Evaluation of contact between the wafer and the electrostatic chuck

Abstract

To provide a method for evaluating contact between a wafer and an electrostatic chuck, a nontransitory computer-readable medium, and a device.SOLUTION: A method may include: (a) introducing a voltage difference between an absolute value of a negative pole of the electrostatic chuck and an absolute value of a positive pole of the electrostatic chuck, in which the introducing occurs while the wafer is supported by the electrostatic chuck and is contacted by one or more conductive contact pins of the electrostatic chuck; (b) monitoring, by an electrostatic sensor that comprises a sensing element, a charge at a point of measurement located at a front side of the wafer, at different points of time that follow a start of the introducing of the voltage difference, to provide monitoring results; and (c) determining an electrical parameter of the contact between the wafer and the electrostatic chuck, based on the monitoring results.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] Cross-reference This application claims priority to U.S. Patent Application No. 17 / 115,656, filed on December 8, 2020. The disclosure thereof is incorporated herein by reference in its entirety for all purposes.

Background Art

[0002] A wafer can be evaluated by an evaluation system such as, but not limited to, a scanning electron microscope (SEM).

[0003] Ideally, when supported by an electrostatic chuck, the front surface of the wafer should be uniformly charged. In practice, the front surface of the wafer may be non-uniformly charged. Non-uniform charging may introduce measurement errors. A typical measurement error may involve an undesirable deflection of the electron beam scanning the wafer.

[0004] The evaluation of the charging of the front surface of the wafer should be performed without contacting the wafer and without contaminating the wafer.

[0005] There is an increasing need to provide a non-contact and non-contaminating method for evaluating the charging of the front surface of the wafer.

[0006] A wafer can be supported by a mechanical stage, by an electrostatic chuck, or by a support element. The support element may not belong to the mechanical stage and may not belong to the electrostatic chuck.

[0007] During the evaluation of the wafer, the wafer may be supported by an electrostatic chuck. The electrostatic chuck may be supported by a mechanical stage.

Summary of the Invention

Problems to be Solved by the Invention

[0008] At various points in time (for example, after wafer evaluation), wafers may be moved away from the mechanical stage. In some cases, wafers may become charged by jumping when they are far enough away from the mechanical stage. This jumping can damage the wafer.

[0009] The need to predict jumps, and even prevent them, is increasing.

[0010] When a wafer is supported by an electrostatic chuck, it can make contact with multiple pins that should be grounded. Grounding can fail for various reasons, including an insulating layer formed on the back surface of the wafer.

[0011] There is a growing need to evaluate the quality of contact between the wafer and the pins. [Means for solving the problem]

[0012] Some embodiments of the present invention relate to a method, a non-transient computer-readable medium, and a system for evaluating contact between a wafer and an electrostatic chuck.

[0013] Subject matter that is considered an embodiment of this disclosure is specifically pointed out and expressly claimed in the concluding section of this specification. However, embodiments of this disclosure, with respect to both their configuration and operation, as well as their object, features, and advantages, can be best understood by referring to the following detailed description when read together with the accompanying drawings. [Brief explanation of the drawing]

[0014] [Figure 1] This figure shows an example of the method. [Figure 2] This figure shows examples of wafer and charged particle systems. [Figure 3] This figure shows an example of an electrostatic sensor. [Figure 4] This figure shows an example of the method. [Figure 5]This figure shows examples of several parts of a wafer and charged particle system. [Figure 6] This figure shows an example of introducing a voltage difference. [Figure 7] This figure shows an example of the method. [Figure 8] This figure shows an example of the relationship between voltage and distance. [Figure 9] This figure shows an example of introducing a distance between the wafer and the mechanical stage. [Modes for carrying out the invention]

[0015] The following detailed description includes numerous specific details to provide a complete understanding of the embodiments of this disclosure.

[0016] However, it will be understood by those skilled in the art that the embodiments of this disclosure can be implemented without these specific details. In other cases, well-known methods, procedures, and components are not described in detail so as not to obscure the embodiments of this disclosure.

[0017] Subject matter that is considered an embodiment of this disclosure is specifically pointed out and expressly claimed in the concluding section of this specification. However, embodiments of this disclosure, with respect to both their configuration and operation, as well as their object, features, and advantages, can be best understood by referring to the following detailed description when read together with the accompanying drawings.

