Layer structure of MR sensor for laser annealing

Abstract

To provide a layer structure of an MR sensor for laser annealing. In an embodiment of the present invention, a magnetoresistive sensor layer structure for laser annealing is disclosed. The magnetoresistive sensor layer structure includes a substrate, a magnetoresistive sensing unit located on the substrate and including an antiferromagnetic pinning layer or a permanent magnet bias layer, an upper heat absorbing layer located above the magnetoresistive sensing unit and / or a lower heat absorbing layer located below the magnetoresistive sensing unit, where the product of the volume, specific heat, and density of the upper absorbing layer is greater than the product of the volume, specific heat, and density of the upper electrode layer, the product of the volume, specific heat, and density of the lower absorbing layer is greater than the product of the volume, specific heat, and density of the lower electrode layer, and when the writing temperature of the antiferromagnetic pinning layer or the permanent magnet bias layer is higher than the blocking temperature or Curie temperature corresponding thereto, the temperature of the lower electrode layer and the temperature of the upper electrode layer are lower than the melting point temperature corresponding thereto, respectively, the upper heat absorbing layer and / or the lower heat absorbing layer, a laser absorbing layer, and a laser transmitting layer. The embodiment of the present invention can solve the problem that the electrode layer is easily ablated.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to the technical field of magnetic sensors, and more particularly to layer structures of magnetoresistive sensors for laser annealing. [Background technology]

[0002] Magnetoresistive sensors, such as magnetic tunnel junction sensors, can use an antiferromagnetic layer as a pinning layer. In this case, a magnetic field annealing method is used to obtain a magnetic field-sensitive orientation of the magnetic tunnel junction above its blocking temperature. When a permanent magnetic bias layer is used in the magnetic tunnel junction to bias the reference or free layer, the magnetic field annealing is performed above its Curie temperature to obtain the magnetization orientation of the permanent magnetic material.

[0003] When laser annealing is used, the laser scans the magnetoresistive sensing unit array on the grain of the magnetoresistive sensor to obtain magnetoresistive sensing units with different sensitive orientations, thereby realizing the fabrication of a multi-axis magnetoresistive sensor on a single grain, which is of great importance for the design, fabrication, and use of magnetoresistive sensors.

[0004] However, in the multilayer structure of a magnetoresistive sensor, the entire structure of the lower electrode layer / stacked layer of the magnetic sensing unit / upper electrode layer is very thin, almost at the nanometer level. Furthermore, there is a gap between adjacent magnetic tunnel junctions, and this gap is electrically connected only through the upper electrode layer or the lower electrode layer. Under operation at a constant laser power and a constant scan speed, due to the different heat capacities of the materials in the magnetic tunnel junction and the gap, the upper electrode layer or the lower electrode layer in the gap may be heated above its melting point, causing ablation and blowing of the magnetoresistive sensor when the ferromagnetic pinning layer or permanent magnet bias layer in the magnetic tunnel junction is heated to the critical blocking temperature or above the Curie temperature. Summary of the Invention [Problem to be solved by the invention]

[0005] SUMMARY OF THE INVENTION An embodiment of the present invention provides a layer structure of a magnetoresistive sensor for laser annealing, so as to solve the problem that the existing layer structure of the magnetoresistive sensor is easily ablated during laser annealing. [Means for solving the problem]

[0006] An embodiment of the present invention is a layer structure of a magnetoresistive sensor for laser annealing, comprising: substrate, a magnetoresistive sensing unit located on a substrate, the magnetoresistive sensing unit comprising, in order from bottom to top, a seed layer, a bottom electrode layer, a stacking layer of a magnetic sensing unit, and a top electrode layer, the stacking layer of the magnetic sensing unit comprising at least an antiferromagnetic pinning layer or a permanent magnet bias layer; an upper heat absorption layer located above the magnetoresistive sensing unit and / or a lower heat absorption layer located below the magnetoresistive sensing unit, wherein a product of the volume, specific heat, and density of the upper heat absorption layer is greater than a product of the volume, specific heat, and density of the upper electrode layer, and a product of the volume, specific heat, and density of the lower heat absorption layer is greater than a product of the volume, specific heat, and density of the lower electrode layer, and when a writing temperature of the antiferromagnetic pinning layer or the permanent magnet bias layer is higher than a blocking temperature or a Curie temperature corresponding thereto, the temperatures of the lower electrode layer and the upper electrode layer are lower than their corresponding melting point temperatures; a laser absorption layer located above the magnetoresistive sensing unit; A laser transmission layer located above the laser absorption layer The present invention provides a layer structure of a magnetoresistive sensor, comprising:

[0007] In an embodiment of the present invention, a heat absorption layer is provided above or below the magnetoresistive sensing unit. The product of the volume, specific heat, and density of the upper heat absorption layer is greater than the product of the volume, specific heat, and density of its adjacent upper electrode layer, and the product of the volume, specific heat, and density of the lower heat absorption layer is greater than the product of the volume, specific heat, and density of its adjacent lower electrode layer. The heat absorption layer has a much higher specific heat than the magnetoresistive sensing unit, thereby maximizing the uniformity of the specific heat of the film layers, upper electrode layers, and lower electrode layers of the magnetoresistive sensing unit and reducing the difference in temperature rise caused by the difference in specific heat of the film layers, upper electrode layers, and lower electrode layers of the magnetoresistive sensing unit. In this case, when the writing temperature of the antiferromagnetic pinning layer / permanent magnet bias layer reaches its blocking temperature / Curie temperature, the temperature rises of the lower electrode layer and the upper electrode layer are close, and the temperatures of the lower electrode layer and the upper electrode layer are both lower than their corresponding melting points. Based on this, ablation of the layer structure of the magnetoresistive sensor during laser annealing can be avoided, thereby improving the stability of the layer structure of the magnetoresistive sensor and the efficiency of laser annealing.

