CN101710525B - Ultra-high sensitive magneto-resistance film material and preparation method thereof - Google Patents

Abstract

An ultrahigh sensitive magnetoresistance thin film material and a preparation method thereof relate to magnetic thin film materials. The film material structure designed in the present invention is: buffer layer/MgO/NiFe/MgO/protective layer; and then annealed at high temperature in a magnetic field. The structural material has high magnetic field sensitivity, and processing it into a magnetic sensing element also has high magnetic field sensitivity. The main advantage of this method is that the material structure design is simple, and the magnetic field sensitivity is significantly improved, which is basically equivalent to the magnetic field sensitivity of some tunneling magnetoresistance (TMR) thin film materials and corresponding components; at the same time, it overcomes the problem when the NiFe layer is thin in the previous material system process. The "magnetic dead layer" caused by the solid phase reaction at the thin film interface brought about by processing materials or devices at a certain temperature, therefore, this material can be used to make highly sensitive magnetoresistance sensing components.

Description

A kind of ultrahigh sensitivity magnetoresistance film material and preparation method thereof

technical field

The invention relates to a magnetic thin film material, in particular to a highly sensitive magnetoresistance thin film material and a preparation method thereof.

Background technique

Anisotropic magnetoresistance (AMR) permalloy thin film material (NiFe) can be used to make application devices such as computer hard disk read head, magnetic random access memory and various magnetic sensors, and is widely used in automation technology, household appliances, navigation systems, mobile In the fields of communications, large-capacity storage and computers, especially in geomagnetic measurements, AMR thin film materials have better direction sensitivity than giant magnetoresistance (GMR) and tunnel magnetoresistance (TMR) thin film materials, and anisotropic magnetic There is a quantitative relationship between resistivity and angle: ρ(θ)=ρ _⊥ +Δρcos ² θ, so this material has a broad application prospect in geomagnetic navigation and other fields. In addition, the resistance value of the AMR device is much smaller than that of the TMR device, which is very beneficial to the use of the device. In order to realize the high sensitivity and low noise characteristics of advanced magnetic sensors and other devices, it is required that the NiFe film must be made very thin, the coercive force is small, the AMR value is as large as possible, and the magnetic field sensitivity is as high as possible. In actual device fabrication, the main structure of thin film materials is usually Ta/NiFe/Ta. In order to further reduce the demagnetization field, the thickness of NiFe is usually only a few to a dozen nanometers; in addition, the process may also need to process the material at a certain temperature or At this time, the "magnetic dead layer" caused by the solid phase reaction at the thin film interface cannot be ignored. At the same time, the shunting effect of the seed layer and the protective layer is more obvious, and it is difficult for the thin film material to maintain a good magnetoresistance change rate (ΔR/R) and magnetic field sensitivity (S _v ). In order to ensure that the ultra-thin NiFe film has a larger magnetoresistance change rate and higher magnetic field sensitivity to meet the needs of magnetic sensors, etc., in the literature WYLee, M.Toney, P.Tameerug, E.Allen and D.Mauri , J.Appl.Phys.87, 6992 (2000) proposed to use (Ni _0.81 Fe _0.19 ) _1-x Cr _x or Ni _1-x Cr _x as the seed layer to prepare the Ni _0.81 Fe _0.19 thin film, and its AMR value is higher than The AMR value of the Ni _0.81 Fe _0.19 film with Ta as the seed layer has been significantly improved. For example, the AMR value of the 12nm thick NiFe film has reached 3.2%, but for NiFe with only a few to a dozen nanometers, especially in the After annealing, it is difficult to ensure that its magnetic field sensitivity is improved. In the literature H.Funaki, S.Okamoto, O.Kitakami, and Y.Shimada, Jpn.J.Appl.Phys., Part 233, L1304 (1994), it is proposed that the use of annealing can significantly improve the ΔR/ R value, such as 20nm thick Permalloy thin film, after annealing at 400°C, the ΔR/R value can reach 3.5%, but this is obtained without a buffer layer and a protective layer. When making an AMR device, use When the buffer layer and protective layer are used, and the thickness of the film is only a few to a dozen nanometers, it is difficult to maintain good indicators of ΔR/R and S _v after annealing. In the literature Lei Ding, Jiao Teng, Qian Zhan, Chun Feng, Ming-hua Li, Gang Han, Li-jin Wang, Guang-hua Yu, and Shu-yun Wang, Appl.Phys.Lett.94, 162506 (2009) A new structure Ta/Al ₂ O ₃ /NiFe/Al ₂ O ₃ /Ta film was designed. After annealing at 380℃, Ta 5nm/Al ₂ O ₃ 1.5nm/NiFe 10nm/Al ₂ O ₃ 1.5nm/ The change rate of Ta 5nm magnetoresistance is 250% higher than that of Ta 5nm/NiFe10nm/Ta 5nm, and the magnetic field sensitivity is increased by 150%, reaching a magnetic field sensitivity of 1.3%/Oe, but its magnetic field sensitivity is compared with tunneling magnetoresistance (TMR) thin film materials There is still a large gap, one of the main reasons is that Al ₂ O ₃ is very difficult to crystallize, and other easy-to-crystallize oxides must be found to maximize the scattering of spin electrons to improve ΔR/R and S _v .

