System and method for moke metrology with consistent mr am die orientation

Abstract

A metrology tool includes a magnet to generate a magnetic field and a stage system on an MRAM wafer to position a plurality of MRAM dies in the magnetic field. The stage system includes a chuck on which the MRAM wafer is to be mounted. The metrology tool further includes optics to provide a laser beam and direct the laser beam to be incident on a respective MRAM die positioned in the magnetic field. The metrology tool additionally includes a detector to receive the laser beam reflected by the respective MRAM die and measure a rotation of a polarization of the reflected laser beam. The metrology tool can be configured to provide a common orientation of the polarization of the laser beam relative to each MRAM die on the MRAM wafer.

Description

[0001] Related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 877,908, filed July 24, 2019, the entire contents of which are incorporated herein by reference for all purposes. Technical Field

[0003] This disclosure relates to the magneto-optical Kerr effect (MOKE), and more specifically, to MOKE metrology for characterizing magnetic random access memory (MRAM). Background Technology

[0004] The magneto-optical Kerr effect (MOKE) refers to the rotation of the polarization of light reflected from a magnetic surface. MOKE measurements can be used to characterize both continuous and patterned thin films. For example, MOKE measurements are used to characterize magnetic random access memory (MRAM) devices, where the magnetic thin film is patterned into cells. MOKE measurements can be performed before and after patterning to measure the effect of patterning on the magnetic properties of the device. MOKE measurements are also known as MOKE metrology.

[0005] Figure 1 is a schematic diagram of a MOKE measurement system 100. The MOKE measurement system 100 includes a magnet 102 having a first pole piece 104-1 and a second pole piece 104-2. The magnet 102 (which is an electromagnet) also includes corresponding conductive coils 106-1 and 106-2 wound around the pole pieces 104-1 and 104-2. A wafer 110 is positioned in the magnet between the pole pieces 104-1 and 104-2. (When the wafer 110 is positioned between the pole pieces 104-1 and 104-2, a portion of the wafer may extend laterally beyond the bottom edges of the pole pieces 104-1 and 104-2, as shown in Figure 1). The wafer 110 may be divided into multiple MRAM dies (e.g., MRAM die 302, ...). Figure 3 MRAM chips (e.g., MRAM chip 300, Figure 3 Magnet 102 generates a magnetic field (H) 108 that is normal (i.e., perpendicular) to the surface of wafer 110. If wafer 110 is an MRAM wafer, then magnetic field 108 is perpendicular to the surface of the MRAM die on the wafer.

[0006] The MOKE measurement system 100 also includes optics to provide and guide a laser beam 114 onto a wafer 110, which is positioned in a magnet between poles 104-1 and 104-2. The laser beam 114 is incident normally onto the wafer 110 (i.e., perpendicular to the surface of the wafer 110). The optics include a laser 112 for generating the laser beam 114, a polarizer 116 for polarizing the laser beam 114, and mirrors 118-1 and 118-2 for guiding the laser beam 114 onto the wafer 110. Although Figure 1 shows two mirrors 118-1 and 118-2, the number and arrangement of mirrors 118 may vary for different embodiments of the MOKE measurement system 100. For example, the laser beam 114 polarized by polarizer 116 may have a specific polarization (e.g., a specific polarization plane).

[0007] For MOKE measurements, a laser beam 114 is provided and directed onto a wafer 110, which is positioned within the magnetic field 108, when the magnet 102 generates a magnetic field 108 (e.g., when current is applied to conductive coils 106-1 and 106-2). The laser beam 114 is reflected by the wafer 110 (e.g., by the MRAM array 304 in the MRAM die 302). Figure 3 This generates a reflected laser beam 120 received by detector 122. The polarization (e.g., polarization plane) of the reflected laser beam 120 is rotated relative to the polarization (e.g., polarization plane) of the laser beam 114 due to MOKE. Detector 122 measures this rotation. Detector 122 includes an analyzer used in conjunction with polarizer 116 to measure the rotation. Various magnetic properties of interest (e.g., coercivity, saturation magnetization, exchange coupling, domain structure, spin polarization, switching curves, and / or hysteresis curves) can be determined based on these MOKE measurements.

