Techniques for waveform detection of periodic signals using voltage comparison

Abstract

Techniques for waveform detection of periodic signals using voltage comparison. Systems, components, computer-implemented methods, and algorithms for generating waveform data are described. A method for generating waveform data may include directing a beam of charged particle pulses toward a sample. The sample may include a conductive feature to which a transient electrical signal is applied. The charged particle pulse beam is characterized by a pulse period measured in units of time. The method may include generating detector data over a time period corresponding to a multiple of the pulse period. The detector data may be generated based at least in part on interactions between the charged particles and the sample. The method may also include generating waveform data describing the transient electrical signal using the detector data.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. non-provisional application No. 18 / 456,263, filed on August 25, 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. A typical IC test regime involves verifying circuit performance under different operating conditions by applying a periodic signal to the circuit at increasing power and determining at what point the circuit fails to operate to specification. To this end, IC testing also includes measuring output signals from IC components to compare the measured output to the expected output.

[0005] The measurement of output signals is complicated by several factors. For example, an IC may contain billions of transistors and billions of internal signal nets, but may have only hundreds of input / output pins. Therefore, when the output signal of an IC component under test does not match its expected output, the internal signals within the IC may be probed to determine the local cause of the output signal failure. Therefore, there is a need for techniques that can sample internal and output signals in a DUT in a manner that can be visually inspected during testing (e.g., during troubleshooting) while protecting the IC components from performance degradation and improving the signal-to-noise ratio when the duty cycle deviates from nominal conditions during IC testing. Summary of the invention

[0006] Systems, components, computer-implemented methods, and algorithms for generating waveform data are described. In one aspect, a method for generating waveform data includes directing a pulsed beam of charged particles toward a sample. The sample may include a conductive feature to which a transient electrical signal is applied. The pulsed beam of charged particles is characterized by a pulse period measured in units of time. The method may include generating detector data for time periods corresponding to multiples of the pulse period. The detector data may be generated based at least in part on an interaction between the charged particles and the sample. The method may also include generating waveform data describing the transient electrical signal using the detector data.

[0007] In some embodiments, the transient signal is a periodic electrical signal. The value "P" may be the period of the transient signal measured in units of time. The pulse period may differ from an integer multiple N*P of P by an increment dP. The method may also include determining a duty cycle of the transient electrical signal using the waveform data. The method may also include determining a period "P" of the transient signal, generating a charged particle beam using a charged particle source, and operating a beam blanker using a periodic pulse signal to pulse the charged particle beam. The period of the periodic pulse signal may deviate from an integer multiple of P.

[0008] In some embodiments, the detector data may be generated using a scanning electron microscope in an imaging mode. The detector data may include an image of a surface of the sample, the image including contrast information describing a waveform. The image may include two-dimensional image data, and the contrast information includes a two-dimensional contrast pattern. Generating the waveform data may include sampling a one-dimensional vector of image data from the detector data in a direction perpendicular to the contrast pattern.

[0009] In some embodiments, the detector data is generated using a scanning electron microscope in a fixed-point mode. The detector data may include a detector signal whose amplitude varies over time for a position on the surface of the sample. The position may be a first position on the surface of the sample, the detector data may be first detector data, the time period may be a first time period, the multiple may be a first multiple, and the waveform data may be first waveform data. The method may also include: directing the charged particle pulse beam toward a second position on the surface of the sample, generating second detector data in a second time period corresponding to a second multiple of the pulse period, and generating second waveform data for the second position. Generating the waveform data may include sampling a segment from the detector signal. The segment may describe the temporal dynamics of the transient electrical signal.

[0010] In some embodiments, the method also includes generating a trigger signal using the transient electrical signal. The trigger period of the trigger signal may be approximately equal to the period P of the transient electrical signal and the least common multiple of the pulse period. The method may also include segmenting the waveform data into one or more segmented waveform data blocks, the duration of the block being based at least in part on the trigger period. The start time and end time of the block may be based at least in part on the trigger signal. The method may also include generating visualization data using the one or more segmented waveform data blocks. The visualization data may be configured to modify a display of an electronic device to present the waveform data as a standing wave waveform. The method may further include modifying the display using the visualization data.

[0011] In some embodiments, the sample includes an integrated circuit. The charged particles can be directed to a region of the integrated circuit that includes the conductive feature.

[0012] In a second aspect, a system includes a charged particle microscope. The system may include a computing device operably coupled to the charged particle microscope. The system may also include one or more non-transitory machine-readable storage media operably coupled to the computing device and storing executable instructions that, when executed, cause the system to perform the operations of the aforementioned aspects.

