Methods and probes for the excitation, detection, and sensing of a device under test

Abstract

Methods and probes for excitation, detection, and sensing of samples. An exemplary method includes positioning a probe of a test tool relative to a contact point associated with a sample of a sample array such that the probe is in electrical contact with the sample array at the contact point; driving parallel electrical excitation of the sample, wherein electrical contact between the probe and the contact point is continuously maintained during driving and values regarding testing of the sample are generated by the parallel excitation of the sample; and repeating the foregoing one or more times for other contact points. Another exemplary method includes submerging a probe in a liquid conductive material to provide a conductive liquid at an end of the probe, the conductive liquid being positionable relative to and / or continuously movable relative to a contact point of the sample to facilitate transmission of an electrical signal that drives excitation of the sample.

Description

Background Art

[0001] Devices such as electronic devices, optoelectronic devices, electromechanical devices, and other types of devices may be subject to inspection and testing. One example is electrical excitation that applies a voltage or current to a contact that is in electrical communication with the device. Typically, in this example, the device and the contact are part of the same circuit, and applying the current / voltage is to drive the excitation of the device to generate various signals such as emission values and reflection values. These can then be monitored and / or sensed optically and / or electrically and recorded for analysis. A device subjected to such a test can be referred to as a device under test (DUT).

Summary of the Invention

[0002] Often, there are multiple devices on a test wafer or other surface, and it is desirable and advantageous to devise methods applicable for testing the devices in parallel by performing parallel electrical, electrochemical, optical, or other such excitations along with parallel detection or sensing or both. Thus, a DUT (which may also be referred to herein as a "sample") can refer to each individual device being tested as well as an aggregate of individual devices, regardless of whether the tests are performed simultaneously or sequentially.

[0003] By providing a method / process, the drawbacks of the prior art are overcome and further advantages are provided. An example method is for testing a sample array including individual samples. The method uses a test tool having a plurality of electrically conductive test probes, and the method positions the plurality of test probes relative to a first plurality of contact points of the sample array associated with a first plurality of individual samples of the sample array such that the plurality of test probes are in electrical contact with the sample array at the first plurality of contact points; driving a parallel electrical excitation of the first plurality of individual samples by one or more electrical signals transmitted to the first plurality of contact points via the plurality of test probes, wherein the electrical contact between the plurality of test probes and the first plurality of contact points is continuously maintained while driving the parallel excitation of the first plurality of individual samples, and a first value regarding the test of the first plurality of individual samples is generated by the parallel excitation of the first plurality of individual samples; moving the plurality of test probes relative to the sample array by moving at least one of the plurality of test probes and the sample array, and based on this movement, positioning the plurality of test probes relative to a next plurality of contact points such that the plurality of test probes are in electrical contact with a next plurality of contact points associated with a next plurality of individual samples of the sample array; driving a parallel electrical excitation of the next plurality of individual samples by one or more electrical signals transmitted to the next plurality of contact points via the plurality of test probes, wherein the electrical contact between the plurality of test probes and the next plurality of contact points is continuously maintained while driving the parallel excitation of the next plurality of individual samples, and a second value regarding the test of the next plurality of individual samples is generated by the parallel excitation of the first plurality of individual samples.

[0004] In an embodiment, the individual sample is a micro light emitting diode (micro-LED) device.

[0005] In some embodiments, the step of driving the parallel electrical excitation of the first plurality of individual samples is performed without using active feedback to continuously maintain electrical contact between the plurality of test probes and the first plurality of first contact points during the driving of the parallel electrical excitation of the first plurality of individual samples.

[0006] In an embodiment, the process further includes observing luminescence from the first plurality of individual samples based on an interaction between the plurality of test probes and the first plurality of contact points, and confirming, based on the luminescence, that electrical contact has been made between the plurality of test probes and the first plurality of contact points, and the step of driving is performed in response to the step of confirming.

[0007] In an embodiment, the process further includes observing a reflected signal from the plurality of test probes and confirming, based on the observed reflected signal, that electrical contact has been made between the plurality of test probes and the first plurality of contact points as part of the step of positioning the plurality of test probes relative to the first plurality of contact points, and the step of driving the parallel electrical excitation of the first plurality of individual samples is performed in response to the step of confirming.

[0008] In an embodiment, at least a portion of each of the plurality of test probes is made of a translucent material.

[0009] In an embodiment, the plurality of test probes includes an array of test probes with an equal distance between the test probes.

[0010] In addition, a method for testing a sample is provided, the method comprising: sinking at least a portion of an electrical conductivity test probe of a test device into a liquid conductive material; removing at least a portion of the sunk test probe from the liquid conductive material, such that a portion of the liquid conductive material remains at an end of the test probe to maintain electrical contact with an electrically conductive portion of the test probe; positioning the test probe relative to a contact point of the sample such that a portion of the liquid conductive material at the end of the test probe physically contacts the contact point of the sample; and driving excitation of the sample by an electrical signal transmitted through the test probe through a portion of the liquid conductive material at the end of the test probe to the contact point.

[0011] In an embodiment, the positioning step positions an end of the test probe relative to the contact point such that the end of the test probe and the contact point are physically spaced apart, and a portion of the liquid conductive material occupies at least the space between the end of the test probe and the contact point and electrically bridges the electrically conductive portion of the test probe and the contact point.

[0012] In an embodiment, the sample is a micro light emitting diode (micro LED) device.

[0013] In an embodiment, the liquid conductive material includes a metal. In some such embodiments, the liquid conductive material includes gallium.

[0014] In an embodiment, the process further comprises monitoring an electrical signal from the test probe and determining based on the monitored electrical signal whether electrical contact with the contact point has been made.

[0015] In an embodiment, the test probe is one of a plurality of test probes of a test device, the sample is one of an array of samples, and the steps of sinking, removing, positioning, and driving are each performed using each test probe of the plurality of test probes to electrically couple each test probe to a respective contact point of each sample of the array of samples to drive the excitation of each sample.

[0016] In addition, an apparatus for testing a device under test (DUT). The DUT includes a plurality of individual devices, and the apparatus includes an array of probes, an alignment system for aligning the DUT and the array of probes relative to each other, and a detection system configured to detect signals from the plurality of individual devices. The apparatus is configured to perform a test by scanning electrical contacts of a plurality of sets of individual devices among the plurality of devices and simultaneously driving electrical excitation of the electrical contacts.

[0017] In an embodiment, the scan includes moving the array of probes relative to the DUT by moving at least one of the array of probes and the DUT, by which movement the array of probes contacts respective electrical contacts of each set of individual devices among the plurality of sets of individual devices.

[0018] In an embodiment, by repeatedly moving, the array of probes contacts respective electrical contacts of each set of individual devices, and by the movement, the array of probes (i) contacts a set of electrical contacts of one set of individual devices among the plurality of sets of individual devices, then (ii) becomes non-contact with the set of electrical contacts of the one set of individual devices, and then (iii) contacts another set of electrical contacts of another set of individual devices among the plurality of sets of individual devices.

[0019] In an embodiment, the scan includes scanning the DUT under an array of probes.

[0020] In an embodiment, the alignment system is further for leveling the DUT with respect to the array of probes.

[0021] In an embodiment, the signals include optical, electrical, or electrochemical signals from individual devices, and the tool is further configured to detect the optical, electrical, or electrochemical signals using a detection system. In an example, the tool can detect such signals regardless of the presence or absence of excitation (it can detect spontaneous emission).

[0022] A further aspect of the present disclosure relates to a system and a computer program product configured to implement the methods described above and herein. The "Summary" of this section is not intended to illustrate any aspect, any implementation, and / or any embodiment of the present disclosure. Further features and advantages are realized by the concepts described herein.

Brief Description of the Drawings

[0023] The aspects described herein are specifically pointed out and clearly claimed as examples in the claims at the end of this specification. The foregoing and other objects, features, and advantages of the present disclosure will be apparent from the following detailed description in conjunction with the accompanying drawings.

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[0038] Described herein are devices, such as equipment for excitation and testing of devices provided on a surface / substrate, such as tools and methods. In some aspects, the induction of excitation of the DUT can be repeated with minimal or no degradation in terms of the effectiveness of the tool or the DUT. The geometric shape corresponding to the desired use case of the tool enables transmissive optical readout or other forms of readout resulting from this excitation, facilitating the performance evaluation of the DUT.

[0039] One example of such tests is electro-optical electroluminescence for the inspection of micro light-emitting diode (also called "micro LED", "micro-LED", "mLED", and "μLED") displays. Numerous examples presented herein relate to the testing of micro LEDs. Testing of micro LEDs can be particularly useful for the inspection of micro LED displays. Micro LED displays incorporate millions of micro LEDs, and their efficient testing is a critically important step in the mass production and marketability of micro LED displays.

[0040] In accordance with the aspects described herein, parallel testing using an array of probes is made possible. Parallel testing in accordance with the aspects described herein can achieve excellent, consistent, and highly reproducible results. By way of example, parallel electrical interactions are performed to effectively excite an array of devices for inspection. Although the features described herein are presented with specific reference to micro LEDs, those skilled in the art will recognize that the features described herein can be used in the testing / inspection of various devices and various samples, such as other types of electromechanical, electro-optical, and electrochemical and chemical devices / samples, and furthermore that the aspects are applicable to both single-element testing and multi-element testing, such as for any array of devices.

[0041] In some embodiments, a tool is provided that operates as a series of probes that apply a voltage or current to contact points to excite a plurality of corresponding devices (e.g., an electronic DUT, optoelectronic DUT, or electromechanical DUT as examples), and then optically and / or electrically monitors signals generated from the plurality of excited devices. The probes form electrical contacts in parallel at multiple sites.

[0042] In a contact test, the probe is physically in contact with the contact point and placed in a state where a certain amount of force is applied. To ensure proper contact between the probe array and the corresponding contact points and to avoid damaging the probe and / or the DUT, the physical interaction between the probe and the contact point, such as the force with which the probe touches the contact point, can be monitored after the initial contact. Subsequently, appropriate adjustments can be made so that the probe continues to reliably contact the relevant contact points with the appropriate contact force applied. The operations and interventions performed based on the observed signals and other indicators of this physical interaction after the initial contact are a form of "feedback". More specifically, the above activities performed after the initial contact to maintain contact are called "active" feedback, and the monitoring / adjustment is part of the technique using feedback for positioning, and perhaps leveling, the test tool with respect to the DUT. Excessive pressure may damage the probe and / or the DUT, but as described in the embodiments herein, various methods are available to avoid such damage.

[0043] As another example, it is also conceivable to make the probe have appropriate flexibility, which is essentially "soft touch" / flexibility, and this can be applied regardless of the presence or absence of monitoring and adjustment as active feedback for adjusting the bending or flexing of the probe, for example, like the tip of a paintbrush bends / flexes. When active feedback is implemented, it is also conceivable that an electronic signal or other signal is changed based on the applied force to identify the appropriate amount of adjustment required to maintain the desired amount of force.

[0044] The methods and devices discussed herein enable repeated parallel flexible contacts (electrical contacts in some embodiments) and interactions to functionally and effectively excite a number of devices under test without damaging the probes or devices and without the need and / or initiation of active feedback measurement / monitoring (although such active feedback is possible if desired). In some examples, this is provided by appropriate mechanical properties such that a plurality of probes can repeatedly and properly interact with the electrical contacts of a device without damaging the structure of the probe or device. Additionally, the use of liquid metal acting as a flexible interface between a device and one or more probes is contemplated to be provided as described herein. Thus, in embodiments where electrical contact has been established, excitation of the device can be observed optically (e.g., by a human eye or, by way of example, by a camera or other optical / image system) and / or electrically, although active feedback, e.g., feedback including identifying whether electrical contact has been broken or continuously checking an electrical signal for leveling purposes or checking, by way of example, whether an applied force is properly maintained, may be performed if desired.

[0045] The probe configuration may vary depending on the individual DUT. Considering the probe configuration of a plurality of probes (array), a flexible probe array can be fabricated with an appropriate pitch and geometry such that, when desired, the DUT is visible without being blocked at the highest magnification of an optical microscope while exciting the DUT. Other microfabrication techniques such as silicon microfabrication and 3D printing can provide what is necessary in terms of fabricating a probe array with the appropriate flexibility, mechanical properties, geometry, and electrical patterning to supply the necessary electrical inputs and outputs as determined by the specific parameters of the DUT to achieve the desired excitation.

