WO2020104031A1

WO2020104031A1 - Method for critical dimension measurement on a substrate, and apparatus for inspecting and cutting an electronic device on the substrate

Info

Publication number: WO2020104031A1
Application number: PCT/EP2018/082230
Authority: WO
Inventors: Bernhard G. Mueller
Original assignee: Applied Materials, Inc.
Priority date: 2018-11-22
Filing date: 2018-11-22
Publication date: 2020-05-28
Also published as: KR102641280B1; CN113169084A; JP7192117B2; JP2022509103A; TWI813795B; TW202037907A; KR20210088720A

Abstract

A method and apparatus for critical dimension measurement on a substrate is described. The method includes supporting the substrate with a major surface of the substrate being in an X-Y plane, cutting a notch with a focused ion beam column angled relative to a plane of the major surface of the substrate under a first angle, measuring at least one of a first dimension and a second dimension of one or more structures adjacent to the notch with a first imaging charged particle beam microscope having an optical axis angled relative to the plane of the major surface of the substrate under a second angle different from the first angle, the first dimension and the second dimension being in the X-Y plane and are measured to scale; and measuring a third dimension of the one or more structures to scale in a direction angled relative to the X-Y plane with the first imaging charged particle beam microscope having the optical axis.

Description

METHOD FOR CRITICAL DIMENSION MEASUREMENT ON A SUBSTRATE, AND APPARATUS FOR INSPECTING AND CUTTING AN ELECTRONIC

DEVICE ON THE SUBSTRATE

FIELD

[0001] The present disclosure relates to an apparatus and a method for inspecting a substrate. Further, embodiments of the present disclosure generally relate to a focused ion beam system for analyzing electronic devices, for example on large area substrates. More particularly, embodiments described herein relate a method for automated critical dimension (CD) measurements on substrates for display manufacturing, such as large area substrates. Particularly, embodiments relate to a method for automated critical dimension measurement on a substrate for display manufacturing, a method of inspecting a large area substrate for display manufacturing, and apparatus for inspecting a large area substrate for display manufacturing, and a method of operating thereof.

BACKGROUND

[0002] Electronic devices, such as TFTs, photovoltaic (PV) devices or solar cells and other electronic devices have been fabricated on large area substrates, such as display glass panels, and thin, flexible media, for many years. The substrates may be made of glass, polymers, or other material suitable for electronic device formation. There is an ongoing effort directed to fabricating the electronic devices on substrates having a surface area much greater than one square meter, such as two square meters, or larger, to produce an end product of a larger size and/or decrease fabrication costs per device (e.g., pixel, TFT, photovoltaic or solar cell, etc.).

[0003] There is often a need to analyze a discrete device that has been determined as being defective, such as a TFT. For example, a transistor that switches an individual pixel may be defective, which causes that pixel to be always on or always off. [0004] Focused ion beam (FIB) systems have been utilized as an analytical technique in the semiconductor industry, materials science and increasingly in the biological field. In the semiconductor industry, FIB systems use a beam of ions for site-specific analysis of a portion of a die on a wafer (e.g., a“sample”).

[0005] Further, in many applications, a substrate is inspected to monitor the quality of the substrate. For example, glass substrates on which layers of coating material are deposited are manufactured for the display market. Since defects may e.g. occur during the processing of the substrates, e.g. during the coating of the substrates, an inspection of the substrate for reviewing the defects and for monitoring the quality of the displays is necessary. Additionally, the size, shape and relative location of structures created by any patterning process step needs to be monitored and controlled by SEM review, for example the measurement of critical dimensions (CD).

[0006] Displays are often manufactured on large area substrates with continuously growing substrate sizes. Further, displays, such as TFT-displays, are subject to continuous improvement. The inspection of the substrate can be carried out by an optical system. However, critical dimension (CD) measurements, for example, of structures of a TFT- array, require a resolution that cannot be provided with optical inspection. A CD measurement can for example provide the size of the structure or distances between structures in a range of some ten nanometers. The resulting dimension can be compared to a desired dimension, wherein the dimension can be considered critical for evaluating the properties of the manufacturing process.

[0007] Substrates for display manufacturing are typically glass substrates having an area of, for example, 1 m² or above. High resolution images on such large substrates are very challenging per se, and most findings from the wafer industry are not applicable. Further, the options for CD measurement, which are exemplarily described above, are not suitable for large area substrates since, for example, the resulting throughput would be undesirable.

[0008] Accordingly, given e.g. the increasing demands on the quality of displays on large area substrates, there is a need for an improved apparatus and method for inspecting large area substrates, for example, particularly a method and apparatus where FIB techniques can be utilized for large area substrates, and more particularly to be utilized for critical dimension measurements.

SUMMARY

[0009] In light of the above, a method for critical dimension measurement on a substrate for display manufacturing, a method of inspecting a large area substrate for display manufacturing, an apparatus for inspecting a large area substrate for display manufacturing, and a method of operating thereof are provided. Further aspects, advantages and features of the present disclosure are apparent from the description and the accompanying drawings.

