Method for calibrating deflector of charged particle beam device, and charged particle beam device

Abstract

A method for calibrating a deflector of a charged particle beam device, the deflector deflecting a charged particle beam of the charged particle beam device based on device coordinates of the charged particle beam device, the method comprising the steps of: placing a specimen on a platform in a vacuum chamber, the specimen providing a periodic pattern, the periodic pattern comprises a unit cell vector in a sample coordinate of the sample; acquiring a first image of a first region of the periodic pattern using the charged particle beam device; determining at least one first local distortion parameter based on the first image; acquiring a second image of a second area of the periodic pattern, wherein the second area is far away from the first area; determining at least one second local distortion parameter based on the second image; determining a first vector between the first region and the second region in a sample coordinate based on the at least one first local distortion parameter and the at least one second local distortion parameter; and calibrating the deflector based on the first vector.

Description

Technical Field

[0001] The present disclosure relates to a method for calibrating a deflector of a charged particle beam device. More specifically, embodiments described herein relate to distortion calibration of a charged particle beam device, such as a charged particle beam device of an electron beam system. Further, a charged particle beam device for imaging a specimen is described. Background Art

[0002] In many applications, it is beneficial to inspect samples, such as substrates on which structures are formed, in particular substrates on which electronic or optoelectronic structures are formed. For example, samples can be inspected to monitor the quality of the sample, in particular to detect defects that may have occurred during processing of the substrate, for example during structuring or coating of the substrate.

[0003] In some applications, thin layers are deposited on substrates, for example on glass substrates or circuit board substrates. The substrate is usually coated in a vacuum chamber of a coating device, in particular using a vapor deposition technique. In the past few years, electronic devices, in particular optoelectronic devices, have been manufactured with an increasing density of structures. For example, for thin film transistor (TFT) displays, high density TFT integration is beneficial. Despite the increase in the number and density of structures within the device, the yield has also to be increased and the manufacturing costs have to be further reduced.

[0004] During the manufacture of electronic or optoelectronic devices (such as displays), the deposited structure of a sample can be imaged to monitor the quality of the sample. For example, the imaging of the sample can be achieved using a charged particle beam device. The deflector of the charged particle beam device is traditionally calibrated using a calibration target having an array of markers arranged at known distances of several millimeters. However, traditional calibration targets often require expensive, special masks to produce, and may further require special production processes. Further, traditional calibration targets may not be easily accessible, cannot be inserted into the system at any time, may require storage space, and / or may not be very accurate. Further, the calibration of the deflector based on such traditional calibration targets may be slow and / or inaccurate.

[0005] Therefore, in view of the need to improve the quality, review and testing of displays or other specimens, there is a need for an improved method of calibrating a deflector of a charged particle beam device with high calibration accuracy and / or high calibration speed. Summary of the invention

[0006] According to aspects of the present disclosure, a method for calibrating a deflector of a charged particle beam device and a charged particle beam device for imaging a sample are provided. Further aspects, advantages and beneficial features can be seen from the dependent claims, the description and the drawings.

[0007] According to one aspect, a method for calibrating deflectors of a charged particle beam device is provided, which deflect the charged particle beam of the charged particle beam device based on the device coordinates of the charged particle beam device. The method includes the following steps: placing a sample on a platform in a vacuum chamber, the sample providing a periodic pattern, the periodic pattern including a unit cell vector in the sample coordinates of the sample. The method includes the following steps: using the charged particle beam device to obtain a first image of a first area of ​​the periodic pattern. The method includes the following steps: determining at least one first local distortion parameter based on the first image. The method further includes the following steps: obtaining a second image of a second area of ​​the periodic pattern, the second area being away from the first area. The method includes the following steps: determining at least one second local distortion parameter based on the second image. The method further includes the following steps: determining a first vector between the first area and the second area in the sample coordinates based on the at least one first local distortion parameter and based on the at least one second local distortion parameter. The method includes the following steps: calibrating the deflectors based on the first vector.

[0008] According to another aspect, a charged particle beam device for imaging a sample is provided. The charged particle beam device comprises: a platform for arranging the sample to be imaged; and a deflector for deflecting the charged particle beam of the charged particle beam device. The charged particle beam device further comprises: a computer-readable medium containing a program for calibrating the deflectors, which, when executed by a processor, performs a method according to the embodiments described herein.

[0009] According to another aspect, a method for calibrating deflectors (particularly sub-deflectors and / or main deflectors) of a charged particle beam device is provided, which deflect the charged particle beam of the charged particle beam device based on the device coordinates of the charged particle beam device. The method comprises the following steps: placing a sample on a platform in a vacuum chamber, the sample providing a periodic pattern, the periodic pattern comprising a unit cell vector in the sample coordinates of the sample. The method comprises the following steps: acquiring a first image of a first area of ​​the periodic pattern using the charged particle beam device. The method further comprises the following steps: determining at least one first local distortion parameter based on the first image, wherein the at least one first local distortion parameter is determined based on a Fourier transform of the first image. The step of determining the at least one first local distortion parameter may comprise the following steps: performing distribution fitting on at least one portion of the first image in frequency space, particularly distribution fitting based on a Gaussian distribution. The deflectors may be calibrated based on the at least one first local distortion parameter.

[0010] Embodiments are also directed to apparatus for implementing the disclosed methods, and include apparatus parts for performing each described method aspect. These method aspects may be performed by hardware components, computers programmed by appropriate software, any combination of the two, or in any other manner. In addition, embodiments according to the present disclosure are also directed to methods for operating the described apparatus and methods for manufacturing the apparatus and devices described herein. The methods for operating the described apparatus include method aspects for implementing each function of the apparatus. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] A full and effective disclosure for one of ordinary skill in the art is set forth in the remainder of the specification including references to the drawings.

