Method of testing a packaging substrate, method of operating an apparatus for testing of a packaging substrate, and apparatus for testing a packaging substrate

Abstract

A method includes: vector scanning a charged particle beam from a first position on a packing substrate to a second position on the packing substrate while the charge particle beam is blanked, the vector scanning being based upon a first calibration of the charged particle beam properties of the charged particle beam and being based upon a second calibration of a beam position of the charged particle beam; un-blanking the charged particle beam onto the second position; blanking the charged particle beam at the second position; vector scanning the charged particle beam from the second position to a third position on the packing substrate while the charged particle beam is blanked, the vector scanning being based upon the first calibration and the second calibration; and testing networks on the packing substrate in the vacuum chamber based upon signals received from the third position.

Description

METHOD OF TESTING A PACKAGING SUBSTRATE, METHOD OF OPERATING AN APPARATUS FOR TESTING OF A PACKAGING SUBSTRATE, AND APPARATUS FOR TESTING A PACKAGING SUBSTRATEFIELD

[0001] The present disclosure relates to a method and an apparatus for testing a packaging substrate. More particularly, embodiments described herein relate to the contactless testing of electric interconnections in a packaging substrate, particularly a panel-leveling packing (PLP) substrate or an advanced packaging (AP) substrate by using charged particle beams, particularly for identifying, characterizing, detecting and / or classifying defects such as shorts, opens, and / or leakages.BACKGROUND

[0002] In many applications, it is necessary to inspect a substrate to monitor the quality of the substrate. Since defects may occur e.g. during the processing of the substrates, e.g. during structuring or coating of the substrates, an inspection of the substrate for reviewing the defects and for monitoring the quality may be beneficial.

[0003] Semiconductor packaging substrates and printed circuit boards for the manufacture of complex microelectronic and / or micro-mechanic components are typically tested during and / or after manufacturing for determining defects, such as shorts or opens, in metal paths and interconnects provided at the substrate. For example, substrates for the manufacture of complex microelectronic devices may include a plurality of interconnect paths for connecting semiconductor chips or other electrical devices that are to be mounted on the packing substrate.

[0004] Various methods for testing such components are known. For example, contact pads of a component to be tested may be contacted with a contact probe, in order to determine whether the component is defective or not. Since the components and the contact pads are becoming progressively smaller due to theprogressing miniaturization of components, contacting the contact pads with a contact probe may be difficult, and there may even be a risk that the device under test gets damaged during the testing.

[0005] The complexity of packaging substrates is increasing and design rules (feature size) are decreasing substantially. Within such substrates the surface contact points (for later flip chip or other chip mounting) are connected to other surface contact points on the packaging substrate to interconnect semiconductor (or other) devices. Standard methods like electrical-mechanical probing for electrical testing cannot satisfy the requirements of volume production testing as the throughput decreases (flying prober, higher number of test points) and contacting reliability decreases (electrical prober, smaller contact size). Beyond the reduced size and the problem of potentially damaging contact pads, the topography of the packaging substrates results in difficulties for other test methods, like test methods utilizing capacitive detectors or electric field detectors, because such methods beneficially have a small mechanical spacing.

[0006] A contactless electrical test with an electron beam can be conducted with a voltage signal reading, i.e. voltage contrast by signal electrons detection, such as secondary electrons (SE) and with charging of the test points or networks with an electron beam. The SE energy depends on the starting potential and therefore the SE signal can be used to measure or evaluate the potential by voltage contrast on different positions on the packing substrate. For packaging substrates, the signal to noise ratio may result in a false defect detection.

[0007] Accordingly, it would be beneficial to provide improved testing methods and testing apparatuses that are suitable for reliably and quickly testing complex microelectronic devices, particularly packaging substrates such as Advanced Packaging (AP) substrates and Panel Level Packaging (PLP) substrates.SUMMARY

[0008] In light of the above, a method and apparatuses for testing a packaging substrate are provided according to the independent claims. Further aspects, advantages, and beneficial features are apparent from the dependent claims, the description, and the accompanying drawings.

[0009] According to an embodiment, a method of testing a packaging substrate with at least one charged particle beam column is provided. The method includes placing the packaging substrate on a stage in a vacuum chamber; blanking a charged particle beam of the at least one charged particle beam column at a first position on the packing substrate; vector scanning the charged particle beam from the first position on the packaging substrate to a second position on the packaging substrate while the charged particle beam is blanked, the vector scanning being based upon a first calibration of one or more charged particle beam properties of the charged particle beam and being based upon a second calibration of a beam position of the charged particle beam; un-blanking the charged particle beam onto the second position; blanking the charged particle beam at the second position; vector scanning the charged particle beam from the second position to a third position on the packaging substrate while the charged particle beam is blanked, the vector scanning being based upon the first calibration and the second calibration; and testing one or more networks on the packaging substrate in the vacuum chamber based upon signals received from at least the third position.

[0010] According to an embodiment, a method of operating an apparatus for testing of a packaging substrate is provided. The method includes placing a substrate in a stage of the apparatus; guiding a charged particle beam of a charged particle beam column sequentially onto a plurality of first positions, the plurality of first positions extending over a field of view of 70 mm or above; for each of the plurality of first positions, adjusting at least one of lens assembly to a calibrated first focus value and a stigmator to a calibrated first astigmation correction value; guiding the charged particle beam sequentially onto a plurality of second positions, the plurality of second positions extending over a field of view of 70 mm or above; for each of the plurality of second positions, setting least one of the lens assembly to at a calibratedsecond focus value and the stigmator to a calibrated second astigmation correction value, and imaging an area at each of the second positions; and based on the imaged areas resulting from the plurality of second position, calibrating one or more deflector stages to determine calibrated position values.

[0011] According to an embodiment, an apparatus for testing of a packaging substrate is provided. The apparatus includes a vacuum chamber; a stage within the vacuum chamber, the stage being configured to support the packaging substrate; a charged particle beam column configured to generate a charged particle beam, the charged particle beam column comprising: a lens assembly with a first an objective lens configured to focus the charged particle beam on the packaging substrate and a second objective lens to focus the charged particle beam on the packaging substrate; a first scanner stage configured to scan the charged particle beam to different positions on the packaging substrate and a second scanner stage configured to scan the charged particle beam to different positions on the packaging substrate; and an electron detector for detecting signal electrons emitted upon impingement of the charged particle beam on the packaging substrate; a beam blanker configured to blank or un-blank the charged particle beam; and a controller having a processor and a memory, storing instructions that, when executed by the processor, cause the apparatus to perform a method according to any of the embodiments of the present disclosure.

[0012] Embodiments are also directed at apparatuses for carrying out the disclosed methods and include apparatus parts for performing each described method aspect. Method aspects may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments according to the disclosure are also directed at methods for operating the described apparatus and a method for manufacturing the apparatuses and devices is described herein. The methods for operating the described apparatus include method aspects for carrying out functions of the apparatus.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] So that the manner in which the above recited features 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. The accompanying drawings relate to embodiments of the disclosure and are described in the following:

[0014] FIG. 1 shows a schematic sectional view of an apparatus for testing a packaging substrate in accordance with any of the testing methods described herein;

[0015] FIG. 2A shows a schematic view of a packaging substrate having test points thereon and a charged particle beam scanning over the packaging substrate as a line-scan and a corresponding schematic signal graph, wherein a signal-to-noise ratio is indicated;

[0016] FIG. 2B shows a schematic view of a packaging substrate having test points thereon and a charged particle beam scanning over the packaging substrate as a vector scan according to embodiments of the present disclosure and a corresponding schematic signal graph, wherein an improved signal-to-noise ratio is indicated;

[0017] FIG. 3A shows a schematic view of a field of view with a plurality of exemplary charged particle beam positions on the packaging substrates for a first calibration;

[0018] FIG. 3B shows a schematic view of a field of view with a plurality of exemplary positioning marks on a substrate for a second calibration;

[0019] FIGS. 4A and 4B show enlarged sectional views of packaging substrates during any of the testing methods described herein;

[0020] FIG. 5 shows an enlarged top view of a packaging substrate during any of the testing methods described herein;

[0021] FIGS. 6A-6D show enlarged sectional views of packaging substrates that can be tested according to the methods described herein;

[0022] FIG. 7 shows a flowchart of a method of testing a packaging substrate according to embodiments described herein; and

[0023] FIG. 8 shows a flowchart of a method of operating a charged particle beam column for testing of a packaging substrate according to embodiments described herein.DETAILED DESCRIPTION

[0024] 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.

[0025] 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 to provide better understanding of the embodiments.

[0026] Embodiments of the present disclosure relate to testing and / or defect review for packaging substrates, i.e. panel-leveling packing (PLP) substrates or advanced packaging (AP) substrates, according to methods as described herein.

