Methods and techniques for testing light emitting devices

Abstract

Methods and techniques for testing light emitting devices are provided. A probe card is used to measure the electrical and optical properties of the light emitting devices. According to aspects of the disclosure, a probe card is used to perform electroluminescence and photoluminescence testing of light emitting devices during manufacturing. According to an embodiment of the disclosure, the probe card comprises of millions of probe tips that simultaneously are placed in proximity to or in contact with the light emitting devices.

Description

Attorney Docket No.2000P009-WO METHODS AND TECHNIQUES FOR TESTING LIGHT EMITTING DEVICES Cross-Reference to Related Applications

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 515,773, filed on July 26, 2023, and titled “Methods and Techniques for Testing Light Emitting Devices,” which application is herein incorporated by reference in its entirety. Field of the Invention

[0001] The present disclosure is generally directed to methods and techniques for testing light emitting devices. A probe card is used to source and measure the electrical and optical responses of the light emitting devices. Background

[0002] As computing is increasingly embedded into daily life across smartphones, gaming, augmented reality, and virtual reality, there is constant demand for smaller, sharper, and more energy-efficient screens. Since display components are typically the largest energy consumers in mobile devices, there is enormous pressure to reduce screen energy consumption to extend battery life. To address this, there has been significant investment and research geared towards the development of micro-light emitting diodes (microLEDs). MicroLEDs are considered next generation display technology as they offer higher display resolution, better color, higher brightness, faster display switching speeds, and, critically, substantially improved energy efficiency. MicroLED is a self-emissive display technology that consumes less than half the power consumed by conventional displays.

[0003] However, yield issues caused by the introduction of new materials into the microLED manufacturing process, chip transfer, and array-to-driver bonding plague the commercialization of microLEDs. Because the human eye is very sensitive, it can detect a single faulty microLED pixel in a display, so extensive optical and electrical testing of microLEDs during manufacturing and packaging is required. Unfortunately, the quality and features of existing probe cards and microscale testing technologies lag behind the microLED scale down, placing the microLED industry at a quandary as systematic and random faults during manufacturing could persist across multiple batches, with negative impact on yields and time-to-market.Attorney Docket No.2000P009-WO Summary of the Invention

[0004] The present disclosure is directed generally towards methods and techniques for testing light emitting devices. A probe card is used to measure the electrical and optical properties of the light emitting devices.

[0005] According to aspects of the disclosure, a probe card is used to perform electroluminescence and photoluminescence testing of light emitting devices during manufacturing. According to an embodiment of the disclosure, the probe card comprises of millions of probe tips that simultaneously are placed in proximity to or in contact with the light emitting devices.

[0006] This disclosure will provide early actionable insights into which light emitting devices are viable for transfer, determine potential process variations which could significantly reduce device design cost by 25%, shorten manufacturing iterations by 2X, and accelerate time- to-market by 4 months. The testing paradigm enabled by the disclosures will have far-reaching commercial and societal impact, magnified by the powerful trends driving mobility, connectivity, and enterprise. The disclosures would accelerate the development of light emitting devices and advanced integrated circuits at the 3 nm, 1 nm, and beyond where conventional testing methodologies are challenged. Advances here will impact a range of societal needs, including continued scale-down of electronics, internet-of-things, mobile computing, virtual and augmented reality.

[0007] The aspects of this disclosure could be used to test other light emitting devices such as organic light emitting diodes (OLED), light emitting diodes (LED), microLED, vertical- cavity surface-emitting laser (VCSEL), edge emitting lasers (EEL), nano-light emitting diodes (nanoLED), and many more emissive devices.

[0008] Generally, in one aspect, a method for testing light emitting devices is provided. The method includes providing a probe card with at least two probes. The method further includes applying a potential difference across a first probe and a second probe of the at least two probes. The method further includes aligning the first probe and the second probe to a first terminal and a second terminal, respectively, of the light emitting device. Thereafter, the method further includes instructing a movable stage to bring the first probe and the second probe into proximity with the first terminal and the second terminal of the light emitting device. A rate of movement or a velocity of the movable stage causes a motional current to be generated within the light emitting device. The generated motional current causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation. Switching off the light emitting device is achieved by ceasing to move the movable stage and / or increasing a separation gap betweenAttorney Docket No.2000P009-WO one of the at least two probes and one of the first terminal or the second terminal of the light emitting device.

[0009] According to an example, the first terminal and the second terminal of the light emitting device are located on the same side of a substrate of the light emitting device.

[0010] According to an example, the at least first terminal and the at least second terminal of the light emitting device are located on opposite sides of a substrate of the light emitting device.