[0012] Figure 1 A charged particle beam apparatus configured to operate in accordance with the methods described herein is shown;

[0013] Figure 2 is a flow chart illustrating a method for calibrating a deflector of a charged particle beam apparatus according to embodiments described herein;

[0014] Figure 3 schematically illustrates the periodic pattern provided by the specimen in specimen coordinates;

[0015] Figure 4 A schematic diagram showing an array of display pixels of a display used as a specimen for calibrating a charged particle beam apparatus is shown;

[0016] Figure 5 Shows Figure 3 a first image of the periodic pattern in device coordinates;

[0017] Figure 6 A portion of a Fourier transform of an image of a periodic pattern is illustrated;

[0018] Figure 7 Shows Figure 6 Distribution fitting of the peak value of the Fourier transform;

[0019] Figure 8 A first image and a second image are schematically illustrated;

[0020] Fig. 9 A schematic diagram showing a portion of a periodic pattern and a vector for determining a first vector according to an embodiment described herein;

[0021] Fig.10 illustrates the grid locations in device coordinates used to acquire images of periodic patterns;

[0022] Fig.11 shows the locations in the specimen coordinates, which are related to Fig.10 The grid position corresponds to;

[0023] Fig.12 illustrating deflector digital / analog (D / A) converter values ​​in device coordinates for a plurality of grid locations in specimen coordinates;

[0024] Fig.13 showing calibration results based on calibration according to embodiments described herein; and

[0025] Fig.14 Calibration results based on calibration according to previous calibration techniques are described. DETAILED DESCRIPTION

[0026] Reference will now be made in detail to the exemplary embodiments, one or more of which are illustrated in the drawings. Each example is provided by way of explanation and is not meant to be limiting. For example, features illustrated or described as part of one embodiment may be used in other implementations or used with other embodiments to produce further embodiments. The present disclosure is intended to include such modifications and variations.

[0027] In the following description of the figures, the same reference numerals refer to the same components. Only the differences related to the various embodiments are described. The structures shown in the figures are not necessarily depicted according to the true scale, but are used to better understand the embodiments.

[0028] Figure 1 Shown is a charged particle beam device 100 configured to operate according to the method described herein. Charged particle beam device 100 may include a scanning microscope 102, particularly a scanning electron microscope, whose beam source 110 is configured to produce a charged particle beam 101, particularly an electron beam. Charged particle beam 101 may be guided along optical axis A through a column 103 of the scanning microscope 102. The interior space of the column 103 may be evacuated. Scanning microscope 102 may include a beam influencing component (such as an accelerator 115, a decelerator, a lens assembly 120, a deflector 140 or other focusing or defocusing components), a beam corrector, a beam splitter, a detector and / or other components provided to affect the charged particle beam 101 propagating along optical axis A.

[0029] The charged particle beam device 100 includes a platform 20 for arranging the sample 10 thereon. The term "sample" as used herein may relate to a substrate on which one or more layers, features or electrical devices (such as TFTs) are formed. For example, the sample may be a display, or may include one or more displays. The sample 10 may be placed on the platform 20 for calibrating the charged particle beam device 100, particularly the deflector 140, and / or for imaging the sample 10, such as for testing or examining the sample 10. The platform 20 may be arranged in an imaging chamber 105, which may be evacuated in some embodiments. The platform 20 may be a movable platform. In particular, the platform 20 may be movable in a plane (also referred to herein as an XY plane) perpendicular to the optical axis A of the charged particle beam device 100. The platform 20 may be movable in a direction Z parallel to the optical axis A.

[0030] The scanning microscope 102 may include one or more focusing lenses, such as one or more focusing lenses of the lens assembly 120. The one or more focusing lenses may be configured to focus the charged particle beam 101 onto a sample 10 disposed on the platform 20. When the charged particle beam 101 impacts the surface of the sample 10, secondary electrons or backscattered electrons (also referred to as "signal electrons") are generated. The signal electrons provide information about the size, spatial characteristics and / or other characteristics of the surface features of the sample 10. The signal electrons can be detected with a detector. By scanning the charged particle beam 101 on the surface of the sample 10 (for example, with a deflector 140) and detecting the signal electrons as a function of the location where the signal electrons are generated, the surface of the sample 10 or a region thereof can be imaged.

[0031] In an embodiment, a deflector 140 may be provided for positioning the charged particle beam 101 on the surface of the sample 10 and / or for scanning the charged particle beam 101 on the surface of the sample 10, for example in the X direction and / or in the Y direction. In some embodiments, the deflector 140 includes a main deflector 142 and a sub-deflector 144. For example, the main deflector 142 may be a magnetic deflector. The sub-deflector 144 may be an electrostatic deflector. In an embodiment, the main deflector and / or the sub-deflector may each include two or more deflectors, in particular for deflecting the charged particle beam 101 into two or more different directions. According to some embodiments, the main deflector 142 may be configured to position the charged particle beam 101 at a specified position in a specified area on the sample 10. The sub-deflector 144 or the main deflector 142 may scan the charged particle beam 101 over the specified area, for example for imaging the specified area or for testing electrical equipment arranged in the specified area. For example, in Figure 1, the charged particle beam 101 is deflected by the main deflector 142 to a first position 16 in a first region 14 of the sample 10, the first region 14 spanning a first scanning range 18. The sub-deflector 144 or the main deflector 142 can scan the charged particle beam 101 over the first region 14 by scanning the charged particle beam 101 in the first scanning range 18.

[0032] According to some embodiments, the charged particle beam device 100 is configured to review and / or test samples. For example, the sample to be reviewed and / or tested may be a panel-level packaging (PLP) substrate or an advanced packaging (AP) substrate, which may be non-contact tested using a charged particle beam to identify and characterize defects such as short circuits, open circuits, and / or leakage. In another example, the sample may be a display comprising a substrate and a plurality of display pixels arranged thereon. The display pixels may be tested by applying a voltage pattern to the display pixels and then positioning a charged particle beam 101 (particularly an electron beam) to each display pixel. The voltage contrast of the secondary electrons generated by the charged particle beam 101 that strikes the display pixels may be measured and evaluated. The greater the negativity of the display pixel, the more secondary electrons are emitted. The greater the positivity of the display pixel, the fewer secondary electrons are emitted. Defective display pixels are revealed by displaying an erroneous voltage in a voltage contrast image.