[0008] In order to more clearly show the technical solutions in the embodiments of the present invention or the prior art, the drawings required for the illustration of the embodiments or the prior art are briefly introduced below. Obviously, the drawings described below are some specific embodiments of the present invention, but those skilled in the art can extend the drawings to other structures and drawings according to the basic concepts of the device structure, driving method and manufacturing method disclosed and promoted by various embodiments of the present invention, which will undoubtedly fall within the scope of the claims of the present invention. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a layer structure of a magnetoresistive sensor provided in an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram of a layer structure of another magnetoresistive sensor provided in an embodiment of the present invention. [Figure 3] FIG. 4 is a schematic diagram of a layer structure of a third magnetoresistive sensor provided in an embodiment of the present invention. [Figure 4] FIG. 2 is a topological diagram of the upper heat absorption layer of the layer structure of the magnetoresistive sensor. [Figure 5] Figure 4 shows a topological diagram of the upper heat absorption layer of the layer structure of the single-arm magnetoresistive sensor. [Figure 6] Figure 4 shows a topological diagram of the upper heat absorption layer of the layer structure of the push-pull multi-arm magnetoresistive sensor. [Figure 7] FIG. 10 is a topological diagram of the upper heat absorption layer of another magnetoresistive sensor layer structure. [Figure 8] Figure 7. Topological diagram of the upper heat absorption layer of the layer structure of the single-arm magnetoresistive sensor. [Figure 9] Figure 7 shows a topological diagram of the upper heat absorption layer of the layer structure of the push-pull multi-arm magnetoresistive sensor. [Figure 10] FIG. 10 is a topological diagram of the upper heat absorption layer of another magnetoresistive sensor layer structure. [Figure 11] Figure 10. Topological diagram of the upper heat absorption layer of the layer structure of the single-arm magnetoresistive sensor. [Figure 12] Figure 10 shows a topological diagram of the upper heat absorption layer of the layer structure of the push-pull multi-arm magnetoresistive sensor. [Figure 13] FIG. 10 is a topological diagram of the upper heat absorption layer of another magnetoresistive sensor layer structure. [Figure 14] Figure 13 is a topological diagram of the upper heat absorption layer of the layer structure of the single-arm magnetoresistive sensor. [Figure 15] Figure 14 is a topological diagram of the upper heat absorption layer of the layer structure of the push-pull multi-arm magnetoresistive sensor. DETAILED DESCRIPTION OF THE INVENTION

[0010] In order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be more clearly and completely described below through implementation with reference to the drawings of the embodiments of the present invention. It is clear that the described embodiments are only some embodiments, not all of the embodiments of the present invention. Based on the basic concepts disclosed and promoted by the embodiments of the present invention, all other embodiments obtained by those skilled in the art will fall within the protection scope of the present invention.

[0011] An embodiment of the present invention provides a layer structure of a magnetoresistive sensor for laser annealing, the layer structure of the magnetoresistive sensor including a substrate, a magnetoresistive sensing unit located on the substrate, the magnetoresistive sensing unit including, in order from bottom to top, a seed layer, a lower electrode layer, a stacking layer of a magnetic sensing unit, and an upper electrode layer, the stacking layer of the magnetic sensing unit including at least an antiferromagnetic pinning layer or a permanent magnet bias layer, and an upper heat absorption layer located above the magnetoresistive sensing unit and / or a lower heat absorption layer located below the magnetoresistive sensing unit, the product of the volume, specific heat, and density of the upper heat absorption layer being: the product of the volume, specific heat, and density of the lower electrode layer is greater than the product of the volume, specific heat, and density of the lower heat absorption layer, and the product of the volume, specific heat, and density of the lower electrode layer is greater than the product of the volume, specific heat, and density of the lower electrode layer; and when the writing temperature of the antiferromagnetic pinning layer or the permanent magnet bias layer is higher than their corresponding blocking temperature or Curie temperature, the temperatures of the lower electrode layer and the upper electrode layer are both lower than their corresponding melting points; the magnetoresistive sensing unit includes an upper heat absorption layer and / or a lower heat absorption layer; a laser absorption layer located above the magnetoresistive sensing unit; and a laser transmission layer located above the laser absorption layer.

[0012] In an embodiment of the present invention, a heat absorption layer is provided above or below the magnetoresistive sensing unit. The product of the volume, specific heat, and density of the upper heat absorption layer is greater than the product of the volume, specific heat, and density of its adjacent upper electrode layer, and the product of the volume, specific heat, and density of the lower heat absorption layer is greater than the product of the volume, specific heat, and density of its adjacent lower electrode layer. The heat absorption layer has a much higher specific heat than the magnetoresistive sensing unit, thereby maximizing the uniformity of the specific heat of the film layers, upper electrode layers, and lower electrode layers of the magnetoresistive sensing unit and reducing the difference in temperature rise caused by the difference in specific heat of the film layers, upper electrode layers, and lower electrode layers of the magnetoresistive sensing unit. In this case, when the writing temperature of the antiferromagnetic pinning layer / permanent magnet bias layer reaches its blocking temperature / Curie temperature, the temperature rises of the lower electrode layer and the upper electrode layer are close, and the temperatures of the lower electrode layer and the upper electrode layer are both lower than their corresponding melting points. Based on this, ablation of the layer structure of the magnetoresistive sensor during laser annealing can be avoided, thereby improving the stability of the layer structure of the magnetoresistive sensor and the efficiency of laser annealing.

[0013] The optional substrate has a passivation layer on its surface facing the magnetoresistive sensing unit, the thermal conductivity of the passivation layer being less than 1 / 10 of the thermal conductivity of the seed layer.

[0014] The material of the optional upper or lower heat absorption layer can be tantalum, titanium, copper, molybdenum, gold, silver, aluminum, platinum, or tin.

[0015] The material of the optional laser absorbing layer is carbon black, or a non-magnetic laser absorbing resin containing carbon black, or a laser absorbing paint.

[0016] The material of the optional laser transmitting layer can be ZrO2, Ti3O5, Ta2O5, HfO2, ZnS, ZnSe, Al2O3, MgO, MgF2, SiO2, YbF3 or AlF3.

