TWI317125B - Structure of magnetic random access memory using spin-torque transfer writing and method for manufacturing same - Google Patents

Description

1317125, P950101 21247twf.doc/006 IX. Description of the Invention: • [Technical Field of the Invention] The present invention generally relates to a magnetic random access memory (MRAM) 'and more specifically' A novel structure of a magnetic random access memory device that is programmed by spin torque transfer and a method of fabricating the structure. [Prior Art] φ Conventional non-volatile magnetic random access memory elements are operated by using cross-point magnetic field switching. The field is generated by current passing through a bit line disposed above and below the element. The ferromagnetic free layer used as a writable plate in the element has a coercivity field smaller than the magnetic field generated by the bit line. As a result, the magnetization direction of the ferromagnetic free layer is changed to be aligned with the direction of the magnetic field. However, this method of operation limits the ability to scale down MRAM components due to the large current required. When a plurality of components are configured as an MRAM array, since the magnetic field of the component affects the ferromagnetic free layer of the adjacent MRAM component, the operation additionally has a problem of write disturb. On the other hand, the MRA element can also be used as a method of spin torque transfer for write operations. The operation depends on the current density of the magnetic tunnel juncti〇n (MTJ) stack, not the current, and the amplitude. The MTJ stack basically comprises a ferromagnetic free layer and a reference layer having a magnetization direction. The electrons pass through the reference layer and are polarized spin. Since the electrons flow through the ferromagnetic free layer from the reference layer: the second electricity 1317125, P950101 21247twf.doc/006 is based on the precessing and damping of the Landau_Lifshitz_Gilbert 'LLG equation ( The adjustment of the term) gradually changes the magnetization direction of the ferromagnetic free layer. In addition, the programmed unit can be written without interference by using the spin torque transfer current through the MTJ stack. This allows self-write, i.e., no additional bit lines are used for writing. As a result, the MRAM element can be further scaled down.

The & MTJ stack can also utilize the second reference layer. The second reference layer has a magnetization direction opposite to the magnetization direction of the first layer. The subsequent magnetization of the free layer = to ^ by the operation of the writer - the flow of electrons in the direction of the component = fixed. For example, for current flowing through the first reference layer to the second reference layer, the magnetization direction of the free layer is aligned with the magnetization direction of the first reference magnet. The required spin torque transfer current density is strongly dependent on the size of the MTJ stack. However, since the MTJ stack becomes smaller, the component & is lost due to the superparamagnetic memory. Since the high write current density is required to achieve self-domain change, the thermal energy m randomly varies the atomic magnetic moment in the material. This phenomenon only contributes to the instability of the ferromagnetic free layer and also contributes to the reference stability. The problem of write disturb in the enemy AM array also continues. Therefore, it is necessary to use an MRAM element which requires a low write current density and can maintain a stable magnetic state in the element itself and in the _. SUMMARY OF THE INVENTION The first embodiment of the present invention includes a nano magnetic element 6 1317125 P950101 21247twf.doc/006 into operation fine, money _ self-hard mis-mram element; ferromagnetic f free structure and second hard Lai. The current density _ is from about 1 〇 5 Å A/cm to about 1 〇 7 A/cm 2 and the pulse duration ranges from about 100 ns. Ns 2 is like the first rain technique in which each layer is flat (four) and has the same as the other layers, and Fig. 1 shows that the two hard magnets are much larger than the ferromagnetic freedom. This enables the use of low current densities for component programming.电流 φ The current density required for the direction of magnetization follows the equation: J=Jc〇[l-(KT/E)ln(r(/rp)], where e = MsVHk/2

Jc〇, K (Bozeman constant) and Γ〇 are constant, pulse duration jin temperature ^ is called saturation magnetization (four) plus 丨 (10) 咖 职 if no kiss ^ ^ component valley product) and Hk (anisotropy field ( Anis〇tr〇pjc fleid)) is a variable parameter. H For two large hard magnets, Hk and V are high. The two hard magnets of μιη visibility require a current density greater than 1〇7 A/cm2 to change the magnetization direction. Conversely, smaller ferromagnetic free structures have relatively low Hk and V. The required current density is about 1 〇 5 or 1 〇 6 A/cm 2 . Therefore, the proportional large volume of the two hard magnets makes the component more stable. At the same time, the smaller ferromagnetic free layer allows the use of a lower current density, thereby facilitating the magnetic stabilization of the component. Figure 2 shows a detailed cross section of an embodiment of the invention as connected to a bit line 22 and 24 carrying a current pulse for performing MRAM writing in a MraM array. The first hard magnet 10 is connected along in Figure 2 The bit line 22 of the x-axis display. The first hard magnet 1〇 can be constructed of a high-coercive material, including a 3d transitional ferromagnetic material or alloy such as CoFe or Co, such as 8 1317125 P950101 21247twf.doc/0〇6

a hard magnetic material of SmCo, or a hybrid structure, for example, deposited on &

