Inspection Equipment

Abstract

In the present invention, high-precision inspection is done of the magnetism of each layer of two magnetic layers having different coercive forces that constitute a magnetic tunnel junction of an MRAM memory cell in a state covered by a non-magnetic material. This inspection device comprises: an NVC probe having set at the tip a diamond that has an NVC which is a complex impurity defect comprising a pair of nitrogen that has entered a carbon substitution position in a diamond lattice and a vacancy where a carbon atom adjacent to the substitutional nitrogen has disappeared; and a pulse magnetic field application means. In the present invention, an application step for applying a pulse magnetic field to a magnetic material in a sample from the pulse magnetic field application means, stopping of the application of the pulse magnetic field of the pulse magnetic field application means, and a detection step that detects the magnetic field from the magnetic material using the NVC probe are executed.

Description

[Technical Field]

[0001] The present disclosure relates to an inspection device, and more particularly to a scanning probe microscope having the function of an inspection device for inspecting magnetic memories, or a semiconductor inspection device for inspecting magnetic memories. [Background technology]

[0002] A measurement technique utilizing nitrogen-vacancy pairs (Nitrogen-Vacancy Centers: NVCs) in diamond has attracted attention. NVCs are also known as nitrogen-vacancy centers, nitrogen-vacancy centers, NV centers, or NV centers. This technique utilizes the fact that a site where carbon is replaced by nitrogen is adjacent to a vacancy in a diamond crystal, resulting in the formation of a characteristic electronic level at the vacancy position (see, for example, Patent Document 1). It is known that fine electronic levels can be utilized even at room temperature, enabling highly sensitive measurements, particularly in magnetic fields. Furthermore, by adjusting the crystal axis direction, it is possible to detect magnetic fields in three dimensions, each directional component. Scanning probe microscopes using diamond microcrystals with NVCs as probes have also been developed, and observations of magnetic domains such as skyrmions have been reported. Currently, this technique is used to investigate fundamental physical properties.

[0003] Furthermore, a spin-polarized scanning electron microscope (spin SEM) has been proposed for evaluating the magnetism of a microscopic region of 100 nm or less (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-152473 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-059057 Summary of the Invention [Problem to be solved by the invention]

[0005] Magneto-Resistive Random Access Memory (MRAM), a next-generation memory technology currently being researched and developed, utilizes the tunneling magnetoresistance effect, which is a mechanism by which the resistance between two magnetic thin films (magnetic layers) sandwiched between an insulating layer changes depending on the magnetization direction of each magnetic layer. Damage to the magnetic layer during the MRAM fabrication process, particularly during etching, is a significant issue. It is said that the development of MRAM devices could be significantly accelerated if the magnetic properties of each magnetic layer could be evaluated after etching. However, the current state of the magnetic layers in MRAM cannot be determined until the wiring for the MRAM memory cell is completed and the tunneling magnetoresistance effect is verified. Therefore, a highly accurate method for inspecting the state of the two magnetic layers in MRAM while they are covered by a non-magnetic material is desired. [Means for solving the problem]

[0006] A brief summary of representative aspects of this disclosure is as follows.

[0007] According to one aspect of the present disclosure, the inspection device includes an NVC probe, the tip of which is set with a diamond having an NVC, which is a complex impurity defect consisting of a nitrogen atom occupying a substitutional site of a carbon atom in a diamond lattice and a vacancy resulting from the removal of a carbon atom adjacent to the nitrogen atom, and a pulsed magnetic field application means. The inspection device executes an application step of applying a pulsed magnetic field from the pulsed magnetic field application means to a magnetic body in a sample, and a detection step of stopping the application of the pulsed magnetic field from the pulsed magnetic field application means and detecting the magnetic field from the magnetic body with the NVC probe. [Effects of the Invention]

[0008] According to an inspection device according to one embodiment of the present disclosure, the magnetism of each of two magnetic layers (magnetic layers) with different coercive forces that constitute the magnetic tunnel junction of an MRAM memory cell can be inspected with high precision while covered by a non-magnetic material. [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows the principle of magnetization inspection of a magnetic material covered with a non-magnetic material using an NVC probe according to an embodiment. [Figure 2] The measurement principle when a pulsed magnetic field is used in magnetic material inspection using an NVC probe according to an embodiment will be described. [Figure 3] 1 shows the overall configuration of an inspection device in a first embodiment. [Figure 4] 1 shows a flowchart of an inspection in Example 1. [Figure 5] 1 shows data obtained in the test in Example 1 and an example of analysis. [Figure 6] 1 shows an example of a display screen of the control device in Example 1. Here, a list of results at a number of inspection points is shown. [Figure 7] 1 shows an example of a display screen in the control device in Example 1. Here, an example is shown in which detailed analysis results for a small number of inspection points are displayed. [Figure 8a] 10 shows an example of a mesh when the magnetic field of an MTJ is reconstructed in the inspection device of the first embodiment, and shows an example in which the bottom surface is divided into concentric circles. [Figure 8b] 10 shows an example of a mesh when the magnetic field of an MTJ is reconstructed in the inspection device in the first embodiment, and shows an example of a sector divided at equal interior angles from the center. [Figure 8c] 8 shows an example of a mesh when the magnetic field of an MTJ is reconfigured, and shows an example in which the concentric circles in FIG. 8a are combined with sectors divided at equal interior angles from the center in FIG. 8b. [Figure 9] In the inspection device according to the second embodiment, an example of an inspection device in which a plurality of NVC probes are mounted in an array and a microwave antenna is shared by the plurality of probes will be shown. [Figure 10] 10 shows the time dependency of the power input to the pulsed magnetic field application coil and the microwave antenna in the inspection device of Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments and examples will be described with reference to the drawings. However, in the following description, the same components will be assigned the same reference numerals, and repeated description may be omitted. Note that the drawings may be more schematic than the actual embodiment to clarify the description, but they are merely examples and do not limit the interpretation of the present disclosure.

