Method for testing a packaging substrate, and apparatus for testing a packaging substrate

Abstract

The present disclosure relates to an apparatus for testing a substrate in a vacuum chamber, the apparatus comprising: a vacuum chamber; a stage within the vacuum chamber, the stage configured to support the substrate; a sensor configured for determining a charging condition within the vacuum chamber, the sensor comprising: an antenna positioned within the vacuum chamber. Furthermore, the present disclosure relates to an according method, a computer program and a sensor.

Description

METHOD FOR TESTING A PACKAGING SUBSTRATE, AND APPARATUS FOR TESTING A PACKAGING SUBSTRATEFIELD

[0001] The present disclosure relates to an apparatus for testing a substrate in a vacuum chamber and an according method. Particularly, embodiments herein relate to determining a charging condition within the vacuum chamber (e.g., a charging state of the substrate) with an antenna positioned within the vacuum chamber.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 circuits 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] The complexity of packaging substrates is increasing and design rules (e.g., feature size) are decreasing substantially. Within such substrates, the surface contact points (for later flip chip or other chip mounting) may be connected to other surface contact points on the packaging substrate to interconnect semiconductor (or other) devices.

[0005] Various methods for electrically testing substrates are known. For example, contact pads of a substrate to be tested may be contacted with a contact probe, inorder to determine whether the component is defective or not. In other examples, it is also known to electrically test a substrate in a contactless manner with an electron beam positioned at various positions on the sample and detecting signal charge particles emitted from the tested substrate.

[0006] During loading, testing and / or unloading of the substrate in a test procedure, various charges may be applied to the substrate. For example, disadvantageous electrostatic charges may also be evoked in a substrate which may damage and / or negatively alter the substrate at least in part.

[0007] Accordingly, it would be beneficial to provide an apparatus and a method to assess and / or address a disadvantageous charging of a substrate in view of a testing of the substrate.SUMMARY

[0008] In light of the above, apparatuses for testing a substrate and according methods 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] A first aspect of the present disclosure relates to an apparatus for testing a substrate in a vacuum chamber, the apparatus comprising: a vacuum chamber; a stage within the vacuum chamber, the stage configured to support the substrate; a sensor configured for determining a charging condition within the vacuum chamber, the sensor comprising: an antenna positioned within the vacuum chamber.

[0010] A second aspect of the present disclosure relates to a method comprising: providing a substrate in a vacuum chamber of an apparatus configured for testing the substrate; receiving an electromagnetic field extending from the substrate with an antenna positioned within the vacuum chamber; determining a charging state of the substrate based on the received electromagnetic field.

[0011] A third aspect relates to a non-transitory computer-readable medium comprising instructions that, when executed by a control unit, cause performing of a method according to the second aspect.

[0012] A fourth aspect relates to a sensor for a vacuum chamber of an apparatus for testing a substrate in the vacuum chamber, the sensor comprising: a lid having a first surface and a second surface, the second surface being opposite the first surface; a vacuum feedthrough providing a vacuum-tight passage from the first surface to the second surface for at least one conductor; an antenna coupled to the first surface; a control unit coupled to the second surface; the antenna and the control unit coupled to each other through at least one conductor passing through the vacuum-tight passage; wherein a maximum distance between the antenna and the first surface of the lid is in a range between 5 mm and 150 mm.

[0013] Embodiments are also directed at apparatuses for carrying out the disclosed methods and include apparatus parts for performing each described method aspect. These 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 described herein. The methods for operating the described apparatus include method aspects for carrying out every function of the apparatus.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 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:

[0015] FIG. 1 shows a schematic sectional view of an apparatus for testing a substrate according to embodiments of the present disclosure;

[0016] FIG. 2A shows a schematic top view of a sensor according to the present disclosure that may be integrated into an apparatus for testing a substrate;

[0017] FIG. 2B shows a schematic side view of a sensor according to the present disclosure that may be integrated into an apparatus for testing a substrate;

[0018] FIG. 3 shows a schematic sectional view of an apparatus for testing a substrate according to further embodiments of the present disclosure;

[0019] FIGS. 4A and 4B show enlarged sectional views of substrates during a testing of the substrates;

[0020] FIG. 5 shows a flowchart of a method according to embodiments of the present disclosure.DETAILED DESCRIPTION

[0021] 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.

[0022] 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 enhance the understanding of the embodiments.

[0023] The present disclosure relates to testing a substrate, for example a packaging substrate, such as a panel-leveling packaging (PLP) substrate and / or an advanced packaging (AP) substrates. Particularly, the present disclosure relates to testing a substrate within a vacuum chamber.

[0024] 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.

[0025] An advanced packaging (AP) substrate provides the device-to-device electrical interconnection 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, for example material of a printed circuit board (PCB) or another compound material, including, for example ceramics and glass materials.

[0026] Panel-level-packaging 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.

[0027] The size of a panel-level-substrate may not be limited 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 thesurface 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.

[0028] When testing a substrate in a vacuum chamber a (potentially) disadvantageous charge may be induced to the substrate. The (potentially) disadvantageous charge may damage and / or negatively alter the substrate and / or other components around the substrate, at least in part. For example, an electrostatic discharge may be evoked due to an unbeneficial charge up of the substrate during a testing procedure. The electrostatic discharge may damage components of the substrate. The testing procedure may, for example, include the loading of the substrate into the vacuum chamber, a testing of the substrate, and / or the unloading of the substrate from the vacuum chamber. It may be possible that during any moment of the testing procedure, a (potentially) disadvantageous charge may be induced to the substrate.

[0029] For example, the testing may include applying controlled charges to the substrate, which may cause an unbeneficial charge-build up in the substrate, leading to the herein described disadvantageous charge effects.

