Test structure and method for a magnetic memory array

Abstract

The application provides a test structure and a test method of a magnetic storage array. The test structure comprises a lower metal layer, an upper metal layer, a magnetic tunnel junction array, and an in-situ magnetic field structure. The magnetic tunnel junction array comprises a magnetic storage device to be tested. The in-situ magnetic field structure comprises at least one metal coil surrounding the magnetic storage device to be tested. By arranging the in-situ magnetic field structure in at least one metal layer of the upper and lower layers of the magnetic tunnel junction array, a vertical magnetic field can be applied to the magnetic storage device to be tested which is composed of a single or several magnetic tunnel junctions by passing current through the at least one metal coil, so as to test the anti-interference performance of the magnetic storage device to be tested in a read-write process. In addition, the in-situ magnetic field can be used to calculate important parameters such as the thermal stability factor of the magnetic storage device to be tested, so that part of the magnetic performance parameters of the magnetic storage device to be tested can be obtained in the WAT test, and the test result can reflect the characteristics of the magnetic tunnel junction array.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a test structure and test method for a magnetic storage array. Background Technology

[0002] Magnetic tunnel junctions (MTJs) are made from magnetic materials. Testing MTJs typically involves examining their operation and performance under a magnetic field. Currently, there are two main industrial approaches. One involves using a wafer magnetic field meter to apply a magnetic field to the MRAM (Magnetoresistive Random Access Memory) cell under test using electromagnets and probe cards. However, wafer magnetic field meters are expensive, and the magnetic field applied to the MRAM cell is over a large area, making it impossible to magnetize a specific MTJ within the MRAM cell in situ. The other approach uses ferromagnetic resonance (FMR) equipment or vibrating sample magnetometers. These devices involve slicing a wafer into small pieces, placing them between two ferromagnetic bodies, and using a current-carrying coil wound around the ferromagnetic bodies to generate a magnetic field for testing. Obviously, slicing the wafer damages it, and the parameters obtained only reflect the characteristics of the thin film sample. Summary of the Invention

[0003] This invention provides a test structure and test method for magnetic storage arrays. By adding an in-situ magnetic field structure to the MRAM manufacturing process, the test can not only measure the interference performance of a single magnetic tunnel junction against external magnetic fields during read and write operations using the in-situ magnetic field applied by the in-situ magnetic field structure, but also calculate important parameters such as the thermal stability factor of a single magnetic tunnel junction using the in-situ magnetic field applied by the in-situ magnetic field structure. This allows for the acquisition of some magnetic performance parameters of the magnetic storage device under test during WAT testing.

[0004] In a first aspect, the present invention provides a test structure for a magnetic storage array, the test structure comprising a lower metal layer and an upper metal layer above the lower metal layer, wherein a magnetic tunnel junction array is disposed between the lower metal layer and the upper metal layer, and wherein the magnetic tunnel junction array contains a magnetic storage device under test. The test structure further includes an in-situ magnetic field structure comprising at least one turn of metal coil surrounding the magnetic storage device under test, the at least one turn of metal coil being located within the lower metal layer and / or the upper metal layer.

[0005] In the above-described scheme, by setting an in-situ magnetic field structure within at least one metal layer of the upper and lower layers of the magnetic tunnel junction array during the MRAM manufacturing process, a vertical magnetic field can be applied to the magnetic storage device under test (MSD), which is composed of one or more MSDs, by passing current through at least one turn of a metal coil during testing. This allows for testing the MSD's resistance to external magnetic field interference during read / write operations. Furthermore, important parameters such as the thermal stability factor of the MSD can be calculated using the in-situ magnetic field structure, enabling the acquisition of some magnetic performance parameters during WAT testing, thus reflecting the characteristics of the MSD array. Additionally, since this invention adds an in-situ magnetic field structure to the existing MSD array structure and process, no additional mask or extra process steps are required to obtain the test structure, facilitating manufacturing.

[0006] In one specific embodiment, the at least one-turn metal coil is located within a metal layer of the lower or upper metal layer, and the at least one-turn metal coil is spirally arranged around the magnetic storage device under test. That is, a metal coil is added only within one metal layer, simplifying the structure and facilitating manufacturing.

[0007] In one specific embodiment, a portion of the metal coil in the at least one-turn metal coil is located within the lower metal layer, and the wiring metal coil is located within the upper metal layer. The portions of the metal coils located within the same metal layer are all spirally wound around the magnetic storage device under test. Furthermore, the metal coils in the upper metal layer and the metal coils in the lower metal layer are electrically connected through a conductive structure passing through the lower and upper metal layers. Adding metal coils to both the upper and lower metal layers applies a sufficiently large magnetic field space around the magnetic storage device under test, improving the accuracy and reliability of the test results.