[0008] MOKE measurement system 100 measures polar MOKE, wherein both magnetic field 108 and laser beam 114 are normal to the surface of wafer 110. Polar MOKE measurement is used to characterize MRAM devices with vertical magnetic tunneling junction (MTJ) stacks, such as spin torque transfer (STT) MRAM devices.

[0009] Figure 2 is a perspective view of a stage system 200 conventionally used for positioning a wafer 110 in magnets 102 between poles 104-1 and 104-2 (Figure 1). The stage system 200 includes a rotating chuck 202 on which the wafer 110 can be mounted. A motor 208 rotates the chuck 202 about its central axis. The central axis is the axis of rotation of the chuck 202. The chuck 202 is coupled to a translation stage 204 (largely obscured by the chuck in Figure 2) that can be moved (i.e. translated) by a motor 210 along a track 206. The stage system 200 thus has a single translation axis in the direction (i.e., parallel to the track 206) along which the chuck 202 can be translated. By combining the rotation of chuck 202 with the translation of chuck 202 along a single translation axis, different regions of wafer 110 (e.g., each die on wafer 110) are successively positioned in laser beam 114 (i.e., positioned to receive laser beam) and MOKE measurements of the regions (e.g., dies) are performed accordingly.

[0010] Figure 3 This is a hypothetical example of an MRAM wafer 300 divided into multiple MRAM dies 302. Each MRAM die 302 is a fully or partially fabricated MRAM device containing an MRAM bit cell array 304. (In...) Figure 3 In the diagram, array 304 is shown for simplicity, focusing only on a single MRAM die 302. The MRAM chip 300 can be mounted on chuck 202 (Figure 2) and positioned in the magnet 102 of the MOKE measurement system 100 between poles 104-1 and 104-2 (Figure 1). Figure 3 In this configuration, wafer 300 is positioned such that the beam spot 306 of laser beam 114 (FIG. 1) is incident on the array 304 of MRAM dies 302. The beam spot 306 may have a spot size of approximately 1 mm or substantially smaller (e.g., approximately several micrometers). By rotating chuck 202 and translating chuck 202 along a single translation axis of stage system 200 (FIG. 2), each MRAM die 302 can be continuously positioned such that the beam spot 306 is continuously incident on each MRAM die 302. Each MRAM die 302 can thereby receive and reflect the laser beam 114 when positioned in magnetic field 108 (FIG. 1), and MOKE measurements can be performed accordingly for each MRAM die 302. Summary of the Invention

[0011] Each MRAM die 302 is continuously positioned on the beam point 306 on the MRAM wafer 300 using the stage system 200 (Figure 2) and its single translation axis. Figure 3In the process, different MRAM dies 302 on the MRAM wafer 300 are given different orientations relative to the polarization (e.g., relative to the polarization plane of the laser beam 114). Therefore, the orientation of the MRAM die 302 relative to the polarization of the laser beam 114 varies depending on the position of the MRAM die 302 on the MRAM wafer 300. However, the signal-to-noise ratio (SNR) of the MOKE measurement of the MRAM die varies depending on the orientation of the MRAM die relative to the polarization of the laser beam 114. This wafer position dependence of relative orientation stems from the patterning of the magnetic film on the MRAM die to form cells, which expose portions of the underlying layer (e.g., the bottom electrode). Some relative orientations cause a sharp decrease in the SNR. For example, the SNR of some relative orientations can drop below the threshold used to perform MOKE measurements. Therefore, MOKE measurements can be limited to sampling portions of the MRAM dies on the wafer and may have more noise for some dies than others.

[0012] Therefore, there is a need for a method and system for measuring the MOKE of MRAM dies (e.g., all MRAM dies) on an MRAM wafer, wherein the dies are positioned such that they have a common orientation relative to the polarization of a laser beam used for MOKE measurement.

