Methods and apparatus for an electron beam testing electrical connections of a substrate

Abstract

A method for testing electrical connections of a substrate is described, wherein the substrate has a first surface contact (21) and a first electrical connection (20) extending from the first surface contact (21). The method comprises: (a) discharging the first surface contact (21) by focusing and deflecting a first electron beam (111) having a first electron energy onto the first surface contact (21); (b) charging the first surface contact (21) by focusing and deflecting a second electron beam (112) having a second electron energy different from the first electron energy onto the first surface contact (21); and (c) testing the first electrical connection (20) by detecting signal electrons emitted from the substrate. Additionally, apparatus for testing electrical connections of a substrate using two electron beams of different electron energies according to the methods described herein is described.

Description

Technology Field

[0001] The present disclosure relates to methods and apparatuses for testing electrical connections extending through a substrate. More specifically, the embodiments described herein relate to non-contact testing of electrical interconnections within a substrate using an electron beam to identify and characterize defects such as short circuits, open circuits, and / or leakage, particularly through voltage contrast measurements. Background Technology

[0002] In many applications, it is necessary to inspect substrates to monitor their quality. For example, glass substrates with deposited coating material layers are manufactured for the display market. Since defects can occur during substrate processing, for instance, during coating, inspecting the substrates to review these defects and monitor the quality of the displays can be beneficial.

[0003] Additionally, semiconductor substrates and printed circuit boards for the fabrication of complex microelectronic or micromechanical components are typically tested before, during, and / or after fabrication to determine defects, such as short circuits or open circuits within metal paths and interconnects provided on the substrate. For example, substrates for the fabrication of complex microelectronic devices may include multiple interconnect paths intended to connect semiconductor chips to be mounted on the substrate. The devices to be tested may further include, for example, thin-film transistors (TFTs), interconnect networks, transistors, pixels of a display, and other components.

[0004] Various methods for testing these components are known. For example, to determine whether a component is defective, the contact pads of the component to be tested can be mechanically brought into contact with a contact probe. However, as components and contact pads are becoming increasingly smaller due to the ongoing miniaturization of components, bringing the contact pads into contact with a contact probe can be difficult, and there may even be a risk of damaging the device under test during the test.

[0005] In addition, it is possible to probe the components to be tested non-contactually using, for example, an electron beam from an electron beam testing column (EBT column). Electron beam testing can be used to monitor defects in the electrical connections of a substrate. In EBT testing, specific voltages are applied to the components to be tested, and a primary electron beam is used to generate signal electrons emitted from the substrate, allowing conclusions regarding the integrity of the components. However, conventional e-beam testing methods may not be suitable for testing advanced microelectronic components, considering the increasing number of increasingly smaller components to be tested per substrate in short time intervals while maintaining high yield.

[0006] Therefore, it would be beneficial to provide test methods and test devices suitable for reliably and rapidly testing complex microelectronic devices.

[0007] In light of the foregoing, methods and apparatus for testing electrical connections of a substrate are provided according to the independent claims. Further embodiments, advantages, and beneficial features are apparent from the dependent claims, the description, and the accompanying drawings.

[0008] According to one embodiment, a method for testing electrical connections of a substrate is provided, wherein the substrate has a first surface contact and a first electrical connection extending from the first surface contact. The method comprises: (a) discharging the first surface contact by focusing and deflecting a first electron beam having a first electron energy onto the first surface contact; (b) charging the first surface contact by focusing and deflecting a second electron beam having a second electron energy different from the first electron energy onto the first surface contact; and (c) testing the first electrical connection by detecting signal electrons emitted from the substrate.

[0009] In some embodiments, the substrate is an advanced packaging substrate (AP substrate) or a panel-level packaging substrate (PLP substrate).

[0010] In some embodiments, discharge (a) is performed before charging (b). In some embodiments, discharge (a) is additionally or alternatively performed after inspection (c). In some embodiments, discharge (a) is performed before charging (b) and after inspection (c). That is, discharge (a) of the first surface contact using the first electron beam can be performed before charging (b) of the first surface contact using the second electron beam, so that the substantially uncharged first surface contact having a defined electrical potential can be charged in the charging phase (b). Alternatively or additionally, discharge (a) of the first surface contact using the first electron beam can be performed after charging and inspection. Thus, after inspection, the first surface contact can be returned to a defined electrical potential by discharging (a) the first surface contact using the first electron beam.

[0011] Charging (b) and inspection (c) may be performed simultaneously, for example, by detecting a secondary electron signal emitted by the substrate as a function of time during charging (b). Alternatively, inspection (c) may be performed after charging (b), for example, by probing the first surface contact with a second electron beam or a first electron beam after charging (c) and / or by probing one or more additional surface contacts.

[0012] According to another embodiment, an apparatus configured to test the electrical connections of a substrate according to any of the methods described herein is provided.

[0013] An apparatus for testing electrical connections of a substrate as described herein may include: a vacuum chamber housing a stage for placing the substrate; a first electron source configured to generate a first electron beam having a first electron energy; a second electron source configured to generate a second electron beam having a second electron energy different from the first electron energy; and a controller, wherein in a discharge phase (a), the first electron beam is focused and deflected toward the first surface contact to discharge the first surface contact; in a charge phase (b), the second electron beam is focused and deflected toward the first surface contact to charge the first surface contact; and the apparatus is configured to control the apparatus so that a first electrical connection connected to the first surface contact is examined by detecting signal electrons emitted from the substrate during or after the charge phase (b) with an electron detector.

[0014] According to a further embodiment, an apparatus for testing electrical connections of a substrate is provided, the apparatus comprises a vacuum chamber housing a stage for placing the substrate, a first electron source configured to generate a first electron beam having a first electron energy, a second electron source configured to generate a second electron beam having a second electron energy different from the first electron energy, a focusing lens array configured to focus the first electron beam on the substrate in a discharge phase and focus the second electron beam on the substrate in a charge phase, a beam deflector array configured to deflect the first electron beam on the first surface contact to discharge the first surface contact of the substrate in a discharge phase and to deflect the second electron beam on the first surface contact to charge the first surface contact in a charge phase, an electron detector for detecting signal electrons emitted from the substrate, and an analysis unit for examining a first electrical connection connected to the first surface contact based on the signal electrons, specifically through voltage contrast measurements.

