Techniques for detecting probe landing in integrated circuit test system

Abstract

Techniques for detecting probe landing in an integrated circuit test system. Systems, methods, and techniques for detecting contact between a probe tip and a sample surface. A method may include dithering a probe in a plane substantially parallel to a surface using a periodic motion having a dithering frequency. The method may include directing a charged particle beam toward a region of the probe. The method may include generating detector data describing periodic motion of the probe based at least in part on an interaction between the charged particle beam and the region of the probe. The method may include displacing the probe toward the surface. The method may also include detecting contact between the probe and the surface using the detector data.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application S / N 18 / 333,136, filed on June 12, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] Embodiments of the present disclosure relate to electronic test systems and algorithms and methods for their operation. In particular, some embodiments relate to techniques for integrated circuit testing. Background Art

[0004] Integrated circuit (IC) testing involves the measurement of individual transistors or groups of transistors of a semiconductor wafer or wafer portion (e.g., a sliced ​​wafer), referred to as a "device under test" or DUT. Typically, a probe is positioned in contact with an integrated circuit element and used to interrogate the DUT using a time-varying electrical signal. As the feature density and structural complexity of integrated circuits increase, placing a probe on a specific IC element involves precisely positioning a nanometer-scale probe tip and developing nanometer-scale information of the three-dimensional probe tip position. Such precise positioning is a significant challenge for an "open loop" positioning system, where the position of the probe tip is known to be within a tolerance range. The imprecise position of the probe tip makes it difficult to predict contact with a surface.

[0005] Precise positioning of probe tips on conductive contacts at nanometer scales corresponding to characteristic feature sizes of current CMOS nodes presents significant challenges. For example, the surface of a typical DUT includes many apparently similar features. For at least this reason, the profile of the probe, and in particular the probe tip, can be difficult to distinguish from the background. As a result, it is impractical to deploy open-loop positioning at the scale of deployed test platforms while using imaging-based contact detection methods. Therefore, there is a need for improved probe tip positioning and contact detection for IC test systems. Summary of the invention

[0006] Systems, methods and techniques for detecting contact between a probe tip and a sample surface. In one aspect, a method may include shaking a probe in a plane substantially parallel to a surface using a periodic motion having a shaking frequency. The method may include directing a charged particle beam toward an area of ​​the probe. The method may include generating detector data describing the periodic motion of the probe based at least in part on an interaction between the charged particle beam and the area of ​​the probe. The method may include displacing the probe toward the surface. The method may also include using the detector data to detect contact between the probe and the surface.

[0007] The method may also include determining an approximate location of the tip of the probe included in the region of the probe. Determining the approximate location of the tip of the probe may include generating an electronic image of the region of the probe and using the electronic image to determine the approximate location of the tip of the probe. Directing the beam may include scanning the charged particle beam in the form of a line over the region of the probe using line scanning. The mathematical product of the jitter frequency and the dwell time of the beam at a point in the line may be equal to or greater than one. The jitter frequency may be approximately equal to the resonant frequency of the probe.

[0008] The method may also include determining an approximate orientation of the probe and generating identifier information for the probe based at least in part on the orientation. The sample may include an integrated circuit having a contact pad, the contact being formed between the probe and the contact pad. Generating the detector data may include generating filtered data using a lock-in amplifier tuned to the dithering frequency. Detecting the contact may correspond to an attenuation of an output of the lock-in amplifier at the dithering frequency.

[0009] The method may also include dithering the probe at a set of motion frequencies, directing a charged particle beam toward the probe, generating detector data describing a response of the probe to the motion frequencies based at least in part on an interaction between the charged particle beam and the probe, estimating a resonant frequency of the probe using the detector data, and selecting the dithering frequency to be approximately equal to the resonant frequency. Directing the charged particle beam may include scanning the beam over the surface in a scanning pattern. Estimating the resonant frequency may include isolating the resonant frequency using a lock-in amplifier. The set of motion frequencies may include an element frequency of 100 kHz.

[0010] Detecting the contact may include determining a phase of a frequency component in the detector data, the frequency component being approximately at the dithering frequency. Detecting the contact may include aligning the phase of the frequency component with the phase of the drive signal of the periodic motion and detecting a change in the frequency component or a change in the phase of the frequency component.

[0011] The probe may be a first probe, the periodic motion may be a first periodic motion, the shaking frequency may be a first shaking frequency, and the system may further include a second probe. The method may further include shaking the second probe in a plane substantially parallel to the surface using a second periodic motion, the second periodic motion having a second shaking frequency approximately at a resonant frequency of the second probe. The method may further include directing a charged particle beam toward an area of ​​the second probe. The method may further include generating detector data describing the periodic motion of the second probe based at least in part on an interaction between the charged particle beam and the area of ​​the probe. The method may further include displacing the second probe toward the surface. The method may further include detecting contact between the second probe and the surface using the detector data. The first shaking frequency and the second shaking frequency may be different.

[0012] In one aspect, one or more non-transitory machine-readable storage media storing instructions that, when executed by a machine, cause the machine to perform the operations of the methods of the aforementioned aspects.

[0013] In one aspect, a system for testing integrated circuit components includes a probe, a charged particle beam system, a detector, a control circuit, and one or more non-transitory machine-readable storage media storing instructions, the detector being oriented toward the probe and configured to detect particles generated by the interaction of the charged particles and the probe, the control circuit being operably coupled to the probe, the charged particle beam system, and the detector and being configured to actuate the probe, the instructions when executed by the system causing the system to perform the operations of the foregoing aspects of the method and medium. The charged particle beam system can be a scanning electron microscope body, and wherein the detector is a secondary electron detector or a backscattered electron detector.

[0014] Embodiments of the present disclosure also include systems, components and methods according to the aforementioned aspects. The terms and expressions that have been adopted are used as descriptive terms rather than restrictive terms, and when using such terms and expressions, it is not intended to exclude any equivalents of the features shown and described or parts thereof, but it should be recognized that various modifications are possible within the scope of the claimed subject matter. Therefore, it should be understood that although the subject matter claimed by the present disclosure has been specifically disclosed through embodiments and optional features, those skilled in the art may modify and change the concepts disclosed herein, and such modifications and changes are considered to be within the scope of the present disclosure as defined by the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The foregoing aspects of the present disclosure and many of the attendant advantages will become more readily appreciated when the following detailed description is taken in conjunction with the accompanying drawings.

[0016] Figure 1 is a schematic diagram illustrating an exemplary integrated circuit testing system according to some embodiments of the present disclosure.

[0017] Figure 2 is a schematic diagram illustrating a plan view of an exemplary integrated circuit test probe according to some embodiments of the present disclosure.

[0018] Figure 3 is a schematic diagram illustrating a side view of an exemplary integrated circuit test probe according to some embodiments of the present disclosure.

[0019] Figure 4 is a schematic diagram illustrating an exemplary integrated circuit testing system including a plurality of probes according to some embodiments of the present disclosure.