[0013] In some embodiments, a metrology tool includes a magnet for generating a magnetic field. The metrology tool also includes a stage system for positioning a plurality of MRAM dies on an MRAM wafer in the magnetic field. The stage system includes a chuck on which the MRAM wafer will be mounted. The metrology tool further includes optics for providing and guiding a laser beam to be incident on a respective MRAM die when the respective MRAM die on the MRAM wafer is positioned in the magnetic field. The laser beam is polarized. The metrology tool additionally includes a detector for receiving the laser beam reflected by the respective MRAM die on the MRAM wafer and measuring the rotation of the polarization of the reflected laser beam. The metrology tool can be configured to provide a common orientation of the MRAM dies relative to the polarization of the laser beam when the laser beam is incident on the MRAM die with each MRAM die on the MRAM wafer positioned in the magnetic field.

[0014] In some embodiments, a method performed in a metrology tool includes generating a magnetic field and positioning an MRAM wafer comprising a plurality of MRAM dies within the magnetic field. With the MRAM wafer positioned within the magnetic field, a laser beam is provided to be incident on the MRAM wafer. The laser beam is polarized. Respective MRAM dies on the MRAM wafer are sequentially positioned such that the laser beam is sequentially incident on the respective MRAM die while the respective MRAM die is positioned within the magnetic field. When the laser beam is incident on the MRAM die, each of the respective MRAM dies is oriented to have a common orientation relative to the polarization of the laser beam. For each of the respective MRAM dies, the rotation of the polarization of the laser beam reflected from the MRAM die is measured.

[0015] In some embodiments, a metrology tool includes a magnet for generating a magnetic field. The metrology tool also includes a stage system for positioning a plurality of MRAM dies on an MRAM wafer in the magnetic field. The stage system includes a chuck on which the MRAM wafer will be mounted. The metrology tool further includes optics for providing and guiding a laser beam to be incident on a respective MRAM die when the respective MRAM die on the MRAM wafer is positioned in the magnetic field. The laser beam is polarized. The metrology tool additionally includes a detector for receiving the laser beam reflected by the respective MRAM die on the MRAM wafer and measuring the rotation of the polarization of the reflected laser beam. The metrology tool further includes one or more processors and a memory storing one or more programs for execution by the one or more processors. The one or more programs include instructions for providing a common orientation of the MRAM die relative to the polarization of the laser beam when the laser beam is incident on the MRAM die with each MRAM die on the MRAM wafer positioned in the magnetic field. Attached Figure Description

[0016] For a better understanding of the various described implementation schemes, please refer to the following specific implementation methods in conjunction with the figures below. The figures may not be to scale.

[0017] Figure 1 is a schematic diagram of the MOKE measurement system.

[0018] Figure 2 is a perspective view of a stage system used to rotate and translate a wafer along a translation axis.

[0019] Figure 3 This is a hypothetical example of an MRAM wafer divided into multiple MRAM dies, wherein a laser beam is incident on the respective MRAM dies.

[0020] Figure 4 This is a perspective view of a stage system according to some embodiments, which rotates a wafer and translates the wafer along two translation axes.

[0021] Figure 5 This is a schematic diagram of a MOKE measurement system according to some embodiments.

[0022] Figure 6 and 7 This is an example of MOKE measurement of an MRAM array on an MRAM die.

[0023] Figure 8 This is a flowchart illustrating a method for characterizing an MRAM die using MOKE according to some embodiments.

[0024] Figure 9 This is a block diagram of the MOKE metering system according to some embodiments.

[0025] The symbols for the same components refer to the corresponding parts in the diagram and instruction manual. Detailed Implementation

[0026] Various embodiments will now be described in detail with reference to the accompanying drawings. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the various described embodiments. However, those skilled in the art will understand that the various described embodiments can be practiced without these specific details. In other examples, well-known methods, processes, components, circuits, and networks have not been described in detail to avoid unnecessarily obscuring aspects of the embodiments.