[0027] For contactless testing of the packaging substrate, at least one charged particle beam is used for writing and reading charges on the packaging substrate, particularly for identifying and characterizing defects such as shorts, opens, and / or leakages. A contactless electrical test with a charged particle beam can be provided, wherein a voltage signal reading (e.g. voltage contrast by signal electron sensing)is provided. According to some embodiments, which can be combined with other embodiments described herein, the voltage contrasts on the packaging substrate may be determined by detection of signal electrons. According to some embodiments, which can be combined other embodiments described herein, the signal electrons may particularly be secondary electrons.

[0028] Further, test point or contact points can be charged contactless on a packaging substrate, such as an AP or PLP substrate. Contactless testing avoids or reduces damage to the AP / PLP substrate. Detection and classification of electrical defects is enabled. In order to further improve the voltage contrast in the methods according to embodiments of the present disclosure, and the apparatuses according to embodiments of the present disclosure, charges on areas of the packaging substrate, which are not to be charged are reduced or avoided. According to some embodiments, a charged particle beam is positioned onto various positions of the packaging substrate with a vector scan method, wherein the beam is blanked (deflected away or switched off) between moving from a first position on the packaging substrate to a second, subsequent position on the packaging substrate. According to some embodiments, which can be combined with other embodiments described herein, a plus of a charged particle beam is provided at the desired location, e.g. a first position on a packaging substrate and further positions on the packaging substrate. According to some embodiments, which can be combined with other embodiments described herein, the vector scanning is provided on a comparably large field of view, for example, the field of view having a size of at least 70 mm or above. Accordingly, improved vector scanning with beam planking and an improved beam positioning can be provided for testing of a packaging substrate.

[0029] The vector scan method according to embodiments of the present disclosure, improves the signal-to-noise ratio (S / N-ratio) and the signal difference between good and defect networks, contact pads or contact electrodes. The charged particle beam is turned off or blanked while the deflection system positions on the next to be tested contact pad, i.e. surface contact electrode, on the panel or wafer or another advanced packaging substrate. According to some embodiments, a blanking and un-blanking of the beam with a deflector is beneficial as compared toswitching the beam on and switching the beam off. For example, some emitters like a thermal field emitter or a cold field emitter have a better performance under stable conditions. The charged particle beam is pulsed on for a defined time and turned off again. The charged particle beam is only hitting the contact pads or contact electrodes and does not expose the dielectric material in-between. According to some embodiments, which can be combined with other embodiments described herein, the charged particle beam is only hitting conductive areas of the packaging substrate. The electron is not hitting dielectric material of the packaging substrate.

[0030] According to an embodiment, a method of testing a packaging substrate with at least one charged particle beam column is described herein. The method includes placing the packaging substrate on a stage in a vacuum chamber. Further, the method includes blanking a charged particle beam of the at least one charged particle beam column at a first position on the packing substrate and vector scanning the charged particle beam from the first position on the packaging substrate to a second position on the packaging substrate while the charged particle beam is blanked. The vector scanning is based upon a first calibration of one or more charged particle beam properties of the charged particle beam and is based upon a second calibration of a beam position of the charged particle beam. The method further includes directing the charged particle beam onto the second position, blanking the charged particle beam at the second position and vector scanning the charged particle beam from the second position to a third position on the packaging substrate while the charged particle beam is blanked. The vector scanning is based upon the first calibration and the second calibration. Further, testing one or more networks on the packaging substrate in the vacuum chamber is provided based upon signals received from at least one of the second position and the third position. For example, each of the first position, the second position and the third position are portions of the one or more networks.

[0031] For embodiments of the present disclosure it is beneficial if the charged particle beam is precisely blanked (or turned on / off). The charged particle beam is beneficially positioned accurately to hit only the contact pad, i.e. surface contact electrode. The charged particle beam is aligned on the packaging substrate, andbased upon the position calibration procedure according to embodiments of the present disclosure. According to some embodiments, which can be combined with other embodiments described herein, the position calibration procedure compensates for several charged particle beam position deviations and particularly, for all charged particle beam position deviations, for example, including test substrate position errors and distortions. Further, the focus and / or shape of the charged particle beam is well-defined and, particularly under all deflection conditions, i.e. large or small charged particle beam deflection angles.

[0032] According to some embodiments, substrate warping may additionally be compensated by providing a distortion alignment specific to a sample, i.e. measuring alignment marks on a sample with a predetermined warping. The position calibration can by modified with a sample specific distortion transformation.

[0033] According to some embodiments, which can be combined with other embodiments described herein, the test, particularly an electrical test of a packaging substrate, is provided by voltage signal reading, for example, sensing the voltage contrast of signal electrons, such as secondary electrons. Further, the contact pads, i.e. the surface contact electrodes and / or the networks (the test points) can be charged with the charged particle beam.

[0034] The energy of the signal electrons, for example, the secondary electrons depend on the potential of the position of release of the signal electron, for example, the starting electrode potential. Accordingly, the signal electrons can be used to measure and / or evaluate the potential of the substrate position, for example, the test electrode potential, by voltage contrast (VC). According to embodiments of the present disclosure, the defect detection can be improved, e.g. less false defects are detected, by improving, e.g. enlarging, the signal difference between good and defective contact pads and / or networks. In other words, the noise signal can be reduced. If the signal difference, e.g. the SE signal difference, between good and defect is low, some defects might not be found within the higher signal noise.

[0035] The defect signal also depends on the signal to noise ratio (S / N-ratio). The S / N-ratio is inter alia depending on surface charging effects caused by scanning acharged particle beam. Particularly for dielectric materials, which electrically separate the surface contact electrodes and / or networks on the PLP / AP substrates, the surface charging occurs. Accordingly, a standard SEM scan (line by line to scan an area) exposes the contact electrodes as well as the dielectric material and introduces surface charge. The surface charge influences the signal electrons, e.g. the SE signal, in particular the SE energy and disturbs the voltage contrast and, thus, the S / N-ratio. Poorer defect detection and false defect detection may result. Compared to display substrates, the ratio of dielectric material to conducive electrodes, e.g. on average, is reduced for packaging substrates (display device: dielectric to conductor about < 1 / 5, Packaging substrate: dielectric to conductor about > 1 :2, or only even 1 :1 ). Accordingly, embodiments of the present disclosure are particularly useful for packaging substrates, for which the noise effect is more serious.

[0036] FIG. 1 shows a schematic view of an apparatus according to embodiments of the present disclosure and illustrates the concept of charge reduction on dielectric material according to embodiments described herein. A packaging substrate 10 is supported on a stage 105. The packaging substrate is supported in the vacuum chamber 110. According to some embodiments, which can be combined with other embodiments described herein, the packaging substrate 10 can be placed on the stage 105 being on ground potential.

[0037] In the following, reference is made to an electron beam of an electron beam column. A person skilled in the art can understand that the embodiments can be modified by using a charged particle beam of a charged particle beam column, wherein, for example, ions are utilized as primary charged particles and electrons are utilized as signal charged particles.

[0038] As is schematically depicted in FIG. 1 , the electron beam column 120 may be provided on a first side of the stage 105. The electron beam column 120 has an electron source 121 for generating an electron beam. The beam is accelerated and guided towards the packaging substrate 10. As it is schematically depicted in FIG. 1 , the electron source 121 is connected to a power supply 130. The power supply can provide a high-voltage to the electron source for emitting the electron beam, i.e.the primary electron beam, from the electron source. According to some embodiments, which can be combined with other embodiments described herein, the voltage provided by the power supply 130 can be varied to change the energy of the electron beam and, thus, the landing energy of the electron beam on the packaging substrate.

[0039] According to some embodiments, which can be combined with other embodiments described herein, a stigmator 126 is provided. The stigmator 126 is configured to reduce astigmatism. Astigmatism can be generated in one or more of the beam optical components of the electron beam column 120. The stigmator is controlled, e.g. by controller 180, to adjust the shape of the electron beam on the packaging substrate, particularly at various positions on the packaging substrates, i.e. at large and small deflection angles of the electron beam. The shape of the beam is adjusted at positions extending over the field of view (FOV) on the packaging substrate.

[0040] A scan deflector 122 is provided. The scan deflector 122 can provide a first scanning stage for deflecting the beam over a first area on the packaging substrate. A second scanning stage for deflecting the beam over a second area on the packaging substrate can be provided according to some embodiments. The second stage can be provided by a second scan deflector 125. According to some embodiments, the deflection fields of scan deflector 122 and the second scan deflector 125 may partially overlap or may be adjacent to each other. The second stage can be operated to scan over the second area, which is smaller than the first area. Accordingly, a large scanning area and a smaller scanning area, which is added to the larger scanning area, can be provided. By providing a two-stage scanning, a large FOV can be provided while having a precise electron beam positioning.