[0015] The embodiments also relate to devices for carrying out the disclosed methods and include parts of the device for carrying out each described method embodiment. These method embodiments may be carried out by hardware components, a computer programmed by suitable software, any combination of the two, or any other method. Furthermore, embodiments according to the present disclosure also relate to methods for operating the described device and methods for manufacturing the devices and devices described herein. Methods for operating the described device include method embodiments for carrying out all functions of the device. Brief explanation of the drawing

[0016] In a manner that allows the features of the present disclosure mentioned above to be understood in detail, a more specific description of the present disclosure, briefly summarized above, can be obtained by referring to the embodiments. The accompanying drawings relate to embodiments of the present disclosure and are described below: FIG. 1 illustrates a schematic cross-sectional view of an apparatus for testing electrical connections of a substrate according to embodiments described in this specification. FIG. 2 illustrates a schematic cross-sectional view of an apparatus for testing electrical connections of a substrate according to embodiments described in this specification. FIGS. 3a-3d schematically illustrate a test method according to embodiments described herein. FIG. 4 illustrates a flowchart of a method for testing electrical connections of a substrate according to embodiments described in this specification. Specific details for implementing the invention

[0017] Various exemplary embodiments will be referenced in detail below, and one or more examples thereof are illustrated in the respective drawings. Each example is provided for illustrative purposes only and is not intended to be limiting. For example, features illustrated or described as part of one embodiment may be used in or together with other embodiments to create other embodiments. The present disclosure is intended to include such modifications and variations. In the following description of the drawings, the same reference numerals refer to the same components. Only differences between individual embodiments are described. The structures illustrated in the drawings are not necessarily depicted in actual proportions but provide a better understanding of the embodiments.

[0018] The complexity of packaging substrates has increased over the years with the aim of reducing the space requirements of semiconductor packages. Conventional semiconductor packages are manufactured from semiconductor wafers before being diced and packaged. Next, the semiconductor package can be mounted on a printed circuit board (PCB) along with other microelectronic components.

[0019] To reduce manufacturing costs, advanced packaging technologies such as 2.5D ICs, 3D ICs, and wafer-level packaging (WLP), e.g., fan-out WLP, have been proposed. In WLP technologies, the integrated circuit is packaged before dicing while remaining part of the wafer. Consequently, the resulting package has nearly the same size as the wafer.

[0020] "2.5D integrated circuits" (2.5D ICs) and "3D integrated circuits" (3D ICs) combine multiple dies into a single integrated package. Here, two or more unpackaged dies are placed on a packaging substrate, for example, a silicon interposer. In 2.5D ICs, the dies are placed side-by-side on the packaging substrate, 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 cost and size compared to conventional 2D circuit board assemblies. Advanced Packaging (AP) substrates provide device-to-device electrical interconnection paths on or inside a wafer, such as a silicon wafer. For example, the AP substrate may include Through Silicon Vias (TSVs) provided, for example, within a silicon interposer, or other conductor lines extending through the AP substrate. Panel-level packaging (PLP) substrates are typically provided from composite materials, for example, materials of printed circuit boards (PCBs), or other composite materials, such as ceramic and glass materials.

[0021] A packaging substrate typically includes a plurality of device-to-device electrical interconnection paths intended to provide electrical connections between dies to be disposed on the packaging substrate. The device-to-device electrical interconnection paths may extend vertically (perpendicular to the surface of the packaging substrate) and / or horizontally (parallel to the surface of the packaging substrate) through the body of the packaging substrate in a complex connection network, and endpoints (referred to herein as surface contacts) are exposed on the surface of the substrate.

[0022] To further reduce manufacturing costs, panel-level substrates are manufactured configured to integrate multiple devices (e.g., chips / dies that may be heterogeneous, e.g., have different sizes and configurations) into a single integrated package. The panel-level substrate typically provides multiple device-to-device electrical interconnection paths extending through the body of the packaging substrate, as well as chip sites on which multiple chips / dies are disposed on its surface, e.g., on one side or both sides. In particular, the size of the panel-level substrate is not limited to the size of the wafer. For example, the panel-level substrate may be rectangular or have other shapes. Specifically, the panel-level substrate may provide a surface area larger than that of a typical wafer, e.g., 1000 cm² or more. For example, the panel-level substrate may have a size of 30 cm x 30 cm or more, 60 cm x 30 cm or more, 60 cm x 60 cm or more, or larger.

[0023] Conventional test devices may not be adapted or suitable for testing advanced packaging substrates due to the geometry and density of surface contacts and / or the size of the packaging substrate, which may differ from the size of conventional dies or printed circuit boards. The present disclosure relates to methods and apparatuses for testing substrates having a plurality of densely arranged surface contacts and a plurality of electrical connections extending between each of two or more surface contacts. In particular, the methods and apparatuses described herein may be suitable for testing packaging substrates configured to incorporate a plurality of devices in a single integrated package and may include at least one device-to-device electrical interconnection path extending between a first surface contact and at least one second surface contact.

[0024] "Surface contacts" can be understood as endpoints of electrical interconnection paths (hereinafter also referred to as "electrical connections") exposed on the surface of a substrate, thereby allowing an electron beam to be directed toward the surface contacts to charge or probe them non-contactually. The surface contacts may be intended to electrically contact a chip / die to be placed on the surface of the substrate, for example, through soldering. For example, the surface contacts may be configured as solder bumps.

[0025] FIG. 1 is a schematic cross-sectional view illustrating an apparatus (100) for testing microelectronic connections, such as interconnection paths and / or vias within a substrate (10), according to embodiments described herein. The apparatus (100) may be a test chamber specifically configured for testing, or may include a vacuum chamber (101) which may be a vacuum chamber of a larger vacuum system, for example, a processing chamber of a substrate manufacturing or processing system. For example, the apparatus may be configured as an inline inspection device integrated into a substrate processing system.

[0026] As schematically depicted in FIG. 1, the substrate (10) comprises a first surface contact (21) and a first electrical connection (20) extending from the first surface contact (21) through the substrate to one or more second surface contacts (22) that may be provided, for example, on the same substrate surface as the first surface contact (21). The substrate (10) may comprise a plurality of surface contacts and a plurality of electrical connections extending from the plurality of surface contacts, for example, more than 1,000 electrical connections, particularly more than 10,000 electrical connections, or even more than 100,000 electrical connections. A plurality of electrical connections extending from the plurality of surface contacts may be tested according to the methods described herein.

[0027] In some embodiments that may be combined with other embodiments described herein, one or more electrical connections extending between surface contacts on different sides of a substrate are examined. In other embodiments, a first plurality of electrical connections extending between surface contacts on a first side of a substrate, a second plurality of electrical connections extending between surface contacts on a second side of a substrate, and / or a third plurality of electrical connections extending between surface contacts on different sides of a substrate are examined. For example, one or more electron beam columns may be arranged on both sides of the substrates (not shown in the drawings), thereby allowing the surface contacts on both sides of the substrates to be charged and / or discharged to examine and test their respective electrical connections.