[0020] Figure 5is a flow chart illustrating an exemplary process for detecting contact between a probe tip and a surface according to some embodiments of the present disclosure.

[0021] Fig. 6A is a composite image showing an exemplary SEM image of an integrated circuit test system on a DUT surface according to some embodiments of the present disclosure.

[0022] Figure 6B is a composite of exemplary SEM images showing an integrated circuit test system in contact with a DUT surface according to some embodiments of the present disclosure.

[0023] Figure 6C is a composite diagram showing an exemplary lock-in amplifier output image of an integrated circuit test system on a DUT surface according to some embodiments of the present disclosure.

[0024] Fig.6D is a graph illustrating an exemplary lock-in amplifier output spectrum of an integrated circuit test system on a DUT surface according to some embodiments of the present disclosure.

[0025] Fig. 6E is a composite diagram showing an exemplary lock-in amplifier output image of an integrated circuit test system in contact with a DUT surface according to some embodiments of the present disclosure.

[0026] Fig. 6F is a graph illustrating an exemplary lock-in amplifier output spectrum of an integrated circuit test system in contact with a DUT surface according to some embodiments of the present disclosure.

[0027] In the drawings, unless otherwise specified, the same reference numerals represent the same components in various views. Where appropriate, not all instances of components need to be labeled to reduce clutter in the drawings. The drawings are not necessarily drawn to scale, with emphasis instead on illustrating the principles being described. DETAILED DESCRIPTION

[0028] Although illustrative embodiments have been illustrated and described, it should be understood that various changes may be made therein without departing from the spirit and scope of the present disclosure. In the following paragraphs, embodiments of analytical instrument systems, components, and methods for detecting tip positions and for detecting contact between probe tips and surfaces are described. To simplify the description, embodiments of the present disclosure focus on integrated circuit characterization and fault analysis. Embodiments are not limited to such instruments, but are intended to be configured for localization and positioning of nano-scale electromechanical components. In illustrative examples, nano-scale composite materials (e.g., quantum dots, MEMS devices, or other nanostructured materials) may benefit from improved positioning of nano-scale electromechanical components that would otherwise be difficult to position with appropriate accuracy.

[0029] Embodiments of the present disclosure include systems, methods, algorithms, and non-transitory media storing machine-readable instructions for locating and detecting contact between a probe tip and a sample surface. Technical advantages of the present disclosure include improved detection of contact between a nanoscale probe tip and a surface without detailed information about the location of the sample surface, and improved performance of an integrated circuit evaluation platform.

[0030] Integrated circuit testing involves the measurement of individual transistors or groups of transistors of a semiconductor wafer or wafer portion (e.g., a sliced ​​wafer), referred to as a "device under test" or DUT. Typically, probes are positioned in contact with integrated circuit elements and are used to interrogate the DUT using periodic, non-periodic, and / or direct current electrical signals. One or more probes are used as inputs, and one or more probes are used as outputs to measure the response of the IC element to the signal. As the feature density and structural complexity of integrated circuits increase, placing a probe on a specific IC element involves nanoscale geometry of the probe tip and nanoscale information of the probe tip position. Such precise positioning is a significant challenge for "closed-loop" positioning systems (e.g., registered piezoelectric actuators). Although technically possible, precise positioning of the probe tip on a conductive contact at the nanoscale corresponding to the characteristic feature size of the current CMOS node can increase the complexity of the control system to a level that is not practical at the level of a deployed test platform. For example, based at least in part on the uncertainty of the sample topography and sample height measurement, a closed-loop fine control system can still rely on a feedback mechanism using the technology of the present disclosure.

[0031] In lieu of a complex closed-loop system, embodiments of the present disclosure exploit the availability of electromechanical systems (e.g., arbitrary waveform generators, piezoelectric actuators, etc.) to induce motion of the probe that is attenuated or removed upon contact with the sample surface. Relative to the prior art, embodiments of the present disclosure improve such detection based at least in part on isolating motion at or near a characteristic frequency of the probe motion, thereby revealing the effects of contact with the surface on the probe. As an illustrative example, contact between the probe tip and a surface can be detected at least in part by an image of the probe for which the frequency domain content has been filtered to isolate the periodic motion of the probe. Filtering in this manner can remove vibrations at other frequencies and remove background (e.g., substantially stationary) information, which can be used to generate an image that isolates individual probes in a field of view that includes multiple probes. Upon contact, the periodic motion of the probe stops, causing the probe to disappear from the image. As shown in reference Figure 1 -6 As described in more detail, embodiments of the present disclosure allow a probe tip to be precisely positioned and lowered onto a nanoscale integrated circuit feature without requiring detailed knowledge of the exact location of the surface of the IC or the geometry of the probe.

[0032] Figure 1 1 is a schematic diagram illustrating an exemplary integrated circuit (IC) test system 100 according to some embodiments of the present disclosure. The exemplary system 100 includes an instrument 105, an instrument computing device (IPC) 110, and a client computing device 115 operably coupled to each other via one or more networks 120. The exemplary system 100 is configured to interrogate an IC device, referred to as a device under test (DUT) 125, using a probe assembly 130 that is electrically coupled to components of the DUT 125 via a controller (also referred to as a test fixture). By applying time-varying electronic signals to components of the DUT 125 (referred to as a "test loop"), performance characteristics of circuit components of the DUT 125 can be derived as part of a quality control and failure analysis technique for ICs manufactured according to a given IC design.

[0033] The instrument 105 includes a test portion 135 in which a probe assembly 130 is disposed, including a DUT 125 and electronic components for driving a test circuit (e.g., a test device), a vacuum component for isolating the DUT 125 from the atmosphere, and a thermal management system for removing heat from the DUT 125 during testing. Coupled with the test portion 135 is a charged particle column 140 and a vacuum chamber 145. The charged particle column 140 can be an ion beam (e.g., a focused ion beam (FIB)) column or an electron beam column. In some embodiments, the instrument 105 includes a FIB column and an electron beam column, wherein one of the charged particle sources is coupled to the vacuum chamber at an angle relative to the charged particle column.

[0034] The electron beam column can generate an electron beam 147 and focus the electron beam 147 onto the DUT 125. The interaction of the electron beam 147 with the DUT 125 generates one or more detectable signals that can be received by one or more detectors 150 operably coupled to the vacuum chamber 145 and configured to generate detector data based at least in part on the measurement of the signals. In an illustrative example, the detector 150 can include a secondary electron detector, a backscattered electron detector, a photon detector, an imaging sensor (e.g., a CCD), etc. In another example, the probe can blur a bright spot on the surface of the DUT 125 so that a signal can be generated from the probe periodically revealing the bright spot and periodically blocking the beam 147 from reaching the surface. Compared to a typical scanning electron microscope (SEM), the vacuum chamber 145 can omit sample manipulation tools, such as interlocks, sample stages, etc., at least in part because the DUT 125 can be removably coupled to a probe assembly 130, which can be disposed on a stage, bracket, or other holding assembly that provides electronic and thermal coupling to the test portion (e.g., coupling to a test device). The electron beam 147 can be directed toward the DUT 125 using a variety of operating modes, including but not limited to imaging modes, line scan modes, and spot modes, as described in reference to FIG. Figure 2 -6 described in more detail.