[0018] For the sake of simplicity and clarity, please understand that the elements shown in the diagrams are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated compared to others for clarity. Furthermore, where deemed appropriate, reference figures may be repeated between diagrams to indicate corresponding or similar elements.

[0019] The illustrated embodiments of the present disclosure can be implemented mostly using electronic components and circuits known to those skilled in the art. Therefore, details will not be described beyond what is considered necessary for an understanding and appreciation of the concepts underlying these embodiments of the present disclosure and so as not to obscure or depart from the teachings of these embodiments of the present disclosure as illustrated above.

[0020] Any reference in this specification to a method should be applied, with the necessary changes, to a system capable of performing the method and, with the necessary changes, to a non-transitory computer-readable medium storing instructions for performing the method.

[0021] Any reference in this specification to a system should be applied, with the necessary changes, to a method that can be performed by the system and, with the necessary changes, to a non-transitory computer-readable medium storing instructions executable by the system.

[0022] Any reference in this specification to a non-transitory computer-readable medium should be applied, with the necessary changes, to a method that can be applied when executing instructions stored on the computer-readable medium and, with the necessary changes, to a system configured to execute instructions stored on the computer-readable medium.

[0023] Methods, devices, and non-transitory computer-readable media that can use an electrostatic sensor are provided.

[0024] The electrostatic sensor can include a sensing element. The sensing element may be a Kelvin probe or may be different from a Kelvin probe. For simplicity of explanation, the following text may relate to a Kelvin probe. Other types of electrostatic sensors may be used.

[0025] Evaluation of the charge distribution in a region on the front surface of a wafer A method for evaluating the charge distribution in a front region of a wafer can be provided. The region may cover the entire wafer or only a portion of it. This method can be applied to multiple regions of a wafer.

[0026] The charge distribution may include charge values ​​at two or more points on the wafer, and additionally or alternatively, charge values ​​between two or more points on the wafer. The two or more points may form an array of points. The points may be separated from each other by a distance in the range of centimeters (for example, in the range of 0.1 centimeters to 10 centimeters).

[0027] This distance may be less than 0.1 centimeters, and additionally or alternatively, may exceed 10 centimeters. The points may be uniformly distributed across the region, or they may be unevenly distributed across the region.

[0028] A charged particle system is a system configured to evaluate a wafer (or a portion of a wafer), which involves irradiating the wafer (or a portion of a wafer) with one or more charged particle beams, such as an electron beam. Non-exclusive examples of charged particle systems include electron beam imaging devices and, but are not limited to, electron microscopes, such as scanning electron microscopes.

[0029] The evaluation may include at least one of the following: defect review, inspection, and metrology (e.g., limit dimension measurement).

[0030] For the sake of simplicity, some of the figures and text refer to scanning electron microscopes (SEMs), such as the review SEM.

[0031] Figure 1 shows a method 100 for evaluating the charge distribution in a region.

[0032] Method 100 can be initiated by initialization step 105.

[0033] The initialization step 105 may include placing a wafer on an electrostatic chuck of the charged particle system.

[0034] Step 105 may be followed by step 110, in which the charge distribution is evaluated using an electrostatic sensor.

[0035] The electrostatic sensor includes a sealed sensing element located within the internal space of a vacuum chamber in a charged particle system. Sealing prevents contamination of the internal space by the sensing element.

[0036] The sensing element may be a movable Kelvin probe. The Kelvin probe can move between different positions during charge measurement. This movement may include vibration, oscillation, etc.

[0037] Step 110 may include performing charge measurements at different locations within the region.

[0038] Charge measurement may involve performing a voltage measurement at a specific location within a region by moving (e.g., vibrating, or additionally, oscillating) a movable Kelvin probe. This movement is relatively small, e.g., a few millimeters. The voltage measurement indicates the charge at a specific point.

[0039] At a specific location, the Kelvin probe can be moved along any path. This path may be horizontal, vertical, oblique, or curved.

[0040] At a specific location, the Kelvin probe can be moved between a first position and a second position. When in the first position, the Kelvin probe may be masked, thereby preventing it from sensing the voltage in that region. When in the second position, the Kelvin probe is not masked.

[0041] Following the measurement (at a specific location), (a) move at least one of the wafer and the electrostatic sensor so that the electrostatic sensor faces a different location, and (b) perform a voltage measurement at the other location.

[0042] The number of repetitions of measurement and movement may exceed two.