[0028] Returning to FIG. 1, the device (100) includes a first electron source (121) configured to generate a first electron beam (111) having a first electron energy, and a second electron source (122) configured to generate a second electron beam (112) having a second electron energy different from the first electron energy, particularly higher than the first electron energy.

[0029] The device further comprises a controller (161), and the controller is configured to control the device (100) such that, in a discharge phase (a), a first electron beam (111) is focused and deflected toward the first surface contact (21) to discharge the first surface contact, and in a charge phase (b), a second electron beam (112) is focused and deflected toward the first surface contact (21) to charge the first surface contact, and by detecting signal electrons emitted from the substrate during or after the charge phase (b) with an electron detector (180), the first electrical connection (20) extended from the first surface contact (21) is inspected.

[0030] The discharge phase (a) and the charge phase (b) are performed sequentially using a first electron beam for discharge and a second electron beam for charging the first surface contact. Meanwhile, the charge phase (b) and the inspection (c) can also be performed simultaneously (i.e., by charging and inspecting simultaneously) by specifically detecting and analyzing the secondary electron signal emitted by the substrate as a function of time during the charge (b). It is also possible to perform the charge and inspection sequentially, that is, by first charging the first surface contact with the second electron beam and then probing the first surface contact and / or additional surface contacts with the first or second electron beam to inspect the first electrical connection.

[0031] In some embodiments that may be combined with other embodiments described herein, the first electron energy of the first electron beam (111) is lower than the second electron energy of the second electron beam (112). The “electron energy” of the electron beam relates to the (average) energy of the electrons of the electron beam propagating toward the substrate. In particular, the first electron energy of the first electron beam (111) may be 1 keV or more and 3 keV or less, particularly about 1.5 keV, and / or the second electron energy of the second electron beam (112) may be 5 keV or more and 15 keV or less, particularly about 10 keV.

[0032] In some embodiments, the first electron energy of the first electron beam (111) may be below the neutral charging point, and the second electron energy of the second electron beam (112) may be above the neutral charging point. As used herein, “neutral charging point” refers to the electron energy of an electron beam that does not change its charges when the electron beam strikes an essentially uncharged surface contact, because the amount of signal electrons emitted from the substrate upon impact essentially corresponds to the amount of electrons delivered to the surface contact by the electron beam. The neutral charging point may correspond to an electron energy of about 2 keV of the electron beam.

[0033] When a first electron beam (111) having electron energy below the neutral charge point (e.g., 1.5 keV) strikes a surface contact, the amount of signal electrons leaving the substrate is typically greater than the amount of electrons delivered to the substrate by the first electron beam (111), for example, because there is a high probability that the striking electrons will generate secondary electrons (SE) leaving the substrate. Accordingly, negative charges are removed from the surface contact, and the surface contact can be discharged along with the electrical connection extending therefrom. As used herein, "discharge" relates particularly to the removal of negative charges, i.e., electrons, accumulated on the surface contact.

[0034] When a second electron beam (112) having electron energy above the neutral charge point (e.g., 10 keV) strikes the surface contact, the amount of signal electrons leaving the substrate is typically less than the amount of electrons delivered to the substrate by the second electron beam (112), for example, because the probability of high-energy electrons leaving the substrate or generating secondary electrons leaving the substrate is reduced. Accordingly, negative charges are applied to the surface contact, and the surface contact is charged (negatively) with an electrical connection extending therefrom. As used herein, "charge" relates particularly to applying negative charges, i.e., electrons, to the surface contact to cause a predetermined electrical potential of the surface contact.

[0035] Since the first electron beam (111) and the second electron beam (112) have different electron energies, particularly below and above the neutral charging point, the first electron beam (111) can be used to remove electrons, i.e., to discharge the surface contact, and the second electron beam (112) can be used to apply electrons, i.e., to charge the surface contact to a predetermined potential.

[0036] The electrical connections of the substrate can be inspected, for example, by charging the electrical connections by aiming an electron beam at a first surface contact electrically connected to the electrical connection until the electrical connection is provided at a predetermined electrical potential through charging. After charging the electrical connection, if there are no defects in the electrical connection, one or more second surface contacts electrically connected to the first surface contact through the electrical connection are provided at the same electrical potential as the first surface contact. The electrical potential of the one or more second surface contacts can be probed, for example, by aiming an electron beam at one or more second surface contacts and measuring the electron energy, SE signal yield, and / or signal intensity of the emitted signal electrons. For example, if the probed surface contact is provided at a negative potential, i.e., charged, the number of emitted signal electrons will increase. These so-called voltage contrast measurements allow for the determination of defective electrical connections of the substrate by probing the surface contacts of the charged electrical connections.

[0037] However, because the density of surface contacts on substrates has increased over the past few years, it can be difficult to negatively charge specific surface contacts to a predetermined electrical potential using an electron beam. For example, previously existing charges on a surface contact (e.g., charges originally present in the sample and / or charges applied during previous measurements of neighboring surface contacts) can negatively affect measurement accuracy because the charging of a pre-charged surface contact over a predetermined period may not lead to the surface contact's predetermined electrical potential. Additionally, charges present on neighboring surface contacts can negatively affect measurement accuracy because they will deflect signal electrons, causing only a portion of them to reach the electron detector. Previously existing charges on neighboring surface contacts can also negatively affect the probing electron beam striking the surface contact, which can lead to positional inaccuracies and prevent the testing of small surface contacts.

[0038] To address the problems mentioned above, according to the embodiments described herein, a first electron beam (111) having a first electron energy is used to discharge the first surface contact (21) before and / or after testing using a second electron beam (112). Discharging the first surface contact (21) in the discharge phase, i.e., removing any negative charges that may be present in the first surface contact (21), can bring the first surface contact (21) to a defined state having a low electric potential or zero electric potential before and / or after testing. "Discharge" does not necessarily mean that the electric potential of the individual surface contact is made zero relative to the ground potential. Rather, the electric potential may be made to a defined (low) voltage value that allows the subsequent charging phase to be started from the defined electric potential.

[0039] In some embodiments, the discharge (a) of the surface contact using the first electron beam may be performed before the charging (b) of the surface contact using the second electron beam. This allows the charging phase (b) to be started from a defined electric potential, which improves measurement accuracy.