[0017] The thickness of the optional upper or lower heat absorption layer is determined by the power of the external laser annealing and the heating time.

[0018] Optionally, in a bottom-up direction: an upper heat absorption layer covering the upper electrode layer and the lower electrode layer, the upper heat absorption layer being electrically isolated from the upper electrode layer; The upper heat absorption layer has a first region and a second region. The first region overlaps the lower electrode layer but does not overlap the upper electrode layer. The second region overlaps the upper electrode layer. An insulating material is buried between the upper heat absorption layer and the upper electrode layer. The first region and the second region are in electrical contact.

[0019] Optionally, the upper heat absorption layer also comprises a third region that does not overlap with the upper electrode layer and the lower electrode layer and that is in electrical contact with the first region and the second region, respectively.

[0020] Optionally, in a bottom-up direction: an upper heat absorption layer covering the upper electrode layer and the lower electrode layer, the upper heat absorption layer being in electrical contact with the upper electrode layer; The upper heat absorption layer includes a first region and a second region. The first region overlaps with the lower electrode layer but does not overlap with the upper electrode layer. The second region overlaps with the upper electrode layer. The first region is electrically isolated from the second region.

[0021] Optionally, the upper heat absorption layer also comprises a third region that does not overlap with the upper electrode layer and the lower electrode layer and is electrically isolated from the first region and the second region, respectively.

[0022] Optionally, in a bottom-up direction: the lower heat absorption layer covers the upper electrode layer and the lower electrode layer, and the lower heat absorption layer is electrically isolated from the lower electrode layer; The lower heat absorption layer has a fourth region and a fifth region. The fourth region overlaps the lower electrode layer but does not overlap the upper electrode layer. The fifth region overlaps the lower electrode layer. An insulating material is buried between the lower heat absorption layer and the lower electrode layer. The fourth region and the fifth region are in electrical contact.

[0023] Optionally, the lower heat absorption layer also comprises a sixth region that does not overlap with the upper electrode layer and the lower electrode layer and that is in electrical contact with the fourth region and the fifth region, respectively.

[0024] Optionally, in a bottom-up direction: The lower heat absorption layer covers the upper electrode layer and the lower electrode layer, and the lower heat absorption layer and the lower electrode layer are in electrical contact. The lower heat absorption layer includes a fourth region and a fifth region. The fourth region overlaps with the lower electrode layer but does not overlap with the upper electrode layer. The fifth region overlaps with the lower electrode layer. The fourth region is electrically isolated from the fifth region.

[0025] Optionally, the lower heat absorption layer also comprises a sixth region, which does not overlap with the upper electrode layer and the lower electrode layer and is electrically isolated from the fourth region and the fifth region, respectively.

[0026] It should be noted that the above description that the heat absorption layer covers the electrode layer in a bottom-up direction actually means that the projection of the heat absorption layer in a bottom-up direction covers the projection of the electrode layer in a bottom-up direction, which will not be described in detail below.

[0027] The above are the main solutions provided by the embodiments of the present invention. The layer structure of the magnetoresistive sensor provided by the embodiments of the present invention will be described in detail with reference to the accompanying drawings and through specific embodiments.

[0028] FIG. 1 shows a schematic diagram of a layer structure of a magnetoresistive sensor provided in an embodiment of the present invention. As shown in FIG. 1, the layer structure 1(0) of the magnetoresistive sensor includes an upper heat absorption layer 13 located above an upper electrode layer 7. Specifically, the layer structure 1(0) of the magnetoresistive sensor includes, from bottom to top, at least a substrate 2, a passivation layer 3, a magnetoresistive sensing unit 41, the upper heat absorption layer 13, a laser absorption layer 8, and a laser transmission layer 9. Among them, the magnetoresistive sensing unit 41 includes, from bottom to top, a seed layer 4, a lower electrode layer 5, a stacking layer 6 of the magnetic sensing unit, and an upper electrode layer 7. The stacking layer 6 of the magnetic sensing unit includes at least an antiferromagnetic pinning layer or permanent magnet bias layer 5(0).

[0029] The optional substrate 2 is typically, but not limited to, a silicon wafer. The optional passivation layer 3 is an insulating layer with low thermal conductivity that prevents heat conduction from above to the substrate 2. The thermal conductivity of the passivation layer 3 can be 1 / 10 of that of the seed layer 4, but is not limited thereto as long as it ensures the stability of the layer structure of the magnetoresistive sensor.

[0030] The magnetoresistive sensing units 41 in the layer structure 1(0) of the magnetoresistive sensor are interconnected via the lower electrode layer 5 and the upper electrode layer 7. An insulating material 10 is buried between the layers of the magnetoresistive sensing units 41 in the layer structure 1(0) of the magnetoresistive sensor and can be used for insulation between the layers of the magnetoresistive sensing units 41. The insulating material 10 is buried between the magnetoresistive sensing units 41 and the upper heat absorption layer 13 in the layer structure 1(0) of the magnetoresistive sensor to achieve electrical isolation.

[0031] The magnetoresistive sensor layer structure 1(0) is annealed by using a laser, where the scanning direction 12 of the laser spot 11 on the surface of the magnetoresistive sensor layer structure 1(0) is horizontal.

[0032] 2 shows a schematic diagram of a layer structure of another magnetoresistive sensor provided in an embodiment of the present invention. As shown in FIG. 2, the layer structure 1(1) of the magnetoresistive sensor includes a lower heat absorption layer 14 located below a lower electrode layer 5. Specifically, the layer structure 1(1) of the magnetoresistive sensor includes, from bottom to top, at least a substrate 2, a passivation layer 3, the lower heat absorption layer 14, a magnetoresistive sensing unit 41, a laser absorption layer 8, and a laser transmission layer 9. The parts of FIG. 2 that are the same as those in FIG. 1 will not be described again.

[0033] An insulating material 10 is embedded between the magnetoresistive sensing unit 41 and the lower heat absorption layer 14 in the layer structure 1(1) of the magnetoresistive sensor to achieve electrical isolation.