[0011] (Embodiment) FIG. 1 is a diagram showing the measurement principle of the inspection device of the present disclosure, and shows the principle of magnetization inspection of a magnetic body covered with a non-magnetic body using an NVC probe according to an embodiment.

[0012] Consider a situation in which a sample wafer 100 advances in a moving direction 102 directly below an NVC probe 101 during a manufacturing process for a memory such as a magnetoresistive random access memory (MRAM). The NVC probe 101 has a diamond tip with a nitrogen-vacancy center (NVC), which is a complex impurity defect consisting of a pair of nitrogen occupying a substitutional position for carbon in the diamond lattice and a vacancy resulting from the removal of a carbon atom adjacent to this substitutional nitrogen.

[0013] As shown enlarged in FIG. 1, two magnetic layers 10 and 11, each having a diameter of, for example, several tens of nanometers in plan view and a thickness of, for example, 1-2 nanometers in cross-sectional view, are fabricated within a wafer 100, sandwiching an insulator 12, for example, made of magnesium oxide (MgO) or the like, having a thickness of, for example, 1 nanometer. The magnetic layers 10 and 11 have different coercive forces. These layers (10, 12, 11) are referred to as a magnetic tunnel junction (MTJ) 103 of an MRAM memory cell. Since FIG. 1 illustrates a state after the etching process is completed, a nonmagnetic layer 104, for example, made of tantalum (Ta) or the like, is fabricated above the MTJ 103, having a thickness of, for example, several tens of nanometers. When this etching process is complete, the magnetization of the magnetic layers 10 and 11 of the MTJ 103 may be damaged, and if the magnetization of the magnetic layers 10 and 11 of the MTJ 103 could be inspected at this point, it would be possible to immediately inspect the etching process and verify the manufacturing conditions of the MTJ 103. However, it is currently difficult to inspect the magnetization of the magnetic layers 10 and 11 of the MTJ 103 at this point. For this reason, the current practice is to inspect the magnetization of the magnetic layers 10 and 11 of the MTJ 103 by actually testing the operation of the MRAM memory once wiring to the MRAM memory cells is complete.

[0014] For magnetic evaluation of microscopic regions of 100 nm or less, spin-polarized scanning electron microscopes (spin-SEMs) (e.g., Patent Document 2) have been used to observe recording bits on hard disks. However, this method requires a shallow probe depth of approximately 1 nm, making evaluation impossible unless the magnetic layer is exposed to the surface. In MRAM, as shown in Figure 1, a nonmagnetic layer 104 such as a Ta layer is stacked several tens of nanometers on top of the magnetic layer 11 before etching. This presents a challenge in directly observing the magnetic layers 10 and 11 using spin-SEM after etching. Furthermore, magnetic force microscopes (MFMs) detect the leakage magnetic field from the sample, so the magnetic material does not need to be exposed. However, even with this method of detecting magnetic field gradients, the signal becomes weak at a distance of several tens of nanometers from the surface of the magnetic material. Even in this case, it is still difficult to inspect the magnetization of the magnetic layers 10 and 11 of the MTJ 103.