[0010] According to one aspect, a method for critical dimension measurement on a substrate is provided. The method includes supporting the substrate with a major surface of the substrate being in an X-Y plane, cutting a notch with a focused ion beam column angled relative to a plane of the major surface of the substrate under a first angle, measuring at least one of a first dimension and a second dimension of one or more structures adjacent to the notch with a first imaging charged particle beam microscope having an optical axis angled relative to the plane of the major surface of the substrate under a second angle different from the first angle, the first dimension and the second dimension being in the X-Y plane and are measured to scale; and measuring a third dimension of the one or more structures to scale in a direction angled relative to the X-Y plane with the first imaging charged particle beam microscope having the optical axis.

[0011] According to another aspect, an apparatus for inspecting a substrate and cutting an electronic device on the substrate is provided. The apparatus includes a vacuum chamber, a stage arranged in the vacuum chamber and configured to support the substrate having the electronic device thereon, a focused ion beam column over the stage, the focused ion beam column having beam path angled at a first angle relative to a plane of a major surface of the substrate, and a first imaging charged particle beam microscope adjacent to the focused ion beam column and having the optical axis angled at a second angle relative to the plane of the major surface of the substrate, the second angle being different from the first angle, the second angle being configured to reduce optical distortion, and the first angle being configured to allow for critical dimension measurement to scale along three dimensions of the electronic device.

[0012] According to another aspect, a method for critical dimension measurement on a substrate is provided. The method includes imaging one or more structures provided on the substrate with a scanning charged particle beam device to obtain an image, an imaging plane of the scanning charged particle beam device being parallel to a major surface of the substrate and the image includes a notch generated in the substrate, and measuring critical dimensions to scale at the image along three different directions of a three dimensional coordinate system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] So that the manner in which the above recited feature of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, may admit to other equally effective embodiments. A full and enabling disclosure to one of ordinary skill in the art is set forth more particularly in the remainder of the specification including reference to the accompanying drawings wherein:

FIG. 1 shows a side view of an apparatus for inspecting a substrate, according to embodiments described herein;

FIG. 2 is a schematic sectional view of a metrology system apparatus for inspecting a substrate according to embodiments described herein;

FIG. 3 shows a side view of a typical arrangement of inspecting a sample in a metrology system having a focused ion beam column (FIB column);

FIG. 4A shows a side view of an arrangement of inspecting a sample in a metrology system having a focused ion beam column according to embodiments of the present disclosure; FIG. 4B shows an image of an apparatus for inspecting a system corresponding to FIG. 4A;

FIG. 5 shows a side view of an apparatus for inspecting a substrate according to embodiments described herein and having FIB column, wherein the apparatus includes components for reducing vibrations;

FIG. 6 shows a side view of an imaging charged particle beam microscope, i.e. an exemplary apparatus for inspecting a substrate, according to embodiments described herein; and

FIG. 7 shows a flow chart illustrating a method of automated CD measurement on a large area substrate, e.g. for display manufacturing, according to embodiments of the present disclosure.

DETAILED DESCRIPTION

[0014] Reference will now be made in detail to the various exemplary embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not meant as a limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet further embodiments. The intention is that the present disclosure includes such modifications and variations.

[0015] Within the following description of the drawings, the same reference numbers refer to the same components. Only the differences with respect to the individual embodiments are described. The structures shown in the drawings are not necessarily depicted true to scale but rather serve the better understanding of the embodiments.

[0016] According to some embodiments, which can be combined with other embodiments described herein, substrates described herein relate to large area substrates, in particular large area substrates for the display market. According to some embodiments, large area substrates or respective substrate supports may have a size of at least 1 m², such as at least 1.375 m². The size may be from about 1.375 m² (1100 mm x 1250 mm- Gen 5) to about 9 m², more specifically from about 2 m² to about 9 m² or even up to 12 m². The substrates or substrate receiving areas, for which the structures, apparatuses, and methods according to embodiments described herein are provided, can be large area substrates as described herein. For instance, a large area substrate or carrier can be GEN 5, which corresponds to about 1.375 m² substrates (1.1 m x 1.25 m), GEN 7.5, which corresponds to about 4.39 m² substrates (1.95 m x 2.25 m), GEN 8.5, which corresponds to about 5.7m² substrates (2.2 m x 2.5 m), or even GEN 10, which corresponds to about 9 m² substrates (2.88 m x 3130 m). Even larger generations such as GEN 11 and GEN 12 and corresponding substrate areas can similarly be implemented. It has to be considered that the substrate size generations provide fixed industry standards even though a GEN 5 substrate may slightly deviate in size from one display manufacturer to another display manufacturer. Embodiments of an apparatus for testing may for example have a GEN 5 substrate support or GEN 5 substrate receiving area such that GEN 5 substrates of many display manufacturers may be supportable by the support. The same applies to other substrate size generations.

[0017] Yet, a person skilled in the art will appreciate that one or more of the advantages described in the present disclosure may also be applicable in semiconductor industry, for which wafers, for example silicon wafers, are utilized as substrates. Accordingly, embodiments of the present disclosure, may be provided for substrates and fields of application handling wafers, such as semiconductor wafer processing.

[0018] Electron beam review (EBR) for large area substrates, wherein the entire substrate or areas distributed over the entire substrate are measured is a comparably young technology. Resolutions of, for example, 20 nm or below, such as 10 nm or below are very challenging to achieve and previous findings from wafer imaging may not be suitable in light of the significant difference in substrate sizes. A simple upscaling cannot be successful, for example, due to the desired throughput. Yet further, processes and apparatuses are beneficially suitable to reduce vibrations on large dimensions below the desired resolution. Yet further, manual or semi- automated processes may also not be suitable in light of the desired throughput as well as the repeatability of measuring positions distributed over the area of the large area substrate.

