Improving navigation accuracy using a camera integrated with a 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 generally relates to X-ray analysis, and more particularly to methods and systems for improving navigation accuracy in X-ray measurement.

Background Art

[0002] Various techniques for improving navigation accuracy in semiconductor manufacturing processes have been disclosed.

[0003] For example, U.S. Patent Application Publication No. 2007 / 0290703 describes a method and system for probing an electrical test signal on a test sample of an integrated circuit using a high-resolution microscope positioned to observe the surface of the test sample with exposed conductive terminals. A housing with a carrier for supporting the test sample with respect to the microscope is provided, and the probe assembly is positionable on the surface of the test sample to carry and acquire an electrical test signal between the test sample. A drive system is provided to shift at least one of the probe and the carrier to a predetermined test position. In one form, the system has a thermal 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 has an environmental control unit for maintaining the interior of the housing at a desired temperature so that accurate measurements can be made 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, which is 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 sample and to send images of the projection mask from the sample to the detector assembly. The system includes a controller, which includes one or more processors configured to execute a set of program instructions. The program instructions are configured to cause one or more processors to receive one or more images of the projection mask from the detector assembly and to determine the quality of one or more images of the projection mask.

[0005] U.S. Patent Application Publication 2019 / 0310080 describes an overlay metricing tool that provides site-by-site alignment, comprising a controller coupled to a telecentric imaging system. The controller receives two or more alignment images of overlay targets on a sample acquired by the imaging system at two or more focus positions, generates alignment data indicating the alignment of the overlay targets in the imaging system based on the alignment images, sets the alignment images as measurement images if the alignment of the overlay targets is within a selected alignment tolerance, and instructs the imaging system to adjust the alignment of the overlay targets in the imaging system if the alignment of the overlay targets is outside the selected alignment tolerance, receives one or more measurement images from the imaging system, and then determines the interlayer overlays of two or more layers of the sample 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. The SPM system has a probe adapted to interact with nanoscale features of a sample and scan within a target region to generate a three-dimensional image of that target region, the system maintains positional information of multiple features of interest of the sample according to a sample-specific coordinate system, the SPM system is configured to adjust the positioning of the probe relative to the sample according to the SPM coordinate system, and the SPM system is further configured to manage the 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 offset the determined alignment errors. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] U.S. Patent Application Publication No. 2007 / 0290703 Specification [Patent Document 2] U.S. Patent Application Publication No. 2020 / 0319443 [Patent Document 3] U.S. Patent Application Publication No. 2019 / 0310080 [Patent Document 4] U.S. 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 [Overview of the project]

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

[0009] A first imaging assembly is configured to produce a first image of the measurement site in the sample. A second imaging assembly is coupled with a 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 formed on 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 produce a first image at a magnification of 1 or 2 or more, the optical camera is configured to produce a second image, and the processor is configured to identify the measurement site in the first and second images. In yet another embodiment, the measurement assembly includes one or more X-ray detector assemblies (XDAs), each XDA including a plurality of energy-dispersive X-ray detector assemblies surrounding the measurement site, wherein (i) a first distance between the optical microscope and the measurement site is greater than 50 mm, and (ii) a second distance between the optical camera and the measurement site is less than 25 mm.

[0012] In some embodiments, the processor is configured to align the measurement position with the measurement site based on at least a 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 another embodiment, the optical camera is configured to generate a 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 site, 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 another embodiment, when the measurement site is aligned with the measurement site, the processor is configured to perform an XRF measurement on a structure formed on a semiconductor substrate.

[0014] In some embodiments, (i) based on a first image, the processor is configured to obtain a first positioning error between the measurement site and the measurement position in a first movement, and (ii) based on a second image, the processor is configured to obtain a second positioning error between the measurement site and the measurement position in a 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 one embodiment, at least one of the first movement and the second movement includes multiple movements. In another embodiment, the second movement is smaller than the first movement.

[0016] According to embodiments of the present invention, an additional system is provided, comprising (a) an interface configured to receive (receive) (i) a first signal from a first imaging assembly and (ii) a second signal from a second imaging assembly coupled with a measurement assembly, and (b) a processor, wherein 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 a 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 the step of receiving (receiving) a first signal from a first imaging assembly and a second signal from a second imaging assembly coupled to a measurement assembly. The 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. The measurement is performed at the measurement site.