[0027] Disclosed are methods and systems for performing MOKE measurements on MRAM dies, which allow MRAM wafers (e.g., MRAM wafer 300, Figure 3 The respective MRAM dies (e.g., all MRAM dies) positioned for MOKE measurements have a common orientation (e.g., relative to the polarization plane) relative to the polarization of the laser beam used for MOKE measurements (e.g., laser beam 114, FIG. 1). Such methods and systems ensure that MOKE measurements of the respective MRAM dies can be performed using a sufficient signal-to-noise ratio. For example, such methods and systems can ensure that all MRAM dies on an MRAM wafer can be characterized (i.e., inspected) using MOKE measurements, or all MRAM dies identified as candidates for inspection on an MRAM wafer.

[0028] Figure 4 It is an MRAM wafer (e.g., MRAM wafer 300) that can be used in a MOKE measurement system to position the corresponding MRAM die (e.g., all MRAM dies) in a magnetic field (e.g., H 108, Figure 1). Figure 3A perspective view of a stage system 400 on an MRAM wafer. According to some embodiments, the stage system 400 can orient respective MRAM dies (e.g., all MRAM dies) on an MRAM wafer to have a common orientation with polarization (e.g., relative to the polarization plane) relative to a laser beam (e.g., laser beam 114, FIG. 1) of a MOKE measurement system. For example, the stage system 400 can be used in a polar MOKE measurement system (e.g., MOKE measurement system 100, FIG. 1), a longitudinal MOKE measurement system, or a transverse MOKE measurement system. The common orientation provides a signal-to-noise ratio sufficient for a predetermined MOKE measurement. The stage system 400 includes wafers (e.g., wafer 110, FIG. 1; wafer 300, etc.). Figure 3 A rotating chuck 402 can be mounted thereon. A motor 404 rotates the chuck 402 about its axis of rotation (e.g., a central axis). The chuck 402 is coupled to a first translation stage 406 movable (i.e., translated) along a track 408 by a motor 410. The first translation stage 406 is coupled to a second translation stage 412 movable (i.e., translated) along a track 414 by a motor 416. The first translation stage 406 couples the chuck 402 to the second translation stage 412. Movement of the first translation stage 406 and the second translation stage 412 respectively translates the chuck 402: movement of the first translation stage 406 translates the chuck in the direction of the track 408, and movement of the second translation stage 412 translates both the first translation stage 406 and the chuck 402 in the direction of the track 414.

[0029] The stage system 400 therefore has two translation axes: a first translation axis in the direction of track 408 (i.e., parallel to track 408), along which the first stage 406 allows the chuck 402 to translate; and a second translation axis in the direction of track 414 (i.e., parallel to track 414), along which the second stage 412 allows the first translation stage 406 and the chuck 402 to translate. A motor 410 moves the first translation stage 406 along the first translation axis. A motor 416 moves the second translation stage 412 along the second translation axis. In some embodiments, the first and second translation axes are perpendicular. For example, track 408 is perpendicular to track 414 (within manufacturing tolerances).

[0030] By mounting the MRAM wafer on chuck 402, positioning the MRAM wafer mounted on chuck 402 within the magnet of the MOKE measurement system (e.g., between poles 104-1 and 104-2 of magnet 102, FIG. 1), and performing a combination of rotating and translating chuck 402 along first and second translation axes, when a laser beam is continuously incident on the corresponding MRAM die (e.g., each MRAM die) on the MRAM wafer, the MRAM die can be continuously positioned in the magnetic field of the magnet (e.g., H 108, FIG. 1) to have a common orientation relative to the polarization of the laser beam of the MOKE measurement system. For example, common orientation can be achieved by rotating chuck 402 and thus the MRAM wafer. The corresponding MRAM die can then be continuously positioned to have a common orientation to receive the laser beam by translating chuck 402 and thus the MRAM wafer along the first and second translation axes.