[0019] Processing or testing the entire substrate or areas distributed over the entire substrate, i.e. without breaking the glass, is particularly challenging in view of the large sizes of the substrates which are produced and processed in current display manufacturing technology. Since the sizes of substrates, e.g. large area substrates, are consistently increasing, larger vacuum chambers are utilized for processing or imaging the substrates. However, larger vacuum chambers are more sensitive to unwanted vibrations compared to smaller chambers. The vibration or the vibrations of the vacuum chamber limit the resolution with which the substrates can for example be inspected. In particular, critical dimensions having sizes below the resolution of an inspection system will remain invisible and thus cannot be measured.

[0020] According to embodiments of the present disclosure, a method for critical dimension measurement on a substrate is provided. The method includes supporting the substrate with a major surface of the substrate being in an X-Y plane and cutting a notch with a focused ion beam column angled relative to a plane of the major surface of the substrate under a first angle. At least one of a first dimension and a second dimension of one or more structures at the notch are measured with a first imaging charged particle beam microscope angled relative to the plane of the major surface of the substrate under a second angle different from the first angle, the first dimension and the second dimension being in the X-Y plane and are measured to scale. A third dimension of the one or more structures are measured to scale with the first imaging charged particle beam microscope having the optical axis. The third dimension of the one or more structures can be measured to scale in a direction angled relative to the X-Y plane with the first imaging charged particle beam microscope having the optical axis. For example, the third direction can be a Z-direction. X, Y, and Z may define a three dimensional coordinate system.

[0021] Measuring three dimensions to scale, for example dimensions along a Cartesian coordinate system (X, Y, and Z), can result in a reduced or zero scaling error. A correction calculation error can be avoided. Yet further, additionally or alternatively , since all dimensions are measured in one image, the throughput of an inspection system can be increased and/or image charging or image carbonization can be reduced. Accordingly, higher precision of the critical dimension measurement can be provided, particularly for the relation between X, Y, and Z. For example, the image can be an image of an area including a notch cut by a FIB. [0022] FIG. 1 shows a side view of an apparatus for inspecting a substrate, according to embodiments described herein. The apparatus 100 includes a vacuum chamber 120. The apparatus 100 further includes a substrate support 110 on which a substrate 160 may be supported. The apparatus 100 includes a first imaging charged particle beam microscope 130. Further, the apparatus may include a second imaging charged particle beam microscope 140. In the example shown in FIG. 1, the first imaging charged particle beam microscope 130 and the second imaging charged particle beam microscope 140 are arranged above the substrate support 110.

[0023] As further shown in FIG. 1, the substrate support 110 extends along the x-direction 150. In the drawing plane of FIG. 1, the x-direction 150 is a left-right direction. A substrate 160 is disposed on the substrate support 110. The substrate support 110 is movable along the x-direction 150 to displace the substrate 160 in the vacuum chamber 120 relative to the first imaging charged particle beam microscope 130 and the second imaging charged particle beam microscope 140. Accordingly, an area of the substrate 160 can be positioned below the first imaging charged particle beam microscope 130 or below the second imaging charged particle beam microscope 140 for CD measurement. The area may include a structure for CD measurement contained in or on a coated layer on the substrate. According to embodiments of the present disclosure, a focused ion beam column (see for example FIGS. 2 and 5) is provided. A notch can be generated in a coated layer on the substrate, for example an electronic device such as TFT provided on the substrate. The substrate support 110 may also be movable along a y-direction (not shown) so that the substrate 160 can be moved along the y-direction, as discussed below. By suitably displacing the substrate support 110 holding the substrate 160 within the vacuum chamber 120, the entire extent of the substrate 160 may be measured inside the vacuum chamber 120. According to embodiments of the present disclosure, particularly for large area substrates, a stage for supporting the substrate can be limited to a movement in X- direction, Y-direction, and Z-direction and a rotating in the X-Y plane.

[0024] The first imaging charged particle beam microscope 130 is distanced from the second imaging charged particle beam microscope 140, e.g. along the x-direction 150 by a distance 135. In the embodiment illustrated in FIG. 1, the distance 135 is a distance between a center of the first imaging charged particle beam microscope 130 and a center of the second imaging charged particle beam microscope 140. In particular, the distance 135 is a distance, along the x-direction 150, between a first optical axis 131 defined by the first imaging charged particle beam microscope and a second optical axis 141 defined by the second imaging charged particle beam microscope 140. The first optical axis 131 and the second optical axis 141 extend along a z-direction 151. The first optical axis 131 may for example be defined by the objective lens of the first imaging charged particle beam microscope 130. Similarly, the second optical axis 141 may for example be defined by the objective lens of the second imaging charged particle beam microscope 140.