[0008] In one specific embodiment, the conductive structure includes at least two magnetic tunnel junctions connected in parallel within a magnetic tunnel junction array. The top electrode of each of the at least two magnetic tunnel junctions is connected to a portion of a metal coil within an upper metal layer via a first conductive post, and the bottom electrode of each of the at least two magnetic tunnel junctions is connected to a portion of a metal coil within a lower metal layer via a second conductive post. By employing this tunnel junction as part of the passage through both the upper and lower metal layers, the test structure of this invention can be obtained using existing photomasks or additional process steps, facilitating fabrication.

[0009] In one specific implementation, the metal coils within each metal layer are spirally routed along the transverse or longitudinal direction of the magnetic tunnel junction array; and each metal segment of the transverse or longitudinal route in the metal coil is located directly above or below a column or row of magnetic tunnel junctions in the magnetic tunnel junction array, eliminating the need for significant dimensional adjustments to the existing mask and reducing alignment difficulties during the manufacturing process.

[0010] In one specific embodiment, the bottom electrode and top electrode of the magnetic storage device under test are electrically connected to a first pad and a second pad, respectively, and the first pad and the second pad are located within a lower metal layer or an upper metal layer. At least one turn of a metal coil has its two ends electrically connected to a third pad and a fourth pad, respectively, and the third pad and the fourth pad are located within a lower metal layer or an upper metal layer. This facilitates the flow of current through the at least one turn of the metal coil, enabling the testing of the electrical parameters between the bottom electrode and the top electrode of the magnetic storage device under test.

[0011] In one specific embodiment, the magnetic storage device under test (MSD) is a magnetic tunnel junction (MTJ) within a magnetic tunnel junction array, and the bottom electrode and top electrode of the MTJ are electrically connected to a first pad and a second pad, respectively. Alternatively, the MSD is an array of MTJs within a magnetic tunnel junction array, wherein the array comprises at least two MTJs connected in series; and the bottom electrode at one end of each of the at least two MTJs is electrically connected to the first pad, and the top electrode at the other end is electrically connected to the second pad. This facilitates the application of a vertical magnetic field to the MSD, which is composed of one or more MTJs.

[0012] Secondly, the present invention also provides a testing method based on any of the above-mentioned test structures. This testing method includes: applying a constant current excitation source to at least one turn of a metal coil to generate a vertical magnetic field of constant strength at the location of the magnetic storage device under test; simultaneously scanning the voltage or current between the bottom and top electrodes of the magnetic storage device under test to measure the change in resistance of the magnetic storage device under test under the vertical magnetic field as a function of voltage. By utilizing an in-situ magnetic field structure embedded within a metal layer, during testing, a vertical magnetic field is applied to the magnetic storage device under test, which is composed of one or more magnetic tunnel junctions, by passing current through at least one turn of the metal coil, thus testing the interference resistance of the magnetic storage device under test during read / write operations. Furthermore, the change in resistance of the magnetic storage device under test as a function of voltage can be obtained through the in-situ magnetic field applied by the in-situ magnetic field structure, enabling the acquisition of some magnetic performance parameters of the magnetic storage device under test during WAT testing, so that the test results can reflect the characteristics of the magnetic tunnel junction array.

[0013] Thirdly, this invention also provides another testing method based on any of the above-mentioned test structures. This method includes: applying a variable current excitation source to at least one turn of a metal coil to generate a vertical magnetic field of varying strength at the location of the magnetic storage device under test; simultaneously applying an excitation source with a set current value to the bottom and top electrodes of the magnetic storage device under test to measure the relationship between the resistance of the magnetic storage device under test and the vertical magnetic field. By utilizing an in-situ magnetic field structure embedded within a metal layer, during testing, a vertical magnetic field is applied to the magnetic storage device under test, which is composed of one or more magnetic tunnel junctions, by passing current through at least one turn of the metal coil, thus testing the device's resistance to external magnetic field interference during read / write operations. Furthermore, the relationship between the resistance of the magnetic storage device under test and the vertical magnetic field can be obtained through the in-situ magnetic field applied by the in-situ magnetic field structure, enabling the acquisition of some magnetic performance parameters of the magnetic storage device under test during WAT testing, allowing the test results to reflect the characteristics of the magnetic tunnel junction array.

[0014] Fourthly, this invention also provides another testing method based on any of the above-mentioned test structures. This method includes: applying a constant current excitation source to at least one turn of a metal coil to generate a vertical magnetic field of constant strength at the location of the magnetic storage device under test; simultaneously applying scanning voltages or currents of different pulse frequencies between the bottom and top electrodes of the magnetic storage device under test to measure the resistance of the magnetic storage device under test under the influence of the vertical magnetic field as a function of voltage. By utilizing an in-situ magnetic field structure embedded within a metal layer, during testing, a vertical magnetic field is applied to the magnetic storage device under test, which is composed of one or more magnetic tunnel junctions, by passing current through at least one turn of the metal coil, thus testing the resistance of the magnetic storage device under test to external magnetic field interference during read / write operations. Furthermore, the resistance-voltage relationship of the magnetic storage device under test can be obtained through the in-situ magnetic field applied by the in-situ magnetic field structure, enabling the acquisition of some magnetic performance parameters of the magnetic storage device under test during WAT testing, allowing the test results to reflect the characteristics of the magnetic tunnel junction array.