[0040] Alternatively or additionally, discharge (a) of the surface contact using the first electron beam can be performed after inspection (c). This allows the surface contact to be returned to a defined (low) electrical potential after charging and inspection, so that subsequent measurements of neighboring surface contacts are not negatively affected by charges that may remain on the surface contact after inspection.

[0041] In some embodiments that may be combined with other embodiments described herein, discharge (a) is performed at the first surface contact before charging (b), and discharge (a) is performed again at the first surface contact after testing (c). Measurement accuracy can be improved for testing the first electrical connection as well as for subsequent tests of adjacent electrical connections. That is, discharge (a), charging (b), and testing (c) may be performed in the following order: (a), (b)+(c), and again (a), said order used for testing each electrical connection among a plurality of electrical connections, and “(b)+(c)” indicates that (b) and (c) may be performed subsequently or simultaneously.

[0042] In some embodiments that may be combined with other embodiments described herein, the substrate comprises a plurality of surface contacts and a plurality of electrical connections extending from the plurality of surface contacts, e.g., 1,000 or more electrical connections to be tested or 10,000 or more electrical connections. Discharge (a), charge (b), test (c), and optionally re-discharge (a) may be performed for each of the plurality of surface contacts to test the plurality of electrical connections extending from the plurality of surface contacts.

[0043] For example, after testing the first electrical connection (20), the second electrical connection (24) extending from the third surface contact (23) of the substrate may be tested as follows: the third surface contact (23) is discharged by focusing and deflecting the first electron beam (111) onto the third surface contact (23), the third surface contact (23) is charged by focusing and deflecting the second electron beam (112) onto the third surface contact (23), and the second electrical connection (24) is tested by detecting signal electrons emitted from the substrate during and / or after charging. Discharging the third surface contact (23) by focusing and deflecting the first electron beam (111) may be performed before charging and / or after testing. Next, the method can proceed by similarly testing other electrical connections, particularly more than 1,000 electrical connections in succession, by deflecting and focusing first and second electron beams on each surface contact extending from a plurality of electrical connections.

[0044] According to the embodiments described herein, the first electron beam (111) and the second electron beam (112) are subsequently focused onto the first surface contact, in particular, using a focusing lens array (140). Specifically, the focusing lens array (140) may be configured to focus one of the first and second electron beams onto the substrate. For example, the spot diameter of the first electron beam (111) and / or the second electron beam (112) focused onto the substrate may be 10 μm or less, particularly 1 μm or less. Accordingly, unlike UV light sources or electron floodguns typically used for removing charge from a substrate in other applications, the first electron beam (111) is focused onto the substrate to specifically discharge a predetermined surface contact in a targeted manner. Targeted charge removal is made possible only from the region of interest, for example, only from the specific surface contact currently being tested. Repeatedly discharging large substrate areas with an unfocused beam, such as a flood gun, takes a considerable amount of time. The present disclosure enables targeted and rapid charge removal from specific surface contacts under test, thereby accelerating the test and improving measurement accuracy.

[0045] According to the embodiments described herein, the first electron beam (111) and the second electron beam (112) are deflected at the first surface contact, in particular, to the beam deflector array (130). For example, the beam deflector array (130) may be configured to deflect one of the first and second electron beams at a predetermined location on a substrate, for example, the first surface contact or another surface contact. The beam deflector array (130) may be an electrostatic beam deflector array and / or a magnetic beam deflector array configured to deflect the first electron beam (111) or the second electron beam (112) to a predetermined location on the substrate surface, wherein the substrate surface is provided in the xy plane. The beam deflector array (130) may allow beam deflection in two directions, namely the x direction and the y direction, thereby allowing the first and second electron beams to be deflected to any predetermined location within the xy plane where a plurality of surface contacts are distributed.

[0046] In some embodiments, the deflection area provided by the beam deflection array (130) may be at least 9 cm² for the first electron beam (111) and the second electron beam (112) on the substrate surface. In particular, the beam deflection array (130) may provide an overlapping deflection area of ​​at least 9 cm² for the first electron beam (111) and the second electron beam (112) on the substrate surface. That is, the first electron beam and the second electron beam may be subsequently deflected to the same locations on the substrate by the deflection array (130) in an overlapping deflection area of ​​at least 9 cm² without moving the stage. In some embodiments, the overlapping deflection area may be at least 16 cm², particularly at least 100 cm², or even at least 225 cm². For example, the beam deflector array (130) may provide an overlapping deflection area for the first electron beam (111) and the second electron beam (112), and the overlapping deflection area has dimensions D1 of at least 3 cm x 3 cm, specifically at least 4 cm x 4 cm, more specifically at least 10 cm x 10 cm, or even at least 15 cm x 15 cm in the xy plane of the substrate.

[0047] In particular, the beam deflector array (130) can enable deflection of a first electron beam to any location within a deflection area of ​​at least 5 cm x 5 cm on the substrate surface, and the deflector array (130) can enable deflection of a second electron beam to any location within the same deflection area of ​​at least 5 cm x 5 cm on the substrate surface, specifically, the same deflection area of ​​at least 10 cm x 10 cm. Since the deflection areas provided for the first and second electron beams may partially or completely overlap, the first and second electron beams can be deflected to the same surface contacts of the substrate without moving the substrate by controlling the beam deflector array (130) accordingly. A large portion of the substrate surface or even the entire substrate can be inspected by deflecting the first and second electron beams to their respective surface contacts that may be distributed across a substrate area of ​​at least 10 cm x 10 cm without moving the stage (105) (i.e., leaving the substrate stationary).

[0048] Deflecting the first electron beam (111) and / or the second electron beam (112) onto one or more surface contacts to be tested using a beam deflector array (130) is advantageous compared to using one or more fixed electron beams. In particular, moving the stage (105) for one or more fixed electron beams is time-consuming and less accurate compared to beam deflection. Additionally, the first electron beam can be rapidly deflected multiple times over the surface contacts for discharge, for example, before and after charging and testing, without requiring time-consuming back-and-forth stage movement. Furthermore, by utilizing the first electron beam (111) deflected at each surface contact for discharge and the second electron beam (112) subsequently deflected at each surface contact for charging and / or probing, multiple surface contacts can be tested quickly and conveniently in succession.

