Multilayer magnetic metal film with perpendicular magnetic anisotropy and method

Abstract

In the multilayer magnetic metal film, a substrate is a thermally oxidized monocrystalline silicon wafer, a buffer layer is laminated on the substrate, the buffer layer is a Ti / Pt, Ta / Pt or Ru / Pt, Ti, Ta or Ru layer, the thickness of the buffer layer is 2-4 nm, a [Co / Pt] n layer is laminated on the buffer layer, the thickness of a Co layer is 0.8-1.8 nm, the thickness of a Pt layer is 0.7-1.5 nm, and n is 2-5. The magnetic anisotropy of the thin film can be obviously regulated and controlled by regulating and controlling the thickness of the buffer layer, the thickness of the Co layer, the thickness of the Pt layer and the cycle number n, and the multi-layer magnetic metal thin film has good perpendicular magnetic anisotropy.

Description

Technical Field

[0001] The present invention relates to the field of memory technology, in particular to a multi-layer magnetic metal film with perpendicular magnetic anisotropy and a method thereof. Background Art

[0002] [Co / Pt] with perpendicular magnetic anisotropy n Multilayer films show extremely important application prospects in the fields of magnetic memory, magnetic sensors and spin electronics. Thanks to its high perpendicular magnetic anisotropy, [Co / Pt] n Multilayer films are used as the core material of perpendicular magnetic recording technology in ultra-high density magnetic recording media, which greatly improves the information storage density. In MRAM, [Co / Pt] with perpendicular magnetic anisotropy n Multilayer films can reduce device power consumption and improve storage reliability due to their low critical current density and high thermal stability factor. n Multilayer films and the regulation of their perpendicular magnetic anisotropy have very important academic and practical value.

[0003] In thin film preparation, film uniformity and thickness accuracy are critical to the performance of the film. [Co / Pt] n The magnetism of the multilayer film is thickness-dependent and closely related to the thickness of the Co layer. Increasing the thickness of Co can enhance the perpendicular magnetic anisotropy of the film, but an excessively thick Co layer will increase the demagnetization energy and thus reduce the perpendicular magnetic anisotropy. Therefore, the optimal value is only within a certain range. The buffer layer can also effectively regulate the magnetic anisotropy. Changing different buffer layers can significantly affect the coercive force and saturation magnetization of the multilayer film. Therefore, how to prepare and regulate [Co / Pt] with excellent perpendicular magnetic anisotropy is a key issue. n Multilayer films are of extraordinary significance for the development of spin electronics and its related devices.

[0004] The information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0005] In view of the shortcomings or defects of the above-mentioned prior art, a multilayer magnetic metal film and method with perpendicular magnetic anisotropy are provided, which significantly improve the uniformity and thickness accuracy of the film layer, effectively regulate the magnetic anisotropy, optimize the interface structure and quality, and avoid the annealing temperature causing the film to recrystallize, thereby reducing the interface quality and causing the degradation of the perpendicular magnetic anisotropy.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] A multilayer magnetic metal film having perpendicular magnetic anisotropy comprises: The substrate is a thermally oxidized single crystal silicon wafer, A buffer layer is stacked on the substrate, wherein the buffer layer is Ti / Pt, Ta / Pt or Ru / Pt, wherein the Ti, Ta or Ru layer has a thickness of 2-4 nm, [Co / Pt] n layer, which is stacked on the buffer layer, wherein the Co layer has a thickness of 0.8-1.8 nm, the Pt layer has a thickness of 0.7-1.5 nm, and n is 2-5.

[0008] In the multilayer magnetic metal film with perpendicular magnetic anisotropy, the substrate is Si / SiO 2 , oxide layer SiO 2 The thickness is 300 nm.

[0009] In the multilayer magnetic metal film with perpendicular magnetic anisotropy, the buffer layer is Ti / Pt, Ta / Pt or Ru / Pt, wherein the thickness of Pt is 1-3 nm.