[0015] Fifthly, this invention also provides another testing method based on any of the above-mentioned test structures. This method includes: applying a constant current excitation source to at least one turn of a metal coil to generate a vertical magnetic field of constant strength at the location of the magnetic storage device under test; and testing the magnetic storage device under test through its bottom and top electrodes under the vertical magnetic field to obtain the required parameters of the magnetic storage device under test. By utilizing an in-situ magnetic field structure embedded within a metal layer, during testing, a vertical magnetic field is applied to the magnetic storage device under test, which is composed of one or more magnetic tunnel junctions, by passing current through at least one turn of the metal coil, thus testing the device's resistance to external magnetic field interference during read / write operations. Furthermore, important parameters of the magnetic storage device under test, such as the P-state (parallel state) / AP-state (anti-parallel state) resistance, TMR (tunnel magnetoresistance), switching voltage, and thermal stability factor, can be calculated using the in-situ magnetic field applied by the in-situ magnetic field structure. This allows for the acquisition of some magnetic performance parameters of the magnetic storage device under test during WAT testing, enabling the test results to reflect the characteristics of the magnetic tunnel junction array. Attached Figure Description

[0016] Figure 1 , Figure 2 These are top and cross-sectional schematic diagrams of a test structure for a magnetic storage array provided in an embodiment of the present invention.

[0017] Figure 3 , Figure 4 These are top and cross-sectional schematic diagrams of a test structure for another magnetic storage array provided in an embodiment of the present invention.

[0018] Figure 5 The Vc-Heff relationship curve of MRAM during operation is obtained by a test method provided in an embodiment of the present invention.

[0019] Figure label:

[0020] 10-Substrate 11-Lower metal layer 12-Upper metal layer 13-Dielectric layer

[0021] 20-Magnetic tunnel junction; 21-Top electrode; 22-Bottom electrode

[0022] 31-First pad 32-Second pad 33-Third pad 34-Fourth pad

[0023] 40 - Metal coil; 51 - First conductive post; 52 - Second conductive post Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] To facilitate understanding of the test structure for the magnetic storage array provided in this embodiment of the invention, the application scenario of the test structure is first described below. This test structure is applied to MRAM to test the magnetic storage array within the MRAM, wherein the MRAM can be an STT-MRAM. The test structure for the magnetic storage array will now be described in detail with reference to the accompanying drawings.

[0026] refer to Figure 1 , Figure 2 , Figure 3 and Figure 4 The test structure for a magnetic storage array provided in this embodiment of the invention includes a lower metal layer 11 and an upper metal layer 12 located above the lower metal layer 11. A magnetic tunnel junction 20 array is disposed between the lower metal layer 11 and the upper metal layer 12, wherein the magnetic tunnel junction 20 array contains the magnetic storage device under test. The test structure also includes an in-situ magnetic field structure, which includes at least one turn of metal coil 40 surrounding the magnetic storage device under test. The at least one turn of metal coil 40 is located within the lower metal layer 11 and / or the upper metal layer 12. That is, the at least one turn of metal coil 40 can be entirely located within the upper metal layer 12, or entirely located within the lower metal layer 11, or a portion of the at least one turn of metal coil 40 can be located within the lower metal layer 11 and a portion within the upper metal layer 12.

[0027] In the above-described scheme, by setting an in-situ magnetic field structure within at least one metal layer of the upper and lower layers of the magnetic tunnel junction 20 array during the MRAM manufacturing process, a vertical magnetic field can be applied to the magnetic storage device under test (MST), which consists of one or more MMTs 20, by passing current through at least one turn of the metal coil 40. This allows for testing the MMT's resistance to external magnetic field interference during read / write operations. Furthermore, important parameters such as the thermal stability factor of the MMT can be calculated using the in-situ magnetic field structure, enabling the acquisition of some magnetic performance parameters during WAT testing, thus reflecting the characteristics of the MMT 20 array. Additionally, since this invention adds an in-situ magnetic field structure to the existing MMT 20 array structure and process, no additional mask or process steps are required to obtain the test structure, facilitating manufacturing. The various structures described above will be described in detail below with reference to the accompanying drawings.

[0028] refer to Figure 1 and Figure 2 The lower metal layer 11 and the upper metal layer 12 are two different metal layers in the MRAM, wherein the lower metal layer 11 can be the Nth metal layer in the MRAM, i.e. Figures 1-4 The Mn shown can be the (N+1)th metal layer in the MRAM, i.e. Figures 1-4 The example shown is Mn+1. Here, n can be any positive integer such as 1, 2, or 3. Of course, both the lower metal layer 11 and the upper metal layer 12 are located on the substrate 10 of the MRAM (e.g., ...). Figure 2 and Figure 4 Above the silicon shown, and between the conductive metal lines, conductive pillars, and other conductive structures of the substrate 10, upper metal layer 12, and lower metal layer 11, an insulating dielectric layer 13 (such as...) is filled. Figure 2 and Figure 4 (Dielectric shown).