[0041] A first plurality of electrodes 146 can generate a multi-pole field, for example, an octupole field, to guide the signal electrons 113 towards the electron detector 140. For example, the first plurality of electrodes can include eight or more electrodes for generating an octupole field. Particularly, the multi-pole field generated by the first plurality of electrodes 146 can be dynamically adjusted to theposition of the electron beam 111 on the packaging substrate 10. The second plurality of electrodes 148 can generate a multi-pole field, for example, an octupole field, to guide the signal electrons 113 towards the electron detector 140. For example, the second plurality of electrodes can include eight or more electrodes for generating an octupole field. Particularly, the multi-pole field generated by the second plurality of electrodes 148 can be static. According to some embodiments, which can be combined with other embodiments described herein, one or more electrodes in the electron beam column 120 can be at least one assembly of four or eight electrodes (or more electrodes), configured to generate a multipole field for guiding signal electrons. As shown in FIG. 1 , the one or more electrodes 154 having the first plurality of electrodes 146 and the second plurality of electrodes 148 can be integrated in the electron beam column 120.

[0042] In some embodiments, the apparatus 100 may include a scan controller 123 connected to a scan deflector 122 of the electron beam column 120 and the second scan deflector 125. The scan deflector 122 and the second scan deflector may be configured to vector scan the electron beam onto a substrate surface.

[0043] According to some embodiments, which can be combined with other embodiments described herein, a beam dump 128 can be provided. The beam dump is configured to block the electron beam, which may be deflected by a further deflector (shown without a reference numeral) towards the beam dump, e.g. into the beam dump 128. The further deflector can be an electrostatic deflector. The electron beam can be deflected into the beam dump for blanking of the electron beam. An aperture can be provided to allow for fast switching of the electron beam by deflecting the electron beam towards the beam dump. Accordingly, a beam blanker configured to switch the electron beam on or off, particularly to switch the electron beam on or off in the plane of the packaging substrate can be provided.

[0044] In the present disclosure, reference is made to “blanking” and “un-blanking” of the electron beam. Blanking of the electron beam is understood as deflecting the electron beam, particularly within the electron beam column, e.g. away from the optical axis. The beam can be deflected, e.g. in a beam dump. Further, blanking of the electron beam can be understood as switching off the electron beam, e.g. byreducing the extraction voltage at the electron source. Un-blanking of the electron beam is understood as deflecting the electron beam onto the optical axis, particularly within the electron beam column. The beam can be deflected, e.g. out of a beam dump. Further, un-blanking of the electron beam can be understood as switching on the electron beam, e.g. by increasing the extraction voltage at the electron source back to normal operation.

[0045] Electron beam testing offers a suitable solution as it allows testing of test points smaller than 60 pm or 10 pm, or even below. It is capable of voltage contrast imaging. The test structures can be charged positive or negative by the electron beam impact, and the test point potential can be determined by the voltage contrast principle for defect detection and sample parameter monitoring (such as capacitance, resistance, etc.)

[0046] Further, the electron beam column, further includes a lens assembly 124 with a first objective lens configured to focus the electron beam on the packaging substrate and, optionally, a second objective lens to focus the electron beam on the packaging substrate. FIG. 1 shows a smaller, second objective lens being provided at a similar position than the first objective lens. The objective lenses may be electrostatic, magnetic, or a magnetic-electrostatic. The first objective lens can have a stronger focusing strength than the second objective lens, e.g. the first objective lens can be configured to have a stronger focusing strength than the second objective lens. Accordingly, coarse focusing can be provided by the first objective lens and fine focusing can be provided by the second objective lens. Yet further, according to some embodiments, which can be combined with other embodiments described herein, the second objective lens can be faster than the first objective lens, i.e. a change of the focusing strength can be changed faster. According to some embodiments, which can be combined with other embodiments described herein, the second objective lens is configured for a smaller hysteresis as compared to the second objective lens. By providing two objective lenses, a large FOV can be provided while having a precise focus control of the electron beam.

[0047] The apparatus 100 further includes an electron detector 140 for detecting signal electrons 113, e.g. secondary electrons, emitted upon impingement of theelectron beam on the packaging substrate, and an analysis unit 141 configured to determine, based on the signal electrons 113, if e.g. a device-to-device electrical interconnect path 20 of the packaging substrate is defective.

[0048] According to an embodiment, an apparatus for testing, e.g. for contactless testing, of a packaging substrate is provided. The apparatus includes a vacuum chamber and a stage within the vacuum chamber. The stage is configured to support the packaging substrate. The apparatus includes an electron beam column configured to generate an electron beam. The electron beam column includes a lens assembly with a first objective lens configured to focus the electron beam on the packaging substrate and a second objective lens to focus the electron beam on the packaging substrate. The electron beam column includes a first scanner stage configured to scan the electron beam to different positions on the packaging substrate and a second scanner stage configured to scan the electron beam to different positions on the packaging substrate. The electron beam column includes an electron detector for detecting signal electrons emitted upon impingement of the electron beam on the packaging substrate and a beam blanker configured to switch the electron beam on or off, particularly in the plane of the packaging substrate. The electron beam column includes a controller having a processor and a memory, storing instructions that, when executed by the processor, cause the apparatus to perform a method according to any of the embodiments of the present disclosure. An analysis unit 141 can be provided. The analysis unit determines, based on the signal electrons, if, for example, a device-to-device electrical interconnect path is defective.

[0049] According to some embodiments, which can be combined with other embodiments described herein, the first objective lens is configured for a larger focusing strength than the second focusing strength, and wherein the second objective lens is configured for a smaller hysteresis as compared to the first objective lens. According to some embodiments, which can be combined with other embodiments described herein, the first scanner stage can be a magnetic scanner stage and the second scanner stage can be an electrostatic scanner stage.

[0050] FIGS. 2A and 2B show a packaging substrate 10 having surface contact points (e.g. first surface contact point 21 ) or contact pads of networks for testing of the packaging substrate. An exemplary test sequence and a schematic signal for detecting, for example, secondary electrons are shown. For FIG. 2A, the electron beam 111 is scanned over the surface of the packaging substrate. Particularly, the contact pads are exposed to the electron beam 111 during a line-scan of the electron beam. As schematically illustrated in FIGS. 2A and 2B, a defect exemplarily shown as a short 28 between a contact pad and a neighboring contact pad may occur. For the example shown in FIG. 2A, the electron beam 111 impinges on the contact pads and on the dielectric material of the packaging substrate. The measurement result of 4 exemplary contact pads numbered as 1-4 is shown schematically as a reading of a secondary electron signal. Upon charging of a network, the contact pads numbered as 1 , 3, and 4 show the proper signal height 213 indicative of a charge provided to the network. In light of the short 28, between neighboring contact pads, the contact pad numbered as 2 has a low signal height 211 , indicating a defect. However, due to charges applied to dielectric material, the overall noise is comparably high. Accordingly, the difference between the low signal height 211 and the proper signal height 213, i.e. the signal indicative of a defective connection and a signal indicative of a good connection, is comparably low. In other words, the signal-to-noise ratio is low, which is illustrated by the arrow between the low signal height 211 and the proper signal height 213, which is smaller as compared to FIG. 2B.

[0051] FIG. 2B shows a similar scenario as compared to FIG. 2A, however with a method of testing according to embodiments of the present disclosure and including vector scanning and beam blanking. At a first position, for example at the position of contact pad numbered as 1 , the electron beam is blanked (deflected away or switched off) after measuring the contact pad numbered as 1 . The electron beam 111 is vector scanned to a second position. For example, the second position can be any of the positions of contact pads numbered as 2, 3, or 4. The electron beam 111 is unblanked (deflected on-axis or switched on). For example, the electron beam can be unblanked (deflected on-axis or switched on) for a period of time. A pulse of an electron beam can be provided on the second position. The electronbeam is only directed to contact pads, i.e. tests electrodes of, for example networks. Based upon such proper beam control, charging of dielectric material is reduced or avoided. Accordingly, the difference between a low signal height 211 and the proper signal height 213, i.e. the signal indicative of a defect defective connection and the signal indicative of a good connection, can be increased. In other words, the signal- to-noise ratio is higher, which is illustrated by the arrow between the low signal height 211 and the proper signal height 213.

[0052] According to embodiments of the present disclosure, an improved vector scanning with beam planking and improved beam positioning can be provided for testing of a packaging substrate. FIG. 3A and 3B each show a portion of a packaging substrate 10 and an exemplary field of view 310 of an electron beam column, illustrating an area, which can, for example, be tested without a relative movement of an optical axis of the electron beam column and the packaging substrate, i.e. without moving the electron beam column or the packaging substrate to guide the electron beam onto a different position or area of the packaging substrate. According to some embodiments, which can be combined with other embodiments described herein, the field of view can have a size of at least 70 mm or above. Particularly, the field of view is orders of magnitude larger as compared to a scanning electron microscope. According to some embodiments, which can be combined with other embodiments described herein, the field of view (FOV) can be 150 mm or below. Accordingly, the field of view can be smaller than a field of view of a display testing with e.g. 200 mm or 300 mm field of view.

[0053] FIG. 3A shows a plurality of positions 312 within the field of view 310. For example, the position 312 can be regularly distributed over the field of view. Alternatively, as distortions and aberrations might increase for larger deflection angles, the density of positions 312 might increase towards the edge of the field of view.