[0046] As a specific example, a matrix or array of probes can be provided, for example, as part of a patterned board or card, and configured such that the probe array can electrically detect connections such as electrical connections formed with a DUT. This can be useful for leveling and aligning the probe array with respect to the DUT. Leveling can be an important part of the test process, regardless of whether it is based on electrical contact / interaction, mechanical leveling, or optical leveling, or otherwise. When using leveling based on electrical contact, it may be desirable to detect whether and when an interaction occurs between the test probe and the electrical contact of the DUT for driving electrical excitation. Detection of such electrical connections between the tool and the device under test is also considered extremely important for leveling the tool (e.g., the probe array of the tool) on the surface of the wafer or other substrate having the device under test and for ensuring accurate test results. It is also conceivable to use other aspects of probe-surface interaction for leveling the probes used to test the device. It is also conceivable to implement capacitive signals, and even optical signals, for aligning the probe with respect to the surface. For example, it is also conceivable that a capacitive signal providing an indicator of contact that can be used for leveling purposes excites the device under test.

[0047] In addition to the probe itself providing signals for alignment, there are other methods of leveling, alignment, and relative alignment that have conventionally required high precision. These are often used in the semiconductor industry for the precise interaction of the wafer on which the device is patterned and the tool. In a specific example, the equipment for leveling and alignment can be considered to include the following sub-assemblies: a wafer loader, a wafer stage, a wafer alignment system, a loader for the test tool, a tool stage and a tool alignment system, and an optical detection system. All of these sub-assemblies have become readily available after years of development in the semiconductor industry and can be implemented together with the aspects discussed in this specification. In some examples, they can be provided as part of an enclosure that maintains an accurate temperature to control the expansion or contraction of the wafer due to temperature variations. The enclosure may optionally further include other systems that assist in the process, such as air conditioning, power supplies, control panels, and various other electrical and ancillary components, to implement the aspects described in this specification.

[0048] Fabrication techniques applied to the aspects described in this specification, such as the fabrication of probe arrays, can be considered to allow for various modifications. One example is the modification of the pitch of the probes for proper alignment with an array of devices under test. The devices may, for example, have pitches set in micrometer, sub-micrometer, or nanometer units.

[0049] In terms of the electrical contact between the probe test tool and the DUT, various geometric shapes can be considered and tolerated. For example, if each device of the array-shaped device to be tested is associated with two electrical contacts (e.g., positive and negative polarities), the two electrical contacts corresponding to each individual device in the array can be considered to be on both sides of the individual device (i.e., for example, one positive (P) or lead contact is adjacent to one side of the device, and one negative (N) or ground contact is adjacent to the other side of the device). As another example, a single contact may be used as the first contact (such as a ground contact) for all devices to be tested, and for each such device, a second contact / contact pad (as a lead contact) can be used for each device and provided adjacent to the side of the device. The above specific examples are geometric shapes where a single contact provided on one side (e.g., the bottom surface) of the wafer / substrate / plane where the device is provided is used as the first contact (e.g., ground) for each device, and the second contact (lead contact) for each device is provided on another side (opposite side, top surface) of the wafter / substrate / plane. Other geometric shapes are also possible.

[0050] In the case of an optoelectronic device to be tested, such as a display using micro LEDs, the micro LEDs of the DUT emit light, for example, as a result of electroluminescence, and the emitted light is measured for each micro LED, that is, the respective measured values of the light emitted from each micro LED can be obtained as an indicator of the individual performance of each such micro LED. If the optical device for measuring the emitted light is blocked by the probe array, accurate measurement may be difficult. When the contact points of the probe are on the same side as the individual devices to be tested (micro LEDs) of the test sample, the probe tip for making contact at the contact points can be constructed in an appropriate geometric shape so that the light emission from the devices to be tested is neither unclear nor basically obstructed.

[0051] Optical observation of the luminescence signal or other responses by the DUT in response to the excitation of the DUT can be performed, for example, from above, from below, and / or from the side opposite to the excitation. In some embodiments, a flat and transparent surface such as the surface where the probe array is installed or coupled is used for mechanical support and strength or other purposes, and further allows the emitted light to pass through for detection. The surface can further enable the use of an excitation tool that can be driven by shining light on the wafer or device structure through the transparent surface, and then measuring the photovoltaic or photocurrent generated in the response. This may be the method employed, for example, in testing a solar array where a voltage is generated by optical excitation or other sunlight excitation.

[0052] Microfabrication of the probe array (geometry, pitch, etc.) can be tailored to the characteristics (geometry, pitch, etc.) of the device on the DUT, regardless of the monitoring mode of the device, such as electrical response, the device's photovoltaic / photocurrent response, photoluminescence, capacitance response, or other forms of response. As a result, an integrated structure for the DUT and the measurement tool (e.g., the probe array) is obtained.

[0053] Figures 1A - 1E show an exemplary environment for use incorporating the aspects described herein, along with its components. First, referring to Figure 1A, the environment can be useful for electrically exciting a device for testing / inspection. The exemplary individual device under test (DUT) is indicated by 100 in Figure 1A. Note that the DUT can refer to a collection of such devices 100 or an individual device 100 itself.

[0054] Each DUT 100 can be, for example, an electronic, optoelectronic, or electromechanical device under test, and each can be provided, for example, as part of an integrated circuit on a plane (not shown) such as a wafer or other substrate.

[0055] The test device in this embodiment (which may also be referred to as a "tool" or "test array") includes a frame / structure 102 that holds an array of probes 110. The frame 102 includes transverse supports 106, 108, and probe array arms 104a, 104b, 104c extend between them. Such probe array arms 104a, 104b, 104c each hold a plurality of probes 110 that are each a sub-array. Note that the frame 102 and associated probes in the figure can also be considered just one segment of a larger frame structure and probe assembly / array of the tool. Thus, it is also conceivable to replicate / iterate segment 102 to form a larger test tool. The length of each transverse rail segment 106, 108, and more generally the size of any of the illustrated and described components, can be of any desired size and dimensions. By way of non-limiting example only, the length of each transverse rail segment 106, 108 can be 15,400 μm. FIG. 1B shows, by way of example only, the sizing of probe array arm 104a, which is 2400 μm in length, 93 μm in width, and 18 μm in height (thickness). The sizing, spacing, etc. of the frame 102 including its components, and the sizing, spacing, etc. of the probes can be adjusted according to the layout and sizing of the device being tested. The probe array can be constructed to have an appropriate pitch and geometry for proper contact with the contacts of the DUT and to facilitate lifting and placement of the array on the device.

[0056] Each probe 110 of the array of probes can be a cantilever having a body portion and a tip portion. FIG. 1C shows, by way of example only, the sizing of an exemplary probe 110. The body portion 120 has a base 122 that is 22 μm in length, a side portion 124 that is 107 μm in length, and a thickness of 1 μm. The tip portion 128 has a length of at least 15 μm in this example. The body portion and tip portion of the probe 110 can be constructed as an integral device of a common material, if desired.

[0057] In certain examples, the probe or a portion thereof can be configured and fabricated to have an appropriate flexibility, and it is also conceivable to adjust the flexibility to at least a selected degree. For example, each probe can be configured to have an appropriate force constant / spring constant such that, for a special material such as silicon, the force per meter is 1.0 Newton per meter (N / m) or less. In some embodiments, the constant is from 0.3 to 1.0 (including the endpoints). However, as is well known, the actual force depends on the material of the probe and can vary further depending on the geometric shape, so it is possible to adjust various force constants for such tests. Additionally, as described above, when a conductive material of a liquid such as gallium is used as in the embodiments described elsewhere herein, another, i.e., significantly larger, force constant is possible. Further, the desired force constant will vary depending on various conditions such as the desired cantilever angle or thickness for a particular geometry of the DUT (e.g., varying by orders of magnitude larger or smaller using the same manufacturing technique). In some embodiments, the probe is selected to have a force constant such that when it touches and presses on the contact point, the probe does not break and does not cause more damage to the DUT than necessary. Additionally, the body portion 120 of the probe extends at a first angle (from the probe array arms 104a, 104b, 104c), and the tip portion 128 that forms the end of the probe (the outermost end of the tip, distal to the probe arm) can extend at an angle different from the first angle (i.e., at an angle with respect to the body portion 120). Thus, in the exemplary probe 110, a bending portion or other direction change is provided in the region between the base and the tip of the probe, and the angle of extension changes at that site.

[0058] Returning to FIG. 1A, the frame 102 can be positioned relative to the DUT such that the probes of the probe array contact various contact locations (also referred to as "contacts", "contact pads", "contact points", or simply "pads") for exciting the DUT. In this regard, and in this particular example, each device under test 100 (a micro-LED in this example) is associated with its corresponding unique pair of contact pads, for example, with one being a lead and the other being ground, or one being a positive (+) polarity contact and the other being a negative (-) polarity contact. Associated with the DUT labeled 100 in FIG. 1A are pads 112 and 114, with probes labeled 116 and 118 respectively contacting these pads. It is understood that pads 112, 114 are in electrical contact with DUT 100, enabling the excitation of DUT 100 by the voltage / current applied via the probes. As an example, one probe of the pair can be a voltage source and the other probe of the pair can be a voltage sink.

[0059] FIG. 1D shows, merely by way of example, a dimensional setting of 20 μm × 12 μm and a height of 0.25 μm for an exemplary contact pad (e.g., 112 in FIG. 1A). FIG. 1E shows, merely by way of example, a dimensional setting of 5 μm × 5 μm and a height of 1.5 μm for an exemplary micro-LED 100 (device under test). These are exemplary dimensions and do not limit the geometric shapes of the DUTs and related components that can be used with the aspects discussed herein.

[0060] The step of exciting an individual DUT, in this example a micro-LED, can be initiated by applying a voltage or inducing a current that lights the micro-LED. The probe makes electrical contact with the corresponding contact point / contact pad and is electrically connected to the contact point. These contact points are either part of the device to be excited, such as the micro-LED itself, or incorporated into the device, or are electrically connected to the device by, for example, vias, leads, pins, routes, traces, etc. The voltage / current can be varied and the response of the micro-LED to this change and over the range of the change can be monitored. In the case of micro-LEDs and other types of optoelectronic devices, the light emitted from the device can be measured using a light sensor. Although not shown in FIG. 1A, it is also conceivable to install a transparent panel of glass or other material as a support for the probe array or, alternatively, to place it between the device under test and the light sensor to allow the light from the DUT to be measured to pass through (e.g., upwards). Typically, but not always, all of the devices being tested, or separate subsets of such devices, are part of the same underlying device, for example a display panel in the case of micro-LEDs, and the electrical contacts used in the test can be patterned and formed during the process of forming the underlying device. As an alternative, the electrical contacts used in the test may be patterned and formed separately from the formation of the underlying device.

[0061] In the example of FIG. 1A, since the probes of the probe array are of the cantilever type, the light emitted from the micro LED can sufficiently reach the area above the DUT. Therefore, a light sensor (not shown) can be arranged above the DUT and the probe array portion of the test tool so that the probe does not interfere with the arrival of light and detection by the sensor. In an alternative arrangement of the so-called "flip chip" structure where the contacts are on one side (e.g., the top or bottom surface) of the DUT substrate and the DUT is on the other side (e.g., the bottom or top surface), the interference of the probe with the light emitted from the micro LED may not be a big concern.

[0062] FIG. 11 shows, together with its components, another example environment for incorporating and using the aspects described herein. FIG. 11 shows a segment of a device array and a corresponding segment of a test tool for testing the segment of the device array. Here, the segment of the device array includes 16 devices 1100 in a 4×4 array. PXLx PITCH refers to the pitch (spacing) between the devices 1100 in the x dimension (left - right direction in FIG. 11), while PXLy PITCH refers to the pitch in the y dimension (up - down direction in FIG. 11).

[0063] The illustrated portion of the test tool includes two electroluminescence (EL) contact probe arms 1110a and 1110b, with six probes extending from each arm. More specifically, each arm comprises three probes extending to contacts on one side (e.g., the left side) of the EL contact probe arm and three probes extending to contacts on the other side (e.g., the right side) of the EL contact probe arm. By configuring the probes in this way along each EL contact probe arm, the EL probe arm can explore the device on each of the two sides of the arm, and thus the EL contact probe arm can be made to extend with a pitch (ELx PITCH) corresponding to every other column of the device array in the y-dimension as shown in the figure and with a corresponding pitch in the x-dimension. At the same time, the probes on the same EL contact probe arm are arranged at regular intervals in the y-dimension according to the excitation contact point spacing (Ely PITCH) of the device.