[0049] According to the embodiments described herein, a rapid and reliable method for accurately testing a plurality of electrical connections is provided. Specifically, in a discharge phase (a), a first electron beam (111) is deflected by a beam deflector array (130) so that the first electron beam (111) is focused onto a first surface contact. In a charge phase (b), a second electron beam (112) is deflected by a beam deflector array (130) so that the second electron beam (112) is focused onto the first surface contact for charging. To test the first electrical connection, signal electrons emitted from the substrate are detected by an electron detector (180) when probing a specific surface contact of the substrate with the second electron beam (112), particularly during or after the charge phase. Focusing and deflecting the electron beams onto different surface contacts increases the speed of testing and ensures that neighboring regions of the substrate are less affected by the electron beams, thereby increasing measurement accuracy. The discharge phases before and / or after charging and testing bring the respective surface contacts to a defined electrical potential before and after testing. A large number of densely arranged surface contacts and their respective electrical connections can be tested quickly and reliably.

[0050] In some embodiments, the inspection (c) includes performing voltage contrast measurements based on signal electrons detected when the second electron beam (112) strikes the substrate. In particular, the second electron beam (112) may be used for both charging the first surface contact and probing additional surface contacts that are to be electrically connected to or electrically disconnected from the first surface contact. Alternatively, the first electron beam (111) may be used for both discharging and probing the surface contacts charged by the second electron beam (112).

[0051] In particular, the inspection (c) may include probing any one or more of the following surface contacts with the second electron beam (112) after charging the first surface contact (21) with the second electron beam (112): the first surface contact (21), one or more second surface contacts (22) that are to be electrically connected to the first surface contact (21) through the first electrical connection (20), and one or more third surface contacts (23) that are to be electrically disconnected from the first surface contact (21).

[0052] The first surface contact (21) may be probed to determine the charge state of the first electrical connection (20) after or during charging. For example, an unexpectedly high electrical potential of the first surface contact (21) after charging (or already during charging) may be an indication of a defective (open) first electrical connection because the applied charges cannot flow into the substrate from the first surface contact (21) toward one or more second surface contacts (22).

[0053] One or more second surface contacts (22) that are to be electrically connected to the first surface contact (21) via the first electrical connection (20) may be probed to determine whether the first electrical connection (20) actually extends between the first surface contact (21) and one or more second surface contacts (22). If one or more second surface contacts (22) are not charged after the first surface contact (21) is charged, the first electrical connection is likely defective (open).

[0054] One or more third surface contacts (23) that must be electrically disconnected from the first surface contact (21) can be probed to determine whether the first electrical connection (20) is short-circuited to an adjacent electrical connection. Specifically, if one or more third surface contacts (23) are charged after the first surface contact (21) is charged, the first electrical connection is likely short-circuited to another electrical connection.

[0055] In some embodiments that may be combined with other embodiments described herein, the device (100) comprises a two-beam column (110) that provides a common electron beam path (115) for a first electron beam (111) and a second electron beam (112). In particular, in a discharge phase (a), the first electron beam (111) can be propagated along the common electron beam path (115) through the two-beam column (110), while the second electron beam is deselected, and in a charge phase (b), the second electron beam (112) can be propagated along the common electron beam path (115) through the two-beam column (110), while the first electron beam is deselected.

[0056] FIG. 1 shows a device (100) having a 2-beam column (110). The 2-beam column (110) may include a beam selector (150) for selecting one of a first electron beam (111) and a second electron beam (112) to propagate through the 2-beam column toward a substrate. For example, the beam selector (150) may include a beam blanker and / or beam dump configured to block the deselected one of the first and second electron beams and allow the selected one of the first and second electron beams to pass along a common electron beam path (115).

[0057] A plurality of beam optical components for affecting a selected of the first electron beam (111) and the second electron beam (112) may be provided along the common electron beam path (115). Specifically, a focusing lens array (140) and / or a beam deflector array (130) may be centered with respect to the common electron beam path (115) as schematically depicted in FIG. 1.

[0058] The beam deflector array (130) may be configured to deflect one of the first and second electron beams to a predetermined position on the substrate. In particular, the beam deflector array (130) may provide an overlapping deflection area of ​​at least 9 cm² on the substrate for the first electron beam (111) and the second electron beam (112).

[0059] A controller (161) may be configured to control a beam selector (150), a beam deflector array (130), and / or a focusing lens array (140) so that one of the first and second electron beams selected is focused and deflected onto a predetermined location on the substrate surface, e.g., a first surface contact or another surface contact. The controller (161) may be further configured to control the beam selector (150) to select a first electron beam (111) for discharge (a) and a second electron beam (112) for charge (b). The first electron beam (111) or the second electron beam (112) may be selected to probe one or more surface contacts to inspect their respective electrical connections.

[0060] Providing a 2-beam column (110) having a common electron beam path (115) for the first electron beam (111) and the second electron beam (112) can be advantageous because a large overlapping deflection area made possible by a single common beam deflection array can be provided, since the common electron beam path (115) centers the beam deflection array (130) for the two beams in that path (see FIG. 1). For example, a large deflection area having dimensions D1 of 3 cm or more in the x and / or y direction, particularly 5 cm or more, or even 10 cm or more can be provided. A large sub-area of ​​the substrate or the entire substrate can be inspected without time-consuming stage movement. In particular, the beam deflection array (130) can provide an overlapping deflection area of ​​at least 3 cm x 3 cm, particularly at least 5 cm x 5 cm on the substrate surface.

[0061] The beam deflector array (130) may be configured to electrostatically and / or electrically deflect a first electron beam for discharge and a second electron beam for charge on a predetermined surface contact.

[0062] In some embodiments that may be combined with other embodiments described herein, a first electron beam (111) is generated by a first electron source (121) having a first emission tip and a first extractor electrode, and / or a second electron beam (112) is generated by a second electron source (122) having a second emission tip and a second extractor electrode. The first and second electron sources may be, for example, thermal field emitters (TFE).

[0063] The electron energy of the first electron beam (111) can be appropriately set by applying a first potential to the first emission tip, and the electron energy of the second electron beam (112) can be appropriately set by applying a second potential to the second emission tip. The second potential can be set so that the second electron beam has an electron energy higher than that of the first electron beam, particularly a second electron energy of 5 keV or more and 15 keV or less.

[0064] In some embodiments that may be combined with other embodiments described herein, the device (100) includes an electron detector (180) for detecting signal electrons emitted from a substrate, particularly when a second electron beam (112) strikes the substrate. The signal electrons may include secondary electrons (SE) and / or backscattered electrons (BSE).

[0065] In some embodiments, the electron detector (180) includes an Everhard-Thornley detector. As schematically depicted in FIG. 1, the Everhard-Thornley detector may be positioned downstream of the focusing lens array (140) and downstream of the beam deflector array (130) in the direction of propagation of the first and second electron beams. This increases detection efficiency.