[0013] In some embodiments, the scanning electron microscope can be operated in a fixed-point mode. The detector data may include a detector signal whose amplitude varies with time at a given position on the surface of the sample. The position is a first position on the surface of the sample, the detector data is first detector data, the time period is a first time period, the multiple is a first multiple, and the waveform data is first waveform data. The operations may also include: referencing a set of positions on the DUT, directing the charged particle pulse beam toward a second position on the surface of the sample, the second position being one of the positions in the set, generating second detector data in a second time period corresponding to a second multiple of the pulse period, and generating second waveform data for the second position.

[0014] The terms and expressions that have been adopted 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 should be recognized that various modifications are possible within the scope of the subject matter claimed. 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 make modifications and changes to 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 flow chart illustrating an exemplary process for generating a differential image of a device under test according to some embodiments of the present disclosure.

[0018] Figure 3 is a schematic diagram illustrating an exemplary image processing method for generating a differential image according to some embodiments of the present disclosure.

[0019] FIG. 4A to FIG. 4Gis a schematic diagram illustrating exemplary integrated circuit test data including voltage data and a differential image according to some embodiments of the present disclosure.

[0020] Figure 5 is a graph illustrating exemplary average differential data as a function of differential phase differential according to some embodiments of the present disclosure.

[0021] In the accompanying 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 described. DETAILED DESCRIPTION

[0022] Although exemplary embodiments have been illustrated and described, it will be appreciated 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 imaging waveforms using voltage contrast 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 contemplated for use in analytical instrument systems configured for electrical signal measurement (which may be measured by techniques including secondary electron detection) and analysis using downsampling.

[0023] 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. Testing typically involves applying one or more voltage signals to the integrated circuit components of the DUT while measuring the DUT's response to the signals. During testing, the signals may be varied to simulate out-of-spec or other challenging conditions as a method of stress testing the DUT with the intent of inducing failure of the DUT while generating measurement data. The measurement data can then be used to better understand the performance characteristics of the DUT, including whether the wafer from which the DUT was removed meets one or more quality criteria.

[0024] A typical IC test regime involves applying a periodic signal (e.g., a clock signal) to a circuit and monitoring the behavior of the circuit as the operating voltage of the circuit varies around a nominal value. The power consumption of the circuit may decrease as the operating voltage decreases, which may be advantageous for low-power applications such as mobile computing, however, the circuit performance may also degrade below the nominal operating voltage. Below a threshold operating voltage, the circuit may stop operating. An illustrative example exists in propagating a clock signal through a circuit. At a nominal operating voltage, the circuit is able to propagate a clock signal through the circuit at a 50% duty cycle, corresponding to a clock signal that is logically high or "on" 50% of the time. As the operating voltage deviates from the nominal voltage, the duty cycle of the clock signal may also deviate from the target, i.e., 50%. Techniques for detecting such periodic clock signals that are independent of the duty cycle of the clock provide the advantages of redundant and non-contact measurements, which have relatively little impact on the system being measured compared to direct measurement techniques (e.g., probe circuits).

[0025] The measurement of the output signal is complicated by several factors. For example, the DUT test mode signal may include approximately 1 GHz (1x10 9 Hz). At such frequencies, the signal-to-noise ratio can be affected by limitations of the measurement equipment and sampling techniques. Similarly, output signals with frequencies on the order of GHz are often difficult to interpret visually. During IC testing, as the duty cycle approaches 0 or 100%, imaging techniques that already have relatively low signal-to-noise detectability for a nominal 50% duty cycle may not be able to fully detect the clock signal. Therefore, there is a need for techniques that can sample internal and output signals in a DUT during testing in a manner that can be visually inspected intuitively (e.g., during troubleshooting) while protecting IC components from performance degradation and improving the signal-to-noise ratio when the duty cycle deviates from nominal conditions during IC testing.

[0026] To this end, embodiments of the present disclosure include systems, methods, algorithms, and non-transitory media storing machine-readable instructions for generating waveform data describing electrical activity of integrated circuit components. In an illustrative example, a method may include directing a charged particle beam toward a sample. The beam may be a pulsed beam. The sample may include a conductive feature to which a transient electrical signal may be applied. The charged particle pulsed beam is characterized by a pulse period measured in units of time. The method may include generating detector data for a time period corresponding to a multiple of the pulse period, the detector data being generated based at least in part on an interaction between the charged particles and the sample. The method may also include using the detector data to generate waveform data describing the transient electrical signal.

[0027] Figure 1is 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 that are 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 test component 130 that is electrically coupled to components of the DUT 125 via a controller (also referred to as a test fixture 135). 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.