[0015] The inspection method disclosed herein uses a probe 101 equipped with an NVC, which can quantitatively detect weak magnetic fields. The NVC probe 101, which is capable of detecting magnetic fields with high sensitivity, can detect a magnetic field (leakage magnetic field) 105 leaking from the surface of a wafer 100, even through a non-magnetic material 104 several tens of nanometers thick, as shown in FIG. 1 . One of the MTJs 103 in the MRAM wafer 100 is placed directly below the probe 101, and the magnetic field lines of the leakage magnetic field 105 leaking from the MTJ 103 are detected while the wafer 100 is moved in a moving direction 102. For example, if the MTJ 103 has a large magnetization as designed and the magnetization directions of the layers 10 and 11 are aligned (the magnetization directions are consistent) (in the case of a healthy, non-defective MTJ 103G), a large value of the leakage magnetic field 105 leaking from the surface is detected over a relatively wide area, as shown on the left side of FIG. 1 (see MTJ 103G). In contrast, as shown on the right side of Figure 1 (in the case of a defective (bad) MTJ 103N), if the magnetization of magnetic layers 10 and 11 is damaged, the range in which the leakage magnetic field 105 can be detected will be narrow and small. In the MTJ 103 shown in Figure 1, the magnetization directions from the north pole to the south pole of magnetic layers 10 and 11 are indicated by arrows 10m1, 11m1, 10m2, and 11m2. In the case of a healthy, non-defective MTJ 103G, in this example, the direction and amount of magnetization of magnetic layer 10 of MTJ 103G are indicated by four upward arrows 10m1, and the direction and amount of magnetization of magnetic layer 11 of MTJ 103G are indicated by four upward arrows 11m1. On the other hand, in the case of a defective (bad) MTJ 103N, in this example, the direction and amount of magnetization of the magnetic layer 10 of the MTJ 103N are indicated by two upward arrows 10m2, and the direction and amount of magnetization of the magnetic layer 11 of the MTJ 103N are indicated by two upward arrows 11m2. Compared to the direction and amount of magnetization of the magnetic layers 10, 11 of the MTJ 103G, the direction and amount of magnetization of the magnetic layers 10, 11 of the MTJ 103N are smaller. In particular, the magnetization of the peripheral portions of the magnetic layers 10, 11 of the MTJ 103N is smaller than that of the magnetic layers 10, 11 of the MTJ 103G, indicating that the magnetization of the peripheral portions of the magnetic layers 10, 11 of the MTJ 103N is damaged.

[0016] Graph 1G at the bottom of Figure 1 shows the relationship between the detected magnetic field MF and position P. Here, the horizontal axis represents position P, and the vertical axis represents the detected magnetic field MF perpendicular to the surface of the sample. Since the shape of the graph (the shape of the detected magnetic field EF) differs for a healthy, non-defective MTJ 103G and a damaged, defective (bad) MTJ 103N, accurate measurement of this leakage magnetic field 105 using NVC probe 101 makes it possible to relatively accurately inspect whether the magnetic layers 10 and 11 constituting the MRAM MTJ 103 are good or bad.

[0017] FIG. 2 is a diagram for explaining the importance of a pulsed magnetic field in the present disclosure, and shows the measurement principle when a pulsed magnetic field is used in magnetic material inspection using an NVC probe according to an embodiment.

[0018] Of the two magnetic layers 10 and 11 of the MTJ 103, one magnetic layer 10, called the pinned layer 206, is adjacent to the other magnetic layer 11, so that the magnetization direction of the pinned layer 206 is firmly fixed in a predetermined direction (in this example, upward magnetization from the north pole to the south pole) and is fixed so that it will not reverse unless an external magnetic field of 1 T is applied. The other magnetic layer 11, called the free layer 207, is provided with an insulating layer 208 made of MgO or the like between the magnetic layer 10 and the free layer 207, and its magnetization reverses in an external magnetic field of about 0.1 T. By applying a pulse magnetic field of about 0.1 to 1 T before measurement, the magnetization direction of the free layer 207 can be controlled (in this example, the magnetization direction of the free layer 207 is changed from upward to downward), allowing the magnetization of the two magnetic layers 10 and 11 to be tested individually.

[0019] 2, first, a large pulse magnetic field is applied to magnetic layers 10 and 11 using pulse magnetic field application coil 209 so as to orient the magnetizations of free layer 207 and fixed layer 206 in the same direction (in this example, magnetization direction 10m of magnetic layer 10 and magnetization direction 11m of magnetic layer 11 are both upward magnetization directions), as shown in first pulse magnetic field application process (first application step) PMF1 in Fig. 2. After the pulse magnetic field is applied by first pulse magnetic field application process PMF1, a large magnetic field is detected when leakage magnetic field 205 on wafer 100 is measured (first inspection step MEG1).

[0020] Then, as shown in FIG. 2, a pulsed magnetic field corresponding to the magnitude between the coercive forces of the pinned layer 206 and the free layer 207 is applied in the opposite direction. This reverses the magnetization of the free layer 207 (the magnetization direction 11m of the magnetic layer 11 is reversed and becomes downward), pointing in the opposite direction to that of the pinned layer 206 (the magnetization direction 10m of the magnetic layer 10 and the magnetization direction 11m of the magnetic layer 11 become opposite). A similar measurement is then performed (second inspection step MEG2). If the magnetizations of the two magnetic layers 10 and 11 are normal, they will cancel each other out, and the leakage magnetic field 205 from the surface of the wafer 100 will be nearly zero. The first pulsed magnetic field application process PMF1 and the second pulsed magnetic field application process PMF2 can be considered together as an application step. Additionally, the first inspection step MEG1 and the second inspection step MEG2 can be considered together as a detection step.