[0066] An energy filter for signal electrons (113) may be arranged in front of the electron detector (180), particularly in front of the Eberhard-Sonley detector. The energy filter may include a grid electrode configured to be set to a predetermined potential. The energy filter may allow for the suppression of low-energy signal electrons. The energy filter may be set for optimal voltage-to-detection. Thus, the signal current detected by the electron detector (180) may depend on the energy of the signal electrons, indicating whether the probed surface contact point is provided at a predetermined electric potential.

[0067] An analysis unit (181) may be provided to inspect a first electrical connection (20) connected to a first surface contact (21) based on signal electrons detected by an electronic detector (180). For example, for each of the multiple electrical connections, the analysis unit (181) may provide an output indicating the state of the multiple electrical connections, e.g., "defective" or "not defective." Optionally, the type of defect (e.g., "open" defect or "short" defect) may be determined by the analysis unit (181) based on the electronic signal detected during probing of a specific surface contact.

[0068] In some embodiments, one or more additional beam-optical components (171) for affecting the first electron beam and / or the second electron beam may be provided in the common electron beam path (115), such as a condenser lens array and / or an aberration corrector array such as a stigmator, a chromator and / or other aberration correctors.

[0069] In some embodiments, the substrate (10) is a packaging substrate configured to provide multi-device in-package interconnection, and the first electrical connection (20) is a device-to-device electrical interconnection path. In particular, the substrate (10) may be an advanced packaging (AP) substrate, a panel level packaging (PLP) substrate, a wafer level packaging (WLP) substrate, or a micro LED substrate.

[0070] FIG. 2 illustrates a schematic cross-sectional view of an apparatus (200) for testing electrical connections of a substrate (10) according to embodiments described herein. The apparatus (200) may be similar to the apparatus (100) shown in FIG. 1 and may include corresponding features so as to allow reference to the above description, which are not repeated herein. Differences will be described below.

[0071] The device (200) comprises a vacuum chamber (101) housing a stage (105) for placing a substrate (10) thereon, a first electron source (121) for generating a first electron beam (111) having a first electron energy, and a second electron source (122) for generating a second electron beam (112) having a second electron energy. The device (200) further comprises a focusing lens array (140) for focusing one selected of the first electron beam (111) and the second electron beam (112) onto the substrate, and a beam deflector array (130) for deflecting one selected of the first electron beam (111) and the second electron beam (112) onto a first surface contact (21). Specifically, the first electron beam (111) may be deflected toward the first surface contact (21) to discharge the first surface contact (21) in the discharge phase (a), and the second electron beam (112) may be deflected toward the first surface contact (21) to charge the first surface contact (21) in the charge phase (b). The above description is referenced and is not repeated herein.

[0072] The device (200) further comprises an electron detector (180) for detecting signal electrons emitted from a substrate upon impact of a second electron beam (112) which can be used to probe surface contacts, particularly after charging, and an analysis unit (181) for examining a first electrical connection (20) extending from a first surface contact (21) based on the detected signal electrons.

[0073] In some embodiments that may be combined with other embodiments described herein, the device (200) comprises a first beam column (201) for a first electron beam (111), and a second beam column (202) arranged next to the first beam column (201) for a second electron beam (112). Each of the first and second beam columns may provide a beam path for each electron beam such that the first and second electron beams propagate along different beam paths through their respective beam columns before the first and second electron beams are successively focused and deflected at the first surface contact and / or additional surface contacts.

[0074] The beam deflector array (130) may include a first beam deflector (231) provided in or below a first beam column (201) to deflect a first electron beam (111) to a predetermined position on the substrate surface, and a second beam deflector (232) provided in or below a second beam column (202) to deflect a second electron beam (112) to a predetermined position on the substrate surface. The first beam deflector (231) and / or the second beam deflector (232) may be electrostatic and / or magnetic beam deflectors that enable each electron beam to be deflected in two directions defining the substrate plane, namely the x and y directions. The first electron beam (111) and the second electron beam (112) can be deflected to the same positions within the deflection area without moving the stage. Specifically, the first beam column (201) and the second beam column (202) can be arranged very close to each other, thereby providing a deflection area that at least partially overlaps the first beam deflector (231) and the second beam deflector (232), and within this area, the first and second electron beams can be deflected to any surface contact of at least 3 cm x 3 cm, specifically at least 4 cm x 4 cm, more specifically at least 10 cm x 10 cm, or even at least 15 cm x 15 cm.

[0075] In some embodiments, the first beam column (201) and the second beam column (202) may be arranged adjacent to each other and may be tilted toward each other (see FIG. 2). For example, the first electron beam path defined by the first beam column (201) and the second electron beam path defined by the second beam column (202) may surround each other at an angle greater than 5° and less than 45°, as schematically depicted in FIG. 2. Tilting the first and second beam columns toward each other can increase the overlapping deflection area provided by the beam deflection array (130) including the first beam deflectioner (231) and the second beam deflectioner (232), even if the first and second beam deflectioners are positioned spaced apart from each other in two adjacent beam columns.

[0076] The focusing lens array (140) may include a first focusing lens (241) provided within or below the first beam column (201) to focus a first electron beam (111) propagating along a first electron beam path defined by the first beam column (201), and a second focusing lens (242) provided within or below the second beam column (202) to focus a second electron beam (112) propagating along a second electron beam path defined by the second beam column (202). The first focusing lens (241) and / or the second focusing lens (242) may each be a magnetic objective lens and / or an electrostatic objective lens. For example, the first focusing lens (241) and / or the second focusing lens (242) may include a magnetic lens component and / or an electrostatic lens component. In other embodiments, pure magnetic objective lenses or pure electrostatic objective lenses, each comprising one or more electrodes, may be provided to focus electron beams on a substrate surface.

[0077] In some embodiments, the first focusing lens (241) may include a first main focus lens and a first refocus lens, for example, an auxiliary focusing coil. The first refocus lens may be configured to ensure that the first electron beam (111) is focused on the substrate surface even in the case of a large deflection angle applied by the first deflector (231). For example, the first refocus lens may apply focus correction that depends on the deflection angle applied by the first deflector (231), which may reduce or prevent a deflection-dependent spot size or spot shape. Alternatively or additionally, the second focusing lens (242) may include a second main focus lens and a second refocus lens, for example, an auxiliary focusing coil. The second refocus lens may be configured to ensure that the second electron beam (112) is focused on the substrate surface even in the case of a large deflection angle applied by the second deflector (232).

[0078] The controller (161) may be configured to control the device (200) in the discharge phase (a) in particular, using the first focusing lens (241) and the first beam deflector (231) so that the first electron beam (111) is focused and deflected to the first surface contact to discharge the first surface contact (21). The second electron beam (112) may be deselected in the discharge phase (a), for example, blanking, blocking, or shutting off.