[0025] As further shown in FIG. 1, the vacuum chamber 120 has an inner width 121 along the x-direction 150. The inner width 121 may be a distance obtained when traversing the vacuum chamber 120 along the x-direction from left-hand wall 123 of the vacuum chamber 120 to right-hand wall 122 of the vacuum chamber 120. An optional aspect of the disclosure relates to the dimensions of the apparatus 100 with respect to the e.g. x-direction 150, particularly for embodiments for which SEM image is obtained on a large area substrate. According to embodiments, the distance 135 along the x-direction 150 between the first imaging charged particle beam microscope 130 and the second imaging charged particle beam microscope 140 may be at least 30 cm, such as at least 40 cm. According to further embodiments, which can be combined with other embodiments described herein, the inner width 121 of the vacuum chamber 120 may lie in the range from 250% to 450% of the distance 135 between the first imaging charged particle beam microscope 130 and the second imaging charged particle beam microscope 140. Accordingly, a high-resolution image for critical dimension measurement can be provided.

[0026] An advantage of having a vacuum chamber with reduced dimensions, as provided by some embodiments described herein, is that one or more vibrations of the vacuum chamber may be reduced, since the level of vibration increases as a function of the size of the vacuum chamber. Accordingly, the vibration amplitude of the substrate may be advantageously reduced as well.

[0027] According to some embodiments, which can be combined with other embodiments described herein, and apparatus for inspecting a large area substrate may further include a controller 180. The controller 180 can be connected (see reference numeral 182) to the substrate support 110, and particularly a displacement unit of the substrate support. Further, the controller 180 can be connected to a scanning deflector assembly 184 of an imaging charged particle beam microscope, such as the first imaging charged particle beam microscope 130 and the second imaging charged particle beam microscope 140.

[0028] The controller 180 comprises a central processing unit (CPU), a memory and, for example, support circuits. To facilitate control of the apparatus for inspecting a large area substrate, the CPU may be one of any form of general purpose computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The memory is coupled to the CPU. The memory, or a computer readable medium, may be one or more readily available memory devices such as random access memory, read only memory, floppy disk, hard disk, or any other form of digital storage either local or remote. The support circuits may be coupled to the CPU for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry and related subsystems, and the like. Inspecting process instructions and/or instructions for generating a notch in an electronic device provided on the substrate are generally stored in the memory as a software routine typically known as a recipe. The software routine may also be stored and/or executed by a second CPU (not shown) that is remotely located from the hardware being controlled by the CPU. The software routine, when executed by CPU, transforms the general purpose computer into a specific purpose computer (controller) that controls the apparatus operation such as that for controlling inter alia the substrate support positioning and charged particle beam scanning during the imaging process. Although the method and/or process of the present disclosure is discussed as being implemented as a software routine, some of the method steps that are disclosed therein may be performed in hardware as well as by the software controller. As such, the embodiments may be implemented in software as executed upon a computer system, and hardware as an application specific integrated circuit or other type of hardware implementation, or a combination of software and hardware. The controller may execute or perform a method for critical dimension measurement on a substrate according to embodiments of the present disclosure.

[0029] An imaging charged particle beam microscope, as used herein, may be adapted for generating a low-energy charged particle beam having a landing energy of 2 keV or below, particularly of 1 keV or below. Compared to high-energy beams, low energy beams do not impact or deteriorate a display backplane structure during critical dimension measurements. According to yet further embodiments, which can be combined with other embodiments described herein, the charged particle energy, for example the electron energy, can be increased to 5 keV or above, such as 10 keV or above between the particle beam source and the substrate. Accelerating the charged particles within the column reduces interaction between the charged particles, reduces aberrations of electro-optical components, and, thus, improves the resolution of the imaging scanning charged particle beam microscope.

[0030] Figure 2 is a schematic sectional view of a metrology system 200. The metrology system 200 includes a vacuum chamber 205 having a stage or substrate support 110 described in FIG. 1 therein. The stage or substrate support 110 supports the large area substrate having an electronic device (not shown) thereon. The vacuum chamber 205 is fluidly coupled with a vacuum pump 210 that maintains a negative pressure in the vacuum chamber 205. The FIB column 145 and the imaging charged particle beam microscope 130 are at least partially positioned in the vacuum chamber 205 above the stage, i.e. substrate support 110. The metrology system 200 also includes a secondary electron detector 215. The secondary electron detector 215 is utilized for imaging during cutting of the electronic device using the FIB column 145.

[0031] Contrary to conventional LAB SEMs having a FIB column, which are explained with respect to the example shown FIG. 3, embodiments of the present disclosure provide one or more measuring charged particle beam microscopes, which are oriented with an optical axis substantially perpendicular to a major surface of the substrate. Further, a focused ion beam (FIB) column is oriented at a first angle, being about 45°.

[0032] For conventional LAB SEMS having a FIB column, as exemplarily shown in FIG. 3, typically a sample or substrate 160 is tilted with respect to an imaging charged particle beam microscope 130. The substrate can be tilted at an arbitrary angle. For example, it is advantageous to have the FIB column perpendicular to a major surface of the substrate (see reference numeral 345) since surfaces of a notch cut with the focused ion beam are smooths at 360° around a center of the focused ion beam. A charged particle beam 330 is typically guided along an optical axis (disregarding scanning deflection) being perpendicular to the surface 307 of the notch to be inspected with the microscope. Accordingly, the dimension 306 of the structure 305 can be measured. However, in order to obtain the thickness of the layer of the structure 305 the correction is applied in light of the FIB cutting angle, which may, for example, be 30°. Further, in light of the arbitrary substrate inclination, a correction based on the SEM observation angle may also be required.