[0011] According to an example, the first terminal is an anode and the second terminal is a cathode or the first terminal is a cathode and the second terminal is an anode.

[0012] According to an example, the light emitting device wafer is scanned across a biased probe of the at least two probes while an imaging sensor generates an image of the light emitting devices.

[0013] According to an example, an intensity or a power of the emitted light or electromagnetic radiation is directly proportional to the generated motional current that flows within the light emitting device.

[0014] According to an example, an amount of the motional current is directly proportional to the velocity of the movement of the movable stage.

[0015] According to an example, an amount of the motional current is directly proportional to the potential difference applied across the first terminal and the second terminal of the light emitting device.

[0016] According to an example, an amount of motional current is inversely proportional to the separation gap between one of the at least two probes and one of the first terminal or the second terminal of the light emitting device.

[0017] According to an example, an amount of motional current is directly proportional to an area of one of the first terminal or the second terminal of the light emitting device.

[0018] According to an example, an amount of motional current is directly proportional to a permittivity value of a substance or a gas that is located between a probe tip of one of the at least two probes and one of the first terminal or the second terminal of the light emitting device.

[0019] According to an example, the emitted light or electromagnetic radiation is measured with a vision system.

[0020] According to an example, the vision system is capable of measuring emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, or emission angle.Attorney Docket No.2000P009-WO

[0021] According to an example, the probe card includes a substrate and the at least two probes made from a conductive material. One of the at least two probes has a probe tip including memristive material or a polymer.

[0022] According to an example, the memristive material is configured to switch its state from conducting to insulating and vice versa.

[0023] According to an example, the memristive material is a deformable material configured to reversibly deform when pushed against a device under test.

[0024] According to an example, the memristive material comprises metal oxides, chalcogenides, amorphous silicon, carbon, and polymer-nanoparticles.

[0025] According to an example, the memristive material is a phase change material.

[0026] According to an example, the phase change material comprises chalcogenide glass or Germanium Antimony Telluride.

[0027] According to an example, the polymer is a deformable material configured to reversibly deform when pushed against a device under test.

[0028] According to an example, the polymer comprises polydimethylsiloxane (PDMS) or an epoxy-based photoresist.

[0029] According to an example, an active or passive switch matrix is monolithically integrated with the probe card.

[0030] According to an example, at least a photon sensor is monolithically integrated into the probe card.

[0031] According to an example, the photon sensor is configured to measure and display emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, or emission angle.

[0032] Generally, in another aspect, a method for testing light emitting devices is provided. The method includes providing a probe card with at least one probe. The method further includes aligning a first probe of the at least one probe to a first terminal of the light emitting device. The method further includes applying a potential difference across the first probe and a second terminal of the light emitting device. Furthermore, the method includes instructing a movable stage to bring the first probe into proximity or contact with the first terminal of the light emitting device. A velocity of movement of the movable stage causes a motional current to be generated within the light emitting device. The generated motional current causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation. Switching off the light emitting device is achieved by ceasing to move the movable stage and / orAttorney Docket No.2000P009-WO increasing a separation gap between the first probe and one of the first terminal and the second terminal of the light emitting device.

[0033] According to an example, the movement of the movable stage ceases when a motion sensor detects that a probe tip of the at least one probe is in proximity or contact with the first terminal of the light emitting device.

[0034] According to an example, the motion sensor is monolithically integrated into the probe card or a substrate of the light emitting device wafer.

[0035] According to an example, the motion sensor is a force sensor, capacitive sensor, proximity sensor, or a light sensor.

[0036] Generally, in another aspect, a method for testing light emitting devices is provided. The method includes providing a probe card with at least two probes. The method further includes aligning a first probe of the at least one probe to a first terminal of a light emitting device as well as aligning a second probe of the at least two probes to a second terminal of the light emitting device. The method further includes applying a potential difference across the first probe and the second probe. Further, the method includes instructing a movable stage to bring the first probe and the second probe into contact with the first terminal and the second terminal of the light emitting device, respectively. A velocity of the movable stage causes a motional current to be generated within the light emitting device. The generated motional current is configured to cause the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation. Upon the first probe and the second probe establishing contact with the at least first terminal and the at least second terminal, respectively, a DC current flows within the light emitting device. The DC current causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation. Switching off the light emitting device is achieved by ceasing to move the movable stage and increasing a separation gap between one of the at least two probes and one of the first terminal or the second terminal of the light emitting device.