[0064] Each device 1100 has two associated contact points respectively. As an example, using the device labeled 1100 in FIG. 11, device 1100 has an associated first contact point 1102 and an associated second contact point 1104. Contact point 1102 is the contact for exciting device 1100 via a probe 1106 extending from EL contact probe arm 1110a. Contact point 1104 is a common ground point that is electrically connected to other ground contact points of device 1100 in the same row (x-dimension) via a common ground (CG) line. In this example, Elx PITCH = 2 * PXLx PITCH, Ely PITCH = PXLy PITCH, and the common ground line may be on the wafer (not shown) to which device 1100 is bonded.

[0065] FIG. 2 shows an example of an alternative arrangement configuration of the array probes extending from the probe array arm 204. Here, the probe array arm 204 provides a pair of cantilever probes, and each pair is configured and sized to contact and electrically interact with two contacts associated with a given device under test (e.g., a micro-LED). The probe array arm 204 provides probes arranged in two columns, namely, probes in one column each having a first length and probes in another column each having a second length, and the first length is longer than the second length. The probes 206a and 206b in the column of longer probes will provide two contacts for testing the first device 1100 (e.g., by straddling the device to reach the respective contacts on both sides of the device), while the probes 206c and 206d in the column of shorter probes will provide two contacts for testing the second device 1100 (e.g., by straddling the device to reach the respective contacts on both sides of the device). The various other probe pairs shown are used for testing other devices 1100 or for another geometry for testing devices.

[0066] Figure 3A shows an alternative probe according to the aspects described herein. Probe 300 may be of a cantilever type with respect to a probe array arm (not shown). For example, the protruding body portion 302 may extend from the probe array arm at a first angle, and the tip portion 304 forms the end of the probe that extends at an angle different from the first angle, i.e., at an angle with respect to the body portion 302. Thus, along the probe, as the probe extends from its proximal end where it extends out from the probe array arm towards the distal end / tip of the probe, the direction changes at region 306 which is the boundary between the body portion 302 and the tip portion 304. In this example, it is also noted that the probe is configured to have generally flat surfaces that taper down to the probe tip 308, resulting in edges 309a, 309b, 309b that extend in the direction of its elongation along the probe. In some applications, it may be preferable for the probe / probe tip to protrude outwardly and away from the coupling structure (such as a probe array arm) so as not to obstruct the optical element / viewing line for viewing the effects of electrical excitation.

[0067] Figure 3B shows an alternative probe according to the aspects described herein. Here, probe 310 having an end extends generally in one direction (perpendicular and close to the end of the probe array arm in the example of FIG. 3B) from probe array arm 312. This is in contrast to the geometry of FIG. 3A where probe 300 has a bend. This configuration may be useful in situations where a contact pad is on one side of the DUT and the excitation characteristics (e.g., light emission) are observed from the other side of the DUT, and where a bend or curvature in the probe is not required to allow more light to reach and exhibit excitation characteristics.

[0068] In any case, the probe may be an integral element and, in some cases, may be formed from a single or multiple materials. By way of example, the material includes one (or more) conductive materials. It should be noted that the probe / material need not be completely conductive; for example, the probe includes silicon with a coating of gold (or other material). However, in terms of material / composition (and as described elsewhere herein), the probe can have a channel that passes a liquid conductive material to the probe tip and provides droplets of the liquid conductive material through the openings at the probe tip. As a specific example, the probe can be made, in part or in whole, of silicon, silicon nitride, a polymer, etc. At least some of the aforementioned materials (e.g., at least silicon nitride) are known to be translucent. The material may need to be appropriately coated to provide high conductivity. In addition, in some embodiments, the probe is selected to have a spring constant such that when touching and pressing on the contact point, the probe does not break and does not cause more damage to the DUT than necessary. Elements for achieving this include appropriate material selection, appropriate geometric shape, and appropriate sizing of the probe, probe array, and frame / support structure for the probe array. Various geometric shapes for cantilever probes with various distributions and / or lengths and pitches are described herein.

[0069] While it is desired and / or essential that part or all of the probe be flexible, it should also be noted that in this situation, a sufficiently high spring constant may be desired for at least the probe tip in order to maintain the probe tip structure when the probe tip physically interacts with the contact pad. As described elsewhere herein, the presence or absence of flexibility can be irrelevant and optional depending on the situation, e.g., when a liquid conductive material is used in combination with a probe as described below.

[0070] According to the aspects described herein, the electrical connection / coupling between the probe tip for electrical excitation and the contact pad can be made with the probe tip itself being variously spaced from the contact pad. This can be done while effectively and reproducibly uniformly exciting the device under test, without compromising conductivity. For such contact, a conductive liquid material such as liquid metal can be used. Thus, according to some aspects, the liquid conductive material is applied to the probe, still at least partially in liquid form, before the probe contacts the contact pad of the DUT. One way to apply such a liquid conductive material to a solid probe is to dip the protruding probe into the liquid conductive material. Such an operation can be performed without damaging the array / the probes of the array. The conductive material in liquid form adheres to the outer surface of the probe, forming a relatively highly conductive liquid buffer on the outside of the probe tip.

[0071] By way of non-limiting example, liquid gallium can be used due to its high conductivity and other advantageous properties, such as its melting point (about 30 °C). Although the examples described herein show gallium as the liquid conductive material, this is merely one non-limiting example and does not exclude the use of other conductive materials such as metal inks or conductive solutions that exist or may be developed in the future. Generally, the conductive material can be selected for its conductivity, mechanical properties, physical properties, and / or elastic properties, depending on the particular application being used. Gallium is a liquid metal at a temperature convenient for production processes near room temperature and has unparalleled properties well-suited for applications such as micro-LED inspection.

[0072] Figure 4A shows an example of a probe tip that has been immersed in and then removed from a liquid conductive material in accordance with the aspects described herein. Probe 400 has a body portion 402 and a tip portion 404, and tip portion 404 is partially immersed in a pool 420 of liquid gallium and then removed. As a result, droplets 410 of liquid gallium remain on probe tip 404 and surround a portion of the probe tip.

[0073] A “bag” in the form of droplets of liquid is formed and adheres to the probe tip. Depending on the physical and / or chemical processes / changes that can occur after removing the probe tip from the liquid gallium (the physical / chemical changes can vary depending on the environment in which the test is conducted and other conditions), it is conceivable that a relatively thin (e.g., in the micrometer or nanometer range) protective layer 414 of droplet 410 is formed. An example of such a chemical change could be, for example, the formation of a layer of gallium oxide molecules, for example a few nanometers thick. Additionally, or alternatively, other changes in gallium in the probe tip can occur, for example, partial solidification (“cooling”) of the liquid gallium at the surface of the droplet, such that, for example, layer 414 is produced and / or the droplet becomes a partially / fully malleable solid.

[0074] On the other hand, the interior 412 of the "bag" can remain liquid gallium protected by the protective layer 414. Using the example of oxidation that results in an oxide bag with an oxidation protective layer 414, the layer 414 can, as one example, prevent and protect the internal liquid gallium 412 within the oxide bag from further oxidation or rust. The ability to form micro / nano droplets of an oxide-coated conductive liquid conductive material (such as gallium) that seals the probe tip is a result of the high compliance of gallium (or similar liquid metals). The bag having the formed oxide layer functions like a sac-like organ, except that it can rapidly reseal if a hole is opened. The dimensions of the droplets and the outer edge of the bag are adapted to fit around the probe tip and match the contacting surfaces as described herein, so the dimensions of the bag and (in this example) the oxide surface 414 can be, at least in part, a function of the size of the probe tip.

[0075] Such a coated probe 400 after being immersed in the liquid conductive material can be lifted / removed from the pool 420 without breaking the sealed state around the chip, which may be, at least in part, due to the presence of the layer 414 of the bag (such as an oxide layer in the nanometer range) around the chip, which may itself have a protective coating.

[0076] In some examples, the liquid conductive material is instead (or additionally) introduced to the end of the probe, e.g., through the probe body to the probe tip as an example, by a channel, conduit, passageway, or other mechanism of the probe itself. For example, it is also conceivable that the probe is partially hollow and the liquid conductive material is delivered to the opening at the end of the probe and through the opening, in the same way as ink is delivered to the tip through the body of a pen. The liquid conductive material can flow from a reservoir, through a channel / conduit / passageway that extends through the probe such that the liquid conductive material flows through the probe to its end, or be provided in some other way. It is also conceivable that the reservoir supplies the liquid conductive material to a number of probes. In an embodiment, when the liquid conductive material is delivered to / through the opening at the end of the probe, droplets of the liquid conductive material are formed at the end of each test probe.

[0077] Whether formed by immersion or formed through the probe itself at the probe tip, droplets of the liquid conductive material on the array of probe tips facilitate the alignment and leveling of the probes in their interaction with the electrical contacts of the device under test and further enable proper leveling and alignment without active feedback. As the probe tip with the conductive material bag approaches the appropriate contact of the DUT, a portion of the bag on the opposite side of the probe tip (e.g., the bottom of the bag) can come into contact with the contact pad of the DUT, so that the conductive material (rather than the probe tip itself) first interacts with the contact pad. This itself causes chemical and / or physical changes in the conductive material, such as the formation of nanoholes in the oxide portion of the bag (in this example), enabling the probe tip to make electrical contact with the contact pad through the droplet of conductive material and without the probe tip actually physically contacting the surface of the contact pad. On the other hand, the liquid state of the conductive material provides a buffer or "cushion" to the probe tip so that it does not experience the strength of resistance it would face if the probe tip touched the (solid) contact pad or if the conductive material on the chip were solid.

[0078] The electrical interaction and / or contact between the probe tip and the contact point is thus carried out without the probe tip physically contacting the contact point. Therefore, the tip of the probe can thus interact electrically with the contact of the DUT without physically contacting the contact or other part of the DUT, as the conductive material serves as a medium for the electrical connection / connectivity between the tip and the contact point of the DUT. Further, by effectively separating the probe tip from the contact point, this state can enable the tunneling current to be induced from the tip to the surface as a function of the voltage.

[0079] Figure 4B shows an example of the electrical coupling between a probe tip with a conductive material at its end and a flat contact, according to the aspects described herein. As shown in the figure, a probe 400 with a liquid conductive material 412 is positioned relative to a contact 422 (i.e., in electrical communication with the device under test), such that droplets 410 of the liquid conductive material 412 physically contact the contact 422 at a plurality of consecutive points of a continuous flat contact area 424. The droplets 410 are deformed as shown in the figure (compared to the shape in Figure 4A), and there is a gap 416 between the contact 422 and the end of the probe tip closest to the contact 422 (i.e., the end of the probe). Nevertheless, the conductive material electrically couples the probe to the contact 422 even though there is no direct physical contact between any part of the probe and the contact 422.

[0080] In an embodiment, pinholes may occur in the oxide layer of the pad when a probe with droplets of a liquid conductive material contacts the contact pad of the DUT. These pinholes enable the liquid conductive material to act as a contact bridge between the probe tip and the pad of the DUT. Under these conditions, the outer oxide layer can serve to contain the liquid conductive material within so that the liquid does not flow over the surface of the contact pad and substantially separate from the probe tip. Further, if the probe tip has possibly "punctured" the oxide layer that connects the liquid material and the contact pad by being further pressed / moved through the droplet towards the contact pad, pulling the probe tip away from the contact can close such pinholes. That is, for example, pinholes may be quickly and automatically repaired by chemical and / or physical processes related to the liquid conductive material (gallium in this example), such as re-oxidation or a phase change of the oxide, when the probe is pulled back from the DUT.

[0081] Accordingly, it is possible to dip a portion of the probe, such as a probe tip, a portion of the probe tip, and / or other portions of the probe, into a pool of gallium or other liquid conductive material and then lift it to provide a droplet on the probe, and / or the droplet can remain around the probe (the chip in this example) due to the presence of the oxide portion in the nanometer range of the bag. As a result, the probe can be easily moved from the immersion liquid to the sample (e.g., DUT) without losing liquid. Additionally, it is also conceivable that after exciting one or more devices, the probe is lifted from the corresponding contact point and holds a droplet of the liquid conductive material on the probe. The conductive material that may have leaked onto the contact point can be ignored. The array and the sample can then be re-tested for other DUTs by, for example, moving the probe array and / or moving the sample under the probe array to facilitate the interaction between the probe and another set of contact points, such that the probes can be repositioned relative to each other without losing liquid. If necessary, it is also conceivable to re-dip the probe array into gallium during the intervals between repositionings.