Co颂ercity (C〇erCivjty) ranges from about 1〇〇 〇e to about ιτ(ι〇,〇〇〇

Oe). Alternatively, the first hard magnet 10 may be constructed of exchange_bias coupled ferromagnetic material. This includes ferromagnetics for antiferromagnetic structures. The antiferromagnetic material may be an antiferromagnetic material such as FeMn, IrMn or ptMn, a synthetic antiferromagnetic structure such as CoFe/Rr/CoFe, or a combination of both. Regardless of the material used for the boxing, the first hard magnet 1〇 should have a total thickness in the range of about 10 nm to about 200 nm. In Fig. 2, the insulator layer 12 is shown above the center axis of the first hard magnet. This structure includes materials such as Al; 2〇3 or Mg〇, and has a thickness ranging from about 0.8 nm to about 4 nm. The insulator layer 12 separates the first hard magnetic body 10 from the ferromagnetic free layer 14. The ferromagnetic free layer 14 may be a single ferromagnetic layer such as CoFe, CoFeB, NiFeSiB or NiFe, or may be a multilayer structure such as CoFeB/Ru/CoFeB. The thickness of each layer ranges from about i nm to about 10 nm. The coercivity of the ferromagnetic free layer η is lower than the coercivity of the first-hard magnetic body 10, such as less than 50 Oe. The thin metal layer 18 is used to conduct electron spin messages from the second hard magnet 20 during writing and to prevent the ferromagnetic free layer 14 from being

Magnetic dissipation between a hard magnet 20 is achieved. The metal layer 18 composed of ru, ι, and: A u attack Ag should, for example, cover a topology having a thickness of less than about 3. The second hard magnet 20 may be constructed of a material similar to that of the first hard magnet 10. In a preferred embodiment, the first hard magnet 1 & 9 1317125 P950101 21247twf.doc/006

The exchange offset of IrMn/CoFeB/Ru/CoFeB is coupled to a multilayer, and the second hard magnet 2〇 is a ferromagnetic single layer having high coercivity such as c〇Fe. In all embodiments, the second hard magnet 20 must have a magnetization direction that is opposite to the magnetization direction of the first hard magnet 10. The second hard magnet 20 is coupled to the bit line 24 shown along the y-axis in FIG.