[0029] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, a magnetic tunnel junction array 20 is disposed between the lower metal layer 11 and the upper metal layer 12, that is, the magnetic tunnel junction array 20 contains multiple rows of magnetic tunnel junctions 20 and multiple columns of magnetic tunnel junctions 20. The bottom electrode 22 of the magnetic storage device under test ( Figure 2 and Figure 4 BE (Bottom Electrode) and Top Electrode 21 ( Figure 2 and Figure 4The TE (Top Electrode) in the image is electrically connected to the first pad 31 and the second pad 32, respectively. The first pad 31 and the second pad 32 are located within either the lower metal layer 11 or the upper metal layer 12. Specifically, the first pad 31 can be located within either the lower metal layer 11 or the upper metal layer 12; similarly, the second pad 32 can also be located within either the lower metal layer 11 or the upper metal layer 12. This facilitates testing the electrical parameters between the bottom electrode 22 and the top electrode 21 of the magnetic storage device under test. Figure 2 and Figure 4 As shown, a bottom electrode 22 is provided at the bottom of each magnetic tunnel junction 20, and a top electrode 21 is provided at the top of each magnetic tunnel junction 20. That is, the bottom electrode 22 of each magnetic tunnel junction 20 faces the lower metal layer 11, and the top electrode 21 faces the upper metal layer 12.

[0030] refer to Figure 1 and Figure 2 The magnetic tunnel junction 20 array includes a magnetic storage device under test (MSD). The MSD can be a single magnetic tunnel junction 20 within the array, or it can be an array of multiple magnetic tunnel junctions 20. For example... Figures 1-4 The magnetic storage device under test shown is a magnetic tunnel junction 20 in the array of magnetic tunnel junctions 20. The bottom electrode 22 and the top electrode 21 of the magnetic tunnel junction 20 under test are electrically connected to the first pad 31 and the second pad 32, respectively, so that during testing, the current or voltage change in the magnetic tunnel junction 20 under test can be scanned through the first pad 31 and the second pad 32, or current or voltage can be passed into the magnetic tunnel junction 20 under test. At the same time, it is convenient to apply a vertical magnetic field to the magnetic storage device under test as a single device.

[0031] When specifically implementing the electrical connection between the magnetic tunnel under test and the first pad 31 and the second pad 32, such as Figure 1 and Figure 3 The two methods are shown. First, refer to... Figure 1 and Figure 2 One configuration shown. First pad 31 ( Figure 1 and Figure 3 PAD A) is located within the lower metal layer 11, and the second pad 32 ( Figure 1 and Figure 3 PAD B) is also located within the lower metal layer 11. (See reference) Figure 1 and Figure 2 The second pad 32 is directly electrically connected to the bottom electrode 22 of the magnetic tunnel junction 20 under test via traces within the lower metal layer 11 and conductive posts between the lower metal layer 11 and the bottom electrode 22. The first pad 31, however, needs to pass sequentially through traces within the lower metal layer 11 and through conductive structures between the lower metal layer 11 and the upper metal layer 12 (such as...). Figure 1 and Figure 3The upper metal layer 12 contains traces (Via), and the conductive pillars between the upper metal layer 12 and the top electrode 21 of the magnetic tunnel junction 20 under test are used to achieve electrical connection with the top electrode 21 of the magnetic tunnel junction 20 under test.

[0032] refer to Figure 2 The conductive structure penetrating between the lower metal layer 11 and the upper metal layer 12 may include at least two magnetic tunnel junctions 20 connected in parallel in an array of magnetic tunnel junctions 20. The top electrode 21 of each of the at least two magnetic tunnel junctions 20 is connected to a trace within the upper metal layer 12 via a first conductive post 51, and the bottom electrode 22 of each of the at least two magnetic tunnel junctions 20 is connected to a trace within the lower metal layer 11 via a second conductive post 52. By using this tunnel junction as part of penetrating the upper metal layer 12 and the lower metal layer 11, the test structure of the present invention can be obtained using existing photomasks or additional process steps, facilitating fabrication. It should be understood that the arrangement of the conductive structure is not limited to the method shown above using magnetic tunnel junctions 20; other methods can also be used. For example, conductive posts penetrating both the lower metal layer 11 and the upper metal layer 12 can be directly used as the conductive structure.

[0033] Secondly, refer to Figure 3 and Figure 4 Another configuration is shown. The first pad 31 is located within the upper metal layer 12, and the second pad 32 is located within the lower metal layer 11. The first pad 31 is electrically connected to the top electrode 21 of the magnetic tunnel junction 20 under test via traces within the upper metal layer 12 and a conductive post between the upper metal layer 12 and the top electrode 21 of the magnetic tunnel junction 20 under test. The second pad 32 is electrically connected to the bottom electrode 22 of the magnetic tunnel junction 20 under test via traces within the lower metal layer 11 and a conductive post between the lower metal layer 11 and the bottom electrode 22 of the magnetic tunnel junction 20 under test.