[0033] However, the review or testing of PLP substrates, AP substrates, displays or other electronic or optoelectronic devices relies on the accurate positioning of the charged particle beam 101 over the deflection area, which can be scanned using the main deflector 142 and the auxiliary deflector 144. In some embodiments, the deflection area can be, for example, larger than 25 square centimeters, in particular larger than 100 square centimeters or larger than 400 square centimeters. In order to achieve accurate positioning of the charged particle beam 101 over the entire deflection area covered by the column 103, a so-called distortion calibration can be performed on the deflector 140. The distortion calibration can provide a two-dimensional (2D) calibration function that transforms the deflector digital / analog converter values ​​(D / A converter values) into sample coordinates over the entire deflection area - and vice versa.

[0034] As used herein, sample coordinates may refer to the coordinates of the sample 10. Specifically, the sample coordinates may be represented by a measure of length. The sample coordinates may be particularly specified in units of length, such as micrometers or millimeters. The distance and direction in the sample coordinates may indicate the true distance and true direction on the sample 10. In an embodiment, the charged particle beam device 100 may locate the charged particle beam 101 based on the internal coordinates of the charged particle beam device 100, which are referred to herein as "device coordinates". In an embodiment, the device coordinates may be or may correspond to the value of a D / A converter. The device coordinates may be represented, for example, by the pixels of the charged particle beam device. For example, in an image acquired by the charged particle beam device 100, an object having a first shape in the sample coordinates may appear as a distorted second shape in the device coordinates. The distortion of the first shape may include, for example, stretching, rotation and / or tilting of the first shape. Further, in different regions of the deflection region, the distortion may be different. The calibration function may take this distortion into account and may provide an accurate positioning of the charged particle beam 101 over the deflection region, in particular over the deflection region of the main deflector and / or the secondary deflector.

[0035] According to an embodiment of the present disclosure, a method for calibrating a deflector 140 of a charged particle beam apparatus 100 (particularly, a sub-deflector and / or a main deflector of the charged particle beam apparatus 100 ) is provided. Figure 2 A flow chart of a method 200 according to embodiments described herein is shown. The charged particle beam device 100 may be configured to deflect a charged particle beam 101 of the charged particle beam device 100 based on device coordinates of the charged particle beam device 100 .

[0036] In an embodiment, the method 200 includes the following steps: placing a sample 10 on a platform 20 in a vacuum chamber (box 210). The sample 10 provides a periodic pattern 12. In some embodiments, the sample 10 includes a substrate 11 and an array of electrical devices formed on the substrate 11. For example, the sample 10 can be a display, which includes a glass substrate and display pixels formed thereon, and these display pixels particularly include TFTs. The periodic pattern 12 can be provided by applying a voltage pattern to the array of electrical devices. In particular, the periodic pattern 12 can be provided by the following steps: applying a first voltage to a first group of electrical devices and applying a second voltage to a second group of electrical devices, the second voltage being different from the first voltage. Additionally or alternatively, the periodic pattern can be provided by periodically arranged structures on the substrate. In an image acquired using the charged particle beam device 100, the structure may show different material contrast or different topographic contrast. For example, these structures may include high-resolution patterns, particularly permanent patterns, produced by lithography on the substrate. More specifically, the structure of the pattern may not be electrically addressable.

[0037] Figure 3 A periodic pattern 12 of a sample 10 is shown, wherein the sample 10 comprises a display. The display may comprise display pixels 410, such as Figure 4 shown. Figure 3 and 4 The display pixels 410 shown may be similar or identical in structure. The periodic pattern 12 may be provided by applying a voltage pattern to the display pixels 410 of the sample 10. More specifically, a positive voltage may be applied to the display pixels of the first group 310, while a negative voltage may be applied to the display pixels of the second group 320. Figure 3 In the embodiment, the voltage pattern is applied according to a checker-board pattern. In further embodiments, the voltage pattern may be applied according to a different periodic pattern.

[0038] In an embodiment of the present disclosure, the periodic pattern 12 has unit cell vectors e, f in the sample coordinates x, y of the sample 10, in particular, the unit cell vectors e, f of the original unit cells of the periodic pattern 12. For example, Figure 3 The unit cell vectors e, f of the periodic pattern 12 are shown, including the first unit cell vector e=(e x ,e y ) and the second unit cell vector f=(f x ,f y In an embodiment, the length of each unit cell vector e, f of the periodic pattern 12 is at most 2 mm, in particular at most 1.5 mm or at most 1 mm. In some embodiments, the length of each unit cell vector e, f of the periodic pattern 12 can be at least 500 nanometers, in particular at least 1 micrometer or at least 5 micrometers.

[0039] According to an embodiment, the method 200 comprises the following steps: acquiring a first image 500 of a first region 14 of a periodic pattern 12 using a charged particle beam device 100 (box 220). In particular, the charged particle beam 101 may be deflected to a first position 16 of the first region 14 using a main deflector 142. The first image 500 may be acquired by scanning the charged particle beam 101 over the first region 14. In some embodiments, the charged particle beam 101 may be scanned over the first region 14 using the main deflector 142, in particular for calibrating the main deflector 142. In further embodiments, which may be combined with other embodiments described herein, the charged particle beam 101 may be scanned over the first region 14 using a sub-deflector 144, in particular for calibrating the sub-deflector 144. In an embodiment, the first image comprises at least two unit cells of the periodic pattern 12, in particular at least four unit cells or at least eight unit cells.