[0043] The movement may be performed by a mechanical stage that moves the wafer within a vacuum chamber.

[0044] The mechanical stage can receive wafers from another mechanical unit, such as a robot or another mechanical unit used to move wafers between the load lock and vacuum chamber of a charged particle system.

[0045] Step 110 is followed by step 120, which involves evaluating the area. This may include a defect review of suspected defects in the area, and measurement of the limit dimensions of structural elements in the area.

[0046] Furthermore, step 110 may be followed by step 125, in which at least one evaluation parameter is determined based on the evaluated charge distribution of the region. The evaluation parameter may be the deflection scheme of the electron beam used to irradiate the wafer during wafer evaluation. The deflection scheme can cancel out (or at least mitigate) the non-uniformity of the charge distribution on the front surface of the wafer.

[0047] Figure 2 shows a wafer 130 and a charged particle system 140, which includes an electrostatic sensor 150, a load lock 142, an electrostatic chuck 128 (located below the wafer 130), a vacuum chamber 144, a charged particle column 146, an optical microscope 147, a processor 148, and a controller 149.

[0048] Figure 2 also shows different measurement points 131 located within region 132 of wafer 130. The region may be of any shape (polygon, curved shape, circle, ellipse, etc.), and additionally or alternatively, the region may be of any size.

[0049] The load lock 142 may be an interface between the charged particle system 140 and its environment. The load lock 142 can receive wafers from a wafer cassette connected to the interface.

[0050] A robotic arm (not shown) can move the wafer between the load lock 142 and the vacuum chamber 144.

[0051] The charged particle column 146 may have a leading or trailing end, and additionally or alternatively, a lens positioned within the vacuum chamber 144.

[0052] The electrostatic sensor 150, or at least the lower part of the electrostatic sensor 150, may be located inside the vacuum chamber 144. For example, the electrostatic sensor 150 may have a sensing element, such as a sensing probe, that is sealed from the internal space of the vacuum chamber to prevent contamination.

[0053] The optical microscope 147 can view the wafer 130 through a window formed in the vacuum chamber 144.

[0054] The wafer 130 may be supported by an electrostatic chuck 183, which can be moved by a mechanical stage (not shown) while inside the vacuum chamber.

[0055] The controller 149 is configured to control the operation of the charged particle system 140.

[0056] The processor 148 is configured to process the signal output from the electrostatic sensor 150 and can perform at least some steps of method 100.

[0057] Figure 3 shows a cross-section of the electrostatic sensor 150.

[0058] The electrostatic sensor 150 includes a conductive seal 151, a sealed housing 152, a movable grounding element 153, a first mechanical unit 155 configured to move the movable grounding element 153, a conductor 156, a second mechanical unit 157 configured to move a sensing element, a sensing element such as a Kelvin probe 159, and an internal mask 158.

[0059] The inductive seal 151 is sealed to the sealed housing 152 to isolate the inside of the electrostatic sensor 150, particularly the Kelvin probe 159, the first mechanical unit 155, and the second mechanical unit 157, from the internal space of the vacuum chamber to prevent contamination of the wafer.

[0060] It should be noted that the first mechanical unit 155 may be located outside the electrostatic sensor 150.

[0061] The second mechanical unit 157 can vibrate the Kelvin probe during any charge measurement, and additionally or alternatively, it can be oscillated.

[0062] The movable grounding element 153 can be moved (by the first mechanical unit 155) between (a) a grounding position in which the movable grounding element is electrically coupled to the sensing element and (b) a disconnection position in which the movable grounding element is not electrically coupled to the sensing element.

[0063] Evaluation of contact between the wafer and the electrostatic chuck Figure 4 shows a method 300 for evaluating contact between a wafer and an electrostatic chuck.

[0064] Method 300 can be initiated by initialization step 305.

[0065] The initialization step 305 may include placing the wafer on an electrostatic chuck of the charged particle system.

[0066] The initialization step 305 may also include positioning one or more conductive contact pins (or other conductive elements) of the electrostatic chuck in positions where they are expected to contact the wafer. For example, if the pins need to contact the wafer when they are in the upper position, the pins are positioned in the upper position.

[0067] The initialization step 305 may be followed by step 310, which introduces a voltage difference between the absolute value of the negative electrode of the electrostatic chuck and the absolute value of the positive electrode of the electrostatic chuck.