[0030] Furthermore, a substrate placed on a stage within the vacuum chamber may cause a capacitor effect, which may induce disadvantageous effects. For example, when the substrate is placed on the stage, an induced charge in the substrate may create a capacitor with the substrate functioning as a first electrode of the capacitor and another part within the vacuum chamber (e.g., a part of the stage and / or a part in the vicinity to the stage) functioning as a second electrode of the capacitor. During an unloading procedure, a distance between the substrate and the stage may increase, which may cause an increase in a voltage drop across the capacitor, which could cause potentially harmful effects to the substrate and / or other components around the substrate.

[0031] According to the present disclosure, apparatuses and methods are provided to determine a charging condition within the vacuum chamber, for example, tomonitor potentially harmful charges related to the testing of the substrate within the vacuum chamber and, potentially, apply according corrective steps.

[0032] A first aspect of the present disclosure relates to an apparatus 100 for testing a substrate in a vacuum chamber, the apparatus 100 including: a vacuum chamber 110; a stage 105 within the vacuum chamber, the stage configured to support the substrate 10; a sensor configured for determining a charging condition within the vacuum chamber, the sensor including: an antenna 191 positioned within the vacuum chamber.

[0033] Particularly, FIG. 1 shows a schematic sectional view of an apparatus 100 for testing a substrate according to embodiments of the present disclosure. As can be seen in FIG. 1 , an antenna 191 is positioned within a vacuum chamber 110, with a substrate 10 being positioned on a stage 105 within the vacuum chamber 110. The apparatus 100 may be configured for testing the substrate (e.g. , in a contactless manner and / or via contact probing).

[0034] The antenna 191 being positioned within the vacuum chamber may provide an assessment of the charging condition within the vacuum chamber. Particularly, the antenna 191 may provide an assessment of the charging of the substrate 10.

[0035] For example, charges within the vacuum chamber 110 may induce an electromagnetic field (e.g., including an electrical field). The antenna 191 may be configured to react with the electromagnetic field such that an assessment of the charges within the vacuum chamber 110 may be provided by the sensor. For example, the antenna 191 may be configured as a receiving antenna. Due to the antenna 191 , the charging condition within the vacuum chamber may be monitored. The monitoring may provide the possibility for interventive steps (e.g., a countercharging and / or an interruption of the testing to avoid further charge-build).

[0036] In some embodiments, the antenna 191 may be positioned in the vacuum chamber 110 such that an electromagnetic field 199 extending from the substrate 10 can be received by the antenna.

[0037] For example, the electromagnetic field 199 may stem from a charge within the substrate 10, with the charge being induced within the substrate 10 due to the testing of the substrate 10. The charge within the substrate 10 may cause the electromagnetic field 199. The antenna 191 may be positioned such that the antenna 191 can receive the energy (and / or power) of the electromagnetic field 199 extending from the substrate 10. The signal received by the antenna 199 may be used to assess the charging of the substrate 10.

[0038] In some embodiments, the sensor may further include: a control unit 192 coupled to the antenna 191 , the control unit 192 configured to determine a charging state of the substrate 10 as the charging condition based on an electromagnetic field 199 received by the antenna 191 .

[0039] For example, the control unit may be configured to receive a signal from the antenna 191 , with the signal being associated with the electromagnetic field 199 extending from the substrate. For example, the signal may include a signal received from the antenna 191 due to the antenna 191 being exposed to the electromagnetic field 199. As described herein, the electromagnetic field 199 may stem from the charge within the substrate 10. With the coupling between the control unit 192 and the antenna 191 , the control unit 192 may be configured to determine a charging state of the substrate 10 based on the signal received from the antenna 191 .

[0040] In an example, the charging state of the substrate 10 may include an information associated with a total charge of the substrate 10. For example, the charging state of the substrate 10 may include a total charge of the substrate or a parameter that is proportional to the total charge of the substrate. For example, if the total amount of charge within the substrate is higher than a lower total amount of charge, a stronger electromagnetic field may be present, leading to a stronger signal received by the antenna. The integration of the antenna 191 and the control unit 192 may thus provide a quantitative assessment of the charging state of the substrate 10.

[0041] In an example, the charging state of the substrate 10 may include an information associated with a local charge of the substrate 10. For example, if thecharge in one part of the substrate 10 increases, an according electromagnetic field 199 increases, leading to a stronger signal received by the antenna. The integration of the antenna 191 and the control unit 192 may thus provide a quantitative assessment of the charging state of the substrate 10.

[0042] In an example, the control unit 192 may be configured to provide signal analysis and / or other computational operations (such as an algorithm) to the signal received from the antenna 191 to determine the charging state of the substrate.

[0043] In an example, the control unit may be configured to determine the charging state based on a predetermined assumption that the signal received from the antenna 191 stems from an electromagnetic field 199 generated by the charging state of the substrate 10. For example, an algorithm of the control unit 192 may account for a boundary condition that the electromagnetic field 199 extends from the substrate 10 such that the charging state of the substrate may be determined in a beneficial manner (e.g., influences of other types of sources of electromagnetic fields may be reduced at least in part by the algorithm). For example, the algorithm may be based on predetermined results (such as simulation results) that account for the potential distribution of electromagnetic fields stemming from the substrate 10.

[0044] In some embodiments, the control unit 192 may be configured to determine an electrostatic charge value associated with the charging state of the substrate based on the received electromagnetic field 199. For example, the electromagnetic field 199 may be a (substantially) electrostatic electromagnetic field. The electrostatic charge value may include an according measurement parameter for measuring an electrostatic electromagnetic field. For example, the electrostatic charge value may be addressed in the unit volt, with the electrostatic charge value providing a strength of the electrostatic field.