[0010] In the multilayer magnetic metal film with perpendicular magnetic anisotropy, the substrate is Si / SiO 2 , relatively, the [Co / Pt] n The Pt layer in the layer is located on the top layer of the multi-layer magnetic metal film.

[0011] A method for preparing a multilayer magnetic metal film having perpendicular magnetic anisotropy comprises: Buffer layer, [Co / Pt] n The sputtering temperature of the multilayer film is room temperature, wherein the buffer layer, the Co layer and the Pt layer are all completed by DC sputtering; After coating, heat treatment is performed to improve the perpendicular magnetic anisotropy. The vacuum degree of annealing is less than 1×10 -5 Pa, annealing temperature is 250-320 ℃, annealing time is 20-90 min, and finally naturally cools to room temperature.

[0012] In the preparation method, a buffer layer, [Co / Pt] n The vacuum degree of the magnetron coating chamber for sputtering of multilayer films is less than 5×10 -6 Pa.

[0013] In the preparation method, the sputtering power of the magnetron coating chamber is 10-35 W, the sputtering gas is Ar gas, the sputtering gas flow rate is 10-30 sccm, and the vacuum degree of the chamber in the magnetron coating chamber is less than 1×10 -4 Pa.

[0014] In the preparation method, the purity of the sputtering gas Ar gas is greater than 99.99%.

[0015] In the preparation method, each metal film is pre-sputtered for 200 seconds before deposition to clean the target material, and the purity of the target material is greater than 99.9%.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention can control the magnetic anisotropy of the film by regulating the thickness of the buffer layer, the Co layer, the Pt layer and the number of periods n. Since Pt itself is not easily oxidized, the multilayer film does not need to be covered with an additional protective layer on the top. As the material of the buffer layer, its thickness change has little effect on the magnetism, and the type of material has a more obvious effect on the sample. The Pt layer and the Ru, Ti and Ta layers have good magnetism within the thickness variation range. After the preparation is completed, the annealing process is performed to improve the perpendicular magnetic anisotropy of the material and optimize the interface structure and quality, avoiding the interlayer diffusion of atoms in the film caused by the annealing temperature being too high, thereby reducing the interface quality and causing the degradation of the perpendicular magnetic anisotropy. The film structure has good perpendicular magnetic anisotropy, and the preparation process is simple and easy to control. The prepared [Co / Pt] n The multilayer film has good perpendicular magnetic anisotropy. In the present invention, the interface effect between Co and Pt causes the multilayer film to have good perpendicular magnetic anisotropy. Therefore, the present invention uses a design of alternating growth of Co and Pt.

[0017] The above description is only an overview of the technical solution of the present invention. In order to make the technical means of the present invention clearer and to achieve the extent that those skilled in the art can implement it according to the contents of the specification, and in order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are exemplified below. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0019] In the attached picture: Figure 1 The Si / SiO prepared by the present invention 2 (300) / buffer layer / [Co / Pt]n Schematic diagram of the cross-sectional structure of a multilayer magnetic metal film with perpendicular magnetic anisotropy; from bottom to top: substrate, buffer layer and [Co / Pt] n Multilayer film; Figure 2 The Si / SiO prepared in Example 1 of the present invention changes the number of multilayer film periods n. 2 (300) / Ti(2.5) / Pt(2) / [Co(1.4) / Pt(0.7)] 5 Hysteresis loop of multilayer magnetic metal film with perpendicular magnetic anisotropy of the sample; the number of cycles n corresponds to 2-5; Figure 3 The present invention is to change the Si / SiO prepared in Example 1 with the number of multilayer film periods n 2 (300) / Ti(2.5) / Pt(2) / [Co(1.4) / Pt(0.7)] 5 Hysteresis loop of multilayer magnetic metal film with perpendicular magnetic anisotropy after annealing at 300 °C for 60 min; the number of cycles n corresponds to 2-5; Figure 4 The Si / SiO with a changed Co thickness prepared in Example 2 is 2 (300) / Ti(2.5) / Pt(2) / [Co(t Co ) / Pt(0.7)] 5 Hysteresis loop of the multilayer magnetic metal film with perpendicular magnetic anisotropy of the sample, where t Co refers to the Co layer thickness, changing the Co thickness to 0.8 nm, 1.0 nm, 1.4 nm, 1.6 nm, and 1.8 nm; Figure 5 The Si / SiO with changed Pt thickness prepared in Example 3 is 2 (300) / Ti(2.5) / Pt(2) / [Co(1.4) / Pt(t Pt )] 5 Hysteresis loop of the multilayer magnetic metal film with perpendicular magnetic anisotropy of the sample, where t Pt refers to the thickness of the Pt layer, and the thickness of Pt was changed to 0.7 nm, 1.0 nm, and 1.5 nm; Figure 6 The Si / SiO buffer layer prepared in Example 4 is modified according to the present invention. 2 (300) / buffer layer / [Co(1.4) / Pt(1.0)] 5 Magnetic hysteresis loops of multilayer magnetic metal films with perpendicular magnetic anisotropy of the samples, changing the type of buffer layer to Ti(2.5) / Pt(2) and Ru(3) / Pt(2).