[0021] In the measurement of the second pulse magnetic field application step PMF2, if the magnetization of the free layer 207 is damaged and reduced, the magnetization of the fixed layer 206 will exceed the magnetization of the free layer 207, and a slight leakage magnetic field 205 will be detected, which will be in the same direction as the leakage magnetic field measured the first time (after application of the first pulse magnetic field application step PMF1). Conversely, if the magnetization of the fixed layer 206 is damaged, the reversed magnetization of the free layer 207 will exceed the magnetization of the fixed layer 206, and a leakage magnetic field 205 will be detected that is in the opposite direction to the leakage magnetic field measured the first time (after application of the first pulse magnetic field application step PMF1).

[0022] In this way, by measuring the output magnetic field when the magnetizations of the two magnetic layers 10 and 11 are in a parallel state (the state before the magnetization of the free layer 207 changes) or an antiparallel state (the state after the magnetization of the free layer 207 changes) due to two pulse magnetic field applications (first pulse magnetic field application process PMF1 and second pulse magnetic field application process PMF2), and comparing the two measurement results, it is possible to accurately inspect the soundness of the magnetization of each of the two magnetic layers 10 and 11. In other words, it is possible to construct an inspection device system that can comprehensively inspect the magnitude, stability, ease of writing, etc. of the magnetization of the two magnetic layers 10 and 11. Therefore, it is possible to inspect the magnetism of each of the two magnetic layers (magnetic layers 10 and 11) with different coercive forces that constitute the magnetic tunnel junction of an MRAM memory cell with high precision while covered by a nonmagnetic material (nonmagnetic layer 104). [Example]

[0023] An example of the present invention will be described below.

[0024] FIG. 3 is a diagram showing the overall configuration of the inspection apparatus according to the first embodiment, illustrating a portion of a semiconductor manufacturing system incorporating an inspection apparatus equipped with the inspection function disclosed in this embodiment. A fully etched MRAM wafer 301 (100) is loaded onto a transfer holder 302 from a transfer chamber 300. The wafer 301 is then transported to an evaluation chamber 303. The evaluation chamber 303 is equipped with an inspection apparatus DIG. The inspection apparatus DIG is equipped with a pulsed magnetic field application coil 304 (209), a green laser beam irradiator, an objective lens 305 for collecting red fluorescence, a microwave irradiation antenna 306, an NVC probe 101 equipped with an NVC, and a probe holder 307. The wafer 301 is then moved by a drive stage 308, and two magnetic layers 10 and 11 are placed directly below the NVC probe 101 for inspection. Installing multiple NVC probes 101 and probe holders 307 in the inspection apparatus DIG can improve inspection throughput. The inspection device DIG further includes a driving stage control device 309, a green band laser light source 310, a red band fluorescence detector 311, and a control system (control device) 312, and the driving stage control device 309, the green band laser light source 310, and the red band fluorescence detector 311 are controlled by the control system (control device) 312 to perform the inspection. After the inspection is completed, the wafer 301 and the transfer holder 302 are transferred to another transfer chamber 313 for the next process.

[0025] That is, a scanning probe microscope as an inspection device DIG having an NVC probe 101 processed into a probe shape is incorporated into a part of a semiconductor manufacturing system. The scanning probe microscope as the inspection device DIG includes a sample stage (sample mounting table, drive stage) 308 on which a sample (wafer 301 (100)) having a magnetic material (magnetic tunnel junction: MTJ 103) consisting of two layers of magnetic materials 10 and 11 with different coercive forces fabricated by a semiconductor fabrication process is placed and set, a microwave irradiation antenna 306 that irradiates microwaves to the NVC probe 101, a green laser light source 310 that emits a green laser to irradiate the NVC probe 101, a red fluorescence detector 311 that detects red fluorescence from the NVC probe 101, a pulsed magnetic field application coil 304 (209) that applies a pulsed magnetic field to the sample 100, a pulsed magnetic field generator (not shown) that generates a pulsed magnetic field to be applied to the pulsed magnetic field application coil 304 (209), and a microwave generator (not shown) that generates microwaves to be applied to the microwave irradiation antenna 306. The inspection device DIG measures the leakage magnetic field on the surface of the sample 100 immediately after each pulse magnetic field application (first pulse magnetic field application process PMF1, second pulse magnetic field application process PMF2) in the measurement data of the leakage magnetic field, and inspects the magnetism of each magnetic layer 10, 11 of the sample 100 by multiple measurements in which multiple pulse magnetic fields are applied under different conditions.

[0026] A flowchart of the inspection process in the evaluation chamber 303 will be described with reference to Fig. 4. Fig. 4 shows a flowchart of the inspection in Example 1. Each step (401-410) shown in Fig. 4 will be described.

[0027] 401: First, the wafer (sample) 301 is set on the driving stage 308 of the evaluation chamber 303. The driving stage 308 moves the wafer 301 to a position directly below the probe 101 in an inspection area to be inspected.

[0028] 402: Then, the probe 101 is brought close to the surface of the sample 301.