The remaining space between the first hard magnet 10 and the second hard magnet 2〇 and the thin metal layer 18 may be filled by a dielectric spacer. The liner thickness can range from about 50 nm to about 200 nm. In a preferred embodiment, the dielectric is si 〇 2 . 3-11 generally illustrate the process of fabricating an MRAM device in accordance with a preferred embodiment of the present invention. Referring to Figure 3, a first hard magnet 10, an insulator structure 12, and an edge magnetic free layer 14 are deposited. The CMP, termination layer 26 may be metallic or insulating c hard mask J 28 placed on top of the CMP stop layer %. In the preferred embodiment #, the right hard mask 28 and the later deposited dielectric liner (discussed below) package @SK) 2 and the CMP slurry is called, then the termination layer %纟_constituting the termination layer 26 The thickness should be approximately 10 nm. Preferably, the hard mask 28 A Si〇2 is used, and the thickness range is also about 30 mm to about 3 nm thick to the thickness of the 3G film. . In a preferred embodiment, the pattern is transformed, such as a _ shape, a mesh shape, or a circular shape. , engraved insulator structure 12, ferromagnetic free layer 14, = two 匕 and: more mask 28 to the patterned anti-money film can be -E) method _ more mask 28 and end of the 1317125 P950101 21247twf.doc / 006 A recipe having multiple steps can be used to etch the ferromagnetic free layer 14 and the insulator 12. Possible chemicals include ci2, bC13, NF3, CF4, CHF3, CO, hydrazine 2, Ar, and/or N2. In the preferred embodiment, RIE is used. Alternatively, a time mode or an end point detection method can be used to terminate on the first hard magnet 1〇. Referring to FIG. 5, the first hard magnetic body 1 is etched into a tapered profile. Purification with Cl2, BC13, NF3, CF4, CHF3, CO, 02, Ar and/or N2 can be used to govern the RIE formulation. However, c〇 and 〇2 can be reduced, and BCI3 and CHF3 can be increased. Time mode or endpoint detection methods can be used to terminate the etching process. In order to remove the polymer, 〇2 plasma removal and wet stripping by 匚265 (~1) can be used. Referring to Figure 6, a suitable solvent is used to reduce the size of the hard mask 28. In the preferred embodiment, the critical dimension of the hard mask 28 ranges from about 10 nm to about 60 nm after reduction. This is a decrease from a pre-shrmk size of less than about 15 〇 nm. If a SiN hard mask is used, the solvent can be hot phosphoric acid under time mode control. In a preferred embodiment, the hard = screen is si 〇 2 ' and the solvent can be a thin hf or buffer under time mode control. Referring to Figure 7, the insulator structure 12, the ferromagnetic free layer = and the CMP stop layer 26 are etched again. Consistent with the reduced hard mask 28. A recipe can be used. For the CMp termination layer 26, possible chemicals include CTM3, CH3F, C〇, 〇2, ΑΓ and domain N2. In the case of a better real & 歹, the ship is used in the case of a fine-tuned parameter. Possible enlightenment of the ferromagnetic free layer 14 and the insulator structure 12 13 1317125 P950101 21247twf.doc/006 The science includes Cl2, BC13, NF3, CF4, CHF3, CO, 02, Ar and/or N2. The time mode or end point detection method can be used to terminate on the first hard magnet 10. In the preferred embodiment, RIE is used in the case of fine tuning parameters. Referring to Figure 8, a thick dielectric liner 16 is deposited over the entire construction. In the preferred embodiment, the dielectric is Si〇2 which is formed by a method such as chemical vapor deposition (CVD) or plasma enhanced CVD. The successor is shown in Figure 9 using a dielectric construction cmp process to expose the CMP stop layer 26 without damaging the ferromagnetic free structure. In a preferred embodiment, the slurry is Ce 〇 2 such that the grinding selectivity is sufficiently high to terminate on the CMP stop layer 26. A number of dummy patterns (not shown in Figure 9) that are close to each other are needed to detect the progress of the grinding. After cmp, mm丨 is needed to remove the remains of the remains. Referring to W 10 ', the CMP termination layer 26 from FIG. 9 is removed by, for example, wet etching or dry etching. In the better case (4) by the coffee _. For the outline ^ metal layer 18, the product is above the structure. Applying a magnetic field during deposition of the second hard magnetic ΐ to induce the magnetization direction film 32 is similar to the first-patterned anti-money film 3〇 because it is column-shaped, such as a film, and the critical dimension ranges from about 5Gnm to about 3 or ® shape. The critical dimension of the first hard magnet 10 is then , ''m, and must be larger than the one shown in Fig. 11' to make a multi-step formulation to the second hard magnet such as 12 1317125 P950101 21247twf.doc/006 and the thin metal layer 18. Possible chemicals include cl2, BC13, NF3, CF4, CHF"3, CO, 〇2, Ar, and/or n2. In the preferred embodiment, RIE is used in the case of fine tuning parameters. A time mode or endpoint detection method can be used to terminate on the dielectric pad during excessive remnant. After etching, all of the polymer was removed using % plasma removal and wet stripping by EKC265. Figure 2 shows a completed memory element having a magnetization direction indicated in the first hard magnetic field 1 and the second hard magnetic body %. The opposite magnetization direction and the conforming shape of the two hard magnets 1 〇 and 2 使得 cause the magnetic flux to form a circular loop via the magnets 1 〇 and 20. This loop stabilizes the energy to satisfy Maxwell's second equation divB = 〇. This self-stabilizing alignment of the hard magnets 1〇 and 2〇 prevents adjacent components from being disturbed by magnetic flux. The present invention has been described above by way of a preferred embodiment, and is not intended to limit the invention, and any of the ordinary skill in the art to which the invention pertains may be made without departing from the spirit and scope of the invention. More dynamic and full, 'Therefore, the scope of protection of the present invention is subject to the definition of patent scope. BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiment of the present invention is better understood. The following embodiments are better understood. In order to achieve the explanation of the present invention, a preferred embodiment is shown in the drawings. However, it should be understood that the invention is not limited to the precise arrangements shown. 31 shows a cross section of the basic structure of an embodiment of the present invention. Figure 2 shows a more detailed cross section of an embodiment of the invention. 13 Ι 317125 〇 ι 21247 twf.d 〇 c / 006 Figures 3-11 generally illustrate the process of fabricating an MRAM device in accordance with a preferred embodiment of the present invention. Figure 12 shows a cross section of an embodiment of the invention. [Main component symbol description] 10: First hard magnet 12: Insulator layer 14: Ferromagnetic free layer 16: Dielectric pad 18: Thin metal layer 20: Second hard magnet 22, 24: Bit line 26: CMP termination Layer 28: Hard mask 30, 32: resist film 14

Claims (1)