[0037] Generally, in another aspect, a method for testing light emitting devices is provided. The method includes providing a probe card with at least one probe. The method further includes aligning a first probe to a first terminal of the light emitting device. The method further includes creating a fixed separation gap between the first probe and the first terminal of the light emitting device. The method further includes applying an AC or high frequency signal to the first probe. The frequency of the AC or high frequency signal is at a resonance frequency of the light emitting device. The method further includes electrically grounding a second terminal of the light emitting device. Generating a resonance current within the light emittingAttorney Docket No.2000P009-WO device which causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation.

[0038] Generally, in another aspect, a method for testing light emitting devices is provided. The method includes providing a probe card with at least two probes. The method further includes aligning the first probe of the at least two probes to the first terminal of the light emitting device as well as aligning a second probe of the at least two probes to a second terminal of the light emitting device. The method further includes creating a fixed separation gap between the first probe and the first terminal of the light emitting device. The method further includes applying an AC or high frequency signal to the first probe while electrically grounding the second probe. The frequency of the AC or high frequency signal is at a resonance frequency of the light emitting device. The method further includes generating a resonance current within the light emitting device which causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation.

[0039] According to an example, an intensity or brightness of the emitted light or electromagnetic radiation is directly proportional to the amplitude or magnitude of the applied AC or high frequency signal.

[0040] According to an example, the high frequency signal is a radiofrequency signal, a microwave signal, infrared signal, or a terahertz signal.

[0041] According to an example, a vision system is used to measure emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, or emission angle.

[0042] According to an example, an image sensor is attached to the probe card or a substrate of the light emitting device.

[0043] According to an example, the image sensor is configured to measure emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, or emission angle.

[0044] According to an example, the image sensor comprises materials or devices that are photon sensitive to an emission wavelength of the light or electromagnetic radiations emitted from the light emitting device.

[0045] According to an example, the materials or devices are diodes or field effect transistors.

[0046] According to an example, the image sensor is an excitation source configured to excite the light emitting device to cause it to light up and / or emit electromagnetic radiation.

[0047] According to an example, the excitation source is a laser.Attorney Docket No.2000P009-WO

[0048] Generally, in another aspect, a method for testing light emitting devices is provided. The method includes providing a probe card with at least one probe. The method further includes creating a separation gap between a first probe of the at least one probe tip and a first terminal of a light emitting device. The method further includes misaligning the first probe to the first terminal of a light emitting device and applying a potential difference across the first probe and a second terminal of the light emitting device. Furthermore, the method includes instructing a movable stage to laterally align the first probe to the first terminal of the light emitting device. The velocity of the movable stage causes a motional current to be generated within the light emitting device. The generated motional current causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation. Switching off the light emitting device is achieved by ceasing to laterally move the movable stage and / or misaligning the first probe to the first terminal of the light emitting device.

[0049] Generally, in another example, a method for testing light emitting devices is provided. The method includes providing a probe card with at least two probes. The method includes creating a separation gap between at least a first probe of the two probes and a first terminal of a light emitting device. Furthermore, the method includes creating a separation gap between a second probe of the at least two probes and a second terminal of the light emitting device. The method further includes misaligning the first probe to the first terminal of the light emitting device. The method further includes misaligning the second probe to the second terminal of the light emitting device. The method further includes applying a potential difference across the first probe and the second probe. Furthermore, the method includes instructing a movable stage to laterally align the first probe and the second probe to the first terminal and the second terminal of the light emitting device respectively. The velocity of the movable stage causes a motional current to be generated within the light emitting device. The generated motional current causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation. Switching off the light emitting device is achieved by ceasing to laterally move the movable stage and / or misaligning the first probe and the second probe to the first terminal and the second terminal of the light emitting device.

[0050] In various implementations, a processor or controller may be associated with one or more storage media (generically referred to herein as “memory,” e.g., volatile and non-volatile computer memory such as RAM, PROM, EPROM, EEPROM, floppy disks, compact disks, optical disks, magnetic tape, SSD, etc.). In some implementations, the storage media may be encoded with one or more programs that, when executed on one or more processors and / or controllers, perform at least some of the functions discussed herein. Various storage media mayAttorney Docket No.2000P009-WO be fixed within a processor or controller or may be transportable, such that the one or more programs stored thereon can be loaded into a processor or controller so as to implement various aspects as discussed herein. The terms “program” or “computer program” are used herein in a generic sense to refer to any type of computer code (e.g., software or microcode) that can be employed to program one or more processors or controllers.

[0051] It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It should also be appreciated that terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.

[0052] These and other aspects of the various embodiments will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. Brief Description of the Drawings

[0053] The present invention will be more fully understood and appreciated by reading the following Detailed Description in conjunction with the accompanying drawings, in which:

[0054] FIG.1A is a side view of a probe card, according to aspects of the present disclosure.