Contents of the invention

The object of the present invention is to propose a magnetoresistance thin film material structure to meet the needs of ultrahigh magnetic field sensitive magnetoresistance thin film materials.

In order to realize the object of the present invention, an ultra-high sensitive magnetoresistance thin film material is proposed, and the structure of the magnetoresistance thin film material is: buffer layer/MgO/NiFe/MgO/protective layer.

The MgO layer is a non-magnetic nano oxide layer in a crystalline state through high temperature annealing.

The buffer layer can be Ta, NiFeCr or NiCr.

The protection layer may be Ta or Au.

MgO

Ni_xFe_100-x

MgO

保护层

其中70＜x＜90。The thickness of each layer of the magnetoresistance thin film material is specifically: buffer layer

MgO

Ni _x Fe _100-x

MgO

The protective layer

where 70<x<90.

The present invention also proposes a preparation method for preparing the above-mentioned ultra-high sensitive magnetoresistance film material, and the specific preparation steps are:

)/MgO(

)/Ni_xFe_100-x(

)/MgO(

)/保护层(

)，其70＜x＜90。The magnetoelectric thin film material is prepared in a magnetron sputtering apparatus, and the buffer layer (

)/MgO(

)/Ni _x Fe _100-x (

)/MgO(

)/The protective layer(

), its 70<x<90.

The background vacuum of the sputtering chamber is 1×10 ^-5 ~ 6×10 ^-5 Pa, the argon pressure during sputtering is 0.2 ~ 0.7Pa, the purity of argon is 99.99%, the substrate is cooled by circulating water, parallel to the substrate A magnetic field of 150-250Oe is added to the sheet direction to induce an easy magnetization direction;

Then, the magnetoresistance thin film material is subjected to vacuum magnetic field heat treatment in a vacuum annealing furnace, the background vacuum degree of the annealing furnace is 2×10 ^-5 ~ 8×10 ^-5 Pa, the annealing temperature is 400 ~ 600°C, and the annealing time is 10 minutes ~ 6 hours, annealing field 500 ~ 1000Oe.

The advantage of the present invention is that: due to the non-magnetic oxide layer-MgO layer with a nanometer thickness in the design of the material structure, it not only hinders the diffusion between the buffer layer and the NiFe layer, but also improves the way of spin electron scattering, and is obtained after heat treatment in a vacuum magnetic field. A non-magnetic oxide layer with a crystalline structure and a good NiFe magnetic domain structure are obtained, thereby improving the magnetic field sensitivity of the thin film material. The main advantages are not only simple material structure design, convenient manufacture, and obvious improvement in magnetic field sensitivity, which is basically equivalent to the magnetic field sensitivity of some tunneling magnetoresistance (TMR) thin film materials; The magnetic field sensitivity of the element is equivalent (but its element design is simpler than that of the TMR element); at the same time, it overcomes the problem of solid phase reaction at the thin film interface caused by processing materials or devices at a certain temperature when the NiFe layer is thin in the previous material system process. The resulting "magnetic dead layer" provides a practical material for making computer hard disk read heads, magnetic random access memories, and various magnetic sensors.

Description of drawings

)/MgO(

)/Ni₈₁Fe₁₉(

)/MgO(

)/Ta(

薄膜磁电阻输出曲线，纵坐标表示磁电阻变化率，横坐标表示外加测量磁场；Figure 1 is Ta(

)/MgO(

)/Ni ₈₁ Fe ₁₉ (

)/MgO(

)/Ta(

Thin film magnetoresistance output curve, the ordinate indicates the rate of change of magnetoresistance, and the abscissa indicates the applied magnetic field;

Fig. 2 is a structural schematic diagram of a magnetoresistive sensing element;

)/Ni₈₀Fe₂₀()/(MgO

)/Au(

)薄膜按图2设计加工成宽为30微米的磁电阻传感元件电压信号输出曲线。Figure 3 is NiFeCr ( )/(MgO

)/Ni ₈₀ Fe ₂₀ ( )/(MgO

)/Au(

) film is designed and processed according to Fig. 2 into a voltage signal output curve of a magnetoresistive sensing element with a width of 30 microns.