[0031] Common orientation can also be achieved by rotating the optical components. Figure 5 This is a schematic diagram of a MOKE measurement system 500 according to some embodiments. The MOKE measurement system 500 includes components of a MOKE measurement system 100 (FIG. 1), wherein a laser 112, a polarizer 116, and a detector 122 are replaced by a laser 512, a polarizer 516, and a detector 522 that are rotatable about their respective longitudinal axes: the laser 512 is rotatable about its longitudinal axis 502, the polarizer 516 is rotatable about a longitudinal axis parallel to the optical path of the laser beam 514, and the detector 522 (e.g., an analyzer within the detector 522) is rotatable about a longitudinal axis parallel to the optical path of the reflected laser beam 520. In some embodiments, the laser 512 and the polarizer 516 are configured to rotate by an equal amount (e.g., rotate together). In some embodiments, the detector 522 (e.g., an analyzer within the detector 522) is configured to rotate in response to the rotation of the laser 512 and the polarizer 516. For example, detector 522 (e.g., an analyzer within detector 522) is configured to rotate by an amount equal to that of laser 512 and polarizer 516 (e.g., rotating together with laser 512 and polarizer 516).

[0032] The rotating laser 512 and polarizer 516 rotate the polarization of the laser beam 514 (e.g., rotate the polarization plane of the laser beam 514). The laser 512 and polarizer 516 are rotatable to maintain a common orientation of the polarization of the different MRAM dies relative to the laser beam 514 when performing MOKE measurements on different MRAM dies. For example, the stage system 200 (FIG. 2) can be used to sequentially position different MRAM dies 302 on the MRAM wafer 300 between a first pole piece 104-1 and a second pole piece 104-2 in the magnetic field 108, such that the laser beam 514 is sequentially incident on the different MRAM dies 302. The stage system 200 and its single translation axis allow the different MRAM dies 302 to have different absolute orientations when positioned to receive the laser beam 514 in this manner. Rotating the laser 512 and polarizer 516 allows different MRAM dies 302 to have a common orientation relative to the polarization of the laser beam 514, independent of the different absolute orientations of the different MRAM dies 302. Rotating the detector 522 (e.g., an analyzer within the detector 522) according to the rotation of the laser 512 and polarizer 516 allows the detector 522 to measure the rotation of the polarization of the reflected laser beam 520 (i.e., polarization measurement relative to the incident laser beam 514).

[0033] In other alternatives, co-orientation can be achieved by keeping the MRAM wafer stationary and moving all or part of the MOKE measurement system. For example, all or part of the magnet 102 and the optics of the MOKE measurement system 100 (FIG. 1) can be moved while the stage system on which the MRAM wafer is mounted is stationary.

[0034] Figure 6 and 7 This is an example of MOKE measurement of an MRAM array on an MRAM die. Figure 6 Demonstrates high-field, fully stacked measurements of MRAM arrays, while Figure 7 Demonstrates low-field, free-layer measurements of MRAM arrays. Figure 6 and 7 The x-axis represents the magnetic field strength (e.g., in Oe), while the y-axis represents the Kerr rotation in arbitrary units. Figure 6 In the diagram, curve 602 is for measuring increasing magnetic fields, and curve 604 is for measuring decreasing magnetic fields. Figure 7 In the figures, curve 702 is for increasing magnetic field measurements and curve 704 is for decreasing magnetic field measurements. The magnetic properties of interest can be extracted from curves 602, 604, 702, and 704 using known techniques. These types of curves can be obtained using a MOKE measurement system (e.g., MOKE measurement system 100 (Figure 1) or 500 (Figure 2)). Figure 5 ))get.

[0035] Figure 8This is a flowchart illustrating a method 800 for characterizing an MRAM die using MOKE according to some embodiments. In method 800, an MRAM die (e.g., MRAM die 300, ...) is... Figure 3 The MRAM chip is mounted (802) on a chuck. The MRAM chip comprises multiple MRAM dies (e.g., MRAM die 302, ...). Figure 3 ).

[0036] A magnetic field (804) is generated. The MRAM wafer is positioned (806) in the magnetic field. For example, the MRAM wafer is positioned between the first electrode 104-1 and the second electrode 104-2 (FIG. 1 or 5). In some embodiments, the magnetic field (e.g., H108, FIG. 1 or 5) is... Figure 5 The corresponding MRAM die is configured (808) to be normal to the MRAM wafer.