[0034] It should be noted that the method of realizing the electrical connection between the magnetic tunnel under test and the first pad 31 and the second pad 32 is not limited to the method shown above. Other configuration methods can also be used.

[0035] Furthermore, the configuration of the magnetic storage device under test (MDD) is not limited to the method shown above, which uses a single magnetic tunnel junction 20 as the MTD. Other methods can also be used. For example, the MTD can be an array of MTDs 20, comprising at least two MTDs 20 connected in series. The bottom electrode 22 at one end of each of the at least two MTDs 20 is electrically connected to a first pad 31, and the top electrode 21 at the other end is electrically connected to a second pad 32. This facilitates the application of a vertical magnetic field to the MTD, which is composed of several MTDs 20. The series connection of at least two magnetic tunnel junctions 20 under test can be achieved by sequentially connecting the bottom electrode 22 and the top electrode 21 of at least two magnetic tunnel junctions 20 under test. Specifically, the structure of connecting the bottom electrode 22 and the top electrode 21 of different magnetic tunnel junctions 20 under test can be achieved by setting conductive pillars between the lower metal layer 11 and the bottom electrode 22, conductive pillars between the upper metal layer 12 and the top electrode 21, and traces within the upper and lower metal layers 11.

[0036] When setting up the in-situ magnetic field structure, the number of turns of the metal coil 40 included in the in-situ magnetic field structure can be at least one turn, such as 1 turn, 2 turns, 3 turns, or 4 turns. Of course, the number of turns of the metal coil 40 is not limited to the integer multiples shown above, and can also be non-integer multiples such as 1.5 turns or 5.5 turns, that is, as long as the metal coil 40 can wrap around the magnetic storage device under test at least once. The at least one turn of the metal coil 40 can be entirely located in the upper metal layer 12, or entirely located in the lower metal layer 11, or a portion of the metal coil 40 can be located in the lower metal layer 11 and a portion of the metal coil 40 can be located in the upper metal layer 12.

[0037] refer to Figure 1 and Figure 3 At least one turn of metal coil 40 has a third solder pad 33 electrically connected to each end. Figure 1 and Figure 3 PAD 1) and fourth pad 34 ( Figure 1 and Figure 3 (PAD 2 in the diagram). The third pad 33 can be located within the lower metal layer 11 or the upper metal layer 12; similarly, the fourth pad 34 can also be located within the lower metal layer 11 or the upper metal layer 12. This is to facilitate the supply of current to at least one turn of the metal coil 40.

[0038] When setting the above-mentioned at least one turn of metal coil 40, such as Figure 1 and Figure 2In one embodiment, the at least one-turn metal coil 40 is entirely located within the upper metal layer 12, and the at least one-turn metal coil 40 spirals around the magnetic storage device under test. This simplifies the structure and facilitates manufacturing by adding the metal coil 40 only within the upper metal layer 12. The third pad 33 is located within the lower metal layer 11, and the fourth pad 34 is located within the upper metal layer 12. The fourth pad 34 is directly electrically connected to a trace leading out from one end of the metal coil 40. However, the third pad 33 needs to be electrically connected to one end of the at least one-turn metal coil 40 located entirely within the upper metal layer 12 via a trace within the lower metal layer 11, a conductive structure passing through the lower metal layer 11 and the upper metal layer 12. The conductive structure can also employ the magnetic tunnel junction 20 shown above. The conductive structure includes at least two parallel magnetic tunnel junctions 20 located in the array of magnetic tunnel junctions 20. The top electrode 21 of each of the at least two magnetic tunnel junctions 20 is connected to the end of at least one turn of metal coil 40 within the upper metal layer 12 via a first conductive post 51. The bottom electrode 22 of each of the at least two magnetic tunnel junctions 20 is connected to a trace within the lower metal layer 11 via a second conductive post 52. By using this tunnel junction as part of the passage through the upper metal layer 12 and the lower metal layer 11, the test structure of this invention can be obtained using existing photomasks or additional process steps, facilitating manufacturing. Alternatively, the third pad 33 can be placed within the upper metal layer 12 and directly electrically connected to the trace leading out from one end of the at least one turn of metal coil 40. Furthermore, it should be noted that the at least one turn of metal coil 40 can also be entirely placed within the lower metal layer 11, similarly making the at least one turn of metal coil 40 spirally surround the magnetic storage device under test. The specific arrangement is similar to... Figure 1 and Figure 2 The setup method shown is similar, so it will not be repeated here.