[0028] The instrument 105 includes a test section 140 in which a test assembly 130 is disposed, including a DUT 125 and electronic components for driving a test circuit (e.g., a test device 135), 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 to the test section 140 is a charged particle column 145. The charged particle column 145 can be an ion beam (e.g., a focused ion beam (FIB)) column or an electron beam column (e.g., as part of a scanning electron microscope). 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 test section 140 at an angle to the charged particle column 145.

[0029] The charged particle column 145 can generate a charged particle beam 147 and can focus the charged particle beam 147 onto a region 127 of the DUT 125. The region 127 can include Figure 3One or more conductive features described in more detail may be electrically enabled and disabled based on one or more transient electrical signals (also referred to as test patterns, test signals, test loops, etc.) applied to the DUT. The interaction of the charged particle beam 147 with the DUT 125 generates one or more detectable signals that may be received by one or more detectors 155 operably coupled to the test section 140 and configured to generate detector data based at least in part on the measurement of the signals. In an illustrative example, the detectors 155 may include secondary electron detectors, backscattered electron detectors, photon detectors, imaging sensors (e.g., CCDs), etc. In comparison to a typical scanning electron microscope (SEM), the test section 140 may omit sample manipulation tools, such as interlocks, sample stages, etc., at least in part because the DUT 125 may be removably coupled to the test assembly 130, which may be disposed on a stage, bracket, or other holding assembly that enables electronic and thermal coupling to the test section 140 (e.g., coupling to the test device 135). The charged particle beam 147 may be directed toward the DUT 125 using various operating modes including, but not limited to, an imaging mode, a line scan mode, a fixed-point mode, and / or a pulse mode.

[0030] To this end, the charged particle column 145 may include a beam blanker 150 disposed in the column and configured to apply an electric field and / or a magnetic field to the path of the entire charged particle beam 147. For example, control electronics 151 operably coupled to the beam blanker 150 may apply a time-varying voltage to electrodes of the beam blanker 150 such that the electric field may reversibly deflect the charged particles 147 into the beam blanker. Operating the beam blanker may allow the charged particle column 145 to direct the charged particle pulse toward the DUT 125, as described with reference to FIG. Figures 2 to 5 Described in more detail. In some embodiments, the pulse includes as few as 1 charged particle to about 1000 charged particles, including physically meaningful fractions of the cited range and subranges thereof. For example, the pulse may include 3 charged particles, 5 charged particles, 10 charged particles, 15 charged particles, etc. In some embodiments, the pulse may extend over multiple cycles of the test signal, so that the technology of the present disclosure may include sampling from multiple points in a set of detector data that corresponds to a relatively long time period relative to the period of the test signal.

[0031] In some embodiments, the test assembly 130 is electrically coupled to components of the test section 140 via a coupling 165, through which one or more test cards 170 may be driven. The test cards 170 may encode test loop schemes and may interact with the DUT 125 to input and output signals to the DUT 125 and relay signals to other components of the exemplary system 100 (e.g., the client PC 115 and / or the IPC 110).

[0032] Computing devices 110 and 115 may be general purpose machines (e.g., laptops, tablet computers, smart phones, servers, etc.) configured to operate instrument 105 or otherwise interact with it. Instrument 105 may in turn include electronic components that form part of a dedicated computing device, including control circuits configured to drive test loops, operate test assembly 130, control electron beam column 145, and operate vacuum systems and thermal management systems. In an illustrative example, test assembly 130 may be driven by a chip tester that operates independently of instrument 105. The operation of test assembly 130 may be coordinated with the operation of instrument 105. For example, the chip tester may generate a trigger signal at the beginning of each test loop and transmit it to instrument 105. In turn, instrument 105 may respond to the trigger signal at least in part by detecting a signal at a given location in the DUT. In another example, dedicated control electronics may be provided with instrument 105 to coordinate the operation of instrument 105 (such as the operation of detector 155 and / or blocker 150) with the operation of test assembly 130. IPC 110 may be a machine provided with software configured to interface with instrument 105 and allow a user of instrument 105 to conduct testing of DUT 125. Similarly, client PC 115 may be configured to control one or more systems of instrument 105 (e.g., via IPC 110 and / or by interfacing with instrument 105 via network 120) to conduct testing of DUT 125.

[0033] 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.

[0034] The exemplary system 100 may include additional and / or alternative components in addition to those illustrated. For example, the instrument 105 may be operably coupled to one or more external components such as a signal generator, a data acquisition system, a power supply system, thermal management, etc. Such components may be housed, for example, in a cabinet physically separate from the instrument 105, but may be operably coupled to the charged particle column 145, the test section 140, the detector 155, etc., via electrical and / or fluid handling connections.