[0034] 3 is a schematic diagram of a layer structure of another magnetoresistive sensor according to an embodiment of the present invention. As shown in FIG. 3, the layer structure 1(2) of the magnetoresistive sensor includes a lower heat absorption layer 14 located below the lower electrode layer 5 and an upper heat absorption layer 13 located above the upper electrode layer 7. Specifically, the layer structure 1(2) of the magnetoresistive sensor includes, from bottom to top, at least a substrate 2, a passivation layer 3, the lower heat absorption layer 14, a magnetoresistive sensing unit 41, the upper heat absorption layer 13, a laser absorption layer 8, and a laser transmission layer 9. The parts of FIG. 3 that are the same as those in FIG. 1 will not be described again.

[0035] The insulating material 10 is buried between the magnetoresistive sensing unit 41 and the upper heat absorption layer 13 in the layer structure 1(2) of the magnetoresistive sensor to achieve electrical isolation. The insulating material 10 is buried between the magnetoresistive sensing unit 41 and the lower heat absorption layer 14 in the layer structure 1(2) of the magnetoresistive sensor to achieve electrical isolation.

[0036] In the layer structure of the magnetoresistive sensor in FIG. 1, it can be seen that the layer structure 1(0) of the magnetoresistive sensor has three regions with different material structures, namely, region A, region B, and region C. Among them, the material structure of region A is laser transmitting layer 9 / laser absorbing layer 8 / upper heat absorbing layer 13 / insulating material 10 / lower electrode layer 5 / seed layer 4. The material structure of region B is laser transmitting layer 9 / laser absorbing layer 8 / upper heat absorbing layer 13 / insulating material 10 / upper electrode layer 7 / stack layer 6 of the magnetic sensing unit / lower electrode layer 5 / seed layer 4. The material structure of region C is laser transmitting layer 9 / laser absorbing layer 8 / upper heat absorbing layer 13 / insulating material 10 / upper electrode layer 7 / insulating material 10.

[0037] In the layer structure of the magnetoresistive sensor in Figure 2, the layer structure 1 (1) of the magnetoresistive sensor has three regions with different material structures, namely, region A, region B, and region C. Among them, the material structure of region A is laser transmitting layer 9 / laser absorbing layer 8 / insulating material 10 / lower electrode layer 5 / seed layer 4 / insulating material 10 / lower heat absorption layer 14. The material structure of region B is laser transmitting layer 9 / laser absorbing layer 8 / insulating material 10 / upper electrode layer 7 / stacking layer 6 of the magnetic sensing unit / lower electrode layer 5 / seed layer 4 / insulating material 10 / lower heat absorption layer 14. The material structure of region C is laser transmitting layer 9 / laser absorbing layer 8 / insulating material 10 / upper electrode layer 7 / insulating material 10 / lower heat absorption layer 14.

[0038] In the layer structure of the magnetoresistive sensor in Figure 3, the layer structure 1 (2) of the magnetoresistive sensor has three regions with different material structures: Region A, Region B, and Region C. Region A's material structure is: laser transmitting layer 9 / laser absorbing layer 8 / upper heat absorbing layer 13 / insulating material 10 / lower electrode layer 5 / seed layer 4 / insulating material 10 / lower heat absorbing layer 14. Region B's material structure is: laser transmitting layer 9 / laser absorbing layer 8 / upper heat absorbing layer 13 / insulating material 10 / upper electrode layer 7 / stack layer 6 of the magnetic sensing unit / lower electrode layer 5 / seed layer 4 / insulating material 10 / lower heat absorbing layer 14. Region C's material structure is: laser transmitting layer 9 / laser absorbing layer 8 / upper heat absorbing layer 13 / insulating material 10 / upper electrode layer 7 / insulating material 10 / lower heat absorbing layer 14.

[0039] During the laser annealing step, the laser heats up instantaneously and transfers heat from the top surface of the magnetoresistive sensor layer structure to its bottom surface.

[0040] Without the heat absorption layer, the different material structures in regions A, B, and C will result in different products of volume, specific heat, and density in different regions of the layer structure of the magnetoresistive sensor, as well as different heat transfer efficiencies and temperature rise effects, thus causing the temperatures in regions A and C to be higher than the melting points of the lower electrode layer 5 and the upper electrode layer 7, and damaging regions A and C.

[0041] In an embodiment of the present invention, a lower heat absorption layer 14 and / or an upper heat absorption layer 13 is added. The product of the volume, specific heat, and density of the upper heat absorption layer 13 is higher than the product of the volume, specific heat, and density of the corresponding upper electrode layer 7, and the product of the volume, specific heat, and density of the lower heat absorption layer 14 is higher than the product of the volume, specific heat, and density of the corresponding lower electrode layer 5. Assuming that the stacking layer 6 of the magnetic sensing unit includes an antiferromagnetic pinning layer 5(0), when the writing temperature of the antiferromagnetic pinning layer 5(0) is higher than its blocking temperature, the temperature of the lower electrode layer 5 is lower than its melting point, and the temperature of the upper electrode layer 7 is lower than its melting point. Alternatively, assuming that the stacking layer 6 of the magnetic sensing unit includes a permanent magnet bias layer 5(0), when the writing temperature of the permanent magnet bias layer 5(0) is higher than its Curie temperature, the temperature of the lower electrode layer 5 is lower than its melting point, and the temperature of the upper electrode layer 7 is lower than its melting point, thus avoiding damage to the layer structure of the magnetoresistive sensor.

[0042] The following description is based on certain principles and rules.

[0043] Using a simple one-dimensional heat conduction model, the temperature rise of a material can be expressed as law (1) as follows:

number

[0044] For the case where Region A and Region C have a single material, the calculation is as follows: The material mass m is expressed as law (2): m=ρ·V (2). where ρ is the density (unit: kg / m 3 ), and v is the heating volume (unit: m 3 ) The heated volume V can be expressed as law (3): v = W·h·d (3). where W is the width of region A, region B, or region C, h is the thickness of region A, region B, or region C, and d is the diameter of the laser spot.

