face of the conductor 37 .
- the hard mask 38 is made of, for example, a conductor.
- the nonmagnet 35 has a first etching rate against ion beam etching (IBE) using a particular first ion beam described later.
- the cap layer 37 has a second etching rate for the IBE.
- the first etching rate is lower than the second etching rate.
- the nonmagnet 35 includes or is made of a material selected based at least in part on a kind of such first ion, the material of the cap layer 37 , and the IBE condition.
- the nonmagnet 35 may contain Ta, W, hafnium (Hf), iron (Fe), cobalt (Co), aluminum (Al), and molybdenum (Mo), or is made of any one of Ta, W, Hf, Fe, Co, Al, and Mo.
- the nonmagnet 35 contains an element which exhibits magnetism as a single substance, or in the case where such an element is a main component, an element that weakens largely or eliminates the magnetism to the nonmagnet 35 can be added to the nonmagnet 35 .
- the nonmagnet 35 may be an alloy of two or more of Ta, W, Hf, Fe, Co, Al, and Mo. Furthermore, the nonmagnet 35 may contain one or more borides of Ta, W, Hf, Fe, Co, Al, and Mo.
- a redeposited material 39 may lie on the side face of the nonmagnet 35 , the side face of the cap layer 37 , and part of the side face of the hard mask 38 .
- the redeposited material 39 includes materials of at least one of the ferromagnet 31 , the insulator 32 , the ferromagnet 33 , the nonmagnet 35 , and the cap layer 37 .
- the surface of the redeposited material 39 lies, for example, on the extension of the side face of the layer stack 24 .
- the surface of the redeposited material 39 and the surface of the layer stack 24 form a continuous flat surface.
- the side face of the structure consisting of a set of the hard mask 38 , the cap layer 37 , the nonmagnet 35 , the layer stack 24 , and the redeposited material 39 may be covered with a sidewall insulator.
- the hard mask 38 can be coupled to a conductor (not shown).
- An area other than the area in which the components shown in FIG. 3 are provided can be filled with an inter-layer insulator (not shown).
- FIGS. 5 to 8 sequentially show the state during the manufacturing process of the portion, which is shown in FIG. 3 , of the magnetoresistive memory device 1 of the first embodiment.
- the inter-layer insulator 22 and the bottom electrode 21 are formed above the surface extending along an xy plane of a substrate 20 .
- a layer stack 24 A is formed on the top face of the inter-layer insulator 22 and the top face of the bottom electrode 21 .
- the layer stack 24 A is later processed into the layer stack 24 and includes the same material layers as the material layers included in the layer stack 24 .
- the layer stack 24 A includes a ferromagnet 31 A, an insulator 32 A, and a ferromagnet 33 A.
- the ferromagnet 31 A, the insulator 32 A, and the ferromagnet 33 A include the same materials as the ferromagnet 31 , the insulator 32 , and the ferromagnet 33 , respectively.
- the ferromagnet 31 A lies on the top face of the inter-layer insulator 22 and the top face of the bottom electrode.
- the insulator 32 A lies on the upper face of the ferromagnet 31 A.
- the ferromagnet 33 A lies on the top face of the insulator 32 A.
- a nonmagnet 35 A is formed on the top face of the layer stack 24 A.
- the nonmagnet 35 A is later processed into the nonmagnet 35 , and includes the same material as the nonmagnet 35 .
- a conductor 37 A is formed on the top face of the nonmagnet 35 A.
- the conductor 37 A is later processed into the conductor 37 and includes the same material as the conductor 37 .
- a hard mask 38 A is formed on the top face of the conductor 37 A.
- the hard mask 38 A remains in areas where the cap layers 37 are to be formed and have openings 41 in the remaining areas.
- the openings 41 extend from the top face to the bottom face of the hard mask 38 A.
- the structure obtained by the process described so far is etched by the first IBE.
- the ions of the first IBE can be, for example, argon.
- the angle of the ion beam IB 1 in the first IBE with respect to the normal to the surface of the substrate 20 that is, the angle ⁇ I 1 with respect to the z axis, falls within a first range.
- the angle of an ion beam with respect to z-axis may be referred to simply as the angle of the ion beam.
- the etching rate is different based on the angle of the ion beam.
- a material 42 removed from the etching-target material by the IBE may be deposited on the surrounding components. The material thus redeposited is also removed again if the etching rate of the IBE is high.
- the angle of the ion beam IB 1 in the first IBE is desired to be able to sufficiently suppress such redeposition, and the first range has, for example, a range including the highest etching rate. Specifically, the first range ranges, for example, from 30° to 60°.