[0035] Figure 2 is a flow chart illustrating an exemplary process 200 for generating waveform data of a device under test (DUT) according to some embodiments of the present disclosure. One or more operations of the exemplary process 200 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 2 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 the illustrative example, the operations for applying a test signal, directing a charged particle pulse toward the DUT (e.g., Figure 1 DUT 125) and operations to generate detector data, wherein the system (e.g., Figure 1 The exemplary system 100 of the present invention is configured to generate visualization data ( Figures 3 to 5 example shown).

[0036] Although the exemplary process 200 is described as a sequence of operations, it should be understood that at least some of the operations may be omitted, repeated, parallelized, combined, and / or reordered. In some embodiments, additional operations are performed before and / or after the operations of the exemplary process 200, which are omitted for clarity of explanation, such as operations for calibration of the electron source, consistency and aberration correction of the charged particle beam, introduction of a DUT sample into the vacuum system, calibrating the system, etc. In another example, a test pattern of a time-varying voltage signal is applied to an integrated circuit component as part of determining one or more failure modes of the DUT. With reference to the exemplary process 200, the operation of the instrument may be combined with a test component (e.g., Figure 1 The DUT may be configured to coordinate the operation of the test assembly 130) as part of generating waveform data describing the electrical activity of the IC components of the DUT, from which duty cycle information and other information may be derived.

[0037] At operation 205, exemplary process 200 includes directing a charged particle beam toward a DUT (eg, Figure 1The beam may be pulsed. In some embodiments, the beam may be pulsed at least in part using charged particles (e.g., ions, electrons) in a beam blanker (e.g., Figure 1 The charged particle pulses may be generated by intermittently redirecting and / or blocking a focused beam in a blocker 150, but other techniques may be used. Operation 205 may be coordinated with a test signal, such as reference Figures 3 to 4G In more detail, at least some of the charged particle pulses are incident on a region of the DUT (e.g., Figure 1 127 in the DUT), incident on that region when that portion of the region of the DUT is inactive (referred to as being in an "off" state).

[0038] In some embodiments, operation 205 may include operating the charged particle source in a mode referred to as "CW" or continuous wave, in which the charged particle beam is continuously emitted for a period of time long enough to extend over multiple cycles of the test signal. In CW operation, the detector data may be sampled at times corresponding to the pulse period. In such cases, sampling errors may occur when the frequency of the clock signal is higher than the cutoff frequency of the secondary electron detector. With the clock signal typically being hundreds of MHz, for some typical secondary electron detectors, the detector bandwidth may be approximately 5 MHz. Therefore, a secondary electron detector with a bandwidth of 100 MHz may be used to directly generate differential data by sampling the detector data and performing a differential operation on the sampled data.

[0039] In this manner, at operation 210, one or more detectors (e.g., Figure 1The detector 155) may generate detector data based at least in part on the interaction between the charged particles of the pulsed beam and the DUT. In some embodiments, the detector data includes secondary electron detector data, which may be generated by collecting secondary electrons re-emitted from the surface of the DUT in response to the charged particle pulse (e.g., using an Everhart-Thornley type detector). Without being constrained by a particular physical mechanism, the probability of secondary electron re-emission may be higher in low potential areas and lower in high potential areas, so that detector data describing active areas of the DUT may appear relatively bright or dark in the detector data. In the case of an electronic image, the relative brightness may look like lighter coloring (e.g., bright areas or saturated areas of the image), while for a spectrum, line scan, or fixed-point signal, the relative brightness may correspond to a higher average signal amplitude (e.g., varying over time or position). In this way, the amplitude of the detector signal (e.g., in units of voltage) may be related to the voltage of a region of the DUT (e.g., the voltage of a transistor gate). In terms of "on" and "off" states, the test pattern may include a periodic or time-varying signal having periods of relatively high voltage and relatively low voltage, where the high voltage corresponds to the "on" state and the low voltage corresponds to the "off" state.

[0040] In some embodiments, operations 205 and 210 are repeated in multiple iterations, for example as part of spatially scanning a charged particle beam with multiple pulses over at least a portion of a surface of the DUT. The iterations can be coordinated with the test pattern such that the pulse period describing the time period between repeated iterations of operations 205 and 210 deviates from the period P of the test pattern by a time increment dP. In this way, an interference effect can be generated between the test pattern and the detector data, such that the detector data generated in multiple iterations of operation 210 can be used to generate downsampled waveform data describing the test pattern. As described in reference Figures 3 to 4G As described in more detail, interference effects can produce detector data, as described in reference Figure 3 and Figure 5When processed in more detail, this detector data can be used to extract time domain information about the test pattern and / or visualize the waveform applied to one or more given IC elements (e.g., conductive features, dielectric features, etc.) of the DUT. Line scan or fixed-point mode data can be used to achieve similar purposes, such as spatially scanning a pulsed beam across a linear region of the DUT and generating one-dimensional detector data showing signal amplitude that varies with beam position. As part of operation 205, the fixed-point mode can provide information by mapping locations of interest on the DUT, such as reference hot spot simulation analysis of the DUT. In this way, the average electron (or ion) dose of the DUT can be reduced overall without affecting the quality of the waveform data generated by the exemplary process 200. To this end, DUT design information can be used to define a set of locations in a region of interest on the DUT where waveform data can be generated.