[0040] In some embodiments, particularly if the periodic pattern 12 is provided by applying a voltage pattern, the first image can be acquired by voltage contrast imaging. In voltage contrast imaging, the voltage contrast of secondary electrons generated by the charged particle beam 101 striking the periodic pattern 12 is measured and evaluated to acquire an image such as the first image 500. For example, Figure 5 Explained Figure 3 A first image 500 of a first region 14 of a periodic pattern 12 is shown. The periodic pattern 12 provided by the voltage pattern can be observed by voltage contrast imaging of the display pixel 410. The more negative the voltage of the display pixel 410, the more secondary electrons are emitted. The more positive the voltage of the display pixel 410, the fewer secondary electrons are emitted. The first image 500 shows the periodic pattern 12 in the device coordinates s, t, wherein the periodic pattern 12 appears distorted. In further embodiments, other imaging techniques (such as conventional SEM imaging, particularly without applying different voltages to the specimen) can be used to acquire the first image of the periodic pattern. For example, if the periodic pattern is provided by structures on a substrate, where these structures are not electrically addressed or cannot be electrically addressed, then conventional imaging methods can be used.

[0041] In an embodiment, the method 200 includes the following steps: determining at least one first local distortion parameter based on the first image 500 (block 230). The at least one first local distortion parameter may indicate a distortion of the periodic pattern 12 in the first image 500. According to some embodiments, the at least one first local distortion parameter includes a first local distortion matrix U. The first local distortion matrix U may provide a local transformation between the sample coordinates x, y and the device coordinates s, t, particularly for the first image 500. In the first image 500, the imaged periodic pattern may have an image unit cell vector u=(u s ,u t ) and v=(v s ,v t ), for example Figure 5 In an embodiment, the first local distortion matrix U may in particular provide a transformation between unit cell vectors e, f in the sample coordinates x, y and image unit cell vectors u, v in the device coordinates s, t, for example according to equation 1. The unit cell vectors e, f of the periodic pattern 12 may be known, for example from the manufacture of the sample 10. The image unit cell vectors u, v may be determined based on the first image 500, in particular according to the embodiments described herein.

[0042]

[0043] In some embodiments, the at least one first local distortion parameter is determined based on a Fourier transform of the first image 500. The Fourier transform may be a fast Fourier transform. The Fourier transform may be a discrete Fourier transform. The Fourier transform may be a two-dimensional (2D) Fourier transform of the first image 500. For example, the Fourier transform may be a two-dimensional fast Fourier transform. For example, the Fourier transform may be determined according to Equation 2 using an image resolution N, using k, l=0, 1...N-1, and using an image grayscale g.

[0044]

[0045] The periodic pattern 12 (particularly the image unit cell vectors u, v) is reflected by the peaks in the amplitude R:=|F| of the Fourier transform F, more particularly by the peaks at the peak positions a, b, where a=(a k ,a l ) and b=(b k ,b l ). In an embodiment, the image unit cell vectors u, v may be determined based on the Fourier transform of the first image 500. Determining the image unit cell vectors u, v may include determining the peak positions a, b of the Fourier transform of the first image 500 in the frequency space. The peak positions a, b may be defined as vectors pointing to the peaks 620 in the Fourier transform, in particular, vectors from the central peak 610 to the two peaks 620 closest to the central peak 610. For example, Figure 6 The amplitude R of the Fourier transform in the frequency space coordinates k, l is illustrated. The Fourier transform includes a central peak 610. Each vector corresponding to a peak position a, b points to a peak 620 that is closest to the central peak 610. For reasons of symmetry, it may be sufficient to determine two peak positions a, b.

[0046] According to some embodiments, determining the at least one first local distortion parameter includes fitting a distribution to at least a portion of the first image 500 in frequency space. In particular, the peaks 620 closest to the central peak 610 of the Fourier transform of the first image 500 may be fitted using a distribution. In some embodiments, each peak 620 may be fitted by fitting a peak value 705 of the peak 620 and adjacent values ​​of the peak 620 (e.g., the peak value 705 and eight adjacent values ​​710). The maximum value determined by the distribution fitting is and Can be used as peak positions a, b. Distribution fitting can provide a more accurate determination of peak positions a, b in particular.

[0047] In some embodiments, the distribution fitting is based on a Gaussian distribution, in particular a two-dimensional Gaussian distribution. In particular, the peak 620 can be fitted using a Gaussian distribution to determine the maximum value a of the peak 620. 0 ,b 0 .For example, Figure 7 This illustrates the use of Gaussian distribution in frequency space for fitting. Figure 6 The peak value 705 corresponding to the peak position a and the eight adjacent values ​​710 of the peak value 705. In particular, the parameter c can be used 1 、c 2 、c 3 , k 0 and l 0 Fit a two-dimensional Gaussian distribution R(k,l) to the data values ​​to determine the location of the peak maximum a=(k 0 ,l 0 ). For example, Equation 3 provides a two-dimensional Gaussian distribution. If the peak in the Fourier transform has no minimum height, then the parameter c 1 It can be used to identify images without periodic patterns.

[0048]

[0049] According to an embodiment, the image unit cell vectors u and v of the first image 500 may be determined based on the peak positions a and b, for example, according to Equation 4. For example, Figure 5 The unit cell vectors u, v shown can be determined based on the peak positions a, b determined in the frequency space.

[0050]

[0051] Based on the unit cell vectors e, f and on the image unit cell vectors u, v, a first local distortion matrix U can be determined, in particular according to equation 5.

[0052]

[0053] The at least one first local distortion parameter (particularly the first local distortion matrix U) may be used for local distortion calibration. The local distortion calibration may be used for calibrating the secondary deflector 144 , particularly for the first region 14 .

[0054] In order to calibrate the deflector 140 (particularly the main deflector 142) for other regions (particularly the entire deflection region) of the deflection region of the main deflector 142 and the auxiliary deflector 144, a global distortion calibration may be performed. Performing the global distortion calibration may include performing additional local distortion calibration on other regions of the periodic pattern in the deflection region. The global distortion calibration may further include determining vectors between regions for which local distortion calibration has been performed.

[0055] In some embodiments, the method 200 includes the following steps: acquiring a second image 810 of a second region 910 of the periodic pattern 12 (box 240). The first region 14 and the second region 910 are regions of the periodic pattern 12 shown in the first image 500 and the second image 810, respectively. The second region 910 may be away from the first region 14. In particular, the first region 14 and the second region may be non-intersecting regions of the periodic pattern 12. The first region 14 and the second region may not be overlapping regions, nor may they be adjacent regions of the periodic pattern 12. The charged particle beam 101 may be deflected to a second position of the second region 910 using the main deflector 142, the second position being different from the first position 16. The second image 810 may be acquired by scanning the charged particle beam 101 over the second region 910 (in particular, scanning using the main deflector 142). In an embodiment, the second image 810 includes at least two unit cells of the periodic pattern 12, in particular at least four unit cells or at least eight unit cells.

