Test System

Abstract

To provide a test system for testing a device having a plurality of electrical contacts.SOLUTION: A test system is provided, comprising: a device table operable to hold at least one device under test; a probe comprising at least one probe end for contacting electrical contacts of the device under test; a movement mechanism operable to move one or both of the device table and the probe so as to bring the at least one probe end into contact with at least one electrical contact of the device under test; and a profile determination system configured to determine a profile of the electrical contacts of the device under test.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a test system, and more particularly to a test system for testing the integrity of electronic devices. [Background technology]

[0002] The electronic device to be tested may include, for example, a semiconductor device (e.g., an integrated circuit). After the electronic device is manufactured, it is desirable to test the device. For example, the integrity of one or more circuits within the electronic device may be tested.

[0003] A method for testing an electronic device may include, for example, inputting an electronic signal (e.g., a pulse signal) into the device and measuring any reflection of the signal from the device. If the device contains an open or short circuit in its circuit, the signal input to the device will be at least partially reflected. If the device does not have any defects, little or none of the input signal will be reflected from the device. Therefore, measurements of the reflected signal from a device under test (DUT) can be used to test the integrity of the device and detect any defects within the device.

[0004] Test systems suitable for testing DUTs have been previously proposed, for example, in US20140021963, the entire contents of which are incorporated herein by reference.

[0005] It is an object of the present invention to provide an improved testing system that obviates or mitigates one or more problems of the prior art, whether or not specified herein. Summary of the Invention

[0006] According to a first aspect of the present invention, there is provided a test system for testing a device having a plurality of electrical contacts, the test system comprising: a device table operable to hold at least one device under test; a probe including at least one probe end for contacting the electrical contacts of the device under test; a movement mechanism operable to move one or both of the device table and the probe to bring the at least one probe end into contact with the at least one electrical contact of the device under test; and a profile determination system configured to determine a profile of the electrical contacts of the device under test.

[0007] The profile determination system may be configured to determine a three-dimensional profile of the electrical contacts of the device under test. The determined profile may include multiple locations at which surfaces of the electrical contacts are disposed. For example, the determined profile may include determined heights of the electrical contacts at different locations on the device under test. The profile determination system may be configured to determine a profile of the device under test that includes an area of ​​the device under test disposed between the electrical contacts. The profile may include, for example, heights of the device under test at different locations on the device under test.

[0008] The location, size, and / or shape of the electrical contacts of the device under test may vary for different devices and may not be known before testing the device. The profile of the electrical contacts of the device under test determined by the profile determination system may be used to determine a position (relative to the device table) to which the probe should be moved so that the probe end makes contact with the electrical contact of the device under test. A movement mechanism may move one or both of the device table and the probe to the determined position so that the probe end makes contact with the electrical contact. This may allow an automated process to be performed in which the probe can be connected to the electrical contact to test the device through the electrical contact.

[0009] An automated process can significantly reduce the time required to test a device (compared to manually moving probes to contact electrical contacts). In some embodiments, a movement mechanism can move one or both of the device table and the probes to contact multiple different electrical contacts at different times. This can allow a device to be tested through multiple different electrical contacts. In such embodiments, the time required to test a device through multiple different electrical contacts is significantly reduced by the automated system for contacting the ends of the probes to the electrical contacts.

[0010] The movement mechanism may be operable to translate one or both of the device table and the probe and / or to rotate one or both of the device table and the probe. In general, the movement mechanism may be operable to perform any movement of the device table and / or the probe that changes the position and / or orientation of the device table and / or the probe.

[0011] The probe may include at least two probe ends, and the movement mechanism may be operable to bring the at least two probe ends into contact with at least two electrical contacts of the device under test, and the at least two probe ends may be in contact with the at least two electrical contacts simultaneously.

[0012] The device under test may include a ground plate. The ground plate may be a separate element from the rest of the device and may be placed on the device for purposes of testing the device. A ground plate located on a device is considered to form part of the device under test. Furthermore, the ground plate is considered to be an example of an electrical contact on the device under test that the probe end may contact. As used herein, any reference to contacting an electrical contact on the device under test is intended to include contacting a ground plate located on the device.

[0013] The profile determination system may include a radiation source configured to irradiate at least a portion of the device under test with radiation, a radiation sensor configured to detect radiation scattered from electrical contacts of the device under test, and a controller configured to determine a profile of the electrical contacts of the device under test from the detected scattered radiation.

[0014] Radiation scattered from different parts of the device under test may appear at different locations within the field of view of the radiation sensor. The controller may determine the locations on the device under test from which the radiation is scattered from the locations within the field of view from which the scattered radiation appears. This may allow the location and / or shape of the scattering surface of the device under test to be determined.

[0015] The radiation sensor may be positioned so that different portions of the device under test that extend away from the device table by different amounts appear at different positions within the field of view of the radiation sensor.

[0016] This ensures that radiation scattered from different distances from the device table will appear at different positions within the field of view of the radiation sensor. The positions within the field of view at which the scattered radiation appears therefore allow the distance from the device table at which the radiation is scattered to be determined. This allows the heights of different points on the device under test to be determined and therefore a profile of the device under test can be derived.

[0017] The radiation sensor may be oriented at an oblique angle relative to the direction of propagation of the radiation emitted from the radiation source.

[0018] The radiation source may be configured to illuminate the strip of devices under test with a radiation strip.

[0019] The radiation sensor may be configured to detect radiation scattered from electrical contacts located within the radiation strip, and the controller is configured to determine the height of a point on the device under test located within the illuminated strip of the device under test.

[0020] The movement mechanism may be operable to move one or both of the device table and the radiation source to scan the radiation strip on the device under test, and the controller is configured to combine the determined heights of points on the device under test at different positions on the radiation strip to determine a profile of the electrical contacts of the device under test.

[0021] The device table may include a plurality of reference structures extending out of or into the device table, and the profile determination system is configured to determine the position of the profile of the electrical contacts of the device under test relative to the position of the reference structures.

[0022] The reference structure provides a known reference point against which the positions of the electrical contacts of the device under test can be determined. Knowledge of the positions of the electrical contacts relative to the reference structure allows the positions to which the probes should be moved to make contact with the electrical contacts to be determined.

[0023] The reference structures may extend from the device table, with at least two of the reference structures extending outside the device table by different distances.

[0024] The movement mechanism may be operable to move one or both of the device table and the probes so that at least one of the probe ends contacts one of the reference structures.

[0025] The test system may further comprise a calibration system configured to enable determination of the position of the at least one probe tip relative to a reference structure.

[0026] Determining the position of the probe end relative to the reference structure allows the probe end to be precisely brought into contact with the reference structure. This provides a reference point for known configurations of the motion mechanism that result in known positions of the probe relative to the device table. This may allow other configurations of the motion mechanism to be determined that result in other positions of the probe relative to the device table. With knowledge of the positions of the electrical contacts relative to the device table, the probe can be precisely moved to contact the desired electrical contacts.

[0027] The calibration system may be the same as the profile determination system. For example, the position of the at least one probe tip relative to the reference structure may be determined using the same procedure as determining the profile of the electrical contacts. Alternatively, a different procedure may be used. For example, the calibration system may include a camera or microscope that may be used to directly observe the position of the probe tip relative to the reference structure.

[0028] The movement mechanism can be adjusted manually while viewing (eg, through a camera or microscope) the position of the probe end relative to the reference structure until the probe end is brought into contact with the reference structure.

[0029] In some embodiments, the calibration system may include means for detecting contact between the probe tip and the reference structure. For example, the calibration system may include an electrical continuity tester that detects electrical continuity between the probe tip and the reference structure. The calibration system may also include one or more pressure sensors on the probe and / or the reference structure that are configured to detect contact between the probe tip and the reference structure.

[0030] The profile determination system may be further configured to determine the position of the probe tip relative to the electrical contacts of the device under test.

[0031] This may allow the position of the probe relative to the device under test and / or the device table to be determined, which allows the calibration of the position of the probe relative to the device table to be updated during the test procedure for testing the device under test.

[0032] The profile determination system may, for example, determine the position of the probe tip relative to the electrical contacts of the device under test when the probe tip is in proximity to the electrical contacts.

[0033] The test system further comprises a controller configured to determine, from the determined profile of the electrical contacts of the device under test, a configuration of a movement mechanism for bringing at least one probe tip into contact with at least one electrical contact of the device under test.

[0034] According to a second aspect of the present invention, there is provided a test system for testing a device having a plurality of electrical contacts, the test system comprising: a device table operable to hold at least one device under test; a probe including at least one probe end for contacting the electrical contacts of the device under test; and a movement mechanism operable to move one or both of the device table and the probe to bring the at least one probe end into contact with the at least one electrical contact of the device under test, wherein the device table includes a plurality of reference structures extending outside or into the device table.

[0035] The reference structure provides a reference point at a known location on the device table. Calibration can be performed to determine the position of the electrical contacts of the device under test and the position of the probe tip relative to the reference structure. Determining the positions of the electrical contacts and the probe tip relative to the reference structure allows the position of the probe tip relative to the electrical contacts to be determined. This allows a movement mechanism to move one or both of the device table and the probe to accurately contact the probe tip with the electrical contact, thereby allowing the probe to test the device under test through the electrical contacts.

[0036] The device table may include at least three reference structures. In some embodiments, the device table may include more than three reference structures, for example, eight reference structures.

[0037] The probe may include at least two probe ends, and the movement mechanism may be operable to bring the at least two probe ends into contact with at least two electrical contacts on the device under test, and the at least two probe ends may be in contact with the at least two electrical contacts simultaneously.

[0038] The device under test may include a ground plate. The ground plate may be a separate element from the rest of the device and may be placed on the device for purposes of testing the device. A ground plate located on a device is considered to form part of the device under test. Furthermore, the ground plate is considered to be an example of an electrical contact on the device under test that the probe end may contact. As used herein, any reference to contacting an electrical contact on the device under test is intended to include contacting a ground plate located on the device.

[0039] At least two of the reference structures extend different distances outside or into the device table.

[0040] At least two reference structures that extend different distances out of or into the device table advantageously improve the accuracy with which the positions of features (e.g., electrical contacts and one or more probe tips) can be determined relative to the reference structures. In some embodiments, the reference structures may all extend approximately the same distance out of or into the device table. However, in such embodiments, accurately contacting electrical contacts located at different heights may depend on the accuracy and linearity of the profile determination system. By placing the reference structures at different heights (i.e., extending different distances out of or into the device table), fiducials at different heights may be obtained. This may allow any nonlinearity or scaling errors in the profile determination system to be compensated for, and may improve the accuracy with which electrical contacts located at different heights are contacted.

[0041] The distance that the reference structure extends out of or into the device table may be referred to as the height of the reference structure. The area of ​​the device table configured to support at least one device under test may be located substantially within the support surface. The distance that the reference structure extends out of or into the device table may be the distance perpendicular to the support surface. In some embodiments, the reference structure may extend from the support surface, and the distance that the reference structure extends out of or into the device table may be the distance the reference structure extends from the support surface. In other embodiments, the reference structure may extend from a plane other than the support surface. For example, the reference structure may be positioned at a different vertical level relative to the support surface. The reference structure may extend from a plane substantially parallel to the support surface. The distance that the reference structure extends out of or into the device table may be the distance the reference structure extends from a plane substantially parallel to the support surface.

[0042] The movement mechanism may be operable to move one or both of the device table and the probes so that at least one of the probe ends contacts one of the reference structures.

[0043] The movement mechanism can be manually operated to bring the probe tip into contact with the reference structure. For example, the probe tip and the reference structure can be viewed through a camera or microscope, and the movement mechanism can be manually operated while viewing the probe tip and the reference structure through the camera or microscope. The movement mechanism can be guided to bring the probe tip into contact with the reference structure.

[0044] The test system may further comprise a calibration system configured to enable determination of the position of the at least one probe tip relative to a reference structure.

[0045] As explained above, with reference to the first aspect, determining the position of the probe end relative to the reference structure allows the probe end to be precisely contacted with the reference structure. This provides a reference point for known configurations of the movement mechanism that result in known positions of the probe relative to the device table. This may allow other configurations of the movement mechanism that result in other positions of the probe relative to the device table to be determined. With knowledge of the positions of the electrical contacts relative to the device table, the probe can be precisely moved to contact the desired electrical contacts.

[0046] For example, the calibration system may comprise a camera or microscope that can be used to directly observe the position of the probe tip relative to a reference structure. Alternatively, the calibration system may comprise a profile determination system as described in relation to the first aspect.

[0047] In some embodiments, the calibration system may include means for detecting contact between the probe tip and the reference structure. For example, the calibration system may include an electrical continuity tester that detects electrical continuity between the probe tip and the reference structure. The calibration system may also include one or more pressure sensors on the probe and / or the reference structure that are configured to detect contact between the probe tip and the reference structure.