- the ion beam having a trajectory such as that of the ion beam IB 1 a may be blocked by the hard mask 38 A and may not reach a deep area of the opening 41 (an area closer to the substrate 20 ).
- the variable resistance element VR in order to arrange the variable resistance element VR at a high density, the narrower the openings 41 of the hard mask 38 A, the shallower area of the openings 41 (an area farther from the substrate 20 ) the ion beam can reach.
- the conductor 37 A is separated into several portions by the first IBE to form the cap layers 37
- the nonmagnet 35 A is separated into several portions to form the nonmagnets 35 B.
- the nonmagnet 35 A has the first etching rate
- the conductor 37 A has the second etching rate higher than the first etching rate. Therefore, the side face of the nonmagnet 35 A is etched less than the side face of the conductor 37 A by the first IBE, and the diameter (or width) D 1 of the nonmagnet 35 B is larger than the diameter (or width) D 2 of the cap layer 37 .
- the diameter D 1 is, for example, the diameter of the top face of the nonmagnet 35 B
- the diameter D 2 is, for example, the diameter of the bottom face of the cap layer 37 .
- ion beams IB 1 of the first IBE are blocked by the hard mask 38 A and do not separate the layer stack 24 A into portions.
- the upper part of the layer stack 24 A is divided into portions, and the lower part is not divided.
- the ferromagnet 33 A is divided into ferromagnets 33 B with each lying a hard mask 38 A
- the insulator 32 A is divided into insulators 32 B with each lying below a remaining pattern of hard mask 38 A.
- the ferromagnet 31 A is processed into a ferromagnet 31 B having a recess 31 BD at the bottom of each opening 41 without being divided into portions each of which would lie below the hard mask 38 A.
- the lower portion of the hard mask 38 A of the layer stack 24 A (hereinafter referred to as a residual portion 24 AP 1 of the layer stack 24 A) has a width larger than a width D 2 of the cap layer 37 due to the nonmagnet 35 B having a width larger than the width D 2 of the cap layer 37 .
- the width of the residual portion 24 AP 1 of the stacked structure 24 A is larger than the width D 2 of the cap layer 37 at any height.
- the upper face of the hard mask 38 A is lowered by the first IBE.
- the material removed from the etching target by the first IBE may be redeposited on the surrounding components. However, since the first IBE has a high angle and provides a high etching rate to the etching target, the redeposited material is again removed by etching and the amount of redeposition in the first IBE is suppressed.
- the structure obtained by the process described so far is etched by a second IBE.
- the ions of the second IBE can be, for example, argon.
- the angle ⁇ I 2 of the ion beam in the second IBE falls within a second range.
- the ion beam is intended to reach a lower part of the layer stack 24 A through the openings 41 .
- the second range is, for example, 0° to 30°
- the angle ⁇ I 2 of the ion beam in the second IBE is, for example, 10° . Since such an ion beam having a low angle is used, the etching rate in the second IBE is low, at least lower than the etching rate in the first IBE.
- some ion beams IB 2 in the second IBE reach a lower part of the layer stack 24 A, particularly the recess 31 BD of the ferromagnet 31 B.
- the position of the bottom of the recess 31 BD is lowered, and the width of the residual portion 24 AP 1 of the layer stack 24 A is narrowed.
- the ion beam having a trajectory such as an ion beam IB 2 a is blocked by the nonmagnet 35 B and hardly reaches the region near the lower part of the nonmagnet 35 B.
- the upper face of the hard mask 38 A is lowered by the second IBE to form a hard mask 38 B.
- the material 42 removed from the etching target may be deposited on the surrounding components.
- the second IBE cannot sufficiently suppress the progress of the redeposition, and the redeposition of the material 42 in the second IBE more easily progresses than the redeposition in the first IBE.
- the second IBE of FIG. 7 is continued.
- the ferromagnet 31 B is formed into ferromagnets 31 by the second IBE.
- the nonmagnets 35 B are also slowly etched by the second IBE to form the nonmagnets 35 . While the top faces of the nonmagnets 35 B are etched, the ion beam IB 2 hardly or does not reach the ferromagnets 33 B and the insulators 32 . Thus, during this period, scattering of the material 42 removed from the ferromagnets 33 B and the insulators 32 B is suppressed, and redeposition by the material 42 from the ferromagnets 33 B and the insulators 32 B is suppressed.
- the ion beam IB 2 comes to reach a ferromagnets 33 B and insulators 32 B, and the ferromagnets 33 B and the insulators 32 B are formed into the ferromagnets 33 and the insulators 32 by the second IBE, respectively.
