Improvement of navigation accuracy using camera coupled with detector assembly

Abstract

To provide methods and systems for improving navigation accuracy in X-ray measurements.SOLUTION: A system includes first and second imaging assemblies and a processor. The first imaging assembly is configured to produce a first image of a measurement site in a sample. The second imaging assembly is coupled with a measurement assembly and is configured to produce a second image of the measurement site. The processor is configured to: (i) perform, based on the first image, a first movement of the sample relative to the measurement assembly, (ii) perform, based on the second image, a second movement of the sample for aligning the sample with the measurement assembly, and (iii) control the measurement assembly to perform a measurement in the measurement site.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates generally to x-ray analysis, and more particularly to a method and system for improving navigation accuracy in x-ray measurements. [Background technology]

[0002] Various techniques have been published to improve navigation accuracy in semiconductor manufacturing processes.

[0003] For example, U.S. Patent Application Publication No. 2007 / 0290703 describes a method and system for probing electrical test signals on an integrated circuit test sample using a high-resolution microscope positioned to observe the surface of the test sample, which exposes conductive terminals. A housing is provided with a carrier for supporting the test sample relative to the microscope, and a probe assembly is positionable on the surface of the test sample to transfer and acquire electrical test signals to and from the test sample. A drive system is provided for shifting at least one of the probe and the carrier to a predetermined test position. In one form, the system includes a heat shield for protecting one of the probe assembly and the carrier from thermal energy generated during operation of the drive system, and in another form, the system includes an environmental control for maintaining a desired temperature within the housing to enable accurate measurements to be taken from the test sample.

[0004] U.S. Patent Application Publication No. 2020 / 0319443 discloses an autofocus system. The system includes an illumination source. The system includes an aperture. The system includes a projection mask. The system includes a detector assembly. The system includes a relay system configured to optically couple illumination transmitted through the projection mask to an imaging system. The relay system is also configured to project one or more patterns from the projection mask onto a test sample and transmit images of the projection mask from the test sample to the detector assembly. The system includes a controller including one or more processors configured to execute a set of program instructions. The program instructions are configured to cause the one or more processors to receive one or more images of the projection mask from the detector assembly and determine quality of the one or more images of the projection mask.

[0005] U.S. Patent Application Publication No. 2019 / 0310080 describes an overlay metrology tool providing site-by-site alignment, including a controller coupled to a telecentric imaging system, which receives two or more alignment images of an overlay target on a specimen captured at two or more focal positions by the imaging system, generates alignment data indicating the alignment of the overlay target in the imaging system based on the alignment images, sets the alignment image as a measurement image if the alignment of the overlay target is within a selected alignment tolerance, and instructs the imaging system to adjust the alignment of the overlay target in the imaging system if the alignment of the overlay target is outside the selected alignment tolerance, further receives one or more measurement images from the imaging system, and then determines overlay between two or more layers of the specimen based on at least one of the measurement images.

[0006] U.S. Patent Application Publication No. 2015 / 0241469 describes a scanning probe microscope (SPM) system and related methods, including an SPM system having a probe adapted to interact with nanoscale features of a sample and scan within a target area to generate a three-dimensional image of the target area, the system maintaining positional information of a plurality of features of interest of the sample according to a sample-specific coordinate system, the SPM system configured to adjust positioning of the probe relative to the sample according to the SPM coordinate system, and the SPM system further configured to manage a dynamic relationship between the sample-specific coordinate system and the SPM coordinate system by determining a set of alignment errors between the sample-specific coordinate system and the SPM coordinate system and applying corrections to the SPM coordinate system to account for the determined alignment errors. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US Patent Application Publication No. 2007 / 0290703 [Patent Document 2] U.S. Patent Application Publication No. 2020 / 0319443 [Patent Document 3] US Patent Application Publication No. 2019 / 0310080 [Patent Document 4] US Patent Application Publication No. 2015 / 0241469 [Patent Document 5] U.S. Patent No. 6,108,398 [Patent Document 6] U.S. Patent No. 9,632,043 Summary of the Invention

[0008] Embodiments of the invention described herein provide a system that includes first and second imaging assemblies and a processor.

[0009] The first imaging assembly is configured to produce a first image of a measurement site in the sample. The second imaging assembly is coupled to the measurement assembly and configured to produce a second image of the measurement site. The processor is configured to (i) perform a first movement of the sample relative to the measurement assembly based on the first image, (ii) perform a second movement of the sample to align the sample with the measurement assembly based on the second image, and (iii) control the measurement assembly to perform a measurement at the measurement site.

[0010] In some embodiments, the sample includes a semiconductor substrate, the measurement site includes a structure created in the semiconductor substrate, the first imaging assembly includes an optical microscope, and the second imaging assembly includes an optical camera.