[0045] In some embodiments, the antenna 191 and the control unit 192 may be configured such that the control unit 192 can determine electrostatic charge values associated with the charging state of the substrate 10 in a range between 1 V and 10 V. For example, electrostatic field strengths in a range between 1 V and 10 Vmay be determined by the herein described sensor including the antenna 191 and the control unit 192.

[0046] In some embodiments, the control unit 192 may be coupled to a computer (not shown). The computer may implement some or all functionalities of the herein described control unit 192 (or vice versa). For example, the control unit 192 may be configured to perform initial operations with the signal received from the antenna 191 , and to send the processed results to the computer with the computer being configured to perform further operations to the received results. For example, the control unit 192 may be configured to determine electrostatic charge values associated with the charging state of the substrate 10 (e.g., in a continuous or periodic manner). The computer may be configured to assess the determined electrostatic charge values for monitoring purposes (e.g., the computer may assess whether the electrostatic charge values cross a predetermined threshold). The computer may be configured to trigger further operational steps (e.g., outputting of a warning and / or altering the operation of the apparatus 100) when a critical electrostatic charge value was determined. For example, if the electrostatic charge value crosses a predetermined threshold, a critical charge value may be determined. In some examples, the control unit 192 may be configured to implement the functions of the herein described computer. In some examples, the herein described computer may be configured to implement the functions of the herein described control unit 192.

[0047] In an example, the antenna may receive an electrostatic electromagnetic field due to a charge within the substrate 10. The according signal induced in the antenna may be transmitted to the control unit 192. The control unit 192 may determine the electrostatic charge value associated with the received signal (e.g., an electrostatic field strength of 3 V). The control unit 192 may send the determined electrostatic charge value (e.g., the electrostatic field strength of 3 V) to the computer. The computer may assess whether the electrostatic charge value crosses a predetermined threshold (e.g., a predetermined threshold of 2.5 V). Crossing the predetermined threshold may be associated with reaching a critical charging state of the substrate 10. If the electrostatic charge value crosses the predeterminedthreshold, further steps may be triggered (e.g., outputting of a warning and / or altering the operation of the apparatus 100).

[0048] For example, the control unit 192 and / or the computer may be communicatively coupled to various components of the apparatus 100 for operational control of the apparatus 100. For example, if a critical charging state was determined by the control unit 192 and / or the computer, the operation of the apparatus may be adjusted (e.g., to reduce the effects of the charged substrate 10 at least in part) and / or a warning may be outputted at an interface of the apparatus 10 (e.g., a visual warning at a display and / or an acoustical warning by a speaker).

[0049] In some embodiments, the sensor may be configured as an electrostatic discharge (ESD) sensor. For example, the antenna 191 and the control unit 192 may be configured as an ESD sensor. The ESD sensor and / or the computer coupled to the ESD sensor may be configured to output an ESD warning, if a critical electrostatic charge value was determined, as described herein.

[0050] In some embodiments, the control unit 192 may be positioned outside of the vacuum chamber 110. Positioning the control unit 192 outside of the vacuum chamber 110 may be beneficial since the vacuum chamber 110 does not have to be designed with consideration to the constraints of the vacuum chamber. For example, a potential risk of material outgassing of the material of the control unit 192 and / or a contamination of the vacuum chamber 110 with particles of the control unit may be reduced at least in part. For example, it may be easier to configure the antenna 191 for the constraints of the vacuum chamber than the control unit 192. For example, the control unit 192 may include various electrical components (such as one or more electrical circuits and / or one or more processors), which may not be easily adapted for the vacuum chamber. For example, the control unit 192 may also include a fan for cooling the various electrical components which may not easily be implemented within a vacuum. The antenna 191 may be adapted in a beneficial manner for the vacuum chamber 110, as the antenna 191 may be made out of fewer components, also having a reduced complexity in geometry, than the control unit 192.

[0051] In some embodiments, the antenna 191 may be coupled to the control unit 192 positioned outside of the vacuum chamber 110 via a vacuum feedthrough 194. For example, a main cable may connect the antenna 191 and the control unit 192, with the main cable going through the vacuum feedthrough.

[0052] In an example, at least a first cable part 196 of the main cable may reside within the vacuum chamber 11 , wherein a second cable part 197 may reside outside of the vacuum chamber. At least the first cable part 196 may be adapted for the vacuum of the vacuum chamber 110. For example, the first cable part 196 may include a material which is adapted for an at least partially reduced material outgassing within the vacuum.

[0053] In other examples, the connection between the antenna 191 and the control unit 192 through the vacuum feedthrough 194 may include at least two different cables. In such a case, the first cable part 196 may be considered a first cable connected between the vacuum feedthrough 194 and the antenna 191 , and the second cable part 197 may be considered a second cable connected between the vacuum feedthrough and the control unit 192. The first and second cable may be directly connected to each other (e.g., the first cable may be plugged through the vacuum feedthrough such that an end of the first cable extends outside of the vacuum chamber for connecting to the second cable). In some examples, the vacuum feedthrough may be configured to provide an electrical intermediary connection between the first cable and the second cable via an electrical segment, which provides an electrical connection through the wall of the vacuum chamber. For example, the first cable may be connected between the antenna 191 and the electrical segment at a first surface (which can correspond to an inner wall of the vacuum chamber exposed to the vacuum); and the second cable may be connected between the control unit 192 and the electrical segment at a second surface (which can correspond to an outer wall of the vacuum chamber not exposed to the vacuum).

[0054] In some embodiments, the apparatus may further include a charged particle beam column configured to provide a charged particle beam 111 on the substrate 10 for testing the substrate. The charged particle beam column may be configured to provide a contactless testing of the substrate 10.