[0068] The voltage difference may be steep, and for example, a change of several tens of volts may be introduced over a period of time on a millisecond scale (e.g., 1 to 90 milliseconds).

[0069] Furthermore, after the initialization step 305, a step 320 may follow in which an electrostatic sensor monitors the charge at a measurement point located on the front of the wafer at different points in time after the introduction of the voltage difference. The result of step 320 is the monitoring result.

[0070] The electrostatic sensor may be any of the electrostatic sensors described above.

[0071] For example, an electrostatic sensor may include a sensing element sealed from the internal space of a vacuum chamber in a charged particle system. The sensing element may be a Kelvin probe. The electrostatic sensor may include a mechanical unit for moving the Kelvin probe during charge measurement. The electrostatic sensor may include a conductive sealing element that seals the sensing element. The electrostatic sensor may include a movable grounding element configured to move between a grounded position in which the movable grounding element is electrically coupled to the sensing element and a disconnected position in which the movable grounding element is not electrically coupled to the sensing element.

[0072] Method 300 may also include step 330 of obtaining an estimate of the capacitance of a virtual capacitor formed by the wafer and the electrostatic chuck.

[0073] Step 330 may include measuring the capacitance using a capacitive electrostatic sensor or receiving the capacitance estimated by other means.

[0074] Steps 320 and 330 may be followed by step 340, in which the electrical parameters of the contact between the wafer and the electrostatic chuck are determined based on the monitoring results.

[0075] The electrical parameter may also be the contact resistance. Since multiple conductive pins may contact the wafer at multiple locations, the contact resistance represents the overall effect of the multiple conductive pins. In other words, the resistance can represent the virtual resistance formed between the wafer and the electrostatic chuck.

[0076] The introduction of a voltage difference can be seen as charging the resistor-capacitor circuit, and the charging pattern that forms over time can represent the discharge of the resistor-capacitor circuit (unless the wafer is completely disconnected from the electrostatic chuck).

[0077] Therefore, step 340 may include approximating the charging pattern represented by the monitoring results to the discharge curve of the resistor-capacitor circuit.

[0078] The voltage difference may be steep, for example, at a rate of at least 1 volt per millisecond.

[0079] Figure 5 shows an example of an electrostatic chuck 183, wafer 130, controller 149, positive power supply 188, and negative power supply 189.

[0080] The wafer 130 is supported by an electrostatic chuck 183. The electrostatic chuck 183 includes a positive electrode 185, a negative electrode 186, and one or more conductive contact pins 187 that can move toward or away from the wafer 130.

[0081] The positive electrode 185 is powered by the positive power supply 188. The negative power supply 189 supplies power to the negative electrode 186.

[0082] The controller 149 can control the voltage supplied by any of the power sources.

[0083] Figure 6 shows the introduction of a voltage difference between the absolute value of the negative electrode and the absolute value of the positive electrode of the electrostatic chuck.

[0084] Figure 6 includes graphs 359 and 358. The x-axis represents time, and the y-axis represents the voltage reading from the electrostatic sensor.

[0085] Graph 358 includes a curve 351 showing the step function 351, which is the introduction of a voltage difference.

[0086] Graph 359 shows the response to the introduction of a voltage difference.

[0087] The charging pattern 352 follows a step function, indicating that the electrostatic chuck and the wafer are completely disconnected.

[0088] Charging patterns 353, 354, and 355 show the charging patterns obtained for different resistance values ​​between the electrostatic chuck and the wafer, e.g., 50 megaohms, 10 megaohms, and 1 megaohm, respectively. The capacitance was 10 nanofarads.

[0089] Predicting wafer jump Figure 7 shows an example of a method 500 for predicting wafer jumps.

[0090] Method 500 can be initiated by step 510, which involves obtaining a predictor that predicts whether the wafer will jump as a result of an increase in the distance between the wafer and the mechanical stage of the evaluation system.

[0091] Predictors can be generated based on changes in wafer voltage under different connectivity conditions between the wafer and the evaluation system. This change is caused by varying the distance between the wafer and the mechanical stage.

[0092] A predictor can refer to a pattern in which the voltage measured by an electrostatic sensor changes. For example, a predictor can refer to the rate of change of the voltage, the voltage range in which the voltage changes, etc.