[0054] The charged particle beam is deflected with the scan deflector, for example, the first scanning stage and the second scanning stage, onto each of the positions 312. For each of the positions, the lens assembly is adjusted to a calibrated first focus value. The focus strength is optimized for each of the positions within therange that may be, for example, achieved with an autofocus routine. Additionally or alternatively, for each of the positions, the stigmator is adjusted to a calibrated first astigmatism correction value. According to some embodiments, which can be combined with other embodiments described herein, further parameters of the electron beam column can be varied to provide further parameters for the first calibration of the electron beam column. The calibration values can be provided, for example, in the lookup table such that an interpolation between each of the positions of the plurality of positions 312 can be provided. Accordingly, the first calibration is provided, which allows for an improved or optimized electron beam spot on the packaging substrate within the field of view 310, and particularly for each position within the FOV.

[0055] FIG. 3B shows a plurality of calibration marks 314 or positioning marks within a field of view 310. For example, the calibration marks 314 can be regularly distributed over the field of view. Alternatively, as distortions might increase for larger scan deflection angles, the density of the calibration marks 314 might increase towards the edge of the field of view.

[0056] The charged particle beam is deflected with the scan deflector, for example, the first scanning stage and the second scanning stage, to be positioned on each of the calibration marks 314. The lens assembly, the stigmator and / or further parameters are set on the calibrated values corresponding to the position of the electron beam. Accordingly, based on the first calibration, an improved or optimized electron beam spot on the packaging substrate is provided for the position of the respective calibration mark 314. According to some embodiments, which can be combined with other embodiments described herein, at least one of the lens assembly is set to at a calibrated second focus value and the stigmator is set to a calibrated second astigmation correction value. The area of the calibration mark can be imaged at the respective second positions of the calibration mark. The calibrated position of the electron beam can be provided by the image of the calibration mark. Accordingly, for each of the positions in the FOV, a second calibration of the beam position can be provided. The calibrated second focus value and the calibrated second assignation correction value may, for example, be provided by aninterpolation of positions 312 shown in FIG. 3A that are neighboring the position of the calibration mark 314.

[0057] According to some embodiments, which can be combined with other embodiments described herein, the calibrated second focus value can be based on one or more calibrated first focus values of one or more first positions at or adjacent to a corresponding second position of the plurality of second positions. Additionally or alternatively, the calibrated second astigmation correction value can be based on one or more calibrated first astigmation correction values of the one or more first positions at, or adjacent to, the corresponding second position of the plurality of second positions. An interpolation may be provided by a look up table.

[0058] In light of embodiments described herein, the first calibration influencing the second position calibration is provided. The first calibration is considered for the second calibration. Accordingly, an improved vector scanning over a large FOV can be provided, particularly for packaging substrate to avoid charging of dielectric material.

[0059] According to an embodiment, a method of testing a packaging substrate with at least one electron beam column is provided. The method includes placing the packaging substrate on a stage in a vacuum chamber and blanking an electron beam of the at least one electron beam column at a first position on the packing substrate. Thereafter the electron beam is vector scanned from the first position on the packaging substrate to a second position on the packaging substrate while the electron beam is blanked. The vector scanning is based upon a first calibration of one or more electron beam properties of the electron beam and is based upon a second calibration of a beam position of the electron beam. The electron beam is directed onto the second position, e.g. by unblanking of the electron beam. Thereafter the electron beam is blanked at the second position and is vector scanned from the second position to a third position on the packaging substrate while the electron beam is blanked, wherein the vector scanning is based upon the first calibration and the second calibration. One or more networks on the packaging substrate in the vacuum chamber are tested based upon signals received from at least the third position.

[0060] FIG. 7 shows a method of testing a packaging substrate. For improved vector scanning according to embodiments of the present disclosure and for testing of packaging substrate, an electron beam is blanked at a first position on the substrate, as shown by operation 702. Thereafter, at operation 704, the electron beam is vector scanned from the first position to a second position based on the first calibration and based on the second calibration. Accordingly, an improved or optimized beam spot can be provided at the second position and an improved or optimized beam position can be provided to direct the electron beam onto the second position. The electron beam is directed onto the second position. For example, an electron beam pulse can be provided for the period of time to provide a charge on the second position and / or to release signal electrons to obtain a signal reading for testing of one or more networks. According to some embodiments, which can be combined with other embodiments described herein, a method of testing may include pulsing the electron beam for a period of time while being directed onto the second position. At operation 706, a measurement can be conducted on the second position with the electron beam, i.e. as a contactless testing. Thereafter, at operation 708 the electron beam is blanked at the second position. Thereafter, at operation 710, the electron beam is vector scanned from the second position to a third position based on the first calibration and based on the second calibration. The third position can be a position adjacent to the second position, for example, the position of a contact pad adjacent to the contact pad of the second position. The third position can be any arbitrary position on the packaging substrate, and particularly the position of any contact pad, surface contact electrode, or test electrode (or even another position of a conductive material on the packaging substrate). According to some embodiments, which can be combined with other embodiments described herein, vector scanning results in positioning of the electron beam on an arbitrary sequence of positions on the packaging substrate. At operation 712, a measurement is provided at the third position with the electron beam, particularly a contactless measurement. At operation 714 at least one network is tested based upon signal readings from signal electrons, for example, secondary electrons.

[0061] According to some embodiments, which can be combined with other embodiments as described herein, each of the first position, the second position anda third position are portions of one or more networks to be tested. Accordingly, vector scanning is provided from and to positions of conductive material. The beam is blanked for scan deflector values that correspond to positions of dielectric material. For embodiments of the present disclosure, a ratio of dielectric areas of the packaging substrate and conductive areas of the packing substrate can be equal to or larger than 1 :3. Thus, the effect of beam blanking is particularly beneficial for packaging substrate.

[0062] According to some embodiments, which can be combined with other embodiments described herein, the beam diameter on the packaging substrate, i.e. when the electron beam is directed and / or pulsed onto the contact pads, i.e. the surface contact electrodes, is 1 pm or above. According to some embodiments, which can be combined with other embodiments described herein, the mean diameter can be 10% of the size of the contact pad or larger. Having a large process enables higher current densities which, in turn, allows for higher throughput. For example, the beam current of the electron beam can be 200 nm or above.

[0063] According to some embodiments, which can be combined with other embodiments described herein, basing the vector scanning of the first calibration includes adjusting at least one of a stigmator and the lens assembly. Particularly, the stigmator and the lens assembly are adjusted with values of the first calibration. Thus, the shape of the electron beam on the packaging substrate can be controlled dependent on the electron beam position. Further parameters, such as the electron beam energy may additionally be included in the first calibration. According to some embodiments, basing the vector scanning on the first calibration may include reading parameters from lookup tables. According to some embodiments, which can be combined with other embodiments described herein, basing the vector scanning on the second calibration includes adjusting at least one of the first deflection stage in the second deflection stage. Electron beam positioning can be provided based on the second calibration. This may include reading parameters of the first deflection stage and / or the second deflection stage from lookup table.

[0064] According to an embodiment, a method of operating an apparatus for testing of a packaging substrate is provided. The method includes placing a substrate in astage of the apparatus and guiding an electron beam of an electron beam column sequentially onto a plurality of first positions, the plurality of first positions extending over a field of view of 70 mm or above. For example, the substrate can be a calibration sample with a plurality of predetermined features or calibration marks (see FIG. 3B), particularly known and / or designed features. The known and / or designed features or calibration marks serve for the calibration. For each of the plurality of first positions, at least one of lens assembly is adjusted to a calibrated first focus value and a stigmator is adjusted to a calibrated first astigmation correction value. The method further includes guiding the electron beam sequentially onto a plurality of second positions, the plurality of second positions extending over a field of view of 70 mm or above. For each of the plurality of second positions, the lens assembly is set to at least one of a calibrated second focus value and the stigmator to a calibrated second astigmation correction value. The method further includes imaging an area at each of the second positions and, based on the imaged areas resulting from the plurality of second position, calibrating one or more deflector stages to determine calibrated position values.

[0065] FIG. 8 shows a flow chart illustrating a method of operating an apparatus for testing of a packaging substrate. At least one of a stigmator and a lens assembly is calibrated for a plurality of first positions in a large field of view, e.g. a rectangular FOV of with a minimum side dimension of 70 mm or above at operation 802. Accordingly, for each of the first positions, focus values and or astigmatism correction values are calibrated, i.e. preferred values are determined based on a calibration. Thereafter, at operation 804, the electron beam is guided to a plurality of second positions. For each of the plurality of second positions, the stigmator and the lens assembly are adjusted to calibrated second values at operation 806. For example, the calibrated second values can be an interpolation of the calibrated first values. For example, a lookup table may be utilized. With a proper electron beam spot for each of the second positions, the scan deflector(s) can be calibrated for each of the second positions at operation 808. The second calibration of the position of the electron beam can be provided utilizing calibrated values for the first calibration, i.e. the first calibration improving and / or optimizing the beam spot.