[0037] With the MRAM wafer positioned in the magnetic field, a laser beam (e.g., laser beam 114, FIG. 1; laser beam 514) is provided. Figure 5 The laser beam is incident on the MRAM wafer. The laser beam has a directional polarization. A laser (e.g., laser 112, FIG. 1; laser 512) is used. Figure 5 (812) generates the laser beam and uses a polarizer (e.g., polarizer 116, FIG. 1; polarizer 516, Figure 5 The laser beam is polarized (814) to have polarization.

[0038] The respective MRAM dies (e.g., each MRAM die on the MRAM wafer) are sequentially positioned (816) such that the laser beam is continuously incident on the respective MRAM die while it is positioned in the magnetic field. As the laser beam is incident on the MRAM die, each of the respective MRAM dies (e.g., each MRAM die on the wafer) is oriented (816) to have a common orientation relative to the polarization of the laser beam (e.g., relative to the polarization plane of the laser beam). This common orientation may be a predetermined orientation that provides a sufficient signal-to-noise ratio for MOKE measurements. The respective MRAM die reflects the laser beam.

[0039] In some embodiments, the laser beam (818) is directed to be incident normally onto the corresponding MRAM die (as shown in Figures 1 and 5, for example).

[0040] In some embodiments, continuously positioning the corresponding MRAM die includes rotating the chuck (820) and translating the chuck along a first translation axis and a second translation axis (822). For example, the chuck 402 is positioned along the stage system 400 ( Figure 4The first and second translation axes are translated. The first and second translation axes can be vertical (within manufacturing tolerances).

[0041] In some embodiments, orienting each of the respective MRAM dies to have the common orientation includes making the laser (e.g., laser 512, Figure 5 ) and the polarizer (e.g., polarizer 516, Figure 5 The laser beam is rotated (824) about its corresponding longitudinal axis to change the polarization of the incident laser beam. For example, the orientation of the MRAM die by rotating the laser and polarizer can be performed by continuously positioning the corresponding MRAM die by rotating the chuck (e.g., chuck 202, FIG. 2) and translating the chuck along a single translation axis (e.g., using stage system 200, FIG. 2).

[0042] For each of the respective MRAM dies, the rotation of the polarization (e.g., the polarization plane of the laser beam) of the laser beam reflected from the MRAM die is measured (826). Thus, a MOKE measurement is performed. In some embodiments, detector 122 (FIG. 1) or 522 ( Figure 5 It includes an analyzer for measuring the rotation of the polarization of the laser beam reflected by the MRAM die.

[0043] In some embodiments (e.g., including step 824), a detector (e.g., detector 522) is used to measure the rotation of the polarization of the laser beam reflected from the corresponding MRAM die, based on the rotation of the laser and the polarizer. Figure 5 Rotate (828).

[0044] Although method 800 includes several operations presented as occurring in a specific order, method 800 may include more or fewer operations. Some operations may be performed sequentially or in parallel. The order of two or more non-sequential dependent operations may be changed, the execution of two or more operations may overlap, and two or more operations may be combined into a single operation. For example, step 806 may include positioning the MRAM wafer in the magnet before generating the magnetic field, such that when the magnetic field is generated in step 804 (e.g., by applying current to coils 106-1 and 106-2, FIG. 1 or 5), the MRAM wafer is in the desired position.

[0045] Figure 9This is a block diagram of a MOKE metrology system 900 according to some embodiments. The MOKE metrology system 900 includes a MOKE inspection tool 930 and a computer system having one or more processors 902 (e.g., CPU), a user interface 906, a memory 910, and several communication buses 904 interconnecting these components. Alternatively, the computer system may be communicatively coupled to the MOKE inspection tool 930 via one or more networks. The computer system may further include one or more network interfaces (wired and / or wireless, not shown) for communicating with the MOKE inspection tool 930 and / or remote computer systems.

[0046] MOKE inspection tool 930 includes measurement system 932 (e.g., MOKE measurement system 100, Figure 1 or 500). Figure 5 ) and stage system 934 (e.g., stage system 200, Figure 2 or 400, Figure 4 In some embodiments, the measurement system 932 is the MOKE measurement system 100 (FIG. 1), and the stage system 934 is the stage system 400 (FIG. 100). Figure 4 In some other embodiments, the measurement system 932 is the MOKE measurement system 500. Figure 5 ), and the stage system 934 is the stage system 200 (Figure 2).