- the top face of the hard mask 38 B is lowered by the second IBE, and becomes the hard mask 38 .
- the material 42 removed from the etching target is deposited on the surrounding components, and as shown in FIG. 3 , the redeposited material 39 may be formed by the material 42 .
- the magnetoresistive memory device 1 including the high-performance variable resistance elements VR can be realized.
- the details are as follows.
- FIG. 9 shows a state in a manufacturing process of a magnetoresistive memory device 100 for reference. Unlike the magnetoresistive memory device 1 of FIG. 3 , the magnetoresistive memory device 100 does not include the nonmagnet 35 .
- the process of FIG. 9 corresponds to the process of FIGS. 7 and 8 of the first embodiment.
- the structure shown in FIG. 9 is etched by the second IBE using a low angle ion beam similar to FIG. 7 .
- the second IBE has a low etching rate to the etching target. Therefore, the etched material is likely to be redeposited on the surrounding components.
- the ion beam IB 2 a that has a trajectory interrupted by the top face of the nonmagnets 35 and does not reach the layer stack 24 A in the structure of FIG. 7 etches the ferromagnets 33 A from the start of the second IBE.
- the etching rate of the second IBE is low, the removal of the redeposited material 42 removed from the ferromagnets 33 A is slow, and the redeposition of the material 42 progresses. Therefore, redeposited materials 51 are formed on the side faces of the ferromagnets 31 , the insulators 32 , the ferromagnets 33 , the cap layers 37 , and the hard masks 38 . Even when the second IBE is finished, in a case where a redeposited material 51 remains on the side wall of an insulator 32 , the redeposited material 51 may cause partial or full electrical conduction between the ferromagnets 31 and 33 . This may suppress production of the designed and intended magnetoresistive effect of the layer stacks 24 , and may disable the layer stacks 24 from functioning as MTJ elements.
- the variable resistance element VR includes the nonmagnet 35 . Since the nonmagnet 35 contains a material having an etching rate lower than that of the cap layer 37 with respect to a particular IBE, the nonmagnet 35 A, which is formed into the nonmagnet 35 , has a diameter larger than that of the conductor 37 A as a result of the IBE using a high angle ion beam performed earlier (for example, the first IBE).
- the IBE using a low angle ion beam performed after the IBE using a high angle ion beam (for example, the second IBE)
- some of ion beams (for example, the IB 2 a ) is blocked by the top face of the nonmagnet 35 B until the corner of the top face of nonmagnet 35 A is scrapped and does not reach the ferromagnet 33 B. Therefore, the redeposition of the material 42 on the side face of the insulator 32 in the second IBE is suppressed, and the conduction between the ferromagnets 31 and 33 is suppressed. Therefore, it is possible to make the layer stack 24 that can exhibit the intended magnetoresistive effect.
- the first embodiment relates to an example in which the ferromagnet 31 under the insulator 32 functions as a reference layer and the ferromagnet 33 on the insulator 32 functions as a storage layer.
- the first embodiment is not limited to this example, and can be applied to an example in which the ferromagnet 31 is located on the insulator 32 and the ferromagnet 33 is located under the insulator 32 .
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Abstract
Description
- This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-48676, filed Mar. 15, 2019, the entire contents of which are incorporated herein by reference.
- Embodiments described herein relate generally to a magnetoresistive memory device and a method of manufacturing the magnetoresistive memory device.
- A magnetoresistive memory device using a magnetoresistive effect element is known.
-
FIG. 1 shows functional blocks of a magnetoresistive memory device of a first embodiment; -
FIG. 2 is a circuit diagram of one memory cell of the first embodiment; -
FIG. 3 shows a structure of part of the memory cell array of the first embodiment; -
FIG. 4 shows an example of the state of magnetization of an MTJ element of the first embodiment; -
FIG. 5 shows a state during a manufacturing process of part of the magnetoresistive memory device of the first embodiment; -
FIG. 6 shows a state following that ofFIG. 5 ; -
FIG. 7 shows a state following that ofFIG. 6 ; -
FIG. 8 shows a state following that ofFIG. 7 ; and -
FIG. 9 shows a structure of part of a magnetoresistive memory device for reference. - According to an embodiment, a magnetoresistive memory device includes a layer stack. The layer stack includes a first ferromagnet, an insulator on the first ferromagnet, and a second ferromagnet on the insulator. A nonmagnet is provided above the layer stack. A first conductor is provided on the nonmagnet. A hard mask is provided above the first conductor. The nonmagnet includes a material that is removed at a first etching rate against a first ion beam. The first conductor includes a material that is removed at a second etching rate against the first ion beam. The first etching rate is lower than the second etching rate.