[0033] Yet further, tilting of the substrate 160 results in a distortion, i.e. an optical distortion, of the measured dimension 302 of the structure 301 and the measured dimension 304 of the structure 303, because the structures are not in the image plane 335 of the microscope. Accordingly, typical LAB SEMs having an FIB column require correction calculation, which results in an increased measurement error due to the angles. The distortion due to the image depth perspective is further difficult to correct.

[0034] Fig. 4A illustrates embodiments of a method for critical dimension measurement on a substrate and an apparatus for inspecting a substrate according to embodiments of the present disclosure. A substrate 160 is substantially perpendicular to an optical axis of an imaging charged particle beam microscope 130. Further, a cutting angle of a focused ion beam column indicated by arrow 445 is approximately 45°. For example, the cutting angle can be about 42° to about 48°. According to embodiments, which may be combined with other embodiments, a focused ion beam column can be provided over the stage. The focused ion beam column has beam path angled at a first angle relative to a plane of a major surface of the substrate, wherein the angle may, for example, be about 42° to about 48°.

[0035] According to embodiments of the present disclosure, it is possible to measure in X- dimension, Y-dimension, and Z-dimension without any scaling error in one single SEM image. Accordingly, a scaling error can be reduced or avoided, no correction calculation errors are incurred, the throughput can be increased, and/or generally improve precision for critical dimensioning, particularly between X, Y, Z, can be provided. Typically, the first angle provided by a cutting angle of the FIB relative to the major surface of the substrate and the second angle provided by the optical axis relative to the major surface of the substrate are fixed.

[0036] With respect to FIG. 4B, showing an exemplary image of an imaging charged particle beam microscope of an electronic device having one or more structures, critical dimension“d” is drawn to scale due to the cut angle of 45°. Further, critical dimension“e” an critical dimension“f’ are drawn to scale due to the top-down image of the microscope.

[0037] According to yet further embodiments, which can be combined with other embodiments described herein, for example the critical dimension“e” can be compared to the predetermined dimension or desired dimension of the structure, i.e. the dimension intended during manufacturing of the electronic device. A method for critical dimension measurement, may determine the desired dimension. The measured dimension“e” can be compensated with the desired dimension“e”, resulting in a compensation factor. The measured dimension“d” may be corrected and/or calibrated with the compensation factor. According to some embodiments, a relation between the a first dimension measure along a major surface of the substrate and a third dimension measured along a dimension perpendicular to the major surface can be evaluated.

[0038] According to some embodiments, which can be combined with other embodiments described herein, a method for critical dimension measurement may include obtaining one image. For example, the one image can be provided by one or more frames. The first dimension (in X-direction), a second dimension (in Y-direction), and a third dimension (in z-direction) are measured from the one image and are measured to scale. For example, the third dimension is perpendicular or has an angle different than 0° relative to a plane defined by the first dimension in the second dimension, e.g. X-Y plane.

[0039] According to yet further embodiments, a critical dimension can be measured by an intensity signal of signal electrons.

[0040] According to embodiments, which may be combined with other embodiments described herein, a method for critical dimension measurement on a substrate is provided. The method includes imaging one or more structures provided on the substrate with a scanning charged particle beam device to obtain an image, an imaging plane of the scanning charged particle beam device being parallel to a major surface of the substrate and the image includes a notch generated in the substrate, and measuring critical dimensions to scale at the image along three different directions of a three dimensional coordinate system. The three different directions may include a first direction, a second direction and a third direction, the first direction and the second direction defining a plane parallel to the major surface, for example an X-Y plane, of the substrate and the third direction being angled relative to the plane, particularly about perpendicular to the plane. The third direction may be a z-direction, for example of a Cartesian coordinate system.

[0041] According to some embodiments, which can be combined with other embodiments described herein, the measured critical dimensions are measured to scale and include at least one of a first dimension and a second dimension of one or more structures adjacent to the notch and a third dimension, the third dimension being a layer thickness. The layer thickness may be the thickness of the structure 405 shown in FIG. 4A. The layer thickness as well as critical dimensions parallel to a major surface of the substrate can be measured to scale. According to some embodiments, which can be combined with other embodiments described herein, a depth of focus of the image may larger than 5 pm and/or smaller than 30 pm.

[0042] FIG. 5 shows another example of an apparatus for inspection of the large area substrate. For example, in the apparatus shown in FIG. 2, the first imaging charged particle beam microscope 130 and the second imaging charged particle beam microscope 140 extend along the z-direction i.e. perpendicularly to the x-direction and to the y-direction, wherein the x-y plane is parallel to the substrate support 110. The FIB column 145 can be provided at an angle relative to a major surface of the substrate which is different as compared to the angle of the optical axis. According to embodiments, which may be combined with other embodiments described herein, the angle of the FIB column relative to a major surface of the substrate or the substrate support (the plane of the substrate support, X-Y-plane) may be 42° to 48°.