[0056] According to an embodiment of the present disclosure, the method 200 comprises the following steps: determining at least one second local distortion parameter based on the second image 810 (block 250). The at least one second local distortion parameter may be determined based on the second image 810, similar to determining the at least one first local distortion parameter based on the first image 500. In particular, the at least one second local distortion parameter may be determined based on a Fourier transform of the second image 810. The step of determining the at least one second local distortion parameter may comprise the following steps: performing a distribution fitting on at least one portion of the second image in frequency space, in particular using a Gaussian distribution.

[0057] In some embodiments, the at least one second local distortion parameter includes a second local distortion matrix U′. The second local distortion matrix U′ may provide a local transformation between sample coordinates and device coordinates, particularly for the second image 810 and the second region 910 .

[0058] According to some embodiments, the method 200 comprises the following steps: determining a first vector d between the first region 14 and the second region 910 in the sample coordinates based on the at least one first local distortion parameter and based on the at least one second local distortion parameter g '(Block 260). The first vector d g The first position 16 where the first image 500 is acquired can be connected to the second position where the second image 810 is acquired. In an embodiment, the first vector d in the sample coordinates x, y g ' can correspond to the image connection vector d in device coordinates s, t g , image connection vector d g Connect the first image 500 and the second image 810. For example, the image connection vector dg The center of the first image 500 may be connected to the center of the second image 810 .

[0059] Figure 8 and 9 The method for determining the first vector d according to an embodiment is schematically illustrated. g '. Figure 8 A first image 500 of a first region 14 of a periodic pattern 12 and a second image 810 of a second region 910 of the periodic pattern 12 are illustrated. The image connection vector d g The center of the first image 500 and the center of the second image 810 are connected in the device coordinates s, t. In an embodiment, the image connection vector d g is predetermined or can be calculated based on the first position and the second position in the device coordinates s,t. Fig. 9 A periodic pattern 12 in the sample coordinates x, y is schematically shown, the periodic pattern comprising a first region 14 and a second region 910 . Fig. 9 The first vector d in the sample coordinates x,y is shown g ', which is connected to the image vector d in device coordinates s,t g Corresponding.

[0060] According to an embodiment, the first vector d is determined g ' includes based on the first local distortion matrix U, based on the second local distortion matrix U' and based on the image connection vector d g To determine the approximate first vector d g0 '. In particular, the first vector d g0 ' can be determined based on the average value of the first local distortion matrix U and the second local distortion matrix U', in particular according to Equation 6.

[0061]

[0062] In an embodiment, the first vector d g 'Can be further approximated by the first vector d g0 ' more accurately determined. In particular, the distortion may be along the image connection vector d g Change. The first vector d g ' can be determined more accurately based on the periodicity of the periodic pattern 12. In an embodiment, the first vector d g ' is further determined based on the unit cell vectors e and f of the periodic pattern 12. Determine the first vector d based on the periodic pattern 12 g ' may specifically include determining a shift vector indicating a shift or offset between the periodic pattern 12 and each of the first image 500 and the second image 810.

[0063] According to an embodiment, the at least one first local distortion parameter comprises a first shift vector s 1 The first shift vector s 1 The first displacement vector s may indicate a first displacement between the periodic pattern 12 and the first image 500. For example, 1 The offset between the pattern reference point of the periodic pattern 12 and the image reference point of the first image 500 can be indicated. The pattern reference point can be a reference point of a unit cell of the periodic pattern 12, in particular, a feature point of the unit cell. Figure 8 In the example, the pattern reference point is a corner of a rectangle in the chessboard pattern. The image reference point of the first image 500 may be, for example, the center of the first image 500. In an embodiment, the first shift vector s 1 It can be determined based on the Fourier transform of the first image 500. The image displacement s=(s s ,s t )(in device coordinates s, t) changes the Fourier transform F =: R·e -iφ The phase φ of Δφ is Δφ, in particular according to equation 7.

[0064]

[0065] By defining the phase φ of the Fourier transform F as caused by the shift s, the shift s can be calculated from the phase φ of the peaks a and b in the Fourier transform. In particular, the shift s can be calculated from the phase φ of the peaks a and b (see equations 8 and 9), where the maximum value of the peak 620 determined by the distribution fit in the frequency space is and is used as the peak positions a, b. The shift s can be calculated according to Eq. 10.

[0066]

[0067] For example, the first shift vector s 1 can be calculated as the shift s of the first image 500 .

[0068] According to an embodiment, the at least one second local distortion parameter comprises a second shift vector s 2 The second shift vector s 2 The second shift vector s may indicate a second shift or offset between the periodic pattern 12 and the second image 810. 2 The first displacement vector s can be calculated based on the second image 810, which is similar to the first displacement vector s calculated based on the first image 500. 1 In particular, the second shift vector s 2 can be calculated as the shift s of the second image 810 .

[0069] The first shift vector s in device coordinates s,t1 can be converted to the first shift vector s in the sample coordinates x, y 1 ', in particular based on the first local distortion matrix U by s 1 '=U -1 ·s 1 Similarly, the second shift vector s in device coordinates s,t 2 can be converted into the transformed second shift vector s in the sample coordinates x, y 2 ', in particular based on the second local distortion matrix U' by s 2 '=U' -1 ·s 2 .

[0070] The first shift vector s 1 , image connection vector d g and the second shift vector s 2 The vector addition of can provide the vector d in device coordinates s,t u , where the vector d u From the pattern reference point of the first image 500, another pattern reference point of the second image 810 is pointed to, for example, Figure 8 As shown. And the vector d in the device coordinates s, t u Similarly, the reference vector d in the specimen coordinates x,y u 'Connect two reference points of the periodic pattern 12, for example Fig. 9 As shown. Reference vector d u '=(d ux ',d uy ') must be integer i, j times the unit cell vector e, f (see Equation 11), because the first shift vector s after conversion 1 ' and the converted second shift vector s 2 Each of ' points to the pattern reference point of the unit cell.