[0079] The controller (161) may be configured to control the device (200) in the charging phase (b) so that, in particular using the second focusing lens (242) and the second beam deflector (232), the second electron beam (112) is focused and deflected onto the first surface contact to charge the first surface contact (21). The first surface contact may be at an electrical potential predetermined by charging. The first electron beam (111) may be deselected in the charging phase (b), for example, blanked, blocked, or shut off.

[0080] The controller (161) may be further configured to control the device (200) so that the first electrical connection is examined by detecting signal electrons emitted from the substrate by an electron detector (180) following or during the charging phase (b). For example, signal electrons may be detected while probing the first surface contact (21), one or more second surface contacts (22), and / or one or more third surface contacts (23) with a second electron beam (112).

[0081] It may be advantageous to provide two separate beam columns for the first electron beam and the second electron beam, because the control of beam selection, beam deflection, and beam focusing is less complex and faster compared to a single 2-beam column adapted to continuously deflect and focus both electron beams to predetermined surface contacts. When the first beam column (201) and the second beam column (202) are positioned close to each other, a large overlapping deflection area may also be possible. For example, the first and second electron beam paths defined by the first and second beam columns may have a distance of 5 cm or less, particularly 3 cm or less, from each other. Additionally, the first and second beam columns may be tilted toward each other to further increase the overlapping deflection area. For example, a large overlapping deflection area of ​​25 cm² or more, 100 cm² or more, or even 225 cm² or more is possible.

[0082] In some embodiments, one or two additional electron beam columns (e.g., configured to generate an electron beam for discharge and an electron beam for charge) may also be arranged on other sides of the substrate so that surface contacts on the first and second surfaces of the substrate can be discharged and / or charged. For example, electrical connections connecting surface contacts on different sides of the substrate may be examined.

[0083] FIGS. 3a–3d schematically illustrate a test method according to embodiments described herein. The illustrated test method may be performed with any of the devices described herein.

[0084] In FIG. 3a, a discharge phase (a) is illustrated. A first electron beam (111) having electron energy suitable for removing negative charges is focused and deflected onto the first surface contact (21) to remove negative charges that may be present on the first surface contact (21) and the first electrical connection (20) extending therefrom.

[0085] In FIG. 3b, a charging phase (b) is illustrated. To set the first electrical connection (20) to a predetermined electric potential that allows subsequent voltage-relative measurements to be performed, a second electron beam (112) having electron energy suitable for applying negative charges is focused and deflected onto the first surface contact (21). Since the first surface contact (21) was previously discharged in the discharge phase (a), positive negative charges corresponding exactly to the predetermined electric potential can be applied by the second electron beam (112). As the second electron beam (112) is focused and deflected onto the first surface contact, charging of the surrounding substrate area can be reduced or avoided. Optionally, signal electrons (113) can be detected in advance during the charging phase (b) to verify and / or monitor whether the secondary electron signal during charging behaves in an expected manner. In particular, the secondary electron signal during charging may already indicate a defect. Specifically, if the first surface contact (21) charges faster than expected, an "open" defect may be identified, and if the first surface contact (21) charges slower than expected, a "short" defect may be identified.

[0086] In FIG. 3c, the inspection phase (c) is illustrated. A second electron beam (112) probes any one or more of the following surface contacts: a first surface contact (21), one or more second surface contacts (22) that are to be electrically connected to the first surface contact (21), and / or one or more third surface contacts (23) that are to be electrically disconnected from the first surface contact (21), particularly neighboring electrical connections. Signal electrons (113) are detected during the probing.

[0087] If the second surface contact (22) is not charged, an "open" fault (31) within the first electrical connection (20) is identified, which can be detected by probing the second surface contact (22). If the third surface contact (23) is charged, a "short" fault (32) between the first electrical connection (20) and the second electrical connection (24) is identified, which can be detected by probing the third surface contact (23). In particular, the multiple surface contacts may be probing to determine whether the respective charging state of the multiple surface contacts is correct and as expected.

[0088] After the inspection, in FIG. 3d, another discharge phase (a) is illustrated. To remove previously applied negative charges from the first surface contact (21), a first electron beam (111) having a first electron energy suitable for removing negative charges is (again) focused and deflected onto the first surface contact (21). The negative influence of previously applied charges on subsequent measurements can be reduced or avoided. After removing the charges from the first surface contact (21) after the inspection, the test of the first electrical connection (20) can be completed.

[0089] After that, a second electrical connection (24) extending from the second surface contact (22) can be similarly inspected.

[0090] Next, multiple additional electrical connections extending from multiple surface contacts can be similarly tested, and in particular, more than 1,000, or even more than 1,000,000 electrical connections can be tested in succession.

[0091] The beam deflector array (130) provides a large overlapping deflection area for the first and second electron beams, so that by deflecting the first and second electron beams in succession to a plurality of surface contacts, a plurality of electrical connections can be tested without moving the substrate. Test speed and test accuracy can be improved compared to other methods that may rely on moving the substrate and / or electron flood guns for charging.

[0092] FIG. 4 shows a flowchart of a method for testing electrical connections of a substrate according to embodiments described in this specification.

[0093] In the box (410), a substrate having a plurality of surface contacts and a plurality of electrical connections extending therefrom is placed on a stage in a vacuum chamber. The substrate may be an advanced packaging substrate or a panel-level packaging substrate.

[0094] In the box (420), negative charges are removed from the first surface contact of the substrate by focusing and deflecting a first electron beam having first electron energy onto the first surface contact.

[0095] In the box (430), negative charges are applied to the first surface contact by focusing and deflecting a second electron beam having second electron energy onto the first surface contact. By focusing and deflecting the second electron beam onto the first surface contact over a predetermined time, the first surface contact and the first electrical connection extending therefrom are set to a predetermined electrical potential.

[0096] In the box (440), the first electrical connection is inspected by detecting signal electrons emitted from the substrate when the second electron beam strikes, particularly during or after charging. As mentioned above, the boxes (430 and 440) may occur simultaneously or subsequently.

[0097] In the box (450), previously applied negative charges are removed from the first surface contact by the first electron beam.

[0098] In particular, in some embodiments described herein, one of the discharge phases (i.e., box (420) or box (450)) may be omitted. For example, in some embodiments, it may be sufficient to discharge the first surface contact after inspection.

[0099] In the box (460), a plurality of additional electrical connections can be similarly inspected by successively deflecting the first and second electron beams to the surface contacts extending from the additional electrical connections.