- Embodiments will now be described with reference to the figures.
- In the following description, components with substantially the same functionalities and configurations will be referred to with the same reference numerals, and repeated descriptions may be omitted. The figures are schematic, and the relations between the thickness and the area of a plane of a layer and ratios of thicknesses of layers may differ from actual ones.
- The entire description for a particular embodiment also applies to another embodiment unless it is explicitly mentioned otherwise or obviously eliminated. Each embodiment illustrates the device and method for materializing the technical idea of that embodiment, and the technical idea of an embodiment does not specify the quality of the material, shape, structure, arrangement of components, etc. to the following.
- Moreover, any step in a flow of a method of an embodiment is not limited to any illustrated order, and can occur in an order different from an illustrated order and/or can occur concurrently with another step.
- In the specification and the claims, a phrase of a particular first component being “coupled” to another second component includes the first component being coupled to the second component either directly or via one or more components which are always or selectively conductive.
- <1.1. Configuration (Structure)>
-
FIG. 1 shows functional blocks of the magnetoresistive memory device according to the first embodiment. As shown inFIG. 1 , a magnetoresistive memory device 1 includes amemory cell array 11, an input/output circuit 12, acontrol circuit 13, arow selection circuit 14, acolumn selection circuit 15, awrite circuit 16, and aread circuit 17. - The
memory cell array 11 includes memory cells MC, word lines WL, bit lines BL, and bit lines /BL. One bit line BL and one bit line /BL constitute one bit line pair. - The memory cell MC can store data in a non-volatile manner. Each memory cell MC is coupled to one word line WL and a pair of bit lines BL and /BL. Each word line WL is associated with a row. Each pair of bit lines BL and /BL is associated with a column. Selection of one row and selection of one or more columns specify one or more memory cells MC.
- The input/
output circuit 12 receives various types of a control signal CNT, various types of a command CMD, an address signal ADD, and data (write data) DAT, for example, from amemory controller 2, and transmits data (read data) DAT to, for example, thememory controller 2. - The
row selection circuit 14 receives the address signal ADD from the input/output circuit 12, and brings one word line WL corresponding to the row that is based on the received address signal ADD into a selected state. - The
column selection circuit 15 receives the address signal ADD from the input/output circuit 12 and brings bit lines BL corresponding to the column that is based on the received address signal ADD into a selected state. - The
control circuit 13 receives the control signal CNT and the command CMD from the input/output circuit 12. Thecontrol circuit 13 controls thewrite circuit 16 and theread circuit 17 based on control instructed by the control signal CNT and the command CMD. Specifically, thecontrol circuit 13 supplies voltages used for data writing to thewrite circuit 16 during the data writing to thememory cell array 11. Further, thecontrol circuit 13 supplies voltages used for data reading to theread circuit 17 during the reading of data from thememory cell array 11. - The
write circuit 16 receives write data DAT from the input/output circuit 12 and supplies the voltages used for data writing to thecolumn selection circuit 15 based on the control by thecontrol circuit 13 and the write data DAT. - The
read circuit 17 includes a sense amplifier, and based on the control of thecontrol circuit 13, uses the voltages used for data reading to determine data stored in the memory cells MC. The determined data is supplied to the input/output circuit 12 as the read data DAT. -
FIG. 2 is a circuit diagram of one memory cell MC of the first embodiment. The memory cell MC includes a variable resistance element VR and a select transistor ST. In a steady state, the variable resistance element VR can be in a selected resistance state of two resistance states, and the resistance of one of the two resistance states is higher than the resistance of the other. The variable resistance element VR can switch between the low resistance state and the high resistance state, and can store one bit of data using the difference between the two resistance states. The variable resistance element VR exhibits, for example, a magnetoresistive effect, and includes, for example, a magnetic tunnel junction (MTJ) element. The MTJ element refers to a structure including an MTJ. - The select transistor ST can be, for example, an n-type metal oxide semiconductor field effect transistor (MOSFET).
- A variable resistance element VR is coupled to one bit line BL at its first end, and is coupled to a first end of the select transistor ST at its second end. A second end of the select transistor ST is coupled to the bit line /BL. The gate of the select transistor ST is coupled to one word line WL, and the source is coupled to the bit line /BL. Although an example is described in which the memory cell MC includes the three-terminal select transistor ST as a switching element, the memory cell MC is not limited to this form. Any switching element can be used as long as it can select the memory cell MC and allow for writing and reading data to and from the selected memory cell MC. Such a switching element includes, for example, a switching element having a two-terminal switching function.