[0029] 403: Then, a measurement system capable of detecting green band laser irradiation and red band fluorescence is confirmed.

[0030] 404: After that, the microwave antenna 306 is operated by the microwave generator, and the probe 101 is irradiated with microwaves.

[0031] 405: Then, the pulsed magnetic field generator drives the pulsed magnetic field application coil 304 (209), and the pulsed magnetic field application coil 304 (209) applies a pulsed magnetic field in the positive direction to the inspection area of ​​the wafer 301 (first pulsed magnetic field application step PMF1). While an example of pulsed magnetic field application using the pulsed magnetic field application coil 304 is described here, a method of bringing a magnet containing an iron core close to the wafer 301 is also acceptable. Alternatively, a method of bringing a permanent magnetic material close to the wafer 301 is also acceptable. In this case, to individually control the magnetization of the two magnetic layers 10 and 11, it is preferable to prepare two or more types of permanent magnets with different output magnetic fields and polarities, such as by using different materials. In this process, a magnetic field of several hundred mT is applied to orient the magnetization of both the fixed layer 206 (10) and the free layer 207 (11) in the same direction.

[0032] 406: After that, the magnetic field applied to the wafer 301 is returned to zero, and the NVC probe 101 is scanned over the inspection area to acquire the first inspection data (first inspection step). At this time, the wafer 301 is slightly moved while the NVC probe 101 detects the magnetic field 205 leaking from the two magnetic layers 10 and 11 in the MRAM. The inspection data can be acquired by creating a magnetic field distribution image using two-dimensional mapping, creating a magnetic field distribution line using one-dimensional mapping, or by single-point inspection of the magnetic field magnitude using point analysis. The data acquisition method also affects the inspection throughput.

[0033] 407: After acquiring the first test data, the pulsed magnetic field generator drives the pulsed magnetic field application coil 304 (209) to apply a pulsed magnetic field in the negative direction from the pulsed magnetic field application coil 304 (209) to the test area of ​​the wafer 301 (second pulsed magnetic field application step PMF2). In this case, the magnetic field reverses only the direction of magnetization of the free layer 207 (11).

[0034] 408: Thereafter, the magnetic field applied to the wafer 301 is returned to zero, and the inspection area is scanned again with the NVC probe 101 to obtain second inspection data (second inspection step).

[0035] 409: The magnetization of the two magnetic layers 10 and 11 is inspected by comparing and analyzing the test data obtained two times with the pulse magnetic field application (405, 407) sandwiched therebetween.

[0036] 410: After the inspection is completed, the probe 101 is separated from the sample 301, and the driving stage 308 moves another inspection area of ​​the wafer 301 to directly below the probe 101. In this way, the magnetization of the MTJs on the wafer 301 is inspected sequentially. After inspection of all the inspection target areas on the wafer 301 is completed, the wafer 301 is moved to another chamber.

[0037] Next, an example of the acquired data and its display method will be described using FIG. 5. FIG. 5 shows an example of the data acquired in the test in Example 1 and an analysis example. As shown in the upper right corner of the table, the magnitude of the magnetic field detected by the probe or the magnitude of the magnetization of each layer is displayed in gray scale, with the positive direction indicated by black and the negative direction indicated by white. Here, it is assumed that the probe 101 detects the magnetic field perpendicular to the surface of the sample 301 (100) and the leakage magnetic field 205 (105) is two-dimensionally mapped. FIG. 5 shows the magnetization state of each magnetic layer 206, 207 of the pinned layer 206 and free layer 207 of the circular MTJ 103, reconstructed and displayed for each layer, when viewed from above. When a positive pulse magnetic field is applied (first inspection step MEG1 after first pulse magnetic field application process PMF1), measurement data (A) indicates that the magnetization of the fixed layer 206 and the free layer 207 is oriented in the same direction. However, in the inspection region RE1, a concentric magnetic field is detected, with the magnetic field being greatest in the center and gradually decreasing. When a negative pulse magnetic field is applied (second inspection step MEG2 after second pulse magnetic field application process PMF2), measurement data (B) indicates that the magnetization of the fixed layer 206 and the free layer 207 is oriented in opposite directions, canceling each other's output magnetic fields. However, the leakage magnetic field is also almost zero. By performing magnetization reconstruction calculations for each layer based on the measurement conditions and the shape of the MTJ 103 using the measurement data (A) and (B), it is assumed that both the fixed layer 206 and the free layer 207 retain healthy magnetization. As a result, the RES evaluation for inspection region RE1 is good (○) for both the fixed layer 206 and the free layer 207. Here, as a very rough idea, the magnetization (C) of the pinned layer 206 can be calculated based on the sum of the measurement data of (A) and (B), such as C = (A + B) / 2. Also, the magnetization (D) of the free layer 207 can be calculated based on the difference between the measurement data of (A) and (B), such as C = (AB) / 2. In detail, the magnetization of each layer should be calculated using a reconstruction simulation or the like.