[0035] The probe assembly 130 may include an individually addressable probe 155 that can be moved in three spatial dimensions (labeled by the "xyz" Cartesian axes) by an electromechanical actuator 160. In this manner, the probe tip (reference Figure 2-4 The probe assembly 130 is electrically coupled to components of the test portion 135 via couplings 165 and 170, whereby the actuator 160 can be driven (e.g., using a drive signal) and an output signal can be generated.

[0036] Based at least in part on challenges associated with calibrating a reference position of the surface of the DUT 125 (e.g., defining z=0 as the surface of the DUT 125), the vertical displacement of the probe 155 may be measured with reference to a calibration displacement (e.g., a return or “0” displacement) that is independent of the type and location of the DUT 125. To this end, the exemplary system 100 may implement open-loop positioning of the probe 155 with reference to a method by which the position of the probe 155 is known relative to the calibration displacement, adjusted by any subsequent displacements (e.g., a starting point in three-dimensional coordinates, where each subsequent displacement is a vector addition of three displacement values). In some cases, the lateral (e.g., “xy”) position of the probe 155 relative to the surface of the DUT 125 may be determined using detector data (e.g., a secondary electron image) generated by directing the electron beam 147 to a region of the DUT 125 or to one or more of the probes 155.

[0037] The computing devices 110 and 115 may be general purpose machines (e.g., laptops, tablet computers, smart phones, servers, etc.) configured to operate or otherwise interact with the instrument 105. The instrument 105 may in turn include electronic components that form part of a dedicated computing device, including control circuits configured to drive the test loop, actuate the probe assembly 130, control the electron beam column 140, and operate the vacuum system and thermal management system. The IPC 110 may be a machine provided with software that is configured to interface with the instrument 105 and allow a user of the instrument 105 to perform testing of the DUT 125. Similarly, the client pc 115 may be configured to control one or more systems of the instrument 105 (e.g., via the IPC 110 and / or by interfacing with the instrument 105 via the network 120) to perform testing of the DUT 125. In some embodiments, the instrument 105, IPC 110, and / or client PC 115 are in separate physical locations and are coupled via a network 120 and / or by other means, such as a direct connection or by a wireless connection (e.g., near-field radio). The network 120 may include a public network (e.g., the Internet) and / or a private network (e.g., an intranet or a local area network). In some embodiments, the IPC 110 and / or client PC 115 are configured to operate the instrument autonomously (e.g., without human intervention) or semi-autonomously (e.g., with limited human intervention, such as initiating a test, identifying a sample, and / or confirming an automated analysis result). In this manner, the exemplary system 100 may be configured to operate autonomously with manual control and / or autonomously as part of a scalable IC characterization system for automated testing of ICs.

[0038] Figure 2 2 is a schematic diagram showing a plan view of an exemplary integrated circuit test probe 200 according to some embodiments of the present disclosure. The probe 200 is Figure 1 The probe 200 includes a probe arm 205 and a probe tip 210. The probe 200 also includes an electromechanical actuator 215 (e.g., Figure 1 The probe 200 may be operably coupled to a control circuit 220 (eg, via Figure 1 The coupling 165 and 170), as shown in reference Figure 1 as described.

[0039] The probe arm 205 and the probe tip 210 may be made of wire that has been shaped and sharpened to a point. Figure 1 and Figure 3As shown, the probe tip 210 can be oriented at an angle relative to the probe arm 205 so that the tip 210 contacts the surface 225 of the DUT 125 in the target area 230. The probe tip 210 can taper to a terminal surface having a feature size on the same order as one or more features 235 of the DUT 125 (e.g., approximately 1-100 nm). The features 235 can be conductive and electrically coupled to one or more IC components (e.g., transistors, diodes, etc.). For example, the features 235 can include conductive contact pads formed in one or more layers of the IC that can be used to mechanically and / or electrically couple the probe 205 to the IC components.

[0040] The probe tip 210 may be brought into contact with the surface 225 at the feature 235, thereby electrically coupling the control circuit 220 with the DUT 125. This coupling may allow the probe 200 to apply at least a portion of a test signal to the DUT 125 through the feature 235. In some embodiments, multiple probes 200 are brought into contact with multiple corresponding features 235 on the surface 225 and deployed simultaneously to apply a test signal and measure an output signal. Figure 4 An exemplary configuration having multiple probes 200 is described.

[0041] The control circuit 220 can drive the actuator 215 in one or more directions, for example, by encoding the motion of the probe 200 as a vector of displacement values. The motion can include a component of linear motion (e.g., linear displacement in one or more directions) and / or a component of periodic motion to cause the probe 200 to tremble. In this case, the "trembling" motion refers to the periodic motion of the probe arm 205 and / or the probe tip 210 characterized by a frequency and an amplitude, where the amplitude, measured as the displacement of the probe tip 210 in a given dimension, can be of the order of magnitude of the size of the feature 235, larger or smaller.

[0042] Using an open-loop positioning system, the displacement vector can be used to track the position of the probe tip 210 within a tolerance of approximately 10%. In this manner, determining whether contact has been made between the probe tip 210 and the surface 225 may be prone to error. Similarly, lifting the probe tip 210 from the surface (e.g., breaking contact) may be prone to error. Moving the probe tip 210 from one feature 235 to another feature 235 while the probe tip 210 is in contact with the surface 225 may damage the DUT 125 and / or the probe tip 210. As the feature 235 size continues to shrink to the 1-10 nm level, additional and / or alternative contact detection techniques are needed. Advantageously, the techniques described herein allow detection of contact between the probe tip and the surface independent of the position of the probe tip 210 on the surface (e.g., no electrical contact with a precise point is required).

[0043] As part of detecting contact between the probe tip 210 and the surface 225, the technology of the present disclosure may include shaking the probe arm 205 and the probe tip 210. In the context of the present disclosure, the term "shake" is used to refer to periodic and / or oscillatory motion, or shaking motion 240. In an illustrative example, the shaking motion 240 can be generated by applying a drive signal to the electromechanical actuator 215. The drive signal can be a sinusoidal or other periodic signal with a frequency and phase called a shaking frequency. The shaking motion 240 can be substantially transverse to the orientation of the probe arm 205 (e.g., lateral motion) or substantially aligned with the orientation of the probe arm 205 (e.g., longitudinal motion). As part of increasing the detectability of the shaking motion 240, the probe 200 can be shaken in a plane substantially parallel to the surface 225 of the DUT 125 and / or in a direction substantially orthogonal to the charged particle beam 147.