[0048] At least one of the reference structures may include a reference feature indicating a reference point on the reference structure, and the movement mechanism is operable to move one or both of the device table and the probes so that at least one of the probe ends contacts the reference point.

[0049] The reference feature provides a more precise positional reference point to which the probe tip can be precisely moved. This increases the accuracy of the measurement of the probe's position relative to the device table. The reference feature provides a point on the reference structure that can be resolved by inspection (direct visual inspection or inspection by an inspection device (e.g., camera or microscope)). This allows the probe tip to be guided into contact with the reference point.

[0050] The reference features may be provided on a convex or protruding surface of the reference structure, which may reduce the chance of the probe tip being unintentionally brought into contact with other areas of the reference structure.

[0051] The reference feature may, for example, comprise a circular groove in the reference structure, and the probe tip may be brought into contact with a reference point within the area surrounded by the circular groove. The reference feature may, for example, surround an apex of the reference structure. For example, in an embodiment where the reference structure includes a circular groove in the reference structure, the circular groove may extend around the apex of the reference structure. The reference feature is located substantially at the apex of the reference structure and indicates a reference point within the circular groove. The probe tip may be brought into contact with the apex (i.e., the reference point) of the reference structure.

[0052] The reference feature may have a dimension approximately equal to the size of the probe end.

[0053] The reference feature may comprise a substantially circular groove formed in the reference structure that extends around an apex of the reference structure.

[0054] The reference structure may include a plurality of substantially circular grooves formed in the reference structure, each groove extending around an apex of the reference structure.

[0055] At least one of the reference structures may include a substantially spherical tip portion.

[0056] The spherical tip portion is surrounded by a substantially flat rim.

[0057] At least one of the reference structures comprises a surface having roughness features on the scale of 50 microns or less.

[0058] The roughness features may, for example, comprise ridges machined into the surface of the reference structure.

[0059] The device table may be operable to hold a number of devices under test.

[0060] The test system further includes a kinematically constrained mount to which the device table is attached, the kinematically constrained mount configured to constrain movement of the device table in multiple degrees of freedom.

[0061] A kinematically constrained mount may, for example, restrict the motion of the device table in six degrees of freedom.

[0062] The test system may further comprise a loading device operable to automatically load and unload devices under test from the device table.

[0063] The test system further comprises a signal generator configured to generate a signal and direct the signal through at least one of the probe ends so that, in use, the signal is directed to a device under test through electrical contacts of the device under test, and a signal sampler configured to sample the signal passing through at least one of the probe ends so that, in use, the signal reflected at the device under test and passing through the probe end is sampled by the signal sampler.

[0064] The signal generator may be configured to generate a broadband signal having frequency components in the range of 0.01 GHz to 10 THz.

[0065] A broadband signal may have only frequency components below about 1 THz. A broadband signal need not necessarily have frequency components spanning the entire range specified herein, but may simply have frequency components occupying a small region of the range specified herein. For example, a broadband signal may, in some embodiments, be limited to frequency components in the range of about 0.25 GHz to 200 GHz. Such a signal would be considered an example of a broadband signal having frequency components in the range of 0.01 GHz to 10 THz.

[0066] The signal generator may include a pulsed radiation source, a first signal converting device positioned to receive radiation pulses from the pulsed radiation source and configured to output signal pulses in response to irradiation from the pulsed radiation source, and a transmission line arrangement configured to direct the signal pulses from the first signal converting device through at least one of the probe ends.

[0067] The first signal conversion device may be configured to generate an electrical signal based on the optical signal. The first signal conversion device may comprise, for example, a photoconductive element. Alternatively, the first signal conversion device may comprise an electro-optical device.

[0068] The signal sampler may include a second signal conversion device arranged to receive radiation pulses from the pulsed radiation source and sample the signal pulses received at the second signal conversion device in response to irradiation from the pulsed radiation source, and the transmission line configuration is configured to guide signal pulses reflected from or transmitted through the device under test and passed through at least one of the probe ends to the second signal conversion device.

[0069] The second signal converting device may be configured to generate an electrical signal based on the optical signal. The second signal converting device may include, for example, a photoconductive element. Alternatively, the second signal converting device may include an electro-optical device. The pulsed radiation source may include a single radiation source, or may include separate radiation sources for illuminating the first and second signal converting devices. For example, the pulsed radiation source may include a first laser configured to illuminate the first signal converting device and a second laser configured to illuminate the second signal converting device.

[0070] According to a third aspect of the present invention, there is provided a test system for testing a device, the test system comprising: a pulsed radiation source configured to provide a generated radiation beam and a received radiation beam, wherein the generated radiation beam and the received radiation beam are pulsed radiation beams; a first signal conversion device arranged to receive pulses of the generated radiation beam and configured to output signal pulses in response to receiving the pulses of the generated radiation beam; a second signal conversion device arranged to receive pulses of the received radiation beam and configured to sample the signal pulses in response to receiving the pulses of the received radiation beam; and a signal conversion device configured to guide the signal pulses from the first signal conversion device to a device under test and to convert the signal pulses reflected from the device under test back through the device under test. a transmission line arrangement configured to introduce an optical delay between the generated radiation beam and the received radiation beam and direct it to a second signal conversion device; and a direct drive delay line arranged in the optical path of the generated radiation beam and / or the received radiation beam, the delay line configured to introduce an optical delay between the generated radiation beam and the received radiation beam, such that pulses of the generated radiation beam are incident on the first signal conversion device at a different time than corresponding pulses of the received radiation beam that are incident on the second signal conversion device, the delay line including at least one reflector arranged in the optical path of the generated radiation beam and / or the received radiation beam, and a synchronous linear motor configured to move the reflector and change the optical path length of the generated radiation beam and / or the received radiation beam to change the optical delay between the generated radiation beam and the received radiation beam.

[0071] A direct-drive delay line including a synchronous linear motor enables high-speed scanning of the delay line, allowing reflections and / or transmissions from a device under test at multiple different time delays relative to an input signal pulse to be rapidly analyzed. A direct-drive delay line can be operated to scan the delay time at a speed comparable to that of, for example, a galvanometer-driven delay line. However, a direct-drive delay line can scan a larger range of delay times than a galvanometer-driven delay line, thereby eliminating the need for separate fast-scan and slow-scan delay lines. The overall acquisition time of measurements can be significantly improved relative to prior art configurations. For example, the acquisition time can be as much as 60 times faster than that achievable with prior art configurations.

[0072] The synchronous linear motor may be a brushless motor.

[0073] The first and / or second signal conversion devices may be configured to generate an electrical signal based on the optical signal. The first and / or second signal conversion devices may comprise, for example, photoconductive elements. Alternatively, the first and / or second signal conversion devices may comprise electro-optical devices.

[0074] The pulsed radiation source may comprise a single radiation source and a beam splitter configured to split the output of the radiation source into the generated radiation beam and the received radiation beam. Alternatively, the pulsed radiation source may comprise separate radiation sources that emit the generated radiation beam and the received radiation beam, respectively. For example, the pulsed radiation source may include a first laser configured to emit the generated radiation beam and a second laser configured to emit the second radiation beam.

[0075] According to a fourth aspect of the present invention, there is provided a test system for testing a device, the test system comprising: a pulsed radiation source configured to provide a generated radiation beam and a received radiation beam, wherein the generated radiation beam and the received radiation beam are pulsed radiation beams; a first signal conversion device arranged to receive pulses of the generated radiation beam and configured to output signal pulses in response to receiving the pulses of the generated radiation beam; a second signal conversion device arranged to receive pulses of the received radiation beam and configured to sample the signal pulses in response to receiving the pulses of the received radiation beam; A test system is provided, comprising: a transmission line arrangement configured to direct signal pulses to a device under test and to direct signal pulses reflected from the device under test through the device under test to a second signal conversion device; a delay line including a first reflector positioned in the optical path of the generated radiation beam, a second reflector positioned in the optical path of the received radiation beam, and a movable stage to which the first reflector and second reflector are attached, wherein movement of the movable stage in a first direction increases the optical path length of the generated radiation beam and decreases the optical path length of the received radiation beam, and movement of the movable stage in a second direction decreases the optical path length of the generated radiation beam and increases the optical path length of the received radiation beam.

[0076] This configuration means that movement of the movable stage changes the optical path lengths of the generated and received radiation beams in opposite directions. As a result, moving the movable stage a first distance introduces a difference in the optical path lengths of the generated and received radiation beams that is at least twice the first distance. Therefore, a smaller movement of the movable stage is required to change the optical delay between the generated and received radiation beams by a given amount (relative to prior art configurations). This advantageously allows for faster scanning of the optical delay. Therefore, the acquisition time over which a given measurement is performed can be reduced. The movable stage can be moved by a motor (e.g., a synchronous linear motor).

[0077] The first and / or second signal conversion devices may be configured to generate an electrical signal based on the optical signal. The first and / or second signal conversion devices may comprise, for example, photoconductive elements. Alternatively, the first and / or second signal conversion devices may comprise electro-optical devices.

[0078] The pulsed radiation source may comprise a single radiation source and a beam splitter configured to split the output of the radiation source into the generated radiation beam and the received radiation beam. Alternatively, the pulsed radiation source may comprise separate radiation sources that emit the generated radiation beam and the received radiation beam, respectively. For example, the pulsed radiation source may include a first laser configured to emit the generated radiation beam and a second laser configured to emit the second radiation beam.

[0079] According to a fifth aspect of the present invention, there is provided a test system for testing a device, the test system comprising: a pulsed radiation source configured to supply a generated radiation beam and a received radiation beam, wherein the generated radiation beam and the received radiation beam are pulsed radiation beams; a first signal conversion device arranged to receive pulses of the generated radiation beam and configured to output a signal pulse in response to receiving the pulses of the generated radiation beam; a second signal conversion device arranged to receive pulses of the received radiation beam and configured to sample the signal pulse in response to receiving the pulses of the received radiation beam; a transmission line arrangement configured to guide the signal pulses from the first signal conversion device to a device under test and to guide the signal pulses reflected from the device under test through the device under test to the second signal conversion device; a radiation sensor configured to detect an intensity of the radiation pulses emitted from the pulsed radiation source; an attenuator arranged in an optical path of the radiation pulses emitted from the pulsed radiation source and configured to reduce the intensity of the radiation pulses by an adjustable amount; and a controller configured to adjust the amount by which the attenuator reduces the intensity of the radiation pulses in response to a measurement of the intensity of the radiation pulses by the radiation sensor.

[0080] The controller may adjust the attenuator so that the average power of the radiation pulse, determined over a time longer than a single pulse period, is substantially constant over time. The radiation pulse may, for example, be transmitted from a pulsed radiation source through an optical fiber to a radiation sensor. For example, changes in the coupling efficiency of the optical fiber result in changes in the intensity of the radiation received at the radiation detector, which is detected by the radiation sensor. The controller may, for example, respond to changes in the intensity measured by the radiation detector to compensate for any changes in the coupling efficiency of the optical fiber.

[0081] The controller may be, for example, a proportional-integral-derivative (PID) controller.

[0082] The first and / or second signal conversion devices may be configured to generate an electrical signal based on the optical signal. The first and / or second signal conversion devices may comprise, for example, photoconductive elements. Alternatively, the first and / or second signal conversion devices may comprise electro-optical devices.

[0083] The pulsed radiation source may comprise a single radiation source and a beam splitter configured to split the output of the radiation source into the generated radiation beam and the received radiation beam. Alternatively, the pulsed radiation source may comprise separate radiation sources that emit the generated radiation beam and the received radiation beam, respectively. For example, the pulsed radiation source may include a first laser configured to emit the generated radiation beam and a second laser configured to emit the second radiation beam.

[0084] Features of different aspects of the invention may be combined with features of other aspects of the invention.