[0082] The above-described embodiments help to eliminate or minimize probe tip wear and other degradation, while achieving repeated and flexible contact with the DUT and solving common problems in single or multiple probe-device interactions. Additionally, it is possible to maintain electrical contact with the DUT regardless of the presence or absence of feedback assistance and guidance, because the electrical contact with the DUT can be achieved without the probe tip physically contacting the surface of the contact pad. In this regard, in the embodiments the probe operates in a non-contact mode, in which the probe / probe tip itself does not physically contact the contact point, but instead an electrical connection is established by a conductive material in the form of a liquid droplet that electrically couples the probe tip and the contact point, and the above-described coupling and associated leveling / alignment between the probe and the DUT can be achieved in a tunneling mode with the contacts of the DUT without using active feedback.

[0083] It should be noted that the probe, which is electrically conductive to electrically excite the device under test, has an electrically conductive portion. In the above example, the tip of the probe chip of the probe is electrically conductive, and thus the droplets formed around the probe chip provide a conductive medium from the probe chip to the contact point where the probe chip engages. However, in some examples, the tip of the probe is not necessarily electrically conductive, and other portions are electrically conductive. Therefore, the droplets of the liquid conductive material can be made large enough to make electrical contact with the electrically conductive portion of the probe. In this regard, the depth to which the probe is immersed in the liquid conductive material and / or the portion of the probe immersed in the liquid conductive material can be based on the location of the electrically conductive portion of the probe and, by way of example, on what size the droplets are desired to be, such that when the conductive material contacts the contact pad, an electrical connection from the probe to the contact pad is formed. In this way, by the steps of sinking at least a portion of the test probe into the liquid conductive material and then removing the probe therefrom, droplets of the liquid conductive material remaining at the end of the test probe and in electrical contact with the electrically conductive portion of the test probe can be provided. The liquid conductive material at the end of the test probe can physically contact each contact point, and then an electrical signal can be transmitted through the liquid conductive material to each contact point by the test probe.

[0084] Due to its properties and characteristics, gallium is an excellent candidate for liquid conductive materials for the applications discussed in this specification. Gallium has very high electrical conductivity, boils at 2400 °C, melts at approximately 30 °C, and has an extremely low or virtually zero vapor pressure at room temperature. Although a low vapor pressure can cause the liquid to evaporate, in the case of gallium droplets, the aforementioned oxide layer prevents this. Gallium is low in toxicity as it can be used in air without the risk of aspiration. Additionally, gallium has low viscosity and would normally be able to flow freely, but the oxide coating prevents the flow of gallium and imparts a high surface tension to the gallium. Gallium is approved by the US Food and Drug Administration for human applications such as magnetic resonance imaging. Furthermore, the human body has a natural ability to remove gallium. The properties of gallium also enhance the ease of cleaning and removal, for example, making it possible to remove gallium material from the tip / end / portion of a probe, reproducibly, or when it is necessary to remove any residue on a DUT. For the above and other reasons, gallium is considered to be substantially safe for industrial applications with little or no need for personnel protection and is therefore considered ideal for certain applications of the embodiments of the aspects described in this specification.

[0085] In addition, during the inspection process, in desirable situations, the use of gallium enables the probe to be reversibly coupled to the contact surface via an adhesive bond where the liquid gallium at least partially solidifies and adheres to the contact surface. This adhesive bond can be remotely released using, for example, infrared or heating (such as electrical Joule heating by conductive wiring incorporated into a tool). The temperature for such reversible adhesion is considered to be approximately 23 °C (varying depending on the environment and other conditions), and at temperatures above this, the gallium cleanly peels off the surface with minimal adhesive force.

[0086] Due to the above properties of gallium, whether used as a conductive bridge enabling a non-contact and highly conductive electrical interaction between the probe and the device under test, or as an adhesive, this liquid metal lifts sufficiently from the contact surface under appropriate loading and unloading conditions, so that gallium can be used over multiple cycles (contact, excitation of the device under test, lifting / moving, repetition, etc.) without replacement. No residue remains on the contact surface, and (in the case of an adhesive bond) the adhesive loses little or none of its own substance. Although excellent adhesives are generally difficult to separate from the adherend, the oxide skin of gallium (in this example) can help facilitate this removal with minimal or no residue remaining on the device. Such properties may be extremely important for applications involving electrical contact and / or interaction.

[0087] Therefore, gallium (and similar metallic elements) with a relatively low melting point, high conductivity, negligible vapor pressure, high surface tension, low viscosity, and metallic properties can be excellent candidates for liquid conductive materials. Additionally, the reactivity of gallium, which has historically been considered an impediment in the use of gallium for various applications, i.e., its ability to form oxides, is beneficial in the context of the applications discussed herein.

[0088] As previously stated, gallium is merely an example of a conductive material; other substances may function similarly or may be superior for certain applications. Exemplary alternative liquid metals that may be suitable include, but are not limited to, for example, eutectic mixtures of gallium and / or indium, gallium-indium-zinc, and gallium-indium-tin. It is also conceivable that other yet-to-be-developed liquids with high conductivity could replace the use of gallium.

[0089] Figures 5A-5B illustrate observable changes based on the immersion of a probe tip into a liquid conductive material. More specifically, the figures illustrate the immersion of a probe into liquid gallium. The semi-flexible cantilever probe 502 is shown in a top-down view in this example where the probe tip is below (not visible) the probe body. FIG. 5A shows the probe 502 before the probe tip is immersed in the liquid gallium pool 504, and FIG. 5B shows the probe 502 with the probe tip immersed in the gallium pool 504 and remaining at least partially submerged.

[0090] As the probe 502 approaches the pool 504, the probe tip is attracted to the gallium, and as a result, it is pulled towards the pool 504 and immersed in the gallium. The flexibility of the probe facilitates the bending / flexing to draw the tip into the liquid gallium, and this flexibility aids the interaction between the probe tip and the gallium pool.

[0091] This results in a change in the reflection of the flexible cantilever probe as shown in FIG. 5B where the probe appears very dark in color. Thus, when the probe tip enters the liquid metal, the flexible cantilever bends and the reflection of light from the cantilever changes when viewed with an objective lens from directly above. This indicates that the probe tip is properly immersed in the liquid metal. Even if the reflected light is not directly above the probe's cantilever, a change can occur when the tip enters the liquid metal. The ripples (506) in the gallium may be detected, as an additional or alternative example, to signal that the probe tip has entered the pool 504. This change may generally be limited to near the probe tip, as the more distant regions 508 of the liquid are thought to be less sensitive as they are farther from the probe tip.

[0092] Figures 6A-6B illustrate additional observable changes based on the immersion of a probe chip in a liquid conductive material according to the aspects described herein. In each of FIGS. 6A-6C, the probe chip is presented facing upward towards the objective lens of the microscope, and this example is a view of the probe chip through the objective lens. In FIG. 6A, the chip was inspected after immersing the probe chip in gallium in an environment and conditions where gallium is in a liquid state at room temperature. The dark rectangular portion 602 is the probe, and the coated area 606 on the chip extending from the probe arm is identified. The probe chip indicated by the smaller circular area 606 appears to have a different shade due to the coating of the liquid conductive material. Using a higher numerical aperture objective lens, the chip is observed in more detail in FIG. 6B. The amorphous material seen on the chip at 610 is a coating of liquid gallium. These illustrations show a high level of control in that only a very small portion of the probe is coated.

[0093] If desired, the probe can be easily cleaned, for example, with hydrogen chloride or other solutions to remove the liquid metal. The result of such a cleaning is shown in FIG. 6C. Comparing FIG. 6B (before cleaning) with FIG. 6C (after cleaning), in FIG. 6C it is possible to clearly visually recognize the shape of the pyramidal probe chip 612, indicating that the conductive material resulting from the immersion step has been easily removed.

[0094] FIG. 7 shows an exemplary test device and setup for DUT measurement that can incorporate the aspects discussed herein. FIG. 7 illustrates a basic electrical circuit to which a probe can be connected. Shown is the case where only one probe 704 is used to investigate the DUT 702 at any given time. The DUT comprises contact pads located on a substrate. Opposite contact points are incorporated in the substrate at 706.

[0095] The electrical probe 704 can be in contact with the DUT 702 at the conductive pads of the DUT, which is, for example, an electronic device, an optoelectronic device, or an electromechanical device, for example, directly or through a liquid metal bridge as described herein. The electrical signal 708 is conducted by the connection cables 710, 712 to the resistor 714 and the amplifier 716, enters the ground cable 718 and the BNC cable 720, and is conducted to the auxiliary input 722. The auxiliary input 722 has an auxiliary output and is inside the DT box 724 that provides a bias to the second contact of 706 on the DUT via the bias cable 726. This is just one example of the environment for imposing an electrical signal on the DUT.

[0096] The electrical interaction between the probe and the conductive material, such as a liquid conductive material and the contact pads / points of the DUT, can be traced using a suitable electronic device capable of monitoring voltage / current signals. As described above, this can be the signal that occurs when the probe is immersed in the liquid conductive material and / or when it is electrically coupled to any other conductive surface such as a contact pad. FIG. 8A shows an exemplary current-voltage curve when the probe tip touches a liquid bath or a conductive surface. Plot 802 represents the applied voltage, and plot 804 represents the excitation response (current) measured using the probe tip (e.g., probe 806) in contact with the liquid metal or the conductive material that is the conductive surface 808, or the probe tip in the liquid metal bridging the contact with the conductive surface.

[0097] The conductivity is monitored in one example by the circuit diagram of FIG. 7. The resulting signal 804 is shown as electrical conductivity in FIG. 8A as a function of time while the probe 806 is in the conductive metal liquid 808. This characterizes the electrical properties of the probe / probe tip in contact with the conductive material, whether it is direct contact with the DUT, contact with the DUT through a liquid metal bridge (e.g., a droplet of liquid conductive material), or directly in the liquid metal. It is found that the current shown at 804 follows the applied voltage 804 quite closely, which means the signal is good. As discussed above, the geometry of the probe can vary, and in some embodiments, each probe can have a substantially flat / linear end / tip as shown in FIGS. 8A - 8C, as opposed to the tapering (e.g., getting thinner towards the end) probe tips shown in other examples discussed herein.

[0098] When the probe tip is immersed in the liquid conductive material, the interaction between the tip and the material can be monitored and verified by (i) observing changes in the reflected light as shown in FIGS. 5A - 5B, (ii) monitoring and observing voltage changes, or (iii) a combination of these two.

[0099] In each of the above cases (where the probe is touching the liquid bath or contact pad), the duration of such contact is independent and unrelated to any feedback and does not require feedback. The method in the case of FIG. 8A was performed by a stepping motor while monitoring with a charge-coupled device (CCD), but the use of a CCD is not essential for optical monitoring, and other automatic or manual methods may be appropriate in terms of the method. An excellent monitor for contact may be current measurement as illustrated. In the case of an array of probes and in situations where mainly optical / mechanical schemes are used to measure contact and leveling of the array as described herein, electrical signals may be used as an addition or alternative. By applying conductivity without the need for feedback and regardless of the presence or absence of droplets of liquid metal, the important operation of "leveling" the probe with respect to the contacts of the DUT is simplified. In this regard, current leveling techniques that do not consider conductivity signals require a relatively accurate leveling of the probe with respect to the DUT. However, a byproduct of making the probe easily electrically contactable (e.g., by vacuum coating techniques and / or by immersing the probe in a liquid conductive material) is that the observed electrical conductivity can be used to easily "level" the probe with respect to the DUT surface to which the probe is to make contact. "Leveling" in this context means that each probe is aligned with and / or relative to each one or more contact pads such that it makes proper electrical contact with those contact pads. And using electrical conduction, it is possible to know which probes are in electrical contact with their respective contact pads and thus how to move or tilt the array of probes and / or the DUT to "level" the probes with respect to the DUT.On the other hand, the droplet approach allows for a wider range of probe lengths and more easily enables electrical contact because, for example, the degree of freedom of electrical coupling between the droplet and the target conductive pad is greater. This is because the droplet has thickness, and each probe can still make proper electrical contact with its respective contact pad even if the probe tip is displaced from the contact pad and / or there is a gap between the probe tip and the contact pad, providing a buffer / freedom / tolerance in this sense.

[0100] The flexibility requirements or characteristics of the cantilever-type probe can be relaxed when a liquid metal bridge (droplet) is used, regardless of whether active feedback is used. For example, since the contact with the liquid conductive bag provides the necessary electrical contact and the probe itself does not necessarily need to physically contact the contact pad, the flexibility of the probe may not be as important. Depending on the size of the bag, a buffer of sufficient size can be created such that the probe tip does not need to contact any of the conductive pads.