[0047] The user interface 906 may include a display 907 and one or more input devices 908 (e.g., a keyboard, mouse, touch-sensitive surface of the display 907, etc.). The display 907 may display MOKE measurement results (e.g., results from method 800). Figure 8 For example, display 907 can display... Figure 6 and 7 The type of curve shown in the image.

[0048] Memory 910 includes volatile and / or non-volatile memory. Memory 910 (e.g., non-volatile memory within memory 910) includes non-transitory computer-readable storage media. Memory 910 optionally includes one or more storage devices remotely located from processor 902 and / or non-transitory computer-readable storage media removably inserted into a computer system. In some embodiments, memory 910 (e.g., non-transitory computer-readable storage media of memory 910) stores the following modules and data, or subsets or supersets thereof: an operating system 912 including processes for handling various basic system services and for performing hardware-dependent tasks; a positioning module 914 for positioning the stage system 934 in the magnet of the measurement system 932 to have a common orientation relative to the polarization of the laser beam to receive the laser beam; a MOKE measurement module 916 for enabling the measurement system 932 to perform MOKE measurements; and a module for reporting MOKE measurement results (e.g., curves, etc.). Figure 6 and 7 (The curve in the image) (e.g., the result of method 800, Figure 8 The reporting module 918. The memory 910 (e.g., a non-transitory computer-readable storage medium) (e.g., together with the positioning module 914 and the MOKE measurement module 916) may contain a reporting module 918 for performing method 800. Figure 8 () all or part of the instructions.

[0049] Each of the modules stored in memory 910 corresponds to a set of instructions for performing one or more functions described herein. Individual modules do not need to be implemented as separate software programs. Modules and various subsets of modules can be combined or otherwise rearranged. In some embodiments, memory 910 stores a subset or superset of the modules and / or data structures identified above.

[0050] More expected Figure 9 This is a functional description of various features that can exist in the MOKE metrology system, rather than a structural diagram. For example, the functionality of the computer system in the MOKE metrology system 900 can be divided among multiple devices. Parts of the modules stored in the memory 910 can alternatively be stored in one or more other computer systems communicatively coupled to the computer system of the MOKE metrology system 900 via one or more networks.

[0051] For illustrative purposes, the foregoing description has been described with reference to specific embodiments. However, the above illustrative discussion is not intended to be exhaustive or to limit the scope of the claims to the precise form disclosed. In view of the foregoing teachings, many modifications and variations are possible. The embodiments were chosen to best illustrate the basic principles of the claims and their practical application, thereby enabling other skilled in the art to best use the embodiments with various modifications suitable for particular purposes.

Claims

1. A metrology tool comprising: a magnet to generate a magnetic field; a stage system to position a magnetic random access memory (MRAM) wafer in the magnetic field, the MRAM wafer comprising a plurality of MRAM dies, the stage system comprising: a chuck on which the MRAM wafer is to be mounted, the chuck rotatable about an axis of rotation; optics to provide a laser beam and direct the laser beam to be incident on at least one of the plurality of MRAM dies on the MRAM wafer with the MRAM wafer positioned in the magnetic field, the optics comprising: a laser to generate the laser beam, a polarizer to polarize the laser beam; and a detector to receive the laser beam reflected by the at least one of the plurality of MRAM dies on the MRAM wafer, and the detector configured to rotate in accordance with rotation of the laser and the polarizer to measure rotation of the polarization of the reflected laser beam to measure polarization relative to the incident laser beam; wherein the metrology tool is configurable to rotate the laser and the polarizer to provide a common orientation relative to the polarization of the laser beam when the laser beam is incident on another MRAM die of the plurality of MRAM dies.

2. The tool of claim 1, wherein: the chuck has an axis of rotation; the stage system has a first axis of translation and a second axis of translation; and the stage system is configured to translate the chuck along the first axis of translation and the second axis of translation and rotate the chuck about the axis of rotation to position each of the plurality of MRAM dies on the MRAM wafer to have the common orientation relative to the polarization of the laser beam.