[0085] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which: [Brief explanation of the drawings]

[0086] [Figure 1] 1 is a schematic diagram of an electronic device for testing using a test system according to one embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram of a probe that can be used to establish electrical contact with the electronic device of FIG. 1. [Figure 3A] FIG. 1 is a schematic diagram of an electronic device including a ground plate. [Figure 3B] FIG. 1 is a schematic diagram of an electronic device including a ground plate. [Figure 4] 1 is a schematic diagram of a portion of a test system that may form part of an embodiment of the present invention; [Figure 5] FIG. 1 is a schematic diagram of a portion of a test system that may form part of an alternative embodiment of the present invention. [Figure 6] 1 is a schematic diagram of a test system according to one embodiment of the present invention. [Figure 7] 7 is a schematic diagram of an example of a loading device that may form part of the test system of FIG. 6. [Figure 8] 1 is a schematic diagram of a portion of an electronic device shown in cross section. [Figure 9A] 7 is a schematic diagram of an embodiment of a profile determination system that may form part of the test system of FIG. 6. [Figure 9B] 7 is a schematic diagram of an embodiment of a profile determination system that may form part of the test system of FIG. 6. [Figure 10] FIG. 7 is a schematic diagram of a device table that may form part of the test system of FIG. 6. [Figure 11] 11A-11C are schematic diagrams of a reference structure that may form part of the device table of FIG. [Figure 12] 7 is a schematic diagram of an embodiment of a mount that may form part of the test system of FIG. 6. [Figure 13] 1 is a schematic diagram of a portion of a test system according to one embodiment of the present invention. [Figure 14] 1 is a schematic diagram of a delay line configuration that may form part of a test system in accordance with one embodiment of the present invention; [Figure 15] FIG. 1 is a schematic diagram of a radiation feedback system that may form part of a test system according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0087] 1 is a schematic diagram of an electronic device 1 that can be tested using a test system according to one embodiment of the present invention. The electronic device 1 may be referred to as a device under test (DUT). The DUT 1 includes a plurality of electrical contacts 3. The plurality of electrical contacts 3 may include, for example, a ball grid array (BGA), a land grid array (LGA), or a pin grid array (PGA). The DUT can be tested by simultaneously electrically contacting at least two of the electrical contacts 3 with a probe.

[0088] FIG. 2 is a schematic diagram of a probe 5 that can be used to establish electrical contact with the electrical contacts 3 of a DUT 1. The probe 5 includes a coaxial cable section 7 terminating in a first probe end 13 and a second probe end 15. The coaxial cable section 7 comprises an inner conductor 9 surrounded by an outer conductor 11 arranged in a coaxial transmission line configuration (the dotted line used to depict the inner conductor 9 indicates that the inner conductor 9 is surrounded by the outer conductor 11). The inner conductor 9 is electrically insulated from the outer conductor 11. Toward the end of the probe 7, the inner transmission 9 extends out of the outer conductor 11 and tapers to form the first probe end 13. The second probe end 15 is formed of a fin that extends out of the outer conductor 11 and is electrically coupled to the outer conductor 11.

[0089] To test DUT 1, first probe end 13 can contact first electrical contact 3 on DUT 1, and second probe end 15 can contact second electrical contact 3 on DUT 1. The inner conductor 9 and first probe end 13 can be used to input a signal to DUT 1 and can therefore be considered to carry a live current. The second probe end 15 and outer conductor 11 can be used to conduct a ground current. Alternatively, the inner conductor 9 can conduct a ground current and the outer conductor 11 can conduct a live current.

[0090] In some embodiments, a probe may have more than two probe ends. For example, a probe may have three probe ends. A probe with three probe ends may have one probe end that conducts a significant current and two probe ends that each conduct a ground current. Such a configuration may be referred to as a ground-signal-ground probe configuration.

[0091] In some embodiments, the DUT 1 may be provided with a ground plate that allows connection to ground. Figures 3A and 3B are schematic diagrams of the DUT 1 including a ground plate 2. Figure 3A shows the ground plate 2 separated from the rest of the DUT 1, while Figure 3B shows the ground plate 2 in contact with the rest of the DUT 1. The ground plate 2 includes openings 4 through which electrical contacts 3 can be accessed.

[0092] The ground plate 2 may have a laminated structure. For example, the ground plate 2 may have a conductive upper layer and an insulating lower layer. The conductive upper layer may include, for example, gold-plated copper. The insulating lower layer may include, for example, a polymer (e.g., polytetrafluoroethylene (PTFE)). The lower insulating layer acts to prevent electrical contact between the contacts 3 and the conductive upper layer.

[0093] 3B, DUT 1 may be tested by contacting first probe end 13 of probe 7 to electrical contact 3 and second probe end 15 to ground plate 2. Ground plate 2 may be a separate element from the device to be tested and may be placed on the device only to test the device. For example, ground plate 2 may be placed on a device to test an electrical contact that does not have a suitable adjacent contact to which the second probe end can be connected.

[0094] Although the ground plate may be a separate element from the device to be tested, for purposes of this description, the ground plate 2 disposed on the device will be considered to form part of the device under test DUT 1. Furthermore, the ground plate 2 will be considered to be an example of an electrical contact of the DUT 1 with which the probe ends 13, 15 may contact. As used herein, any reference to contacting an electrical contact 3 on the DUT 1 will include contacting the ground plate 2 disposed on the device.

[0095] FIG. 4 is a schematic diagram of a portion of a test system 15 that may form part of an embodiment of the present invention. Test system 15 includes a signal generator 17 and a signal sampler 19. Signal generator 17 may generate a wideband signal having frequency components in the range of, for example, 0.01 GHz to 10 THz. In some embodiments, the signal generator may generate a wideband signal having frequency components in the range of 0.25 GHz to 200 GHz. A wideband signal need not necessarily have frequency components spanning the entire range specified herein, but may simply have frequency components occupying a small region of the range specified herein. For example, a wideband signal having frequency components in the range of about 0.25 GHz to 200 GHz (but, for example, having no substantial frequency components at frequencies higher than about 200 GHz) would be considered an example of a wideband signal having frequency components in the range of 0.01 GHz to 10 THz.

[0096] A signal generator 17 generates a signal for input to the DUT 1. A signal sampler 19 receives and analyzes the signal reflected from the DUT 1. Both the signal generator 17 and the signal sampler 19 are connected to the probe 7 via a transmission line 21. The probe 7 may be similar to the probe 7 described above with reference to FIG. 2, for example, and will not be described in further detail with reference to FIG. 4. Like reference numbers in FIGS. 2 and 4 indicate like features of the probe 7.

[0097] A first probe end 13 of the probe 7 is connected to a first electrical contact 3 on the DUT 1. A second probe end 15 is connected to a second electrical contact 3 on the DUT 1. For simplicity of illustration, only two electrical contacts 3 are shown on the DUT 1 in Figure 4. However, it will be understood that the DUT 1 may include three or more electrical contacts 3.

[0098] The inner conductor 9 of the probe 7, electrically connected to the first probe end 13, is connected to a transmission line 21 that transmits a signal from the signal generator 17 to a signal sampler 19. Thus, the signal generated by the signal generator 17 is transmitted through the transmission line 21, the inner conductor 9 of the probe 7, and the first probe end 13 to the electrical contact 3 of the DUT 1. Any signal reflected at the DUT 1 can be transmitted through the first probe end 13, the inner conductor 9 of the probe 7, and the transmission line 21 to the signal sampler 19 for analysis.

[0099] The signal generator 17 includes a biasing element 16 and a first photoconductive element 23. The signal sampler 19 includes a measurement device 20 and a second photoconductive element 25. The first and second photoconductive elements are conductive in response to illumination by radiation and are substantially non-conductive when not illuminated by radiation. The first and second photoconductive elements 23, 25 can be selectively illuminated by radiation to generate a signal at the first photoconductive element 23 and sample a signal at the second photoconductive element 25. The signal generator 17 and the signal sampler 19 can be considered to form a sampling module 18 operable to input signal pulses to the DUT 1 through the probe 7 and receive signal reflections from the DUT 1.

[0100] The test system 15 further comprises a radiation source 27. The radiation source 27 emits radiation pulses in the form of a pulsed radiation beam 29. The radiation source 27 may comprise, for example, a laser. The radiation beam is incident on a beam splitter 31, which splits the pulsed radiation beam 29 into a generated beam 33 comprising the generated pulses and a received beam 35 comprising the received pulses. The generated beam 33 is directed to be incident on the first photoconductive element 23, and the received beam 35 is directed to be incident on the second photoconductive element 25.

[0101] The pulse generating beam 33 causes a signal pulse to be generated in the first photoconductive element 23 and input to the DUT 1. The biasing element 16 applies a potential to the first photoconductive element 23. For example, the biasing element 16 may apply a DC potential or an AC potential (e.g., having a frequency of about 30 KHz) to the first photoconductive element 23. When a radiation pulse is incident on the first photoconductive element 23, a signal pulse is generated in the first photoconductive element 23 due to a combination of the biasing element 16 and the illumination of the first photoconductive element 23. Thus, the first photoconductive element operates to generate an electrical signal based on the optical signal.

[0102] The pulsed receive beam 35 acts to sample the electrical signal received at the second photoconductive element 25 at selected times (when the second photoconductive element 25 receives a radiation pulse). The sampled signal at the second photoconductive element 25 is measured by the measurement device 20. The second photoconductive element 25 can be thought of as generating an electrical signal (which is measured by the measurement device 20) based on the optical signal (provided by the receive beam 35). The electrical signal generated at the second photoconductive element 25 is in turn based on the signal reflected from the DUT 1. This process can be referred to as sampling the signal.

[0103] The optical path of the receive beam 35 relative to the second photoconductive element 25 includes a delay line 37 configured to introduce an optical delay between a generated pulse in the generate beam 33 and a received pulse in the receive beam 35. The optical delay introduced by the delay line 37 causes the generated pulse to be incident on the first photoconductive element 23 at a different time than the corresponding received pulse incident on the second photoconductive element 25. As a result, there is a delay between the signal pulse sent to the DUT 1 (from the signal generator 17) and the reflected signal sampled by the second photoconductive element 25 and received by the measurement device 20.

[0104] The delay time between the input signal pulse and the reflection sampled by the signal sampler 19 can be adjusted to analyze reflections from the DUT 1 at different delay times after the pulse is input to the DUT 1. The delay line 37 includes a movable stage 39 to which a reflector in the optical path of the receive beam 35 is attached. Movement of the movable stage 39 (indicated by the two-headed arrow in FIG. 4 ) changes the optical path length of the receive beam 35 and therefore changes the optical delay between the generated pulse 33 incident on the first photoconductive element 23 and the received pulse incident on the second photoconductive element 25. The movable stage 39 can be scanned, for example, to analyze reflections from the DUT 1 at different delay times.

[0105] It should be understood that the components shown in Figure 4 are not drawn to scale. Test system 15 may include different components than those shown in Figure 4 and described above and / or may include additional components to those described and shown. Details of other examples of test systems are provided in US20140021963, which is incorporated herein by reference in its entirety. Any of the features disclosed in US20140021963 may be used with the test systems described herein.

[0106] As described above, the first photoconductive element 23 and the second photoconductive element 25 generate an electrical signal based on an optical signal. The first and second photoconductive elements 23, 25 may be considered examples of signal conversion devices. In some embodiments, signal conversion devices other than photoconductive elements may be used. For example, the first and / or second photoconductive elements 23, 25 may be replaced by other forms of signal conversion devices.

[0107] An alternative signal conversion device that may form part of an embodiment of the present invention may be an electro-optical device, such as an electro-optical crystal. The electro-optical crystal forming part of the signal generator may be configured to receive a polarized radiation beam (e.g., generated beam 33) and generate an electrical signal based on the polarized radiation beam.

[0108] The electro-optic crystal forming part of the signal sampler may be configured such that its optical properties change in response to exposure to an electric field. For example, the birefringence of the crystal may change in response to exposure to an electric field. An electrical signal incident on the electro-optic crystal from DUT1 exposes the crystal to an electric field. A receive beam 35 may be directed to be incident on the electro-optic crystal, and the receive beam 35 transmitted by the crystal may be detected by one or more sensors. A change in the optical properties (e.g., birefringence) of the crystal may induce a change in the receive beam 35 transmitted by the crystal, which may be detected by one or more sensors. For example, the signal from DUT1 may act to alter the polarization state and / or amplitude of the receive beam 35 transmitted by the crystal. For example, the change in polarization state and / or amplitude may be measured using, for example, polarizing optics and one or more photodiode sensors. This may result in a measurement signal proportional to the signal received from DUT1.

[0109] Similar to the operation of the photoconductive element described above, an electro-optic crystal can be used in conjunction with pulsed generating and receiving beams 33, 35 to generate signal pulses at selected times and sample the reflected signals. An optical delay can be introduced between the generating beam 33 and receiving beam 35, allowing reflections received at different delay times to be analyzed (as described above with reference to the embodiment including a photoconductive element).

[0110] In some embodiments, different types of signal conversion devices may be used in signal generator 17 and signal sampler 19. For example, a photoconductive element may be used in signal generator 17 and an electro-optic crystal may be used in signal sampler 19.

[0111] Although embodiments have been described above in which radiation beam 29 is emitted from radiation source 27 and split into generation beam 33 and receive beam 35, in some embodiments, separate radiation sources may be used to generate the generation beam and receive beam. For example, in some embodiments, a dual laser system including two synchronized lasers may be used. The lasers may be controllably synchronized such that the optical delay between the radiation beams emitted from the two lasers is controlled and adjusted (e.g., electronically). In such embodiments, the synchronization between the lasers may be adjusted to analyze signals received at different delay times (as described above with reference to delay line 37). Since the function of the delay line can be replaced by adjusting the synchronization between the lasers, embodiments including a dual laser system may therefore not include a delay line. However, in some embodiments, a delay line may still be used with a dual laser system.