[0044] Advantageously, the lateral motion may stimulate the resonant and / or harmonic vibration modes of the probe arm to enhance the amplitude of the shaking motion 240. To this end, the shaking frequency may be approximately the resonant frequency of the probe 200. In general, the resonant frequency of the cantilever under lateral motion is expressed as:

[0045]

[0046] where k n is a constant specific to the resonant mode, E is Young's modulus, I is the moment of inertia, w is the width of the probe arm 205, and L is the length of the probe arm 205. As will be appreciated by one of ordinary skill in the relevant art, E, I, w, and L are parameters specific to the materials and geometry of the probe arm 205 and the probe tip 210. The resonant properties are sensitive to the value of each parameter, such that relatively small deviations of the estimated value of the probe 200 from the actual value can reduce or eliminate resonant motion in the probe 200.

[0047] To this end, the technology of the present disclosure includes determining the resonant frequency of the probe 200. Determining the resonant frequency of the probe 200 may include shaking the probe 200 on a set of motion frequencies. In some cases, the set of motion frequencies may be determined based at least in part on an estimate determined using the above expression. In some cases, the response of the probe 200 to the scanning of the motion frequencies may be measured using a charged particle microscope. For example, a charged particle beam may be directed toward the probe 200 (e.g., the probe arm 205 and / or the probe tip 210). In the case of a SEM, the detector data may include secondary electron images, backscattered electron images, line scan signals, current absorbed by the probe 200 from the beam, and / or intensity data as a function of time. The detector data may be filtered by frequency to isolate the frequency component corresponding to a given motion frequency. In this way, the detector data may describe the response of the probe 200 to the motion frequency based at least in part on the interaction between the charged particle beam and the probe 200. Determining the response of the probe 200 to each motion frequency in the set of motion frequencies may allow the resonant frequency of the probe 200 to be estimated from the detector data. The shaking frequency can be selected to be approximately equal to the resonant frequency. In some embodiments, the shaking frequency can be a fraction or multiple of the resonant frequency. For example, the shaking frequency can be selected to stimulate a harmonic vibration mode of the probe 200, rather than the first resonant mode (n=1 in the above expression). Similarly, the shaking frequency can be selected to be different from the resonant frequency, for example based at least in part on the performance constraints of the electromechanical actuator 215. In the case where the shaking motion 240 causes a detectable signal in the detector data, contact can be detected without stimulating the resonant mode of the probe 200.

[0048] In some embodiments, a charged particle beam can be scanned over an area of ​​the probe 200 (e.g., the probe arm 205 and / or the probe tip 210) using a line scan 245. A line scan can be a scanning pattern defined by a vector connecting two ends that traverse the area of ​​the probe 200. The beam can be repeatedly scanned over the probe such that the line scan 245 is characterized by a cycle time. The cycle time (excluding the time between consecutive line scans 245) can include the average dwell time of the beam at a given point on the surface 225. The dwell time can be determined based at least in part on a jitter frequency such that the frequency content for the jitter motion 240 is captured by the beam. In some embodiments, the jitter frequency (having a frequency of seconds) can be determined based at least in part on a jitter frequency. -1The mathematical product of the dwell time of the beam at a point in the line scan 245 (e.g., the dwell time of the beam at a point on the probe surface) (having units of seconds) is equal to or greater than one (a unitless value). In some embodiments, the point in the line scan 245 may coincide with a feature of the probe 200 or the surface 225 of the DUT 125. In an illustrative example, for a jitter frequency of about 100 kHz, the dwell time may be about 10 microseconds or more. With respect to the frequency range, above a jitter frequency of about 10 MHz, problems arise from electromagnetic effects, such as coupling (e.g., Figure 1 The invention relates to the method of measuring the position of the probe 245. The method of measuring the position of the probe 245 is carried out by the user to reduce the loss caused by the conductance and / or impedance in the coupling 170) and the electromechanical wear of the actuator (e.g., actuator 215). In contrast, below a dithering frequency of about 50 kHz, the acquisition time of each probe position may reduce the throughput and make the probing technique impractical on a large scale. In some cases, the cycle time of the line scan 245 is about 20 milliseconds to about 50 milliseconds, corresponding to a spot size of about 1.2 nm-50 nm, including subranges, fractions, and interpolations thereof.

[0049] Figure 3 is a diagram showing some embodiments according to the present disclosure Figure 2 Schematic diagram of a side view of an exemplary integrated circuit test probe 200 . Figure 3 As shown in reference Figure 2 The probe arm 205, probe tip 210, actuator 215, control circuit 220, surface 225 of DUT 125, and a system including an imaging system 305 (e.g., an electron microscope, a focused ion beam source, and / or an optical microscope), a vacuum chamber 310 (e.g., Figure 1 145 ) and other components of one or more sensors 315 operably coupled to the probe 200 .

[0050] exist Figure 3 , surface 225 is shown as recessed into DUT 125 to reflect that feature 235 is generally formed inside DUT 125 and is revealed by selectively removing material from DUT 125 (e.g., by ion beam milling or other etching processes). Probe tip 210 is shown at a displacement 320 from surface 225. In some embodiments, an exemplary process of the present disclosure includes dithering probe tip 210 and directing an electron beam at at least a portion of probe tip 210, as described with reference to FIG. Figure 2As described, the probe tip 210 is displaced toward the surface 225 while being displaced. The control circuit 220 may include one or more electronic signal filters and other components to process the signals generated by the detector 150. For example, the filters may include one or more lock-in amplifiers, bandpass filters, low-pass and / or high-pass filters, etc., which are configured to isolate frequency components of the detector data attributable to the dithering motion 240. As the displacement 320 decreases as the probe tip 210 approaches the surface 225, the response signal generated as an output of the detector 150 and / or the filter may be stored, processed, and / or used by the control circuit 220 to detect contact of the probe tip 210 with the surface 225. In the example of a lock-in amplifier, the control circuit may be configured (e.g., provided with analog and / or digital components) to generate a plurality of displacement signals in a scanning mode (e.g., Figure 2 The time series of intensity values ​​generated by detector 150 during a line scan 245) is transformed into frequency space and filtered. In some cases, the deviation may be greater than 0.1%, greater than 0.5%, greater than 1%, greater than 2%, greater than 3%, greater than 4%, greater than 5%, greater than 10%, or greater than 25%, including fractions and interpolations thereof.