[0043] FIG. 5 shows a side view of an apparatus for inspecting a substrate, according to embodiments described herein. The apparatus includes a displacement unit 410. The displacement unit 410 is adapted for displacing the substrate support along a first direction, e.g. along the x-direction 150 to position the substrate support 110 in below the first imaging charged particle beam microscope 130 and/or below the second imaging charged particle beam microscope 140. The displacement unit 410 may be adapted for moving the substrate support 110 forward and backward along the x-direction 150, i.e. toward the right and toward the left in FIG. 5. According to embodiments, which can be combined with other embodiments described herein, the apparatus described herein further includes a displacement unit, such as e.g. displacement unit 410 shown in FIG. 5. The displacement unit may be adapted for displacing the substrate support along the first direction. The displacement unit 410 may e.g. include a plurality of linear actuators (not shown) on which the substrate support 110 rests. Alternatively or additionally, the displacement unit may e.g. include a magnetic guiding system (not shown) for guiding the substrate support 110 along the x-direction 150. In the schematic representation shown in FIG. 5, the displacement unit 410 is arranged in the vacuum chamber 120.

[0044] The displacement unit may be adapted for displacing the substrate support along the first direction from a position proximate to a first end or wall of the vacuum chamber to a position proximate second end or wall of the vacuum chamber. The displacement unit may have a displacement range along the first direction, wherein the displacement unit may be adapted for displacing the substrate support to an arbitrary target coordinate within the displacement range.

[0045] The apparatus shown in FIG. 5 may further include a further displacement unit (not shown) adapted for displacing the substrate support 110 in the vacuum chamber 120 along the y-direction 152. The displacement unit 410 and the further displacement unit may form a common displacement system adapted for moving the substrate support 110 in an x-y plane. Accordingly, by suitably moving the substrate support 110 holding the substrate in the x-y plane, any area of a substrate disposed on the substrate support 110 may be positioned below the first imaging charged particle beam microscope 130 or below the second imaging charged particle beam microscope 140 for CD measurement of the target portion. The substrate support may be mounted onto the further displacement unit or on a common displacement system formed by the displacement unit and the further displacement unit. The further displacement unit may be adapted for displacing the substrate support relative to the first imaging charged particle beam microscope and/or relative to the second imaging charged particle beam microscope. The further displacement unit may have a displacement range along the first direction, wherein the displacement range may lie in the range from 150% to 180% of the substrate width or the respective width of the substrate receiving area. The vacuum chamber may have a first inner dimension along the first direction of 150% to 180% of the first receiving area dimension along the first direction. [0046] The apparatus 100 shown in FIG. 5 further includes a vacuum pump 420 adapted for generating a vacuum in the vacuum chamber 120. The vacuum pump 420 is fluidly coupled to the vacuum chamber 120 via connection 430, e.g. a conduit, wherein the connection 430 connects the vacuum pump 420 with the vacuum chamber. Via the connection 430, the vacuum pump 420 may evacuate the vacuum chamber. Accordingly, a pressure of e.g. 10 ¹ mbar or below may be provided in the vacuum chamber. During operation, the vacuum pump 420 may vibrate. Via the connection 430, which is attached to the vacuum pump 420 and to the vacuum chamber 120, mechanical vibrations of the vacuum pump 420 may be transmitted to the vacuum chamber 120. Accordingly, undesired vibrations may be transmitted to the vacuum chamber 120 and/or to a substrate (not shown) positioned on the substrate support 110. To dampen vibration of the vacuum pump 420, a vibration damper 431 is included in the apparatus 100, more particularly in the connection 430. As shown, the vibration damper 431 is coupled to the vacuum pump 420 via a first coupling 432 and to the vacuum chamber 120 via a second coupling 433.

[0047] FIG. 5 further shows a vibration sensor 450 adapted for measuring the vibration of the vacuum chamber 120. For example, the vibration sensor may be adapted for measuring amplitudes and/or frequencies of the vibrations of the vacuum chamber 120. The vibration sensor 450 may further be adapted for measuring vibrations in one or more directions. The vibration sensor 450 may include an optical source (not shown) adapted for generating an optical beam. The optical beam may be directed onto the vacuum chamber 120, for example onto a wall of the vacuum chamber 120, wherein at least part of the optical beam may be reflected from the vacuum chamber. The vibration sensor 450 may further include a detector (not shown) for detecting the optical beam after being reflected from the vacuum chamber 120. Accordingly, information about the vibration of the vacuum chamber 120 may be collected by the vibration sensor 450. The vibration sensor may be an interferometer.

[0048] According to some embodiments, the vibration sensor is configured for measuring vibrations influencing the relative position between the imaging charged particle beam microscope and the substrate support. As shown in FIG. 5, this measurement may be conducted at the vacuum chamber in light of the relatively large amplitudes generated at the vacuum chamber. According to yet further or additional implementations, a vibration sensor, e.g. an interferometer or an piezo vibration sensor, can be mounted at the substrate support to measure the relative position (and position variation) of the imaging charged particle beam microscope or may be mounted to the imaging charged particle beam microscope to measure the relative position (and position variation) of the substrate support.

[0049] Data collected by the vibration sensor 450 regarding the relative position between the imaging charged particle beam microscope and the substrate support and/or the vibrations of the vacuum chamber 120 may be transmitted to a control unit (e.g. controller 180 in FIG. 1). Using the data collected by the vibration sensor 450, the control unit may control the apparatus 100. In particular, using the data collected by the vibration sensor 450, the control unit may control the first imaging charged particle beam microscope 130, the second imaging charged particle beam microscope 140, the displacement unit 410 or other components included in the apparatus 100, e.g. to temporarily pause the CD measurement of the substrate if the vibration sensor 450 indicates that the vibration of the vacuum chamber range exceed a predetermined limit. Yet further additionally or alternatively, the measurement of the relative position may be used to correct the images with an appropriate correction factor resulting from the measurement of the relative position.