3. The tool of claim 2, wherein the stage system further comprises: a first translation stage to which the chuck is coupled to translate the chuck along the first axis of translation; a first motor to move the first translation stage along the first axis of translation; a second translation stage to which the first translation stage is coupled to translate the chuck and the first translation stage along the second axis of translation; a second motor to move the second translation stage along the second axis of translation; and a third motor to rotate the chuck about the axis of rotation.

4. The tool of claim 2, wherein the first axis of translation and the second axis of translation are perpendicular.

5. The tool of claim 1, wherein: the magnet is configured to generate the magnetic field normal to a surface of the MRAM wafer when the MRAM wafer is positioned in the magnetic field; and the optics are configured to direct the laser beam to be normally incident on each MRAM die of the plurality of MRAM dies when each MRAM die is successively positioned to receive the laser beam.

6. The tool of claim 1, wherein: ​ The optics include a mirror to manipulate the laser beam to be incident on respective MRAM dies on the MRAM wafer; and The detector includes an analyzer.

7. A method performed in a metrology tool, comprising: generating a magnetic field; positioning a magnetic random access memory (MRAM) wafer in the magnetic field, the MRAM wafer including a plurality of MRAM dies; with the MRAM wafer positioned in the magnetic field, providing a laser beam to be incident on at least one of the plurality of MRAM dies on the MRAM wafer, wherein providing the laser beam includes generating the laser beam using a laser and polarizing the laser beam to have a polarization using a polarizer; receiving, using a detector, the laser beam reflected by the at least one of the plurality of MRAM dies on the MRAM wafer, and measuring a rotation of the polarization of the reflected laser beam by rotating the detector as a function of rotation of the laser and the polarizer to measure a polarization of the incident laser beam; continuously positioning each MRAM die of the plurality of MRAM dies on the MRAM wafer such that the laser beam, with the MRAM wafer positioned in the magnetic field, is continuously incident on each MRAM die of the plurality of MRAM dies; and rotating the laser and the polarizer to provide a common orientation with respect to the polarization of the laser beam when the laser beam is incident on each MRAM die of the plurality of MRAM dies.

8. The method of claim 7, further comprising mounting the MRAM wafer on a chuck, wherein continuously positioning each MRAM die of the plurality of MRAM dies includes: rotating the chuck; and translating the chuck along a first translational axis and along a second translational axis.

9. The method of claim 8, wherein the first translational axis and the second translational axis are perpendicular.

10. The method of claim 7, wherein: providing the laser beam includes directing the laser beam to be normally incident on each MRAM die of the plurality of MRAM dies; and generating the magnetic field includes configuring the magnetic field to be normal to each MRAM die of the plurality of MRAM dies.

11. The method of claim 7, further comprising mounting the MRAM wafer on a chuck, wherein continuously positioning each MRAM die of the plurality of MRAM dies includes: rotating the chuck; and translating the chuck along a single translational axis.

12. A metrology tool, comprising: a magnet to generate a magnetic field; a stage system to position a magnetic random access memory (MRAM) wafer in the magnetic field, the MRAM wafer including a plurality of MRAM dies, the stage system including: a chuck on which the MRAM wafer is to be mounted, the chuck rotating about a rotation axis; and a separate translation stage to which the chuck is coupled to translate the chuck along the separate translation axis; Optics to provide a laser beam and direct the laser beam to be incident on at least one of the plurality of MRAM dies on the MRAM wafer with the MRAM wafer positioned in the magnetic field, the optics comprising: a laser to generate the laser beam, a polarizer to polarize the laser beam; and a detector to receive the laser beam reflected by the at least one of the plurality of MRAM dies on the MRAM wafer and the detector configured to rotate in accordance with rotation of the laser and the polarizer to measure rotation of the polarization of the reflected laser beam to measure the polarization of the incident laser beam; one or more processors; and memory storing one or more programs for execution by the one or more processors, the one or more programs including instructions for rotating the laser and the polarizer to provide a common orientation with respect to the polarization of the laser beam when the laser beam is incident on another one of the plurality of MRAM dies.

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