[0071]

[0072] Approximate reference vector d u0 '=d g0 '+s 2 '-s 1 ' can be based on the approximate first vector d g0 ' and the shift vector s 2 ' and s 1 ' to determine. As an approximation to an integer, a non-integer i r and j r It can be based on the approximate reference vector d u0 'to be determined, for example according to Equation 12.

[0073]

[0074] Next, integers i and j can be obtained by r and j r Based on the integers i, j corresponding to the reference vector du', the first vector dg' can be determined by vector addition, in particular according to equation 13.

[0075] dg=i·e+j·f+s-( 方程式13 )

[0076] According to an embodiment, the method includes the following steps: calibrating the deflector based on the first vector dg' (box 270). In an embodiment, the first vector dg' provides the accurate relative position of the second image 810 relative to the first image 500 in the specimen coordinates x, y. The first vector dg' and the corresponding image connection vector dg can be used to determine the relationship between the specimen coordinates x, y and the device coordinates s, t. The determined relationship can be used, for example, to determine a calibration function or a calibration lookup table. Further, one or more local distortion parameters can be interpolated for the area between the first area 14 and the second area 910. In some embodiments, the local distortion matrix can be interpolated for any area between the first area 14 and the second area 910 based on the first local distortion matrix U and the second local distortion matrix U'.

[0077] In an embodiment, the method 200 further comprises the step of determining a plurality of other vectors in the sample coordinates x,y based on other images of non-intersecting regions of the periodic pattern 12. According to an embodiment, the first image 500, the second image 810 and the other images are acquired at the grid position 1010, specifically at the grid position 1010 in the device coordinates s,t.

[0078] In an embodiment, the distance between the first position of the first image and the second position of the second image and / or the distance between the grid positions can be selected so that the absolute deviation of the non-integer ir and jr from the corresponding integers i, j remains small, for example less than 0.3 or less than 0.2. In the event of larger absolute deviations, a smaller distance between the positions in the device coordinates s, t can be selected for calibration. In some embodiments, the distance between the positions in the sample coordinates x, y can be greater than 1 mm, in particular greater than 2 mm or greater than 3 mm. For example, the distance can be about 5 mm.

[0079] Determining each of the plurality of other vectors may include determining at least one other local distortion parameter based on one of the other images. The at least one other local distortion parameter for the other images may be determined similarly to determining the at least one first local distortion parameter for the first image 500. Based on the at least one other local distortion parameter and based on the at least one previously determined local distortion parameter, the other vectors of the plurality of other vectors may be determined. Each of the plurality of other vectors may be determined in conjunction with determining the first vector d g 'Similarly decided.

[0080] For example, the second vector of the plurality of other vectors may be determined according to the operations outlined with respect to blocks 240, 250, and 260 of method 200. In particular, in determining the first vector d g ', a third image may be acquired at a grid position 1010 away from the second position. At least one third local distortion parameter may be determined based on the third image. The second vector may be determined based on the at least one second local distortion parameter associated with the second image 810, and further determined based on the at least one third local distortion parameter.

[0081] According to some embodiments, the first position for acquiring the first image may be the center position of the grid position 1010. Subsequent images may be acquired at adjacent grid positions of the grid position 1010. For example, the first image, the second image, and the further images may be acquired along the grid positions, particularly starting from the center position, in a square spiral path 1020, such as Fig.10 shown.

[0082] In an embodiment, the method 200 comprises the following steps: based on the plurality of other vectors (particularly based on the first vector d g ' and the plurality of other vectors) to calibrate the deflector 140. For example, Fig.11 Explains the Fig.10 The grid position 1010 shown corresponds to the position of the sample in coordinate x, y. Fig.10 and 11 The graph of allows to determine a calibration function or calibration lookup table that converts the grid positions 1010 ( Fig.10 ) and the corresponding position 1110 in the sample coordinate x, y ( Fig.11 ) and vice versa.

[0083] In particular, based on the relationship between the device coordinates s,t and the specimen coordinates x,y, the inverse of the distortion calibration function can be determined, which provides the deflector D / A converter values ​​in the device coordinates s,t as a function of the specimen coordinates x,y. Fig.12A plurality of D / A converter values ​​in device coordinates s,t are illustrated, corresponding to a plurality of equally spaced grid positions in specimen coordinates x,y.

[0084] Further, the local distortion matrix determined for grid position 1010 may be interpolated between grid positions 1010. For example, Fig.13 An example of distortion calibration results based on calibration using a display to provide a periodic pattern is described. In particular, Fig.13 The matrix elements U of the local distortion matrix determined at grid positions 1010 and interpolated between grid positions 1010 are shown. 1 In contrast, Fig.14 The matrix elements U determined according to the previous calibration technique are shown in 1 In particular, compared to the deflector calibration according to the previous calibration technique ( Fig.14 ) compared to the deflector calibration based on the local distortion matrix determined according to the embodiments described herein ( Fig.13 ) can be more accurate and show less noise. The main deflector calibration according to the embodiments described herein can provide a more reliable calibration. In particular, manual corrections can be reduced or avoided. Further, the calibration of the auxiliary deflector can be performed about 10 times faster than previous calibration techniques.

[0085] According to a further embodiment, a method for calibrating a deflector 140 (particularly a sub-deflector 144) of a charged particle beam device 100 is provided. The method may include any of the operations of the method 200 described herein, particularly the operations described with respect to blocks 210, 220, and 230 of the method 200. The method may further include the following steps: calibrating the deflector 140, particularly the sub-deflector 144, based on the at least one first local distortion parameter. For example, the sub-deflector 144 may be calibrated based on a first local distortion matrix determined for the acquired first image 500.