[0039] Of course, some of the metal coils 40 in the at least one-turn metal coil 40 can be located within the lower metal layer 11, and the wiring metal coil 40 can be located within the upper metal layer 12. The metal coils 40 located within the same metal layer are all spirally arranged around the magnetic storage device under test. That is, the metal coils 40 located within the lower metal layer 11 are also spirally arranged around the magnetic storage device under test, and the metal coils 40 located within the upper metal layer 12 are also spirally arranged around the magnetic storage device under test, so that an in-situ magnetic field can be formed above and below the magnetic storage device under test. By adding metal coils 40 to both the upper metal layer 12 and the lower metal layer 11, a sufficiently large magnetic field space is applied around the magnetic storage device under test, improving the accuracy and reliability of the test results. Furthermore, the metal coil 40 in the upper metal layer 12 and the metal coil 40 in the lower metal layer 11 are electrically connected through a conductive structure passing through the lower metal layer 11 and the upper metal layer 12. This allows some of the metal coils 40 in the upper metal layer 12 and some of the metal coils 40 in the lower metal layer 11 to be directly or indirectly electrically connected to the third pad 33 and the fourth pad 34. Thus, current can be supplied to all the metal coils 40 by simply passing current through a pair of pads (the third pad 33 and the fourth pad 34) from the outside.

[0040] In implementing the electrical connection between the metal coils 40 within different metal layers, the conductive structure penetrating between the lower metal layer 11 and the upper metal layer 12 may include at least two magnetic tunnel junctions 20 connected in parallel within an array of magnetic tunnel junctions 20. The top electrode 21 of each of these at least two magnetic tunnel junctions 20 is connected to a portion of the metal coil 40 within the upper metal layer 12 via a first conductive post 51, and the bottom electrode 22 of each of these at least two magnetic tunnel junctions 20 is connected to a portion of the metal coil 40 within the lower metal layer 11 via a second conductive post 52. By employing this tunnel junction as part of the connection between the upper metal layer 12 and the lower metal layer 11, the test structure of this invention can be obtained using existing photomasks or additional process steps, facilitating fabrication.

[0041] like Figure 3 and Figure 4 The illustration shows an arrangement where both the lower metal layer 11 and the upper metal layer 12 have metal coils 40. (Refer to...) Figure 3At least one turn of metal coil 40 is introduced from the third pad 33 as one end, and then wraps around the magnetic storage device under test in the upper metal layer 12 to about 3 / 4 of a turn. It is then introduced into the lower metal layer 11 through the conductive structure shown above, and wraps around the magnetic storage device under test in the lower metal layer 11 to about 1 / 2 of a turn. It is then introduced back into the upper metal layer 12 through the conductive structure shown above, and continues to wrap around the magnetic storage device under test in the upper metal layer 12 to more than 1 / 2 of a turn. Finally, it is led out to the fourth pad 34 and electrically connected to the fourth pad 34. It should be noted that the method of providing metal coil 40 in both the upper and lower metal layers 11 is not limited to... Figure 3 and Figure 4 This is one method shown; other settings can also be used.

[0042] Additionally, refer to Figure 1 and Figure 3 Each metal coil 40 within a metal layer can be arranged in a spiral pattern along the transverse or longitudinal direction of the magnetic tunnel junction 20 array. This means the metal coil 40 is composed of multiple segments of transverse or longitudinal lines connected end-to-end, facilitating the fabrication of the metal coil 40. Alternatively, each segment of the transverse or longitudinal line in the metal coil 40 can be positioned directly above or below a column or row of magnetic tunnel junctions 20 in the array. This eliminates the need for significant dimensional adjustments to the existing mask, reducing alignment difficulties during manufacturing. It should be noted that the arrangement of the metal coil 40 is not limited to the spiral pattern along the transverse or longitudinal direction of the magnetic tunnel junction 20 array shown above; other spiral patterns can also be used.

[0043] By incorporating an in-situ magnetic field structure within at least one metal layer of the upper and lower layers of the magnetic tunnel junction 20 array during the MRAM manufacturing process, a vertical magnetic field can be applied to the magnetic storage device under test (MST), which consists of one or more MMTs 20, by passing current through at least one turn of a metal coil 40. This allows for testing the MMT's resistance to external magnetic field interference during read / write operations. Furthermore, the in-situ magnetic field structure applied by the in-situ magnetic field can be used to calculate important parameters such as the thermal stability factor of the MMT, enabling the acquisition of some magnetic performance parameters during WAT testing. This allows the test results to reflect the characteristics of the MMT 20 array. Additionally, since this invention adds an in-situ magnetic field structure to the existing MMT 20 array structure and process, no additional mask or processing steps are required to obtain the test structure, thus facilitating manufacturing.

[0044] In addition, embodiments of the present invention also provide a test method based on any of the above-described test structures, see reference. Figures 1-4 The testing method includes:

[0045] An excitation source with a constant current is applied to at least one turn of a metal coil 40 to generate a vertical magnetic field with a constant magnetic field strength at the location of the magnetic storage device under test.

[0046] Simultaneously scan the voltage or current between the bottom electrode 22 and the top electrode 21 of the magnetic storage device under test to measure the relationship between the resistance of the magnetic storage device under test and the voltage under the action of a vertical magnetic field.