[0093] Different connectivity conditions can refer to connections with different conductivity. Conductivity can be affected by various parameters, such as the spatial relationship between the wafer and the mechanical stage (e.g., whether the wafer is parallel to the mechanical stage, whether the wafer is warped, the minimum distance between the wafer and the mechanical stage), and the presence or absence of a discharge path to the wafer.

[0094] Step 510 may be followed by step 520, in which the voltage of a region of the wafer is monitored by an electrostatic sensor.

[0095] The electrostatic sensor may be any of the electrostatic sensors described above.

[0096] An electrostatic sensor may include a sensing element sealed from the internal space of a vacuum chamber in a charged particle system. The sensing element may be a Kelvin probe. The electrostatic sensor may include a mechanical unit for moving the Kelvin probe during charge measurement. The electrostatic sensor may include a conductive sealing element that seals the sensing element. The electrostatic sensor may include a movable grounding element configured to move between a grounded position in which the movable grounding element is electrically coupled to the sensing element and a disconnected position in which the movable grounding element is not electrically coupled to the sensing element.

[0097] Monitoring is performed during the monitoring period in which the distance between the wafer and the mechanical stage increases, and the monitoring provides monitoring results.

[0098] Step 520 may be followed by step 530, which predicts whether the wafer will jump, and the prediction is based on the predictor and monitoring results.

[0099] Furthermore, step 520 may be followed by step 540, which predicts the timing of the generation of an electric arc between the wafer and the measurement system.

[0100] Step 530 and 540 may be followed by step 550, which responds to the prediction.

[0101] Step 550 may include generating a warning, stopping the increase in the distance between the wafer and the mechanical stage before the predicted timing of the occurrence of an electric arc, or performing any other response.

[0102] Figure 8 shows an example of the relationship between voltage and distance, as indicated by the first curve 561, the second curve 562, the third curve 563, and the fourth curve 564.

[0103] The first curve 561 and the second curve 562 represent the case where the wafer did not jump.

[0104] The third curve 563 and the fourth curve 564 show the cases where the wafer jumped and an arc was formed between the wafer and its surroundings (event 564(1) and arc 564(2)). Each arc discharged the wafer.

[0105] Figure 9 shows an example where the distance between the wafer and the mechanical stage is increased by 700.

[0106] The upper part of Figure 9 shows a wafer 130 supported by pins 181 and an electrostatic chuck 183. The electrostatic chuck 183 is supported by a mechanical stage 182.

[0107] The central portion of Figure 2 shows that a distance of 700 is introduced between the wafer 130 and the electrostatic chuck 182 by lowering the mechanical stage 182 that supports the electrostatic chuck 183.

[0108] The lower part of Figure 9 shows that a distance of 700 is introduced between the wafer 130 and the electrostatic chuck 183 by raising the pin 181 that raises the wafer.

[0109] A method can be provided for evaluating the charge distribution of a front region of a wafer, which may include evaluating the charge distribution of the region using an electrostatic sensor that may include a sensing element that can be sealed from the internal space of a vacuum chamber of a charged particle system, and this evaluation may include performing charge measurements at different measurement points within the region.

[0110] The sensing element may be a Kelvin probe, and the electrostatic sensor may include a mechanical unit for moving the Kelvin probe during charge measurement.

[0111] The electrostatic sensor may include a conductive sealing element that encloses the sensing element.

[0112] The electrostatic sensor may include a movable grounding element that can be configured to move between a grounding position in which the movable grounding element can be electrically coupled to a sensing element and a disconnection position in which the movable grounding element cannot be electrically coupled to the sensing element.

[0113] This method may include determining at least one evaluation parameter used during the evaluation of the region, and this determination may be based on the evaluated charge distribution of the region.

[0114] This method may include moving a wafer between one of two different locations and another of two different locations, and this movement may be performed by a mechanical stage of a charged particle system.

[0115] A device can be provided for evaluating the charge distribution of a front region of a wafer, which may include a processing circuit and an electrostatic sensor that may include a sensing element that can be sealed from the internal space of a vacuum chamber of a charged particle system, the electrostatic sensor may be configured to perform charge measurements at different measurement points within the region, and the processing circuit may be configured to evaluate the charge distribution of the region based on the charge measurements.

[0116] The sensing element may be a Kelvin probe, and the electrostatic sensor may include a mechanical unit for moving the Kelvin probe during charge measurement.

[0117] The electrostatic sensor may include a conductive sealing element that encloses the sensing element.

