Optics for in-situ scanning electron microscopy restoration

Abstract

The device is introduced into the scanning electron microscope (SEM) via a load lock and placed on the SEM stage. The device includes a substrate and an optical system mechanically coupled to the substrate to direct light upwards, away from the substrate. With the device on the SEM stage, the optical system is used to direct light upwards through the SEM aperture, illuminating the electron detector within the SEM.

Description

Technical Field

[0001] Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 538,071, filed September 13, 2023, which is hereby incorporated by reference in its entirety for all purposes. The present disclosure relates to scanning electron microscopes (SEMs), and more specifically to optical systems used in-situ to repair SEMs.

Background Art

[0002] An SEM includes an electron detector that detects electrons scattered from a target to be imaged. The electron detector may sometimes be referred to as an electron detection device (EDD). The electron detector may be implemented as a reverse-biased diode. During SEM operation, charge trapping occurs in the electron detector, resulting in a loss of detector bandwidth and thus a reduction in the imaging capability of the SEM. An SEM with degraded electron detector bandwidth can be repaired by replacing the entire subsystem (field-replaceable unit or FRU) within the SEM that includes the electron detector. This approach is costly, labor-intensive, and causes significant downtime of the SEM. Another approach is to reverse electron-detector bandwidth degradation through high-temperature processing, which is also labor-intensive and suffers from significant downtime.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, more practical techniques are needed to restore lost electron detector bandwidth. In particular, it is desirable to repair the electron detector in situ without destroying the vacuum of the SEM. [Means for solving the problem]

[0005] In some embodiments, the device includes a substrate and also includes an optical system mechanically coupled to the substrate to direct light upward into the aperture of the SEM, away from the substrate. The device is loadable into the SEM and can be removed from the SEM via the SEM's load lock.

[0006] In some embodiments, the method includes loading the device onto the SEM stage through the SEM load lock. The device includes a substrate and an optical system mechanically coupled to the substrate to direct light upward away from the substrate. The method also includes using the device on the SEM stage to direct light upward through the SEM aperture onto an electron detector in the SEM using the optical system.

[0007] This apparatus and method can be used to perform in-situ maintenance on an electron detector to recover lost bandwidth, and can also be used for testing an electron detector in situ. [Brief explanation of the drawing]

[0008] To better understand the various implementation configurations described, please refer to the following detailed explanations in conjunction with the diagrams below. [Figure 1] This is a cross-sectional view of a device, according to several embodiments, that includes a light source, lens, and mirror, placed in a container and mounted on a stage within the vacuum chamber of a scanning electron microscope (SEM) to illuminate an electron detector within the SEM. [Figure 2]This is a cross-sectional view of a device, according to several embodiments, that includes a substrate-mounted light source, lens, and mirror, loaded onto a stage in the vacuum chamber of a scanning electron microscope (SEM) to illuminate an electron detector within the SEM. [Figure 3] The insertion of the apparatus shown in Figure 1 into the SEM via the load lock of the SEM is shown in several embodiments. [Figure 4] The insertion of the apparatus shown in Figure 2 into the SEM via the SEM's load lock is shown in several embodiments. [Figure 5] This is a cross-sectional view of a device, according to several embodiments, that includes a lens and mirror, which are housed in a container and omit a light source, and are mounted on a stage within the vacuum chamber of a scanning electron microscope (SEM) to illuminate an electron detector within the SEM. [Figure 6] This is a cross-sectional view of a device, according to several embodiments, that includes a substrate-mounted lens and mirror, without a light source, loaded on a stage within the vacuum chamber of a scanning electron microscope (SEM) to illuminate an electron detector within the SEM. [Figure 7] The insertion of the apparatus shown in Figure 5 or Figure 6 into the SEM via the load lock of the SEM is shown according to several embodiments. [Figure 8] This is a block diagram showing the components of an example of the apparatus shown in Figure 1 or Figure 2, according to several embodiments. [Figure 9] This is a block diagram showing components of another example of the apparatus in Figure 1 or Figure 2, according to several embodiments. [Figure 10] This flowchart shows methods for illuminating an electron detector in a scanning electron microscope (SEM) according to several embodiments. Similar reference numerals refer to corresponding parts throughout the drawings and specification. [Modes for carrying out the invention]

[0009] Herein, various embodiments are given in detail, examples of which are shown in the accompanying drawings. In the following detailed description, numerous specific details are given in order to provide a complete understanding of the various embodiments described. However, it will be apparent to those skilled in the art that the various embodiments described can be carried out without these specific details. In other examples, well-known methods, procedures, components, circuits, and networks are not described in detail so as not to unnecessarily obscure the aspects of the embodiments.