[0045] For the case where multi-materials are introduced into region A, region B, and region C the calculation is as follows: The total heated volume V can be expressed as law (4): V = Σ i V i (4) The total material mass M is expressed as law (5):

number

number

number

number

[0046] When no heat absorbing layer is provided in the layer structure of the magnetoresistive sensor, the material properties and temperature rise results of Region A, Region B, and Region C are set forth in Tables 1 to 4 below.

[0047] Table 1 shows the material properties and temperature rise results for Region A, Region B, and Region C.

[0048] [Table 1]

[0049] As shown in Table 1 above, the laser annealing conditions are assumed to be a blocking temperature Tb = 350 °C, a laser power P of 5 W, a laser spot diameter d of 25 μm, and a heating time t, i.e., a holding time of 0.1 μs.

[0050] The dimensions of each layer in the magnetoresistive sensing unit are: Seed layer / bottom electrode layer (Ta): thickness 0.15um, width 15um, Upper electrode layer (Cu): thickness 1.00um, width 10um, Stacking layer of magnetic sensing unit (mainly NiFe): thickness 0.50um, width 5um Assume as follows.

[0051] For the magnetoresistive sensing unit composed of seed layer / bottom electrode layer / stacked layer of magnetic sensing unit / top electrode layer, the materials in different regions are as follows: the material of the magnetoresistive sensing unit in region A is mainly Ta, the material of the magnetoresistive sensing unit in region C is mainly Cu, and the material of the magnetoresistive sensing unit in region B is mainly composite material Ta / main NiFe / Cu.

[0052] It can be seen from Table 1 that during the laser annealing stage, when the temperature of the Ta / primary NiFe / Cu composite in region B reaches 394°C, it approaches the blocking temperature Tb = 350°C of the antiferromagnetic pinning layer. At this point, the temperature in region A reaches 3,903°C, which exceeds the melting point of the Ta bottom electrode layer, 3,017°C, and the temperature in region C reaches 613°C, which is lower than the melting point of Cu, 1,084°C. Clearly, ablation occurs within region A, disrupting the entire layer structure of the magnetoresistive sensor.

[0053] The thickness of the seed layer / bottom electrode layer is increased to 200 nm to decrease the temperature in region A. Table 2 shows the material properties and temperature increase results for different types of region A, region B, and region C.

[0054] [Table 2]

[0055] As shown in Table 2 above, the dimensions of each layer in the magnetoresistive sensing unit are: Seed layer / bottom electrode layer (Ta): thickness 0.20 um, width 15 um, Upper electrode layer (Cu): thickness 1.00um, width 10um, Stacking layer of magnetic sensing unit (mainly NiFe): thickness 0.50um, width 5um Assume that:

[0056] It can be seen from Table 2 that during the laser annealing stage, when the temperature of the Ta / primary NiFe / Cu composite in region B reaches 375°C, it approaches the blocking temperature Tb = 350°C of the antiferromagnetic pinning layer. At this point, the temperature in region A reaches 2933°C, which is lower than the melting point of Ta, 3017°C, and the temperature in region C reaches 613°C, which is lower than the melting point of Cu, 1084°C. Although ablation does not occur in region A, its temperature is still close to the melting point of the Ta bottom electrode layer, making it susceptible to ablation.

[0057] By further increasing the thickness of the seed layer / bottom electrode layer to 250 nm, Table 3 shows the material properties and temperature increase results of another type of region A, region B, and region C.

[0058] [Table 3]

[0059] As shown in Table 3 above, the dimensions of each layer in the magnetoresistive sensing unit are Seed layer / bottom electrode layer (Ta): thickness 0.25 um, width 15 um, Upper electrode layer (Cu): thickness 1.00um, width 10um, Stacking layer of magnetic sensing unit (mainly NiFe): thickness 0.50um, width 5um Assume as follows.

[0060] It can be seen from Table 3 that during the laser annealing stage, when the temperature of the Ta / primary NiFe / Cu composite in region B reaches 360°C, it reaches the blocking temperature Tb of the antiferromagnetic pinning layer = 350°C. At this point, the temperature in region A reaches 2,351°C, which is lower than the melting point of Ta, 3,017°C, and the temperature in region C reaches 613°C, which is lower than the melting point of Cu, 1,084°C. Although ablation does not occur in region A, the temperature difference between regions A / B / C is still much larger.

[0061] By increasing the thickness of the top electrode layer to 1.1 um, Table 4 shows the results of material properties and temperature increase of another type of region A, region B, and region C.

[0062] [Table 4]

[0063] As shown in Table 4 above, the dimensions of each layer in the magnetoresistive sensing unit are: Seed layer / bottom electrode layer (Ta): thickness 0.25 um, width 15 um, Upper electrode layer (Cu): thickness 1.10um, width 10um, Stacking layer of magnetic sensing unit (mainly NiFe): thickness 0.50um, width 5um Assume as follows.

[0064] It can be seen from Table 4 that during the laser annealing stage, when the temperature of the Ta / primary NiFe / Cu composite in region B reaches 341°C, it is lower than the blocking temperature Tb of the antiferromagnetic pinning layer, Tb=350°C. At this point, the temperature of region A reaches 2,351°C, which is lower than the melting point of Ta, Tb=3,017°C, and the temperature of region C reaches 559°C, which is lower than the melting point of Cu, Tb=1,084°C. However, the composite in region B cannot reach the blocking temperature and cannot complete the laser writing operation of the magnetoresistive sensing unit.

[0065] It can be seen from Tables 1 to 4 above that the efficiency of simply increasing the film thickness of the magnetoresistive sensor unit is very low.

[0066] Based on this, a heat absorption layer is added to the layer structure of the magnetoresistive sensor, and the material properties and temperature rise results of Region A, Region B, and Region C are described in Table 5 below.

[0067] [Table 5]

[0068] As shown in Table 5, for example, an upper heat absorption layer is added to regions A, B, and C, and the material of the upper heat absorption layer is Cu with a thickness of 2 um.