[0038] In addition, in the measurement data for the test area RE2 (A), a circular magnetic field is detected that is maximum in the center and gradually decreases, similar to the case for the test area RE1. However, the magnitude of the magnetic field is slightly smaller than that of the test area RE1. On the other hand, in the measurement data for (B), the magnetic field value is almost zero in the center, but a slight positive magnetic field is detected at the periphery of the circle. In other words, in the measurement data for (B), the magnetizations of the pinned layer 206 and the free layer 207 should be in opposite directions and should be canceled, but they are not canceled at the periphery. Since the stray magnetic field is in the positive direction (positive magnetic field PMF), it can be seen that the magnetization of the pinned layer 206 is detected. In other words, it can be inferred that the magnetization of the pinned layer 206 is not sufficiently large at the periphery of the free layer 207, and therefore cannot be canceled. The table shows the magnetizations of the pinned layer 206 and the free layer 207 actually reproduced using a reconstruction program. The resulting RES results show that the pinned layer 206 is good (○) and the free layer 207 is bad (×).

[0039] Furthermore, in the measurement data for the inspection area RE3 (A), a circular magnetic field was detected that was maximum in the center and gradually decreased, similar to the case for the inspection area RE2, and its magnitude was slightly smaller than that of the inspection area RE1. On the other hand, in the measurement data for (B), a slight negative magnetic field was detected in the center of the circle. This indicates that in (B), where the magnetizations of the pinned layer 206 and the free layer 207 are in opposite directions and should be canceled, they are not canceled. Instead, they are in the negative direction (negative magnetic field NMF), and the magnetization of the free layer 207 is detected. In other words, it can be inferred that the pinned layer 206 does not have sufficient magnetization, and the magnetization of the free layer 207 cannot be canceled. The table shows the magnetizations of the pinned layer 206 and the free layer 207 actually reproduced using a reconstruction program. As a result, the pinned layer is marked as poor (×) and the free layer is marked as good (○) in RES. By performing two measurements of the measurement data (A) and the measurement data (B) as described above and analyzing them, it is possible to accurately inspect the magnetizations of the fixed layer 206 and the free layer 207.

[0040] Moreover, by performing such an inspection multiple times at the same location at time intervals after application of the pulsed magnetic field, it is possible to evaluate the stability of the MTJ 103. In particular, in the second inspection step MEG2, the magnetizations of the fixed layer 206 and the free layer 207 are expected to become antiparallel, which is likely to cause energetic instability, and therefore it is expected that a stability inspection to confirm that the results do not change over time will be important.

[0041] An example of a display on the display screen DP of the control device 312 according to the first embodiment will be described with reference to Figs. 6 and 7. Fig. 6 shows an example of a display screen on the control device in the first embodiment. Here, a list of results at a large number of inspection points is shown. Fig. 7 shows an example of a display screen on the control device in the first embodiment. Here, an example of displaying detailed analysis results at a small number of inspection points is shown.

[0042] The top layer of the menu 60 on the left side of the display screen DP of the control device 312 includes a "Sample Setting" menu 61 for transporting the sample 301 and selecting the inspection position; a "Pulse Magnetic Field Setting" menu 62 for setting the magnitude and duration of the pulsed magnetic field applied before observation; a "Microwave Setting" menu 63 for setting the intensity of the microwave irradiated to the NVC probe 101 and issuing an ON / OFF command; a "Scanning Condition Setting" menu 64 for setting whether the magnetic field detection by the NVC probe 101 is to be performed in two dimensions, one dimension, or point analysis, as well as the time period, and issuing a measurement start / stop command; and a "Result Display" menu 65 for displaying the progress and results of the inspection and analysis results. A diagram 66 is displayed in the lower left corner, showing which part of the entire wafer 301 is designated as the inspection position 68. The center of Figure 6 displays a list of evaluation points 67 from the "Result Display" menu. Here, coordinates are defined on the wafer 301 in two dimensions, with numbers along the vertical axis and letters along the horizontal axis, and the inspection results for each point are displayed. In this table, most of the results are judged to be good (○), but there are some defective (×) areas in the lower right corner. Clicking on this X will display a more detailed view of whether the defective area is the free layer 206 or the fixed layer 207, or which part is defective. Figure 7 shows an example of the 2D analysis results that are displayed in this case. As an example, the inspection results for the magnetization of the free layer 206 or the fixed layer 207 at coordinates 5H and 6H are displayed here.

[0043] When evaluating such acquired data, it is effective in shortening analysis time to create a database in advance of several data patterns that indicate good and bad products and determine whether or not the product matches this.If the pattern does not match the database, calculations can be performed to reconstruct the magnetization of the MTJ 103 based on the acquired magnetic field data.