[0020] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0022] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0023] To facilitate understanding of the embodiments of the present invention, several specific embodiments will be further explained below with reference to the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0024] For a better understanding, Figures 1 to 6 As shown, a multilayer magnetic metal film having perpendicular magnetic anisotropy comprises: The substrate is a thermally oxidized single crystal silicon wafer, A buffer layer is stacked on the substrate, wherein the buffer layer is Ti / Pt, Ta / Pt or Ru / Pt, wherein the Ti, Ta or Ru layer has a thickness of 2-4 nm, [Co / Pt] n A layer is stacked on the buffer layer, wherein the Co layer has a thickness of 0.8-1.8 nm, the Pt layer has a thickness of 0.7-1.5 nm, n is 2-5, and the Co and Pt layers are alternated.

[0025] In a preferred embodiment of the multilayer magnetic metal film with perpendicular magnetic anisotropy, the substrate is Si / SiO 2 , oxide layer SiO 2 The thickness is 300 nm.

[0026] In a preferred embodiment of the multilayer magnetic metal film with perpendicular magnetic anisotropy, the buffer layer is Ti / Pt, Ta / Pt or Ru / Pt, wherein the thickness of Pt is 1-3 nm.

[0027] In a preferred embodiment of the multilayer magnetic metal film with perpendicular magnetic anisotropy, the substrate is Si / SiO 2 , relatively, the [Co / Pt] n The Pt layer in the layer is located on the top of the multi-layer magnetic metal film. In addition, the second layer of the buffer layer is a Pt layer, so [Co / Pt] n In the layer, no matter the period number n is 2-5, [Co / Pt] n The layer is always Co as the first layer so that the Co layer forms a Co / Pt interface with the second layer of the buffer layer, namely the Pt layer.

[0028] A method for preparing a multilayer magnetic metal film having perpendicular magnetic anisotropy comprises: Buffer layer, [Co / Pt] n The sputtering temperature of the multilayer film is room temperature, wherein the buffer layer, the Co layer and the Pt layer are all completed by DC sputtering; After coating, heat treatment is performed to improve the perpendicular magnetic anisotropy. The vacuum degree of annealing is less than 1×10 -5 Pa, annealing temperature is 250-320 ℃, annealing time is 20-90 min, and finally naturally cools to room temperature.

[0029] In a preferred embodiment of the preparation method, a buffer layer, [Co / Pt] n The vacuum degree of the magnetron coating chamber for sputtering of multilayer films is less than 5×10 -6 Pa.

[0030] In a preferred embodiment of the preparation method, the sputtering power of the magnetron coating chamber is 10-35 W, the sputtering gas is Ar gas, the sputtering gas flow rate is 10-30 sccm, and the vacuum degree of the chamber in the magnetron coating chamber is less than 1×10 -4 Pa.