[0011] In other embodiments, the optical microscope is configured to generate a first image at one or more magnifications, the optical camera is configured to generate a second image, and the processor is configured to identify the measurement site in the first and second images. In yet other embodiments, the measurement assembly includes one or more X-ray detector assemblies (XDAs), each XDA including a plurality of energy dispersive X-ray detectors surrounding a measurement location, and (i) a first distance between the optical microscope and the measurement location is greater than 50 mm, and (ii) a second distance between the optical camera and the measurement location is less than 25 mm.

[0012] In some embodiments, the processor is configured to align the measurement location with the measurement site based on at least the second image. In other embodiments, the optical camera is positioned at a third distance less than 20 mm from at least one of the SDDs. In yet other embodiments, the optical camera is configured to generate the second image at a single magnification.

[0013] In some embodiments, at least one of the energy dispersive X-ray detectors includes a silicon drift detector (SDD). In other embodiments, the system includes an X-ray source configured to direct an X-ray beam to the measurement location, and in response to directing the X-ray beam, at least one of the energy dispersive X-ray detectors is configured to detect X-ray fluorescence (XRF) emitted from the sample. In yet other embodiments, when the measurement location is aligned with the measurement site, the processor is configured to perform XRF measurements on structures created in the semiconductor substrate.

[0014] In some embodiments, (i) based on the first image, the processor is configured to derive a first positioning error between the measurement site and the measurement position in the first movement, and (ii) based on the second image, the processor is configured to derive a second positioning error between the measurement site and the measurement position in the second movement, the second positioning error being smaller than the first positioning error. In other embodiments, the optical camera and the SDD are coupled to a common support structure of the measurement assembly.

[0015] In an embodiment, at least one of the first movement and the second movement comprises a plurality of movements, hi another embodiment, the second movement is smaller than the first movement.

[0016] According to an embodiment of the present invention, there is additionally provided a system comprising: (a) an interface configured to receive (i) a first signal from a first imaging assembly and (ii) a second signal from a second imaging assembly coupled to a measurement assembly; and (b) a processor, wherein the processor is configured to: (i) identify a measurement site in the sample based on the first signal; (ii) perform a first movement of the sample relative to the measurement assembly; (iii) identify the measurement site based on the second signal; and (iv) perform a second movement of the sample relative to the measurement assembly to perform a measurement at the measurement site.

[0017] According to an embodiment of the present invention, there is additionally provided a method including receiving a first signal from a first imaging assembly and a second signal from a second imaging assembly coupled to a measurement assembly. A measurement site is identified based on the second signal, and a second movement of the sample relative to the measurement assembly is performed to align the sample with the measurement assembly. A measurement is performed at the measurement site.

[0018] The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken in conjunction with the drawings, in which: [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic illustration of a system for X-ray fluorescence (XRF) measurements in accordance with an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic illustration of a system for X-ray fluorescence (XRF) measurements in accordance with an embodiment of the present invention. [Figure 3] FIG. 3 is a schematic illustration of an X-ray detector assembly (XDA) and optical microscope of the system of FIG. 2 above, in accordance with an embodiment of the present invention. [Figure 4] 3 is a flow chart that schematically illustrates a method for performing X-ray measurements and improving navigation accuracy in the system of FIGS. 1 and 2 above, in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] (overview) The very large scale integration (VLSI) manufacturing process of integrated circuits (ICs) typically involves measurements, such as X-ray measurements, at predefined measurement sites within the IC device to ensure that the fabricated structures meet design requirements. As the dimensions of structures within IC devices decrease, the size of the measurement sites decreases, and therefore the requirement for navigation accuracy increases to enable proper measurements at each measurement site.

[0021] Embodiments of the present invention described below provide techniques for improving the navigation accuracy of systems configured to perform processes and / or inspections or measurements at specific locations within ICs during and after their manufacture. In embodiments of the present invention, the system includes an X-ray system configured to perform X-ray measurements at one or more measurement locations defined on a specimen, such as, but not limited to, a semiconductor substrate (e.g., wafer) containing multiple ICs during manufacture.

[0022] In some embodiments, the X-ray system includes an X-ray source configured to direct an X-ray beam at a measurement site, and a measurement assembly, such as an X-ray detector assembly (XDA), which may include a plurality of silicon drift detectors (SDDs) or other solid-state energy dispersive detectors surrounding the measurement site. In response to directing the X-ray beam, at least one of the SDDs, and typically all of the SDDs, is configured to detect X-rays, such as, but not limited to, fluorescent light (XRF), emitted from the semiconductor wafer.