[0100] Although the foregoing description relates to some embodiments, other additional embodiments may be made without departing from the basic scope, and their scope is determined by the following claims.

Claims

Claim 1 A method for testing electrical connections of a substrate having a first surface contact (21) and a first electrical connection (20) extending from the first surface contact, comprising: (a) discharging the first surface contact (21) by focusing and deflecting a first electron beam (111) having a first electron energy onto the first surface contact (21); (b) charging the first surface contact (21) by focusing and deflecting a second electron beam (112) having a second electron energy different from the first electron energy onto the first surface contact (21); and (c) testing the first electrical connection (20) by detecting signal electrons emitted from the substrate. Claim 2 A method in which, in paragraph 1, (a) is performed before (b), and (a) is performed again after (c). Claim 3 A method according to claim 1, wherein for each of the plurality of surface contacts, (a), (b)+(c), and optionally (a) again are performed in this order to inspect a plurality of electrical connections connected to a plurality of surface contacts of the substrate. Claim 4 A method according to any one of claims 1 to 3, wherein a plurality of surface contacts are distributed over a substrate surface area of ​​at least 9 cm², and the first and second electron beams are continuously deflected on the plurality of surface contacts by a beam deflector arrangement without moving the stage (105). Claim 5 A method according to any one of claims 1 to 3, wherein the first electron energy is lower than the second electron energy, the first electron energy is 1 keV to 3 keV, and the second electron energy is 5 keV to 15 keV. Claim 6 A method according to any one of claims 1 to 3, wherein (c) performs voltage contrast measurements based on signal electrons detected when the second electron beam (112) or the first electron beam (111) collides with the substrate. Claim 7 A method according to any one of claims 1 to 3, wherein (c) probing any one of the following surface contacts with the second electron beam (112) or the first electron beam (111) after charging the first surface contact with the second electron beam (112): - the first surface contact (21); - one or more second surface contacts (22) to be electrically connected to the first surface contact (21) through the first electrical connection (20); and - one or more third surface contacts (23) to be electrically disconnected from the first surface contact (21). Claim 8 A method according to any one of claims 1 to 3, wherein (a) the first electron beam (111) is propagated along the common electron beam path (115) through the two-beam column (110), while the second electron beam is deselected, and (b) the second electron beam (112) is propagated along the common electron beam path (115) through the two-beam column (110), while the first electron beam is deselected. Claim 9 A method according to any one of claims 1 to 3, wherein (a) the first electron beam (111) is propagated through a first beam column (201), focused by a first focusing lens (241) of the first beam column, and deflected on the first surface contact by a first beam deflector (231) of the first beam column, and (b) the second electron beam (112) is propagated through a second beam column (202), focused by a second focusing lens (242) of the second beam column, and deflected on the first surface contact by a second beam deflector (232) of the second beam column. Claim 10 In claim 9, the first beam column (201) and the second beam column (202) are arranged next to each other and tilted toward each other. Claim 11 A method according to any one of claims 1 to 3, wherein the first electron beam is generated by a first electron source (121) having a first emission tip provided at a first potential, and the second electron beam is generated by a second electron source (122) having a second emission tip provided at a second potential. Claim 12 A method according to any one of claims 1 to 3, wherein the substrate (10) is a packaging substrate configured to provide multi-device in-package interconnection, the first electrical connection (20) is a device-to-device electrical interconnection path, and the substrate (10) is an advanced packaging (AP) substrate, a panel level packaging (PLP) substrate, a wafer level packaging (WLP) substrate, or a micro LED substrate. Claim 13 As a device (100, 200) for testing electrical connections of a substrate, a vacuum chamber (101) housing a stage (105) for placing the substrate; a first electron source (121) configured to generate a first electron beam (111) having a first electron energy; and a second electron source (122) configured to generate a second electron beam (112) having a second electron energy different from the first electron energy; A device comprising a controller (161), wherein the controller is configured to control the device such that, in a discharge phase (a), the first electron beam (111) is focused and deflected toward the first surface contact (21) to discharge the first surface contact (21); in a charge phase (b), the second electron beam (112) is focused and deflected toward the first surface contact (21) to charge the first surface contact (21); and the first electrical connection (20) connected to the first surface contact (21) is inspected by detecting signal electrons emitted by the substrate during or after the charge phase (b) with an electron detector (180). Claim 14 In claim 13, the apparatus comprises a 2-beam column (110) providing a common electron beam path (115) for the first electron beam and the second electron beam, wherein the 2-beam column comprises a beam selector (150) for selecting one of the first electron beam and the second electron beam to propagate toward the substrate through the 2-beam column (110). Claim 15 In claim 13, the apparatus comprises a first beam column (201) having a first focusing lens (241) and a first beam deflector (231) for focusing and deflecting the first electron beam (111), and a second beam column (202) having a second focusing lens (242) and a second beam deflector (232) for focusing and deflecting the second electron beam (112), wherein the first beam column and the second beam column are arranged next to each other. Claim 16 An apparatus according to any one of claims 13 to 15, comprising a beam deflector array (130) configured to deflect one selected of the first and second electron beams to a predetermined position on the substrate, and / or a focusing lens array (140) configured to focus one selected of the first and second electron beams on the substrate. Claim 17 In claim 16, the beam deflector array (130) provides an overlapping deflection area of ​​at least 9 cm² on the substrate for the first electron beam (111) and for the second electron beam (112). Claim 18 A device according to any one of claims 13 to 15, wherein, for inspecting the first electrical connection (20), the second electron beam (112) is focused and deflected to at least one of the first surface contact (21), one or more second surface contacts (22) to be electrically connected to the first surface contact, and one or more third surface contacts (23) to be electrically separated from the first surface contact, and the signal electrons emitted by each of the substrate are detected by the electron detector (180) to perform voltage contrast measurements. Claim 19 A device for testing electrical connections of a substrate, comprising: a vacuum chamber housing a stage for placing the substrate; a first electron source configured to generate a first electron beam having a first electron energy; a second electron source configured to generate a second electron beam having a second electron energy different from the first electron energy; a focusing lens array (140) configured to focus the first electron beam on the substrate in a discharge phase and focus the second electron beam on the substrate in a charge phase; a beam deflector array (130) configured to deflect the first electron beam over the first surface contact to discharge the first surface contact of the substrate in the discharge phase and to deflect the second electron beam over the first surface contact to charge the first surface contact in the charge phase; and an electron detector (180) for detecting signal electrons emitted from the substrate. A device comprising an analysis unit (181) for examining a first electrical connection (20) extending from the first surface contact (21) based on the signal electrons.

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