[0069] It can be seen that when the temperature of the composite material in region B reaches 429°C, the laser power increases to 20 W. However, the temperature in region A drops to 563°C, and the temperature in region C decreases to 492°C. The temperatures throughout regions A, B, and C are very close, well below the melting points of the top and bottom electrode layers. The laser power increases to 20 W, but the increase in laser power can be achieved by simply adjusting the laser parameters.

[0070] Based on this, a heat absorption layer is introduced, and the product of specific heat, density, and volume of the heat absorption layer is 3,328, which is much larger than the 214 of the lower electrode layer, the 932 of the upper electrode layer, and the 1,547 of the stacking layer of the magnetic sensing unit, which makes the temperatures of region A, region B, and region C very close to each other, far lower than the melting points of the upper and lower electrode layers.

[0071] The following explains that the heat absorption layer in the layer structure of the magnetoresistive sensor is mainly divided into two cases.

[0072] In the first case, the heat absorption layer is electrically isolated from the adjacent electrode layer by a very thin insulating layer for easy heat conduction. In this case, the arrangement of the heat absorption layer is not adversely affected by the arrangement of the electrode layers. Specifically, the upper heat absorption layer is electrically isolated from the upper electrode layer and / or the lower heat absorption layer is electrically isolated from the lower electrode layer.

[0073] In the second case, the heat absorption layer is in direct electrical contact with the adjacent electrode layer. Necessary electrical isolation must be provided between corresponding different regions of the heat absorption layer in the layer structure of the magnetoresistive sensor to prevent adjacent magnetoresistive sensing units from shorting due to conductive connections of the heat absorption layer. The advantage of this case is that the heat absorption layer transfers heat directly to the electrode layer. Specifically, the upper heat absorption layer is in electrical contact with the upper electrode layer, and electrical isolation must be provided between corresponding different regions of the upper heat absorption layer in the layer structure of the magnetoresistive sensor. And / or the lower heat absorption layer is in electrical contact with the lower electrode layer, and electrical isolation must be provided between corresponding different regions of the lower heat absorption layer in the layer structure of the magnetoresistive sensor.

[0074] For convenience of explanation, the following embodiment only illustrates the design of the upper heat absorption layer in the layer structure of a magnetoresistive sensor, and the design principles are also applicable to the design of the lower heat absorption layer in the layer structure of a magnetoresistive sensor. It can be understood that the design principles of the first region of the upper heat absorption layer are the same as those of the fourth region of the lower heat absorption layer. The design principles of the second region of the upper heat absorption layer are the same as those of the fifth region of the lower heat absorption layer. The design principles of the third region of the upper heat absorption layer are the same as those of the sixth region of the lower heat absorption layer.

[0075] For the case where an insulating material is used for electrical isolation between the upper heat absorption layer and the upper electrode layer, the topological structure is shown below.

[0076] FIG. 4 is a topological diagram of the upper heat absorption layer of a magnetoresistive sensor layer structure. The upper heat absorption layers 13 in two adjacent magnetoresistive sensor layer structures are electrically isolated from each other. In other embodiments, the upper heat absorption layers in two adjacent magnetoresistive sensor layer structures may optionally be directly connected to each other. The magnetoresistive sensor layer structure includes a pin 100 that is not covered by the upper heat absorption layer 13. As shown in FIG. 4 , in a bottom-up direction, the upper heat absorption layer 13 covers the upper electrode layer 7 and the lower electrode layer 5 and is electrically isolated from the upper electrode layer 7. The upper heat absorption layer 13 includes a first region and a second region. The first region overlaps the lower electrode layer 5 but does not overlap the upper electrode layer 7. The second region overlaps the upper electrode layer 7. An insulating material is embedded between the upper heat absorption layer 13 and the upper electrode layer 7. The first region and the second region are in electrical contact.

[0077] However, the first region of the upper heat absorption layer 13 corresponds to region A in the layer structure of the magnetoresistive sensor, and the second region of the upper heat absorption layer 13 corresponds to region E in the layer structure of the magnetoresistive sensor. Region E includes regions B and C.

[0078] The upper heat absorption layer 13 will be described in detail by defining regions D and F in the layer structure of the magnetoresistive sensor. The upper heat absorption layer region covered above the bottom electrode layer 5 is region D in the layer structure of the magnetoresistive sensor corresponding to the upper heat absorption layer 13. The upper heat absorption layer region covered above the top electrode layer 7 is region E in the layer structure of the magnetoresistive sensor corresponding to the upper heat absorption layer 13. The combined region F formed by regions D and E in the layer structure of the magnetoresistive sensor constitutes a topological structure corresponding to the upper heat absorption layer 13. Region G is the corresponding region not covered by the upper heat absorption layer 13, the top electrode layer 7, and the bottom electrode layer 5.

[0079] During laser scanning of the topological structure corresponding to Figure 4, there may be a difference in heat conduction between the region G not covered by the upper heat absorption layer 13 and the region F covered by the laser, but it does not affect the magnetic field annealing of the array area of ​​the magnetoresistive sensing units by the laser.

[0080] Figure 5 is a topological diagram of the upper heat absorption layer of the single-arm magnetoresistive sensor layer structure in Figure 4. In the magnetoresistive sensor layer structure, the topological structure of the upper heat absorption layer formed by the combination of all D and E regions of the magnetoresistive sensor layer structure is shown as reference numeral 130. The topological structure of all G regions is shown as reference numeral 140, which is not covered by the upper heat absorption layer 13, the upper electrode layer 7, and the lower electrode layer 5. The oval represents the magnetic sensing unit stacking layer 6.