[0031] In a preferred embodiment of the preparation method, the purity of the sputtering gas Ar gas is greater than 99.99%.

[0032] In a preferred embodiment of the preparation method, each metal film is pre-sputtered for 200 seconds before deposition to clean the target material, and the purity of the target material is greater than 99.9%.

[0033] In one embodiment, the film structure is substrate / buffer layer / [Co / Pt] nThe preparation method is to use magnetron sputtering coating method to sequentially carry out buffer layer / [Co / Pt] on the substrate n Sputtering of multilayer films. Each layer is completed by DC sputtering. The coating process is simple. The prepared multilayer film has good perpendicular magnetic anisotropy and the magnetism is easy to control.

[0034] [Example 1] The multilayer film is prepared on the thermally oxidized single crystal silicon wafer using magnetron sputtering coating equipment at room temperature. The film structure is specifically Si / SiO 2 / Ti(2.5) / Pt(2) / [Co(1.4) / Pt(0.7)] n . Prepare samples with different period numbers n. SiO 2 The thickness of the oxide layer is 300nm. The vacuum degree of the film chamber of the magnetron sputtering equipment is 3×10 -6 Pa, the vacuum degree of the sample delivery chamber is 5×10 -5 Pa. Each layer is sputtered by DC magnetron sputtering, the sputtering power is 10 W, and the flow rate of sputtering gas Ar gas is controlled as follows: Ti and Pt are 20 sccm, Co is 10 sccm. The purity of Ar gas is greater than 99.99%. The purity of each target material is higher than 99.9%. The hysteresis loop of the multilayer magnetic film material prepared in this embodiment in the prepared state is as follows: Figure 2 As shown, the sample exhibits obvious perpendicular magnetic anisotropy. At the same time, it can be seen that the saturation magnetization and coercive force of the sample increase with the increase of the number of cycles.

[0035] The sample was then annealed in the coating chamber at 300°C for 60 min. The vacuum degree of the chamber was less than 1×10 -5 Pa. The hysteresis loop of the sample after annealing is as follows Figure 3 As shown, through the annealing process, it can be seen that the saturation magnetization and coercive force of the sample are improved, and the squareness of the hysteresis loop is also optimized.

[0036] [Example 2] The multilayer film was prepared on a thermally oxidized single crystal silicon wafer using a magnetron sputtering coating device at room temperature. Compared with Example 1, this example maintained the same number of cycles, buffer layer and Pt layer thicknesses, and changed the Co layer thickness to 0.8 nm, 1.0 nm, 1.4 nm, 1.6 nm and 1.8 nm. In addition, the parameters for preparing the film did not change. The film structure is specifically Si / SiO 2 / Ti(2.5) / Pt(2) / [Co(t Co ) / Pt(0.7)] 5 The hysteresis loop of the multilayer magnetic film material prepared in this embodiment in the prepared state is as follows: Figure 4 As shown, the sample exhibits obvious perpendicular magnetic anisotropy. At the same time, it can be seen that the saturation magnetization and coercive force of the sample increase with the increase of the Co layer thickness.

[0037] [Example 3] The multilayer film was prepared on a thermally oxidized single crystal silicon wafer using a magnetron sputtering coating device at room temperature. Compared with Example 1, this example maintained the same number of cycles, buffer layer and Co layer thickness, and changed the Pt layer thickness to 0.7 nm, 1.0 nm and 1.5 nm. In addition, the parameters for preparing the film did not change. The film structure is specifically Si / SiO 2 / Ti(2.5) / Pt(2) / [Co(1.4) / Pt(t Pt )] 5 The hysteresis loop of the multilayer magnetic film material prepared in this embodiment in the prepared state is as follows: Figure 5 As shown, the sample exhibits obvious perpendicular magnetic anisotropy. At the same time, it can be seen that the coercivity of the sample has no obvious change, and the saturation magnetization has a tendency to increase with the increase of Pt thickness, but the saturation magnetization when the Pt thickness is 1.5 nm is smaller than that of 1.0 nm. This shows that the Pt thickness has only a regulatory effect on the magnetic properties of the multilayer film in terms of saturation magnetization, and cannot effectively regulate the coercivity of the multilayer film.