[0050] FIG. 6 shows an imaging charged particle beam microscope, i.e. a charged particle beam device 500, such as the first imaging charged particle beam microscope and/or the second imaging charged particle beam microscope, as described herein. The charged particle beam device 500 includes an electron beam column 20 providing e.g. a first chamber 21, a second chamber 22 and a third chamber 23. The first chamber, which can also be referred to as a gun chamber, includes an electron beam source 30 having an emitter 31 and suppressor 32.

[0051] The emitter 31 is connected to a power supply 531 for providing a potential to the emitter. The potential provided to the emitter may be such that the electron beam is accelerated to an energy of e.g. 20 keV or above. Accordingly, the emitter may be biased to a potential of -1 kV voltages to provide landing energy of 1 keV for a grounded substrate. An upper electrode 562 is provided at a higher potential for guiding the electrons through column at a higher energy. [0052] With the device shown in Fig 6, an electron beam (not shown) may be generated by the electron beam source 30. The beam may be aligned to the beam limiting aperture 550, which is dimensioned to shape the beam, i.e. blocks a portion of the beam. Thereafter, the beam may pass through the beam separator 580, which separates the primary electron beam from a signal electron beam, i.e. from signal electrons. The primary electron beam may be focused on the substrate 160 by the objective lens. The substrate 160 is positioned on a substrate position on the substrate support 110. On impingement of the electron beam onto the substrate 160 signal electrons, for example, secondary and/or backscattered electrons or x-rays are released from the substrate 160, which can be detected by a detector 598.

[0053] In the exemplary embodiment illustrated in FIG. 6, a condenser lens 520 and a beam shaping or beam limiting aperture 550 are provided. The two-stage deflection system 540 is provided between the condenser lens and the beam limiting aperture 550, e.g. a beam shaping aperture, for alignment of the beam to the aperture. The electrons may be accelerated to the voltage in the column by an extractor or by the anode. The extractor can, for example, be provided by the upper electrode of the condenser lens 520 or by a further electrode (not shown).

[0054] As shown in FIG. 6, the objective lens has a magnetic lens component 561 having pole pieces 64 and 63 and having a coil 62, which focuses the primary electron beam on the substrate 160. The substrate 160 can be positioned on the substrate support 110. The objective lens shown in FIG. 6 includes the upper pole piece 63, the lower pole piece 64 and the coil 62 forming a magnetic lens component 60 of the objective lens. Further, the upper electrode 562 and a lower electrode 530 form an electrostatic lens component of the objective lens.

[0055] Further, in the embodiment illustrated in FIG. 6, a scanning deflector assembly 570 is provided. The scanning deflector assembly 570 (see also scanning deflector assembly 184 in FIG. 1) can, for example, be a magnetic, but preferably an electrostatic scanning deflector assembly, which is configured for high pixel rates. The scanning deflector assembly 570 may be a single stage assembly, as shown in FIG. 6. Alternatively, also a two-stage or even a three-stage deflector assembly can be provided. Each stage is provided at a different position along the optical axis 2. [0056] The lower electrode 530 is connected to a voltage supply (not shown). The embodiment illustrated in FIG. 6 shows the lower electrode 530 below the lower pole piece 64. The lower electrode being the deceleration electrode of the immersion lens component; i.e. a retarding field lens component, of the objective lens is typically at a potential to provide a landing energy of the charged particles on the substrate of 2 keV or below, e.g. 500 V or 1 keV.

[0057] The beam separator 580 is adapted for separating the primary and the signal electrons. The beam separator can be a Wien filter and/or can be at least one magnetic deflector, such that the signal electrons are deflected away from the optical axis 2. The signal electrons are then guided by a beam bender 591, e.g. a hemispherical beam bender, and a lens 595 to the detector 598. Further elements like a filter 596 can be provided. According to yet further modifications, the detector can be a segmented detector configured for detecting signal electrons depending on the starting angle at the specimen.

[0058] The first imaging charged particle beam microscope and the second imaging charged particle beam microscope may be charged particle beam devices of an imaging charged particle beam microscope type, such as e.g. the charged particle beam device 500 shown in FIG. 6.

[0059] FIG. 7 illustrates a method inspecting a substrate or of CD measurement on a substrate, particularly a large area substrate. A notch is cut with a focused ion beam under a first angle (see box 702). The first angle can be about 45°. One or more imaging charged particle beam microscopes measure under a second, different angle to scale in an X-Y plane (see box 704), i.e. a plane parallel to a substrate stage or parallel to a major surface of the substrate. The second angle can be about 90°. The second angle may also be advantageously chosen to have a short working distance while being able to position various positions of a large areas substrate below the charged particle beam microscope. For example, the working distance can be below 1 mm, such as 700 pm or below. Further, as indicated by box 706, a measuring of a dimension to scale is provided in Z-direction. For example, the three dimensions, e.g. in three different directions of a three dimensional coordinate system, can be measured from one image.