[0047] By utilizing an in-situ magnetic field structure embedded within a metal layer, a vertical magnetic field is applied to the magnetic storage device under test (MSD), which consists of one or more magnetic tunnel junctions 20, by passing current through at least one turn of a metal coil 40 during testing. This allows for the testing of the MSD's resistance to external magnetic field interference during read / write operations. Furthermore, the in-situ magnetic field structure applied by the in-situ magnetic field structure allows for the acquisition of the resistance-voltage relationship of the MSD, enabling the acquisition of some magnetic performance parameters during WAT testing. This ensures that the test results reflect the characteristics of the magnetic tunnel junction 20 array.

[0048] Furthermore, embodiments of the present invention also provide another testing method based on any of the above-described test structures, see reference. Figures 1-4 The testing method includes:

[0049] An excitation source with varying current is applied to at least one turn of a metal coil 40 to generate a vertical magnetic field with varying magnetic field strength at the location of the magnetic storage device under test.

[0050] Simultaneously, an excitation source with a set current value is applied to the bottom electrode 22 and top electrode 21 of the magnetic storage device under test to measure the relationship between the resistance of the magnetic storage device under test and the vertical magnetic field.

[0051] By utilizing an in-situ magnetic field structure embedded within a metal layer, a vertical magnetic field is applied to the magnetic storage device under test (MSD), which consists of one or more magnetic tunnel junctions 20, by passing a current through at least one turn of a metal coil 40 during testing. This allows for the testing of the MSD's resistance to external magnetic field interference during read / write operations. Furthermore, the in-situ magnetic field structure applied by the in-situ magnetic field structure allows for the acquisition of the MSD's resistance as a function of the vertical magnetic field. This enables the acquisition of some magnetic performance parameters of the MSD during WAT testing, ensuring that the test results reflect the characteristics of the magnetic tunnel junction 20 array.

[0052] Furthermore, this invention also provides another test method based on any of the above-mentioned test structures, see reference. Figures 1-4 The testing method includes:

[0053] An excitation source with a constant current is applied to at least one turn of a metal coil 40 to generate a vertical magnetic field with a constant magnetic field strength at the location of the magnetic storage device under test.

[0054] Simultaneously, scanning voltages or currents with different pulse frequencies are applied between the bottom electrode 22 and the top electrode 21 of the magnetic storage device under test to measure the relationship between the resistance of the magnetic storage device under test and the voltage under the action of a vertical magnetic field.

[0055] By utilizing an in-situ magnetic field structure embedded within a metal layer, a vertical magnetic field is applied to the magnetic storage device under test (MSD), which consists of one or more magnetic tunnel junctions 20, by passing current through at least one turn of a metal coil 40 during testing. This allows for the testing of the MSD's resistance to external magnetic field interference during read / write operations. Furthermore, the in-situ magnetic field structure applied by the in-situ magnetic field structure allows for the acquisition of the resistance-voltage relationship of the MSD, enabling the acquisition of some magnetic performance parameters during WAT testing. This ensures that the test results reflect the characteristics of the magnetic tunnel junction 20 array.

[0056] Finally, this embodiment of the invention also provides another test method based on any of the above test structures, see reference. Figures 1-4 The testing method includes:

[0057] An excitation source with a constant current is applied to at least one turn of a metal coil 40 to generate a vertical magnetic field with a constant magnetic field strength at the location of the magnetic storage device under test.

[0058] Under a vertical magnetic field, the magnetic storage device under test is tested through the bottom electrode 22 and the top electrode 21 to obtain the required parameters of the magnetic storage device under test.

[0059] Specifically, the required parameters for the magnetic storage device under test can be its P-state / AP-state resistance, TMR, switching voltage, and thermal stability factor. To obtain these parameters, the device can first be tested under a vertical magnetic field using its bottom electrode 22 and top electrode 21 to obtain its DC-RV (voltage-resistance curve under DC signal), Pulse-IV (voltage-current curve affected by pulse signal), and Vc-PulseWidth curve (voltage distribution versus pulse width). Then, based on the DC-RV, Pulse-IV, and Vc-PulseWidth curves, the P-state / AP-state resistance, TMR, switching voltage, and thermal stability factor parameters can be extracted.

[0060] Thermal stability is a very important parameter in STT-MRAM. The thermal stability factor Δ is related to the barrier height EB and temperature. When a vertical magnetic field is applied to a vertically magnetized magnetic tunnel junction (pMTJ), the energy barrier between the two stable states of the pMTJ will change, which will cause the switching voltage Vc to change with the effective magnetic field Heeff. The thermal stability factor Δ is obtained by measuring the curve of VC with respect to Heeff.

[0061]

[0062] like Figure 5 The curve showing the Vc-Heff relationship of the MRAM during operation is obtained by testing using the test method shown in the embodiment of the present invention.