[0023] In some embodiments, the X-ray system includes a first imaging assembly, in this example an optical microscope (OM), configured to generate a first image of the measurement site on the wafer. The OM can have at least two magnifications, referred to herein as low and high. The low magnification (e.g., with an objective lens with a magnification of about 1x) can be used to identify the measurement site within the field of view (FOV) of the OM. The high magnification can be used to generate the first image (e.g., using an objective lens with a magnification of between about 5x and 20x). Additionally or alternatively, the low magnification objective lens can be used to acquire the first image of the measurement site.

[0024] In some embodiments, the X-ray system comprises a second imaging assembly coupled to the measurement assembly and configured to generate a second image of the measurement site, in the present example a camera with unity magnification. In this specification and claims, the terms "coupled with" and "coupled to" also refer to a camera being integral with or integrated into the respective measurement assembly.

[0025] In some embodiments, the X-ray system includes a movable stage controlled by a processor and configured to move the wafer relative to the X-ray source, the XDA, and the imaging assembly. Based on the first and second images, the processor is configured to control the stage to align a measurement location (defined on the wafer) with a measurement site defined by the configuration of the XDA so as to perform an X-ray measurement at the measurement site. It should be noted that any misalignment (e.g., lateral offset) between the measurement location and the measurement site may result in measuring a structure other than the measurement site, thereby degrading the quality of process control.

[0026] In some embodiments, the FOV of the OM is positioned in the X-ray system at a distance greater than about 50 mm, typically about 100 mm, from the measurement location defined by the configuration of the X-ray source and XDA. Furthermore, when the X-ray system includes two or more X-ray sources and XDAs, the distance between the OM and a given measurement location can be at least 100 mm. Typically, the positioning accuracy of the stage is determined, among other things, by the distance traveled by the measurement site relative to the measurement location. Therefore, a shorter stage travel results in better positioning accuracy, and therefore better alignment between the measurement site and the measurement location, which is essential for the quality of X-ray measurements. In this specification and claims, the term "quality" of X-ray measurements refers to the accuracy (e.g., repeatability) and precision of the measurement results. For example, repeatability decreases when measuring different locations (due to errors in positioning accuracy) rather than the same location on the wafer.

[0027] In some embodiments, in the above configuration, the camera FOV has a size of about 3 mm x 3 mm, and the center of the FOV is positioned less than about 25 mm from the measurement site, and in embodiments of the invention, about 10 mm or 20 mm.

[0028] In some embodiments, during a system calibration step performed before measurements are performed, the processor is configured to perform mapping of the movable stage to improve the inherent positioning accuracy of the stage. For example, after stage mapping, the stage positioning error is (i) between about 3 μm and 6 μm over about 100 mm of movement, and (ii) between about 0.3 μm and 0.6 μm over about 10 mm of movement. In this specification and claims, the term "positioning error" refers to the offset (measured in distance) between an intended position and the actual position of a given location on the wafer, e.g., a measurement site.

[0029] In some embodiments, after stage mapping and during processing of the wafer, the processor is configured to receive coordinates of multiple measurement sites. For each measurement site, the processor is configured to move the wafer to position the measurement site within the low magnification FOV of the OM. The processor is configured to identify the measurement site using any suitable technique, such as applying a pattern recognition algorithm to the first image, and control the OM to use high magnification to acquire and generate a first image of the measurement site.

[0030] In some embodiments, based on the first image, the processor is configured to control the stage to perform a first movement of the wafer such that the measurement site is located within the FOV of the camera. Note that the first movement of the stage has a movement range of about 100 mm (or any other suitable movement) such that the measurement site is typically located within the FOV of the camera.

[0031] In some embodiments, the processor is configured to control the camera to generate a second image of the measurement site. In such embodiments, the processor can apply a pattern recognition algorithm to identify the measurement site in both the first and second images. The processor is then configured to control the stage to perform a second movement, e.g., about 10 mm or 20 mm, so that the measurement site is aligned with the measurement location. As noted above, a shorter stage movement, e.g., about 10 mm, significantly improves alignment between the measurement site and the measurement location compared to alignment achieved with a stage movement of about 100 mm.

[0032] In some embodiments, at least one of the first movement and the second movement comprises multiple movements. In other words, one or both of the movements can be performed in one or more positional adjustments after the first movement. Furthermore, the second movement is typically smaller than the first movement.

[0033] In some embodiments, after aligning the measurement site with the measurement location, the processor is configured to control the measurement assembly to perform an X-ray measurement at the measurement site. More specifically, the processor controls the X-ray source to apply an X-ray beam to the measurement site and to perform the X-ray measurement based on signals received from the SDD in response to application of the X-ray beam.