[0118] The electrostatic sensor may include a movable grounding element that can be configured to move between a grounding position in which the movable grounding element can be electrically coupled to a sensing element and a disconnection position in which the movable grounding element cannot be electrically coupled to the sensing element.

[0119] The processing circuit can be configured to determine at least one evaluation parameter of the wafer based on the evaluated charge distribution of the region.

[0120] A non-transient computer-readable medium can be provided for evaluating the charge distribution of a region on the front surface of a wafer. The non-transient computer-readable medium stores instructions for evaluating the charge distribution of the region using an electrostatic sensor that may include a sensing element that can be sealed from the internal space of a vacuum chamber of a charged particle system, and this evaluation may include performing charge measurements at different measurement points within the region.

[0121] A method for predicting wafer jumps can be provided, the method including the steps of: obtaining a predictor that predicts whether a wafer will jump as a result of an increase in the distance between the wafer and a mechanical stage of a charged particle system, the predictor may be generated based on a change in the voltage of the wafer under different connectivity conditions between the wafer and the charged particle system, the change may be caused by a change in the distance between the wafer and the mechanical stage; monitoring the voltage of a region of the wafer by an electrostatic sensor which may include a sensing element, the monitoring being performed during a monitoring period in which the distance between the wafer and the mechanical stage may increase, and providing the monitoring results; and predicting whether the wafer will jump, the prediction may be based on the predictor and the monitoring results.

[0122] This method may include the step of predicting the timing of the generation of an electric arc between the wafer and the measurement system.

[0123] This method may include stopping the increase in the distance between the wafer and the mechanical stage before the predicted timing of electric arc generation.

[0124] The predictor may also be the rate of increase in voltage for each increase in distance.

[0125] This method may include generating predictors.

[0126] The sensing element may be a Kelvin probe, and the electrostatic sensor may include a mechanical unit for moving the Kelvin probe during monitoring.

[0127] The electrostatic sensor may include a conductive sealing element that encloses the sensing element.

[0128] The electrostatic sensor may include a movable grounding element that can be configured to move between a grounding position in which the movable grounding element can be electrically coupled to a sensing element and a disconnection position in which the movable grounding element cannot be electrically coupled to the sensing element.

[0129] A device can be provided for predicting wafer jumps, the device may include a processing circuit and an electrostatic sensor which may include a sensing element, the electrostatic sensor which may be configured to monitor the voltage of a region of the wafer, the monitoring being performed during a monitoring period in which the distance between the wafer and a mechanical stage belonging to a charged particle system may increase, and the monitoring results are provided, the processing circuit which may be configured to obtain a predictor which predicts whether the wafer will jump as a result of the increase in the distance between the wafer and the mechanical stage, the predictor which may be generated based on changes in the voltage of the wafer under different connectivity conditions between the wafer and the charged particle system, the change which may be caused by changing the distance between the wafer and the mechanical stage, and the processing circuit which may be configured to predict whether the wafer will jump, the prediction which may be based on the predictor and the monitoring results.

[0130] The processing circuit may be configured to predict the timing of the generation of an electric arc between the wafer and the measurement system.

[0131] The processing circuit may be configured to stop increasing the distance between the wafer and the mechanical stage before the predicted timing of electric arc generation.

[0132] The predictor may also be the rate of increase in voltage for each increase in distance.

[0133] The processing circuit may be configured to generate predictors.

[0134] The sensing element may be a Kelvin probe, and the electrostatic sensor may include a mechanical unit for moving the Kelvin probe during monitoring.

[0135] The electrostatic sensor may include a conductive sealing element that encloses the sensing element.

[0136] The electrostatic sensor may include a movable grounding element that can be configured to move between a grounding position in which the movable grounding element can be electrically coupled to a sensing element and a disconnection position in which the movable grounding element cannot be electrically coupled to the sensing element.

[0137] A non-transient computer-readable medium can be provided for predicting wafer jumps, the non-transient computer-readable medium storing instructions for obtaining predictors that predict whether a wafer will jump as a result of an increase in the distance between the wafer and a mechanical stage of a charged particle system, the predictors may be generated based on changes in the voltage of the wafer under different connection conditions between the wafer and the charged particle system, the changes may be caused by changing the distance between the wafer and the mechanical stage, the non-transient computer-readable medium storing instructions for monitoring the voltage of a region of the wafer by an electrostatic sensor which may include a sensing element, the monitoring is performed during a monitoring period in which the distance between the wafer and the mechanical stage may increase, and the monitoring results are provided, and the non-transient computer-readable medium also stores instructions for predicting whether a wafer will jump, the prediction may be based on the predictors and the monitoring results.