[0112] In embodiments including more than one radiation source (e.g., a dual laser system), the multiple radiation sources may be considered to together form a pulsed radiation source. A pulsed radiation source herein is intended to include a single radiation source or multiple radiation sources, such as, for example, a dual laser system. In embodiments where the pulsed radiation source includes a single radiation source, the pulsed radiation source may further comprise a beam splitter configured to split the radiation beam into a generated radiation beam and a received radiation beam.

[0113] In some embodiments, a DUT 1 may be tested using two or more probes 7 and two or more sampling modules 18. Figure 5 is a schematic diagram of a portion of a test system 15' including a first sampling module 18a and a second sampling module 18b. The first sampling module 18a is connected to a first probe 7a, and the second sampling module 18b is connected to a second probe 7b. Both the first and second probes 7a, 7b are brought into contact with electrical contacts 3 on the DUT 1.

[0114] The first and second sampling modules 18a, 18b are supplied with radiation emitted from a radiation source 27 (e.g., a laser). The radiation source 27 emits a radiation beam 29, which is split by a beam splitter 31 into a generated beam 33 and a received beam 35. The received beam 35 is directed to a delay line 37 operable to introduce an optical delay between the generated beam 33 and the received beam 35. The generated beam 33 is split by the beam splitter 31 into first and second portions 33a, 33b. The received beam 35 is split by the beam splitter 31 into first and second portions 35a, 35b. The first portion 33a of the generated beam and the first portion 35a of the received beam are supplied to the first sampling module 18a. The generated beam and the first and second portions of the received beam are coupled to an optical fiber 32 by a fiber coupler 34 and via a mirror 38. The second portion 33b of the generated beam and the second portion 35b of the received beam are provided to a second sampling module 18b.

[0115] In the configuration shown in FIG. 5, the first and second sampling modules 18a, 18b are driven using a common generating beam 33 and receiving beam 35. In this configuration, the sampling modules 18a, 18b can measure signals transmitted between the first and second probes 9A, 9B through the DUT 1 in addition to signals reflected at the DUT 1. By alternately selectively turning off pulse generation in each sampling module 18a, 18b, the reflected signal can be separated from the transmitted signal. For example, the first sampling module 18a can first generate a signal pulse. The transmission of the pulse can be measured by the second sampling module 18b, and the reflection of the pulse can be measured by the first sampling module 18a. Subsequently, the second sampling module 18b can generate a signal pulse. The transmission of the pulse can be measured by the first sampling module 18a, and the reflection of the pulse can be measured by the second sampling module 18b.

[0116] The measurements described above can be used to form a 2×2 matrix S that describes the coupling between two electrical contacts and is given by equation (1) below:

[0117]

number

[0118] element S 11 represents the signal injected at and reflected back to the first electrical contact. 22 represents the signal injected at and reflected back to the second electrical contact. 12 represents the signal injected at the first electrical contact and transmitted to the second electrical contact. 21 represents the signal injected at the second electrical contact and transmitted to the first electrical contact. The matrix S may be referred to as the S-parameter measurement or scattering matrix of DUT1.

[0119] In some embodiments, the test system may include three or more sampling modules and may simultaneously test DUT1 through two or more electrical contacts. In general, an N×N S-parameter matrix may be derived by sampling DUT1 through N electrical contacts.

[0120] 5 includes a delay line 37, it will be understood that the delay between the generated beam 33 and the received beam 35 can instead be introduced by using a dual laser system, as described above. A first laser emits the generated beam 33 and a second laser emits the received beam 35. The first and second lasers can be synchronized, and the synchronization between the lasers can be controlled to control the optical delay between the generated and received beams.

[0121] As described above, DUT 1 may be tested through one or more probes 7 that are brought into contact with one or more electrical contacts using a variety of different methods. A signal may be input to DUT 1, and the reflection and / or transmission of the signal by DUT 1 may be measured. In the examples described below, emphasis is placed on measuring signals reflected by DUT 1. However, it will be understood that similar principles apply to measuring transmitted signals. Thus, the following description may equally apply to measuring transmitted signals as opposed to measuring reflected signals.

[0122] It may be desirable to test the DUT 1 through several different electrical contacts 3. This can be achieved by moving the probe 7 and / or the DUT 1 so that the probe ends 13, 15 contact different electrical contacts 3. At each position of the probe 7 and the DUT 1, a signal pulse can be input to the DUT 1 through the probe 7 and the signal reflection from the DUT 1 can be analyzed at different delay times.

[0123] It would be desirable to provide an automatic or semi-automatic test system that automatically moves the probe and / or DUT 1 so that the probe ends contact different electrical contacts and the DUT 1 can be tested through the different electrical contacts. Providing an automatic or semi-automatic test system can significantly reduce the time required to test the DUT 1 (e.g., compared to manually contacting the probes with the electrical contacts). An automatic or semi-automatic test system may allow the DUT 1 to be rapidly tested through multiple electrical contacts 3. An automatic or semi-automatic test system may allow multiple DUTs 1 to be tested in rapid succession.

[0124] 6 is a schematic diagram of a test system 101 according to one embodiment of the present invention. The test system includes a device table 103 operable to hold at least one device 1. In some embodiments, the device table 103 may be operable to hold multiple devices 1. The device table 103 is positioned on a mount 104. The mount 104 is positioned on a motion stage 106. The multiple devices 1 may be held in, for example, a tray 105. The multiple trays 105 of devices 1 may be held in a tray holder 107. The trays 105 can be unloaded from the tray holder 107 (as shown in FIG. 6) to test one or more devices held on the trays 105.

[0125] The test system 101 further comprises a loading device 109 operable to automatically load and unload the device 1 from the device table 103. For example, the loading device 109 can move the device 1 from the tray 105 and load the device 1 onto the device table 103. After the device 1 is tested while held on the device table 103, the device 1 can be unloaded from the device table 103 and returned to the tray 105.

[0126] 7 is a schematic diagram of one embodiment of a loading device 109. The loading device 109 comprises a robot having a first arm 111, a second arm 113, and an actuator 115 disposed at the end of the second arm 113. The first arm 111, the second arm 113, and the actuator 115 are rotatable about a joint 117. Rotating the first arm 111, the second arm 113, and / or the actuator 115 about the joint 117 allows the actuator 115 to move between components. The loading device 109 has an outer reach indicated by a dashed line 119.

[0127] 7 also shows the tray 105, the first device table 103a, and the second device table 103b positioned on the mount 104. The loading device 109 is operable to load the device 1 from the tray 105 onto the device table 103a. In the depiction shown in FIG. 7, the loading device 109 is in the process of loading the device 1 from the tray 105 onto the device table 103a. The loading device 109 can move the device 1 by moving the actuator 115 to a position to pick up the device 1. The actuator 115 then clasps the device 1, and the device 1 can be moved by the actuator 115 to a different position for unloading.

[0128] In the embodiment shown in Figure 7, device tables 103a, 103b are each operable to hold six devices. Once device 1 is loaded onto device table 103, it can be loaded onto mount 104 where device 1 can be tested. Device table 103 can be moved onto mount 104 and loaded by, for example, loading device 109. As shown in Figure 7, first device table 103a can be loaded with a device while second device table 103b is positioned on mount 104 and device 1 on second device table 103b is tested. This can improve the throughput of test system 101. The throughput of a test system can be considered to be the number of devices tested per unit time.

[0129] Returning again to Figure 6, the test system 101 shown in Figure 6 further includes a pair of probes 7. Although not shown in detail in Figure 6, the probes 7 may be similar to the probe embodiments described above with reference to Figure 6. Each probe is connected to a sampling module 18. The sampling modules 18 are operable to input signal pulses to the DUT 1 through the probes 7 and receive signal reflections from the DUT 1, as described above with reference to Figure 4. The sampling modules 18 in the Figure 6 embodiment may be similar to the sampling modules 18 described above with reference to Figure 4 and may have any of the features of the sampling modules described herein.

[0130] In the embodiment shown in Figure 6, the sampling module is coupled to an optical fiber 121, the other end of which is coupled to a radiation source 27. As described above with reference to Figure 4, the radiation source 27 emits pulses of radiation that can be directed to be incident on a photoconductive element that forms part of the sampling module 18. Although not shown in Figure 6, the test system 101 may further comprise one or more delay lines configured to introduce an optical delay between the radiation pulses emitted from the radiation source 27. The operation of the radiation source 27 and the sampling module 18 will not be described in further detail with reference to Figure 6. As described above, alternative embodiments of the sampling module and / or radiation source may be used.

[0131] The probe 7 can be brought into contact with electrical contacts 3 (not shown in FIG. 6) on the DUT 1 through probe ends 13, 15 (not shown in FIG. 6) of the probe 7. The test system 101 includes a movement mechanism 122 operable to move one or both of the device table 103 and the probe 7 to bring the probe ends 13, 15 into contact with at least two electrical contacts 3 on the DUT 1. The movement mechanism is shown only schematically as a box 122 in FIG. 6, as it may take a variety of different forms and may include multiple components not shown in detail.

[0132] The movement mechanism 122 may include, for example, one or more actuators configured to move components of the test system 101. For example, the one or more actuators may be configured to move the probe 7 and bring the probe ends 13, 15 on the probe 7 into contact with the electrical contacts 3 on the DUT 1. Additionally or alternatively, the one or more actuators may be configured to directly move the device table 103 on which the DUT 1 is located. Additionally or alternatively, the one or more actuators may be configured to move the mount 104 on which the device table 103 that holds the DUT 1 is located. Additionally or alternatively, the one or more actuators may be configured to move the motion stage 106 on which the mount 104 is located. The movement mechanism may be operable to translate and / or rotate one or more components (e.g., the device table 103 and / or the probe 7). The movement mechanism may be operable to adjust the position and / or orientation of one or more components (e.g., the device table 103 and / or the probe 7).

[0133] It will be appreciated that in order to bring the probe ends 13, 15 of the probes 7 into contact with the electrical contacts 3 of the DUT 1, it is desirable to know the positions of the electrical contacts 3 to be contacted relative to the positions of the probe ends 13, 15. Knowledge of these positions allows the necessary movement of the probes 7 and / or the device table 103 on which the DUT 1 is positioned to make contact with the electrical contacts to be determined. However, the position, size, and / or shape of the electrical contacts 3 on the DUT 1 may differ for different devices and cannot be known prior to testing the device.

[0134] Figure 8 is a schematic diagram in cross section of a portion of a DUT 1. The DUT 1 includes a plurality of electrical contacts 3 (shown in Figure 8 as ball-type electrical contacts). Also shown in Figure 8 is a probe 7 that can be used to contact the electrical contacts 3. The probe 7 shown in Figure 8 is the same as the probe 7 described above with reference to Figure 2 and will not be described in further detail here.

[0135] As can be seen in FIG. 8 , the electrical contacts 3 do not all have the same size and shape. Furthermore, the pitch 123 between adjacent electrical contacts 3 is not consistent for each of the electrical contacts 3. The pitch 123 between adjacent contacts 3 may not match the pitch 125 between the probe ends 13, 15 of the probe 7. It may not be easy to find a position and orientation of the probe 7 relative to the DUT 1 where the probe ends 13, 15 simultaneously contact two electrical contacts of the DUT 1. For example, the probe 7 may be tilted relative to the DUT 1 to simultaneously contact two electrical contacts 3. The angle at which the probe 7 is tilted relative to the DUT 1 may be different when contacting different electrical contacts 3.

[0136] A configuration of the motion mechanism 122 that achieves contact can be determined to bring the probe ends 13, 15 into contact with the electrical contacts of the DUT 1. The motion mechanism 122 is operable to move one or both of the device table 103 and the probes 7 to adopt the determined configuration in which the probe ends 13, 15 of the probes 7 are in contact with the electrical contacts 3 on the DUT 1. References herein to movement of the device table 103 can include direct movement of the device table 103 or can include movement of another component on which the device table 103 is positioned. For example, movement of the mount 104 on which the device table 103 is positioned is an example of movement of the device table 103. Similarly, movement of the motion stage 106 on which the device table 103 is positioned is a further example of movement of the device table 103.

[0137] It may be desirable to have knowledge of the location, size, and / or shape of the electrical contacts of the DUT 1 in order to determine the configuration of the movement mechanism 122 that will bring the probe ends 13, 15 of the probes 7 into contact with the electrical contacts 3 of the DUT 1. Referring again to FIG. 6 , the test system 101 further includes a profile determination system 127. The profile determination system 127 is configured to determine a profile of the electrical contacts of the device. For example, the profile determination system may be configured to determine a three-dimensional profile of the electrical contacts of the device. The determined electrical contact profile is then used to determine the configuration of the movement mechanism 122 that will bring the probe ends 13, 15 of the probes 7 into contact with the electrical contacts 3 of the DUT 1.