[0041] The test loop may include test patterns with frequencies on the order of 1 GHz to 10 GHz, corresponding to periods on the order of about 1 nanosecond or less. Physical limitations governing the response time of charged particle microscopy systems may limit the temporal resolution of the detector data, such that successive iterations of operations 205 and 210 may be spaced apart in time by approximately an integer multiple of the period and an offset of increment dP, such that the detector data generated upon successive iterations of operation 210 are temporally resolved. In this manner, a pulse period P may be defined as e (or the sampling period of CW operation), so P e ≈N*P+dP. For example, when the period of the test pattern is about 3 ns and the time resolution of the charged particle system and the detector is about 100 ns, the integer multiple N may be about 50. In this way, the first iteration of operation 205 and operation 210 may be performed at the initial time t o The first iteration is performed at about t1≈N*P+dP≈150ns+dP, the second iteration is performed at about t1≈2*N*P+2*dP≈300ns+2*dP, etc. In this way, each data point is resolved in time and the electronic pulse progresses through the test pattern period P in time.

[0042] The value of delta dP may be based at least in part on the temporal resolution of the beam blanker, which may be a fraction of a nanosecond (e.g., 1x10 -10 In this manner, each subsequent iteration of operations 205 and 210 may be incrementally offset relative to the test pattern by an increasing multiple of dP. In practice, the detector data generated in repeated iterations of operation 210 may be understood as sampling different points on the test pattern, such as Figure 3As illustrated, a waveform at a given location on the DUT can be reconstructed therefrom. In addition, the interference effect described by the waveform data generated in operation 215 allows the duty cycle to be derived. The duty cycle can be an important indicator of IC performance, and when the DUT begins to fail, the duty cycle gradually deviates from the specification. In this way, operation 215 may include, for example, determining the duty cycle of the IC component by sampling the amplitude of the secondary electron signal over a time period, reconstructing the temporal dynamics of the electrical activity of the IC component, and determining the ratio of the "on" time to the "off" time of the IC component. Advantageously, this sampling technique can also reduce the total dose of charged particles incident on the DUT surface by subjecting the surface of the DUT to a charged particle flux during a portion of the time when the test mode is applied to the IC component of the DUT.

[0043] Figure 3 3 is a schematic diagram illustrating an exemplary data processing method 300 for generating waveform data 305 according to some embodiments of the present disclosure. Generating waveform data 305 may include: Figure 1 Scanning a charged particle beam (e.g., Figure 1 The charged particle beam 147 in the image 315 of the region 310 is generated while pulsing the beam, as shown in reference Figure 2 305. In the case where the detector data includes line scan data or point pattern data, the waveform data 305 can be or include spectral data extracted from the detector data. For images, the waveform data 305 can be sampled from the image data. In this way, the image data can be sampled to generate waveform data for multiple locations of the area 310 and / or multiple different test patterns at different times.

[0044] Region 310 includes a plurality of features 320, which may be integrated circuit components, conductive areas of a surface, or other features. During the active "on" portion of the test mode, one or more of features 320 may be electrically activated intermittently according to the test mode. Figure 2As described, by generating detector data in a pulsed mode, the image 315 may include one or more patterned regions 325, in contrast to those regions corresponding to inactive features 320 that do not display such patterns. The patterned regions 325 are displayed as the same dark and white horizontal stripe pattern, referred to as a "spiral stripe" pattern. However, it should be understood that different patterns may be displayed in different active regions, for example, where different test modes are applied to different components of the DUT, or where different components receive different signal inputs as part of the operation of the DUT. The illustrated patterns are at least partially derived from downsampling the temporal activity (e.g., frequency, duty cycle, etc.) of the DUT, thereby allowing the image data to visually represent the "on" and "off" states of at least a subset of the features 320 in the combined image. For integer multiples of a given value N and a given value of the delta dP, the pattern can be measured and upsampled to reconstruct the waveform observed at the relevant feature 320.