[0038] [Example 4] The multilayer film was prepared on a thermally oxidized single crystal silicon wafer using a magnetron sputtering coating device at room temperature. Compared with Example 1, this example maintained the same number of cycles, Co layer thickness and Pt layer thickness, and changed the buffer layer to Ti / Pt and Ru / Pt. In addition, the parameters for preparing the film did not change. The film structure is specifically Si / SiO 2 / Buffer layer / [Co(1.4) / Pt(1.0)] 5 The hysteresis loop of the multilayer magnetic film material prepared in this embodiment in the prepared state is as follows: Figure 6 As shown in the figure, the sample exhibits obvious perpendicular magnetic anisotropy. It can be seen that different buffer layers can effectively regulate the magnetic properties of the multilayer film.

[0039] The basic principles of the present application are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present application. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation, and the above details do not limit the present application to being implemented by adopting the above specific details.

[0040] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A multilayer magnetic metal film having perpendicular magnetic anisotropy, characterized in that: These include, The substrate is a thermally oxidized single crystal silicon wafer, A buffer layer is stacked on the substrate, wherein the buffer layer is Ti / Pt, Ta / Pt or Ru / Pt, wherein the Ti, Ta or Ru layer has a thickness of 2-4 nm, [Co / Pt] n layer, which is stacked on the buffer layer, wherein the Co layer has a thickness of 0.8-1.8 nm, the Pt layer has a thickness of 0.7-1.5 nm, and n is 2-5.

2. The multilayer magnetic metal film with perpendicular magnetic anisotropy according to claim 1, characterized in that: Preferably, the substrate is Si / SiO2, and the thickness of the oxide layer SiO2 is 300 nm.

3. The multilayer magnetic metal film with perpendicular magnetic anisotropy according to claim 1, characterized in that: The buffer layer is Ti / Pt, Ta / Pt or Ru / Pt, and the thickness of Pt is 1-3 nm.

4. The multilayer magnetic metal film with perpendicular magnetic anisotropy according to claim 1, characterized in that: The [Co / Pt] n The Pt layer in the layer is located on the top layer of the multi-layer magnetic metal film.

5. The method for preparing a multilayer magnetic metal film having perpendicular magnetic anisotropy according to any one of claims 1 to 4, characterized in that: These include, Buffer layer, [Co / Pt] n The sputtering temperature of the multilayer film is room temperature, wherein the buffer layer, the Co layer and the Pt layer are all completed by DC sputtering; After coating, heat treatment is performed to improve the perpendicular magnetic anisotropy. The vacuum degree of annealing is less than 1×10 -5 Pa, annealing temperature is 250-320 ℃, annealing time is 20-90 min, and finally naturally cools to room temperature.

6. The preparation method according to claim 5, characterized in that: In the magnetron coating chamber, buffer layer, [Co / Pt] n The vacuum degree of the magnetron coating chamber for sputtering of multilayer films is less than 5×10 -6 Pa.

7. The preparation method according to claim 6, characterized in that The sputtering power of the magnetron coating chamber is 10-35 W, the sputtering gas is Ar gas, the sputtering gas flow rate is 10-30 sccm, and the vacuum degree of the chamber in the magnetron coating chamber is less than 1×10 -4 Pa.

8. The preparation method according to claim 7, characterized in that: The purity of sputtering gas Ar is greater than 99.99%.

9. The preparation method according to claim 5, characterized in that: Each layer of metal film is pre-sputtered for 200 seconds before deposition to clean the target material. The purity of the target material is greater than 99.9%.

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