1317125 X. Patent application scope: 1. A nano magnetic component comprising: (a) a first hard magnet having a first magnetization direction and having a central axis;;.. (b) - second a hard magnet separated from the first hard magnetic body by a dielectric gasket having a second magnetization direction opposite to the first magnetization direction of the first hard magnet and having a central axis such that when the first hard magnet is aligned with the second hard magnet, a closed magnetic flux loop is formed via the first and second hard magnets; and (c) a ferromagnetic free layer having a central axis such that a spin torque transfer current is transmitted along the central axis of the first hard magnet, the second hard magnet, and the ferromagnetic free layer, and affects the ferromagnetic free layer a magnetization direction, wherein the second hard magnetic body has a shape conformed to a top and a side of the first hard magnetic body to surround a top end and a side end of the ferromagnetic free layer. 2. The nano magnetic element according to claim 1, wherein the ferromagnetic free layer has a coercivity of less than 50 〇e. ' 3. If you apply for a patent range! The nano magnetic element according to the item, wherein the ferromagnetic free layer is C〇Fe or CoFeB. , wherein 'd, wood magnetic components, one of which is a ferromagnetic 15 13 l7l25 98-8-17 6. The nano magnetic component described in claim 1 of the patent scope, further comprising (d) - insulator a layer between the first hard magnetic body and the ferromagnetic freely wide. 7. The nano magnetic element according to claim 6 of the patent application, wherein the jinda 纟ba body is widely AI2O3 or Mg〇. 8. The nano magnetic element according to claim 6, further comprising: #(8)-thin metal layer contacting the ferromagnetic free layer and the first zircoid. ^A nano magnetic element as described in claim 8 wherein the metal layer is Ru or Ir. 10. For the nano magnetic component described in the scope of claim 8 of the patent application, Li Zhonghu said that all parts of the thin metal layer of the layer are separated from the hard magnetic axis. ^ Γ ' A device comprising: each of the plurality of nano magnetic elements: the nano magnetic element comprises: a shaft (a) - a / hard magnet having a - 'magnetization direction and having a center (b) - a two hard magnet, the # is separated from the body, the second hard magnet has a 盥 沭Μ 玫 玫 更 更 更 更 更 更 更 更 一 一 第二 第二 第二 第二 第二 第二 第二 第二 第二 第二 第二 第二 第二 第二 第二 第二 第二 第二 第二 第二 第二_: hard paste I; medium::: and the second hard magnetic body to form a closed magnetic flux circuit 1 and 16 1317125 98-8-17 (c) a ferromagnetic free layer 'which has a central axis' a spin torque transfer current is transmitted along the central axes of the first and second hard magnets and the ferromagnetic free layer and affects a magnetization direction of the ferromagnetic free layer, wherein the a hard magnet having a shape conforming to a top and a side wall of the first hard magnet to surround the ferromagnetic self From the top and side ends of the layer, and each nano magnetic element is connected to a wafer to form an array for use in a magnetic random access memory. 12. Preparing a device for use in a nanomagnetic element The method includes a first hard magnet, a pillar, a thin metal layer deposited later, and a second hard magnet deposited later, the first hard magnet having a first magnetization direction and a meandering shape. The pillar includes an insulator layer, a ferromagnetic free layer, a CMP stop layer, and a hard mask, the second hard magnet having a second magnetization opposite to the first magnetization direction of the first hard magnet Direction, the method comprising: (a) reducing the hard mask; (b) etching the CMP stop layer, the ferromagnetic free layer, and the pillar of the insulator layer to form the hard mask And (c) etching the second hard magnetic body and the thin metal layer into a column shape such that the pattern is aligned with the first hard magnetic shape. 13. As described in claim 12 Method of preparing a device for use in a nanomagnetic element Wherein step (a) further comprises reducing the size of the hard mask from less than 150 nm to a hard mask size of 10 nm to 60 nm. 14. Preparation as described in claim 12 for Neil magnetic 17 * 1317125 98-8-17 The method of step _, wherein the step (C) comprises etching the second hard magnetic x to make the second hard magnetic element larger than / the first hard magnetic size. A method of preparing a device for use in a nanomagnetic element according to claim 12, wherein the step (including etching the second hard magnetic body such that the second hard magnetic material has a size of 50 nm to 300 nm). 16. The method of preparing a device for use in a nanomagnetic element according to claim 12, wherein the column shape is one of an elliptical shape, an eye shape, and a circular shape. 18 1317125 Hard magnet has a shape conforming with top and sidewalls of the first hard magnetic to enclose top and lateral sides of the ferromagnetic free layer. A spin-torque transfer current passes along the central Axis of the first and second hard magnets and the ferromagnetic free layer, and affects the magnetization direction of the ferromagnetic free layer. 7. The designated representative figure: (1) The representative representative figure of the case is: Figure (2). (b) The symbol of the representative figure is briefly described: 10: first hard magnet 12: insulator layer 14: ferromagnetic free layer 16: dielectric liner 18: thin metal layer 20: second hard magnet 22, 24: bit Yuan line = If there is a chemical formula in this case, please reveal the most money