[0051] The charged particle beam 147 can be directed toward a region of the probe 200 that may include the probe tip 210 as a method for detecting the region of the probe 200 having the largest amplitude of the shaking motion 240. In addition to and / or in lieu of the line scan and imaging modes, the charged particle beam 147 can be focused in a spot mode onto the edge of the probe arm 205 or the probe tip 210. The amplitude of the shaking motion 240 and the relative size of the beam spot and the probe width (e.g., at or near the probe tip 210) can cause a region of the probe to traverse the charged particle beam 147 twice during each cycle of the shaking motion 240. In this way, the frequency of interest for filtering can be approximately twice the shaking frequency. Advantageously, the relatively high sampling frequency can enhance the separation of the characteristic signal of the shaking motion 240 from other periodic noise sources (e.g., out-of-band acoustic and / or vibration noise, EMI, etc.), such as those attributable to electromagnetic interference from vacuum components (e.g., turbo pump rotation), DUT test signals, line frequencies, etc. Additionally and / or alternatively, the charged particle beam 147 can be defocused to a size that is of the same order of magnitude as the probe tip size (e.g., a characteristic size of about 10-100 nm). In this manner, the motion of the probe can be captured in the detector data while also reducing exposure of the DUT surface 125 to charged particles (e.g., reducing the flux of charged particles in terms of particles per unit area). Advantageously, this approach allows detection of contacts with reduced or eliminated beam-induced contamination or damage.

[0052] Figure 4is a schematic diagram illustrating an exemplary integrated circuit testing system 400 including a plurality of probes according to some embodiments of the present disclosure. Figure 4 The probe is Figure 1-3 1 and 2. The system 400 shows ten individual probes, each of which contacts a corresponding feature 235. For example, a first probe tip 210-1 can contact a first feature 235-1 and a second probe tip 210-2 can contact a second feature 235-2. The disclosed system can accommodate multiple probes, each of which individually employs the techniques described herein to detect proximity and / or contact with a surface of a DUT. Probe assemblies (e.g., Figure 1 The probe assembly 130) can accommodate 1-12 probes, including their sub-ranges and interpolations.

[0053] In some embodiments, each probe 200 is driven at a corresponding shaking frequency to cause a corresponding shaking motion 240. For example, the first probe can be driven using a first shaking motion 240-1 at a first shaking frequency, the second probe can be driven using a second shaking motion 240-2 at a second shaking frequency, and the third probe can be driven using a third shaking motion 240-3 at a third shaking frequency. The shaking frequencies can be the same or different. In the case where the filtering method can resolve different frequencies within the tolerance of the resonant response of the probe 200, the corresponding shaking frequencies can be distinguishable and resonant. In some cases, the first shaking frequency can be approximately equal to the first resonant mode, the second shaking frequency can be approximately equal to the second resonant mode, and so on. In some cases, the shaking frequencies can be fractions or multiples of each other. In some cases, the shaking frequencies can be reduced by reducing the amount of vibration caused by the probe assembly (for example, Figure 1 The jitter frequency is determined in a manner that causes crosstalk caused by vibration transmission of the probe assembly 130 of the probe assembly 130. In the illustrative example, the corresponding jitter frequency can be selected to have irregular intervals that interfere in a manner that vibrations do not propagate between the probes.

[0054] Advantageously, applying different jitter frequencies to corresponding probes can allow a single scan pattern 405 to distinguish between probes in a common set of detector data based on frequency. For example, by filtering the frequency components of the detector data to isolate the different corresponding jitter frequencies, contact of each corresponding probe with the surface of the DUT can be detected in parallel. In contrast, for a single jitter frequency, the scan pattern 405 can be tagged with position information that can be cross-referenced to identify a given probe. This approach may be limited by signal quality because the change in signal strength when a single probe makes contact may be relatively small relative to the signals generated by the remaining probes. Similarly, the temporal resolution of the data may limit the ability to distinguish between probes that are in contact with the surface of the DUT within a given time period. As shown in reference Figure 2 and Figure 5 Described in more detail, the scan pattern is shown as a substantially circular scan, but may also be or include one or more linear segments, which may be continuous (eg, a polygon) or discontinuous (eg, a set of linear segments).

[0055] In some embodiments, the beam may be defocused to extend over the surface of the DUT 125, thereby capturing motion information of multiple probes in the detector data. In this way, the detector data may include frequency domain information for each of the corresponding jitter frequencies, such that when the probes contact the surface of the DUT, the frequency domain information of the probes is eliminated from the detector data. Advantageously, this approach protects the surface by reducing area-specific exposure of the surface to charged particles (e.g., for a given fluence, the flux is lower when the beam is defocused over a larger portion of the surface), while also allowing multiple probes to be monitored by associating each of the probes with a corresponding jitter frequency identifiable from the detector data without individually locating the probes.

[0056] Figure 5 is a flow chart illustrating an exemplary process 500 for detecting contact between a probe tip and a surface according to some embodiments of the present disclosure. One or more operations of the exemplary process 500 may be performed by a computer system in communication with additional systems, including but not limited to a characterization system, a network infrastructure, a database, and a user interface device. In some embodiments, reference Figure 5 At least a subset of the described operations are automatically performed (e.g., without human involvement) or pseudo-automatically performed (e.g., initiated by a human or with limited human intervention). In an illustrative example, operations for positioning a probe tip, shifting a probe tip, jittering a probe, and generating detector data can be automatically performed, wherein the system 100 is configured to generate visualization data that displays one or more response signals for interpretation by a human user (an example shown in FIG. 6 ). Although the exemplary process 500 is described as a sequence of operations, it should be understood that at least some of these operations may be omitted, repeated, and / or reordered. In some embodiments, additional operations are performed before and / or after the operations of the exemplary process 500, which are omitted for clarity of explanation, such as operations for calibrating an electron source, alignment and aberration correction of an electron beam, initializing a probe position, and the like.

[0057] At operation 505, the exemplary process 500 includes jittering a probe (eg, Figure 2 Dithering the probe may include generating a motion at least partially transverse to the orientation of the probe (e.g., Figure 2 and Figure 4 The shaking motion 240). As shown in reference Figure 2As described in more detail, the shaking motion may include a periodic component characterized by a shaking frequency. The shaking motion may be performed by moving an electromechanical actuator (e.g., Figure 1 The periodic drive signal is applied to the actuator 160 to generate the shaking motion. In some embodiments, the probe includes one or more actuators for generating the shaking motion, which are different from the electromechanical actuator used to move the probe. For example, the actuator used for shaking can be designed to resonate at about the shaking frequency, so that the energy used to drive the shaking motion can be relatively low compared to the energy used to drive the electromechanical actuator used to position the probe.

[0058] In some embodiments, operation 505 includes shaking multiple probes simultaneously. Figure 4 As described in more detail, the probes may be jittered at corresponding jitter frequencies or phases as a method of distinguishing different probes. To this end, operation 505 may include jittering a first probe / probe tip (e.g., first probe tip 210-1) at a first jitter frequency and jittering a second probe / probe tip (e.g., second probe tip 210-2) at a second jitter frequency that may be different from the first jitter frequency. Similarly, for any number of probes (e.g., 4, 6, 8, 10, 12 probes, or more), each probe may be vibrated at a corresponding frequency. For a discussion of jitter frequencies, refer to Figure 2-4 . With the detector signal processor synchronized with the beam scanning pattern, multiple probes can be driven at substantially the same jitter frequency so that the probes can use the same resonant or near-resonant jitter frequency that is phase-shifted relative to another probe using the resonant or near-resonant jitter frequency. Detecting the phase of the probe jitter motion allows for distinguishing multiple probes and detecting contact of a given probe with the surface of the DUT. For example, detecting the contact can include determining the phase of the probe as captured in the detector data, locking the phase of an appropriate frequency component at about the jitter frequency in the detector data to the phase of the drive signal, and detecting changes in the amplitude and / or phase of the frequency component relative to the drive signal when the probe approaches and / or contacts the DUT surface.