[0010] Bandwidth degradation in an electron detector in a scanning electron microscope (SEM) can be reversed in situ by illuminating the electron detector. The electron detector can be illuminated using a device loaded into the SEM via a load lock. Therefore, the electron detector can be repaired without disrupting the vacuum within the SEM and without replacing the SEM subsystem containing the electron detector. Illumination of the electron detector may also be performed to test its functionality with light.

[0011] Figure 1 is a cross-sectional view of a device 100 used to irradiate an electron detector 124 in a SEM, according to several embodiments. In Figure 1, the device 100 is loaded onto a stage 126 in the vacuum chamber 128 of the SEM. During normal operation of the SEM, targets may be loaded onto the stage 126 for imaging. In some embodiments, these targets are reticles (i.e., photomasks) used to manufacture semiconductor wafers. The SEM may be configured and used to image the reticle (for example, to inspect the reticle for defects and / or to image defects identified on the inspected reticle). However, the device 100 is not used during normal operation, but instead is used to perform maintenance on the SEM and / or to test the SEM.

[0012] The apparatus 100 includes a container 102, a light source 108, a lens 110, and a mirror 114. The light source 108, lens 110, and mirror 114 are arranged inside the container 102. In some embodiments, the light source 108 is a laser (e.g., a laser diode) or a light-emitting diode (LED), the lens 110 is arranged inside an optical component 112 (e.g., a collimator which may be an optical fiber collimator) inside the container 102, and / or the mirror 114 is a right-angle prism mirror. For example, the light source 108 may be a Thorlabs L375P70MLD laser diode, the optical system 112 may be an Edmund Optics #88-173 optical fiber collimator, and the mirror 114 may be a Thorlabs MRA05-F01 right-angle prism mirror.

[0013] The container 102 is either reticle-shaped or otherwise shaped in such a way that it can be loaded into the SEM (e.g., into the SEM configured and used to image the reticle) and onto the stage 126. The container 102 has a bottom surface that serves as a substrate 104 to which the light source 108, lens 110, and mirror 114 are directly or indirectly mechanically coupled. For example, the optical components 112, including the light source 108, mirror 114, and / or lens 110, may be fixed to the substrate 104 and thus directly mechanically coupled. In another example, the light source 108, optical components 112, and / or mirror 114 may be fixed to one or more sides of the container 102 and thus indirectly mechanically coupled to the substrate 104, as the sides of the container 102 are connected to the substrate 104 (i.e., up to the bottom surface of the container 102).

[0014] The optical component 112 and the mirror 114, and thus the lens 110 and the mirror 114, are disposed within the container 102 and entirely or partially constitute an optical system that is mechanically coupled directly or indirectly to the substrate 104. These optical systems direct light 116 upward away from the substrate 104, into the aperture 120 in the SEM, and onto the electron detector 124 in the SEM. The container 102 has a top aperture that allows light 116 to be directed upward away from the substrate 104 and into the aperture 120. For example, the container 102 has an aperture 107 (e.g., an opening or a window) on the top surface 106 of the container 102. In another example, the top surface 106 of the container 102 is absent, so that the top of the container 102 is open.

[0015] Directing the light 116 to the aperture 120 guides the light 116 into the column of the SEM. For example, the mirror 114 can direct the light 116 upward through the aperture 120 and into the column of the SEM in a direction away from the substrate 104 (e.g., perpendicular to the substrate 104). The aperture 120 may be an aperture in a lens 122 (e.g., a magnetic lens) that is used during normal operation to focus electrons onto a target to be imaged, and the target is mounted on the stage 126 during normal operation. The electron detector 124 is used during normal operation to detect secondary electrons scattered from the surface of the target to be imaged.