[0066] According to some embodiments, which can be combined with other embodiments described herein, a calibrated second focus value can be based on one or more calibrated first focus values of one or more first positions at, or adjacent to, a corresponding second position of the plurality of second positions. Additionally or alternatively, the calibrated second astigmatism correction value is based on one or more calibrated first astigmatism correction values of the one or more first positions at, or adjacent to, the corresponding second positions of the plurality of second positions.

[0067] As shown in FIG. 8, at operation 810, the method of operating an electron beam column for testing of a packaging substrate may continue at operation 702 of FIG. 7 with a method of testing a packaging substrate according to any of the embodiments of the present disclosure. For testing a packing substrate, a first calibration and a second calibration are utilized. The first calibration for vector scanning can include the calibrated first focus value and the calibrated first astigmation correction value and the second calibration for vector scanning can include the calibrated position values.

[0068] As described with respect to FIG. 1 and FIGS. 7 and 8, a method of testing a packaging substrate is provided. The packaging substrate is a panel level packaging substrate or an advanced packaging substrate, the method being conducted with at least one charged particle beam column.

[0069] The complexity of packaging substrates has been increasing for years, with the aim of reducing the space requirements of semiconductor packages. For reducing the manufacturing costs, packaging techniques were proposed, such as 2.5D ICs, 3D-ICs, and wafer-level packaging (WLP), e g. fan-out WLP. In WLP techniques, the integrated circuit is packaged before dicing. A “packaging substrate” as used herein relates to a packaging substrate configured for an advanced packaging technique, particularly an WLP-technique or a panel-level-packing (PLP)- technique.

[0070] “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 areplaced on a packaging substrate, e.g. on a silicon interposer or a panel-level- packaging substrate. In 2.5D ICs, the dies are placed on the packaging substrate side-by-side, whereas in 3D ICs at least some of the dies are placed on top of each other. The assembly can be packaged as a single component, which reduces costs and size as compared to a conventional 2D circuit board assembly.

[0071] A packaging substrate typically includes a plurality of device-to-device electrical interconnect paths for providing electrical connections between the chips or dies that are to be placed on the packaging substrate. The device-to-device electrical interconnect paths may extend through a body of the packaging substrate in a complex connection network, vertically (perpendicular to the surface of the packaging substrate) and / or horizontally (parallel to the surface of the packaging substrate) with end points (referred to herein as surface contact points) exposed at the surface of the packing substrate.

[0072] An advanced packaging (AP) substrate provides the device-to-device electrical interconnect paths on, or within, a wafer, such as a silicon wafer. For example, an AP substrate may include Through Silicon Vias (TSVs), e.g. provided in a silicon interposer, other conductor lines extending through the AP substrate. A panel-level-packaging substrate is provided from a compound material including, for example, ceramics and glass materials.

[0073] PLP substrates are manufactured that are configured for the integration of a plurality devices (e.g., chips / dies that may be heterogeneous, e.g. may have different sizes and configurations) in a single integrated package. Further, AP substrates may be combined on a PLP substrate. A panel-level substrate typically provides sites for a plurality of chips, dies, or AP substrates to be placed on a surface thereof, e.g. on one side thereof or on both sides thereof, as well as a plurality of device-to-device electrical interconnect paths extending through a body of the PLP substrate.

[0074] Embodiments of the present disclosure relate in particular to an advanced packaging substrate or a panel level packaging substrate. As compared to printed circuit boards, a packaging substrate configured for embodiments of the presentdisclosure or used in embodiments of the present disclosure can have contact pads or surface contact electrodes with an elevated structure, such as bumps or other convexly shaped contact surfaces. The contact surfaces are contact pads and are convexly shaped before a solder connection is added.

[0075] Further, the packaging substrates according to embodiments of the present disclosure may include different materials, for example, semiconductor material, ceramics, or glass as compared to printed circuit boards. Thus, different charging effects of an electron beam hitting non-conductive areas or non-network areas are given, such that an improved vector scanning according to embodiments of the present disclosure is beneficial. Additionally or alternatively, active or passive electronic components, for example, capacitors, coils, transformers or transistors may be included or embedded in the packaging substrate. In addition, a variety of further active and passive components could be embedded in the substrates, which also require electrical tests. Yet further, the line width of electrical interconnect paths can be 20 pm or below, e.g. in a range of 20 pm down to 2pm, or even below. Additionally or alternatively, the size of contact pads can be of 60 pm or below or even about 10 pm or below. Accordingly, as compared to a printed circuit board, the failure rate characteristics of an AP / PLP substrate is more critical. Embodiments of the present disclosure allow for an improved vector scanning. The coating and etching (structuring) processes in AP / PLP manufacturing are more complex as compared to PCB boards and create more potential process related electrical failures. Additionally, embedded active and passive electrical components, such as a capacitor or other devices, create more defect potential and are more sensitive to failure. Due to the higher value of the later mounted semiconductor devices, the AP / PLP substrates electrical test of all nets and embedded components is beneficial. Standard PCBs can be tested by a needle tester since a mechanical damaged contact pad (scratches by needle) does not cause significant yield loss. On AP / PLP the contact size is so small that any scratch causes reduced connectivity and yield loss, particularly for convexly shaped contact pads.

[0076] Notably, the size of a panel-level-substrate is not lim ited to the size of a wafer. For example, a panel-level-substrate may be rectangular or have another shape.Specifically, a panel-level-substrate may provide a surface area larger than the surface area of a typical wafer, e.g., 1000 cm2or more. For example, the panel-level substrate may have a size of 30 cm x 30 cm or larger, 60 cm x 30 cm or larger, 60 cm x 60 cm or larger.

[0077] According to embodiments of the present disclosure, electron beam testing and / or electron beam review provides for testing of contact pads of 60 pm or below or even about 10 pm or below. Voltage contrast testing imaging can be provided. Testing can be provided at or between “surface contact points” of the packaging substrate.

[0078] A “surface contact point” or “contact pad” may be understood as an end point of an electrical interconnect path that is exposed at a surface of the packaging substrate, such that an electron beam can be directed on the surface contact point for contactless charging or probing the electrical interconnect path. A surface contact point is configured to electrically contact a chip, a die, a smaller package, or other electrical components like capacitors, resistors, coils, or the like, that is to be placed on the surface of the packaging substrate, e g. via soldering. Electrical components may also include active electrical components, such as a transformer changing the voltage in a region of the package.

[0079] According to embodiments of the present disclosure, 100% of the electrical interconnect paths are tested. The costs of ownership of device packages including the chips etc. such as processors, memories, or the like (microelectronic devices), is mainly determined by the highly integrated microelectronic devices. Accordingly, mounting a non-defective microelectronic device to a defective packaging substrate is disadvantageous with respect to manufacturing cost. A fully non-defective packaging substrate is desirable before mounting of the microelectronic devices.

[0080] According to some embodiments, which can be combined with other embodiments described herein, a charge control during writing of a charge can be provided by operating the electron beam column with a defined landing energy. Particularly, the landing energy, i.e. the energy of the electron beam upon impingement of the packaging substrate, can be varied to control the chargeprovided on the packaging substrate. By variation of the landing energy, an area of impingement of the electron beam can be charged positively, negatively, or not charged. During a writing operation, no charge is beneficially provided to the packaging substrate. A contactless electrical test can be provided with an electron beam, wherein the charge can be at, for example, a first surface contact point, and charge can be read at, for example, a second surface contact point. This enables the detection and classification of electrical defects of the packaging substrate. The different electron beam landing energies (Upe) control the SE yield (secondary electron yield) and, thus, the total electron yield.

[0081] As it is schematically depicted in FIG. 1 , a packaging substrate 10 includes a first device-to-device electrical interconnect path 20 extending between a first surface contact point 21 and a second surface contact point 22 of the packaging substrate 10. Optionally, the first device-to-device electrical interconnect path 20 may extend between three or more surface contact points that may be provided on the same surface or on two opposite surfaces of the packaging substrate. The device-to-device electrical interconnect path 20 depicted in FIG. 1 extends only between the first surface contact point 21 and the second surface contact point 22. Both are arranged at a top surface of the packaging substrate, but the present disclosure is not limited to such device-to-device electrical interconnect paths, and the device-to-device electrical interconnect path may be a complex network of vias, pillars, and / or conductor lines extending through the packaging substrate, with a plurality of surface contact points.

[0082] The packaging substrate 10 may include a plurality of device-to-device electrical interconnect paths for connecting a plurality of devices that are to be placed on the packaging substrate 10. In FIG. 1 , three device-to-device electrical interconnect paths are exemplarily depicted, but the packaging substrate 10 may include thousands or tens of thousands of such device-to-device electrical interconnect paths that are typically electrically isolated from each other, if no short exists between two electrical interconnect paths.