[0138] An embodiment of the profile determination system 127 is shown in more detail in Figure 9. Figure 9A is a schematic diagram of one embodiment of the profile determination system 127 from a side view. Figure 9B is a schematic diagram of the device 1 from a top view, where the device 1 is illuminated with a radiation strip by the profile determination system 127.

[0139] The profile determination system 127 includes a radiation source 129, a radiation sensor 131, and a controller 133. The radiation source 129 is configured to irradiate at least a portion of the device under test with radiation 135. In the example shown in FIG. 9, the radiation source 129 is configured to irradiate a strip of the device 1 with the radiation strip 135. The radiation sensor 131 is configured to detect radiation scattered from the device 1. For example, the radiation sensor 131 may detect radiation scattered from electrical contacts 3 on the device 1. The controller is configured to determine a profile (e.g., a three-dimensional profile) of the electrical contacts of the device 1 from the detected scattered radiation.

[0140] The radiation source 129 may include, for example, one or more light-emitting diodes (LEDs). In some embodiments, the radiation source 129 may include a laser. However, lasers typically emit coherent radiation. The coherent radiation scattered from the device 1 may form an interference pattern (e.g., a speckle pattern) that is visible to the radiation sensor 131 and may result in measurements generated by the radiation sensor 131. The radiation emitted from an LED is typically less coherent than the radiation emitted from a laser. As a result, the use of one or more LEDs advantageously reduces the impact of any interference effects on the measurements generated by the radiation sensor 131.

[0141] 9, the radiation sensor 131 is oriented at an oblique angle α to the direction of propagation of the radiation 135 emitted from the radiation source 129. The radiation sensor 131 is positioned such that different parts of the device 1 having different heights appear at different positions within the field of view of the radiation sensor 131. The controller 133 may determine the positions on the device 1 from which the radiation is scattered, from the positions within the field of view of the radiation sensor where the scattered radiation appears. This may allow the position and / or shape of the scattering surface of the device under test to be determined.

[0142] 9, the radiation source 129 is configured to illuminate a strip of devices 1 with a radiation strip 135. The radiation sensor 131 is configured to detect radiation scattered from devices 1 located within the radiation strip (e.g., from electrical contacts of the devices 1). The controller 133 is configured to determine the height of points of devices located within the illuminated strip of devices 1.

[0143] The radiation strip 135 can be scanned on the device 1, as indicated by the double-headed arrow in FIG. 9B . For example, the movement mechanism 122 can move one or both of the device table 103 on which the device 1 is located and the radiation source 129 to scan the radiation strip 135 on the device 1. At each position of the radiation strip 135 on the device 1, the controller 133 determines the height of a point of the device 1 located within the radiation strip 135. The controller 133 combines the determined heights of the device 1 at different positions of the radiation strip 135 to determine a three-dimensional profile of the device 1. The profile of the device 1 includes the profiles of the electrical contacts 3 on the device 1.

[0144] In some embodiments, the radiation source 129 and the radiation sensor 131 may be positioned such that specular reflection from the electrical contacts 3 is received at the radiation sensor 131. This may increase the detection signal received at the radiation sensor 131 and therefore improve the accuracy of the profile determination. Such embodiments are particularly applicable to profiling devices that include a land grid array (LGA) of electrical contacts 3. The electrical contacts 3 that form a land grid array may have a relatively small height compared to other forms of electrical contacts. Therefore, the profile of the LGA may be difficult to detect. Detecting specular reflection from the LGA may improve the accuracy with which the LGA is profiled.

[0145] In some embodiments, the profile determination system 127 may include multiple radiation sources 129. A first radiation source may be oriented such that specular reflection from the electrical contacts 3 is received at the radiation sensor 131. The first radiation source may be used to profile devices 1 that include an LGA. A second radiation source may be oriented such that diffusely scattered radiation, rather than specular reflection, is received at the radiation sensor. The second radiation source may be used to profile devices that do not include an LGA.

[0146] In other embodiments, the profile determination system 127 may determine the profile of the electrical contacts 3 on the DUT 1 by means different from those described above with reference to FIG. 9 . For example, the profile determination system 127 may include a camera that acquires an image of the DUT 1 from above. Image processing may be performed on the acquired image to detect the positions of the electrical contacts 3 within the image. In some embodiments, the two-dimensional information regarding the positions of the electrical contacts 3 may be combined with information acquired from one or more additional sensors configured to provide information regarding the height of the DUT 1.

[0147] In some embodiments, the height of the electrical contacts 3 on the DUT 1 may be determined by illuminating the electrical contacts 3 with a radiation beam and measuring the return time of the radiation reflected from the electrical contacts 3. The return time may be used to determine the height of the electrical contacts 3. For example, the profile determination system 127 may include a laser configured to illuminate a portion of the DUT 1 with a laser beam and a radiation sensor positioned to measure the return time of the laser radiation reflected from the DUT 1. The controller may determine the height of a point on the DUT 1 based on the return time. The laser and / or the DUT 1 may be moved to illuminate different locations on the DUT 1 and determine the height of the DUT 1 at the different locations. The determined heights of the DUT 1 at different locations on the DUT 1 may be combined to form a profile of the DUT 1, including a profile of the electrical contacts 3 on the DUT 1.

[0148] In some embodiments, information about the height of the DUT 1 at different locations (e.g., obtained using a laser as described above) may be combined with information derived from acquired images of the DUT 1. For example, an image of the DUT 1 from which the positions of the electrical contacts 3 on the DUT 1 may be derived may be combined with the height information to determine the profile of the electrical contacts 3 on the DUT 1.

[0149] Although embodiments have been described in which a three-dimensional profile of the electrical contacts of the DUT 1 may be determined, in some embodiments, a two-dimensional profile may be sufficient. For example, if the DUT 1 includes a plurality of electrical contacts 3 arranged in a line, it may be sufficient to determine the height of the electrical contacts 3 as a function of position along the line, thereby determining the two-dimensional profile of the electrical contacts 3. In embodiments in which the DUT 1 includes a more complex arrangement of electrical contacts 3, it may be desirable to determine the three-dimensional profile of the electrical contacts 3.

[0150] In order to determine the configuration of the movement mechanism 122 that will bring the probe ends 13, 15 of the probe 7 into contact with the electrical contacts 3 of the DUT 1, it is desirable to know the position of the profile of the DUT 1 relative to the position of the probe 7. In some embodiments, this can be achieved by determining the position of the profile of the DUT 1 relative to the device table 103 on which the DUT 1 is held. The position of the probe 7 relative to the device table 103 can likewise be determined, thereby providing the position of the profile of the DUT 1 relative to the position of the probe 7.

[0151] When reference is made herein to the position of an element relative to the position of another element, it is intended to include the relative orientation of the two elements. For example, determining the position of the probe 7 relative to the device table 103 may include determining the relative orientation of the probe 7 and the device table 103.

[0152] Figure 10 is a schematic diagram of device table 103. Also shown in Figure 10 is the coordinate system used to describe the position and orientation of device table 103. Device table 103 can be translated in the x, y, and z directions, and rotated by an azimuthal angle φ about the x axis and a polar angle θ about the z axis.

[0153] The device table 103 includes device mounting positions 137 where devices 1 can be mounted on the device table 103. In the embodiment shown in Figure 10, the device table 103 includes six device mounting positions 137. In other embodiments, the device table 103 may include more or less than six device mounting positions 137.

[0154] The device 1 may be held in place on the device table 103 by vacuum clamping the device 1 to the device table 103. In the embodiment of Figure 10, the device mounting location 137 is provided with a vacuum port 139 operable to apply a vacuum to the underside of the device 1 to clamp the device to the device table 103.

[0155] The device table 103 shown in Figure 10 includes a gripping position 141. The gripping position 141 provides a contact point at which the device table 103 can be gripped to hold and move the device table 103. For example, the actuator 115 of the loading device 109 shown in Figure 7 can grip the device table 103 at the gripping position 141.

[0156] The device table 103 further includes a shorting pad 143, which provides a location where components can be shorted together. For example, both of the two probe ends 13, 15 can be brought into contact with the shorting pad 143, thereby shorting the two probe ends 13, 15. This can allow one or more reference measurements to be taken. For example, a measurement of the signal reflection from the shorted probe ends can be taken as a reference measurement. If the probe ends 13, 15 are not shorted together, another reference measurement can be taken. The shorting pad 143 can be, for example, gold plated.

[0157] The underside of the device table 103 is provided with attachment points 145. The attachment points 145 may be configured to interface with a mount 104 on which the device table 103 is disposed. The mount 104 may comprise a kinematically constrained mount. An example of a mount 104 on which the device table 103 may be disposed is described in further detail below with reference to FIG. 12.

[0158] The device table 103 further includes a reference structure 147. The reference structure 147 may, for example, be inserted into a hole in the device table 103. The reference structure 147 provides a reference point at a known position on the device table 103. The reference structure 147 may provide a reference position on the device table 103 against which the profile of the electrical contacts 3 on the DUT 1 may be measured. For example, the profile determination system 127 may determine a profile of the device table 103, which may include the profile of the electrical contacts 3 on the DUT 1 placed on the device table, as well as the profile of the reference structure 147 on the device table 103. The reference structure 147 may be identified in the determined profile. Because the reference structure 147 may be placed at a known position on the device table 103, identifying the reference structure 147 in the determined profile of the device table 103 may allow the position of the electrical contacts 3 on the DUT 1 placed on the device table 103 to be determined. The determined position of the electrical contact 3 on the device table 103 may enable the position to which the probe 7 should be moved relative to the device table 103 to contact the electrical contact 3 to be determined.

[0159] The reference structure 147 can extend outside the device table 103 (as shown in FIG. 10 ). In alternative embodiments, the reference structure 147 can extend into the device table 103 (e.g., the reference structure can be embedded within the device table 103). In the embodiment shown in FIG. 10 , the reference structure 147 is located at a different vertical level (i.e., a different position on the z-axis shown in FIG. 10 ) relative to the level at which the device 1 is supported. The device mounting location 137 configured to support the device 1 can be located substantially within the support surface. In the embodiment shown in FIG. 10 , the reference structure 147 extends from a plane substantially parallel to the support surface. In other embodiments, the reference structure 147 can extend from the support surface. The reference structure 147 can extend in a direction perpendicular to the support surface (as shown in FIG. 10 ).

[0160] At least two of the reference structures 147 may extend out of or into the device table 103 by different distances. For example, in some embodiments, all of the reference structures may extend out of or into the device table 103 by different distances. The distance that the reference structure 147 extends out of or into the device table 103 may be referred to as the height of the reference structure 147. The distance that the reference structure 147 extends out of or into the device table 103 may be the distance in a direction perpendicular to the support surface. In the embodiment of FIG. 10 , the distance that the reference structure 147 extends out of or into the device table 103 may be the distance that the reference structure 147 extends from a plane substantially parallel to the support surface. In embodiments in which the reference structure 147 extends from the support surface, the distance may be the distance that the reference structure 147 extends from the support surface.

[0161] Reference structures 147 that extend out of or into the device table by different distances advantageously improve the accuracy with which the positions of features (e.g., electrical contacts 3 on DUT 1) can be determined relative to the reference structures 147. In some embodiments, the reference structures may all extend out of or into the device table 103 by approximately the same distance. However, in such embodiments, accurately contacting electrical contacts 3 located at different heights may depend on the accuracy and linearity of the profile determination system 127. By placing the reference structures 147 at different heights (i.e., extending out of or into the device table 103 by different distances), references at different heights may be obtained. This may allow any nonlinearity or scaling errors in the profile determination system 127 to be compensated for, and the accuracy with which electrical contacts 3 located at different heights are contacted may be improved.

[0162] To accurately determine the position of the profile of the electrical contacts 3 on the DUT 1 relative to the device table 103, it may be desirable to provide at least three reference structures 147 on the device table 103. In some embodiments, more than three reference structures 147 may be provided. For example, in the embodiment of FIG. 10, eight reference structures 147 are provided.

[0163] Figure 11 shows an example of a reference structure 147 in more detail. Figure 11A is a schematic diagram of a side view of the reference structure 147. Figure 11B is a schematic diagram of the reference structure 147 shown in perspective. Figure 11C is a schematic diagram of the end of the reference structure 147 in more detail.