[0016] Lens 110 can direct light 116 along an optical path substantially parallel to substrate 104 to mirror 114. The optical path corresponds to optical axis 118 parallel to substrate 104 between lens 110 and mirror 114. Mirror 114 changes the direction of optical axis 118 and the optical path (e.g., 90 degrees upward away from substrate 104). Optical axis 118 then passes through aperture 118 and terminates at electron detector 124, such that light 116 illuminates electron detector 124. Stage 126 is disposed in vacuum chamber 128 with mirror 114 positioned in line of sight with electron detector 124 through aperture 120. In some embodiments, lens 110 focuses light 116 onto aperture 120 (e.g., such that substantially all light 116 passes through aperture 120 to reach electron detector 124). In some embodiments, lens 110 collimates light 116 (e.g., such that a collimated light beam is incident on aperture 120. The collimated beam may be wider than aperture 120, such that only a portion of the collimated beam passes through aperture 120 to enter electron detector 124).

[0017] Light source 108 generates light 116 (e.g., a laser beam or LED light), and provides light 116 to lens 110 (e.g., to optical system 112) along an optical path corresponding to optical axis 118. The portion of optical axis 118 between light source 108 and lens 110 may be parallel to substrate 104 (e.g., along the portion of optical axis 118 between lens 110 and mirror 114). Accordingly, light source 108 supplies light 116 to the optical system that directs light 116 along the optical path. The optical path may initially be substantially parallel to substrate 104, and then oriented upward away from substrate 104.

[0018] The output and wavelength of the light source 108 are selected, according to several embodiments, to enable effective charge detrapping for the electron detector 124. For example, the light source 108 has a power of 1 mW to 100 mW and produces light 116 having a wavelength in the range of 250 nm to 600 nm. For example, the wavelength may be ultraviolet, or violet, or blue, or green, or yellow, or orange. If the power to light 116 is too low, the charge detrapping will be too long and therefore impractical, while if the power to light 116 is too high, it may damage components in the SEM. Similarly, if the wavelength of light 116 is too long, it may not be effective for charge detrapping, while if the wavelength of light 116 is too short, it may damage components in the SEM.

[0019] The light source 108 may be configured to operate in multiple power states (i.e., modes). For example, the light source 108 can operate in a first full-power state and a second low-power state, where the power of the light 116 generated in the first full-power state is higher than the power of the light 116 generated in the second low-power state. The light source 108 may also be turned off. The first full-power state may be used for charge detrapping. The second low-power state may be used to align the device 100 (e.g., mirror 114) with the aperture 120. Alignment is performed to position the device 100 so that the optical axis 118, and therefore the light 116, passes through the aperture 120 to the electron detector 124. Alignment can be performed by operating the light source 108 in the second low-power mode and moving the stage 126 until the electron detector 124 detects the light 116. For example, the stage 126 may be an xy stage with corresponding motors that move the stage 126 until it is properly positioned. Once the alignment is complete with the device 100 properly positioned, the light source 108 is switched to a first full-power state to perform charge detrapping.

[0020] In some embodiments, the container 102 may be omitted. Figure 2 is a cross-sectional view of the apparatus 200 according to some embodiments, in which the container 102 is omitted and the substrate 104 is replaced by a substrate 202. The light source 108, lens 110, and mirror 114 are mechanically coupled to the substrate 202 by being mounted on top of the substrate 202. For example, the light source 108, optical components 112, and / or mirror 114 may be directly mechanically coupled (e.g., fixed) to the substrate 202.