[0083] According to embodiments described herein, the packaging substrate 10 is placed on a stage 105 in the vacuum chamber 110. The stage can be movable,particularly in the z-direction (i.e. in a direction perpendicular to the stage surface) and / or in the x- and y-directions (i.e. in the plane of the stage surface). The stage 105 is provided within the vacuum chamber and is configured to support the packaging substrate, being e.g. one of a panel level packaging substrate and an advanced packaging substrate. An electron beam 111 is directed on the first surface contact point 21. The electron beam can be scanned to be directed to the second surface contact point 22. Signal electrons 113 emitted from the second surface contact point 22 are detected for testing the first device-to-device electrical interconnect path 20. The signal electrons may be secondary electrons and / or backscattered electrons. For example, it can be determined whether the first device- to-device electrical interconnect path 20 has an “open”-defect.

[0084] Alternatively or additionally, the electron beam 111 is directed on a further surface contact point 27 that is not an end point of the first device-to-device electrical interconnect path 20, i.e. that belongs to a second device-to-device electrical interconnect path 23 that may extend through the packaging substrate, adjacent to the first device-to-device electrical interconnect path 20. Signal electrons emitted from the further surface contact point 27 are detected for testing the first device-to- device electrical interconnect path 20. The signal electrons may be secondary electrons and / or backscattered electrons. For example, it can be determined whether the first device-to-device electrical interconnect path 20 has a “short” defect.

[0085] In particular, by detecting the signal electrons 113 emitted upon impingement of the electron beam 111 on the packaging substrate (particularly, by determining the energy of the signal electrons 113 that depends on the electric potential of the second surface contact point 22 or of the further surface contact point 27), it can be determined in a “voltage contrast measurement”, if the first device-to-device electrical interconnect path 20 is defective. Specifically, defective connections in the packaging substrate can be determined and classified, e.g. in open, short and / or leakage defects.

[0086] In some embodiments, the analysis unit 141 may be configured to determine, based on the detected signal electrons, whether an electrical interconnect path of apackaging substrate has a defect, such as a short, an open and / or a leakage. Optionally, the analysis unit 141 may be configured to classify a detected defect. In some embodiments, the analysis unit 141 may be configured to determine, based on the detected signal electrons from subsequent measurements, whether a short or a leakage exists between two or more electrical interconnect paths. In some implementations, the signal electrons 113 detected by the electron detector 140 may provide information about an electric potential of the substrate location from which the signal electrons 113 are emitted or reflected, and the analysis unit 141 may be configured to determine from said information if the device-to-device electrical interconnect path 20 is defective or not. The analysis unit 141 may be further configured to classify a determined defect. Specifically, testing may include determining, by the analysis unit 141 , if the first device-to-device electrical interconnect path 20 has any of a short, an open, and / or a leakage. An “open” is understood as an open electrical interconnect path that does not actually electrically connect the first surface contact point 21 and the second surface contact point 22. A “short” is understood as an electrical connection between two electrical interconnect paths that are actually to be electrically separated.

[0087] In some embodiments, which can be combined with other embodiments described herein, one or more electrical connections extending between surface contacts on different sides of the substrate are inspected. In yet further embodiments, a first plurality of electrical connections extending between surface contacts on a first side of the substrate, a second plurality of electrical connections extending between surface contacts on a second side of the substrate, and / or or third plurality of electrical connections extending between surface contacts on different sides of the substrate are inspected. For example, one or more electron beam columns may be arranged on both sides of the substrates (not shown in the figures), such that surface contacts on both sides of the substrate can be charged and / or discharged for inspecting and testing the respective electrical connections.

[0088] The testing method described herein is suitable for testing packaging substrates for multi-device in-package integration, particularly for testing PLP substrates or AP substrates, and uses an electron beam both for charging e.g. thedevice-to-device electrical interconnect path 20 and for reading the charged circuitry voltage, particularly by probing the second surface contact point and / or further surface contact points. In other words, both the “electrical driving” and the “probing” is done with an electron beam, such that defects can be reliably and quickly found. Testing by electron beam charging and electron beam probing (e.g. with an electron beam test (EBT) column or an electron beam review (EBR) column) is independent of topography, fast, and flexible with regard to contact point positions, size and geometry, whereas the topography of the packaging substrate may be a problem for other test methods like capacitive or electric field detectors.

[0089] A packing substrate, such as a PLP substrate, may include a plurality of device-to-device connections, e.g. 5.000 or more, 10.000 or more, 20.000 or more, or even 50.000 or more. The connections may include Through Silicon Vias (TSVs), e.g. provided in a silicon interposer with other conductor lines extending through the packaging substrate, and / or may include multi-die interconnect bridges that may be embedded in the packaging substrate. The packaging substrate may be a multilayer substrate including electrical interconnections in a plurality of layers arranged on top of each other, e.g. in a layer stack.

[0090] In some embodiments, the packaging substrate 10 includes a plurality of device-to-device electrical interconnect paths extending between respective first and second surface contact points, and optional further contact points. The method may also include testing the plurality of device-to-device electrical interconnect paths sequentially or in parallel. “Sequential testing” as used herein, refers to the subsequent testing of a plurality of device-to-device electrical interconnect paths of the packaging substrate. For example, 5.000 or more device-to-device electrical interconnect paths are tested one after the other. “Parallel testing” as used herein, may refer to the synchronous testing of two or more device-to-device electrical interconnect paths. “Parallel testing” as used herein, may also refer to the testing of several device-to-device electrical interconnect paths by scanning the electron beam for charging within one field of view over several first surface contact points while scanning the electron beam for probing in one field of view over several corresponding second surface contact points. Particularly for sequential testing,embodiments of a trailing or continuous discharging of device-to-device electrical interconnect paths, i.e. networks, can result in a more equal distribution of charging times between the networks.

[0091] While conventional PCBs typically include comparatively large flat metal pads that form surface contact points for testing, a packaging substrate that is tested according to embodiments described herein may include huge numbers of small, convexly shaped bumps to be tested, which makes testing more challenging. In particular, the first surface contact point 21 and the second surface contact point 22 may have a maximum dimension of 25 pm or less, particularly 10 pm or less, respectively. For example, the first and second surface contact points may be essentially round, particularly semi-spherically shaped, with a diameter of 25 pm or less, particularly 10 pm or less. According to some embodiments, which can be combined with other embodiments described herein, a surface contact point can have a three-dimensional topography, particularly a substantially semi-spherical shape.

[0092] In contrast to mechanical testers, electron beams can be accurately directed on such small surface areas because electron beams can be focused down to small probe diameters and can be accurately directed on predetermined points of the substrate, e.g. with scan deflectors that have, for example, an accuracy in a sub- pm-range. While other testers may slip or slide from surface contact points with a convex geometry, electron beams can be accurately focused onto arbitrary geometries, such that the testing methods described herein are geometryindependent and topography-independent.

[0093] The first plurality of electrodes and / or the second plurality of electrodes can be utilized for guiding of signal electrons during detection of the signal electrons and can be utilized for generating the electric field for charge control. According to additional or alternative modifications, the electric field may be generated by a further electrode, for example, electrode 154, or by a combination of a further electrode and the first plurality of electrodes and / or the second plurality of electrodes.

[0094] In some embodiments, which can be combined with other embodiments described herein, the electron detector 140 includes an Everhard-Thornley detector. An energy filter 142 for the signal electrons 113 may be arranged, e.g. in front of the electron detector 140, particularly in front of the Everhard-Thornley detector, as schematically depicted in FIG. 1 . The energy filter may include a grid electrode configured to be set on a predetermined potential. The energy filter 142 may allow the suppression of low-energy signal electrons. The energy filter 142 may suppress signal electrons that are irrelevant for the voltage contrast measurements to be conducted. In some implementations, the energy filter 142 may suppress signal electrons emitted from uncharged surface areas and may only let through signal electrons emitted from a charged surface contact point. Accordingly, the signal current detected by the electron detector may depend on the energy of the signal electrons, which indicates if a probed surface contact point is defective or not. Accordingly, avoiding or reducing charging of undesired substrate areas by vector scanning and beam blanking improves the S / N-ratio for the defect detection.

[0095] FIG. 1 exemplarily illustrates the stage 105 being connected to ground. The stage may be connected directly to ground, may be connected to ground via a DC power supply as exemplarily shown in FIG. 1 , or may be connected to ground via an AC power supply. According to some embodiments, which can be combined with other embodiments described herein, the stage can include a conductive stage surface connected directly or indirectly to ground for providing a reference potential. For example, a power supply 106 can be provided to indirectly connect the stage to ground.

[0096] According to some embodiments, which can be combined with other embodiments described herein, the stage includes a conductive stage surface connected directly or indirectly to ground for providing a reference potential. According to yet further additional or alternative modifications, the packaging substrate can be partially connected to ground, for example, by the stage. For example, some circuitries can be connected to GND while some circuits are not connected to ground. According to yet further modifications, which can be combined with other embodiments described herein, the packaging substrate can becapacitively connected to ground, e.g. by the stage. For some embodiments, there is no ohmic connection.

[0097] The defined potential of the stage, particularly a conductive stage, provides electric field lines, particularly at non-conductive portions of the stage surface and the packaging substrate. The defined potential can be utilized to influence the electron beam of the electron beam column.