[0164] The reference structure 147 comprises a pillar-like structure. The pillar may have a diameter of, for example, approximately 2-3 mm. The reference structure 147 includes a substantially spherical tip portion 149. The spherical tip portion 149 is surrounded by a substantially flat rim 151. The spherical tip portion 149 and the substantially flat rim 151 provide an easily identifiable feature in the determined profile of the device table 103. For example, the spherical tip portion 149 and the substantially flat rim 151 may make it relatively easy to fit a geometric function to the profile data. Thus, the position of the reference structure 147 relative to other features in the determined profile (e.g., electrical contacts 3 on the DUT 1) can be easily identified.

[0165] The reference structure 147 may include other features that improve the visibility of the reference structure 147 to the profile determination system 127. For example, a profile determination system 127 that measures radiation scattered from an object at an oblique angle (e.g., the profile determination system 127 shown in FIG. 9 ) works particularly well when profiling an object that scatters a relatively large amount of radiation diffusely from the surface to be profiled. The reference structure 147 may be provided with roughness features on small scales that serve to increase the diffuse scattering of radiation from the reference structure 147. For example, the reference structure 147 may be provided with roughness features on a scale of about 50 microns or less. This may improve the visibility of the reference structure 147 to the profile determination system 127.

[0166] In some embodiments, the reference structure 147 may be provided with ridges on the surface of the reference structure 147. The ridges may be spaced, for example, by about 40 microns. The ridges may be considered an example of a roughness feature.

[0167] The reference structure 147 shown in FIG. 11 includes a reference feature 153. The reference feature 153 indicates a reference point to which the probe tip can be brought into contact with the reference structure 147. The reference feature may have dimensions approximately equal to the size of the probe tips 13, 15. Any reference made herein to a reference feature 153 having dimensions approximately equal to the size of the probe tips 13, 15 should be interpreted to mean that the reference feature 153 has dimensions on the order of (or comparable to) the size of the probe tips 13, 15. It should be understood that a reference feature 153 having dimensions approximately equal to the size of the probe tips 13, 15 should not be limited to features having the exact same size. As will be explained in more detail below, the reference feature 153 is intended as a point to which the probe tip can be guided to calibrate the position of the probe 7 relative to the device table 103. The extent to which the reference feature 153 and the probe tips 13, 15 have the same size can be determined by the required accuracy of the calibration.

[0168] 11 , the reference feature 153 comprises a groove in the reference structure. The groove is substantially circular and extends around the apex of the reference structure 147. The groove 153 may have a diameter of, for example, about 150 microns. The groove depth may be about 10 microns. In some embodiments, the reference feature 153 may include multiple circular grooves of different sizes extending around the apex of the reference structure 147. In other embodiments, the reference feature 153 may comprise a laser-etched mark on the reference structure 147, a crosshair (e.g., a pair of grooves forming a crosshair) indicated on the reference structure 147, or some other feature. In general, the reference feature 153 may include any feature resolvable by inspection (direct visual inspection or inspection by an inspection device (e.g., a camera or microscope)). This may allow a probe tip to be guided into contact with the reference point indicated by the reference feature 153.

[0169] As alluded to above, the reference features 153 may be used to calibrate the position of the probe 7 relative to the device table 103. As described above, the positions of the electrical contacts 3 on the DUT 1 held by the device table 103 are determined by the profile determination system 127 relative to the reference structures 147 on the device table 103. It is desirable to accurately calibrate the movement mechanism 122 that determines the position of the probe 7 relative to the device table 103 in order to determine the configuration of the movement mechanism 122 that brings the probe ends 13, 15 into contact with the electrical contacts of the DUT 1.

[0170] The movement mechanism 122 can be calibrated by bringing the probe 7 into contact with a reference structure 147. Because the position of the reference structure 147 on the device table 103 is known, bringing the probe 7 into contact with the reference structure 147 provides a known position of the probe 7 that can be used to calibrate the movement mechanism 122. To improve the accuracy of the calibration, the probe ends 13, 15 can be brought into contact with the reference structure 147 at or near a reference point indicated by a reference feature 153 on the reference structure 147. As described above, the reference feature 153 can have a size comparable to that of the probe ends 13, 15. Thus, the reference feature 153 provides a more accurate reference point to which the probe ends can be precisely moved. For example, as shown in FIG. 11C , the probe ends 13, 15 can be moved to contact the reference structure within a circular groove 153.

[0171] Reference feature 153 can, for example, surround the vertex of reference structure 147. For example, in embodiments in which reference feature 153 comprises a circular groove in the reference structure, the circular groove can extend around the vertex of reference structure 147 (as shown in FIG. 11C ). Reference feature 153 indicates a reference point that is substantially located at the vertex of reference structure 147 and that is within the circular groove. The probe tip can be brought into contact with the vertex (i.e., the reference point) of the reference structure.

[0172] The reference feature 153 may be provided on a convex or protruding surface of the reference structure 147. This may reduce the chance of the probe tip being unintentionally brought into contact with other areas of the reference structure 147.

[0173] In some embodiments, the movement mechanism 122 can be manually operated to bring the probe ends 13, 15 into contact with the reference structure. That is, the configuration of the movement mechanism 122 can be adjusted by a person until the probe ends 13, 15 contact the reference structure 147. The test system 101 can include a calibration system that enables the position of the probe ends 13, 15 relative to the reference structure 147 to be determined. The calibration system can include, for example, a camera or microscope through which the probe ends 13, 15 and the reference structure 147 can be viewed. The movement mechanism 122 can be adjusted by an operator while viewing the probe ends 13, 15 and the reference structure 147 through the calibration system. The movement mechanism 122 can be adjusted until the probe ends 13, 15 contact the reference structure 147 (e.g., at or near a reference point indicated by the reference feature 153).

[0174] This provides a reference for a known configuration of the movement mechanism 122, resulting in a known position of the probe 7 relative to the device table 103. This can allow for other configurations of the movement mechanism 122, resulting in other positions of the probe 7 relative to the device table 103. Knowing the position of the electrical contacts 3 relative to the device table 103 allows the probe 7 to be precisely moved to contact the desired electrical contacts 3. In some embodiments, reference features 153 on the reference structure 147 can be detected by the profile determination system 127. Thus, the positions of the reference features 153 used during calibration of the movement mechanism 122 can be detected in the profile of the electrical contacts 3 of the DUT 1. This can improve the accuracy with which the positions of the electrical contacts 3 are determined relative to the position of the probe 7.

[0175] In some embodiments, multiple probe ends 13, 15 of probe 7 may be brought into contact with reference structure 147 at different times to provide additional reference configurations for movement mechanism 122 and improve the accuracy of the calibration. Probe 7 may be moved to contact multiple different reference structures 147 at different times to further improve the calibration. To accurately calibrate the movement mechanism in all directions, it may be desirable for probe 7 to be brought into contact with reference structures 147 located at different positions in the x, y, and z directions.

[0176] The probe ends 13, 15 may be brought into contact with the reference structure 147 at a number of different orientations. For example, the probe 7 may be rotated to different orientations (e.g., four or more different orientations) while in contact with the reference structure 147 (e.g., by changing the angle θ that the probe makes with the z-axis and / or by changing the angle φ that the probe makes with the x-axis). The different orientations of the probe 7 may provide additional reference positions that may improve the calibration of the movement mechanism.

[0177] Examples have been described above in which a calibration system configured to enable determination of the position of the probe tip relative to the reference structure 147 includes a camera or microscope through which the probe tip and the reference structure 147 can be viewed. In some examples, the calibration system may include other components. For example, the calibration system may include a profile determination system 127, which may determine the profile of the reference structure 147 and the probe tip as the probe tip is brought towards the reference structure 147. This may enable an operator to determine the position of the probe tip relative to the reference structure 147 and to bring the probe tip into contact with the reference structure 147.

[0178] In some embodiments, the calibration system may include means for detecting contact between the probe tip and the reference structure. For example, the calibration system may include an electrical continuity tester that detects electrical continuity between the probe tip and the reference structure. The calibration system may include one or more pressure sensors on the probe and / or the reference structure that are configured to detect contact between the probe tip and the reference structure.

[0179] The calibration of the movement mechanism 122 may be updated without having to bring the probe ends 13, 15 into contact with the reference structure 147. For example, in some embodiments, the calibration of the movement mechanism 122 may be updated when the probe 7 is brought near the electrical contacts 3 of the DUT 1 (e.g., during testing of the DUT 1). The profile determination system 127 may determine the profile of the probe ends 13, 15 of the probe 7 and the profile of the electrical contacts 3 to which the probe ends 13, 15 are proximate. The determined profile may be used to determine the position of the probe ends 13, 15 relative to the electrical contacts 3. This may be used to determine the accuracy of the current calibration of the movement mechanism 122, and the calibration may be updated as necessary. The calibration of the movement mechanism 122 may be updated, for example, after the probe 7 is replaced with a new probe 7.

[0180] FIG. 12 is a schematic diagram of an embodiment of a mount 104 shown in two perspective views. Also shown in FIG. 12 is a device table 103 that may be disposed on the mount 104. The mount 104 is a kinematically constrained mount that restricts the movement of the device table 103 in multiple degrees of freedom. For example, the kinematically constrained mount 104 may restrict the movement of the device table 103 in all six degrees of freedom. Restricting the movement of the device table 103 may allow the device table 103 to be moved in a repeatable and controlled manner that allows for precise positioning of the device table 103. In some embodiments, the device table 103 may be held in a fixed position on the mount 104, and the probe 7 may be moved around the device table 103 to contact different elements on the device table 103.

[0181] The mount 104 includes ball supports 157 that fit into attachment points 145 located on the underside of the device table 103. The attachment points 145 include V-shaped grooves in which the ball supports 157 sit. The ball supports 157 can slide along the groove-shaped attachment points 145 to adjust the orientation of the device table 103 relative to the mount 104. Each ball support 157 has two contact points with the groove-shaped attachment points 145 in which the ball supports 157 sit. With three attachment points 145 and three ball supports 157, there are a total of six contact points. Each surface contact point can have a unique normal direction. The combination of the six contact points serves to restrict the movement of the device table 103 in six degrees of freedom.

[0182] The mount 104 further comprises a vacuum seal 159. The vacuum seal 159 may allow the device table 103 to be vacuum clamped to the mount 104. In other embodiments, the device table 103 may be clamped to the mount 104 using a different clamping mechanism. For example, the device table 103 may be magnetically, electrostatically, or mechanically clamped to the mount 104. The vacuum seal may allow a vacuum pump to be fluidly connected to a vacuum port 139 on the device table 103 through the mount 104.

[0183] The mount 104 further comprises a cleaning pad 161. The cleaning pad 161 provides a surface against which the probe ends 13, 15 of the probes 7 may be cleaned. For example, the movement mechanism 122 may drag the probe ends 13, 15 over the cleaning pad 161, which may act to remove dirt, solder oxides, or other deposits from the probe ends 13, 15.

[0184] Described above is an example of a test system 101 configured to determine a profile of electrical contacts 3 on one or more devices 1 before contacting the electrical contacts 3 with probes 7. Device profiling and probing may be performed in successive stages. For example, a device table 103 holding one or more devices 1 may first be profiled using a profile determination system 127. The device table 103 may then be moved to a probing stage, in which one or more probes 7 are brought into contact with electrical contacts 3 on the DUTs 1 positioned on the device table 103. The DUTs 1 may then be tested using the one or more probes 7. The profile of the device table 103 obtained during the profiling stage is used to determine a configuration of the movement mechanism 122 to be used during the probing stage to contact the electrical contacts 3 on the devices 1 on the device table 103.

[0185] To improve the throughput of the test system 101, the first device table 103 may be profiled while device 1 on the second device table 103 is probed. Once the first device table 103 has been profiled, it may be moved to a probing stage so that device 1 on the first device table 103 is probed. While device 1 on the first device table 103 is being probed, the third device table 103 may be profiled in preparation for probing device 1 on the third device table 103.

[0186] The test system 101 of Figure 6 includes a motion stage 106. The motion stage may be, for example, a linear motion stage 106 operable to move the device table 103 between a profiling stage and a probing stage.

[0187] After the device table 103 has been profiled by the profile determination system 127, the configuration of the movement mechanism 122 to be used during the probing phase is determined (e.g., by a controller). During the probing phase, the movement mechanism 122 may move one or both of the device table 103 and the probes 7 to a number of different positions and / or orientations so as to bring the probe ends 13, 15 of the probes 7 into contact with a number of different electrical contacts 3 on the DUT 1 located on the device table 103.

[0188] Prior to the probing step, a sequence of configurations of the moving mechanism that will attempt to contact each of the electrical contacts to be tested in the shortest possible time can be determined. For example, a comprehensive search of possible moving mechanism sequences can be performed to find the sequence that minimizes the time required to perform the probing step. Algorithms such as genetic algorithms or simulated annealing algorithms can be used to search for the optimal sequence of moving mechanism configurations.