[0034] The disclosed techniques improve the navigation accuracy and measurement quality of X-ray systems and other systems that perform measurements at predefined measurement sites during the integrated circuit manufacturing process.

[0035] (System Description) FIG. 1 is a schematic illustration of an x-ray system 20, in accordance with one embodiment of the present invention.

[0036] In some embodiments, system 20 is configured to perform X-ray measurements at a measurement site on a sample. In the present example, the sample includes a semiconductor substrate, referred to herein as a wafer 22, having structures such as transistors, diodes, and memory cells of an integrated circuit (IC) device. In this example, system 20 includes an X-ray fluorescence (XRF) system, embodiments of which are described in detail in applicant's U.S. Patent Nos. 6,108,398 and 9,632,043.

[0037] In some embodiments, system 20 includes an X-ray source 24, in this example an X-ray tube, driven by a high-voltage power supply unit (PSU) 26. The X-ray tube is configured to emit X-rays having an appropriate energy range and flux to X-ray optics 28, which are aligned with X-ray source 24 in the XYZ coordinate system of system 20. X-ray optics 28 is configured to focus the X-ray beam onto a small area, referred to herein as measurement position (MP) 30, e.g., a spot having a diameter that is typically between about 10 μm and 20 μm on the surface of wafer 22, but which in some applications can be as large as about 100 μm.

[0038] In this specification and claims, the term "about" or "approximately" in connection with any numerical value or range indicates an appropriate dimensional tolerance that enables a part or collection of components to function for its intended purpose as described herein.

[0039] In some embodiments, system 20 includes an integrated optical inspection system, also referred to herein as a first imaging assembly or optical microscope (OM) 50, configured to generate images of the surface of wafer 22 at location 27. In embodiments of the invention, OM 50 has at least two objective lenses configured to generate high magnification (e.g., between about 5x and 20x) and low magnification (e.g., about 1x) images of the surface of wafer 22 at location 27. In embodiments of the invention, the location of OM 50 determines a distance 25 between location 27 and MP 30; for example, distance 25 is greater than about 50 mm, typically about 100 mm.

[0040] In some embodiments, system 20 includes a measurement assembly 35 that is configured to perform one or more X-ray measurements at a site on wafer 22 that is aligned with MP 30. In other words, the X-ray measurements are performed where MP 30 is positioned on the surface of wafer 22.

[0041] In some embodiments, the measurement assembly 35 includes one or more sets of suitable detectors, such as, but not limited to, solid-state energy dispersive X-ray detectors, which in the present example include silicon drift detectors (SDDs) 32, such as SDDs supplied by Bruker Corporation (MA 01821, USA) or SDDs by any other suitable SDD supplier, such as, but not limited to, Amptek Inc. (MA 01730, USA) and KETEK GmbH (Munich, 81737, Germany). Each set of SDDs 32 is disposed in a respective X-ray detector assembly (XDA) 31.

[0042] Reference is now made to inset 29, which shows a bottom view of measurement assembly 35. In an embodiment of the present invention, measurement assembly 35 includes a single XDA 31 with four SDDs 32 arranged in a predetermined geometric shape that surrounds the projection of the position of MP 30 onto the XY plane of measurement assembly 35 (defined by the XYZ coordinate system).

[0043] Referring now back to the overall view of system 20, in some embodiments, system 20 includes a second imaging assembly, in the present example a camera 33, that is coupled to measurement assembly 35. For example, camera 33 may be integrated with measurement assembly 35, e.g., during manufacturing of measurement assembly 35 of system 20. It should be noted that camera 33 is typically not directly coupled to any of SDDs 32, but rather both camera 33 and SDD 32 are coupled to a common support structure (e.g., plate) of measurement assembly 35 and are electrically connected to an external entity (such as a processor, described below) via electrical leads or traces for exchanging signals therebetween.

[0044] In some embodiments, camera 33 is configured to generate an image of the surface of wafer 22 at location 21 located at a distance 23 from MP 30. In the present example, distance 23 is less than about 25 mm, typically about 10 mm, camera 33 has a single magnification, and the image generated by camera 33 has a field of view (FOV) of about 3 mm by 3 mm of the surface of wafer 22.

[0045] In an alternative embodiment, the camera 33 may be positioned in the system 20 at a suitable position (to generate an image at a portion of the wafer 22 located at a distance 23 from the MP 30) without being coupled to the measurement assembly 35.

[0046] The configuration of measurement assembly 35, XDA 31, and camera 33 is provided as an example. In other embodiments, measurement assembly 35 can include any suitable number of XDA 31, each having any suitable number of SDD 32 (and / or any other suitable type of detector) arranged in any suitable configuration. Further, measurement assembly 35 can have any suitable number of imaging assemblies coupled together, arranged using any suitable configuration, in addition to or instead of camera 33.