[0045] Measuring patterns in image data may include extracting intensity curves from the image and applying one or more spectral analysis techniques to determine the amplitude of the detector signal as a function of position. Figure 3 As illustrated, the intensity curve can be extracted by sampling the image data along ray 330, which is oriented relative to the pattern so that the waveform captures the periodic characteristics of the pattern. In the case of a horizontally oriented pattern, such as Figure 3 As shown, the orientation of ray 330 can be substantially vertical. Since the orientation of the pattern is based at least in part on the scanning pattern of the charged particle beam used to generate the image data, ray 330 can be oriented in a direction different from the direction shown. Along the direction of ray 330, the amplitude of the image signal (e.g., measured in counts, voltage, etc.) can be sampled to generate the vector of waveform data 305.

[0046] The raw waveform data vector will include noise from the detector data. Thus, the exemplary method 300 may include one or more post-processing operations applied to at least a portion of the waveform data 305 as part of determining temporal characteristics of the activity of the DUT component sampled by the ray 330 and generating output data 350 (such as filtered waveform data). Such characteristics include, but are not limited to, frequency, period 335 and 340, and / or duty cycle. A filter 345 (such as a bandpass filter or other frequency-based filter) may be used to selectively remove noise from the waveform data 305.

[0047] Figure 3The spectra in , although not drawn to scale, represent actual experimental data extracted from a conductive element in a sample under the application of a periodic voltage. As shown, temporal dynamic information can be extracted to reconstruct different duty cycles. Period 335 and period 340 can be equal or can be different. In the illustrated example, period 335 and period 340 are substantially equal, but appear visually different due to the different distances over which the corresponding rays 330 extend. The duty cycles are different, as shown in reference FIG. 4A to FIG. 4G Advantageously, the exemplary method 300 is relatively insensitive to the duty cycle of the DUT, at least in part because the "on" state and the "off" state are sampled to generate detector data (e.g., image data) from which the downsampled waveform can be extracted. In this manner, the patterned region 325 can be generated even when the duty cycle deviates from the nominal value.

[0048] FIG. 4A to FIG. 4G is a schematic diagram illustrating exemplary integrated circuit test data including voltage data and exemplary electron microscope images according to some embodiments of the present disclosure. Figure 4A , Figure 4B , Figure 4D and Figure 4F Indicates a voltage signal corresponding to a test mode using a square wave signal. Figure 4C , Figure 4E and Figure 4G 2. An electron microscope image (e.g., Figure 3 315), as shown in reference Figures 2 to 3 Describe in more detail.

[0049] Figure 4A 4 is an exemplary test mode using a square wave voltage signal characterized by a period 400. In integrated circuit testing, the period 400 may be on the order of 1 nanosecond to 100 nanoseconds, as determined by the IC manufacturer's test plan. In this way, the exemplary process 200 may be coordinated with any test mode. Figure 4A Duty cycles that deviate from 50% are also illustrated. Although not drawn to scale, Figure 4A The duty cycle of the exemplary test pattern in corresponds to a value between 10% and 30%. However, the technology of the present disclosure is not limited to this range and is relatively insensitive to the duty cycle compared to conventional technologies.

[0050] exist Figure 4A , Figure 4B , Figure 4D and Figure 4FIn each of the examples, a sampling period 405 is shown spanning multiple values ​​of the period 400, as indicated by parallel lines intersecting the horizontal axis of time. The sampling period 405 differs from the period by a time increment dP 410, which may be from about 0.00001 nanoseconds to about 1 nanosecond, including subranges, fractions, and interpolations thereof. The value of dP may be based at least in part on the time resolution of the beam blanker of the system with which the exemplary processes of the present disclosure are implemented. For example, where the system has a time resolution of 0.0001 nanoseconds for the detector data, the downsampling may be reduced to provide more detailed detector data from which the waveform data may be generated.

[0051] Figure 4B Sampling conditions are illustrated where a sampling period 405 initially coincides with two valid "on" states of the DUT at duty cycle values ​​above 50%. Each cycle 400 of the test pattern can be decomposed by increments 410 to provide the number of sampling points in each complete cycle of the test pattern. The duration of the "on" valid state plus the increment 410 yields the number of sampling periods 405 that measured the "on" state. Similarly, the duration of the "off" state plus the increment 410 yields the number of sampling periods 405 that measured the "off" state. Similarly, the duty cycle can be determined by measuring the number of points in the waveform data that sampled the "on" state and the number of points that sampled the "off" state, and finding the ratio of the two. Spatial distances in the image can be correlated to time domain information using beam scanning pattern information (e.g., dwell time and scan rate) used to generate the image data. Based on this information, the waveform data can be converted from position to time as the independent variable. In Figure 4C , lower duty cycles (close to 50%) do not affect the quality of the detector data and / or image data. Figure 4D The example duty cycle is significantly lower than 50%, which is the observed portion of the DUT (e.g., Figure 3 310 in the figure) is close to a fault example, in which the sampling technique of the present disclosure produces a pattern in the detector data, and waveform data can be extracted from the pattern, which can be processed to reproduce the waveform of the test mode.