[0055] For example, the vacuum chamber 101 may be a testing chamber specifically configured for testing or may be one vacuum chamber of a larger vacuum system, e.g. a processing chamber of a packaging substrate manufacturing or processing system.

[0056] Subsequently, a testing of the substrate with a charged particle beam 111 provided by the charged particle beam column is described with respect to a packaging substrate.

[0057] As it is schematically depicted in FIG. 1 , a packaging substrate 10 may include 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, that are both arranged at a top surface of the packaging substrate. 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 and having a plurality of surface contact points.

[0058] The packaging substrate 10 may include a plurality of device-to-device electrical interconnect paths 20 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. However, in some examples, the packaging substrate 10 may include thousands or tens of thousands of such device- to-device electrical interconnect paths, which are typically electrically isolated from each other, if no short exists between two electrical interconnect paths.

[0059] The packaging substrate 10 may be placed on a stage 105 in the vacuum chamber 110. The stage can be movable, particularly in the z-direction (e.g., in a direction perpendicular to the stage surface) and / or in the x- and y-directions (e.g.,in the plane of the stage surface). The stage 105 may be provided within the vacuum chamber and may be configured to support the packaging substrate, being one of a panel level packaging substrate and an advanced packaging substrate.

[0060] As it is schematically depicted in FIG. 1 , a charged particle beam column 120 may be provided on a first side of the stage 105. In some embodiments, which can be combined with other embodiments described herein, the charged particle beam column 120 may have a charged particle source 121 (e.g., an electron source) for generating the herein described charged particle beam 11 (e.g., an electron beam), as well as beam-optical elements, such as a scan deflector 122 and / or an objective lens 124, for directing the charged particle beam onto a substrate placed on the stage 105. The objective lens 124 may be an electrostatic objective lens (as shown in FIG. 1 ), a magnetic objective lens, or a magnetic-electrostatic objective lens.

[0061] The apparatus 100 may further include an electron detector 140 for detecting signal electrons 113 emitted upon impingement of the charged particle beam on the packaging substrate, and an analysis unit 141 configured to determine, based on the signal electrons 113, if the substrate is defective (e.g., if the first device-to-device electrical interconnect path 20 is defective).

[0062] The charged particle beam 111 (e.g., an electron beam) may be directed on the first surface contact point 21 for testing the substrate 10. The charged particle beam 111 can be scanned to be directed to that second surface contact point 22. Signal electrons 113 emitted from the second surface contact point 22 can be 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.

[0063] Alternatively or additionally, the charged particle beam 111 (e.g., the electron beam) may be directed on a further surface contact point 27 that is not an end point of the first device-to-device electrical interconnect path 20, e.g., 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 interconnectpath 20. Signal electrons emitted from the further surface contact point 27 can be 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.

[0064] 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.

[0065] In some embodiments, the analysis unit 141 may be configured to determine, based on the detected signal electrons, whether an electrical interconnect path has a defect, such as a short, an open and / or a leakage. Optionally, the analysis unit 141 may be configured to classify any 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 first device-to-device electrical interconnect path 20 is defective or not. The analysis unit 141 may be further configured to classify a determined defect. For example, 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 anelectrical connection between two electrical interconnect paths that are designed to be electrically separated.

[0066] In some embodiments, which can be combined with other embodiments described herein, the electron detector 140 may include an Everhard-Thornley detector. An energy filter 142 for the signal electrons 113 may be arranged in front of the electron detector 140, particularly in front of the Everhard-Thornley detector, as it is 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.

[0067] In some embodiments, the apparatus 100 may include a scan controller 123 connected to a scan deflector 122 of the charged particle beam column 120. The scan deflector 122 may be configured to scan the charged particle beam 111 over a substrate surface. The electron beam may be directed on a portion of the packaging substrate, e.g. with a first beam probe diameter. The portion of the packaging substrate can be an area of the packaging substrate, wherein the electron beam is scanned over the area of the packaging substrate. The electron beam can be raster scanned over the portion of the packaging substrate. For example, one or more scan deflectors 122 can scan the electron-beam over the portion of the packaging substrate. The portion of the packaging substrate may also be a surface contact point. The electron-beam can be vector scanned to one or more surface contact points of the packaging substrate. For example, one or more scan deflectors can be used to vector scan the electron-beam to one or more surface contact points.

[0068] For example, the scan controller 123 may be configured to control the scan deflectors such that the electron beam is sequentially directed to pairs of first andsecond surface contact points for testing respective device-to-device electrical interconnect paths extending between the respective pairs of first and second surface contact points. This allows a quick and reliable test of a plurality of electrical interconnect paths extending through the packaging substrate.

[0069] 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. As exemplarily shown in FIG. 1 , the controller can be connected to the power supply 130, the scan controller 123, the analysis unit 141 , the UV source assembly (source and / or shutter), and the stage 150. The controller may also be connected to the electron detector 140. Furthermore, the controller may be connected to the herein described control unit 192 and / or the computer coupled to the control unit 192.

[0070] The stage 105 may be connected to ground. The stage may be connected directly to ground, may be connected to ground via a DC power supply 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.

[0071] FIGS. 4A and 4B show enlarged sectional views of packaging substrates during a testing method that may be performed with the apparatus 100. 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.

[0072] 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 charging electron beam 111 on the first surface contact point 21 and directing the electron beam 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 the first 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 an 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.

[0073] 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.

[0074] 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.

[0075] In FIG. 4B, a short 152 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.

[0076] 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.

[0077] The testing of the substrate via the electron beam 111 may induce the herein described (potentially) disadvantageous charge to the substrate which may be assessed and / or monitored by the herein described sensor. For example, the provisioning of the charged particle beam 111 on the substrate 10 may evoke a charge within the substrate. For example, as described herein, if a critical charging state of the substrate 10 is determined (e.g., due to the testing of the substrate) further steps may be triggered (e.g., outputting of a warning and / or altering the operation of the apparatus 100).