[0101] Furthermore, in applications where a probe is used on a surface, such as for the conductivity of the probe, thermal conductivity, applications for thermocouple imaging scans, or other applications where electrical connection is required, such a liquid metal bridge can simplify both electrical excitation and the measurement of electrical conductivity, thermal conductivity, and imaging. The above and other electrical-based phenomena will be materially simplified as a result of the characteristics resulting from such a liquid metal bridge. The characteristics include the excellence and effectiveness in providing the necessary electrical contact, protecting the liquid metal and the probe inserted into this liquid inside the thin bag formed by oxidation, and protecting the metal of the probe tip from oxidation. Due to the above and other characteristics, many problems regarding the scan of probe imaging based on electrical interaction can be solved even when using a single probe in addition to a probe array.

[0102] Figure 8B shows an exemplary current-voltage curve and the optical properties of a probe when the probe is coated with gallium and still in air before being guided onto the gold surface (e.g., typically by dipping the probe into a liquid metal and then withdrawing it, and before the probe touches the contact point of the DUT). Plot 810 represents the applied voltage, and plot 812 represents the excitation response (current) measured with the probe tip. The excitation response 812 is essentially just electrical noise. On the other hand, the probe 814 appears relatively dark. This is in contrast to when the probe tip 814 is in contact with a uniform and relatively smooth gold conductive surface as in Figure 8C. In Figure 8C, plot 820 is the applied voltage and plot 822 is the current. There is an obvious and nearly perfect correlation between these two in Figure 8C. In addition, on the right side of the figure shown optically, the probe appears much brighter compared to Figure 8B, illustrating that in addition to the electrical indication of the contact (by the waveform), there is also a visual (optical) indication of the contact. In this embodiment, each probe is already in electrical contact with the metal surface. The example of gallium in Figure 8A has a noisy excitation signal, but the comparison using Figure 8C shows the excellent conductive properties of the liquid metal compared to the excellent conductivity of gold.

[0103] In an embodiment with an array of probes, individual electrical indications (e.g., plots) can be obtained for each probe of the array in order to separately evaluate the situation of the electrical coupling of the probe to the surface (such as a liquid conductive material or contact pad) at that point in time.

[0104] Figures 9A - 9C show examples of electrically based leveling of an array - shaped probe according to the aspects described in this specification. In Figures 9A - 9C, a linear array 902 of probes is provided over a DUT 904 that includes a plurality of devices to be tested. One objective is to level the probes to make generally equal contact with a corresponding set of the plurality of devices. This is done in a two - step operation in this example. Each probe can be monitored (as shown, for example, in Figures 8A - 8C) such that the electrical properties of the probe at any point can indicate whether an electrical contact has occurred between the probe and the corresponding device of the DUT.

[0105] The pitch of the probe array (the spacing between adjacent probes) in this example does not exactly match the pitch (i.e., the spacing between adjacent devices) of an array - shaped optoelectronic device (such as a micro - LED). Thus, probes 11, 8, 5, and 2 do not contact any of the contact points in any of Figures 9A - 9C. First, in Figure 9A, there is no contact between any of the probes of array 902 and DUT 904. In Figure 9B, probes 12, 10, 9, and 7 (most of the upper part of the probe array) are in contact with their respective contact points, as indicated by the emission of light (blue luminescence) from the corresponding four micro - LEDs. Then in Figure 9C, probes 6, 4, 3, and 1 further contact their respective contact points of the DUT, lighting another four micro - LEDs of the DUT. Figures 9A - 9C are for illustrative purposes only, and in actual applications, the pitch of the probe array may be more fully aligned with the pitch of the contact points of the DUT, even if the test is carried out in multiple steps.

[0106] Figures 10A - 10C illustrate continuous excitation when testing a DUT according to the aspects described herein. Reproducibility is very important for an efficient test when testing a DUT having hundreds, thousands, or millions of individual devices to be tested. In Figure 10A, the probes (numbered 1 - 12) of the probe array 1002 are each in contact with a respective contact pad of a first set of contact pads of the DUT corresponding to eight lit micro - LEDs (shown by eight boxes). In Figure 10B, the probes of the array 1002 are disengaged from contact with the first set of contact pads. In Figure 10C, the probes of the array 1002 are in contact with a second set of contact pads of the DUT corresponding to another eight lit micro - LEDs (likewise shown by eight boxes). In some embodiments, the probes are immersed in a liquid conductive metal and then electrically coupled to the first set of contact pads (Figure 10A), then the probes are lifted or otherwise moved away from the first set of contact pads as shown in Figure 10B, optionally immersed again in the liquid conductive material, and then electrically contacted to the second set of contact pads as in Figure 10C.

[0107] In one or some embodiments of the aspects described in this specification, a tool and a method of using the tool are provided. The tool can be designed to hold a probe chip or a plurality of probe chips, optionally in parallel with each other, and to enable flexible contact between the probe chip and a target device (e.g., DUT). The probe chip has a geometric shape suitable for the electrical and / or optical and / or mechanical capabilities and / or chemical properties of the components of the target device, such that the probe chip can excite such components of the target device for a certain period of time (e.g., 1 second or less, etc.), with or without active feedback. This can be achieved while preventing, minimizing, or eliminating the risk of damage to the probe chip due to contact and / or damage to the target device, and further, optionally, while configuring to enable / allow monitoring the effect of excitation by the probe chip by optical visualization and other means.

[0108] Optionally, the tool may be constructed using silicon micro / nano processing techniques. For example, an array / matrix of probes with probe chips can be manufactured at least partially using such processing techniques. As an example, photoresist for etching and deposition of conductive elements and other features for forming integrated circuits or other electrical devices is used for pattern formation of features on a substrate.

[0109] Optionally, the tool may be fabricated from a polymer material and / or a material other than high-purity silicon or doped silicon, such as silicon nitride or other materials having properties that facilitate the effective fabrication of the desired geometric structure.

[0110] In some cases, the tool enables multiple excitation and detection paths to be implemented simultaneously. In some cases, the signal detected by the contact of the probe tip with the DUT is used for leveling the carrier of the probe tip with respect to the DUT, so that multiple (e.g., all) probes of the tool make proper contact with the features of the DUT. This enables leveling by some signal, such as reflection of light from the surface of the tool, e.g., the surface of the probe of the tool. In some examples, leveling can be achieved without measuring the electrical properties (such as current) in the probe tip, but the above and other means for detecting the leveling of the tool with respect to the DUT are not excluded.

[0111] In some cases, the probe tip can be inserted into a conductive material, e.g., a conductive material in liquid form, to coat at least a portion of the probe, e.g., a part or all of the probe tip portion of the probe, to form droplets thereon. This enables the transfer of the liquid conductive material from the bath of the liquid conductive material to the DUT in the form of droplets on the probe tip without depleting the liquid of those droplets on the probe tip. In some cases, the above further enables transfer / relocation / relative movement between the probe tip and the DUT, while the liquid conductive material remains without the need to repeatedly immerse the probe tip in the liquid conductive material if desired, from one or more components of the device (e.g., one set of contact pads) to another set of components of the device (e.g., another set of contact pads). In an embodiment, the liquid conductive material is a liquid metal or contains a liquid metal.

[0112] The probe may be a conductive probe, and there may be an electrically conductive bridge provided, for example, by droplets between each probe tip and the contact on the DUT so that the probe tip does not need to physically contact the DUT directly. For example, the probe tip may be arranged at a distance from the contact of the DUT, and a conductive material (adhering to the probe tip) fills the space between the probe tip and the contact of the DUT, making it possible to electrically couple the probe tip to the contact of the DUT. Optionally, the conductive material coating the probe tip can be easily removed from the probe tip and the DUT. Using a liquid conductive material for the probe tip and for the contact of the DUT may be temporary for the purpose of exciting components of the DUT (such as micro LEDs), i.e., for testing / inspecting these components of the DUT with respect to the desired function. After the test / excitation, for example, the DUT can be separated from the probe, the liquid conductive material can be removed to the extent necessary, and then it can be put into production or used in the manufacture / fabrication of other devices.

[0113] Some of the features of the aspects described in this specification are as follows and can be implemented alone and / or in combination with each other. In an embodiment, a method for testing a device under test (DUT) is provided, the method using a test tool comprising a plurality of electrically conductive test probes, the DUT comprising a plurality of contact points associated with a plurality of individual devices to be electrically excited in the DUT. The method includes positioning a plurality of test probes relative to the plurality of contact points such that the plurality of test probes are in electrical contact with the DUT at the plurality of contact points, driving parallel electrical excitation of the plurality of individual devices with one or more electrical signals transmitted through the plurality of test probes to the plurality of contact points, and continuously maintaining electrical contact between the plurality of test probes and the plurality of contact points while performing the step of driving the parallel excitation. The steps of driving and maintaining can be performed without / without the use of active feedback to continuously maintain electrical contact between the plurality of test probes and the plurality of contact points while performing the step of driving the parallel electrical excitation.

[0114] In any of the foregoing and / or alternative embodiments, the method further includes, as part of the positioning step, observing reflected signals from the plurality of test probes and, based on the observed reflected signals, confirming that electrical contact has occurred between the plurality of test probes and the plurality of contact points, and the driving step is performed (initiated based) in response to the confirming step. In an embodiment, the plurality of test probes are configured to be physically attracted to the plurality of contact points based on a step of positioning the plurality of test probes in proximity to the plurality of contact points, the reflected signals indicating the force applied to the plurality of test probes, and the confirming step is based on observing that the plurality of test probes have been physically attracted to the plurality of contact points and electrical contact has occurred therebetween based on the reflected signals.

[0115] In any of the foregoing and / or alternative embodiments, the method further includes, as part of the positioning step, observing luminescence from a plurality of individual devices and, based on the luminescence, confirming that electrical contact has occurred between a plurality of test probes and a plurality of contact points, and the driving step is performed (initiated) in response to the confirming step.

[0116] In any of the foregoing and / or alternative embodiments, one or more electrical signals driving parallel electrical excitation include a voltage or current applied in parallel to at least some of the plurality of contact points using at least some of the corresponding plurality of test probes.

[0117] In any of the foregoing and / or alternative embodiments, the plurality of individual devices includes a plurality of micro light-emitting diode (micro-LED) devices.

[0118] In any of the foregoing and / or alternative embodiments, the plurality of connection points are the first plurality of connection points of the DUT, the plurality of individually electrically excited devices are the first plurality of individually excited devices, and the method further comprises, after driving the parallel electrical excitation, pulling back / moving the plurality of test probes from / to the plurality of contact points, and then positioning the plurality of test probes with respect to the next plurality of contact points of the DUT such that the plurality of test probes are in electrical contact with the DUT at the next plurality of contact points. In some examples, the movement is performed to move the test probes away from the plurality of contact points until contact with the next plurality of contact points is established. In any case, the method can further comprise driving a parallel electrical excitation of the next plurality of individual devices of the DUT by one or more electrical signals transmitted to the next plurality of contact points via the plurality of test probes. In an embodiment, the method further comprises repeating the pulling back / moving step, the positioning step, and the driving step one or more times such that multiple sets of individual devices of the DUT are electrically excited via multiple sets of contact points of the DUT.

[0119] In any of the foregoing and / or alternative embodiments, the method includes the steps of submerging at least a portion of each test probe of a plurality of test probes into a liquid conductive material, and removing / moving at least a portion of each submerged test probe from the liquid conductive material, wherein for each test probe of the plurality of test probes, a droplet of the liquid conductive material remains at the end of the test probe and is in electrical contact with the electrically conductive portion of the test probe. The positioning step is performed based on the submerging and removing steps. The step of positioning the plurality of test probes positions and drives the plurality of test probes such that for each test probe of the plurality of test probes, the liquid conductive material at the end of the test probe physically contacts each of the plurality of contact points. The driving step transmits an electrical signal through the liquid conductive material to each contact point by the test probe. In a further embodiment, the plurality of connection points are the first plurality of connection points of the DUT, the plurality of individual devices to be electrically excited are the first plurality of individual devices to be excited, and the method further includes, after the step of driving the parallel electrical excitation, the steps of pulling back / moving the plurality of test probes from / to the plurality of contact points, and positioning the plurality of test probes relative to the next plurality of contact points of the DUT such that the plurality of test probes are in electrical contact with the DUT at the next plurality of contact points, and for each test probe of the plurality of test probes, the liquid conductive material at the end of the test probe physically contacts each of the plurality of next contact points. In some examples, the movement is performed to move the test probes away from the plurality of contact points until contact with the next plurality of contact points is established. In any case, the method can further include the step of driving a parallel electrical excitation of the next plurality of individual devices of the DUT by one or more electrical signals transmitted to the next plurality of contact points via the plurality of test probes.In a further embodiment, the method further includes repeating the steps of submerging and removing in a liquid conductive material before positioning a plurality of test probes relative to the following plurality of contact points, and then performing the step of positioning / moving the plurality of test probes relative to the following plurality of contact points. In some examples, this is done while maintaining the amount of conductive material at the probe tip.