[0052] In this manner, the processes and techniques of the present disclosure (e.g., Figure 2An exemplary process 200 of the present invention may include operations for reconstructing waveforms of test patterns for periodically and / or non-periodically activating IC components of a DUT, thereby allowing the system to monitor changes in duty cycle and other performance characteristics during testing. This method can be used repeatedly during a test loop, so that waveform data can be generated in a manner that is substantially insensitive to changes in duty cycle. In some embodiments, increment 410 can be modified during the test process. For example, when the duty cycle is below or above the point where the "on" state or the "off" state is shorter than increment 410, the increment can be shortened to provide one or more sampling points during the corresponding state.

[0053] Figure 5 is a flowchart illustrating an exemplary data processing technique 500 for generating visualization data of a test pattern according to some embodiments of the present disclosure. The exemplary technique 500 may be performed automatically (e.g., without human intervention), pseudo-automatically (e.g., with limited human intervention), and / or manually (e.g., manually specifying process parameters, starting, terminating, etc.). The exemplary technique 500 may constitute Figure 2 As part of the exemplary process 200, the generated waveform data may be used by a tester system (e.g., Figure 1 The system 100) outputs and / or visualizes the user. Figure 5 5 , exemplary technique 500 is shown as generating visualization data for display on digital oscilloscope 505, but similar data may be generated as part of exemplary technique 500 for display on other devices (e.g., Figure 1 Client PC 115 in Figure 1 The waveform data is displayed on an instrument (such as a PC 110) in the apparatus.

[0054] The exemplary technique 500 may include a technique for locking the phase of the waveform data so as to visualize the waveform data as a standing wave. To this end, the exemplary technique may include generating a trigger signal 510 based at least in part on a transient electrical signal 515 (such as a test pattern provided to the DUT). The trigger period of the trigger signal 510 may be approximately equal to the least common multiple of the period P of the transient electrical signal 515 (e.g., the period 400 in FIG. 4 ) and the pulse period provided to pulse the charged particle beam (e.g., the sampling period 405 in FIG. 4 ). Therefore, the trigger period may also be a smaller number, defined by the least common multiple of the two periods.

[0055] The trigger signal 510 can be used to process the detector data and / or the waveform data so as to segment the waveform data into one or more segments of waveform data blocks 525 (at the segmenter block 520). The segmentation can be based at least in part on the duration of the block defined at least in part by the trigger period. The start time and the end time can be based at least in part on the trigger signal. For example, the trigger signal can include timing information, such as a start trigger and an end trigger. In another example, the trigger signal can be generated simultaneously with the visualization data, so that the segmentation can be initiated by the trigger signal (e.g., as a result of a user selecting a menu option to display the visualization data on the observation device 505). In some embodiments, the exemplary technique 500 can include filtering and / or smoothing the segmented waveform data 525, providing smoothed data 527, thereby reducing noise in the visualization data 535, thereby simplifying visual inspection and reducing quantification variability.

[0056] The exemplary technique may also include generating visualization data 535 using one or more segmented waveform data blocks 525 at the auto recorder block 530. The visualization data 525 is configured to modify a display of the observation device 505 to present the waveform data as a standing wave waveform 540. In this manner, the exemplary technique may include modifying a display of the observation device using the visualization data to visualize the waveform data 535 generated as part of the exemplary process of the present disclosure (e.g., the exemplary process 200, the exemplary method 300, etc.). Advantageously, the visualization standing wave allows a user of the observation device 505 to visually assess the temporal dynamics of the waveform concurrently with the DUT under test. For example, the duty cycle may be visually assessed and quantified during testing, rather than employing post-test analysis.

[0057] 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 may 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, and specifically on scanning electron microscope systems, these are non-limiting exemplary embodiments.

[0058] 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.

[0059] 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.

[0060] 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 examples 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, in the case 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 or other values ​​typical in the relevant technical field. For example, a dimension of "approximately 10 mm" may describe a dimension of 9 mm to 11 mm, and a time of the order of 1 ns may mean a time of 0.3 ns to 3 ns.

[0061] 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, the method comprising: directing a pulsed beam of charged particles toward a sample including a conductive feature to which a transient electrical signal is applied, wherein the pulsed beam of charged particles is characterized by a pulse period measured in units of time; generating detector data for a time period corresponding to a multiple of the pulse period, the detector data being generated based at least in part on an interaction between the charged particles and the sample; and Waveform data describing the transient electrical signal is generated using the detector data.