[0021] In Figure 2, the apparatus 200 is loaded onto the stage 126 in the vacuum chamber 228 of the SEM, according to several embodiments. Targets can be loaded onto the stage 126 in the vacuum chamber 228 for imaging during normal operation of the SEM. In some embodiments, these targets are semiconductor wafers. The SEM is sometimes referred to as a wafer SEM. However, the apparatus 200 is not used during normal operation, but instead is used for maintenance of the SEM or for testing the SEM. The substrate 202 may be wafer-shaped or otherwise molded to allow the apparatus 200 to be loaded into the SEM and onto the stage 126. The light source 108, lens 110, optical components 112, and mirror 114 of the apparatus 200 function as described for apparatus 100 (Figure 1).

[0022] Figure 3 shows the insertion of the device 100 (Figure 1) into the SEM 300 through the load lock 302 of the SEM 300 according to several embodiments. The SEM 300 includes a vacuum chamber 128 (Figure 1). In some embodiments, the SEM 300 is configured to image a reticle and is used during normal operation, and the device 100 is shaped to the reticle shape or otherwise to allow the device 100 to be loaded into the vacuum chamber 128 of the SEM 300 through the load lock 302. The load lock 302 is isolated from the vacuum chamber 128. The load lock 302 is directly accessible from the outside of the SEM 300, but the vacuum chamber 128 is not directly accessible, but is instead accessible through the load lock 302. The device 100 is loaded into the SEM 300 via the load lock 302. With the load lock 302 at atmospheric pressure, the device 100 is loaded into the load lock 302 from the outside of the SEM 300. With the device 100 in the load lock 302, the load lock 302 is then pumped down to a vacuum. Once a vacuum is established within the load lock 302, the device 100 is transferred into the vacuum chamber 128 and onto the stage 126 (Figure 1). The device 100 is aligned with the opening 120 (Figure 1) (e.g., using a second low-power state for the light source 108) and is then used to illuminate the electron detector 124 (Figure 1) to perform maintenance on the electron detector 124 (e.g., using a first full-power state for the light source 108) and / or to test the electron detector 124. Once maintenance and / or testing is complete, the device 100 is returned from the vacuum chamber 128 to the load lock 302, which is under vacuum and then ventilated to atmospheric pressure, and then the device 100 is removed from the load lock 302. Thus, the device 100 is loadable onto the SEM 300 and detachable from the SEM 300 via the load lock 302.

[0023] Figure 4 shows the insertion of the device 200 (Figure 2) into the SEM 400 through the load lock 402 of the SEM 400 according to several embodiments. The SEM 400 includes a vacuum chamber 228 (Figure 2) separate from the load lock 402. The load lock 402 is directly accessible from the outside of the SEM 400, but the vacuum chamber 228 is not directly accessible and is instead accessible through the load lock 402. In some embodiments, the SEM 400 is configured to image a semiconductor wafer (e.g., the SEM 400 is a wafer SEM) and is used during normal operation, and the device 200 is either wafer-shaped (e.g., having a wafer-shaped substrate 202 in Figure 2) or otherwise shaped to allow the device 200 to be loaded into the vacuum chamber 228 of the SEM 400 through the load lock 402. Device 200 is loadable into and unloadable from SEM 400 (i.e., vacuum chamber 228) via load lock 402 (Figure 3), just as device 100 is loadable into and unloadable from SEM 300 via load lock 302 (Figure 3).

[0024] In some embodiments, the light source 108 is omitted from the apparatus 100 or 200. Figure 5 is a cross-sectional view of an apparatus 500 used to illuminate an electron detector 124 in an SEM, without the light source 108, according to some embodiments. Apparatus 500 corresponds to apparatus 100 (Figure 1), but the light source 108 is omitted. The lens 110, optical components 112, and mirror 114 of apparatus 500 are arranged in a container 502. The container 502 is reticle-shaped or otherwise shaped in such a way that it can be loaded into an SEM that can be configured and used to image a reticle. The container 502 has a bottom surface that serves as a substrate 504 to which the lens 110 and mirror 114 are directly or indirectly mechanically coupled. For example, the mirror 114 and / or optical components 112, including the lens 110, may be fixed to the substrate 504 and thus directly mechanically coupled. In another example, the optical components 112 and / or mirror 114 may be fixed to one or more sides of the container 502 and thus mechanically coupled indirectly to the substrate 504 (i.e., relative to the bottom surface of the container 502), since the sides of the container 502 are connected to the substrate 504.