[0047] In some embodiments, system 20 comprises a signal processing unit 38 having a processor 34, as described herein, and an interface 36 configured to exchange signals between processor 34 and other entities of system 20. System 20 comprises a movable stage 40 controlled by processor 34 and configured to move wafer 22 in the X and Y directions of an XYZ coordinate system, and optionally also in the Z direction. Additionally or alternatively, stage 40 is further configured to rotate the wafer about the Z axis of the XYZ coordinate system.

[0048] In some embodiments, in a system calibration step performed before measurements are taken, processor 34 is configured to map movable stage 40 to improve the stage's inherent positioning accuracy. For example, after stage mapping, stage 40 may have a positioning error of (i) between approximately 3 μm and 6 μm when stage 40 moves approximately 100 mm, and (ii) between approximately 0.3 μm and 0.6 μm when stage 40 moves approximately 10 mm. As used herein and in the claims, the term "positioning error" refers to the offset in the XY plane (measured in distance units, e.g., millimeters) between the intended and actual positions of selected portions of wafer 22 relative to a reference position of system 20. In some cases, the positioning error is not constant but will vary across the XY plane of stage 40.

[0049] In some embodiments, when initiating an X-ray measurement run, processor 34 is configured to receive a list of one or more measurement sites intended to be measured by system 20. Upon selecting a measurement site from the list, wafer 22 is moved so that the selected measurement site is aligned with OM 50 along the Z axis, and processor 34 controls OM 50 to generate a first image of the measurement site. Note that processor 34 is configured to receive the first image from OM 50 and apply a pattern recognition algorithm to identify the measurement site within the FOV of the first image. In some embodiments, processor 34 is configured to control the magnification of OM 50 for acquiring the first image.

[0050] Processor 34 then controls stage 40 to perform a movement (also referred to herein as a first movement) of wafer 22 to position the measurement site within the FOV of camera 33. The first movement of stage 40 has a movement range of distances 25 and 23 that is approximately 100 mm (e.g., between approximately 80 mm and 120 mm), such that the measurement site is typically located within 3 mm x 3 mm of the FOV of camera 33.

[0051] In some embodiments, once the selected measurement site is aligned with camera 33, processor 34 is configured to control camera 33 to generate a second image of the measurement site. In such embodiments, processor 34 may also apply a pattern recognition algorithm to identify the measurement site in the second image. Processor 34 is then configured to control stage 40 to perform a movement (referred to herein as a second movement) along distance 23 from position 21, e.g., about 10 mm, to align the measurement site with MP 30. Note that in this specification and claims, the term "align" and its grammatical variations refer to a positioning accuracy having an offset of less than about 0.5 um in the XY plane of an XYZ coordinate system.

[0052] In some embodiments, reducing the distance traveled by stage 40 from, for example, about 100 mm to about 10 mm significantly improves the positioning accuracy (i.e., reduces the positioning error) of stage 40 from, for example, about 5 μm to about 0.5 μm, respectively. The improved positioning accuracy improves alignment between selected measurement sites on wafer 22 and MP 30.

[0053] In some embodiments, after aligning the measurement site with the MP 30, the processor 34 is configured to control the X-ray source 24 and the measurement assembly 35 to perform X-ray measurements at the measurement site.

[0054] More specifically, in some embodiments, processor 34 controls X-ray source 24 to apply an X-ray beam to MP 30. In response to the X-ray beam being directed at and impinging on the surface of wafer 22, at least one SDD 32, typically each SDD 32, is configured to detect XRF emitted from a measurement site on wafer 22 aligned with MP 30. Note that the position of MP 30 is determined by the configuration and arrangement of X-ray source 24, X-ray optics 28, and SDD 32, as well as the site on wafer 22. In such embodiments, in response to application of the X-ray beam, processor 34 performs X-ray measurements based on signals received from SDD 32.

[0055] 1 is provided as an example and is simplified for conceptual clarity. In other embodiments, wafer 22 is mounted in a suitable fixture, but X-ray source 24, X-ray optics 28, and measurement assembly 35 are moved to perform the X-ray measurements described above.

[0056] In alternative embodiments, the disclosed techniques may be used, mutatis mutandis, in other types of suitable metrology and inspection systems, such as optical-based, non-XRF X-ray-based, electron beam-based, ion beam-based systems, etc. Additionally, the disclosed techniques may be used, mutatis mutandis, in other types of systems configured to perform localized operations other than metrology, such as systems designed for probing processes, localized deposition processes, localized etching and / or drilling processes performed on any suitable specimen, including but not limited to semiconductor substrates.