[0055] FIG. 1B is a side view of a light emitting device wafer, according to aspects of the present disclosure.

[0056] FIG.1C is a side view of a probe card and light emitting device wafer in proximity, according to aspects of the present disclosure.

[0057] FIG. 1D is an electrical equivalent circuit, according to aspects of the present disclosure.

[0058] FIG. 1E are plots of stage movement, separation gap, and motional current versus time, according to aspects of the present disclosure.

[0059] FIG. 1F is a side view of a probe card in mechanical contact with a light emitting device wafer, according to aspects of the present disclosure.

[0060] FIG. 1G is an electrical equivalent circuit, according to aspects of the present disclosure.

[0061] FIG. IH are plots of stage movement, separation gap, and motional current versus time, according to aspects of the present disclosure.Attorney Docket No.2000P009-WO

[0062] FIG.1I is a top view of the light emitting device wafer, according to aspects of the present disclosure.

[0063] FIG.1J is a top view of a probe card, according to aspects of the present disclosure.

[0064] FIG. 1K is a bottom view of a probe card, according to aspects of the present disclosure.

[0065] FIG.1L is a top view of a probe card, according to aspects of the present disclosure.

[0066] FIG.2A is a top view of a carrier, according to aspects of the present disclosure.

[0067] FIG.2B is a bottom view of a carrier, according to aspects of the present disclosure.

[0068] FIG.3A is a side view of a probe card in proximity to a light emitting device wafer, according to aspects of the present disclosure.

[0069] FIG.3B is a side view of a probe card in proximity to a light emitting device wafer, according to aspects of the present disclosure.

[0070] FIG.4 is a side view of an imager, according to aspects of the present disclosure.

[0071] FIG.5A is a side view of an imager that is placed on top of a probe card, according to aspects of the present disclosure.

[0072] FIG. 5B is a side view of an imager that is placed below the light emitting device wafer, according to aspects of the present disclosure.

[0073] FIG. 6 is a side view of a probe card that is monolithically integrated with photon sensitive devices along with a light emitting device wafer, according to aspects of the present disclosure.

[0074] FIG.7A is a side view of a probe card in proximity to a light emitting device wafer, according to aspects of the present disclosure.

[0075] FIG. 7B is an electrical equivalent circuit, according to aspects of the present disclosure.

[0076] FIG. 7C is an electrical equivalent circuit, according to aspects of the present disclosure.

[0077] FIG.8 is a side view of an imager that is placed on top of a probe card, according to aspects of the present disclosure.

[0078] FIG. 9 is a side view of a probe card that is monolithically integrated with photon sensitive devices along with a light emitting device wafer, according to aspects of the present disclosure.

[0079] FIG.10 is a side view of a probe card in proximity to a light emitting device wafer, according to aspects of the present disclosure.Attorney Docket No.2000P009-WO

[0080] FIG.11A is a side view of a probe card in proximity to a light emitting device wafer, according to aspects of the present disclosure.

[0081] FIG.11B is a side view of a probe card in proximity to a light emitting device wafer, according to aspects of the present disclosure.

[0082] FIG.12 is a schematic view of a probe card that is mounted on top of a LED wafer. Detailed Description of Embodiments

[0083] The present disclosure describes various methods and techniques for testing light emitting devices (LEDs) as well as measuring their emission intensity or emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle.

[0084] The ability to parallel test millions of light emitting devices would enable light emitting device manufacturers to gain early actional insights into their performance, increase measurement throughput, reduce cost of test, and accelerate the commercialization of new display technologies.

[0085] FIG.1A illustrates a side view of a probe card 100A. The probe card substrate 102 could be a material that is optically transparent to the emission wavelength of the light emitting device (LED). Thus, the electromagnetic radiation emitted from the light emitting device should be capable of transmitting through substrate 102. An imaging sensor could be placed on top of the probe card 100A to sense the transmitted electromagnetic radiation and convert that into an image. Substrate 102 could be opaque or transparent material. It is preferable for the substrate 102 to be transparent if the probe card 100A would be used to test light emitting devices. Example of transparent substrates are glass, Pyrex, fused silica, etc. For LEDs that emit in the infrared wavelengths, the substrate 102 could be silicon. First probes 104 and second probes 106 are attached to the probe card substrate 102. Material forming a probe tip 108 is attached to the apex of the probes 104 and 106. In this way, the material may be considered as forming probe tips on the first probes 104 and the second probes 106. The material could be a polymer and / or dielectric, and / or a memristive material. The polymer minimizes probe tip damage or scratches to the LED during probing. The polymer could be conductive or insulative. The polymer could also be reversibly deformable. Examples of polymer are polydimethylsiloxane (PDMS), epoxy-based photoresist such as SU-8, general photoresist, porous polymer, etc. The probes 104 and 106 are electrically isolated from each other. The probe tip size and spacings range from nanometers to millimeters.Attorney Docket No.2000P009-WO