- The following description is based on an example in which the variable resistance element VR includes an MTJ element.
-
FIG. 3 shows a structure of part of thememory cell array 11 of the first embodiment. More specifically,FIG. 1 shows the resistance change element VR of each of two adjacent memory cells MC and the periphery thereof. - Two independent
bottom electrodes 21 are provided above asubstrate 20. Aninter-layer insulator 22 is provided in the area between thebottom electrodes 21. Theinter-layer insulator 22 fills, for example, the area between thebottom electrodes 21. - One variable resistance element VR is provided on the upper face of each
bottom electrode 21. Each variable resistance element VR includes alayer stack 24, anonmagnet 35, and aconductor 37. - The layer stack 24 exhibits a tunnel magnetoresistive effect and can function as an MTJ element. As such an example, the
layer stack 24 includes aferromagnet 31, aninsulator 32, and aferromagnet 33. Thelayer stack 24 may include an additional layer. - The
ferromagnet 31 is located on the upper face of thebottom electrode 21 and includes, for example, one or more of cobalt platinum (CoPt), cobalt nickel (CoNi), and cobalt palladium (CoPd), or is made of any one of CoPt, CoNi, and CoPd. - The
insulator 32 is located on the upper face of theferromagnet 31. Theinsulator 32 includes a nonmagnetic insulator or is made of a nonmagnetic insulator. For example, theinsulator 32 includes or is made of magnesium oxide (MgO). - The
ferromagnet 33 is located on the upper face of theinsulator 32, and includes, for example, one or more of cobalt iron boron (CoFeB) and iron boride (FeB), or is made of any one of CoFeB and FeB. - The variable resistance element VR may include an additional layer. Such a layer includes, for example, one or more conductors between the
ferromagnet 31 and thebottom electrode 21. The conductor has a function of facilitating the crystallinity of one or more of theferromagnet 31, theinsulator 32, and theferromagnet 33, for example, and can function as a so-called base layer or a buffer layer. - The
ferromagnets FIG. 4 , and have for example, a magnetization easy axis along a direction passing through the interfaces of theferromagnet 31, theinsulator 32, and the ferromagnet 33 (indicated by arrows). Theferromagnets ferromagnet 31, theinsulator 32, and theferromagnet 33. - The direction of magnetization of the
ferromagnet 31 remains unchanged by the normal operation of the magnetoresistive memory device 1, that is, even by reading and writing of data, and can function as a so-called reference layer. On the other hand, the direction of magnetization of theferromagnet 33 is variable, and can function as a so-called storage layer. Theinsulator 32 can function as a tunnel barrier. - Specifically, when the directions of magnetization of the
ferromagnets layer stack 24 exhibits a resistance value Rp. On the other hand, when the directions of magnetization of theferromagnets layer stack 24 exhibits a resistance value Rap. The resistance value Rap is higher than the resistance value Rp. States indicating two different resistance values can be assigned to two types of binary data, respectively. - When the write current IwP flows from the
ferromagnet 33 toward theferromagnet 31, the magnetization direction of theferromagnet 33 becomes parallel to the magnetization direction of theferromagnet 31. On the other hand, when a write current IwP flows from theferromagnet 31 toward theferromagnet 33, the magnetization direction of theferromagnet 33 becomes antiparallel to the magnetization direction of theferromagnet 31. - Referring back to
FIG. 3 , the side face of thelayer stack 24 is tapered. That is, the diameter of atop face 24T of thelayer stack 24 is smaller than the diameter of abottom face 24B of thelayer stack 24. Alternatively, the area of theupper face 24T of thelayer stack 24 is smaller than the area of thebottom face 24B of thelayer stack 24. As used herein, the term “diameter” is not necessarily used for a circle, and does not require that the component for which the diameter is used be a circle. It refers to, for example, the linear distance from one end to another end in a shape close to a circle, and in the example ofFIG. 3 , it indicates the length of the component along the x axis. As an example, it indicates the length on an imaginary straight line passing through the center, and can be used interchangeably with the width. The side face of thelayer stack 24 has an inclination of, for example, an angle θ1 with respect to the z axis. - A