[0081] FIG. 6 is a topological diagram of the upper heat absorption layer of the push-pull multi-arm magnetoresistive sensor layer structure in FIG. 4. 100 denotes a pin. The two left magnetoresistive sensing unit arms have an antiferromagnetic pinned layer magnetization direction 150, and the two right magnetoresistive sensing unit arms have an antiferromagnetic pinned layer magnetization direction 160, where the magnetization direction 150 is opposite to the magnetization direction 160. The connection between the upper heat absorption layer region above the upper electrode layer 7 and the upper heat absorption layer region above the lower electrode layer 5 in the magnetoresistive sensing unit array is denoted as 170. The upper heat absorption layer connection region between the magnetoresistive sensing unit arrays is denoted as 172. The upper heat absorption layer region of the connection pin 100 is denoted as 171. 173 denotes the region not covered by the upper electrode layer 7, the lower electrode layer 5, and the upper heat absorption layer 13.

[0082] FIG. 7 is a topological diagram of the upper heat absorption layer of another magnetoresistive sensor layer structure. The upper heat absorption layers 13 of two adjacent magnetoresistive sensor layer structures are directly connected. As shown in FIG. 7, the upper heat absorption layer 13 also includes a third region. The third region does not overlap with the upper electrode layer 7 and the lower electrode layer 5, and the third region is in electrical contact with the first and second regions, respectively. 100 denotes a pin, the upper portion of which is not covered by the upper heat absorption layer 13. Region E of the magnetoresistive sensor layer structure above the upper electrode layer 7 corresponds to the second region of the upper heat absorption layer 13. Region A of the magnetoresistive sensor layer structure above the lower electrode layer 5 corresponds to the first region of the upper heat absorption layer 13. Region G not covered by the electrode layers corresponds to the third region of the upper heat absorption layer 13.

[0083] 8 is a topological diagram of the upper heat absorption layer of the single-arm magnetoresistive sensor layer structure in FIG. 7. In the magnetoresistive sensor layer structure, the area except for the pin 100 is covered by the upper heat absorption layer 13.

[0084] 9 is a topological diagram of the upper heat absorption layer of the push-pull multi-arm magnetoresistive sensor layer structure in FIG. 7. Reference numeral 100 denotes a pin, and the area excluding the pin 100 is covered with the upper heat absorption layer 13.

[0085] 10 is a topological diagram of the upper heat absorption layer of another magnetoresistive sensor layer structure, in which the upper heat absorption layer 13 covers the upper electrode layer 7 and the lower electrode layer 6 from bottom to top, and the upper heat absorption layer 13 is in electrical contact with the upper electrode layer 7, which can reduce the thermal conduction barrier.

[0086] To avoid short circuits between the magnetoresistive sensing units 6, the upper heat absorption layer 13 comprises a first region and a second region, the first region overlaps the lower electrode layer 5 but does not overlap the upper electrode layer 7, the second region overlaps the upper electrode layer 7, a gap is between the upper heat absorption layer in the first region and the upper heat absorption layer in the second region, the first region and the second region are electrically isolated from each other, and the upper heat absorption layer above region A and the upper heat absorption layer above region B are electrically isolated from each other. In addition, the pins 100 are not covered by the upper heat absorption layer 13, and region G of the magnetoresistive sensor layer structure is not covered by the upper heat absorption layer 13.

[0087] Figure 11 is a topological diagram of the upper heat absorption layer of the single-arm magnetoresistive sensor layer structure in Figure 10. 100 is a pin, which is not covered by the upper heat absorption layer 13. At this time, the upper heat absorption layer above the upper electrode layer 7 is 134, and the upper heat absorption layer corresponding to region A is 135, and 134 and 135 are electrically isolated from each other. The region not covered by the electrode layer is shown as 136, which is not covered by the heat absorption layer.

[0088] 12 is a topological diagram of the upper heat absorption layer of the push-pull multi-arm magnetoresistive sensor layer structure in FIG. 10. 100 is a pin, which is not covered by the heat absorption layer. The upper heat absorption layer above the upper electrode layer 7 is 137. The upper heat absorption layer above the lower electrode layer 5 is 138. The upper heat absorption layer connection area between the magnetoresistive sensing unit arrays is labeled 142. The upper heat absorption layer area connected to the pin 100 is labeled 141, and 139 is the area not covered by the upper electrode layer 7, the lower electrode layer 5, and the upper heat absorption layer 13.

[0089] 13 is a topological diagram of the upper heat absorption layer of another magnetoresistive sensor layer structure. 100 is a pin that is not covered by the heat absorption layer. The first region of the upper heat absorption layer 13 corresponds to region A of the magnetoresistive sensor layer structure. The second region of the upper heat absorption layer 13 corresponds to region E of the magnetoresistive sensor layer structure. The third region of the upper heat absorption layer 13 corresponds to region G of the magnetoresistive sensor layer structure that is not covered by an electrode layer. The third region is electrically isolated from the first and second regions, respectively, or the first and third regions, taken as a combination, are electrically isolated from the second region.

[0090] 14 is a topological diagram of the upper heat absorption layer of the single-arm magnetoresistive sensor layer structure in FIG. 13. 100 is a pin that is not covered by the heat absorption layer. At this time, the upper heat absorption layer above the upper electrode layer 7 is 151. The upper heat absorption layer above the lower electrode layer 5 is 152. The upper heat absorption layer above the area not covered by the electrode layer is 153. The upper heat absorption layers 152 and 153 are combined to form the upper heat absorption layer 154, and 154 and 151 are electrically isolated from each other.

[0091] FIG. 15 is a topological diagram of the upper heat absorption layer of the layer structure of the push-pull multi-arm magnetoresistive sensor in FIG. 13. 100 is a pin, above which there is no heat absorption layer. The upper heat absorption layer above the upper electrode layer is 161. The upper heat absorption layer connection region between the magnetoresistive sensing unit arrays is labeled 164. The upper heat absorption layer region connected to pin 100 is labeled 165. The upper heat absorption layer above the lower electrode layer is 162. The upper heat absorption layer corresponding to the region not covered by the electrode layer is 163. A bond 166 is formed by 162 and 163, and the upper heat absorption layer region 166 is electrically isolated from the upper heat absorption layer region 161.

[0092] It should be noted that the above description is merely a preferred embodiment and technical principle of the present invention. Those skilled in the art should understand that the present invention is not limited to the specific embodiments herein, and that various obvious modifications, rearrangements, mutual combinations, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail using the above embodiments, the present invention is not limited to the above embodiments. Many other equivalent embodiments can be included without departing from the concept of the present invention, and the scope of the present invention is defined by the appended claims.