[0189] Some forms of movement of the probe 7 and / or device table 103 may be performed faster than other forms of movement. For example, rotation of the probe 7 may take longer to perform than translation of the probe 7. Therefore, a solution may be sought that reduces the number of rotations of the probe 7 during the probing phase. For example, a solution may be explored that reduces the total number of different angular orientations of the probe 7 during the probing phase.

[0190] There may be several orientations of the probe 7 relative to the device table 103 that achieve contact with the electrical contacts in an undesirable manner. For example, some configurations of the probe 7 may result in slippage of the probe ends 13, 15 on the electrical contacts 3. Slippage of the probe 7 may cause one of the probe ends 13, 15 to move away from the electrical contacts 3. It may be desirable to seek a probe orientation in which the probe ends 13, 15 are located relatively close to the highest point on the electrical contacts 3, thereby reducing the likelihood of the probe ends 13, 15 slipping on the electrical contacts 3.

[0191] In some embodiments, the test system 101 may include multiple probes 7 (as shown in FIG. 6). Multiple probes may be used to simultaneously test different DUTs 1 located on a single device table 103. Additionally, or alternatively, multiple probes may be used to simultaneously test a single DUT 1 through different electrical contacts 3. This may reduce the amount of time required to test a single DUT 1 and / or the amount of time required to test all DUTs 1 located on the device table 103. Thus, the throughput of the test system 101 may be improved.

[0192] Described above are various improvements to the test system that allow for automated testing of multiple devices 1. Inventive improvements to the sampling module 18, radiation source, and delay line (e.g., as shown in FIG. 4) are also contemplated herein and will be described below with reference to FIGS. 13-15.

[0193] Figure 13 is a schematic diagram of a portion of a test system 201 according to one embodiment of the present invention. The test system 201 shown in Figure 13 may be similar to the test system described above with reference to Figure 4 and may include many of the same or similar components.

[0194] Test system 201 includes a sampling module 203. Sampling module 203 includes first and second photoconductive elements 204, a signal generator (not shown in FIG. 13), and a signal sampler (not shown in FIG. 13). Sampling module 203 is similar to sampling module 18 described above with reference to FIG. 4 and will not be described in further detail here.

[0195] The sampling module is connected to a probe 207 via a coaxial cable 205. The probe 207 is brought into contact with electrical contacts 3 on the DUT 1. The signal from the sampling module 203 is input to the DUT 1 through the probe 207, and the signal reflection from the DUT 1 returns to the sampling module for analysis.

[0196] The test system 201 further includes a radiation source 209, a beam splitter 211, and a delay line 213. The radiation source 209 may include, for example, a laser capable of emitting near-infrared radiation (e.g., having a wavelength of about 800 nm, about 1000 nm, or about 1560 nm). A radiation beam 210 emitted from the radiation source 209 is incident on the beam splitter 211. The radiation beam 210 may be a pulsed radiation beam. The pulses of the radiation beam may have a pulse width of, for example, less than about 1 picosecond. The beam splitter 211 splits the radiation beam 210 into a generated beam 215 and a received beam 217. The generated beam 215 and the received beam 217 are coupled to an optical fiber 207 and transmitted to the sampling module 203. In the sampling module 203, the generated beam is directed to be incident on the first photoconductive element 204, and the received beam is directed to be incident on the second photoconductive element 204.

[0197] Delay line 213 is disposed in the optical path of receive beam 217 and is configured to introduce an optical delay between pulses in generated beam 215 and pulses in receive beam 217. Delay line 213 may be similar to delay line 37 described above with reference to Figure 4 and may include one or more reflectors mounted on a translation stage (not shown in Figure 13), which may be moved to scan the optical delay between generated beam 215 and receive beam 217.

[0198] Prior art delay line configurations include separate slow-scan and fast-scan delay lines. The fast-scan delay line may be a galvanometer-driven delay line. In such configurations, the fast-scan delay line may not provide a sufficiently large delay time range. For example, the fast-scan delay line may introduce a maximum optical delay of approximately 50 picoseconds. In prior art configurations, data segments may be acquired over a 50 picosecond delay time range (corresponding to the maximum optical delay of the fast-scan delay line), and then the slow-scan delay line may be moved to acquire another data segment over another 50 picosecond range of delay time. The different data segments are then concatenated to obtain a complete data set. The process of acquiring multiple different data sets at different positions of the slow-scan delay line may result in a large acquisition time to obtain a complete data set.

[0199] In the embodiment shown in FIG. 13, only a single delay line 213 is used. The delay line 213 can be scanned over a wide range of delay times at speeds comparable to those achievable with galvanometer-driven delay lines. The delay line 213 is a direct-drive delay line including a synchronous linear motor configured to move a reflector to vary the optical delay introduced by the delay line 213. The linear motor may be brushless, reducing friction in the motor and improving efficiency. The translation stage may include high-quality crossed-roller bearings or air-bearings. In contrast, prior art delay line configurations use ball-screw drives, which limit the maximum speed and acceleration of the translation stage. The ball-screw also introduces some level of backlash, which is avoided by the direct-drive delay lines contemplated herein.

[0200] The overall acquisition time of measurements obtained using the direct drive lines discussed herein can be significantly improved relative to prior art configurations, for example, acquisition times can be as much as 60 times faster than those achievable with prior art configurations.

[0201] 13 further includes a digital sampling module 219. The digital sampling module 219 receives a first signal 221 from the delay line 213 and a second signal 223 from the sampling module 203. The digital sampling module 219 simultaneously samples the first and second signals 221, 223 and maintains alignment between the two signals so that data from the sampling module can be assigned to a specific delay time introduced by the delay line 213. The digital sampling module interfaces with a controller 225, which may be a computer. The controller 225 can store the data sampled by the digital sampling module 219.

[0202] 14 is a schematic diagram of a delay line configuration forming part of a test system according to one embodiment of the present invention. The configuration shown in FIG. 14 comprises a radiation source 301 emitting a radiation beam 303. The radiation beam 303 is incident on a beam splitter 305, which splits the radiation beam into a generated beam 307 and a received beam 309. Both the generated beam 307 and the received beam 309 are fed into the delay line configuration. The delay line configuration comprises a first reflector unit 311 that receives the generated beam 307 and a second reflector unit 313 that receives the received beam 309. The first and second reflector units 311, 313 may each comprise a single reflector or multiple reflectors. The first and second reflector units 311, 313 may comprise corner cube reflectors.

[0203] The first and second reflector units 311, 313 are mounted on a movable stage 315. The movable stage 315 is movable in a first direction 317 and a second direction 319. Movement of the movable stage 315 in the first direction 317 increases the optical path length of the generated beam 307 and decreases the optical path length of the received beam 309. Movement of the movable stage 315 in the second direction 319 decreases the optical path length of the generated beam 307 and increases the optical path length of the received beam 309.

[0204] In the configuration shown in FIG. 14 , movement of movable stage 315 changes the optical path lengths of the generated and received beams in opposite directions. As a result, movement of movable stage 315 by a first distance introduces a difference in the optical path lengths of the generated and received beams that is at least twice the first distance. Therefore, a smaller movement of the movable stage is required to change the optical delay between the generated and received beams by a given amount (relative to prior art configurations). This advantageously allows for faster scanning of the optical delay. Therefore, the acquisition time over which a given measurement is performed can be significantly reduced.

[0205] In the embodiment of Figure 14, the delay line arrangement further comprises a prism 321 (e.g. a roof prism) located in the optical path of the generated beam 307 and the received beam 309. The prism may reflect radiation to the first and second reflector units such that the radiation pulse undergoes multiple reflections at the reflector units 311, 313. By causing the radiation pulse to undergo multiple reflections at the reflector units 311, 313, the total optical path of the pulse through the delay line arrangement is increased. This may increase the optical delay introduced between the pulses in the generated and received beams.

[0206] The generated beam 307 and received beam 309 output from the delay line arrangement are coupled by coupler 323 into optical fiber 321. Optical fiber 321 can transmit the generated beam and received beam to a sampling module.

[0207] FIG. 15 is a schematic diagram of a radiation feedback system that may form part of a test system according to one embodiment of the present invention. The configuration shown in FIG. 15 comprises a radiation source 401 (e.g., a laser) that emits a radiation beam 403. The radiation beam 403 is coupled to an optical fiber 405. The optical fiber 405 may be used to transmit the radiation beam 403 to a sampling module (as described above with reference to other embodiments). The fiber coupling efficiency of the optical fiber 405 may change over time. For example, the coupling efficiency may change over time due to changes in the temperature of the fiber 405 or other factors such as creep of the optical components used to couple the radiation beam 403 to the fiber 405.

[0208] A change in the fiber coupling efficiency of the optical fiber 405 will cause a change in the power of the radiation beam that is output from the optical fiber 405 (and that may be provided to the sampling module). It may be desirable to maintain a substantially constant average power of the radiation that is output from the optical fiber 405 and that may be provided to the sampling module.

[0209] A radiation feedback system is provided to stabilize the power of radiation output from the optical fiber 405. The radiation feedback system comprises a radiation sensor 409, an attenuator 413, and a controller 411. The radiation beam 403 output from the optical fiber 405 is incident on a beam splitter 407. The beam splitter 407 directs a first portion 408 of the radiation beam to the radiation sensor 409. A second portion 410 of the radiation beam can be provided to, for example, a sampling module.

[0210] The radiation sensor 409 is configured to detect the intensity of the radiation output from the optical fiber 405 (the radiation may comprise radiation pulses). The attenuator 413 is positioned in the optical path of the radiation beam emitted from the radiation source 401 before the radiation beam is coupled to the fiber 405. The attenuator 413 is configured to reduce the intensity of the radiation beam by an adjustable amount. The controller 411 is configured to adjust the amount by which the attenuator reduces the intensity of the radiation beam in response to measurements of the intensity of the radiation beam by the radiation sensor 409. For example, if the radiation sensor 409 detects an increase in the intensity of the radiation beam 403, then the controller 411 can act to increase the amount by which the attenuator 413 attenuates the radiation beam 403. If the radiation sensor 409 detects a decrease in the intensity of the radiation beam 403, then the controller 411 can act to decrease the amount by which the attenuator 413 attenuates the radiation beam 403. Thus, the radiation feedback system can act to maintain a substantially constant average power of the radiation beam output from the optical fiber 405.

[0211] The radiation beam may be pulsed, and the radiation feedback system may act to maintain a substantially constant average power of the radiation beam, where the average is taken over one pulse period. The radiation feedback system may not act to alter the temporal profile of individual pulses. In some embodiments, the pulse repetition rate of the radiation beam may be about 100 MHz (i.e., 10 nanosecond pulse period). The radiation feedback system may act to reduce power instability at frequencies of about 1 KHz or less.

[0212] The controller 411 may comprise a proportional-integral-derivative (PID) controller. The attenuator 413 may include a liquid crystal variable retarder which, in combination with a polarizing element, may provide voltage-controlled attenuation of the radiation beam 403. In other embodiments, different types of attenuators may be used. For example, the attenuator 413 may comprise a motorized variable neutral-density filter wheel, an acousto-optic modulator, or an electro-optic modulator.

[0213] In some embodiments, one or more optical components of a test system may be fiber-based. For example, any of the radiation sources described herein may include a fiber laser. Additionally, or alternatively, the beam splitters or radiation sources described herein may be optical fiber-based. In some embodiments, one or more components of a delay line may be optical fiber-based. A fiber-based delay line may include a section of stretched optical fiber (e.g., using a piezoelectric bobbin). However, a fiber-based delay line may not achieve the range of delay times possible with a free-space delay line as described herein. Therefore, a test system including a delay line may not have all of its optical components based on optical fiber.

[0214] In embodiments including a dual laser system in which the optical delay between the generated and received beams can be adjusted by adjusting the synchronization between the two lasers, the entire path of the generated and / or received beams can be based within an optical fiber.

[0215] Various inventive aspects of the test system have been described above and illustrated in the drawings with reference to specific embodiments of the present invention. It will be appreciated that any of the described and / or illustrated aspects may be combined in a single embodiment. For example, one or more features of one embodiment may be combined with one or more features of another embodiment. It will be further appreciated that although several embodiments have been described that include one or more inventive aspects, embodiments that include only a single inventive aspect are also contemplated herein. In general, any feature of any described embodiment may be used alone or in any combination with any of the other features of the described embodiments.