[0059] At operation 510, exemplary process 500 includes directing a charged particle beam (eg, Figure 1 of electron beam 147). As shown in reference Figure 1-3Described in more detail, the charged particle beam can be an electron and / or ion beam. In the imaging mode, the beam can be directed to multiple probes and DUTs using a grating pattern so that the frame rate in the imaging mode will be compatible with the jittering motion of the sampling probe. For example, the frame rate can be greater than about half of the jittering frequency to allow the jittering motion of the probe to be detectable in the image sequence of the probe. In another example, an image can be generated by integrating the time information at each of a set of grating positions within a time period. In this way, detector data is generated for multiple points at each of the set of grating positions without applying an edge detection algorithm, and is used to generate an image of the probe profile. In an illustrative example, the probe can be jittered at about 91kHz, and the electron beam is used to sample the jittering motion of the probe at a sampling frequency of 1MHz for 100 data points, corresponding to a dwell time of 100 microseconds at each position. The detector data at each position can be used for processing (e.g., by transforming to the frequency domain and filtering) to isolate the 91kHz mode. The amplitude of the 91 kHz pattern can be used as an intensity value for each pixel in an image that reproduces at least a portion of the periphery of the probe tip.

[0060] In some embodiments, directing the charged particle beam includes scanning the beam over the surface of the DUT in a scanning mode. Figure 4 Described in more detail, the rotational pattern may correspond to a circular motion, a polygonal motion, etc., such that the beam traverses one or more probes as one or more line scans. Figure 4 In the illustrative example of , the beam traverses ten probes (e.g., Figure 4 The scanning pattern corresponds to a polygon having a number of sides equal to the number of probes for which the exemplary process 500 is to be performed. Figure 4 Ten probes are included, but the system of the present disclosure may include more or fewer probes, such as 4 probes, 6 probes, 8 probes, 12 probes, etc., including interpolations thereof. In another example, the scanning pattern may include multiple discontinuous line scans (e.g., Figure 2 The scanning pattern may include a plurality of line scans 245, each of which is oriented to cause the beam to pass through a corresponding probe area. In some cases, each line scan of the scanning pattern may be substantially orthogonal to a corresponding probe. Advantageously, using a scanning pattern including a plurality of discontinuous line scans may reduce the total electron flux incident on the surface of the DUT, thereby limiting degradation of the surface features 235 (e.g., conductive contact pads of an IC, dielectric regions, etc.) caused by beam-induced contamination.

[0061] As reference Figure 2-3As described in more detail, the beam can be focused onto an area of ​​the probe and used in a line scan mode and / or a spot mode. In this manner, the motion of the probe can be detected and used to identify the transition from free vibration to anchored vibration. The area of ​​the probe may include the probe tip. Advantageously, directing the beam toward the probe tip may improve the probe's contact with the surface (e.g., Figure 2 Detection of contact with the surface 225 of the DUT 125). To this end, the exemplary process 500 may include determining the approximate position of the tip of the probe. Determining the approximate position of the tip of the probe may include generating one or more electronic images of the probe and determining the approximate position of the tip of the probe using the electronic images. Determining the approximate position of the tip of the probe may include an automated and / or pseudo-automated geometric fitting method applied to an image and / or contour of the probe in the filtered frequency data. For example, the position of the probe tip may be approximated by fitting a line segment to each edge of the tapered portion of the probe, such that the convergence point of the line segments represents the position of the probe tip. In some embodiments, the position of the probe tip may be approximated by repeating a line scan at two or more locations in the tapered region of the probe. The probe tip may be located using an estimate of the probe width at each line scan and an estimate of the distance between line scans. In some cases, the edge of the probe may be identified in the line scan, which may be used to identify the leading and trailing edges of the probe, as described in reference to FIG. Fig.6D Described in more detail.

[0062] At operation 515, the exemplary process 500 includes generating detector data. Figure 2-3 and in Figures 6A-6F As described in more detail in the examples of , the detector data may include one or more modalities describing the interaction of the charged particle beam with the probe region. For example, the detector data may include a sequence of images generated using a secondary electron detector or a backscattered electron detector. In another example, the detector data may include a vector of intensity values ​​(proportional to the flux of charged particles incident on the detector surface) and corresponding position values ​​(e.g., referenced to a starting point). In point mode, the detector data may include a time series vector of intensity values, where each element of the vector consists of a vector corresponding to a detector (e.g., Figure 1 The time step separation of the sampling frequency of the detector 150).

[0063] Operation 515 may include generating filtered data to isolate one or more frequency components of the charged particle detector. For example, the output signal from the detector may be detected using a lock-in amplifier (e.g., as a Figure 2-3The detector data may be filtered using a bandpass filter configured to isolate the jitter frequencies, and / or using other filtering techniques suitable for selectively removing periodic components of the detector signal attributable to sources other than the jittering motion of the probe. To this end, the intensity values ​​in the detector data may be transformed into frequency space (e.g., using a Fourier transform, a fast Fourier transform, etc.) to facilitate filtering by frequency. In this way, the detector data may include a sequence of frequency-space intensity data for a set of time points, such that the intensity data may be represented as a function of frequency and time.

[0064] At operation 520, the exemplary process 500 includes displacing the probe toward the surface. Displacing the probe tip may include engaging one or more individually addressable actuators (e.g., Figure 1 Electromechanical actuator 160). In this manner, operation 510 may include engaging one or more actuators so that a vector describing the displacement of the probe tip is non-zero in a dimension substantially perpendicular to the sample surface and approximately equal to zero in the other dimensions. In the example of a three-coordinate displacement vector, operation 510 may include applying the vector (X, Y, Z) = (0, 0, z), where "z" is a non-zero number. In some embodiments, the xy coordinates (or their equivalent) are determined with reference to an image of the sample surface.

[0065] Operation 520 may include applying one or more displacement rates to the z-motion of the probe tip. For example, a first "coarse" motion rate may be greater than a second "fine" motion rate. In some embodiments, operation 510 includes applying one or more displacement rates to the z-motion of the probe tip. Figure 3 The displacement rate in the z-axis is reduced from a "coarse" rate to a "fine" rate when the displacement 320) is from about 100 nm to about 1000 nm (including subranges, fractions, and interpolations thereof). With a tolerance of about 10% in displacement, reducing the displacement rate at the threshold distance can reduce the risk of damage to the probe and / or sample surface caused by unintended contact.