conductive nonmagnet 35 is provided on the top face of thelayer stack 24, that is, on the top face of theferromagnet 33, for example. The material of the nonmagnet 35 will be described later. The side face of the nonmagnet 35 is tapered. The side face of the nonmagnet 35 has an inclination of, for example, an angle θ2 with respect to the z axis. The angle θ2 is larger than the angle θ1. - The
conductor 37 is provided on the top face of thenonmagnet 35. Theconductor 37 functions as a cap layer. Theconductor 37 may be hereinafter referred to as acap layer 37. Thecap layer 37 includes, for example, one or more of platinum (Pt), tungsten (W), tantalum (Ta), and ruthenium (Ru), or is made of any one of platinum (Pt), tungsten (W), tantalum (Ta), and ruthenium (Ru). The side face of thecap layer 37 extends, for example, along the z axis. - A
hard mask 38 is provided on the top face of theconductor 37. Thehard mask 38 is made of, for example, a conductor. - Next, the material of the nonmagnet 35 will be described. The
nonmagnet 35 has a first etching rate against ion beam etching (IBE) using a particular first ion beam described later. Thecap layer 37 has a second etching rate for the IBE. The first etching rate is lower than the second etching rate. Thenonmagnet 35 includes or is made of a material selected based at least in part on a kind of such first ion, the material of thecap layer 37, and the IBE condition. For example, thenonmagnet 35 may contain Ta, W, hafnium (Hf), iron (Fe), cobalt (Co), aluminum (Al), and molybdenum (Mo), or is made of any one of Ta, W, Hf, Fe, Co, Al, and Mo. When the nonmagnet 35 contains an element which exhibits magnetism as a single substance, or in the case where such an element is a main component, an element that weakens largely or eliminates the magnetism to the nonmagnet 35 can be added to thenonmagnet 35. - Alternatively, the
nonmagnet 35 may be an alloy of two or more of Ta, W, Hf, Fe, Co, Al, and Mo. Furthermore, thenonmagnet 35 may contain one or more borides of Ta, W, Hf, Fe, Co, Al, and Mo. - A redeposited
material 39 may lie on the side face of the nonmagnet 35, the side face of thecap layer 37, and part of the side face of thehard mask 38. The redepositedmaterial 39 includes materials of at least one of theferromagnet 31, theinsulator 32, theferromagnet 33, thenonmagnet 35, and thecap layer 37. The surface of the redepositedmaterial 39 lies, for example, on the extension of the side face of thelayer stack 24. For example, the surface of the redepositedmaterial 39 and the surface of thelayer stack 24 form a continuous flat surface. - The side face of the structure consisting of a set of the
hard mask 38, thecap layer 37, thenonmagnet 35, thelayer stack 24, and the redepositedmaterial 39 may be covered with a sidewall insulator. - The
hard mask 38 can be coupled to a conductor (not shown). An area other than the area in which the components shown inFIG. 3 are provided can be filled with an inter-layer insulator (not shown). - <1.2. Manufacturing Method>
- With reference to
FIGS. 5 to 8 , a method of manufacturing the structure ofFIG. 3 will be described.FIGS. 5 to 8 sequentially show the state during the manufacturing process of the portion, which is shown inFIG. 3 , of the magnetoresistive memory device 1 of the first embodiment. - As shown in
FIG. 5 , theinter-layer insulator 22 and thebottom electrode 21 are formed above the surface extending along an xy plane of asubstrate 20. Alayer stack 24A is formed on the top face of theinter-layer insulator 22 and the top face of thebottom electrode 21. Thelayer stack 24A is later processed into thelayer stack 24 and includes the same material layers as the material layers included in thelayer stack 24. According to the current example, thelayer stack 24A includes aferromagnet 31A, aninsulator 32A, and aferromagnet 33A. - The
ferromagnet 31A, theinsulator 32A, and theferromagnet 33A include the same materials as theferromagnet 31, theinsulator 32, and theferromagnet 33, respectively. Theferromagnet 31A lies on the top face of theinter-layer insulator 22 and the top face of the bottom electrode. Theinsulator 32A lies on the upper face of theferromagnet 31A. Theferromagnet 33A lies on the top face of theinsulator 32A. - A