[0057] In some embodiments, processor 34 comprises a general-purpose computer and is programmed with software to perform the functions described herein. The software may be downloaded to the computer in electronic form, for example, over a network, or alternatively or additionally, may be provided and / or stored on non-transitory, tangible media, such as magnetic, optical, or electronic memory.

[0058] (Improving navigation accuracy in systems with multiple channels) 2 is a schematic illustration of an X-ray system 10 according to an embodiment of the present invention. In some embodiments, while the system 20 of FIG. 1 above has a single channel for making X-ray measurements, the system 10 has multiple channels.

[0059] In some embodiments, system 10 includes a single stage 40, a single OM 50, and a common processing unit 38 (including interface 36 and processor 34), similar to the configuration of system 20 described in FIG. 1 above. However, in an embodiment of the present invention, system 10 includes two sets of X-ray measurement channels. Each X-ray measurement channel of system 10 includes a PSU 26, an X-ray source 24, and a measurement assembly 35. More specifically, system 10 includes measurement assemblies 35a and 35b, each including an SDD 32 and a respective camera 33, e.g., cameras 33a and 33b, respectively, coupled to measurement assemblies 35a and 35b, as described in detail in FIG. 1 above. In such an embodiment, system 10 is configured to simultaneously perform two navigation processes (with improved navigation accuracy as described in FIG. 1 above) and two X-ray measurements at two respective measurement sites on wafer 22.

[0060] 1 above, system 10 may be configured to perform X-ray measurements simultaneously on two wafers 22. Additionally or alternatively, system 10 may include two OMs 50 (i.e., a separate OM for each channel), allowing the first step of the navigation process (i.e., generating a first image using OM 50) to be performed simultaneously on both wafers 22.

[0061] These particular configurations of systems 10 and 20 are presented as examples to illustrate particular problems, such as positioning errors, that are addressed by embodiments of the present invention, and to demonstrate the application of these embodiments in enhancing the performance of such systems. However, embodiments of the present invention are not limited to this particular type of exemplary XRF system, and the principles described herein may be applied to other types of measurement systems known in the art as well.

[0062] FIG. 3 is a schematic illustration of measurement assemblies 35a and 35b of system 10 of FIG. 2 above, in accordance with an embodiment of the present invention.

[0063] In some embodiments, the measurement assembly 35a comprises an XDA 31a having four SDDs 32 and a camera 33a, such as camera 33 in FIG. 1 above, coupled to the measurement assembly 35a in a fixed position relative to the projection of the MP30.

[0064] In some embodiments, measurement assembly 35b, which has a similar structure compared to measurement assembly 35a, comprises an XDA 31b having four SDDs 32 and a camera 33b like camera 33a of measurement assembly 35a. Camera 33b is coupled to measurement assembly 35b at a fixed position relative to the projection of MP30.

[0065] In some embodiments, each of measurement assemblies 35a and 35b has a rectangular shape with a size of about 200 mm along the Y axis and about 80 mm along the X axis, the centers of gravity (COG) of adjacent SDDs 32 are positioned less than about 15 mm from each other, each SDD 32 has a diameter between about 10 mm and 13 mm, and a camera (e.g., camera 33a) is positioned between adjacent SDDs 32 (as shown in FIGS. 1 and 3) or at any other suitable location positioned less than 30 mm, 20 mm, or 10 mm from the projection of MP30.

[0066] 3, measurement assemblies 35a and 35b are positioned at a distance of about 120 mm from each other to allow sufficient space for placing OM 50 therebetween. In other embodiments, OM 50 can be mounted to system 10 at any other suitable location, and measurement assemblies 35a and 35b can therefore be positioned at any other suitable distance from each other. Note that the distance between the X-ray channels is configurable and can be determined based on the size of wafer 22 and the sampling mechanism of the user of system 10, and can allow for two simultaneous X-ray measurements on wafer 22 (or on different wafers 22 in the above-described embodiments).

[0067] The configurations, shapes, and dimensions of measurement assemblies 35a and 35b and their components are provided as examples. In other embodiments, measurement assemblies 35a and 35b can have any other suitable configurations, which may be similar or different from one another, and can have the same or any other suitable components in addition to or instead of the components described in Figures 1 and 3.

[0068] Figure 4 is a flow chart that schematically illustrates a method for performing X-ray measurements to improve navigation accuracy in X-ray system 20, in accordance with an embodiment of the present invention. The method can be applied mutatis mutandis to performing X-ray measurements in system 10 of Figure 2 above.

[0069] In a wafer loading step 100, processor 34 is configured to control the loading of wafer 22 onto system 20 (using any suitable loading technique) and the placement of wafer 22 on stage 40, and then attach wafer 22 to stage 40.