[0086] With continued reference to FIG.1A, the material could be a memristor. A memristor is a non-volatile electronic memory device whose resistance can be programmed (resistor function) and subsequently remained stored (memory function). Thus, the memristor could be programmed to be conductive or insulative (non-conducting). The memristive material could be a polymer with reversibly deformable properties that reversibly deforms when pushed against a device under test. Materials such as metal oxides, chalcogenides, amorphous silicon, carbon, and polymer-nanoparticle composite materials are examples of the memristive material. Most common memristive materials are hafnium oxide, titanium oxide, vanadium oxide, aluminum oxide, silicon dioxide, silicon nitride or a combination thereof. Phase change materials such as chalcogenide glass, Germanium Antimony Telluride (Ge2Sb2Te5) also exhibit memristive behaviors and could be used to form the probe tip. In a phase change material, an electric current flowing through the phase change material could heat and quench the phase change material making it either amorphous (insulative) or crystalline (conductive). In certain testing schemes, it is desirable for the probe tip to be either conductive or insulative. To change the conductivity state of the memristive material at the probe tip 108, the memristive material of probe card 100A could be brought into mechanical contact with a conductive polymer plate. To make the memristive material conductive, a positive potential (set voltage) is applied to the probes 104 and 106 while the conductive polymer plate is electrically grounded. To switch the state of the memristive material to insulative, a negative potential (reset voltage) is applied to the probes 104 and 106 while the conductive polymer plate is electrically grounded. After the memristive material is programmed to a conductive or insulative state, the probe card 100A along with the probes 104, 106, and memristive material could be used to test the LED.

[0087] FIG.1B is a side view of a light emitting device (LED) wafer 100B. The wafer 100B could be a sheet for roll-to-roll testing of the LEDs. Referring to FIG. 1B, the LEDs are fabricated on the substrate 110. The substrate 110 could be silicon or sapphire. The LED could be a diode with an anode terminal 112 and cathode terminal 114. If the LED is a diode, it could be forward biased to switch it on. The substrate 110 could contain a single or several LEDs. The anode terminal 112 and cathode terminal 114 could be located on the frontside 116 of the substrate 110. When the LED is switched on, light could emit through the frontside 116 and / or the bottom side 118 of the substrate 110.

[0088] FIG. 1C is a schematic view of the probe card 100A brought into proximity to the LED wafer 100B. A first separation gap 120 exists between the first probe 104 and the LED first terminal 112. A second separation gap 122 exists between the second probe 106 and the LED second terminal 114. In other applications, the separation gaps 120 and 122 could be filledAttorney Docket No.2000P009-WO with other gases such as air, nitrogen, or argon. Vacuum could also be introduced in the separation gaps 120 and 122. As an example, vacuum is introduced in the separation gap 120 and 122 when measurements are performed inside a scanning electron microscope (SEM) or transmission electron microscope (TEM). The probe card 100A and / or LED wafer 100B could be mounted on a movable stage and the stage instructed to bring the probe card 100A and LED wafer 100B into proximity. The stage could be motor driven, piezoelectric, or manually operated. A computer program could be used to operate the stage. As an example, the LED wafer 100B could be placed on the chuck of a wafer prober and the probe card 100A placed above the LED wafer 100B. The chuck could be instructed through a computer program (or instructed manually) to move the LED wafer 100B in proximity to the probe tips 108 of the probe card 100A. A tilt alignment routine may be required to ensure that a constant separation gap 120 and 122 is maintained across all the probe tips 108 and first terminals 112 and second terminals 114.

[0089] With continued reference to FIG.1C, probes 104 and 106 are aligned to first terminals 112 and second terminals 114 respectively. A fixed potential difference could be applied across probes 104 and 106. As an example, a positive voltage is applied to probe 104 while probe 106 is electrically grounded. After the application of the potential difference, the movable stage is incrementally moved to bring the probe tips 108 closer to first terminals 112 and second terminals 114 of the LED. During the motion of the movable stage, the separation gaps 120 and 122 change and get smaller. The change in the separation gap 120 and 122 results in a change in the capacitance across probe 104 and first terminal 112 as well as probe 106 and second terminal 114. This change in capacitance as a function of the change in the separation gap 120 and 122 results in a motional current that forward biases the LED to switch on, light up, or emit electromagnetic radiation. The forward current flows from probe 104 through material forming the first probe tip 108 across the separation gap 120 into first terminal 112, then through the LED (diode) within the substrate 110, then out from the second terminal 114 through the separation gap 122, and then through material forming the second probe tip 108 into probe 106. Reference number 100C refers to an arrangement wherein the probes 104 and 106 are brought into proximity with the terminals 112 and 114 as shown in FIG.1C. FIG.1D is the electrical equivalent circuit that models the flow of the motional current as a function of changes in the separation gap 120 and 122.