[0025] The optical system on apparatus 500 functions as described for apparatus 100 (Figure 1). Light 516 is supplied to the optical system on apparatus 500 from a light source separate from apparatus 500 (i.e., to lens 110 in optical component 112 and to mirror 114). The separate light source may be outside the SEM or located inside the SEM. The SEM has an optical system (e.g., optical fiber and / or free-space optical system including mirrors) that guides light 516 to the optical system on apparatus 500 along an optical path corresponding to the optical axis 518. Lens 110 can guide light 516 to mirror 114 along an optical path substantially parallel to the substrate 504. The optical axis 518 corresponding to this optical path is parallel to the substrate 504 between lens 110 and mirror 114. Mirror 114 changes the direction of the optical axis 118 and the optical path (e.g., 90 degrees upward from the substrate 504), directing light 516 upward away from the substrate 504. Container 502, like container 102 (Figure 1), has a top opening that allows light 516 to be directed upward away from the substrate 504 into the opening 120 (Figure 1). For example, container 502 has an opening 507 (e.g., an opening or window) on its top surface 506. In another example, the top surface 506 of container 502 is absent, and the top surface of container 502 is open.

[0026] Figure 6 is a cross-sectional view of a device 600 used to irradiate an electron detector 124 in a SEM, corresponding to device 200 (Figure 2) but omitting the light source 108, according to several embodiments. The lens 110 and mirror 114 of device 600 are mechanically coupled to the substrate 602 by being mounted on top of the substrate 602. For example, the optical components 112 and / or the mirror 114 may be mechanically coupled (e.g., fastened) directly to the substrate 602. The substrate 602 may be wafer-shaped or of other shape that allows device 200 to be loaded into an SEM which may be a wafer SEM. The optical system on device 600, including the lens 110, optical components 112, and mirror 114, functions as described for devices 100 (Figure 1), 200 (Figure 2), and 500 (Figure 5).

[0027] Figure 7 shows the insertion of the apparatus 712 into the SEM 700 through the load lock 702 of the SEM 700 according to several embodiments. The apparatus 712 includes a substrate and an optical system that directs light upward away from the substrate, but does not include a light source that generates the light. For example, the substrate 712 may be substrate 500 (Figure 5) or substrate 600 (Figure 6). In some embodiments, the SEM 700 is configured to image a reticle and is used during normal operation. In some embodiments, the SEM 700 is a wafer SEM.

[0028] The SEM 700 includes a vacuum chamber 704 containing an electron detector (e.g., electron detector 124), an aperture (e.g., aperture 120 in lens 122), and a stage (e.g., stage 126). A load lock 702 is separated from the vacuum chamber 704. The load lock 702 is directly accessible from the outside of the SEM 700, but the chamber 704 is not directly accessible and is instead accessible through the load lock 702. The device 700 is loadable into the SEM 700 (i.e., the vacuum chamber 704) and unloadable from the SEM 700 (i.e., the vacuum chamber 704) via the load lock 702, and unloadable from the SEM 400 via the load lock 402 (Figure 4), just as device 100 is loadable into and unloadable from the SEM 300 via the load lock 302 (Figure 3), and device 200 is loadable there.

[0029] A light source 708 (e.g., a laser or LED) located outside the SEM 700 generates light 710 (e.g., light 516 in Figure 5 or 6) which is transmitted into the vacuum chamber 704 through a port 706 (e.g., a window or fiber optic coupling) inside the SEM 700. Light 710 is provided to the apparatus 712 when the apparatus 712 is loaded into the vacuum chamber 704. The SEM 700 has an optical system (e.g., a fiber optic and / or free-space optical system including mirrors) for directing light 710 into the optical system on the apparatus 700 (e.g., along the optical path 518 in Figures 5-6). Light source 708, like light source 108, may be configured to operate in multiple power states (i.e., modes). For example, light source 708, like light source 108, may have a first full-power state, a second low-power state, and an off state. The power of light 710 generated in the first full-power state is higher than the power of light 710 generated in the second low-power state. The power and wavelength of the light 710 generated by the light source 708 may be the same as the power and wavelength of the light 116 generated by the light source 108 (Figures 1-2).