[0120] In any of the foregoing and / or alternative embodiments, the plurality of test probes includes an array of test probes where the spacing between the test probes is equidistant.

[0121] In any of the foregoing and / or alternative embodiments, a reservoir containing a liquid conductive material supplies the liquid conductive material to the ends of the plurality of test probes via one or more conduits / channels / passages extending to the ends of the plurality of test probes. In a further embodiment, droplets of the liquid conductive material are formed at the ends of each of the plurality of test probes, and the step of positioning the plurality of test probes positions and drives the plurality of test probes such that for each of the plurality of test probes, the liquid conductive material at the end of the test probe physically contacts each of the plurality of contact points, and the step of driving transmits an electrical signal through the droplets of the liquid conductive material at the end of the test probe to each of the contact points by the test probes.

[0122] According to a further aspect, a method for testing a device under test (DUT) is provided, the method using a test tool comprising electrically conductive test probes, the DUT comprising contact points associated with individual devices to be electrically excited in the DUT, the method comprising positioning the test probes relative to the contact points such that the test probes are in electrical contact with the DUT at the contact points, driving the electrical excitation of the individual devices by means of one or more electrical signals transmitted to the contact points via the test probes, and continuously maintaining electrical contact between the test probes and the contact points while performing the step of driving the electrical excitation, the steps of driving and maintaining being performed without / without the use of active feedback for continuously maintaining electrical contact between a plurality of test probes and a plurality of contact points while performing the step of driving parallel excitations.

[0123] According to a further aspect, a method for testing a device is provided, the method comprising: submerging at least a portion of a test probe of a test device / tool into a liquid conductive material; removing / moving at least a portion of the submerged test probe from the liquid conductive material such that a droplet of the liquid conductive material remains at an end of the test probe and is in electrical contact with an electrically conductive portion of the test probe; positioning a contact point of the test probe and a device under test (DUT) relative to each other such that the liquid conductive material at the end of the test probe physically contacts the contact point of the DUT; driving excitation of the device of the DUT by an electrical signal transmitted through the test probe through the droplet of the liquid conductive material at the end of the test probe. In an embodiment, the positioning step positions the end of the test probe and the contact point relative to each other such that the end of the test probe and the contact point are physically spaced apart, and the droplet of the liquid conductive material occupies at least the space between the probe tip of the test probe and the contact point and electrically bridges the electrically conductive portion of the test probe and the contact point. In such an embodiment, the device of the DUT can include a micro light emitting diode (micro LED).

[0124] In any of the foregoing and / or alternative embodiments, the liquid conductive material includes a metal. This can include, for example, gallium.

[0125] In any of the foregoing and / or alternative embodiments, at least a portion of the submerged test probe includes at least a portion of a probe tip of the test probe.

[0126] In any of the foregoing and / or alternative embodiments, the contact point is a first contact point, and the method further comprises, after the step of driving the excitation, a step of retracting / moving the test probe from / to the first contact point, wherein at least a portion of the droplet of the liquid conductive material remains as a droplet at the end of the test probe after the retracting / moving step and continues to be in electrical contact with the electrically conductive portion of the test probe, a step of positioning the test probe and the next contact point of the DUT relative to each other such that the remaining droplet of the liquid conductive material at the end of the test probe physically contacts the next contact point of the DUT, and a step of driving the excitation of the next device of the DUT by an electrical signal transmitted through the test probe through the droplet of the liquid conductive material at the end of the test probe to the next contact point. In some examples, the movement is performed to move the test probe away from the contact point until contact with the next contact point is established.

[0127] In any of the foregoing and / or alternative embodiments, the method repeats the step of retracting / moving, the step of positioning the test probe and the next contact point relative to each other, and the step of driving the excitation of the next device one or more times, and in each repetition, the next contact point is the next selected contact point corresponding to the next device of the DUT.

[0128] In any of the foregoing and / or alternative embodiments, the method further comprises a step of measuring a signal, such as electroluminescence, mechanical deformation, chemical initiation, and / or electrical excitation of the device based on the step of driving the excitation.

[0129] In any of the foregoing and / or alternative embodiments, the positioning step moves the test probe, the DUT, or both to position the test probe and the contact point closer to each other.

[0130] In any of the foregoing and / or alternative embodiments, the method further includes monitoring an electrical signal from a test probe and determining whether electrical contact has been made with a contact point based on the monitored electrical signal.

[0131] In any of the foregoing and / or alternative embodiments, the test probe is one of an array of test devices or a plurality of test probes, and the steps of lowering, removing, positioning, and driving are performed using each test probe of the array / plurality of test probes to electrically couple each test probe to a respective contact point of the DUT to drive the excitation of each device of the DUT. In an embodiment, this further includes the step of leveling the array / plurality of test probes with respect to a plurality of devices of the DUT and / or the step of aligning the array / plurality of test probes with a plurality of devices of the DUT. The steps of leveling / aligning include monitoring an electrical signal from the test probes of the array / plurality of test probes and determining whether the array / plurality of test probes are leveled and / or aligned with respect to a plurality of devices of the DUT based on the monitored electrical signal. Further, in an embodiment, the method senses, for example, in an optically recognized form, that the test probes of the array / plurality of test probes and the DUT are in continuous contact, which is not necessary and / or not monitored. In an embodiment, active feedback including automatic movement / physical adjustment of at least one of the array / plurality of test probes and the DUT to maintain contact between the test probe of the array / plurality of test probes and the DUT is not necessary and / or not performed.

[0132] In any of the foregoing and / or alternative embodiments, the test probe is manufactured to be inflexible and / or to have a flexibility defined by a selected spring constant, the selected spring constant being optionally selected from a desired range of values, or within a desired range of values, and / or below a threshold value, an exemplary threshold value being 5 Newton meters.

[0133] In an additional embodiment, a method of preparing a test probe for electrical excitation of a device under test is provided. The preparation includes submerging at least a portion of the test probe into a liquid conductive material and removing / moving at least a portion of the submerged test probe from / in relation to the liquid conductive material such that droplets of the liquid conductive material remain at the end of the test probe and are in electrical contact with the electrically conductive portion of the test probe, the liquid conductive material remaining at least partially in a physical form of a liquid or a malleable solid state during electrical excitation of the device under test.

[0134] In a further additional embodiment, a method of testing a device under test (DUT) includes submerging at least a portion of a test probe into a liquid conductive material, removing / moving at least a portion of the submerged test probe from / in relation to the liquid conductive material such that droplets of the liquid conductive material remain at the end of the test probe and are in electrical contact with the electrically conductive portion of the test probe, and guiding droplets of the liquid conductive material at the end of the test probe to a contact point of the DUT, the test probe and the contact point remaining physically spaced apart with the liquid conductive material disposed therebetween during electrical excitation of the device of the DUT associated with the contact point.

[0135] According to a further embodiment, a system for testing a device under test (DUT) is provided, the system including an array / plurality of test probes and a liquid conductive material. In an embodiment, each test probe of the array / plurality of test probes is manufactured to be inflexible and / or to have a flexibility defined by a selected spring constant, the selected spring constant being selected to be, optionally, from a desired range, or within a desired range, and / or below a threshold value, an exemplary threshold value being 5 Newton meters. Additionally, in some embodiments, a method of using the system includes dipping / submerging at least a portion of each test probe of the array / plurality of test probes into the liquid conductive material, and removing / moving at least a portion of each submerged test probe from / with respect to the liquid conductive material such that, for each test probe of the array / plurality of test probes, the liquid conductive material remains at the end of the test probe and is in electrical contact with the electrically conductive portion of the test probe, and moving the array of test probes and / or the DUT towards / against each other such that the liquid conductive material at the ends of the test probes physically contacts respective contact points on the DUT while the liquid conductive material remains at least partially in a liquid state.

[0136] Aspects discussed herein, particularly probe arrays, may be related to probe card technology that provides an assembly of probes as a "card" for a test device. In some embodiments, an array of probes as discussed herein may be provided on a probe card / as part of a probe card. The probe card is typically located under a complex circuit and voltages are applied / impressed through the circuit for the purpose of connecting to the complex circuit and performing tests. The probes of the probe card can project upward from the substrate material of the card. The protrusions may be somewhat flexible and some probes may be longer than others. By being flexible, the longest protrusions can bend / flex until the shorter protrusions physically contact the DUT after the longest protrusions physically contact the DUT. What is considered here is to avoid damage to the probe structure. As a result of the bending of the protrusions, there may be inaccurate and non-uniform physical contact between the probe / chip and each contact point where excitation and measurement of individual components / devices under test are performed. This may be particularly problematic when uniform device excitation is required in various applications, from testing of displays to testing of parallel electrical motions of multiple devices. A technique for overcoming the problems associated with inaccurate and non-uniform contact in off-the-shelf array probes is the provision of a flexible sample surface such as a polymer film. Another example of off-the-shelf array probes when the sample is flexible is used in a technique called beam pen nanolithography. Other lithography applications involve coating the outer surface of the probe with a non-conductive liquid ink. However, there has been no discussion about applying a highly conductive material of a liquid to repeatedly achieve gentle electrical interaction between the probe tip and the device under test. In such a coating, it goes without saying that electrical coupling and excitation are repeated by the same probe / probe tip for continuous contact points, and parallel electrical excitation of devices under test as discussed herein is not possible.

[0137] It is possible to coat the probe tip itself, separately from the immersion step discussed herein, with a hard metal coating material, but the purpose of such a coating has not customarily been to facilitate electrical contact with the surface, but rather to provide an opaque coating around the probe tip to facilitate light propagation in a narrow space and near a sample at a short distance.

[0138] On the other hand, in some techniques involving the use of feedback, probes extending from a flexible polymer film based on hard sapphire are seen. In this situation, a complex feedback method can be realized that can inform the feedback operation by multiple-point imaging in parallel with light reflection and force microscopy. One goal was not to make proper electrical contact with the surface, for example, but rather to make contact as softly as possible while measuring the force for imaging, and to achieve the same electrical excitation conditions for the device to be excited in a flexible, equivalent, and repeatable manner without feedback.

[0139] In another technique for parallel feedback, the array of probes is conductive and extends from a flexible polymer and makes contact alternately rather than in parallel when the sample is scanned under the probe array. The electrical signals obtained in response change over time as the sample is scanned, thus forming a time-varying image of the feedback for imaging. However, this is not effective for the goals of the embodiments herein, such as achieving parallel excitation in a repeatable manner.

[0140] In yet another technique, a large-scale parallel array of silicon probes is provided with a reservoir for delivering non-conductive ink, and the ink is supplied from the reservoir through a liquid delivery channel to a regular chip rather than being applied externally to the probe by submersion / immersion. Further, since this liquid ink is non-conductive as described above, it was used for applications related to lithography rather than for testing the device.

[0141] Depending on the probe design, it is possible to incorporate a "hollow" glass probe. An array of hollow glass tubes has been proposed, for example, for fountain pen-based nanolithography. In one approach, it is conceivable to coat a hollow probe and fill it with a conductive material to enable effective electrical conduction. However, filling such a tube with a conductive material such as liquid metal can be difficult due to the wettability of the hollow probe surface by the liquid metal. This problem may be overcome by chemical modification of such hollow probes or the use of wetting agents when using silicon microfabrication techniques or similar microfabrication techniques for parallel hollow probes.

[0142] Probes that have been used in conjunction with gallium are hollow glass probes that contain liquid metal, and such hollow probes with gallium have been exclusively applied to lithography. In this regard, a method of press-fitting gallium into a glass pipette for writing is known. However, neither the lithography application nor the use of glass probes discloses large-scale array probes for either lithography or, more importantly, for electrical excitation and device observation.

[0143] Furthermore, conventional techniques that utilize some of the above do not provide related techniques for efficiently and effectively leveling all the probes in an array on their respective corresponding contact surfaces. The leveling technique focuses on an assembly of flexure joints with a support structure for moving the array of probes to the surface for leveling. However, according to the aspects described herein, the freedom provided by conductive droplets in terms of an acceptable distance regarding the electrical conductivity between the probe tip and the contact surface enables leveling based on the conductivity of the droplet material along with the surface conductivity monitored as needed. Additionally, or alternatively, leveling based on reflection may be provided.