[0090] With continued reference to FIG. 1D, voltage VA is applied to probe 104 while voltage VC is applied to probe 106. The movable stage is instructed to bring probes 104 and 106 into proximity with first terminals 112 and second terminals 114. The velocity of theAttorney Docket No.2000P009-WO movement of the movable stage along with the potential difference across probes 104 and 106 cause a motional current to flow from voltage VA through probe 104 (represented as resistor R1) and material forming probe tip 108 (represented as resistor R2). The motional current is transferred across the separation gap 120 (represented as capacitor C1) into first terminal 112 (represented as resistor R3) into the LED (represented as diode D1). The motional current then flows out from the LED through second terminal 114 (represented as resistor R4) across the separation gap 122 (represented as capacitor C2) into material forming probe tip 108 (represented as resistor R5) of the probe 106 (represented as resistor R6) to probe 106.

[0091] With continued reference to FIG.1D, for discussion purposes, the equivalent circuit could further be simplified into a current flowing through biased variable capacitors C1 and C2. The motional current can be expressed as: Equation 1where ^^is the motional current, ^^^is the potential difference between probes 104 and 106, ^^^is the change in capacitance across the separation gap 120, ^^ is the incremental step movement of the movable stage, and ^^ is the time it takes for the movable stage to make an incremental step movement.

[0092] With continued reference to FIG.1D, Equation 1 above suggests that the velocityat which the movable stage moves could influence the amount of current that flows in the LED. Higher velocities of motion of the movable stage could result in higher motional current flowing through the LED and causing the LED to switch on, light up, or emit electromagnetic radiation. The intensity or brightness of the emitted light from the LED is directly proportional to the motional current value. Higher motional currents result in brighter emitted lights. As the movable stage moves to bring the probe tips 108 into proximity with the first terminals 112 and second terminals 114, the capacitance across probe 104 and first terminal 112 is given by: Equation 2where ^^is the capacitance across probe 104 and first terminal 112, ^ is the permittivity of the substance located between the material and first terminal 112,Attorney Docket No.2000P009-WO ^ is the area of the first terminal 112, ^ is the original separation gap when the movable stage is not moving, and ^ is the incremental step movement of the movable stage. Differentiating Equation 2 with respect to the movement of the stage yields: Equation 3Sinceడ^ೞడ௭is directly proportional to the motional current (as shown in Equation 1), Equation 3 suggests that increasing the first terminal 112 area ^ while reducing the separation gap 120 ^^would increase the amount of motional current flowing through the LED.

[0093] While the movable stage moves to bring the probe tips 108 into proximity with the first terminals 112 and second terminals 114, the separation gap decreases and the LED is switched on. The LED is switched off when the movable stage ceases to move. There is a charge buildup across the separation gap which needs to be safely discharged. To discharge, the LED wafer 100B is retracted from the probe card 100A at a slower velocityడ௭to avoid generating a high reverse current in the light emitting device.

[0094] FIG.1E includes plots of the stage movement versus time, separation gap versus time, and motional current versus time. A potential difference is applied between probe 104 and 106. At time t0, the movable stage is instructed to incrementally move. As the stage incrementally moves by steps of z, the separation gap 120 and 122 decreases causing motional current (im) to begin to flow within the LED. The motional current flow causes the LED to switch on, light up, or emit electromagnetic radiation. At time t1, the movable stage ceases to move causing the separation gap (g-z) to be constant. Since there is no stage movement, ^^ ൌ ^ and change in capacitance ^^^ൌ ^ resulting in no current flow per Equation 1. Thus, the LED turns off from time t1 to t2 when the stage ceases to move. Although the LED is turned off, there is a charge buildup in the separation gap which needs to be carefully discharged to avoid causing electrostatic discharge which could potentially destroy the LEDs. With the potential difference still applied to probes 104 and 106, the discharge process is performed by instructing the movable stage to retract the LED wafer 100B away from the probe card 100A. The discharge process occurs from time t2 to t3. The discharge process generates a reverse current in the LED. To avoid generating significant reverse current, the movable stage is moved with a smallerAttorney Docket No.2000P009-WO velocityడ௭డ௧from time t2 to t3. At time t3, the movable stage is returned to its original location and ceases to move. At time t3, the LED is reset and another testing cycle could be initiated. The technique described above where current is generated within the LED by incrementally bringing at least a voltage biased probe into proximity or contact with an LED is referred to as velocity probing. The voltage bias could be DC, AC, or a high frequency signal.