2. The computer-implemented method of claim 1 , wherein the transient signal is a periodic electrical signal, wherein a value “P” is the period of the transient signal measured in units of time, and wherein the pulse period differs from an integer multiple N*P of P by an increment dP. 3 . The computer-implemented method of claim 1 , further comprising determining a duty cycle of the transient electrical signal using the waveform data.

4. The computer-implemented method of claim 1 , further comprising: Determining the period "P" of the transient signal; generating a charged particle beam using a charged particle source; as well as The beam blanker is operated using a periodic pulse signal to apply pulses to the charged particle beam, and the period of the periodic pulse signal deviates from an integer multiple of P.

5. The computer-implemented method of claim 1, wherein the detector data is generated using a scanning electron microscope in an imaging mode, and wherein the detector data comprises an image of a surface of the sample, the image containing contrast information describing the waveform.

6. The computer-implemented method of claim 5, wherein the image comprises two-dimensional image data and the contrast information comprises a two-dimensional contrast pattern, and wherein generating the waveform data comprises sampling a one-dimensional vector of image data from the detector data along a direction perpendicular to the contrast pattern.

7. The computer-implemented method of claim 1, wherein the detector data is generated using a scanning electron microscope in a fixed-point mode, wherein the detector data comprises a detector signal whose amplitude varies with time at a location on the surface of the sample.

8. The computer-implemented method of claim 7, wherein the location is a first location on the surface of the sample, the detector data is first detector data, the time period is a first time period, the multiple is a first multiple, and the waveform data is first waveform data, the method further comprising: directing the pulsed beam of charged particles toward a second location on the surface of the sample; generating second detector data for a second time period corresponding to a second multiple of the pulse period; as well as Second waveform data of the second position is generated.

9. The computer-implemented method of claim 7, wherein generating the waveform data comprises sampling segments from the detector signal, the segments describing the temporal dynamics of the transient electrical signal.

10. The computer-implemented method of claim 1 , further comprising: A trigger signal is generated using the transient electrical signal, wherein a trigger period of the trigger signal is approximately equal to a least common multiple of a period P of the transient electrical signal and the pulse period.

11. The computer-implemented method of claim 10, further comprising: segmenting the waveform data into one or more blocks of segmented waveform data, the duration of the blocks being based at least in part on the trigger period and the start time and end time being based at least in part on the trigger signal; generating visualization data using the one or more pieces of segmented waveform data, the visualization data being configured to modify a display of an electronic device to present the waveform data as a standing wave waveform; as well as The display is modified using the visualization data.

12. The computer-implemented method of claim 1, wherein the sample comprises an integrated circuit, and wherein the charged particles are directed to a region of the integrated circuit comprising the conductive feature.

13. A system, comprising: charged particle microscopy; a computing device operably coupled to the charged-particle microscope; and one or more non-transitory machine-readable storage media operably coupled to the computing device and storing executable instructions that, when executed, cause the system to perform operations including: directing a pulsed beam of charged particles toward a sample including a conductive feature to which a transient electrical signal is applied, wherein the pulsed beam of charged particles is characterized by a pulse period measured in units of time; generating detector data for a time period corresponding to a multiple of the pulse period, the detector data being generated based at least in part on an interaction between the charged particles and the sample; and Waveform data describing the transient electrical signal is generated using the detector data.

14. The system of claim 13, wherein the transient signal is a periodic electrical signal, wherein the value "P" is the period of the transient signal measured in units of time, and wherein the pulse period differs from an integer multiple N*P of P by an increment dP.

15. The system of claim 13, further comprising determining a duty cycle of the transient electrical signal using the waveform data.

16. The system according to claim 13, further comprising: Determining the period "P" of the transient signal; generating a charged particle beam using a charged particle source; as well as The beam blanker is operated using a periodic pulse signal to apply pulses to the charged particle beam, and the period of the periodic pulse signal deviates from an integer multiple of P.

17. The system of claim 13, wherein the detector data is generated using a scanning electron microscope in a fixed-point mode, wherein the detector data comprises a detector signal whose amplitude varies with time at a location on the surface of the sample.

18. The system of claim 17, wherein the position is a first position on the surface of the sample, the detector data is first detector data, the time period is a first time period, the multiple is a first multiple, and the waveform data is first waveform data, the operations further comprising: referencing a set of locations on the DUT; directing the pulsed beam of charged particles toward a second location on the surface of the sample, the second location being one of the locations in the group; generating second detector data for a second time period corresponding to a second multiple of the pulse period; as well as Second waveform data of the second position is generated.

19. The system of claim 13, wherein generating the waveform data comprises sampling segments from the detector data, the segments describing the temporal dynamics of the transient electrical signal.

20. The system of claim 13, wherein the sample comprises an integrated circuit, and wherein the charged particles are directed to a region of the integrated circuit comprising the conductive feature.

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