[0078] In some embodiments, the antenna 191 of the herein described sensor may be positioned between a charged particle beam source 112 of the charged particle beam column and the stage 105. Such a positioning of the antenna 191 may provide that the electromagnetic field 199 extending from the substrate 10 can be received by the antenna 191 in a beneficial manner (e.g., since a risk of blocking the electromagnetic field 199 by other parts of the apparatus, such as the stage 105, is reduced at least in part).

[0079] In an example, the antenna 191 may be positioned above the stage 105 within the vacuum chamber. In such an example, when a substrate 10 is positioned on the stage 105, the antenna 191 is positioned above the substrate 10 such that the electromagnetic field 199 extending from the substrate can be received by the antenna 191 in a beneficial manner (e.g., since a risk of blocking theelectromagnetic field 199 by other parts of the apparatus, such as the stage, is reduced at least in part).

[0080] In some embodiments, a minimum distance of the antenna 191 to the substrate (or to the stage 105) may be in a range between 10 mm and 100 mm, more particularly between 20 mm and 100 mm, most particularly between 50 mm and 100 mm. For example, the minimum distance of the antenna 191 to the substrate (or to the stage 105) may change due to an adaptation of the stage’s position. For example, as illustrated in FIG. 1 , in some examples, the stage 105 may be positioned along the z-axis which can adapt the minimum distance of the antenna 191 to the substrate (or to the stage 105). The herein described ranges of the minimum distance of the antenna 191 to the substrate (or to the stage 105) may provide a beneficial detecting / receiving of the electromagnetic field 199.

[0081] In some embodiments, the antenna 191 may at least partially be formed in a cylindrical shape. For example, at least a part of the antenna 191 may include an envelope that follows a cylindrical shape. An antenna at least partially formed in a cylindrical shape may be easily mechanically integrated into the vacuum chamber and / or may provide a lower risk of influencing the vacuum due to the cylindrical symmetry, while providing a beneficial geometry for receiving the electromagnetic field 199.

[0082] In an example, the antenna may be at least partially formed in a disc-shape.

[0083] In some embodiments, the cylindrical shape may have a diameter in a range between 10 mm and 100 mm, particularly between 20 mm and 180 mm, more particularly between 40 mm and 60 mm. Such diameter ranges may provide a compact antenna which may provide a lower risk of influencing the vacuum while enabling a detection of the herein described charging conditions within the vacuum chamber.

[0084] In some embodiments, the antenna may have a length (e.g., across a vector perpendicular to the diameter of the cylindrical shape) in a range between 10 mm and 100 mm, particularly between 20 mm and 180 mm, more particularly between40 mm and 60 mm. Such length ranges may provide a compact antenna which may provide a lower risk of influencing the vacuum while enabling a detection of the herein described charging conditions within the vacuum chamber.

[0085] In some embodiments, the antenna 191 may include a vacuum compatible metal. With the antenna 191 including a vacuum compatible metal, a lower risk of influencing the vacuum while enabling a detection of the herein described charging conditions within the vacuum chamber can be provided.

[0086] In some embodiments, the vacuum compatible metal may include aluminum and / or stainless steel.

[0087] FIG. 2A shows a schematic top view of a sensor according to the present disclosure that may be integrated into an apparatus 100 for testing a substrate; and FIG. 2B shows a schematic side view of the sensor.

[0088] In some embodiments, the antenna 191 may be fixated to a bracket 193 with the bracket being attached to a lid 195, the lid 195 forming a part of a wall of the vacuum chamber.

[0089] Particularly, in FIG. 2B, the bracket 193 can be seen in a side view. For example, the bracket 193 may include at least two legs extending from each other in an angle. In such a case, the antenna 191 may be fixated to a lower side of a plateau portion of a first leg of the bracket, the lower side facing the vacuum chamber, particularly the stage 105, where the substrate 10 may be positioned. The upper side of the plateau portion of the first leg of the bracket may be opposite the lower side, with the upper side facing the wall 209 of the vacuum chamber 110, for example, facing the lid 195. The bracket 193 having at least two legs may be beneficial as the fixation of the bracket to the wall 209 of the vacuum chamber can be provided by the second leg of the bracket 193, and the orientation of the antenna 191 regarding the vacuum chamber can be provided by the first leg of the bracket 193. In an example, the bracket 193 may be at least partially formed in an L-shape form including two legs, with the first leg being substantially perpendicular to the second leg, as schematically shown in FIG. 2B.

[0090] In some embodiments, a maximum distance between the antenna 191 and an inner surface of the lid 195 may be in a range between 5 mm and 150 mm, particularly between 5 mm and 100 mm, more particularly between 5 mm and 50 mm, most particularly between 5 mm and 20 mm. The inner surface of the lid 195 may be the surface of the lid facing the vacuum chamber 110 (with the inner surface of the lid 195 being the surface that can be exposed to the vacuum of the vacuum chamber).