[0095] FIG. 1F is a schematic view of the probe card 100A brought into contact with the LED wafer 100B. The velocity probing technique described in previous paragraphs could be used to switch the LED on and off. The probe tips 108 could be conductive or insulative. With a potential difference applied across probes 104 and 106, when the material of the probe tip 108 is conductive, then a mechanical contact between the probe tips 108 and first terminals 112 and second terminals 114 would result in a potential difference being directly applied between the first terminals 112 and second terminals 114. As long as the applied potential difference is greater than the turn-on voltage of the LED, then a DC current will flow though the LED and cause the LED to switch on, light-up, or emit electromagnetic radiation. Reference number 100D refers to an arrangement wherein the probe tips 108 of the probes 104 and 106 are brought into contact with the terminals 112 and 114 as shown in FIG.1F.

[0096] FIG.1G is the electrical equivalent circuit of FIG.1F where potential VA is applied to probe 104 and potential VC applied to probe 106. DC current flows from probe 104 (represented as resistor R7) through the material of the probe tip 108 (represented as resistor R9) then through the first terminal 112 (represented as resistor R11) through the LED (represented as diode D2) to second terminal 114 (represented as resistor R12). The DC current that comes out of second terminal 114 (represented as resistor R12) makes its way through the material of the probe tip 108 (represented as resistor R10) to probe 106 (represented as resistor R8).

[0097] FIG.1H includes plots corresponding the testing scheme. FIG.1H is similar to FIG. 1E with the key difference being that upon the probe tips 108 making contact with the first terminals 112 and second terminals 114, a higher or lower forward DC current could go through the LED based on the applied potential difference between probes 104 and 106. Between times t1 and t2 when probe tips 108 are in contact with first terminals 112 and second terminals 114, the applied potential difference to first terminals 112 and second terminals 114 could result in a forward DC current flowing through the LED.

[0098] FIG. 1I is a schematic view of the LED wafer 100E. Arrays of LED 100F are manufactured on the same substrate 110. A single LED 100F could comprise sapphireAttorney Docket No.2000P009-WO substrate, GaN buffer layer, n-GaN layer, quantum wells, p-GaN layer, quantum dots, Bragg reflectors, and metal contacts which form the first terminal 112 and second terminal 114.

[0099] FIG. 1J is a schematic view of the topside of a probe card 100G. Arrays of probes 100H are manufactured on the same substrate 102. Each probe 104 and / or 106 could have material forming a probe tip 108 attached at its apex. The pitch between probes 104 and 106 is the same as the pitch between the first terminals 112 and second terminals 114 of the LED 100F. Probes 104 could be electrically shorted with metal traces 124. The metal trace could be a transparent metal oxide such as indium tin oxide (ITO). Vias 128 electrically connects the metal traces 124 on the topside of the substrate 102 to the bottom side metal traces 124 of the same substrate 102. Probes 106 could be electrically shorted with metal traces 126. The metal trace 126 could be a transparent metal oxide such as indium tin oxide (ITO). Vias 130 electrically connect the metal traces 126 on the topside of the substrate 102 to the bottom side metal traces 126 of the same substrate 102. Screw holes 132 enable the probe card 100G to be aligned and screwed onto a carrier substrate such as a printed circuit board (PCB).

[0100] FIG.1K is a schematic view of the bottom side of a probe card 100G. Vias 128 are electrically shorted to probes 104 while vias 130 are electrically shorted to probes 106. Furthermore, vias 128 are electrically shorted to contact pad 138 through metal trace 134. Likewise, vias 130 are electrically shorted to contact pad 140 through metal trace 136. External electrical signals are transferred to the probes 104 and 106 through the contact pads 138 and 140. Contact pads 138 and 140 could be flip-chip bonded to a printed circuit board or soldered to electrical wires and connected to a source measure unit or a parameter analyzer.