[0030] In some embodiments, the light source 708 may be located inside the SEM700 rather than outside it, and port 706 may be omitted.

[0031] Apparatus 100 (Figures 1 and 3) may have additional components other than the light source 108, lens 110, optical component 112, and mirror 114. The additional components may be placed inside the container 102. Similarly, apparatus 200 (Figures 2 and 4) may have additional components that can be mounted on the substrate 202.

[0032] Figure 8 is a block diagram showing components of the apparatus 800 according to several embodiments. The apparatus 800 may be an example of apparatus 100 (Figures 1, 3) or 200 (Figures 2, 4). The apparatus 800 has a substrate (e.g., substrate 104 in Figure 1, substrate 202 in Figure 2) on which the components shown in Figure 8 are directly or indirectly mechanically coupled. These components of the apparatus 800 include an optical system 802 (e.g., lens 110 and mirror 114; lens 110, optical component 112, and mirror 114), a light source 804 (e.g., light source 108), electronic equipment 806, a battery 808, a battery charger 810, and a plug 812. The electronic equipment 806 is electrically coupled to the light source 804 and controls the light source 804. The electronic equipment 806 may be used to turn the light source 804 on and off and to control the power of the light produced by the light source 804 (e.g., by controlling the power supplied to the light source 804). In some embodiments, the electronic device 806 is used to switch the light source 804 between different states, including a first ON state (e.g., a first full-power state of the light source 108), a second ON state with lower power than the first ON state (e.g., a second low-power state of the light source 108), and an OFF state. The battery 808 is electrically coupled to the electronic device 806 and the light source 804 and supplies power to them. The battery 808 may also be electrically coupled to the light source 804 through the electronic device 806, and the electronic device 806 controls the amount of power supplied from the battery 808 to the light source 804.

[0033] The battery charger 810 is electrically coupled to the battery 808 and charges the battery 808. The battery charger 810 is also electrically coupled to the plug 812, through which the battery charger 810 receives power to charge the battery 808 (for example, to recharge the battery 808 after the device 800 has been used in the SEM). To charge the battery 808, the plug 812 is connected to (e.g., accepts) the connector for the external power supply of the device 800 and the SEM. The plug 812 receives power for the charger 810 from this external power supply when the device 800 is not in the SEM. The charger 810 uses this power to charge the battery 808.

[0034] Figure 9 is a block diagram showing components of the apparatus 900 according to several embodiments. Apparatus 900, such as apparatus 800 (Figure 8), may be an example of apparatus 100 (Figures 1, 3) or 200 (Figures 2, 4). Apparatus 900 has a substrate (e.g., substrate 104 in Figure 1, substrate 202 in Figure 2) on which the components shown in Figure 9 are directly or indirectly mechanically coupled. These components of apparatus 900 include an optical system 902 (e.g., lens 110 and mirror 114, lens 110, optical component 112, and mirror 114), a light source 904 (e.g., light source 108), electronic equipment 906, and an electrical connector 908. Electronic equipment 906 is electrically coupled to the light source 904 and controls the light source 904 in the same way that electronic equipment 806 controls the light source 804 (Figure 8). The electrical connector 908 is electrically coupled to the electronic equipment 906 and the light source 904 to supply power to the electronic equipment 906 and the light source 904. The electrical connector 908 receives power from the SEM's power supply and provides that power to the electronic equipment 906 and the light source 904. For example, the electrical connector 908 contacts electrical contacts within the SEM that are normally used during operation to bias the target being imaged. The electrical connector 908 receives power through these electrical contacts. The electrical connector 908 may also be electrically coupled to the light source 904 through the electronic equipment 906, which controls the amount of power supplied to the light source 904.