[0063] By utilizing an in-situ magnetic field structure embedded within a metal layer, a vertical magnetic field is applied to the magnetic storage device under test (MSD), which consists of one or more magnetic tunnel junctions 20, by passing current through at least one turn of a metal coil 40 during testing. This allows for the testing of the MSD's resistance to external magnetic field interference during read / write operations. Furthermore, the in-situ magnetic field applied by the structure allows for the calculation of important parameters of the MSD, such as P-state / AP-state resistance, TMR, switching voltage, and thermal stability factor. This enables the acquisition of some magnetic performance parameters of the MSD during WAT testing, allowing the test results to reflect the characteristics of the magnetic tunnel junction 20 array.

[0064] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A test structure for a magnetic storage array, characterized in that, include: Lower metal layer; An upper metal layer located above the lower metal layer; A magnetic tunnel junction array is disposed between the lower metal layer and the upper metal layer, wherein the magnetic tunnel junction array contains a magnetic storage device under test; The in-situ magnetic field structure includes: at least one turn of metal coil surrounding the magnetic storage device under test; the at least one turn of metal coil is located within the lower metal layer and / or the upper metal layer.

2. The test structure as described in claim 1, characterized in that, The at least one turn of the metal coil is located within one of the metal layers of the lower metal layer or the upper metal layer, and the at least one turn of the metal coil is spirally surrounding the magnetic storage device under test.

3. The test structure as described in claim 1, characterized in that, A portion of the metal coil in the at least one turn of the metal coil is located within the lower metal layer, and a portion of the metal coil is located within the upper metal layer; The partial metal coils located within the same metal layer are all spiral-shaped, surrounding the magnetic storage device under test. Furthermore, the metal coil in the upper metal layer and the metal coil in the lower metal layer are electrically connected through a conductive structure that passes through the lower metal layer and the upper metal layer.

4. The test structure as described in claim 3, characterized in that, The conductive structure includes at least two magnetic tunnel junctions connected in parallel in the magnetic tunnel junction array; Furthermore, the top electrode of each of the at least two magnetic tunnel junctions is connected to the portion of the metal coil in the upper metal layer via a first conductive post; and the bottom electrode of each of the at least two magnetic tunnel junctions is connected to the portion of the metal coil in the lower metal layer via a second conductive post.

5. The test structure as described in any one of claims 2 to 4, characterized in that, The metal coils within each metal layer are spiral-shaped along the transverse or longitudinal direction of the magnetic tunnel junction array; Furthermore, each metal segment of the horizontal or vertical trace in the metal coil is located directly above or below a column or row of magnetic tunnel junctions in the magnetic tunnel junction array.

6. The test structure as described in claim 1, characterized in that, Also includes: The first and second pads are electrically connected to the bottom and top electrodes of the magnetic storage device under test, respectively, and the first and second pads are located in the lower or upper metal layer. The third and fourth pads are electrically connected to the two ends of the metal coil, respectively, and the third and fourth pads are located in the lower or upper metal layer.

7. The test structure as described in claim 6, characterized in that, The magnetic storage device under test is one of the magnetic tunnel junctions in the array, and the bottom electrode and top electrode of the magnetic tunnel junction under test are electrically connected to the first pad and the second pad, respectively; or, The magnetic storage device under test is one of the magnetic tunnel junction arrays, wherein the magnetic tunnel junction array includes at least two magnetic tunnel junctions under test connected in series; and the bottom electrode of one end of the at least two magnetic tunnel junctions under test is electrically connected to the first pad, and the top electrode of the other end is electrically connected to the second pad.

8. A test method based on the test structure according to any one of claims 1 to 7, characterized in that, include: An excitation source that applies a constant current to the at least one turn of the metal coil generates a vertical magnetic field of constant magnetic field strength at the location of the magnetic storage device under test. Simultaneously, the voltage or current between the bottom electrode and the top electrode of the magnetic storage device under test is scanned to measure the relationship between the resistance of the magnetic storage device under test and the voltage under the action of the vertical magnetic field.

9. A test method based on the test structure according to any one of claims 1 to 7, characterized in that, include: An excitation source with varying current is applied to the at least one turn of the metal coil to generate a vertical magnetic field with varying magnetic field strength at the location of the magnetic storage device under test. Simultaneously, an excitation source with a set current value is applied to the bottom and top electrodes of the magnetic storage device under test to measure the relationship between the resistance of the magnetic storage device under test and the vertical magnetic field.

10. A test method based on the test structure described in any one of claims 6 to 7, characterized in that, include: An excitation source with a constant current is applied to the third and fourth pads to generate a vertical magnetic field with a constant magnetic field strength at the location of the magnetic storage device under test. Simultaneously, scanning voltages or currents of different pulse frequencies are applied between the bottom and top electrodes of the magnetic storage device under test to measure the relationship between the resistance of the magnetic storage device under test and the voltage under the action of the vertical magnetic field.

11. A test method based on the test structure according to any one of claims 1 to 7, characterized in that, include: An excitation source that applies a constant current to the at least one turn of the metal coil generates a vertical magnetic field of constant magnetic field strength at the location of the magnetic storage device under test. Under the vertical magnetic field, the magnetic storage device under test is tested through the bottom and top electrodes to obtain the required parameters of the magnetic storage device under test.

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