[0098] FIG. 1 shows a controller 180. According to some embodiments, which can be combined with other embodiments described herein, the controller can be connected to one or more of the components of the apparatus 100 for contactless testing of a packaging substrate and for charge control. As exemplarily shown in FIG. 1 , the controller can be connected to the power supply 130, the scan controller 123, the analysis unit 141 , and the stage 105. The controller may also be connected to the electron detector 140.

[0099] The controller 180 comprises a central processing unit (CPU), a memory and, for example, support circuits. To facilitate control of the apparatus for testing packaging substrates, 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, 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 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 vector scanning, first calibration, second calibration and the utilization of the calibrations during testing, the stage positioning during the testing operation. Although themethod 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, embodiments of the invention 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.

[0100] The controller may execute or perform a method of testing a packaging substrate with an electron beam column according to embodiments of the present disclosure. According to an embodiment, an apparatus for testing of packaging substrates with any of the methods described herein is provided. The apparatus may include the controller 180. The controller includes a processor and a memory, storing instructions that, when executed by the processor, cause the apparatus to perform a method according to embodiments of the present disclosure.

[0101] FIGS. 4A and 4B show enlarged sectional views of packaging substrates during a testing method described herein. The packaging substrate 10 may be an AP substrate or a PLP substrate for the manufacture of a multi-die integrated package and includes a first die connection interface for attaching a first die 301 and a second die connection interface for attaching a second die 302. A plurality of device-to-device electrical interconnect paths (four of which are exemplarily shown in FIG. 4A and FIG. 4B) extend between a respective first surface contact point of the first die connection interface and a respective second surface contact point of the second die interconnection interface. The surface contact points may be formed as, or include, solder bumps that have a three-dimensional geometry, e.g. an essentially semi-spherical shape.

[0102] In FIG. 4A, a first device-to-device electrical interconnect path 20 extending between a first surface contact point 21 and a second surface contact point 22 is tested by directing a charge of an electron beam 111 on the first surface contact point 21 and directing the electron beam 112 on the second surface contact point 22. Since the first surface contact point 21 is electrically connected to the second surface contact point 22 by the first device-to-device electrical interconnect path 20, the second surface contact point 22 should be at the same electrical potential as thefirst surface contact point 21 after charging of the first surface contact point 21. Signal electrons 113 emitted from the second surface contact point 22 are detected that carry information about the electrical potential of the second surface contact point 22, which should be equal to the electrical potential of the first surface contact point 21. If an electrical potential of the second surface contact point 22, different from the electrical potential of the first surface contact point 21 is determined, a defect is detected. The detected voltage contrast can be used for characterizing the defect. Further, the detected voltage contrasts of subsequent measurements of neighboring electrical interconnect paths can be compared, in order to find out about shorts or leakages between different electrical interconnect path.

[0103] After the test of the first device-to-device electrical interconnect path 20, the electron beam 111 can be directed on two surface contact points of a second device- to-device electrical interconnect path 23, e.g. by scanning (vector scanning) the electron beams with respective scan deflectors to other positions, and / or by moving the stage on which the packaging substrate is supported. A plurality of device-to- device electrical interconnect paths can be subsequently tested with the charging electron beam and the probing electron beam. Accordingly, a plurality of test points can be tested sequentially and / or in parallel.

[0104] In FIG. 4B, an open 151 exists in the first device-to-device electrical interconnect path 20. The open 151 is determined because the second surface contact point 22 is not charged after or during the charging of the first surface contact point 21 by the charging electron beam 111.

[0105] In FIG. 4B, a short 155 exists between the second device-to-device electrical interconnect path 23 and a third device-to-device electrical interconnect path 24. The short can be determined because the third device-to-device electrical interconnect path 24 is charged together with the second device-to-device electrical interconnect path 23, which can be detected by the probing electron beam that is directed on the further surface contact point 27 of the third device-to-device electrical interconnect path 24 after or during the charging of the second device-to- device electrical interconnect path 23.

[0106] For an evaluation and defect classification, the signals of measurements of neighboring interconnect paths and / or previously collected data can be compared, such that opens, shorts, and leakages in the packaging substrate can be identified.

[0107] FIG. 5 is a schematic top view of a packaging substrate 10 as described herein under test. The packaging substrate has a top surface with a plurality of surface contact points arranged in a 2-dimensional pattern. The packaging substrate 10 includes a first die connection interface 31 for attaching a first die, particularly by flip-chip mounting, a second die connection interface 32 for attaching a second die, particularly by flip-chip mounting, and optionally, further die connection interfaces that may be arranged pairwise next to each other. The first die connection interface 31 may include a plurality of first surface contact points, e.g. formed as solder bumps, and the second die connection interface 32 may include a plurality of second surface contact points, e.g. formed as solder bumps.

[0108] In some embodiments, each first surface contact point of the first die connection interface 31 is connected to one respective second surface contact point of the second die connection interface 32 by a device-to-device electrical interconnect path. For the sake of clarity, only the device-to-device electrical interconnect paths connecting the first and second die connection interfaces are depicted. According to some embodiments, which can be combined with other embodiments described herein, the first surface contact point may be connected to one second surface contact point. Alternatively, the first surface contact point may be connected to two or more second surface contact points. The two or more second surface contact points can be probed with the electron beam, for example, after charge has been applied to the first surface contact point.

[0109] According to the testing method described herein, the charging electron beam 111 is directed, particularly focused, on a first surface contact point of the first die connection interface 31 , and the charging electron beam 111 is directed, particularly focused, on the associated second surface contact point of the second die connection interface 32. Signal electrons emitted from the second surface contact point are detected for testing whether an “open” defect exists in the electrical interconnect path that connects the first and second surface contact points.Thereafter, the other surface contact points of the first and second die connection interfaces may be tested, particularly pairwise.

[0110] Alternatively or additionally, it can be tested in parallel or subsequently, whether the charging of one device-to-device electrical interconnect path leads to the charging of a surface contact point of another device-to-device electrical interconnect path, such that a “short” defect can be determined.

[0111] The packaging substrate 10 depicted in FIG. 6A has surface contact points on both main surfaces of the packaging substrate. For example, a first plurality of device-to-device electrical interconnect paths may extend between first and second surface contact points exposed on an upper substrate surface, and a second plurality of device-to-device electrical interconnect paths may extend between first and second surface contact points exposed on a lower substrate surface. The dotted boxes exemplarily show chips or the like, mounted on top of the packaging substrate after the substrate test has been completed.

[0112] The packaging substrate 10 depicted in FIG. 6B, has at least one device-to- device electrical interconnect path that extends between at least three surface contact points 25, i.e. a first surface contact point, a second surface contact point, and at least a third surface contact point.

[0113] The packaging substrate 10 depicted in FIG. 6C has at least one device-to- device electrical interconnect path that extends between at least three surface contact points 25 that are exposed on different main surfaces of the substrate in a complex connection network. Such a device-to-device electrical interconnect path may be configured for connecting three or more dies with each other through the packaging substrate.

[0114] The packaging substrate 10 depicted in FIG. 6D has at least one interconnect bridge 29 embedded in the packaging substrate 10. At least one device-to-device electrical interconnect path extends through the at least one interconnect bridge 29. In particular, a plurality of device-to-device electrical interconnect paths extending between a first die connection interface and a second die connection interface ofthe packaging substrate extend through the interconnect bridge. The interconnect bridge may be embedded in the packaging substrate during the manufacture of the packaging substrate. The interconnect bridge may be a bridge chip embedded in the packaging substrate for increasing the connection speed between multiple dies.

[0115] According to some embodiments, which can be combined with other embodiments described herein, test methods and / or apparatuses according to the present disclosure may be utilized during and / or after manufacturing of a packaging substrate. For example, a test may be applied on a packaging substrate that does not yet include all layers or structures. For example, a test may be conducted after a redistribution layer (RDL) has been manufactured and / or after a via layer has been manufactured. An RDL test and / or a via test can be provided. Yet further, a test may be provided on the finished packaging substrate.

[0116] A test may be provided by charging (writing on) one or more portions, e.g. surface contact points, and by detecting the charge by means of signal electrons, i.e. reading a charge on the packaging substrate. The number of electrons emitted from the surface of the packaging substrate per irradiated electron, i.e. the total electron yield is energy dependent. For a total electron yield of 1 , the same number of electrons reach the surface of the packaging substrate as compared to the number of signal electrons being emitted from or scattered at the surface of the packaging substrate. There are two neutral energy values, a first neutral energy value and a second neutral energy value, for which the total electron yield equals 1 , i.e. there is no charging. According to some embodiments, which can be combined with other embodiments described herein, the surface of the packaging substrate can be read, i.e. signal electrons can be detected, with an electron beam having one of the neutral energy values.

[0117] According to some embodiments, which can be combined with other embodiments described herein, directing an electron beam with the first landing energy on a portion of a packaging substrate can be a charging operation. The charging operation “writes” a charge to an electrical interconnect path or a network of electrical interconnect paths. Further, directing an electron beam with a second landing energy on a portion of the packaging substrate can be an operation fordetecting signal electrons. The electron beam at the second landing energy may “read” a charge of an electrical interconnect path or a network of electrical interconnect paths.