[0138] Any of the relationships described above can be learned in any way. For example, a reference structural element with a recess of known dimensions can be irradiated to provide measurement results associated with the known dimensions of the recess. Additionally or alternatively, the relationships may be learned by simulating electronic images obtained when scanning a structural element.

[0139] In the aforementioned specification, embodiments of the Disclosure have been described with reference to specific examples of embodiments of the Disclosure. However, it will be apparent that various modifications and changes can be made without departing from the broader intent and scope of embodiments of the Disclosure as described in the appended claims.

[0140] Furthermore, terms such as “front,” “rear,” “top,” “bottom,” “up,” and “down” in this specification and the claims are used for descriptive purposes, where applicable, and are not necessarily used to describe permanent relative positions. It should be understood that such terms are interchangeable under appropriate circumstances, so that embodiments of the disclosure described herein may operate in orientations other than those illustrated or otherwise described herein, for example.

[0141] The connections discussed herein may be any type of connection suitable for transferring signals between each node, unit, or device, for example, via an intermediate device. Therefore, unless implied or otherwise stated, connections may be, for example, direct or indirect. Connections may be illustrated or described with reference to being single, multiple, unidirectional, or bidirectional. However, different embodiments may modify the configuration of the connections. For example, separate unidirectional connections may be used instead of bidirectional connections, and vice versa. Also, multiple connections may be replaced by a single connection that transfers multiple signals sequentially or in a time-division multiplexing manner. Similarly, a single connection carrying multiple signals may be separated into various different connections carrying subsets of these signals. Thus, many options exist for transferring signals.

[0142] Any configuration of components for achieving the same function is effectively “associated” in such a way that the desired function is achieved. Therefore, any two components combined herein to achieve a particular functionality may be considered “associated” with each other, independently of the architecture or intermediate components, in such a way that the desired functionality is achieved. Similarly, any two such associated components may be seen as “operably connected” or “operably coupled” with each other in order to achieve the desired functionality.

[0143] Furthermore, those skilled in the art will recognize that the boundaries between the operations described above are merely illustrative. Multiple operations may be combined into a single operation, a single operation may be distributed among additional operations, and operations may be performed with at least partial overlap in time. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be modified in various other embodiments.

[0144] Furthermore, for example, in one embodiment, the illustrated example may be implemented as a circuit arranged on a single integrated circuit or within the same device. Alternatively, the example may be implemented as any number of separate integrated circuits or separate devices that are appropriately interconnected with one another.

[0145] However, other modifications, variations, and alternative forms are also possible. The specification and drawings should be considered accordingly in an illustrative rather than restrictive sense.

[0146] In the claims, no reference numerals placed between parentheses shall be construed as limiting the claims. The word “equipped with” shall not preclude the presence of other elements or steps other than those listed in the claims. Furthermore, as used herein, the terms “a” or “an” shall be defined as one or more. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims shall not be construed as meaning that the introduction of another claim element by the indefinite article “a” or “an” means that any particular claim containing such introduced claim element is limited to embodiments of the disclosure containing only one such element, even if the same claim contains the introductory phrase “one or more” or “at least one” and an indefinite article such as “a” or “an”. The same applies to the use of definite articles. Unless otherwise stated, terms such as “first” and “second” are used to arbitrarily distinguish between elements described by such terms. Therefore, these terms are not necessarily intended to indicate any temporal or other prioritization of such elements. The mere fact that certain means are described in different claims does not imply that combinations of these means cannot be used advantageously.

[0147] While some features of embodiments of this disclosure have been illustrated and described herein, many modifications, substitutions, alterations, and equivalents will be conceivable to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and alterations that fall within the true spirit of embodiments of this disclosure.