[0091] For example, the wall 209 of the vacuum chamber 110 of the apparatus 100 (and also the lid 195) may be set on a ground potential to provide an electrical termination for the vacuum chamber. Having the maximum distance between the antenna 191 and the inner surface of the lid 195 in the herein described ranges may provide that the antenna 191 can be regarded as being in a close range to the ground potential of the wall 209 of the vacuum chamber. This may be beneficial, as the shorter length from the antenna 191 to the wall 209 may provide a shorter cable for connecting the antenna 191 to the control unit 192, particularly when the control unit 192 is positioned outside of the vacuum chamber 110. For example, in view of the herein described ranges of the maximum distance between the antenna 191 and an inner surface of the lid 195, a shorter distance between the antenna 191 and the vacuum feedthrough 194 can be provided with the vacuum feedthrough 194 providing the link from the vacuum chamber 110 to the control unit 192 outside of the vacuum chamber 110. With the herein described ranges of the maximum distance between the antenna 191 and an inner surface of the lid 195, a shorter first cable part 196 can be provided between the antenna 191 and the vacuum feedthrough 194. The risk of an outgassing of material of the first cable part 196, which may negatively impact the vacuum of the vacuum chamber 110, can be reduced at least in part, since the shorter first cable part 196 may have less surface for a material outgassing.

[0092] Furthermore, with the herein described ranges of the maximum distance between the antenna 191 and an inner surface of the lid 195, the antenna 191 can be regarded as being positioned in a vicinity to the ground termination of the wall 209 of the vacuum chamber 110. Influences onto the electromagnetic field 199 tobe detected may be reduced at least in part since the antenna 191 is positioned close to the ground termination of the wall which may limit cross-talking effects, scattering or other effects that do not stem from the charging state of the substrate itself. Having the antenna in the vicinity to the ground termination may provide that the electromagnetic field 199 can propagate to the antenna 191 with at least a partially reduced impact from other sources (e.g., reducing the impact from the antenna fixation which may pick up the electromagnetic field leading to an altered electromagnetic field being detected at the antenna 191 ). Furthermore, the herein described ranges of the maximum distance between the antenna 191 and an inner surface of the lid 195, may provide a more global detection of the electromagnetic field 199, due to the larger distance to the substrate 10, which may provide a more overall assessment of the charging state of the substrate 10, compared to when the antenna would be positioned in a very close vicinity to the substrate.

[0093] In some embodiments, the control unit 192 may be attached to the lid 195, with the lid 195 being a removable lid of the wall of the vacuum chamber. For example, in FIGS. 2A and 2B a non-removable part 201 of the wall of the vacuum chamber is shown next to the lid 195, which may be a removable lid. The removable lid 195 may provide an improved integration of the herein described sensor into the apparatus 100. For example, in some applications a vacuum chamber may be easily upgraded with the herein described sensor by attaching the removable lid 195, in other applications the sensor may be easily removed by removing the lid 195 (e.g., when the sensor is not of interest, e.g., for maintenance and / or testing purposes). Furthermore, when the lid 195 is removed, adjusting of the antenna 191 , the control unit 192 and / or the bracket 193 may be performed more easily, as well as other maintenance procedures concerning the herein described sensor. For example, an exchange and / or repair of the antenna 191 may be performed by simply removing the lid 195 such that a (potentially strenuous) access from the inside of the vacuum chamber to the antenna 191 for an exchange and / or repair of the antenna 191 can be reduced at least in part.

[0094] In some embodiments, the antenna 191 may include a resistor 204, with the resistor having a resistance in the range between 100 Megaohm (MQ) to 1000000Megaohm (MQ), particularly between 1000 Megaohm (MQ) to 1000000 Megaohm (MQ), more particularly from 300000 Megaohm (MQ) to 900000 Megaohm (MQ). Having the herein described resistances may be beneficial to determining the charging condition (particularly the charging state of the substrate) within the vacuum chamber 110. For example, the resistor 204 may be connected in series to the antenna 191 . For example, the resistor 204 may be connected in series between the antenna 191 and the first cable part 196 that extends within the vacuum chamber 110. For example, the resistor may have a voltage rating to withstand voltages of the substrate of at least 0.5 kV and / or up to 10 kV, e.g. about 5 kV or more.

[0095] In some embodiments, the apparatus 100 may include a UV source assembly configured to illuminate the substrate 10 in the vacuum chamber 110 with one or more pulses of UV radiation to adapt a charge of the substrate. As shown in FIG. 3, an apparatus 100 according to the present disclosure can further include one or more UV sources 170, e.g. a UV source generating UV radiation, with the UV sources 170 being a part of the UV source assembly. The one or more UV sources 170 can be positioned at the vacuum chamber 110. For example, the one or more UV sources 170 can be positioned to allow for uniform illumination of the test area of the charged particle beam column 120. The illumination areas 172 of the UV source are depicted in FIG. 3. The apparatus 100 of FIG. 3 may include some or all the features of the apparatus 100 described with respect to FIG. 1 , which are not described again for the sake of brevity.

[0096] In an example, the apparatus may be configured to adapt the charge of the substrate with the one or more pulses of UV radiation, based at least in part on a determined charging state of the substrate. For example, an electrostatic charge value associated with the charging state of the substrate may have been determined, as described herein (e.g., an electrostatic charge value of 3 V). Accordingly, with the information on the electrostatic charge value, the UV source assembly may be controlled to adapt the charge of the substrate (e.g., to countercharge the substrate to reduce the overall charge of the substrate). For example, the herein described controller 180 may be communicatively coupled to the control unit 192 (and / or the herein described computer coupled to the controlunit 192), with the controller 180 adapting the charge of the substrate by controlling the UV sources 170.

[0097] The effect to control the substrate charge with UV radiation is the photo effect. Ions generated by the UV light with residual gas may contribute to the charge adaptation of the substrate.

[0098] According to some embodiments, which can be combined with other embodiments described herein, to control the charge of all test points (surface contact points) on an AP or PLP substrate, a vacuum ultraviolet (VUV) light source can be provided. The UV source can be integrated in the charged particle beam column and / or the vacuum chamber 110. The field of view (FOV) of the charged particle beam column, i.e. the SEM FOV, can be irradiated before a charged particle beam test sequence, particularly directly before a charged particle beam test sequence, during a charged particle beam test sequence, or after a charged particle beam test sequence. Particularly, areas of the packaging substrate such as the FOV can be irradiated without any mechanical substrate motion, for example, by the stage CV.