[0066] At operation 525, the exemplary process 500 includes detecting contact of the probe tip with the surface of the DUT. Figures 6A-6F Described in more detail, detecting the contact may include one or more methods using the detector data generated at operation 515. For example, where generating the detector data includes generating filtered data using a lock-in amplifier tuned to a dither frequency, detecting the contact may correspond to an attenuation of the output of the lock-in amplifier at the dither frequency. In some cases, detecting the contact may include comparing the value of the lock-in output to a threshold at which the probe tip is considered to be in contact with the surface of the DUT.

[0067] Example 1: The probe tip lands on the device surface

[0068] Figures 6A-6F Exemplary data from experimental embodiments of the present disclosure are presented. Figure 6A-6B are shown on the device surface (for example, Figure 2 A composite image of an exemplary SEM image of an integrated circuit test system on a surface 225 of a device and in contact with a device surface. Figure 6C and Fig. 6E are composite images showing exemplary lock-in amplifier output images of an integrated circuit test system respectively on and in contact with a DUT surface. Fig.6D and Fig. 6F are graphs illustrating exemplary lock-in amplifier output spectra of an integrated circuit test system on and in contact with a DUT surface, respectively. Figures 6A-6F The images and data presented in are illustrative examples and are not intended to limit the scope of the present disclosure. Rather, the images and data are presented to demonstrate the improved contact detection provided by the techniques of the present disclosure.

[0069] like Figure 6A-6B As shown, the environment of the probe tip 210 may include relatively dense visual information, such as multiple features 235, surface particles, shadows, charged areas, and edges, which together obscure the shape, outline, and / or shadow of the probe tip 210. As a result, it may be difficult to visually determine contact between the probe tip 210 and the surface 225 of the DUT 125. In some cases, the probe tip 210 may have a rough or other irregular surface, which may be formed by surface accumulation (e.g., carbon contamination or other deposits) and / or due to the manufacturing process, which may further complicate the visual determination of contact with the DUT surface 225. As an illustrative example, Figure 6B Shown with Fig. 6A A small visually discernible difference in the probe tip 210 is observed, but still indicates that the probe tip 210 is in contact with the surface 225.

[0070] Figure 6C The image 605 in can be generated from the SEM data at least in part by filtering the frequency information at approximately a jitter frequency and / or a multiple of the jitter frequency. For example, pixel-by-pixel frequency information from a sequence of SEM images can be sampled by generating time series data of the intensity of a given pixel. Determining the frequency-spatial information (e.g., via digital signal processing techniques, such as Fourier transform techniques) can isolate the jitter motion 240 of the probe tip 210 relative to the surface 225 of the DUT 125 that is not vibrating at the same frequency or frequencies. As shown, the filtered frequency information generates a relief image of the probe tip 210 against a background of arbitrary average noise. Comparable spectral data 610 can be generated using line scans 245, such as Fig.6D, where the edge 615 of the probe tip 210 is indicated in the intensity data by local maxima (eg, peaks and valleys) in the spectral data. Fig.6D , a device having a detector (e.g., Figure 1 The spectrum of the electron beam shadow produced by the orientation of the detector 150) relative to the probe tip 210. In this case, "shadow" refers to the tendency of the secondary electron signal from the surface facing the detector to be brighter relative to the signal from the surface facing away from the detector. In this way, the spectral data 610 includes a peak at the leading edge 615-1 that is brighter than an arbitrary average background "A" and a peak at the trailing edge 615-2 that is darker than the background.

[0071] In some embodiments, an electron beam (e.g., Figure 1 The charged particle beam 147) can be directed, for example, in a spot pattern at the edge 615 of the probe tip 210, such that the shaking motion 240 of the probe tip repeatedly brings the edge 615 of the probe tip under the beam spot. In this way, the frequency of the intensity data can be a multiple of the shaking frequency, and the amplitude can be a scalar value generated as a function of time, for which the amplitude of the value indicates whether the probe tip 210 is in contact with the surface 225 of the DUT 125. This method is also referred to as Figure 2-5 In terms of the spectral data 610 , the point pattern information can be understood as a vector of intensity values ​​of the edge 615 , each element of which is the filtered frequency information at a given time.

[0072] Fig. 6E -F presents a second image 620 of frequency data and corresponding spectral data 625 at about the shake frequency or multiples of the shake frequency. In contrast to image 605 and spectral data 610, probe tip 210 is absent in second image 620, and spectral data 625 indicates a slight shadow of probe tip 210 near trailing edge 615-2. Based at least in part on the anchoring of probe tip 210 to surface 225 upon contact, free vibration of probe tip 210 at about the shake frequency and / or at multiples of the shake frequency is substantially eliminated, as indicated by the absence of peak 610 in spectral data 625. In some cases, some vibration from the shake motion may remain, such that detecting contact may include comparing the intensity of peak 610 intensity values ​​in image 605, spectrum 610, or a scalar value as a function of time to a threshold value below which the probe is considered to be in contact with the surface. In some embodiments, the detection signal may be used to determine whether conductive coupling is established.

[0073] In the foregoing description, various embodiments have been described. For the purpose of explanation, specific configurations and details have been set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to those skilled in the art that these embodiments can be practiced without these specific details. In addition, in order not to obscure the described embodiments, well-known features may have been omitted or simplified. Although the exemplary embodiments described herein focus on integrated circuit test systems, particularly multi-probe systems, these are non-restrictive illustrative embodiments. The embodiments of the present disclosure are not limited to such embodiments, but are intended to address analytical instrument systems, for which a wide array of material samples, such as microbial samples (e.g., for physiological measurements) and / or nanostructure samples, can be analyzed by the probes of the present disclosure.

[0074] Some embodiments of the present disclosure include a system having one or more data processors and / or logic circuits. In some embodiments, the system includes a non-transitory computer-readable storage medium containing instructions, which, when executed on one or more data processors and / or logic circuits, cause one or more data processors and / or logic circuits to perform part or all of one or more methods disclosed herein and / or part or all of one or more processes and workflows. Some embodiments of the present disclosure include a computer program product tangibly embodied in a non-transitory machine-readable storage medium, the computer program product including instructions configured to cause one or more data processors and / or logic circuits to perform part or all of one or more methods disclosed herein and / or part or all of one or more processes.

[0075] The terms and expressions employed herein are used as terms of description rather than limitation, and when such terms and expressions are used, it is not intended to exclude any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the claims. Therefore, it should be understood that while the present disclosure includes specific embodiments and optional features, modifications and changes to the concepts disclosed herein may be made by those skilled in the art, and such modifications and changes are deemed to be within the scope of the appended claims.