[0144] While it is conceivable to use mechanical leveling in conjunction with the aspects described herein, it is not essential. This is not possible because, according to past techniques that utilize coated probes, the nature of the ink that coats the probe externally is non-conductive; the electrical interaction with the surface through the conductivity of the probe tip and the surface has never been used to verify leveling, and other methods (such as active feedback) have been used to verify leveling independently of the electrical interaction of the probe tip surface. Nevertheless, note that such other methods are applicable and can be used in conjunction with the aspects described herein.

[0145] Therefore, for test / inspection applications, such as inspecting the micro-LEDs of a display to achieve defect inspection based on electroluminescence, there is no prior art that combines parallel techniques for array probes to achieve good, homogeneous, and repeatable electrical interactions while effectively exciting the array-shaped device.

[0146] According to the embodiments described herein, the inspection time for inspecting a wafer can be shortened. By shortening the inspection time, it becomes possible to introduce test tools / probe arrays as described herein into production / practical applications. As an example, consider a 6-inch wafer of micro-LEDs with a pitch between contacts of 64.8 microns and approximately 4.2 million micro-LEDs. Further, assuming a probe card with 45×45 array-shaped probes (i.e., 2025 probes) for driving voltage / current and a common ground for the reference, approximately 2074 measurements are required to inspect the micro-LEDs across the entire wafer (4.2 million micro-LEDs / 2025 probes = approximately 2074 measurements to inspect approximately 4.2 million micro-LEDs). If each measurement (where 2025 probes test 2025 micro-LEDs) takes 1 second, approximately 2074 seconds (0.6 hours) are required to inspect the micro-LEDs on the wafer. Assuming one probe for each micro-LED to be examined, approximately 4.2 million seconds (about 1.6 months) would be required (merely an example and not limiting).

[0147] Devices and related methods / processes are described herein. FIG. 12 shows an exemplary process for testing a sample array comprising individual samples according to the embodiments described herein. The method uses a test tool comprising a plurality of electrically conductive test probes. The process may be executed, in one or more instances, by a processor or process circuit of one or more computers / computer systems as described herein, such as a computer system of the test tool or a computer system in communication with the test tool.

[0148] The process of FIG. 12 includes positioning a plurality of test probes against a first plurality of contact points of a sample array associated with a first plurality of individual samples of the sample array such that the plurality of test probes are in electrical contact with the sample array at the first plurality of contact points (1202). The process drives (1204) the parallel electrical excitation of the first plurality of individual samples by one or more electrical signals transmitted through the plurality of test probes to the first plurality of contact points, and the electrical contact between the plurality of test probes and the first plurality of contact points is continuously maintained while the step of driving the parallel excitation of the first plurality of individual samples is being performed. The parallel excitation of the first plurality of individual samples results in a first value regarding the test of the first plurality of individual samples. The process determines (1206) whether there are a next plurality of individual samples to be tested. If not (1206, N), the process ends. Otherwise (1206, Y), the process moves (1208) the plurality of test probes relative to the sample array by moving at least one of the plurality of test probes and the sample array, and based on this moving step, positions the plurality of test probes against a next plurality of contact points such that the plurality of test probes are in electrical contact with the next plurality of contact points associated with the next plurality of individual samples of the sample array. The process further drives (1210) the parallel electrical excitation of the next plurality of individual samples by one or more electrical signals transmitted through the plurality of test probes to the next plurality of contact points, and the electrical contact between the plurality of test probes and the next plurality of contact points is continuously maintained while the step of driving the parallel excitation of the next plurality of individual samples is being performed. The parallel excitation of the next plurality of individual samples results in a second value regarding the test of the next plurality of individual samples. After driving the excitation of the next plurality of samples, the process can return to 1206 to end or continue to the next set of samples.

[0149] In an embodiment, the individual sample is a micro light emitting diode (micro-LED) device.

[0150] In some embodiments, the step of driving the parallel electrical excitation of the first plurality of individual samples is performed without using active feedback to continuously maintain electrical contact between the plurality of test probes and the first plurality of first contact points during the step of driving the parallel electrical excitation of the first plurality of individual samples. This also applies to any other individual sample being tested.

[0151] In an embodiment, the process further includes observing luminescence from the first plurality of individual samples based on an interaction between the plurality of test probes and the first plurality of contact points, and confirming, based on the luminescence, that electrical contact is made between the plurality of test probes and the first plurality of contact points, and the driving step is performed in response to the confirming step (i.e., initiated based on or by the confirming step).

[0152] In an embodiment, the process further includes observing a reflected signal from the plurality of test probes and confirming, based on the observed reflected signal, that electrical contact is made between the plurality of test probes and the first plurality of contact points as part of the step of positioning the plurality of test probes relative to the first plurality of contact points, and the step of driving the parallel electrical excitation of the first plurality of individual samples is performed in response to the confirming step (i.e., initiated based on or by the confirming step).

[0153] In an embodiment, at least a portion of each of the plurality of test probes is made of a translucent material.

[0154] In an embodiment, the plurality of test probes includes an array of test probes where the spacing between the test probes is equidistant.

[0155] Figure 13 shows another exemplary process, in this case a process for testing a sample. The process may be executed, in one or more embodiments, by a processor or processing circuitry of one or more computers / computer systems as described herein, such as a computer system of a test tool or a computer system in communication with a test tool.

[0156] As 1302, the process includes submerging at least a portion of a test probe of a test device for electrical conductivity into a conductive material of a liquid, removing at least a portion of the submerged test probe from the conductive material of the liquid, and based thereon, a portion of the conductive material of the liquid remains at an end of the test probe and is in electrical contact with an electrically conductive portion of the test probe. The process includes (1304) positioning the test probe relative to a contact point of the sample such that a portion of the conductive material of the liquid at the end of the test probe physically contacts the contact point of the sample, and (1306) driving excitation of the sample by an electrical signal transmitted to the contact point by the test probe through a portion of the conductive material of the liquid at the end of the test probe.

[0157] In an embodiment, the positioning step positions the end of the test probe relative to the contact point such that the end of the test probe and the contact point are physically spaced apart, and the portion of the conductive material of the liquid occupies at least the space between the end of the test probe and the contact point and electrically bridges the electrically conductive portion of the test probe and the contact point.

[0158] In an embodiment, the sample is a micro light emitting diode (micro LED) device.

[0159] In an embodiment, the conductive material of the liquid includes a metal. In some such embodiments, the conductive material of the liquid includes gallium.

[0160] In an embodiment, the process further includes monitoring an electrical signal from a test probe and determining whether electrical contact has been made with a contact point based on the monitored electrical signal.

[0161] In an embodiment, the test probe is one of a plurality of test probes of a test device, the sample is one of an array of samples, and the steps of lowering, removing, positioning, and driving are performed using each of the plurality of test probes to electrically couple each test probe to a respective contact point of a respective sample of the array of samples to drive excitation of each sample.

[0162] In some examples, the method or aspects thereof may be implemented by one or more computer systems, such as a computer system that controls a device / tool having an array of probes. By this control device, for example, the movement of the tool, DUT, and / or each component can be controlled. The computer system may be incorporated / provided as part of the tool, or may communicate with the tool via one or more communication links, such as a wired or wireless communication link configured for digital / data communication. In some examples, the computer system may be located remotely from the tool. Thus, the processes described herein may be implemented alone or collectively by one or more computer systems. The computer system may also be referred to as a data processing device / system, a computer device / system / node, or simply a computer. The computer system may be based on one or more various system architectures and / or instruction set architectures, such as those provided by Intel Corporation (Santa Clara, California, USA) or ARM Holdings plc (Cambridge, England, UK).

[0163] FIG. 14 shows a computer system 1400 communicating with an external device 1412. The computer system 1400 includes one or more processors 1402, such as a central processing unit (CPU). The processor can read program instructions from a functional component used for executing instructions, such as a location like a cache or main memory, decode the program instructions, execute the program instructions, access memory for instruction execution, and include functional components for writing the results of the executed instructions, etc. The processor 1402 can further include registers used by one or more of the functional components. The computer system 1400 further includes a memory 1404, input / output (I / O) devices 1408, and an I / O interface 1410, which can be coupled to the processor 1402 and to each other by one or more buses and / or other connections. The bus connection represents any one or more of several types of bus structures, such as a memory bus or memory controller, a peripheral bus, a high-speed graphics port, and a processor or local bus using any one of various bus architectures. By way of example and not limitation, such architectures include Industry Standard Architecture (ISA), Micro Channel Architecture (MCA), Extended ISA (EISA), Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnect (PCI).

[0164] Memory 1404 may be, by way of example, main memory or system memory (such as random access memory) used for the execution of program instructions, a storage device such as, by way of example, a hard drive, flash media, or optical media, and / or cache memory, or may include these. Memory 1404 may comprise a cache such as a shared cache that can be coupled to a local cache (such as an L1 cache, an L2 cache, etc. by way of example) of the processor 1402. Additionally, memory 1404 may be at least one computer program product having a set of (such as at least one) program modules, instructions, code, etc. configured to execute the functions of the embodiments described herein when executed by one or more processors, or may include the computer program product.

[0165] Memory 1404 can store an operating system 1405 and other computer programs 1406, such as one or more computer programs / applications to be executed to implement the aspects described herein. Specifically, the program / application can include computer-readable program instructions configurable to execute the functions of the embodiments of the aspects described herein.

[0166] Examples of I / O devices 1408 include, but are not limited to, microphones, speakers, global positioning system (GPS) devices, cameras, light sources, accelerometers, gyroscopes, magnetometers, sensor devices configured to sense light, proximity, heart rate, body temperature and / or ambient temperature, blood pressure, and / or epidermal resistance, and activity monitors. The I / O device may be incorporated into the computer system as shown in the figure, but in some embodiments, the I / O device can also be regarded as an external device (1412) coupled to the computer system through one or more I / O interfaces 1410.

[0167] Computer system 1400 can communicate with one or more external devices 1412 via one or more I / O interfaces 1410. Exemplary external devices include a keyboard, a pointing device, a display, and / or any other device that enables a user to interact with computer system 1400. Other exemplary external devices include any device that enables computer system 1400 to communicate with one or more other computing systems or peripheral devices such as a printer. A network interface / adapter is an exemplary I / O interface that enables computer system 1400 to communicate with one or more networks, such as a local area network (LAN), a general wide area network (WAN), and / or a public network (e.g., the Internet), etc., to provide communication with other computer devices or systems, storage devices, etc. Ethernet-based (such as Wi-Fi) interfaces and Bluetooth® adapters are merely examples of currently available types of network adapters used in computer systems (BLUETOOTH is a registered trademark of Bluetooth SIG, Inc., Kirkland, Washington, USA).

[0168] Communication between I / O interface 1410 and external device 1412 can be carried out via a wired and / or wireless communication link 1411, such as an Ethernet-based wired connection or wireless connection. Exemplary wireless connections include cellular, Wi-Fi, Bluetooth®, proximity, short-range, or other types of wireless connections. More generally, communication link 1411 can be any suitable wireless and / or wired communication link for communicating data.

[0169] Examples of the specific external device 1412 include one or more data storage devices that can store one or more programs, one or more computer-readable program instructions, and / or data, etc. The computer system 1400 may include removable / non-removable, volatile / non-volatile computer system storage media, and / or may be coupled to and communicable with the storage media (e.g., as an external device of the computer system). For example, the system may include a non-removable non-volatile magnetic media (typically called a "hard drive"), a magnetic disk drive for reading and writing to a removable non-volatile magnetic disk (e.g., a "floppy disk"), and / or an optical disk drive for reading and writing to a removable non-volatile optical disk such as a CD-ROM, DVD-ROM, or other optical media, and / or may be coupled thereto.

[0170] The computer system 1400 can operate in a number of other general-purpose or special-purpose computing system environments or configurations. The computer system 1400 can take any of a variety of forms, and well-known examples thereof include, but are not limited to, personal computer (PC) systems, server computer systems such as messaging servers, thin clients, thick clients, workstations, laptops, handheld devices, mobile devices / computers such as smartphones, tablets, and wearable devices, multi-processor systems, microprocessor-based systems, telephony devices, network appliances (such as edge appliances), virtualization devices, storage controllers, set-top boxes, programmable household electronics, network PCs, minicomputer systems, mainframe computer systems, and distributed cloud computing environments including any of the above systems or devices, etc.