[0086] In some embodiments, which may be combined with other embodiments, the method for calibrating one or more deflectors of a charged particle beam device may be partially or fully automated. In particular, automated calibration and / or imaging may provide high throughput and / or reduce costs.

[0087] According to some embodiments, a charged particle beam device can be used for or configured to image, test and / or review a packaging substrate (such as a PLP substrate or an AP substrate). Over the years, in order to reduce the space requirements of semiconductor packaging, the complexity of packaging substrates has been increasing. In order to reduce manufacturing costs, some packaging technologies have been proposed, such as 2.5D IC, 3D-IC and wafer-level packaging (WLP), such as fan-out WLP. In WLP technology, integrated circuits are packaged before being cut. The "packaging substrate" used herein relates to a packaging substrate constructed for advanced packaging technology, particularly WLP technology or panel-level packaging (PLP) technology.

[0088] "2.5D integrated circuits" (2.5D ICs) and "3D integrated circuits" (3D ICs) combine multiple dies in a single integrated package. Here, two or more dies are placed on a packaging substrate, such as a silicon interposer or a panel-level packaging substrate. In a 2.5D IC, the dies are placed side by side on the packaging substrate, while in a 3D IC, at least some of the dies are placed on top of other dies. The assembly can be packaged as a single part, which can reduce cost and size compared to traditional 2D circuit board assemblies.

[0089] The package substrate typically includes a plurality of electrical interconnection paths between devices for providing electrical connections between chips or dies to be placed on the package substrate. The electrical interconnection paths between devices may extend vertically (perpendicular to the surface of the package substrate) and / or horizontally (parallel to the surface of the package substrate) through the body of the package substrate, and to the terminals exposed at the surface of the package substrate (referred to herein as surface contacts) in a complex network of connections.

[0090] Advanced packaging (AP) substrates provide electrical interconnection paths between devices on or within a wafer such as a silicon wafer. For example, an AP substrate may include through silicon vias (TSVs) (which are provided, for example, in a silicon interposer), other conductor lines extending through the AP substrate. Panel-level packaging substrates are provided by composite materials, such as printed circuit board (PCB) materials or another composite material, including, for example, ceramic and glass materials.

[0091] The manufactured panel-level packaging substrate is constructed to integrate multiple devices (e.g., chips / die that may be heterogeneous (e.g., may have different sizes and configurations)) in a single integrated package. Further, AP substrates can be combined on a PLP substrate. The panel-level substrate typically provides sites (e.g., on one or both sides) for multiple chips, die, or AP substrates placed on its surface, as well as electrical interconnection paths between multiple devices extending through the body of the PLP substrate.

[0092] It is worth noting that the size of the panel-level substrate is not limited to the size of the wafer. For example, the panel-level substrate can be rectangular or have another shape. Specifically, the panel-level substrate can provide a larger surface area than the surface area of ​​a typical wafer, for example, 1000 cm 2 For example, the size of the panel-level substrate may be 30 cm x 30 cm or more, 60 cm x 30 cm or more, 60 cm x 60 cm or more.

[0093] In some embodiments, the charged particle beam apparatus is configured to image and / or calibrate with a sample, including a large area substrate for display manufacturing having a surface area of ​​1 m 2 or larger. The surface area may be from about 1.375m 2 (1100mm×1250mm—GEN 5) to about 10m 2 , more specifically, from about 2m 2 To approximately 10m 2 , even up to 12m 2 For example, the substrate may be GEN 7.5 (corresponding to approximately 4.39 m 2 (1.95m x 2.25m) surface area), GEN 8.5 (corresponding to approximately 5.7m 2 (2.2m x 2.5m) surface area) or even GEN 10.5 (corresponding to about 10m 2 (surface area of ​​2.95 m x 3.37 m). Even larger generations (such as GEN 11 and GEN 12) may be implemented.

[0094] The sample may include a non-flexible substrate (e.g., a glass substrate or glass plate) or a flexible substrate (such as a coil or foil or thin glass sheet). The sample may be a coated substrate, wherein one or more thin layers of material or other features are deposited on the substrate, for example by a physical vapor deposition (PVD) process or a chemical vapor deposition process (CVD) process or a lithographic process or an etching process. In particular, the sample may include a substrate for display manufacturing and a plurality of electronic or optoelectronic devices formed thereon. The electronic or optoelectronic devices formed on the substrate are typically thin film devices including a stack of thin layers. For example, the sample may be a substrate on which an array of thin film transistors (TFTs) is formed, for example, a substrate based on thin film transistors.

[0095] According to an embodiment of the present disclosure, a charged particle beam device 100 for imaging a sample 10 includes a platform 20 for arranging the sample 10 to be imaged. The charged particle beam device 100 may further include one or more deflectors 140 for deflecting a charged particle beam 101 of the charged particle beam device 100. In an embodiment, the charged particle beam device 100 includes a computer-readable medium, which contains a program for calibrating the one or more deflectors 140, which, when executed by a processor, performs a method according to the embodiments described herein, in particular, a method for calibrating the one or more deflectors of the charged particle beam device 100. The charged particle beam device 100 may be configured to image the sample 10 based on the calibration performed according to the method described herein.

[0096] In some embodiments, the charged particle beam device 100 includes a controller 160, which is connected to the charged particle beam device 100 (see, for example, Figure 1). The controller 160 of the charged particle beam device 100 may include a central processing unit (CPU), a computer readable medium according to the embodiments described herein, and, for example, a support circuit. To facilitate control of the charged particle beam device 100, the CPU may be one of any form of general-purpose computer processors that can be used in an industrial environment to control various components and subprocessors. The computer readable medium is coupled to the CPU. The computer readable medium or memory may be one or more easily accessible memory devices, such as random access memory, read-only memory, hard disk, or any other form of local or remote digital storage. The support circuit may be coupled to the CPU for supporting the processor in a conventional manner. The support circuit includes a cache, a power supply, a clock circuit, an input / output circuit system and related subsystems, and the like. Instructions for calibrating the one or more deflectors 140 of the charged particle beam device 100 are generally stored in a computer readable medium as a software routine commonly referred to as a recipe. The software routine may also be stored and / or executed by a second CPU that is away from the hardware controlled by the CPU. The software routine, when executed by the CPU, transforms a general-purpose computer into a special-purpose computer (controller), which controls the charged particle beam device 100, and can calibrate the one or more deflectors 140 of the charged particle beam device 100 according to any embodiment of the present disclosure. Although the method of the present disclosure is discussed as being implemented as a software routine, some method operations disclosed therein can also be performed in hardware and performed by a software controller. Therefore, the embodiments can be implemented in software when executed on a computer system, implemented in hardware as a special application integrated circuit or other types of hardware implementation, or implemented in a combination of software and hardware. The controller 160 can execute / perform the method for calibrating one or more deflectors of a charged particle beam device according to the embodiments described herein.