[0076] When a term is used without explicit definition, it is understood that unless the term has a special and / or particular meaning in the field of charged particle microscopy systems or other related fields, the term refers to the ordinary meaning of the word. The term "about" or "substantially" is used to indicate a deviation from the stated property, wherein the deviation has little or no effect on the corresponding function, property or attribute of the described structure. In the illustrated example where one dimensional parameter is described as "substantially equal to" another dimensional parameter, the term "substantially" is intended to reflect that the two parameters being compared may be unequal within permissible limits (such as manufacturing tolerances or confidence intervals inherent to system operation). Similarly, where a geometric parameter (such as alignment or angular orientation) is described as "approximately" perpendicular, "substantially" perpendicular, or "substantially" parallel, the term "about" or "substantially" is intended to reflect that the alignment or angular orientation may differ from the precisely stated condition (e.g., not precisely perpendicular) within permissible limits. For numerical values ​​(such as diameter, length, width, etc.), the term "about" may be understood to describe a deviation of up to ±10% from the stated value. For example, a size of "about 10 mm" may describe a size from 9 mm to 11 mm.

[0077] This description provides exemplary embodiments, and is not intended to limit the scope, applicability or configuration of the present disclosure. On the contrary, the subsequent description of the exemplary embodiments will provide enabling descriptions for realizing various embodiments to those skilled in the art. It should be understood that, without departing from the spirit and scope set forth in the appended claims, various changes may be made to the functions and arrangements of the elements. Specific details are given in the description to provide a thorough understanding of the embodiments. However, it should be understood that the embodiments may be put into practice without these specific details. For example, the specific system components, systems, processes and other elements of the present disclosure may be shown in schematic form, or omitted from the diagram, so as to avoid obscuring the embodiments due to unnecessary details. In other cases, well-known circuits, processes, components, structures and / or technologies may be shown without unnecessary details.

Claims

1. A computer-implemented method for detecting contact between a probe tip and a sample surface, the method comprising: dithering the probe in a plane substantially parallel to the surface using a periodic motion having a dithering frequency; directing a charged particle beam toward a region of the probe; generating detector data describing periodic motion of the probe based at least in part on interaction between the charged particle beam and a region of the probe; displacing the probe toward the surface; as well as The detector data is used to detect contact between the probe and the surface. 2 . The computer-implemented method of claim 1 , further comprising determining an approximate location of a tip of the probe included in the region of the probe.

3. The computer-implemented method of claim 2, wherein: Determining the approximate position of the tip of the probe includes: generating detector data describing a region of the probe; and The detector data is used to determine an approximate position of the tip of the probe.

4. The computer-implemented method of claim 1 , wherein: Directing the beam includes scanning the charged particle beam in a line over the area of ​​the probe using line scanning.

5. The computer-implemented method of claim 4, wherein: The mathematical product of the dither frequency and the dwell time of the beam at a point in the line is equal to or greater than one.

6. The computer-implemented method of claim 1 , further comprising: determining an approximate orientation of the probe; as well as Identifier information is generated for the probe based at least in part on the orientation.

7. The computer-implemented method of claim 1 , wherein: The sample includes an integrated circuit having a contact pad, the contact being formed between the probe and the contact pad.

8. The computer-implemented method of claim 1 , wherein: Generating the detector data includes generating filtered data using a lock-in amplifier tuned to the dithering frequency, wherein detecting the contact corresponds to an attenuation of an output of the lock-in amplifier at the dithering frequency.

9. The computer-implemented method of claim 1 , further comprising: dithering the probe at a set of motion frequencies; directing the charged particle beam toward the probe; generating detector data describing a response of the probe to the frequency of motion based at least in part on an interaction between the charged particle beam and the probe; using the detector data to estimate the resonant frequency of the probe, and The dithering frequency is selected to be approximately equal to the resonant frequency.

10. The computer-implemented method of claim 9, wherein: Directing the charged particle beam includes scanning the beam over the surface in a scanning pattern.

11. The computer-implemented method of claim 9, wherein: Estimating the resonant frequency includes isolating the resonant frequency using a lock-in amplifier.

12. The computer-implemented method of claim 9, wherein: The set of motion frequencies includes an element frequency of 100 kHz.

13. One or more non-transitory machine-readable storage media storing instructions that, when executed by a machine, cause the machine to perform operations comprising: dithering the probe in a plane substantially parallel to the surface using a periodic motion having a dithering frequency; directing a charged particle beam toward a region of the probe; generating detector data describing periodic motion of the probe based at least in part on interaction between the charged particle beam and a region of the probe; displacing the probe toward the surface; as well as The detector data is used to detect contact between the probe and the surface.

14. One or more media according to claim 13, wherein: Generating the detector data includes generating filtered data using a lock-in amplifier tuned to the dithering frequency, wherein detecting the contact corresponds to an attenuation of an output of the lock-in amplifier at the dithering frequency.

15. One or more media according to claim 13, wherein: The dithering frequency is approximately equal to the resonant frequency of the probe.

16. One or more media according to claim 13 or 15, wherein: The mathematical product of the dither frequency and the dwell time of the beam at a point is equal to or greater than one.

17. A system for testing an integrated circuit component, the system comprising: Probe; Charged particle beam systems; a detector oriented toward the probe and configured to detect particles generated by an interaction of a charged particle and the probe; a control circuit operably coupled to the probe, the charged particle beam system, and the detector and configured to actuate the probe; as well as One or more non-transitory machine-readable storage media storing instructions that, when executed by the system, cause the system to perform operations including: dithering the probe in a plane substantially parallel to the surface using a periodic motion having a dithering frequency at about a resonant frequency of the probe; directing a charged particle beam toward a region of the probe; generating detector data describing periodic motion of the probe based at least in part on interaction between the charged particle beam and a region of the probe; displacing the probe toward the surface; as well as The detector data is used to detect contact between the probe and the surface.

18. The system of claim 17, wherein: The charged particle beam system is a scanning electron microscope column, and wherein the detector is a secondary electron detector or a backscattered electron detector.

19. The system of claim 17, wherein: Detecting the contact comprises: determining a phase component and a frequency component in the detector data, the phase component and the frequency component being attributable to periodic motion of the probe; aligning the phase component with the phase of a drive signal for the periodic motion; and A change in the frequency component or a change in the phase component of the detector data is detected with respect to the drive signal.

20. The system of claim 17, wherein: The probe is a first probe, the periodic motion is a first periodic motion, the jitter frequency is a first jitter frequency, and wherein the system further comprises a second probe, and wherein the operations further comprise: dithering the second probe in the plane substantially parallel to the surface using a second periodic motion having a second dithering frequency at about a resonant frequency of the second probe; directing the charged particle beam toward a region of the second probe; generating detector data describing periodic motion of the second probe based at least in part on interaction between the charged particle beam and a region of the probe; displacing the second probe toward the surface; and The detector data is used to detect contact between the second probe and the surface.

21. The system of claim 20, wherein: The first jitter frequency and the second jitter frequency are not equal.

Images