[0044] 8a, 8b, and 8c show examples of how to create a mesh when performing a reconstruction calculation. FIG. 8a shows an example of a mesh when the magnetic field of an MTJ is reconstructed in the inspection device of Example 1, and shows an example in which the bottom surface is divided into concentric circles. FIG. 8b shows an example of a mesh when the magnetic field of an MTJ is reconstructed in the inspection device of Example 1, and shows an example in which the mesh is divided into sectors divided at equal interior angles from the center. FIG. 8c shows an example of a mesh when the magnetic field of an MTJ is reconstructed, and shows an example in which the concentric circles of FIG. 8a and the sectors divided at equal interior angles from the center of FIG. 8b are combined.

[0045] For example, one possible method is to divide the circular bottom surface of the MTJ 103 into concentric circles (Figure 8a), or to divide the bottom surface of the MTJ 103 into sectors with equal interior angles from the center (Figure 8b). A division method that combines the concentric circles of Figure 8a and the sectors of Figure 8b, with equal interior angles from the center, is also possible. By dividing the area into smaller areas in this way, the inspection results for each area can be displayed. This allows for immediate inspection of the etching process, verification of the MTJ 103 fabrication conditions, and feedback to the fabrication conditions. [Example]

[0046] Example 2 will be described with reference to Fig. 9. Fig. 9 shows an example of an inspection device in Example 2 in which a plurality of NVC probes are mounted in an array and a microwave antenna is shared by the plurality of probes.

[0047] Here, in order to increase the throughput of the inspection, an inspection device DIG1 is shown that can simultaneously inspect a plurality of MTJs 103 formed at different locations on the same (single) wafer 901 (100) using a plurality of NVC probes 101. The inspection device DIG1 has a transfer stage 900, a probe array 902, a microwave antenna 903, a green band laser light source 904, a pulsed magnetic field application coil 905, and a red band fluorescence detector 907.

[0048] A wafer 901 mounted on a transfer stage 900 is moved directly below the probe array 902. In this embodiment, the microwave antenna 903 has a length equivalent to the diameter Di of the wafer 901 so that microwaves can be applied to multiple NVC probes 101 simultaneously. The green laser light source 904 is also capable of applying green laser light to multiple NVC probes 101 simultaneously. Meanwhile, a red fluorescence detector 907, which is a detection system for red fluorescence 905, is provided for each NVC probe 101, allowing inspection of each MTJ 103 individually. The red fluorescence detector 907 can also be replaced by a device such as a camera. Furthermore, a microwave antenna 903 and a pulsed magnetic field application coil 906 are provided. In FIG. 9, multiple probes 101 are equipped with one microwave antenna 903, and each probe 101 is equipped with one pulsed magnetic field application coil 906. However, these may be provided one for each probe or shared by multiple probes. 9, by mounting multiple NVC probes 101 and inspection channels (903, 906, 907), it becomes possible to inspect many MTJs 103 in a short time. In other words, the time required to acquire inspection data for all MTJs 103 on one wafer 901 can be shortened.

[0049] It is also expected that the characteristics of each NVC probe 101 will differ, so before actually measuring the MTJ 103, it is desirable to inspect the characteristics of each NVC probe 101, particularly its responsiveness to magnetic fields, and organize this data into a database before starting the actual measurement. [Example]

[0050] Fig. 10 shows the time dependence of the power input to the pulsed magnetic field application coil and microwave antenna in the inspection device of Example 3. Fig. 10 shows a graph in which the vertical axis represents the power Pw input to the pulsed magnetic field application coil (209, 304, 906) and microwave antenna (306, 903) of the inspection device (DIG, DIG1) in Figs. 3 and 9, and the horizontal axis represents time t. Below, the operation of the pulsed magnetic field application coil 304 and microwave antenna 306 will be explained as representative examples.

[0051] First, power is supplied from a microwave generator MWGEN (not shown) to the microwave antenna 306. The microwaves irradiated from the microwave antenna 306 to the NVC probe 101 have an intensity at a level that irradiates an AC magnetic field of about 1 mT onto the NVC probe 101. These microwaves are then continuously irradiated until the end of the measurement.

[0052] Then, just before the first measurement MEG1, a large current is passed from the pulsed magnetic field generator PLGEN (not shown) to the pulsed magnetic field application coil 304 for a short time to control the magnetization orientation of the fixed layer 206 and the free layer 207 in the MTJ 103 (first pulsed magnetic field application step PMF1). Here, for example, a magnetic field of 0.1 T or more (>0.1 T) is generated. During the subsequent measurement MEG1 by the NVC probe 101, no power is applied to the pulsed magnetic field application coil 304, while the microwave antenna 306 continues to irradiate the NVC probe 101 with microwaves. After the first measurement MEG1 is completed, as preprocessing for the second measurement MEG2, the pulsed magnetic field generator PLGEN briefly applies power to the pulsed magnetic field application coil 304 to generate a magnetic field of the opposite polarity (e.g., -0.1 T) to change the magnetization of the free layer 207 of the MTJ 103 (second pulsed magnetic field application step PMF2). Thereafter, the second measurement MEG2 is started for the NVC probe 101. Again, during this measurement MEG2, no power is supplied to the pulsed magnetic field application coil 304, and the microwave antenna 306 continues to irradiate the NVC probe 101 with microwaves. These two measurements (MEG1 and MEG2) complete the inspection of the magnetization of the fixed layer 206 and free layer 207 of one MTJ 103 pair.