nonmagnet 35A is formed on the top face of thelayer stack 24A. Thenonmagnet 35A is later processed into thenonmagnet 35, and includes the same material as thenonmagnet 35. Aconductor 37A is formed on the top face of thenonmagnet 35A. Theconductor 37A is later processed into theconductor 37 and includes the same material as theconductor 37. - Furthermore, a
hard mask 38A is formed on the top face of theconductor 37A. Thehard mask 38A remains in areas where the cap layers 37 are to be formed and haveopenings 41 in the remaining areas. Theopenings 41 extend from the top face to the bottom face of thehard mask 38A. - As shown in
FIG. 6 , the structure obtained by the process described so far is etched by the first IBE. The ions of the first IBE can be, for example, argon. The angle of the ion beam IB1 in the first IBE with respect to the normal to the surface of thesubstrate 20, that is, the angle θI1 with respect to the z axis, falls within a first range. In the following description, the angle of an ion beam with respect to z-axis may be referred to simply as the angle of the ion beam. - In general, when a component extending along the xy plane is partially removed and patterned by the IBE, the etching rate is different based on the angle of the ion beam. Also, a
material 42 removed from the etching-target material by the IBE may be deposited on the surrounding components. The material thus redeposited is also removed again if the etching rate of the IBE is high. The angle of the ion beam IB1 in the first IBE is desired to be able to sufficiently suppress such redeposition, and the first range has, for example, a range including the highest etching rate. Specifically, the first range ranges, for example, from 30° to 60°. - On the other hand, when the angle of the ion beam is high, the ion beam having a trajectory such as that of the ion beam IB1 a may be blocked by the
hard mask 38A and may not reach a deep area of the opening 41 (an area closer to the substrate 20). In particular, in order to arrange the variable resistance element VR at a high density, the narrower theopenings 41 of thehard mask 38A, the shallower area of the openings 41 (an area farther from the substrate 20) the ion beam can reach. - The
conductor 37A is separated into several portions by the first IBE to form the cap layers 37, and thenonmagnet 35A is separated into several portions to form thenonmagnets 35B. As described above, for the first IBE, thenonmagnet 35A has the first etching rate, and theconductor 37A has the second etching rate higher than the first etching rate. Therefore, the side face of thenonmagnet 35A is etched less than the side face of theconductor 37A by the first IBE, and the diameter (or width) D1 of the nonmagnet 35B is larger than the diameter (or width) D2 of thecap layer 37. The diameter D1 is, for example, the diameter of the top face of the nonmagnet 35B, and the diameter D2 is, for example, the diameter of the bottom face of thecap layer 37. - Some of ion beams IB1 of the first IBE are blocked by the
hard mask 38A and do not separate thelayer stack 24A into portions. In the example ofFIG. 6 , the upper part of thelayer stack 24A is divided into portions, and the lower part is not divided. In the example where thecurrent layer stack 24A includes theferromagnet 31A, theinsulator 32A, and theferromagnet 33A, theferromagnet 33A is divided intoferromagnets 33B with each lying ahard mask 38A, and theinsulator 32A is divided intoinsulators 32B with each lying below a remaining pattern ofhard mask 38A. On the other hand, theferromagnet 31A is processed into aferromagnet 31B having a recess 31BD at the bottom of eachopening 41 without being divided into portions each of which would lie below thehard mask 38A. - The lower portion of the
hard mask 38A of thelayer stack 24A (hereinafter referred to as a residual portion 24AP1 of thelayer stack 24A) has a width larger than a width D2 of thecap layer 37 due to the nonmagnet 35B having a width larger than the width D2 of thecap layer 37. As an example, the width of the residual portion 24AP1 of the stackedstructure 24A is larger than the width D2 of thecap layer 37 at any height. - The upper face of the
hard mask 38A is lowered by the first IBE. - The material removed from the etching target by the first IBE may be redeposited on the surrounding components. However, since the first IBE has a high angle and provides a high etching rate to the etching target, the redeposited material is again removed by etching and the amount of redeposition in the first IBE is suppressed.