[0099] The apparatus 100 may include a shutter 175. The shutter 175 can be a mechanical shutter. The shutter is configured to turn on or turn off the UV radiation of the illumination areas 172. According to some embodiments, which can be combined with other embodiments described herein, the UV radiation can be turned on / off quickly or can be pulsed. For example, a UV radiation pules can be 500 ms or shorter, such as 100 ms or shorter. Particularly, a UV radiation pulse can be 10 ms or shorter. The UV radiation pulses can be provided by pulsing of the UV source or by a mechanical shutter. According to some embodiments, which can be combined with other embodiments described herein, a method may include moving a shutter to provide pulses of UV radiation while illuminating the packaging substrate with UV radiation.

[0100] According to some embodiments, which can be combined with other embodiments described herein, the wavelength of the UV radiation can be 200 nm or shorter, particularly 170 nm or shorter. Additionally or alternatively, a gasdischarge tube can be utilized to generate the radiation. For example, a Xenon lamp, a Mercury lamp, a deuterium lamp, or the like may be used. Gas discharge lamps may beneficially be operated in a continuous operation mode. According to some embodiments, which can be combined with other embodiments described herein, the shutter configured to provide UV radiation pulses can be beneficial. A UV source 170 and a shutter may be included in or may form a UV source assembly.

[0101] The herein described controller 180, the control unit 192 and / or the computer coupled to the control unit 192 may each include a central processing unit (CPU), a memory and, for example, support circuits. To facilitate control of the apparatus 100, 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 may be 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.

[0102] In some examples, the herein described computer coupled to the control unit 192 may be implemented by the herein described controller 180.

[0103] A second aspect relates to a method including: providing 501 a substrate in a vacuum chamber of an apparatus configured for testing the substrate; receiving 502 an electromagnetic field extending from the substrate with an antenna positioned within the vacuum chamber; determining 503 a charging state of the substrate based on the received electromagnetic field. Providing 501 the substrate in the vacuum chamber may include loading the substrate 10 onto the stage 105 and positioning the stage 105 within the vacuum chamber.

[0104] In some embodiments, the method of the second aspect may further include: testing the substrate 10 with a charged particle beam 111 ; unloading the substrate from the vacuum chamber after testing the substrate.

[0105] In some embodiments, the method may further include: determining an electrostatic charge value associated with the charging state of the substrate 10 based on the received electromagnetic field.

[0106] For example, as described herein, the electromagnetic field 199 may be a (substantially) electrostatic electromagnetic field. The electrostatic charge value may include an according measurement parameter for measuring an electrostatic electromagnetic field. For example, the electrostatic charge value may be addressed in the unit volt, with the electrostatic charge value providing a strength of the electrostatic field.

[0107] In some embodiments, the antenna 191 and the control unit 192 may be configured such that the control unit 192 can determine electrostatic charge values associated with the charging state of the substrate 10 in a range between 1 V and 10 V. For example, electrostatic field strengths in a range between 1 V and 10 V may be determined by the herein described sensor including the antenna 191 and the control unit 192.

[0108] In some embodiments, the method may further include outputting a warning when the electrostatic charge value crosses a predetermined threshold.

[0109] In some embodiments, the method may further include altering the operation of the apparatus configured for testing the substrate when the electrostatic charge value crosses a predetermined threshold. For example, altering the operation of the apparatus may include interrupting and / or aborting a testing of the substrate. Furthermore, altering the operation of the apparatus may include counter charging the substrate by the apparatus (e.g., with an UV charging as described herein).

[0110] In some embodiments, the method may further include determining the charging state of the substrate continuously and / or periodically when the substrate 10 is positioned within the vacuum chamber.

[0111] Even if not explicitly mentioned as method steps or method operations, features, examples and / or embodiments described herein with respect to the apparatus of the first aspect may accordingly be applied to the method of the second aspect (and vice versa).

[0112] A third aspect relates to a non-transitory computer-readable medium including instructions that, when executed by a control unit (and / or a computer), cause performing of a method according to the second aspect. For example, the method of the second aspect may be performed by an apparatus according to the first aspect. In an example, the herein described control unit 192 and / or the computer coupled to the control unit 192 may include the non-transitory computer- readable medium of the third aspect to enable that the apparatus 100 of the first aspect may perform the method of the second aspect.

[0113] For example, the third aspect may relate to a computer program including instructions that, when executed (e.g., by a control unit and / or computer), cause performing of a method according to the second aspect (e.g., by the apparatus of the first aspect).

[0114] Even if not explicitly mentioned as computer-implemented steps or computer-implemented method operations, features, examples and / or embodiments described herein with respect to the apparatus of the first aspect (or the method of the second aspect) may accordingly be applied to the third aspect (and vice versa).

[0115] A fourth aspect relates to a sensor for a vacuum chamber of an apparatus 100 for testing a substrate in the vacuum chamber, the sensor including: a lid 195 having a first surface and a second surface, the second surface being opposite the first surface; a vacuum feedthrough 194 providing a vacuum-tight passage from the first surface to the second surface for at least one conductor; an antenna 191coupled to the first surface; a control unit 192 coupled to the second surface; the antenna and the control unit coupled to each other through at least one conductor passing through the vacuum-tight passage; wherein a maximum distance between the antenna 191 and the first surface of the lid 195 is in a range between 5 mm and 150 mm, particularly between 5 mm and 100 mm, more particularly between 5 mm and 50 mm, most particularly between 5 mm and 20 mm.

[0116] An exemplary sensor of the first aspect (integrated into the apparatus 100) is shown in FIGS. 2A and 2B.