[0171] Aspects of the present invention can be a system, a method, and / or a computer program product, all of which can be configured to implement or facilitate the aspects described herein. In some embodiments, aspects of the present invention can take the form of a computer program product that can be embodied as a computer-readable medium. The computer-readable medium can be a tangible storage device / media in which computer-readable program code / instructions are stored. Exemplary computer-readable media include, but are not limited to, electronic, magnetic, optical, or semiconductor storage devices or systems, or any combination of the foregoing. Exemplary embodiments of computer-readable media include a hard drive or other mass storage device, a wired electrical connection, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory such as EPROM or flash memory, an optical fiber, a portable computer disk / diskette, such as a compact disk read-only memory (CD-ROM) or a digital versatile disk (DVD), etc., an optical storage device, a magnetic storage device, or any combination of the foregoing. The computer-readable medium can be made readable by a processor, an arithmetic processing unit, etc. for obtaining data (e.g., instructions) from the medium for execution. In a particular example, the computer program product comprises / stores one or more computer-readable media having computer-readable program code for providing and facilitating one or more aspects described herein, or comprises such media.

[0172] As described above, program instructions embodied / stored in a computer-readable medium can be obtained and executed by any of a variety of suitable components, such as a processor of a computer system that causes the computer system to operate and function in a particular manner. Such program instructions for performing operations for implementing, achieving, or facilitating the aspects described herein can be written in any desired programming language or can be compiled from code written in a programming language. In some embodiments, such programming languages include object-oriented and / or procedural programming languages such as C, C++, C#, Java, and the like.

[0173] Program code can include one or more program instructions obtained for execution by one or more processors. The computer program instructions are provided, for example, to one or more processors of one or more computer systems to generate a machine, and when the program instructions are executed by the one or more processors, are adapted to implement, achieve, or facilitate aspects of the present invention, such as the operations or functions described in the flowcharts and / or block diagrams described herein. Thus, each block, or combination of blocks, of the flowchart diagrams and / or block diagrams illustrated and described herein can, in some embodiments, be practiced by computer program instructions.

[0174] Although various examples are provided, it is possible to make variations without departing from the spirit of the aspects described in the claims.

[0175] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, it will be understood that the terms "comprises" and / or "comprising", when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0176] All structural, material, acts, and equivalents of the corresponding components of all means-plus-function or step-plus-function components in the claims below, if any, are intended to include any structure, material, or act for performing the functions in combination with other components specifically recited in the claims. The description of one or more embodiments is presented for purposes of illustration and description and is not intended to be exhaustive or limited to the forms disclosed. Numerous modifications and variations will be apparent to those of ordinary skill in the art. Embodiments are chosen and described in order to best explain the various aspects and practical applications and to enable others of ordinary skill in the art to understand the various embodiments with various modifications as are suited to the particular use contemplated.

Claims

Claim 1 A method for testing a sample array containing individual samples, the method using a test tool comprising a plurality of electrically conductive test probes, the method comprising: Positioning a plurality of test probes relative to a first plurality of contact points of the sample array associated with a first plurality of individual samples of the sample array such that the plurality of test probes are in electrical contact with the sample array at the first plurality of contact points; Driving a parallel electrical excitation of the first plurality of individual samples by one or more electrical signals transmitted to the first plurality of contact points via the plurality of test probes, wherein the electrical contact between the plurality of test probes and the first plurality of contact points is continuously maintained during the step of driving the parallel excitation of the first plurality of individual samples, and a first value regarding the test of the first plurality of individual samples is generated by the parallel excitation of the first plurality of individual samples; Moving the plurality of test probes relative to the sample array by moving at least one of the plurality of test probes and the sample array, and based on this movement, positioning the plurality of test probes relative to the next plurality of contact points such that the plurality of test probes are in electrical contact with the next plurality of contact points associated with the next plurality of individual samples of the sample array; Driving a parallel electrical excitation of the next plurality of individual samples by one or more electrical signals transmitted to the next plurality of contact points via the plurality of test probes, wherein the electrical contact between the plurality of test probes and the next plurality of contact points is continuously maintained during the step of driving the parallel excitation of the next plurality of individual samples, and a second value regarding the test of the next plurality of individual samples is generated by the parallel excitation of the first plurality of individual samples A method comprising. Claim 2 The method according to claim 1, wherein the individual sample is a micro light emitting diode (micro LED) device. Claim 3 The step of driving the parallel electrical excitation of the first plurality of individual samples is performed without using active feedback to continuously maintain electrical contact between the plurality of test probes and the first plurality of first contact points during the performance of the step of driving the parallel electrical excitation of the first plurality of individual samples, the method according to claim 1.

4. Based on the interaction between the plurality of test probes and the first plurality of contact points, observing luminescence from the first plurality of individual samples, and based on the luminescence, further including the step of confirming that electrical contact has been made between the plurality of test probes and the first plurality of contact points, the driving step being performed in response to the confirming step, the method according to claim 1.

5. As part of the step of positioning the plurality of test probes relative to the first plurality of contact points, observing a reflected signal from the plurality of test probes, and based on the observed reflected signal, further including the step of confirming that electrical contact has been made between the plurality of test probes and the first plurality of contact points, the step of driving the parallel electrical excitation of the first plurality of individual samples being performed in response to the confirming step, the method according to claim 1.

6. At least a portion of each of the plurality of test probes is made of a translucent material, the method according to claim 1.

7. The plurality of test probes includes an array of test probes with an equal distance between the test probes, the method according to claim 1.

8. A method for testing a sample, submerging at least a portion of the electrical conductivity test probes of the test device into a liquid conductive material; removing at least a portion of the submerged test probes from the liquid conductive material, such that a portion of the liquid conductive material remains at the end of the test probe and is in electrical contact with the electrically conductive portion of the test probe; positioning the test probes relative to the contact points of the sample such that a portion of the liquid conductive material at the end of the test probe physically contacts the contact points of the sample; driving the excitation of the sample by an electrical signal transmitted through the portion of the liquid conductive material at the end of the test probe and through the test probe to the contact points comprising a method.

9. The positioning step positions the end of the test probe relative to the contact point such that the end of the test probe and the contact point are physically spaced apart, and a portion of the liquid conductive material occupies at least the space between the end of the test probe and the contact point and electrically bridges the electrically conductive portion of the test probe and the contact point, the method according to claim 8.

10. The method according to claim 8, wherein the sample is a micro light emitting diode (micro LED) device.

11. The method according to claim 8, wherein the liquid conductive material comprises a metal.

12. The method according to claim 11, wherein the liquid conductive material comprises gallium.

13. The method according to claim 8, further comprising the steps of monitoring an electrical signal from the test probe and determining whether electrical contact with the contact point has been made based on the monitored electrical signal.

14. The test probe is one of a plurality of test probes of a test device, the sample is one of an array of samples, and the steps of lowering, removing, positioning, and driving are performed using each test probe of the plurality of test probes to electrically couple each test probe to a respective contact point of each sample of the array of samples to drive the excitation of each sample, the method according to claim 8.

15. An apparatus for testing a device under test (DUT) comprising a plurality of individual devices, the apparatus comprising: an array of probes; an alignment system for aligning the DUT and the array of probes relative to each other; a detection system configured to detect signals from the plurality of individual devices and the apparatus is configured to perform a test by scanning the electrical contacts of a plurality of sets of individual devices among the plurality of devices and driving the electrical excitation of the electrical contacts at the same time.

16. The scan includes moving the array of probes relative to the DUT by moving at least one of the array of probes and the DUT, and by this movement the array of probes contacts respective sets of electrical contacts for each set of individual devices of the plurality of sets of individual devices, the apparatus according to claim 15.

17. By repeatedly moving, the array of probes contacts respective sets of electrical contacts for each set of individual devices, and by the movement the array of probes (i) contacts one set of electrical contacts for one set of individual devices of the plurality of sets of individual devices, then (ii) becomes non-contact with the one set of electrical contacts for the one set of individual devices, and then (iii) contacts another set of electrical contacts for another set of individual devices of the plurality of sets of individual devices, the apparatus according to claim 16.

18. The scan includes scanning the DUT under the array of probes, the apparatus according to claim 15.

19. The alignment system is further for leveling the DUT relative to the array of probes, the apparatus according to claim 15.

20. The signal includes an optical signal, an electrical signal, or an electrochemical signal from an individual device, and the tool is further configured to detect the optical signal, the electrical signal, or the electrochemical signal using a detection system, the apparatus according to claim 15.

21. A memory; and A processor in communication with the memory A computer system comprising, controlling a test tool comprising a plurality of electrically conductive test probes, Positioning the plurality of test probes relative to a first plurality of contact points of a sample array associated with a first plurality of individual samples of the sample array such that the plurality of test probes are in electrical contact with the sample array at the first plurality of contact points; Driving parallel electrical excitation of a first plurality of individual samples by one or more electrical signals transmitted to a first plurality of contact points via a plurality of test probes, wherein electrical contact between the plurality of test probes and the first plurality of contact points is continuously maintained while performing the step of driving parallel excitation of the first plurality of individual samples, and a first value regarding testing of the first plurality of individual samples is generated by parallel excitation of the first plurality of individual samples; Moving at least one of the plurality of test probes and the sample array to move the plurality of test probes relative to the sample array, and based on this movement, positioning the plurality of test probes relative to the next plurality of contact points so that the plurality of test probes are in electrical contact with the next plurality of contact points associated with the next plurality of individual samples of the sample array; Driving parallel electrical excitation of a next plurality of individual samples by one or more electrical signals transmitted to the next plurality of contact points via the plurality of test probes, wherein electrical contact between the plurality of test probes and the next plurality of contact points is continuously maintained while performing the step of driving parallel excitation of the next plurality of individual samples, and a second value regarding testing of the next plurality of individual samples is generated by parallel excitation of the first plurality of individual samples; A computer system configured to implement a method comprising the above steps. Claim 22 The computer system according to claim 21, wherein the individual sample is a micro light emitting diode (micro LED) device. Claim 23 The computer system according to claim 21, wherein the step of driving parallel electrical excitation of the first plurality of individual samples is performed without using active feedback for continuously maintaining electrical contact between the plurality of test probes and the first plurality of first contact points while performing the step of driving parallel electrical excitation of the first plurality of individual samples. Claim 24 The method further includes observing luminescence from a first plurality of individual samples based on an interaction between a plurality of test probes and a first plurality of contact points, and confirming that electrical contact has been made between the plurality of test probes and the first plurality of contact points based on the luminescence, wherein the driving step is performed in response to the confirming step. The computer system according to claim 21.

25. The method further includes observing a reflected signal from a plurality of test probes as part of positioning the plurality of test probes relative to a first plurality of contact points, and confirming that electrical contact has been made between the plurality of test probes and the first plurality of contact points based on the observed reflected signal, wherein the step of driving parallel electrical excitation of the first plurality of individual samples is performed in response to the confirming step. The computer system according to claim 21.

26. At least a portion of each of the plurality of test probes is made of a translucent material. The computer system according to claim 21.

27. The plurality of test probes includes an array of test probes in which the spacing between the test probes is equidistant. The computer system according to claim 21.

28. A memory; and A processor in communication with the memory A computer system comprising: Controlling a test tool comprising a plurality of electrically conductive test probes to Submerging at least a portion of the electrically conductive test probes of the test device into a liquid conductive material; Removing at least a portion of the submerged test probes from the liquid conductive material, such that a portion of the liquid conductive material remains at the end of the test probe and is in electrical contact with the electrically conductive portion of the test probe; Positioning the test probes relative to the contact points of the sample such that a portion of the liquid conductive material at the end of the test probe physically contacts the contact points of the sample; Driving the excitation of the sample by an electrical signal transmitted through the portion of the liquid conductive material at the end of the test probe and through the test probe to the contact points A computer system configured to implement a method including the above steps.

29. The step of positioning positions the end of the test probe relative to the contact point such that the end of the test probe and the contact point are physically spaced apart, and a portion of the liquid conductive material occupies at least the space between the end of the test probe and the contact point and electrically bridges the electrically conductive portion of the test probe and the contact point, the method according to claim 28.

30. The computer system according to claim 28, wherein the sample is a micro light emitting diode (micro LED) device.

31. The computer system according to claim 28, wherein the liquid conductive material comprises a metal.

32. The computer system according to claim 31, wherein the liquid conductive material comprises gallium.

33. The computer system according to claim 28, wherein the method further comprises monitoring an electrical signal from the test probe and determining whether electrical contact with the contact point has been made based on the monitored electrical signal.

34. The test probe is one of a plurality of test probes of a test device, the sample is one of an array of samples, and the steps of lowering, removing, positioning, and driving are performed using each of the plurality of test probes to electrically couple each test probe to the respective contact point of each sample of the array of samples to drive excitation of each sample, the computer system according to claim 28.

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