Detailed ways

Example 1

)/MgO(

)/Ni₈₁Fe₁₉(

)/MgO(

)/Ta()。然后将薄膜材料进行真空磁场热处理，退火炉本底真空度为8×10^-5Pa，退火温度400℃，退火时间为0.5小时，退火场800Oe，制得薄膜。Magnetic thin films were prepared in a magnetron sputtering apparatus. Firstly, the glass substrate is ultrasonically cleaned with organic chemical solvent and deionized water, and then placed on the sample base of the sputtering chamber. The substrate is cooled with circulating water, and a magnetic field of 150 Oe is applied parallel to the direction of the substrate. The background vacuum of the sputtering chamber is 3×10 ^-5 Pa, and Ta (

)/MgO(

)/Ni ₈₁ Fe ₁₉ (

)/MgO(

)/Ta( ). Then the film material was subjected to vacuum magnetic field heat treatment, the background vacuum degree of the annealing furnace was 8×10 ^-5 Pa, the annealing temperature was 400° C., the annealing time was 0.5 hour, and the annealing field was 800 Oe to prepare the film.

Figure 1 is the magnetoresistance output curve of the thin film material measured by the conventional four-probe method, and its magnetic field sensitivity is up to 2.0% Oe, which is better than that of literature Lei Ding, Jiao Teng, Qian Zhan, Chun Feng, Ming-hua Li, Gang Han, Li-jin Wang, Guang-hua Yu, and Shu-yun Wang, Appl. Phys. Lett.94, 162506 (2009) have a much higher magnetic field sensitivity of NiFe under the same conditions. High-resolution electron microscopy shows that the MgO layer Crystallization is good.

Example 2

)/(MgO

)/Ni₈₀Fe₂₀(

)/(MgO

)/Au(

)。然后将薄膜材料进行真空磁场热处理，退火炉本底真空度为4×10^-5Pa，退火温度500℃，退火时间为2小时，退火场900Oe，制得薄膜。用常规的四探针方法测的该薄膜材料的磁电阻输出曲线，其磁场灵敏度最大为2.3％/Oe。再通过一般的半导体加工工艺将薄膜材料加工成线宽为30微米的磁电阻传感元件；一般的半导体加工工艺是指：甩胶、曝光、显影、坚膜、刻蚀等。Magnetic thin films were prepared in a magnetron sputtering apparatus. Firstly, the single crystal Si(001) substrate is ultrasonically cleaned with organic chemical solvent and deionized water, and then placed on the sample base of the sputtering chamber. The substrate is cooled with circulating water, and a magnetic field of 250 Oe is applied parallel to the direction of the substrate. The background vacuum of the sputtering chamber is 4×10 ^-5 Pa, and NiFeCr (

)/(MgO

)/Ni ₈₀ Fe ₂₀ (

)/(MgO

)/Au(

). Then the film material was subjected to vacuum magnetic field heat treatment, the background vacuum degree of the annealing furnace was 4×10 ^-5 Pa, the annealing temperature was 500° C., the annealing time was 2 hours, and the annealing field was 900 Oe to prepare the film. The magnetoresistance output curve of the thin film material measured by the conventional four-probe method shows that the maximum magnetic field sensitivity is 2.3%/Oe. Then, the thin film material is processed into a magnetoresistive sensing element with a line width of 30 microns through the general semiconductor processing technology; the general semiconductor processing technology refers to: glue removal, exposure, development, film hardening, etching, etc.

Figure 2 is a schematic diagram of the structure of the magnetoresistive sensing element, and Figure 3 is the voltage signal output curve of the magnetoresistance sensing element. equivalent of a magnetoresistive (TMR) sensing element.

Claims (5)

1. a kind of ultrahigh sensitivity magnetoresistance film material, it is characterized in that, described magnetoresistance film material structure is: buffer layer/MgO/Ni _x Fe _100-x /MgO/protective layer, wherein The magnetoresistance thin film material is prepared in a magnetron sputtering apparatus, and the buffer layer/MgO/Ni _x Fe _100-x /MgO/protective layer is sequentially deposited on a cleaned glass substrate or a single crystal silicon substrate, 70 <x<90; The background vacuum degree of the sputtering chamber is 1×10 ^-5 ~ 6×10 ^-5 Pa, the argon pressure is 0.2 ~ 0.7 Pa during sputtering, the substrate is cooled by circulating water, and 150 ~ 250Oe magnetic field to induce an easy magnetization direction; The magnetoresistance thin film material is subjected to vacuum magnetic field heat treatment in a vacuum annealing furnace, the background vacuum degree of the annealing furnace is 2×10 ^-5 to 8×10 ^-5 Pa, the annealing temperature is 400-600°C, and the annealing time is 10 minutes ~ 6 hours, annealing field 500 ~ 1000Oe. 2. The ultra-high sensitive magnetoresistance thin film material as claimed in claim 1, wherein the purity of the argon gas is 99.99% during sputtering. 3. The ultrahigh sensitive magnetoresistance thin film material as claimed in claim 1, characterized in that, the buffer layer is Ta, NiFeCr or NiCr. 4. The ultrahigh sensitive magnetoresistance thin film material according to claim 1, characterized in that, the protective layer is Ta or Au. 5. The ultrahigh sensitive magnetoresistance thin film material as claimed in claims 1～4, is characterized in that, the thickness of each layer of described magnetoresistance thin film material is: buffer layer 30～

MgO 10～

Ni _x Fe _100-x 50～

MgO 10～

Protective layer 50～

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