- As shown in
FIG. 7 , the structure obtained by the process described so far is etched by a second IBE. The ions of the second IBE can be, for example, argon. - The angle θI2 of the ion beam in the second IBE falls within a second range. In the second IBE, the ion beam is intended to reach a lower part of the
layer stack 24A through theopenings 41. For this purpose, the second range is, for example, 0° to 30°, and the angle θI2 of the ion beam in the second IBE is, for example, 10° . Since such an ion beam having a low angle is used, the etching rate in the second IBE is low, at least lower than the etching rate in the first IBE. - By the second IBE using the ion beam having such an angle, some ion beams IB2 in the second IBE reach a lower part of the
layer stack 24A, particularly the recess 31BD of theferromagnet 31B. As a result, with the progress of the second IBE, the position of the bottom of the recess 31BD is lowered, and the width of the residual portion 24AP1 of thelayer stack 24A is narrowed. - On the other hand, the ion beam having a trajectory such as an ion beam IB2a is blocked by the
nonmagnet 35B and hardly reaches the region near the lower part of the nonmagnet 35B. - The upper face of the
hard mask 38A is lowered by the second IBE to form ahard mask 38B. - Also by the second IBE, the
material 42 removed from the etching target may be deposited on the surrounding components. In particular, because the etching rate of the second IBE is low, the second IBE cannot sufficiently suppress the progress of the redeposition, and the redeposition of the material 42 in the second IBE more easily progresses than the redeposition in the first IBE. - As shown in
FIG. 8 , the second IBE ofFIG. 7 is continued. Theferromagnet 31B is formed intoferromagnets 31 by the second IBE. The nonmagnets 35B are also slowly etched by the second IBE to form thenonmagnets 35. While the top faces of thenonmagnets 35B are etched, the ion beam IB2 hardly or does not reach theferromagnets 33B and theinsulators 32. Thus, during this period, scattering of the material 42 removed from theferromagnets 33B and theinsulators 32B is suppressed, and redeposition by the material 42 from theferromagnets 33B and theinsulators 32B is suppressed. - As the top faces of the
nonmagnets 35A are etched, the ion beam IB2 comes to reach aferromagnets 33B andinsulators 32B, and theferromagnets 33B and theinsulators 32B are formed into theferromagnets 33 and theinsulators 32 by the second IBE, respectively. - Further, the top face of the
hard mask 38B is lowered by the second IBE, and becomes thehard mask 38. - By the second IBE, the
material 42 removed from the etching target is deposited on the surrounding components, and as shown inFIG. 3 , the redepositedmaterial 39 may be formed by thematerial 42. - <1.3. Advantages (Effects)>
- According to the first embodiment, the magnetoresistive memory device 1 including the high-performance variable resistance elements VR can be realized. The details are as follows.
-
FIG. 9 shows a state in a manufacturing process of a magnetoresistive memory device 100 for reference. Unlike the magnetoresistive memory device 1 ofFIG. 3 , the magnetoresistive memory device 100 does not include thenonmagnet 35. The process ofFIG. 9 corresponds to the process ofFIGS. 7 and 8 of the first embodiment. - The structure shown in
FIG. 9 is etched by the second IBE using a low angle ion beam similar toFIG. 7 . As described with reference toFIG. 7 , the second IBE has a low etching rate to the etching target. Therefore, the etched material is likely to be redeposited on the surrounding components. In the structure shown inFIG. 9 , the ion beam IB2a that has a trajectory interrupted by the top face of thenonmagnets 35 and does not reach thelayer stack 24A in the structure ofFIG. 7 etches theferromagnets 33A from the start of the second IBE. On the other hand, since the etching rate of the second IBE is low, the removal of the redepositedmaterial 42 removed from theferromagnets 33A is slow, and the redeposition of thematerial 42 progresses. Therefore, redepositedmaterials 51 are formed on the side faces of theferromagnets 31, theinsulators 32, theferromagnets 33, the cap layers 37, and the hard masks 38. Even when the second IBE is finished, in a case where a redepositedmaterial 51 remains on the side wall of aninsulator 32, the redepositedmaterial 51 may cause partial or full electrical conduction between theferromagnets - According to the first embodiment, the variable resistance element VR includes the
nonmagnet 35. Since the nonmagnet 35 contains a material having an etching rate lower than that of thecap layer 37 with respect to a particular IBE, thenonmagnet 35A, which is formed into thenonmagnet 35, has a diameter larger than that of theconductor 37A as a result of the IBE using a high angle ion beam performed earlier (for example, the first IBE). For this reason, in the IBE using a low angle ion beam performed after the IBE using a high angle ion beam (for example, the second IBE), some of ion beams (for example, the IB2 a) is blocked by the top face of the nonmagnet 35B until the corner of the top face ofnonmagnet 35A is scrapped and does not reach theferromagnet 33B. Therefore, the redeposition of the material 42 on the side face of theinsulator 32 in the second IBE is suppressed, and the conduction between theferromagnets layer stack 24 that can exhibit the intended magnetoresistive effect. - <1.4. Modification and Others>
- The first embodiment relates to an example in which the
ferromagnet 31 under theinsulator 32 functions as a reference layer and theferromagnet 33 on theinsulator 32 functions as a storage layer. The first embodiment is not limited to this example, and can be applied to an example in which theferromagnet 31 is located on theinsulator 32 and theferromagnet 33 is located under theinsulator 32. - While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Claims (16)
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- 2019-09-09 US US16/565,316 patent/US20200294566A1/en not_active Abandoned
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2021
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Also Published As
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US20220028441A1 (en) | 2022-01-27 |
CN111697129B (en) | 2023-10-27 |
TW202036888A (en) | 2020-10-01 |
JP2020150217A (en) | 2020-09-17 |
US11682441B2 (en) | 2023-06-20 |
TWI715128B (en) | 2021-01-01 |
CN111697129A (en) | 2020-09-22 |
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