[0018] The present invention will be more fully understood by reference to the following detailed description of its embodiments in conjunction with the drawings.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic explanatory diagram of a system for fluorescence X-ray (XRF) measurement according to an embodiment of the present invention. [Figure 2] It is a schematic explanatory diagram of a system for fluorescence X-ray (XRF) measurement according to an embodiment of the present invention. [Figure 3] It is a schematic explanatory diagram of an X-ray detector assembly (XDA) and an optical microscope of the system of FIG. 2 above according to an embodiment of the present invention. [Figure 4] It is a flowchart schematically showing a method of performing X-ray measurement and improving navigation accuracy in the systems of FIGS. 1 and 2 above according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0020] (Overview) The very large scale integration (VLSI) manufacturing process of an integrated circuit (IC) usually includes measurements such as X-ray measurement at predefined measurement sites within the IC device to confirm that the manufactured structure meets the design requirements. As the dimensions of the structures within the IC device become smaller, the size of the measurement sites becomes smaller, and thus the requirements for navigation accuracy to enable appropriate measurement at each measurement site increase.

[0021] The embodiments of the present invention described below provide a technique for improving the navigation accuracy of a system configured to perform processes and / or inspections or measurements at specific sites within an IC during and after IC manufacturing. In an embodiment of the present invention, the system includes an X-ray system that is configured to perform X-ray measurements at one or more measurement sites defined on a sample such as a semiconductor substrate (e.g., a wafer) including a plurality of ICs during manufacturing, including but not limited to.

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

[0023] In some embodiments, the X-ray system includes a first imaging assembly configured to generate a first image of the measurement site on the wafer, which in an example of the present invention is an optical microscope (OM). The OM can have at least two magnifications, referred to herein as low magnification and high magnification. The low magnification (e.g., having 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 between about 5x and 20x). Additionally or alternatively, the low magnification objective lens may 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 with a measuring assembly and configured to produce a second image of the measurement site, a camera having a single magnification in the example of the present invention. In this specification and in the claims, the terms “coupled with” and “coupled to” also refer to the camera being integrated with or coupled to the respective measuring assembly.

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

[0026] In some embodiments, the field of view (FOV) of the OM is positioned in the X-ray system at a distance greater than approximately 50 mm, typically about 100 mm, from the measurement position defined by the configuration of the X-ray source and XDA. Furthermore, if the X-ray system comprises two or more X-ray sources and XDAs, the distance between the OM and a given measurement position can be at least 100 mm. Typically, the positioning accuracy of the stage is determined, in particular, by the distance the measurement site moves relative to the measurement position. Therefore, the shorter the stage movement, the better the positioning accuracy, and thus the better the alignment between the measurement position and the measurement site, which is essential for the quality of the X-ray measurement. In this specification and in the claims, the term “quality” of an X-ray measurement means the accuracy (e.g., repeatability) and precision of the measurement results. For example, if different locations are measured (due to errors in positioning accuracy) rather than the same location on the wafer, repeatability is reduced.

[0027] In some embodiments, in the above configuration, the camera's field of view (FOV) has a size of approximately 3 mm x 3 mm, and the center of the FOV is located at a distance of less than approximately 25 mm from the measurement site. In embodiments of the present invention, it is at a distance of approximately 10 mm or 20 mm.

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

[0029] In some embodiments, during wafer processing after stage mapping, the processor is configured to receive the 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 sites using any appropriate technique, such as applying a pattern recognition algorithm to a first image, and to control the OM to use high magnification to acquire and generate a first image of the measurement sites.

[0030] In some embodiments, based on a first image, the processor is configured to control the stage to perform a first move of the wafer so that the measurement area is positioned within the camera's FOV. Note that the first move of the stage has a range of approximately 100 mm (or any other appropriate move) so that the measurement area is typically positioned within the camera's FOV.

[0031] In some embodiments, the processor is configured to control the camera to generate a second image of the measurement area. In such embodiments, the processor can apply a pattern recognition algorithm to identify the measurement area in both the first and second images. The processor is then configured to control the stage to perform a second movement, for example, about 10 mm or 20 mm, so that the measurement area is aligned with the measurement position. Note that, as described above, shortening the stage movement distance, for example to about 10 mm, significantly improves the alignment between the measurement area and the measurement position compared to the alignment achieved with a stage movement of about 100 mm.

[0032] In some embodiments, at least one of the first and second movements includes 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 and the measurement position, the processor is configured to control the measurement assembly to perform X-ray measurements at the measurement site. More specifically, the processor controls the X-ray source to apply an X-ray beam to the measurement site and performs X-ray measurements based on signals received from the SDD in response to the application of the X-ray beam.

[0034] The disclosed technology improves the navigation accuracy and measurement quality of X-ray systems and other systems that perform measurements at predefined measurement sites in the production process of integrated circuits.

[0035] (System description) Figure 1 is a schematic diagram illustrating an X-ray system 20 according to 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 examples of the present invention, the sample includes a semiconductor substrate, referred to herein as wafer 22, having structures such as transistors, diodes, and memory cells of integrated circuit (IC) devices. In this embodiment, system 20 includes an X-ray fluorescence (XRF) system, embodiments relating to the applicant's XRF system are described in detail, for example, in U.S. Patents 6,108,398 and 9,632,043.