[0097] According to the embodiments described herein, the methods of the present disclosure may be performed using computer programs, software, computer software products and interrelated controllers, which may have a CPU, a computer readable medium or memory, a user interface, and input and output devices that communicate with corresponding components of the apparatus.

[0098] Methods according to embodiments described herein can be used to calibrate charged particle beam equipment for process control (e.g., for producing packaging substrates, such as PLP substrates or AP substrates, flat panels, displays, OLED devices (such as OLED screens), TFT-based substrates, and / or other samples having multiple electronic or optoelectronic devices formed thereon). Process control can include, for example, periodic monitoring, imaging, and / or defect review.

[0099] Embodiments of the present disclosure can advantageously provide faster and / or more accurate calibration of one or more deflectors of a charged particle device, such as a scanning electron microscope. Further, calibration according to the embodiments can be performed without conventional calibration plates, which can be expensive, can require storage space, and / or can require the production of special masks. For example, calibration according to the embodiments can be performed using a specimen comprising a substrate having an accurate, high-resolution periodic pattern. Such a specimen can be readily available or can be produced using existing masks, such as masks used to manufacture electronic or optoelectronic devices. In some embodiments, the specimen used for calibration can be a specimen to be tested or reviewed, such as a display.

[0100] While the foregoing is directed to certain embodiments, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is to be determined by the following claims.

Claims

1. A method for calibrating a deflector of a charged particle beam device, wherein the deflector deflects a charged particle beam of the charged particle beam device based on device coordinates of the charged particle beam device, the method comprising the following steps: placing a sample on a platform in a vacuum chamber, the sample providing a periodic pattern including a unit cell vector in a sample coordinate of the sample; acquiring a first image of a first region of the periodic pattern using the charged particle beam device; determining at least one first local distortion parameter based on the first image; Acquire a second image of a second area of ​​the periodic pattern, where the second area is far away from the first area; determining at least one second local distortion parameter based on the second image; determining a first vector between the first region and the second region in specimen coordinates based on the at least one first local distortion parameter and based on the at least one second local distortion parameter; and The deflector is calibrated based on the first vector. 2 . The method of claim 1 , wherein the first vector is further determined based on the unit cell vector of the periodic pattern.

3. The method of claim 1 , wherein the at least one first local distortion parameter is determined based on a Fourier transform of the first image; and wherein the at least one second local distortion parameter is determined based on a Fourier transform of the second image.

4. The method according to claim 1 , wherein the step of determining the at least one first local distortion parameter comprises the following steps: Distribution fitting is performed on at least one portion of the first image in frequency space; and wherein the step of determining at least one second local distortion parameter comprises the following steps: distribution fitting is performed on at least one portion of the second image in frequency space. The method of claim 4 , wherein the distribution fitting is based on a Gaussian distribution.

6. A method as claimed in any of the preceding claims, wherein the at least one first local distortion parameter comprises a first local distortion matrix, wherein the at least one second local distortion parameter comprises a second local distortion matrix, and wherein each of the first local distortion matrix and the second local distortion matrix provides a local transformation between the specimen coordinates and the device coordinates.

7. A method as claimed in any one of the preceding claims, wherein the at least one first local distortion parameter comprises a first shift vector indicating a first offset between the periodic pattern and the first image; and wherein the at least one second local distortion parameter comprises a second shift vector indicating a second offset between the periodic pattern and the second image.

8. A method as claimed in any one of the preceding claims, wherein the deflector comprises a main deflector and a sub-deflector, in particular wherein each of the first image and the second image is acquired by scanning the charged particle beam using the main deflector.

9. The method of claim 8, wherein the charged particle beam is deflected to a first position using the main deflector to acquire the first image; and wherein the charged particle beam is deflected to a second position using the main deflector to acquire the second image.

10. The method of any preceding claim, wherein the length of each of the unit cell vectors of the periodic pattern is at most 2 millimeters.

11. The method according to any of the preceding claims, wherein each of the first image and the second image comprises at least two unit cells, in particular at least four unit cells, of the periodic pattern.

12. A method as claimed in any one of the preceding claims, wherein the specimen comprises a substrate and an array of electrical devices formed on the substrate, and wherein the periodic pattern is provided by applying a first voltage to a first group of the electrical devices and applying a second voltage to a second group of these electrical devices, the second voltage being different from the first voltage.

13. The method according to any one of the preceding claims, further comprising the steps of: Based on other images of non-intersecting regions of the periodic pattern, a plurality of other vectors in the sample coordinates are determined, wherein the step of determining each of the plurality of other vectors comprises the following steps: determining at least one other local distortion parameter based on one of the other images; determining the further vector based on the at least one further local distortion parameter and based on at least one previously determined local distortion parameter; and Based on the plurality of other vectors, the deflector is calibrated.

14. The method of claim 13, wherein the first image, the second image and the further images are acquired at grid positions, in particular at grid positions in device coordinates.

15. A charged particle beam device for imaging a sample, the charged particle beam device comprising: A platform for arranging the sample to be imaged; a deflector for deflecting a charged particle beam of the charged particle beam device; as well as A computer readable medium containing a program for calibrating the deflector, which program, when executed by a processor, performs the method as claimed in any one of claims 1 to 14.

Images