[0117] In some embodiments of the fourth aspect, the control unit 192 may be configured to determine a charging condition within the vacuum chamber based on an electromagnetic field received by the antenna.

[0118] Features, examples and / or embodiments described herein with respect to the apparatus of the first aspect may accordingly be applied to the sensor of the fourth aspect (and vice versa). For example, features described regarding the antenna 191 , the control unit 192, the vacuum-feedthrough 194, and / or the lid 195 of the apparatus 100 of the first aspect may also be features of the sensor of the fourth aspect (and vice versa).

[0119] 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

CLAIMS1. An apparatus (100) for testing a substrate in a vacuum chamber, the apparatus comprising: a vacuum chamber (110); a stage (105) within the vacuum chamber, the stage configured to support the substrate (10); a sensor configured for determining a charging condition within the vacuum chamber, the sensor comprising: an antenna (191 ) positioned within the vacuum chamber.

2. The apparatus according to claim 1 , further comprising: a charged particle beam column configured to provide a charged particle beam (111 ) on the substrate (10) for testing the substrate.

3. The apparatus according to claim 1 or 2, wherein the antenna (191) is positioned in the vacuum chamber (110) such that an electromagnetic field (199) extending from the substrate (10) can be received by the antenna.

4. The apparatus according to any of claims 1 -3, the sensor further comprising: a control unit (192) coupled to the antenna (191 ), the control unit (192) configured to determine a charging state of the substrate (10) as the charging condition based on an electromagnetic field (199) received by the antenna (191 ).

5. The apparatus according to claim 4, wherein the control unit (192) is configured to determine an electrostatic charge value associated with the charging state of the substrate based on the received electromagnetic field (199).

6. The apparatus according to claim 5, wherein the antenna (191 ) and the control unit (192) are configured such that the control unit can determine electrostatic charge values associated with the charging state of the substrate (10) in a range between 1 V and 10 V.

7. The apparatus according to any of claims 4-6, wherein the control unit (192) is positioned outside of the vacuum chamber (110).

8. The apparatus according to claim 7, wherein the antenna (191 ) is coupled to the control unit (192) positioned outside of the vacuum chamber (110) via a vacuum feedthrough (194).

9. The apparatus according to any of claims 2-8, wherein the antenna (191 ) is positioned between a charged particle beam source (112) of the charged particle beam column and the stage (105).

10. The apparatus according to any of claims 1 -9, wherein the antenna (191 ) is at least partially formed in a cylindrical shape.

11. The apparatus according to claim 10, wherein the cylindrical shape has a diameter in a range between 10 mm and 100 mm, particularly between 20 mm and 180 mm, more particularly between 40 mm and 60 mm.

12. The apparatus according to any of claims 1-11 , wherein the antenna (191 ) comprises a vacuum compatible metal.

13. The apparatus according to claim 12, wherein the vacuum compatible metal comprises aluminum and / or stainless steel.

14. The apparatus according to any of claims 1 -13, wherein the antenna (191 ) is fixated to a bracket (193) with the bracket being attached to a lid (195), the lid forming a part of a wall of the vacuum chamber.

15. The apparatus according to claim 14, wherein a maximum distance between the antenna (191 ) and an inner surface of the lid (195) is in a range between 5 mm and 150 mm, particularly 5 mm and 100 mm, more particularly 5 mm and 50 mm, most particularly 5 mm and 20 mm.

16. The apparatus according to claim 14 or 15, referred back to any of claims 4- 13, wherein the control unit (192) is attached to the lid (195), with the lid being a removable lid of the wall of the vacuum chamber.

17. The apparatus according to any of claims 1-16, wherein the antenna (191 ) comprises a resistor, with the resistor having a resistance in the rangebetween 100 Megaohm to 1000000 Megaohm, particularly between 1000 Megaohm to 1000000 Megaohm, more particularly from 300000 Megaohm to 900000 Megaohm.

18. The apparatus according to any of claims 1 -17, further comprising: a UV source assembly configured to illuminate the substrate (10) in the vacuum chamber (110) with one or more pulses of UV radiation to adapt a charge of the substrate.

19. A method comprising: providing (501 ) a substrate in a vacuum chamber of an apparatus configured for testing the substrate; receiving (502) an electromagnetic field extending from the substrate with an antenna positioned within the vacuum chamber; determining (503) a charging state of the substrate based on the received electromagnetic field.

20. The method according to claim 19, further comprising: testing the substrate (10) with a charged particle beam (111 ); unloading the substrate from the vacuum chamber after testing the substrate.21 . The method according to any of claims 19 or 20, further comprising: determining an electrostatic charge value associated with the charging state of the substrate (10) based on the received electromagnetic field.

22. The method according to claim 21 , further comprising: outputting a warning when the electrostatic charge value crosses a predetermined threshold.

23. A non-transitory computer-readable medium comprising instructions that, when executed by a control unit, cause performing of a method according to any of claims 19 to 22.

24. Sensor for a vacuum chamber of an apparatus (100) for testing a substrate in the vacuum chamber, the sensor comprising: a lid (195) having a first surface and a second surface, the second surface being opposite the first surface; a vacuum feedthrough (194) providing a vacuum-tight passage from the first surface to the second surface for at least one conductor; an antenna (191 ) coupled to the first surface; a control unit (192) coupled to the second surface; the antenna and the control unit coupled to each other through at least one conductor passing through the vacuum-tight passage; wherein a maximum distance between the antenna (191 ) and the first surface of the lid (195) is in a range between 5 mm and 150 mm.

25. The sensor according to claim 24, wherein the control unit (192) configured to determine a charging condition within the vacuum chamber based on an electromagnetic field received by the antenna.

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