[0070] In measurement site selection step 102, processor 34 receives the list of measurement sites, selects a measurement site from the list, and moves wafer 22 (using stage 40) to the coordinates of the selected site to align the selected measurement site with OM 50 so that the measurement site is positioned within the FOV of OM 50, as described in detail in Figure 1 above.

[0071] In a first image generation step 104, processor 34 generates a first image of the measurement site based on the image signals received from OM 50 and identifies the measurement site in the first image as described in detail above in Figure 1. In some embodiments, processor 34 is configured to calculate the distance between the identified measurement site and the center of the field of view (FOV) of OM 50, which indicates, among other things, a placement error of stage 40.

[0072] In some embodiments, processor 34 controls stage 40 to move wafer 22 to correct the calculated error and to align the measurement site with the center of the FOV of OM 50.

[0073] In a first movement step 106, the processor 34 controls the stage 40 to move the wafer 22 approximately 100 mm to position the measurement site aligned with the camera 33 coupled to the measurement assembly 35 (e.g., in the XY plane of the XYZ coordinate system).

[0074] In some embodiments, the processor 34 may use the error calculated in step 104 to perform mapping of the stage 40 (also referred to herein as stage mapping) to improve the positioning accuracy of the stage 40.

[0075] In a second image generation step 108, processor 34 generates a second image of the measurement site based on the image signals received from camera 33, as described in detail above in Figure 1. Step 108 ends when the measurement site is located within the FOV of the second image generated by camera 33.

[0076] In some embodiments, the processor 34 is configured to calculate a placement error of the stage 40 based on the calculated distance between the measurement site and the center of the FOV of a second image generated based on the signal received from the camera 33, and to adjust the stage mapping to correct the placement error.

[0077] In some embodiments, processor 34 controls stage 40 to move wafer 22 to correct the calculated error and position the measurement site at the center of the FOV of camera 33. Note that in other embodiments, moving wafer 22 to position the measurement site at the center of the FOV of camera 33 can be considered a separate step in the method.

[0078] In a second movement step 110, the processor 34 controls the stage 40 to move the wafer 22 approximately 10 mm or 15 mm to position the measurement site aligned (in the XY plane) with the X-ray source 24 and XDA 31 of the measurement assembly 35, as described in detail in FIG. 1 above.

[0079] In an X-ray measurement step 112, processor 34 controls X-ray source 24 and XDA 31 of measurement assembly 35 to perform one or more X-ray measurements at the measurement site, as described in detail in FIG. 1 above.

[0080] In decision step 114, processor 34 checks whether to take an x-ray measurement at another measurement site on wafer 22. If another measurement is required, the method loops back to step 102.

[0081] If no additional measurements are required on wafer 22 , the method proceeds to wafer unload step 116 , where processor 34 controls the robot of system 20 to unload wafer 22 .

[0082] The method of FIG. 4 is provided as an example and can be used mutatis mutandis in other processes, such as measurements on semiconductor wafers or other suitable substrates having one or more measurement sites.

[0083] The above-described embodiments are cited by way of example, and it will be understood that the scope of the appended claims is not limited to what is particularly shown and described herein. Rather, the scope includes both combinations and subcombinations of the various features described herein, as well as variations and modifications thereof not disclosed in the prior art that would occur to one skilled in the art upon reading the above description. Documents incorporated by reference in this patent application are considered an integral part of this application, except that to the extent that terms are defined in these incorporated documents in a manner that is inconsistent with definitions expressly or implicitly made herein, only the definitions in this specification shall be considered. [Explanation of symbols]

[0084] 20 X-ray systems 22 wafers 24 X-ray source 26 High Voltage Power Supply Unit (PSU) 28 X-ray optics 36 Interface 34 processors

Claims

1. It is a system, A first imaging assembly including an optical microscope, configured to generate a first image of a measurement area including a structure formed in a sample including a semiconductor substrate, A second imaging assembly, which includes an optical camera and is coupled to the measurement assembly, is configured to generate a second image of the measurement area. Processor and Includes, The aforementioned processor, (i) Based on the first image, perform a first movement of the sample relative to the measurement assembly, (ii) Based on the second image, perform a second movement of the sample in order to align the sample with the measurement assembly. (iii) Control the measuring assembly to perform a measurement at the measurement site. It is configured in such a way. system.

2. The system according to claim 1, wherein the optical microscope is configured to generate the first image at a magnification of 1 or 2 or more, the optical camera is configured to generate the second image, and the processor is configured to identify the measurement area in the first image and the second image.

3. The system according to either claim 1 or 2, wherein the measuring assembly comprises one or more X-ray detector assemblies (XDAs), each XDA comprising a plurality of energy-dispersive X-ray detectors surrounding a measurement position, and (i) a first distance between the optical microscope and the measurement position is greater than 50 mm, and (ii) a second distance between the optical camera and the measurement position is less than 25 mm.