[0037] In some embodiments, the system 20 includes an X-ray source 24, an X-ray tube in the example of the present invention, 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 an X-ray optical system 28 aligned with the X-ray source 24 in the XYZ coordinate system of the system 20. The X-ray optical system 28 is configured to focus the X-ray beam onto a small area referred to herein as a measurement position (MP) 30, for example, a spot on the surface of a wafer 22 having a diameter typically between about 10 μm and 20 μm, but which can be about 100 μm in some applications.

[0038] In this specification and in the claims, the terms “about” or “approximately” with respect to any number or range indicate a suitable dimensional tolerance that enables the component or assembly of the building to function for the intended purpose as described herein.

[0039] In some embodiments, the system 20 comprises an integrated optical inspection system, also referred herein as the first imaging assembly or optical microscope (OM) 50, configured to generate an image of the surface of the wafer 22 at position 27. In embodiments of the present invention, the 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 the wafer 22 at position 27. In embodiments of the present invention, the position of the OM 50 determines the distance 25 between position 27 and MP 30, for example, the distance 25 is greater than about 50 mm and typically about 100 mm.

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

[0041] In some embodiments, the measurement assembly 35 includes one or more sets of suitable detectors, such as solid energy dispersive X-ray detectors, and in the examples of the present invention, the solid energy dispersive X-ray detectors include silicon drift detectors (SDDs) 32, such as SDDs supplied by Bruker Corporation (Massachusetts 01821, USA) or SDDs from any other suitable SDD supplier, such as Amptek Inc. (Massachusetts 01730, USA) and KETEK GmbH (Munich, 81737, Germany). Each set of SDDs 32 is placed in the respective X-ray detector assembly (XDA) 31.

[0042] Here, refer to inset 29 showing a bottom view of the measuring assembly 35. In an embodiment of the present invention, the measuring assembly 35 includes a single XDA 31 with four SDDs 32 arranged in a predetermined geometric shape surrounding the projection of the position of MP 30 on the XY plane (defined by the XYZ coordinate system) of the measuring assembly 35.

[0043] Now, let us return to and refer to the overall diagram of System 20. In some embodiments, System 20 includes a second imaging assembly, a camera 33 in the example of the present invention, which is coupled with the measuring assembly 35. For example, the camera 33 is integrated with the measuring assembly 35, for example, when manufacturing the measuring assembly 35 of System 20. Note that the camera 33 is not typically directly coupled to either of the SDDs 32, but both the camera 33 and the SDDs 32 are coupled to a common support structure (e.g., a plate) of the measuring assembly 35 and are electrically connected to an external entity (such as a processor, described later) via electrical leads or traces for exchanging signals between them.

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

[0045] In an alternative embodiment, the camera 33 can be positioned in the system 20 at a suitable location (for generating an image of 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 configurations of the measuring assembly 35, XDA 31, and camera 33 are provided as examples. In other embodiments, the measuring assembly 35 may 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. Furthermore, the measuring assembly 35 may have any suitable number of imaging assemblies coupled together, arranged in addition to or in place of the camera 33 using any suitable configuration.

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

[0048] In some embodiments, during a system calibration step performed before measurement, the processor 34 is configured to map the movable stage 40 to improve the intrinsic positioning accuracy of the stage. For example, after stage mapping, the positioning error of the stage 40 is between approximately 3 μm and 6 μm when the stage 40 moves approximately 100 mm, and between approximately 0.3 μm and 0.6 μm when the stage 40 moves approximately 10 mm. In this specification and in the claims, the term “positioning error” means the offset in the XY plane between the intended position and the actual position of a selected portion of the wafer 22 relative to a reference position of the system 20 (measured in units of distance, e.g., millimeters). In some cases, the positioning error is not constant and will vary across the XY plane of the stage 40.

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

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

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

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

[0053] In some embodiments, after aligning the measurement site with the MP30, the processor 34 is configured to control the X-ray source 24 and the measurement assembly 35 to perform X-ray measurement at the measurement site.

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

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

[0056] In alternative embodiments, the disclosed technology can be used with modifications in other types of suitable measurement and inspection systems, such as optical-based, non-XRF X-ray-based, electron beam-based, and ion beam-based systems. Furthermore, the disclosed technology can be used with modifications in other types of systems configured to perform local operations other than measurement. For example, a system designed for probing processes, local deposition processes, local etching and / or drilling processes performed on any suitable sample, not limited to semiconductor substrates.