[0118] According to some embodiments, which can be combined with other embodiments described herein, charging of portions of the packaging substrate is reduced or avoided during detection of signal electrons, i.e. reading of a charge. Particularly, influencing of a charge of electrical interconnect path or network of electrical interconnect paths is avoided or kept to a minimum while detecting signal electrons, for example, detecting the charge previously provided.

[0119] For example, a network of electrical interconnect paths may include 5 surface contact points (or any number lager than 2). A charge can be applied, i.e. “written”, to a first surface contact point. The charge applied to the network of electrical interconnect paths can be “read” at a second surface contact point. It is beneficial not to change the charge of the network of electrical interconnect paths with the 5 surface contact points while “reading” the charge on the second to fifth surface contact point. Accordingly, charge generation can be reduced or avoided during detecting signal electrons by utilizing a neutral energy value for the landing energy.

[0120] The neutral energy values are material dependent. The material of the packaging substrate or a material of the surface of the packaging substrate is known and the landing energies can be adapted to the packaging substrate material for methods of testing the packaging substrate. The first neutral energy value can be a few hundred eV (200 to 500 eV). The second neutral energy value can be between 1.5 keV and 2.5 keV for typical packaging substrates or typical surface contact points on a packaging substrate. According to some embodiments, which can be combined with other embodiments described herein, the landing energy for test methods can be chosen to be above the second neutral energy value for charging, to be between the first neutral energy value and the second neutral energy value for charging, or to be below the first neutral energy value. The landing energy can be adapted depending on the test strategy, the material of the packaging substrate, and / or the material of the surface contact points.

[0121] For landing energies below the first neutral energy value, negative charging occurs, i.e. the total electron yield is smaller than 1. For landing energies between the first neutral energy value and the second neutral energy value, positive charging occurs, i.e. the total electron yield is larger than 1 . The total electron yield being larger than 1 relates to the fact that more electrons leave the surface as compared to the number of electrons impinging on the surface. Thus, the packaging substrate or structures charge positively. For landing energies above the second neutral energy value, negative charging occurs, i.e. the total electron yield is smaller than 1 . The total electron yield being smaller than 1 relates to the fact that less electrons leave the surface as compared to the number of electrons impinging on the surface. The packaging substrates or structures charge negatively.

[0122] According to embodiments of the present disclosure, test structures, for example, regions of a packaging substrate and / or surface contact points can be charged positive or negative by the electron beam impact. Depending on the primary energy level, i.e. the landing energy, in relation to the secondary electron yield, the total electron yield can be controlled. The test point potential can be determined. A voltage contrast principle can be utilized for defect detection. Further, sample parameter monitoring (such as capacitance resistance) can be provided. According to some embodiments, which can be combined with other embodiments described herein, the landing energy can be changed to be higher or lower than the second neutral energy value. The landing energy of the electron beam is set to a predetermined landing energy and positioned on a portion of the packaging substrate, for example, the surface contact point or test point on the packaging substrate. The electron beam remains on the portion of the packaging substrate for a defined time to charge the portion of the packaging substrate positive or negative with respect to the environment of the portion of the packaging substrate. For example, the environment of a surface contact point under test can be one or more neighboring surface contact points.

[0123] A 'vector scan’ method according to embodiments of the present disclosure improves the S / N-ratio and signal difference between good and defect contact pads or contact electrodes. The electron beam is turned off while the deflection systempositions on the contact electrode that is next to be tested on the panel, or wafer, or any other substrate. The electron beam is then pulsed on for a defined time and turned off again. The electron beam is only hitting the contact electrodes and does not expose the dielectric material in-between.

[0124] Embodiments of the present disclosure provide one or more of the further following advantages. A contact free electrical test of packaging substrates as disclosed herein can be provided, wherein electrical charge can be controlled for electrical defect detection. In light of the flexibility of the electron beam, increased testing speed can be provided. A test including 100% of the electrical interconnection path is possible during volume production. Further, the flexibility of the electron beam allows for testing and flexible setup for different AP / PLP substrate layouts. The test methods and apparatuses disclosed herein are independent from test feature dimensions and further allow for being scalable to smaller dimensions, particularly if technical development moves towards smaller structure sizes. The testing of the packaging substrates is damage free.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

CLAIMSWhat is claimed is:1 . A method of testing a packaging substrate with at least one charged particle beam column, the method comprising: placing the packaging substrate on a stage in a vacuum chamber; blanking a charged particle beam of the at least one charged particle beam column at a first position on the packing substrate; vector scanning the charged particle beam from the first position on the packaging substrate to a second position on the packaging substrate while the charged particle beam is blanked, the vector scanning being based upon a first calibration of one or more charged particle beam properties of the charged particle beam and being based upon a second calibration of a beam position of the charged particle beam; un-blanking the charged particle beam onto the second position; blanking the charged particle beam at the second position; vector scanning the charged particle beam from the second position to a third position on the packaging substrate while the charged particle beam is blanked, the vector scanning being based upon the first calibration and the second calibration; and testing one or more networks on the packaging substrate in the vacuum chamber based upon signals received from at least the third position.

2. The method of claim 1 , wherein each of the first position, the second position and the third position are portions of the one or more networks.

3. The method of any of claims 1 to 2, wherein a ratio between dielectric areas of the packaging substrate and conductive areas of the packing substrate is equal to or larger than 1 :3.

4. The method of any of claims 1 to 3, wherein a beam diameter on the packing substrate is 1 pm or above.

5. The method of claim 4, wherein a beam current of the charged particle beam is 200 nA or above.

6. The method of any of claims 1 to 5, wherein basing the vector scanning on the first calibration comprises adjusting at least one of a stigmator and a lens assembly and wherein basing the vector scanning on the second calibration comprises adjusting at least one of a first deflection stage and a second deflection stage.

7. The method of claim 6, wherein basing the vector scanning on at least one of the first calibration and the second calibration comprises reading parameters from one or more look up tables.

8. The method of any of claims 1 to 7, wherein vector scanning results in positioning of the charged particle beam on an arbitrary sequence of positions on the packaging substrate.

9. The method of any of claims 1 to 8, further comprising:pulsing the charged particle beam for a period of time while directed onto the second position.

10. The method of any of claims 1 to 9, wherein the charged particle beam is vector scanned to a plurality of positions extending over a field of view of at least 70 mm.

11. A method of operating an apparatus for testing of a packaging substrate, comprising: placing a substrate in a stage of the apparatus; guiding a charged particle beam of a charged particle beam column sequentially onto a plurality of first positions, the plurality of first positions extending over a field of view of 70 mm or above; for each of the plurality of first positions, adjusting at least one of a lens assembly to a calibrated first focus value and a stigmator to a calibrated first astigmation correction value; guiding the charged particle beam sequentially onto a plurality of second positions, the plurality of second positions extending over a field of view of 70 mm or above; for each of the plurality of second positions, setting least one of the lens assembly to at a calibrated second focus value and the stigmator to a calibrated second astigmation correction value, and imaging an area at each of the second positions; and based on the imaged areas resulting from the plurality of second position, calibrating one or more deflector stages to determine calibrated position values.

12. The method of claim 11 , wherein the calibrated second focus value is based on one or more calibrated first focus values of one or more first positions at or adjacent to a corresponding second position of the plurality of second positions.

13. The method of any of claims 11 to 12, wherein the calibrated second astigmation correction value is based on one or more calibrated first astigmation correction values of the one or more first positions at or adjacent to the corresponding second position of the plurality of second positions.

14. The method of any of claims 11 to 13, further comprising: a method of testing a packing substrate according to any of claims 1 to 10.

15. The method of claims 14, wherein a first calibration for vector scanning includes the calibrated first focus value and the calibrated first astigmation correction value and a second calibration for vector scanning includes the calibrated position values.

16. An apparatus for testing of a packaging substrate, comprising: a vacuum chamber; a stage within the vacuum chamber, the stage being configured to support the packaging substrate; a charged particle beam column configured to generate a charged particle beam, the charged particle beam column comprising:a lens assembly with a first objective lens configured to focus the charged particle beam on the packaging substrate and a second objective lens to focus the charged particle beam on the packaging substrate; a first scanner stage configured to scan the charged particle beam to different positions on the packaging substrate and a second scanner stage configured to scan the charged particle beam to different positions on the packaging substrate; and an electron detector for detecting signal electrons emitted upon impingement of the charged particle beam on the packaging substrate; a beam blanker configured to blank or un-blank the charged particle beam; and a controller having 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 15.

17. The apparatus of claim 16, wherein the first objective lens is configured for a larger focusing strength than the second objective lens and wherein the second objective lens is configured for a smaller hysteresis and / or to be faster as compared to the first objective lens.

18. The apparatus of claim 17, wherein the first scanner stage is a magnetic scanner stage and the second scanner stage is an electrostatic scanner stage.

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