[0035] Figure 10 is a flowchart illustrating method 1000 for illuminating an electron detector in an SEM according to several embodiments. In method 1000, the apparatus is loaded into the SEM (1002). Examples of apparatus include apparatus 100 (Figures 1 and 3), 200 (Figures 2 and 4), 500 (Figure 5), 600 (Figure 6), 712 (Figure 7), 800 (Figure 8), and 900 (Figure 9). Examples of SEMs include SEM 300 (Figure 3), 400 (Figure 4), and 700 (Figure 7). The apparatus is loaded into the SEM through the load lock of the SEM (e.g., load lock 302 in Figure 3, 402 in Figure 4, 702 in Figure 7) (1002) and loaded onto the stage of the SEM (e.g., stage 126 in Figures 1, 2, 5, or 6). The apparatus includes a substrate (e.g., substrate 104 in Figure 1, 202 in Figure 2, 504 in Figure 5, 602 in Figure 6) and an optical system (e.g., optical system 802 in Figure 8, 902 in Figure 9) mechanically coupled to the substrate to direct light upward away from the substrate. In some embodiments, the optical system includes a lens (e.g., lens 110 in Figures 1, 2, 5, or 6) and a mirror (e.g., mirror 114 in Figures 1, 2, 5, or 6) (1004). The apparatus may further include a light source mechanically coupled to the substrate (e.g., light source 108 in Figure 1 or 2, 804 in Figure 8, 904 in Figure 9) (1006). Alternatively, the light source may be omitted (e.g., Figures 5-7 with respect to apparatuses 500, 600, and 712).

[0036] In some embodiments, once the apparatus is loaded onto the stage, low-power light is generated and supplied to the optical system (1008). Using the low-power light, the mirror is aligned with the aperture (e.g., aperture 122 in Figure 1 or 2) and the electron detector (e.g., electron detector 124 in Figure 1 or 2) (1010).

[0037] In some embodiments, after alignment has been performed (for example, after the mirror has been aligned with the aperture and electron detector in step 1010), light is generated and supplied to the optical system using a light source (1012).

[0038] Alternatively (for example, if the light source is omitted from the apparatus), light is received by the optical system from a light source outside the apparatus (for example, light source 708 in Figure 7). In either case, this light may be of first power (for example, in the first full power state of light source 108), and the light in steps 1008 and 1010 may be of second power (for example, in the second low power state of light source 108), where the second power is lower than the first power. Low-power light is lower power than full-power light.

[0039] In the stage-mounted apparatus after alignment has been performed, an optical system is used (1014) to direct light upward through an aperture (e.g., aperture 122 in Figure 1 or 2) onto an electron detector (e.g., electron detector 124 in Figure 1 or 2). In some embodiments, the light is guided to a mirror along a substantially parallel optical path to the substrate using a lens (1016), and then directed upward toward the aperture using the mirror (1018). In some embodiments, the light is focused into the aperture using a lens (1020). Alternatively, the light may be collimated using a lens so that a collimated beam of light enters the aperture.

[0040] After directing light upward onto the electron detector through the aperture, the device is removed from the SEM via a load lock (1022). For example, the device is removed after the electron detector has been irradiated for a sufficient amount of time to recover its bandwidth through charge detrapping and / or after the electron detector has been tested using light.

[0041] Figure 10 shows the steps of method 1000 to be performed in a specific order. In practice, certain groups of steps may be performed simultaneously or overlapping. For example, steps 1008 and 1010 may be performed simultaneously or overlapping. Steps 1012 and 1014 may also be performed simultaneously or overlapping. However, according to some embodiments, steps 1008 and 1010 are performed before steps 1012 and 1014.

[0042] The foregoing description is provided with reference to specific embodiments for illustrative purposes. However, the above exemplary description is not intended to be exhaustive or to limit the claims to the exact form disclosed. Many modifications and variations are possible in light of the above teachings. The embodiments were selected to best illustrate the principles underlying the claims and their practical application, thereby enabling other persons skilled in the art to best use the embodiments with various modifications suitable for the specific use intended.

Claims

1. It is a device, circuit board and An optical system mechanically coupled to the substrate, directing light away from the substrate and upward towards the aperture of a scanning electron microscope (SEM), A device comprising the above, which can be loaded into the SEM and removed from the SEM through the load lock of the SEM.