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

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

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

[0060] In an alternative embodiment, the system 10 has two different stages 40, and therefore, based on the technique described in Figure 1 above, the system 10 is configured to perform X-ray measurements simultaneously on two wafers 22. In addition or alternatively, the system 10 may have two OMs 50 (i.e., separate OMs for each channel) so that the first step of the navigation process (i.e., generating a first image using the OMs 50) can be performed simultaneously on both wafers 22.

[0061] These specific configurations of systems 10 and 20 are shown as examples to illustrate certain problems, such as positioning errors, that are addressed by embodiments of the present invention, and to demonstrate the applicability of these embodiments in improving 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 can similarly be applied to other types of measurement systems known in the art.

[0062] Figure 3 is a schematic diagram illustrating the measurement assemblies 35a and 35b of the system 10 shown in Figure 2, according to an embodiment of the present invention.

[0063] In some embodiments, the measuring assembly 35a comprises an XDA 31a having four SDDs 32 and a camera 33a such as the camera 33 in Figure 1, and is coupled to the measuring assembly 35a in a fixed position relative to the projection of the MP 30.

[0064] In some embodiments, a measuring assembly 35b having a similar structure to measuring assembly 35a comprises an XDA 31b having four SDDs 32 and a camera 33b similar to the camera 33a of measuring assembly 35a. The camera 33b is coupled to the measuring assembly 35b in a fixed position relative to the projection of MP 30.

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

[0066] In the example shown in Figure 3, the measurement assemblies 35a and 35b are positioned approximately 120 mm apart from each other, allowing sufficient space between them for positioning the OM50. In other embodiments, the OM50 can be mounted on the system 10 at any other suitable location, and thus the measurement assemblies 35a and 35b can be positioned at any other suitable distance from each other. Note that the distance between the X-ray channels can be configured and determined based on the size of the wafer 22 and the user's sampling mechanism of the system 10, and that two X-ray measurements on the wafer 22 (or on different wafers 22 in the embodiments described above) can be performed simultaneously.

[0067] The configuration, shape, and dimensions of the measuring assemblies 35a and 35b and their components are provided as examples. In other embodiments, the measuring assemblies 35a and 35b may have any other suitable configuration, which may be similar to or different from each other, and may have the same components or any other suitable components in addition to or instead of the components shown in Figures 1 and 3.

[0068] Figure 4 is a flowchart illustrating a method for improving navigation accuracy by performing X-ray measurements in an X-ray system 20 according to an embodiment of the present invention. This method can also be applied when performing X-ray measurements in the system 10 shown in Figure 2, with necessary modifications.

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

[0070] In the measurement site selection step 102, the processor 34 receives a list of measurement sites, selects a measurement site from the list, moves the wafer 22 (using the stage 40) to the coordinates of the selected measurement site in order to align the selected measurement site with the OM50, so that the measurement site is positioned within the FOV of the OM50, as described in detail in Figure 1 above.

[0071] In the first image generation step 104, the processor 34 generates a first image of the measurement area based on the image signal received from the OM50 and identifies the measurement area in the first image, as described in detail in Figure 1 above. In some embodiments, the processor 34 is configured to calculate the distance between the identified measurement area and the center of the field of view (FOV) of the OM50, which, among other things, indicates the positioning error of the stage 40.

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

[0073] In the first moving step 106, the processor 34 controls the stage 40 to move the wafer 22 by approximately 100 mm to position the measurement area aligned with the camera 33 coupled to the measurement assembly 35 (for example, 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 a stage mapping (also referred to herein as stage mapping) of the stage 40 to improve the positioning accuracy of the stage 40.

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

[0076] In some embodiments, the processor 34 is configured to calculate the placement error of the stage 40 based on the calculated distance between the measurement site and the FOV center 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, the processor 34 controls the stage 40 to correct the calculated error and move the wafer 22 to position the measurement area at the center of the camera 33's FOV. Note that in other embodiments, the movement of the wafer 22 to position the measurement area at the center of the camera 33's FOV can be considered a separate step of the method.

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

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

[0080] In decision step 114, the processor 34 checks whether or not to perform an X-ray measurement at another measurement site on the wafer 22. If another measurement is required, the method loops back to step 102.

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

[0082] The method shown in Figure 4 is provided as an example and can be modified and used in other processes, such as measurements on a semiconductor wafer or measurements on other suitable substrates having one or more measurement sites.

[0083] The embodiments described above are cited as examples, and it will be understood that the appended claims are not limited to those specifically shown and described herein. Rather, the scope includes both combinations and partial combinations of the various features described herein, as well as variations and modifications thereof not disclosed in the prior art, which would be recalled by those skilled in the art upon reading the foregoing. Documents incorporated by reference in this patent application of the present invention are considered integral parts of this application, except that, insofar as terms are defined in those incorporated documents in a manner that contradicts the definitions made herein, only the definitions herein should 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 Interfaces 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