[0053] The disclosure made by the inventor has been specifically described above based on examples, but it goes without saying that the present disclosure is not limited to the above-described embodiments and examples, and various modifications are possible. [Explanation of symbols]

[0054] 100: wafer, 101: NVC, 102: movement direction, 103: magnetic tunnel junction (MTJ), 104: non-magnetic layer, 105: leakage magnetic field, 200: wafer, 201: NVC, 202: movement direction, 203: magnetic tunnel junction (MTJ) MTJ), 204: non-magnetic layer, 205: leakage magnetic field, 206: fixed layer, 207: free layer, 208: insulating layer, 209: magnetic field application coil, 300: transfer chamber, 301: wafer, 302: transfer holder, 303: evaluation chamber, 304: pulsed magnetic field application coil, 305: objective lens, 306: microwave irradiation antenna, 307: probe and probe holder equipped with NVC, 308: drive stage, 309: drive stage control device, 310: green band laser light source, 311: red band fluorescence detector, 312: control system, 900: transfer stage, 901: wafer, 902: probe array, 903: microwave antenna, 904: green band laser light source, 905: red band fluorescence, 906: pulsed magnetic field application coil, 907: red band fluorescence detector

Claims

1. an NVC probe with a diamond at its tip having an NVC, which is a complex impurity defect consisting of a nitrogen atom occupying a substitutional position of carbon in the diamond lattice and a vacancy resulting from the removal of a carbon atom adjacent to the nitrogen atom; a pulse magnetic field applying means, an application step of applying a pulsed magnetic field from the pulsed magnetic field application means to a magnetic body in the sample; a detection step of stopping the application of the pulsed magnetic field by the pulsed magnetic field application means and detecting a magnetic field from the magnetic body by the NVC probe; the magnetic material has a plurality of layers, and the plurality of layers are two magnetic layers that form a magnetic tunnel junction, the upper surface of which is covered with a non-magnetic material; The inspection device is characterized in that the pulse magnetic field applying means applies a magnetic field that changes the magnetization state of one of the two magnetic layers.

2. 2. The inspection device according to claim 1, The detecting step An inspection device characterized by inspecting the magnetization of one of the magnetic layers using measurement data of a magnetic field detected before a change in the magnetization of the one of the magnetic layers and measurement data of a magnetic field detected after a change in the magnetization of the one of the magnetic layers.

3. 3. The inspection device according to claim 2, The applying step a first applying step of applying the pulse magnetic field from the pulse magnetic field applying means to the two magnetic layers so as to make the magnetization directions of the two magnetic layers coincide with each other; a second applying step of applying a pulsed magnetic field from the pulsed magnetic field applying means to the two magnetic layers by changing the direction and magnitude of the pulsed magnetic field applied in the first applying step so as to change the magnetization of one of the magnetic layers, The detecting step a first inspection step of measuring a magnetic field from the two magnetic layers by the NVC probe after the first application step; a second inspection step of measuring the magnetic field from the two magnetic layers by the NVC probe after the second application step; An inspection device characterized in that the magnetization of each layer of the two magnetic layers is inspected by analyzing the first measurement data obtained by the first inspection step and the second measurement data obtained by the second inspection step.

4. 4. The inspection device according to claim 3, An inspection device characterized by calculating the sum and difference of the first measurement data obtained in the first inspection step and the second measurement data obtained in the second inspection step, thereby reconstructing and displaying the magnetization of each layer of the two magnetic layers for each layer.

5. 5. The inspection device according to claim 1, A plurality of the NVC probes are provided; Further, a red band fluorescence detector is provided, the sample is a wafer including a plurality of the magnetic tunnel junctions; an inspection apparatus, wherein in the detecting step, a plurality of the magnetic tunnel junctions formed at different positions on the same wafer are inspected using a plurality of the NVC probes and the red band fluorescence detector.

6. 6. The inspection device according to claim 5, Further, a microwave antenna is included which irradiates microwaves onto the plurality of NVC probes, An inspection device characterized in that, in the detection step, measurement is performed while irradiating the microwave from the microwave antenna to the plurality of NVC probes.

7. 7. The inspection device according to claim 6, the pulsed magnetic field applying means includes one pulsed magnetic field applying coil, The inspection device is characterized in that the pulse magnetic field application coil controls the magnetization of the two magnetic layers that constitute each of the plurality of magnetic tunnel junctions formed at different locations on the wafer.

8. 8. The inspection device according to claim 7, Further, a green band laser light source is provided for irradiating the plurality of NVC probes with a green band laser, In the detection step, the green band laser is irradiated onto the plurality of NVC probes from the green band laser light source, and red band fluorescence generated from the plurality of NVC probes is detected by the red band fluorescence detector, thereby measuring the magnetization of the two magnetic layers.

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