4. The system according to claim 3, wherein the processor is configured to align the measurement position with the measurement area based on at least the second image.

5. The system according to claim 3, wherein the optical camera is positioned at a third distance less than 20 mm from at least one of the energy-dispersive X-ray detectors.

6. The system according to claim 3, wherein the optical camera is configured to generate the second image at a single magnification.

7. The system according to claim 3, wherein at least one of the energy-dispersive X-ray detectors includes a silicon drift detector (SDD).

8. The system according to claim 3, comprising an X-ray source configured to direct an X-ray beam to the measurement position, wherein at least one of the energy-dispersive X-ray detectors is configured to detect fluorescent X-rays (XRF) emitted from the sample in response to the directing of the X-ray beam.

9. The system according to claim 8, wherein the processor is configured to perform XRF measurement on the structure formed on the semiconductor substrate when the measurement position is aligned with the measurement area.

10. (i) Based on the first image, the processor is configured to obtain a first positioning error between the measurement area and the measurement position in the first movement; (ii) Based on the second image, the processor is configured to obtain a second positioning error between the measurement area and the measurement position in the second movement, wherein the second positioning error is smaller than the first positioning error, according to claim 3.

11. The system according to claim 3, wherein the optical camera and the energy-dispersive X-ray detector are coupled to a common support structure of the measurement assembly.

12. The system according to claim 1, wherein at least one of the first movement and the second movement includes a plurality of movements.

13. The system according to claim 1, wherein the second movement is smaller than the first movement.

14. It is a system, (i) an interface configured to receive a first signal from a first imaging assembly and (ii) a second signal from a second imaging assembly coupled with a measurement assembly, Processor and Includes, The processor is configured to (i) identify a measurement site in a sample based on the first signal, (ii) perform a first movement of the sample relative to the measurement assembly, (iii) identify the measurement site based on the second signal, and (iv) perform a second movement of the sample relative to the measurement assembly to perform a measurement at the measurement site, wherein the sample includes a semiconductor substrate, the measurement site includes a structure formed on the semiconductor substrate, the first imaging assembly includes an optical microscope, and the second imaging assembly includes an optical camera. system.

15. The system according to claim 14, wherein the measuring assembly comprises one or more X-ray detector assemblies (XDAs), each XDA comprising a plurality of energy-dispersive X-ray detectors surrounding a measurement position, (i) a first distance between the optical microscope and the measurement position is greater than 50 mm, and (ii) a second distance between the optical camera and the measurement position is less than 25 mm.

16. (i) Based on the first signal, the processor is configured to obtain a first positioning error between the measurement area and the measurement position in the first movement, and (ii) Based on the second signal, the processor is configured to obtain a second positioning error between the measurement area and the measurement position that is smaller than the first positioning error in the second movement.

17. The system according to claim 15, wherein at least one of the energy-dispersive X-ray detectors includes a silicon drift detector (SDD).

18. The system according to claim 15, wherein the optical camera and the energy-dispersive X-ray detector are coupled to a common support structure of the measurement assembly.

19. It is a method, The steps include receiving a first signal from a first imaging assembly and receiving a second signal from a second imaging assembly coupled to a measurement assembly, Based on the first signal, the steps include identifying the measurement site in the sample and performing a first movement of the sample relative to the measurement assembly, The steps include identifying the measurement site based on the second signal and performing a second movement of the sample relative to the measurement assembly in order to align the measurement assembly with the sample, The steps include: performing a measurement at the aforementioned measurement site, A method comprising: the sample comprising a semiconductor substrate; the measurement site comprising a structure formed on the semiconductor substrate; the first imaging assembly comprising an optical microscope; and the second imaging assembly comprising an optical camera.

20. The method according to claim 19, wherein the measuring assembly comprises one or more X-ray detector assemblies (XDAs), each XDA comprising a plurality of energy-dispersive X-ray detectors surrounding a measurement position, (i) a first distance between the optical microscope and the measurement position is greater than 50 mm, and (ii) a second distance between the optical camera and the measurement position is less than 25 mm.

21. (i) Based on the first signal, a step of obtaining a first positioning error between the measurement site and the measurement position in the first movement, (ii) The method according to claim 20, further comprising the step of obtaining a second positioning error between the measurement portion and the measurement position in the second movement that is smaller than the first positioning error, based on the second signal.

22. The method according to claim 21, wherein the camera and the energy-dispersive X-ray detector are coupled to a common support structure of the measurement assembly.

23. The method according to any one of claims 19 to 22, wherein the step of performing the second move includes the step of performing a move smaller than the first move.

Images