[0216] While specific embodiments of the present invention have been described above, it will be understood that the invention may be practiced otherwise than as described. The above description is illustrative and not limiting. Thus, it will be apparent to those skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below. [Example 1] A test system for testing a device having a plurality of electrical contacts, the test system comprising: a device table operable to hold at least one device under test; a probe including at least one probe tip for contacting an electrical contact of the device under test; a movement mechanism operable to move one or both of the device table and the probes to bring the at least one probe tip into contact with at least one electrical contact of a device under test; a profile determination system configured to determine a profile of the electrical contacts of a device under test. [Example 2] The profile determination system a radiation source configured to irradiate at least a portion of the device under test with radiation; a radiation sensor configured to detect radiation scattered from the electrical contacts of the device under test; and a controller configured to determine a profile of the electrical contacts of the device under test from the detected scattered radiation. [Example 3] The test system of Example 2, wherein the radiation sensor is positioned so that different portions of the device under test that extend away from the device table by different amounts appear at different positions within the field of view of the radiation sensor. Example 4. The testing system of Example 3, wherein the radiation sensor is oriented at an oblique angle relative to a direction of propagation of radiation emitted from the radiation source. Example 5. The test system of any of Examples 2 to 4, wherein the radiation source is configured to illuminate the strip of the device under test with a radiation strip. [Example 6] A test system as described in Example 5, wherein the radiation sensor is configured to detect radiation scattered from electrical contacts located within the radiation strip, and the controller is configured to determine the height of a point of the device under test located within the irradiated strip of the device under test. [Example 7] A test system as described in Example 6, wherein the movement mechanism is operable to move one or both of the device table and the radiation source to scan the radiation strip on the device under test, and the controller is configured to combine the determined heights of points on the device under test at different positions on the radiation strip to determine the profile of the electrical contacts of the device under test. [Example 8] A test system described in any of Examples 1 to 7, wherein the device table includes a plurality of reference structures extending outside or within the device table, and the profile determination system is configured to determine the position of the profile of the electrical contacts of the device under test relative to the position of the reference structures. Example 9. The test system of Example 8, wherein the reference structures extend outside the device table and at least two of the reference structures extend outside the device table by different distances. [Example 10] A test system as described in Example 8 or Example 9, wherein the movement mechanism is operable to move one or both of the device table and the probes so that at least one of the probe ends contacts one of the reference structures. Example 11. The test system of Example 10, further comprising a calibration system configured to enable determination of a position of the at least one probe end relative to the reference structure. Example 12. The test system of any of Examples 1 to 11, wherein the profile determination system is further configured to determine a position of a probe tip relative to an electrical contact of a device under test. [Example 13] A test system described in any of Examples 1 to 12, further comprising a controller configured to determine, from the determined profile of the electrical contacts of the device under test, a configuration of the movement mechanism that brings the at least one probe end into contact with at least one electrical contact of the device under test. [Example 14] A test system for testing a device having a plurality of electrical contacts, the test system comprising: a device table operable to hold at least one device under test; a probe including at least one probe tip for contacting an electrical contact of the device under test; a movement mechanism operable to move one or both of the device table and the probes to bring the at least one probe end into contact with at least one electrical contact of a device under test; A test system wherein the device table includes a plurality of reference structures extending outwardly or into the device table. Example 15. The test system of Example 14, wherein at least two of the reference structures extend different distances out of or into the device table. [Example 16] A test system as described in Example 14 or Example 15, wherein the movement mechanism is operable to move one or both of the device table and the probes so that at least one of the probe ends contacts one of the reference structures. Example 17. The test system of Example 16, further comprising a calibration system configured to enable determination of a position of the at least one probe end relative to the reference structure. [Example 18] A test system as described in Example 16 or Example 17, wherein at least one of the reference structures includes a reference feature indicating a reference point on the reference structure, and the movement mechanism is operable to move one or both of the device table and the probes so that at least one of the probe ends contacts the reference point. Example 19. The test system of Example 18, wherein the reference feature comprises a substantially circular groove formed in the reference structure and extending around an apex of the reference structure. [Example 20] The test system of Example 19, wherein the reference structure includes a plurality of substantially circular grooves formed therein, each groove extending around an apex of the reference structure. [Example 21] The test system of any one of Examples 14 to 20, wherein at least one of the reference structures comprises a substantially spherical tip portion. Example 22: The test system of Example 21, wherein the spherical tip portion is surrounded by a substantially flat rim. [Example 23] A test system according to any one of Examples 14 to 22, wherein at least one of the reference structures comprises a surface having roughness features on the scale of 50 microns or less. [Example 24] The test system according to any one of Examples 1 to 23, wherein the device table is operable to hold a plurality of devices under test. [Example 25] A test system described in any of Examples 1 to 24, further comprising a kinematically constrained mount to which the device table is attached, the kinematically constrained mount configured to constrain movement of the device table in multiple degrees of freedom. [Example 26] The test system of any one of Examples 1 to 25, further comprising a loading device operable to automatically load and unload devices under test from the device table. [Example 27] a signal generator configured to generate a signal and direct the signal through at least one of the probe ends, such that, in use, the signal is directed to a device under test through an electrical contact of the device under test; 27. The test system of any one of Examples 1 to 26, further comprising: a signal sampler configured to sample a signal passing through at least one of the probe ends, wherein during use, a signal reflected at the device under test and passing through the probe end is sampled by the signal sampler. [Example 28] The test system of Example 27, wherein the signal generator is configured to generate a wideband signal having frequency components in a range of 0.01 GHz to 10 THz. [Example 29] The signal generator a pulsed radiation source; a first signal conversion device disposed to receive radiation pulses from the pulsed radiation source and configured to output signal pulses in response to irradiation from the pulsed radiation source; and a transmission line arrangement configured to direct the signal pulses from the first signal transformation device through at least one of the probe ends. [Example 30] The signal sampler a second signal converting device arranged to receive radiation pulses from the pulsed radiation source, the second signal converting device responsive to irradiation from the pulsed radiation source to sample the signal pulses received at the second signal converting device; 30. The test system of Example 29, wherein the transmission line configuration is configured to direct signal pulses reflected from or transmitted through a device under test and passed through at least one of the probe ends to the second signal conversion device. [Example 31] A test system for testing a device, the test system comprising: a pulsed radiation source configured to provide a generated radiation beam and a received radiation beam, wherein the generated radiation beam and the received radiation beam are pulsed radiation beams; a first signal conversion device arranged to receive the pulses of the generated radiation beam and configured to output a signal pulse in response to receiving the pulses of the generated radiation beam; a second signal conversion device positioned to receive pulses of the received radiation beam and configured to sample signal pulses in response to receiving the pulses of the received radiation beam; a transmission line configuration configured to guide a signal pulse from the first signal converting device to a device under test and to guide a signal pulse reflected from the device under test through the device under test to the second signal converting device; a direct drive delay line arranged in an optical path of the generated radiation beam and / or the received radiation beam, the delay line configured to introduce an optical delay between the generated radiation beam and the received radiation beam, such that pulses of the generated radiation beam are incident on the first signal conversion device at a different time than corresponding pulses of the received radiation beam which are incident on the second signal conversion device; the delay line at least one reflector positioned in the optical path of the generated radiation beam and / or the received radiation beam; a synchronous linear motor configured to move the reflector and change the optical path length of the generated radiation beam and / or the received radiation beam to change the optical delay between the generated radiation beam and the received radiation beam. [Example 32] A test system for testing a device, the test system comprising: a pulsed radiation source configured to provide a generated radiation beam and a received radiation beam, wherein the generated radiation beam and the received radiation beam are pulsed radiation beams; a first signal conversion device arranged to receive the pulses of the generated radiation beam and configured to output a signal pulse in response to receiving the pulses of the generated radiation beam; a second signal conversion device positioned to receive pulses of the received radiation beam and configured to sample signal pulses in response to receiving the pulses of the received radiation beam; a transmission line configuration configured to guide a signal pulse from the first signal converting device to a device under test and to guide a signal pulse reflected from the device under test through the device under test to the second signal converting device; a first reflector positioned in the path of the generated radiation beam; a second reflector positioned in the path of the received radiation beam; and a delay line including a movable stage to which the first reflector and the second reflector are mounted, wherein movement of the movable stage in a first direction increases the optical path length of the generated radiation beam and decreases the optical path length of the received radiation beam, and movement of the movable stage in a second direction decreases the optical path length of the generated radiation beam and increases the optical path length of the received radiation beam. [Example 33] A test system for testing a device, the test system comprising: a pulsed radiation source configured to provide a generated radiation beam and a received radiation beam, wherein the generated radiation beam and the received radiation beam are pulsed radiation beams; a first signal conversion device arranged to receive the pulses of the generated radiation beam and configured to output a signal pulse in response to receiving the pulses of the generated radiation beam; a second signal conversion device positioned to receive pulses of the received radiation beam and configured to sample signal pulses in response to receiving the pulses of the received radiation beam; a transmission line configuration configured to guide a signal pulse from the first signal converting device to a device under test and to guide a signal pulse reflected from the device under test through the device under test to the second signal converting device; a radiation sensor configured to detect an intensity of a radiation pulse emitted from the pulsed radiation source; an attenuator disposed in the optical path of the radiation pulse emitted from the pulsed radiation source and configured to reduce the intensity of the radiation pulse by an adjustable amount; and a radiation feedback system including a controller configured to adjust the amount by which the attenuator reduces the intensity of the radiation pulse in response to a measurement of the intensity of the radiation pulse by the radiation sensor.

Claims

1. 1. A test system for testing a device under test having a plurality of electrical contacts, the test system comprising: a device table operable to hold the devices under test; a probe including at least one probe tip for contacting an electrical contact of the device under test; a movement mechanism operable to move one or both of the device table and the probes to bring the at least one probe tip into contact with at least one electrical contact of the device under test; a profile determination system configured to determine a three-dimensional profile of a plurality of electrical contacts of the device under test; a configuration of the movement mechanism for bringing the at least one probe end into contact with at least one electrical contact of the device under test, including the electrical contact under test, for each electrical contact under test among the plurality of electrical contacts of the device under test, is determined from the determined three-dimensional profile of the plurality of electrical contacts of the device under test, the movement mechanism is capable of tilting the probe with respect to the device under test, and the angle at which the probe is tilted with respect to the device under test is allowed to be different when contacting different electrical contacts; the probe having a first probe end and a second probe end; the movement mechanism is operable to move one or both of the device table and the probes so as to bring the first probe end into contact with an electrical contact of the test object and the second probe end into contact with another electrical contact of the device under test; the second probe end is configured to conduct a ground current; Test system.

2. The profile determination system comprises: a radiation source configured to irradiate at least a portion of the device under test with radiation; a radiation sensor configured to detect radiation scattered from the electrical contacts of the device under test; 10. The test system of claim 1, further comprising: a controller configured to determine the three-dimensional profile of the plurality of electrical contacts of a device under test from the detected scattered radiation.

3. 3. The test system of claim 2, wherein the radiation sensor is positioned such that different portions of the device under test that extend away from the device table by different amounts appear at different positions within the field of view of the radiation sensor.

4. The test system of claim 3 , wherein the radiation sensor is oriented at an oblique angle relative to a direction of propagation of radiation emitted from the radiation source.

5. 5. The test system of claim 2, wherein the radiation source is configured to illuminate the strip of devices under test with a radiation strip.

6. 6. The test system of claim 5, wherein the radiation sensor is configured to detect radiation scattered from electrical contacts located within the radiation strip, and the controller is configured to determine a height of a point of the device under test located within the illuminated strip of the device under test.

7. 7. The test system of claim 6, wherein the movement mechanism is operable to move one or both of the device table and the radiation source to scan the radiation strip on the device under test, and the controller is configured to combine determined heights of points of the device under test at different positions of the radiation strip to determine the three-dimensional profile of the plurality of electrical contacts of the device under test.

8. 8. A test system as described in any one of claims 1 to 7, wherein the device table includes a plurality of reference structures extending outside or into the device table, and the profile determination system is configured to determine the position of the three-dimensional profile of the plurality of electrical contacts of the device under test relative to the position of the reference structures.

9. 9. The test system of claim 8, wherein the reference structures extend outside the device table and at least two of the reference structures extend outside the device table by different distances.

10. 10. The test system of claim 8 or claim 9, wherein the movement mechanism is operable to move one or both of the device table and the probes so that at least one of the probe ends contacts one of the reference structures.

11. The test system of claim 10 , further comprising a calibration system configured to enable determination of a position of the at least one probe tip relative to the reference structure.

12. 12. The test system of claim 1, wherein the profile determination system is further configured to determine the position of the probe tips relative to the electrical contacts of a device under test.

13. 13. The test system of claim 1, wherein the determined three-dimensional profile includes a plurality of locations at which surfaces of the plurality of electrical contacts are placed so that the positions and sizes or positions and shapes of the plurality of electrical contacts are determined.

14. the test system further comprising a signal generator for generating a signal and directing the signal through the at least one probe end; the signal generator is configured to generate a signal having frequency components in the range of 0.01 GHz to 10 THz; A test system according to any one of claims 1 to 13.

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