[0060] Embodiments of the present disclosure has at least one of several advantages, which are as follows: Critical dimension measurements can be provided without scaling error, particularly in three different directions, such as X, Y, and Z of a three dimensional coordinate system. A correction calculation error can be reduced or avoided. CD measurements in three different directions can be provided from one image. Throughput can be increased and charging and/or carbonization can be reduced. Accordingly, high precision of CD measurements can be provided, particularly for different directions of a three dimensional coordinate system, e.g. X, Y, and Z. Yet further, CD measurements can be provided with a high resolution, e.g. below 10 nm, on a large area substrate. Resolution limitations for EBR on large area substrates can be reduced to allow for higher resolution. Particularly for large area substrates a CD measurement can be provided in three different directions of a three dimensional coordinate system.

[0061] While the foregoing is directed to some embodiments, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A method for critical dimension measurement on a substrate, comprising: supporting the substrate with a major surface of the substrate being in an X-Y plane; cutting a notch with a focused ion beam column angled relative to a plane of the major surface of the substrate under a first angle; measuring at least one of a first dimension and a second dimension of one or more structures adjacent to the notch with a first imaging charged particle beam microscope having an optical axis angled relative to the plane of the major surface of the substrate under a second angle different from the first angle, the first dimension and the second dimension being in the X-Y plane and are measured to scale; and measuring a third dimension of the one or more structures to scale in a direction angled relative to the X-Y plane with the first imaging charged particle beam microscope having the optical axis.

2. The method of claim 1, wherein the first dimension or the second dimension are distances on the substrate, particularly in the X-Y plane.

3. The method of any of claims 1 or 2, wherein the first angle is about 42° to about 48°.

4. The method of any of claims 1 to 3, wherein the second angle is about 89° to about 91°.

5. The method of any of claims 1 to 4, further comprising: imaging an area of the substrate including the notch to obtain an image, wherein measuring at least one of a first dimension and a second dimension is based upon the image and wherein measuring the third dimension is based upon the image.

6. The method of claim 5, wherein the measuring at least one of the first dimension, the second dimension, and the third dimension are critical dimension measurements being measured by an intensity signal of the image.

7. The method of any of claims 1 to 6, further comprising: determining a desired dimension of the first dimension or the second dimension being measured to scale, correcting the third dimension being measured in scale based upon the desired dimension.

8. The method of any of claims 1 to 7, wherein the first angle and the second angle are fixed.

9. The method of any of claims 1 to 8, wherein a stage for supporting the substrate is limited to a movement in X-direction, Y -direction, and Z-direction and a rotating in the X- Y plane.

10. A method for critical dimension measurement on a substrate, comprising: imaging one or more structures provided on the substrate with a scanning charged particle beam device to obtain an image, an imaging plane of the scanning charged particle beam device being parallel to a major surface of the substrate and the image includes a notch generated in the substrate; measuring at the image critical dimensions to scale along three different directions of a three dimensional coordinate system.

11. The method of claim 10, wherein the three different directions include a first direction, a second direction and a third direction, the first direction and the second direction defining a plane parallel to the major surface of the substrate and the third direction being angled relative to the plane, particularly about perpendicular to the plane.

12. The method of claim 11, wherein the plane is a X-Y plane and the third direction is a z-direction.

13. The method of any of claims 10 to 12, wherein the critical dimensions include at least one of a first dimension and a second dimension of one or more structures adjacent to the notch and a third dimension, the third dimension being a layer thickness.

14. The method of any of claims 10 to 13, wherein a depth of focus of the image is larger than 5 pm and/or smaller than 30 pm.

15. An apparatus for inspecting a substrate and cutting an electronic device on the substrate, the apparatus comprising: a vacuum chamber; a stage arranged in the vacuum chamber and configured to support the substrate having the electronic device thereon; a focused ion beam column over the stage, the focused ion beam column having beam path angled at a first angle relative to a plane of a major surface of the substrate; and a first imaging charged particle beam microscope adjacent to the focused ion beam column and having the optical axis angled at a second angle relative to the plane of the major surface of the substrate, the second angle being different from the first angle, the second angle being configured to reduce optical distortion, and the first angle being configured to allow for critical dimension measurement to scale along three directions of the electronic device.

16. The apparatus for inspecting a substrate and cutting an electronic device on the substrate according to claim 15, wherein the first angle is about 42° to about 48°.

17. The apparatus for inspecting a substrate and cutting an electronic device on the substrate according to any of claims 15 to 16, wherein the second angle is about 89° to about 91°.

18. The apparatus for inspecting a substrate and cutting an electronic device on the substrate according to any of claims 15 to 17, the stage providing a substrate receiving area further comprising: a second imaging charged particle beam microscope having a distance from the first imaging charged particle beam microscope of 30% to 70% of the size of the substrate receiving area.

19. The apparatus for inspecting a substrate and cutting an electronic device on the substrate according to any of claims 15 to 18, further comprising: a controller comprising: a processor and a memory storing instructions that, when executed by the processor, cause the apparatus to perform a method according to any of claims 1 to 9.

20. The apparatus for inspecting a substrate and cutting an electronic device on the substrate according to any of claims 15 to 19, wherein the vacuum chamber has an inner dimension of 150% to 180% of substrate receiving area.

21. The apparatus for inspecting a substrate and cutting an electronic device on the substrate according to any of claims 15 to 20, wherein the second imaging charged particle beam microscope is distant from the first imaging charged particle beam microscope by a distance of at least 30 cm.