Claims

1. A layer structure of a magnetoresistive sensor for laser annealing, comprising: substrate, a magnetoresistive sensing unit located on the substrate, the magnetoresistive sensing unit comprising, in order from bottom to top, a seed layer, a bottom electrode layer, a stacking layer of a magnetic sensing unit, and a top electrode layer, the stacking layer of the magnetic sensing unit comprising at least an antiferromagnetic pinning layer or a permanent magnet bias layer; an upper heat absorption layer located above the magnetoresistive sensing unit and / or a lower heat absorption layer located below the magnetoresistive sensing unit, wherein a product of the volume, specific heat, and density of the upper heat absorption layer is greater than a product of the volume, specific heat, and density of the upper electrode layer, and a product of the volume, specific heat, and density of the lower heat absorption layer is greater than a product of the volume, specific heat, and density of the lower electrode layer, and when a write temperature of the antiferromagnetic pinning layer or the permanent magnet bias layer is higher than a corresponding blocking temperature or Curie temperature, the temperatures of the lower electrode layer and the upper electrode layer are lower than their corresponding melting point temperatures; a laser absorption layer positioned above the magnetoresistive sensing unit; a laser transmitting layer located above the laser absorbing layer; In the bottom to top direction, the upper heat absorption layer is electrically isolated from the upper electrode layer and has an area that does not overlap with the upper electrode layer and the lower electrode layer, or the upper heat absorption layer is in electrical contact with the upper electrode layer; or A layer structure of a magnetoresistive sensor, characterized in that the lower heat absorption layer is electrically isolated from the lower electrode layer and has an area that does not overlap with the upper electrode layer and the lower electrode layer, or the lower heat absorption layer and the lower electrode layer are in electrical contact.

2. 2. The magnetoresistive sensor layer structure of claim 1, wherein a passivation layer is provided on one surface of the substrate facing the magnetoresistive sensing unit, and the thermal conductivity of the passivation layer is less than 1 / 10 of the thermal conductivity of the seed layer.

3. In the bottom to top direction, when the upper heat absorption layer is electrically isolated from the upper electrode layer, the upper heat absorption layer covers the upper electrode layer and the lower electrode layer; 2. The magnetoresistive sensor layer structure of claim 1, wherein the upper heat absorption layer comprises a first region and a second region, the first region overlapping the lower electrode layer and not overlapping the upper electrode layer, the second region overlapping the upper electrode layer, an insulating material is buried between the upper heat absorption layer and the upper electrode layer, and the first region and the second region are in electrical contact.

4. 4. The magnetoresistive sensor layer structure of claim 3, wherein the upper heat absorption layer also comprises a third region, the third region not overlapping the upper electrode layer and the lower electrode layer, and the third region being in electrical contact with the first region and the second region, respectively.

5. In the bottom to top direction, When the upper heat absorption layer and the upper electrode layer are in electrical contact, the upper heat absorption layer covers the upper electrode layer and the lower electrode layer; 2. The magnetoresistive sensor layer structure of claim 1, wherein the upper heat absorption layer comprises a first region and a second region, the first region overlapping the lower electrode layer but not overlapping the upper electrode layer, and the second region overlapping the upper electrode layer, the first region and the second region being electrically isolated from each other.

6. 6. The magnetoresistive sensor layer structure of claim 5, wherein the upper heat absorption layer also comprises a third region, the third region not overlapping the upper electrode layer and the lower electrode layer, and the third region being electrically isolated from the first region and the second region, respectively.

7. In the bottom to top direction, when the lower heat absorption layer and the lower electrode layer are electrically isolated from each other, the lower heat absorption layer covers the upper electrode layer and the lower electrode layer; 2. The magnetoresistive sensor layer structure of claim 1, wherein the lower heat absorption layer comprises a fourth region and a fifth region, the fourth region overlapping the lower electrode layer and not overlapping the upper electrode layer, the fifth region overlapping the lower electrode layer, an insulating material is buried between the lower heat absorption layer and the lower electrode layer, and the fourth region and the fifth region are in electrical contact.

8. 8. The magnetoresistive sensor layer structure of claim 7, wherein the lower heat absorption layer also comprises a sixth region, the sixth region not overlapping the upper electrode layer and the lower electrode layer, and the sixth region being in electrical contact with the fourth region and the fifth region, respectively.

9. In the bottom to top direction, When the lower heat absorption layer and the lower electrode layer are in electrical contact, the lower heat absorption layer covers the upper electrode layer and the lower electrode layer; 2. The magnetoresistive sensor layer structure of claim 1, wherein the lower heat absorption layer comprises a fourth region and a fifth region, the fourth region overlapping the lower electrode layer and not overlapping the upper electrode layer, the fifth region overlapping the lower electrode layer, and the fourth region and the fifth region being electrically isolated from each other.

10. 10. The magnetoresistive sensor layer structure of claim 9, wherein the lower heat absorption layer further comprises a sixth region, the sixth region not overlapping the upper electrode layer and the lower electrode layer, and the sixth region being electrically isolated from the fourth region and the fifth region, respectively.

11. 2. The magnetoresistive sensor layer structure of claim 1, wherein the material of the upper heat absorption layer or the lower heat absorption layer is tantalum, titanium, copper, molybdenum, gold, silver, aluminum, platinum, or tin.

12. 2. The magnetoresistive sensor layer structure according to claim 1, wherein the material of said laser absorbing layer is carbon black, or a non-magnetic laser absorbing resin containing carbon black, or a laser absorbing paint.

13. The material of the laser transmission layer is ZrO ２ , Ti ３ O ５ , Ta ２ O ５ , HfO ２ , ZnS, ZnSe, Al ２ O ３ , MgO, MgF ２ , SiO ２ , YbF ３ , or AlF ３ 2. The magnetoresistive sensor layer structure of claim 1, wherein:

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