Claims

1. A method for evaluating contact between a wafer and an electrostatic chuck, The steps include: introducing a voltage difference between the absolute value of the negative electrode and the absolute value of the positive electrode of the electrostatic chuck while the wafer is supported by the electrostatic chuck and in contact with one or more conductive contact pins of the electrostatic chuck; A step of monitoring the charge at a measurement point located on the front surface of the wafer at different points in time after the introduction of the voltage difference using an electrostatic sensor including a sensing element, and providing the monitoring result, The steps include determining the electrical parameters of the contact between the wafer and the electrostatic chuck based on the monitoring results, Includes, A method wherein the electrostatic sensor further comprises a movable grounding element, the movable grounding element being configured to move between a grounding position in which the movable grounding element is electrically coupled to the sensing element and a disconnection position in which the movable grounding element is not electrically coupled to the sensing element.

2. The method according to claim 1, wherein the step of determining the electrical parameters includes the step of determining the resistance of the contact.

3. The method according to claim 2, wherein the step of determining the resistance of the contact includes approximating the charging pattern represented by the monitoring result to the discharge curve of a resistor-capacitor circuit.

4. The method according to claim 1, wherein the step of introducing the voltage difference includes a step of introducing the voltage difference at a rate of at least 1 volt every 1 millisecond.

5. The method according to claim 1, wherein the sensing element is a Kelvin probe, and the electrostatic sensor includes a mechanical unit for moving the Kelvin probe during the charge measurement.

6. The method according to claim 1, wherein the electrostatic sensor further comprises a conductive sealing element that seals the sensing element.

7. A device for evaluating contact between a wafer and an electrostatic chuck, Processing circuit and A static sensor including a sensing element, The electrostatic sensor is configured to monitor the charge at a measurement point located on the front surface of the wafer at different points in time after the introduction of a voltage difference between the absolute value of the negative electrode and the absolute value of the positive electrode of the electrostatic chuck, wherein the introduction is performed while the wafer is supported by the electrostatic chuck and in contact with one or more conductive contact pins of the electrostatic chuck. The processing circuit is configured to determine the electrical parameters of the contact between the wafer and the electrostatic chuck based on the results of monitoring the charge. The electrostatic sensor further comprises a movable grounding element, the movable grounding element being configured to move between a grounding position in which the movable grounding element is electrically coupled to the sensing element and a disconnection position in which the movable grounding element is not electrically coupled to the sensing element.

8. The device according to claim 7, wherein the processing circuit is configured to determine the electrical parameters of the contact by determining the resistance of the contact.

9. The device according to claim 8, wherein determining the resistance of the contacts involves approximating the charging pattern represented by the result of monitoring the charge to a discharge curve of a resistor-capacitor circuit.

10. The device according to claim 7, wherein the voltage difference is introduced at a rate of at least 1 volt every 1 millisecond.

11. The device according to claim 7, wherein the sensing element is a Kelvin probe, and the electrostatic sensor includes a mechanical unit for moving the Kelvin probe during the charge measurement.

12. The device according to claim 7, wherein the electrostatic sensor further comprises a conductive sealing element that seals the sensing element.

13. A non-transient computer-readable medium for evaluating contact between a wafer and an electrostatic chuck, While the wafer is supported by the electrostatic chuck and in contact with one or more conductive contact pins of the electrostatic chuck, a voltage difference is introduced between the absolute value of the negative electrode of the electrostatic chuck and the absolute value of the positive electrode of the electrostatic chuck. An electrostatic sensor including a sensing element monitors the charge at a measurement point located on the front surface of the wafer at different points in time after the introduction of the voltage difference, and provides the monitoring results. Based on the monitoring results, the electrical parameters of the contact between the wafer and the electrostatic chuck are determined. It stores the commands for that purpose, A non-transient computer-readable medium, wherein the electrostatic sensor further comprises a movable grounding element, the movable grounding element being configured to move between a grounding position in which the movable grounding element is electrically coupled to the sensing element and a disconnection position in which the movable grounding element is not electrically coupled to the sensing element.

14. A non-transient computer-readable medium according to claim 13, wherein determining the electrical parameters includes determining the resistance of the contact.

15. The non-transient computer-readable medium according to claim 14, wherein determining the resistance of the contact approximates the charging pattern represented by the monitoring result to the discharge curve of a resistor-capacitor circuit.

16. The non-transient computer-readable medium according to claim 13, wherein the sensing element is a Kelvin probe, and the electrostatic sensor comprises a mechanical unit for moving the Kelvin probe during the charge measurement.

17. The non-transient computer-readable medium according to claim 13, wherein the electrostatic sensor further comprises a conductive sealing element that seals the sensing element.

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