2. The optical system includes a mirror that directs the light upward so as to move it away from the substrate, A lens that guides light to the mirror along an optical path substantially parallel to the substrate, The apparatus according to claim 1, characterized by including the following:

3. The apparatus according to claim 2, characterized in that the lens focuses the light into the aperture of the SEM.

4. A light source that is mechanically coupled to the substrate and generates and provides the light to the optical system, The apparatus according to claim 2, further comprising:

5. The apparatus according to claim 4, characterized in that the light source is a laser or a light-emitting diode (LED).

6. The light source generates light in the wavelength range of 250 nm to 600 nm. The aforementioned light source generates light with a power in the range of 1 mW to 100 mW. The apparatus according to feature 4.

7. The present invention further includes electronic equipment that is mechanically coupled to the substrate and electrically coupled to the light source to control the light source, The electronic device switches the light source between multiple states. The aforementioned plurality of states include a first ON state, a second ON state, and an OFF state. The light generated by the first ON-state light source has higher power than the light generated by the second ON-state light source. The apparatus according to feature 4.

8. A battery that is mechanically coupled to the substrate and electrically coupled to the electronic device and the light source, and supplies power to the electronic device and the light source, The apparatus according to claim 7, further comprising:

9. A battery charger that is mechanically coupled to the substrate and electrically coupled to the battery to charge the battery, A plug mechanically coupled to the substrate and electrically coupled to the battery charger to receive power for the battery charger when the device is not inside the SEM, The apparatus according to claim 8, further comprising

10. An electrical connector that is mechanically coupled to the substrate and electrically coupled to the electronic device and the light source, receives power from the SEM's power supply, and provides power to the electronic device and the light source. The apparatus according to claim 7, further comprising:

11. The apparatus according to claim 1, characterized in that it does not include a light source for generating the light.

12. A container for housing the optical system, Includes, The aforementioned container is reticle-shaped, The substrate is the bottom surface of the container, The optical system is placed inside the container. The container has a top aperture that allows the optical system to direct the light upward into the aperture. The apparatus according to feature 1.

13. The aforementioned substrate is in wafer form, The optical system is mounted on the upper part of the substrate. The apparatus according to feature 1.

14. It is a method, The step involves loading the device onto the stage of a scanning electron microscope (SEM) through the load lock of the SEM, wherein the device is circuit board and An optical system mechanically coupled to the substrate to direct light upward so as to move away from the substrate, Includes, With the apparatus on the stage of the SEM, the optical system is used to direct light upward through the aperture of the SEM onto the electron detector inside the SEM. A method that includes this.

15. After directing the light upward onto the electron detector through the aperture, the device is removed from the SEM through the load lock. The method according to claim 14, further comprising:

16. The optical system includes lenses and mirrors, The step of directing the light upward through the aperture using the optical system is: The steps of using the lens to guide light to the mirror along an optical path substantially parallel to the substrate, The steps include using the mirror to direct the light upward toward the aperture, The steps of focusing the light into the aperture using the lens, The method according to 14, characterized by including the following:

17. The apparatus further comprises a light source mechanically coupled to the substrate, The aforementioned method, The steps of generating light, The steps of providing the light to the optical system using the light source, The method according to 16, further comprising:

18. The aforementioned light is light of first power, The method, before generating, providing, inducing, directing, and focusing the first power of light, The steps include generating and supplying light of a second power to the optical system, wherein the second power is lower than the first power, and the mirror directs the light of the second power upward away from the substrate, The steps include aligning the mirror with the aperture and the electron detector using the second power of light, The method according to 17, characterized by including the following:

19. The aforementioned SEM is configured to image the reticle, The container is reticle-shaped, The substrate is the bottom surface of the container, The optical system is placed inside the container. The container has a top opening, The step of using the optical system to direct the light upward includes the step of directing the light through the top aperture. The method according to feature 14.

20. The aforementioned SEM is configured to image a semiconductor wafer, The aforementioned substrate is in wafer form, The optical system is mounted on the upper part of the substrate. The method according to feature 14.

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