[0101] In another embodiment, FIG.1L is a schematic view of the topside of a probe card 100K. Arrays of probes 100H are manufactured on the same substrate 102. Each probe 104 and 106 could have a material forming a probe tip 108 attached at its apex. The pitch between probes 104 and 106 is the same as the pitch between the first terminals 112 and second terminals 114 of the LED 100F. Vias 142 connect each probe 104 and 106 from the topside of the substrate 102 to the bottom side of the substrate 102. An active or passive switch matrix is monolithically integrated with the probe card. The active or passive switch matrix allows for each probe 104 or 106 to be individually addressed where each probes 104 or 106 could receive a specific electrical signal. When LED wafer 100E is tested with the probe card 100K which is integrated with a switch matrix, individual LEDs 100F could be switched on or off simultaneously or individually based on the selection / addressing scheme of the switch matrix.

[0102] The bottom side 100J of probe card 100G (as shown in FIG.1K) could be mounted onto the topside 200B of a carrier 200A. Carrier 200A is shown in FIG.2A. The carrier 200AAttorney Docket No.2000P009-WO could be a printed circuit board (PCB). The carrier substrate 202 forms an aperture 210 and has metal contacts 204 and 206. The metal contact 204 and 206 could be a metal pad, a spring- loaded feature, or a pogo pin. The screw holes 132 on the probe card 100G are aligned to the tapped holes 208 of the carrier substrate 202. Once aligned, screws 304 are used to secure the probe card 100G to the carrier 200A where the contact pads 138 and 140 of the probe card 100G make electrical contact to metal contacts 204 and 206 respectively. Vias could electrically connect the metal pads 204 and 206 on the topside 200B of the carrier substrate 202 to the bottom side 200C of the carrier substrate 202.

[0103] FIG.2B is a schematic view of the bottom side of the carrier 200A. Vias 212 and 214 electrically connect metal pads 204 and 206 respectively. One end of a first electrical wire could be soldered to via 212 and the other end connected to the source measure unit. One end of a second electrical wire could be soldered to via 214 and the other end connected to the source measure unit.

[0104] Referring to FIG.3A, the probe card 100G is aligned to the LED wafer 100E. A vision system 302 such as a camera is mounted above the probe card 100G to allow for the simultaneous viewing of the probes 104 and 106 along with the LEDs 100F. The vision system 302 could be a spectroradiometer or colorimeter capable of measuring the intensity, hue, color, lumens of the emitted light coming from the LED 100F. The vision system 302 could be scanned across the LED wafer 100E to collect the electroluminescence and photoluminescence properties of the LEDs 100F. A software program could be used to store the collected data. Multiple vision systems 302 could also be used to capture the emission information.

[0105] Referring to FIG 3B, the vision system 302 is positioned below the LED wafer 100E.

[0106] In another embodiment, and with continued reference to FIG.3A and FIG.3B, with the separation gaps 120 and 122 fixed, the probes 104 and 106 are aligned to the first terminals 112 and second terminals 114. An AC signal or high frequency signal is applied to probes 104 while probes 106 are electrically grounded. The high frequency signal could be a radiofrequency (RF) signal, microwave signal, infrared signal, or terahertz signal. If the frequency of the AC signal or high frequency signal corresponds to the resonance frequency of the light emitting device 100F, then a resonance current could be produced within the light emitting device 100F. At the resonance frequency, there is an internal amplification of the motional current flowing through the light emitting device. The resonance current will cause the light emitting device to emit light or electromagnetic radiation. Since the AC or high frequency signal is an alternating signal, in one cycle, the light emitting device could be switched on and off. The intensity or brightness of the emission is directly proportional to theAttorney Docket No.2000P009-WO amplitude or magnitude of the applied AC or high frequency signal. The technique of switching on and off a light emitting device at its resonance frequency is known as resonance probing. A high frequency vision system 302 could be used to measure the emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle of the light emitting devices 100F.

[0107] FIG. 4 is a schematic view of an imager 400. The imager 400 comprises of image sensors 404 on a frame 402. The image sensors 404 are capable of detecting and conveying electromagnetic information used to form an image. The image sensor 404 could be a charge- coupled device (CCD) or an active pixel sensor made of complementary metal oxide (CMOS). The sensing mechanism of the image sensor 404 could be light, ultraviolet, infrared, thermal, gigahertz, ultrasonic, terahertz, radar, sonar, and many more. The image sensor 404 could be attached directly to the LED wafer 100E or probe card 100G to produce an image of the LEDs 100F. The image sensor 404 could be as large as the LED wafer 100E to offer parallel imaging of all the LEDs 100F on the LED wafer 100E. A computer could be used to operate the image sensor 404 as well as display the imaging results on a monitor. Based on the generated image of the LEDs 100F, a computer vision program could be used to determine which LEDs 100F would pass or fail quality testing based on the color and / or intensity of the emitted light or electromagnetic radiation from the LEDs 100F. The computer vision program could also offer important yield analysis data such as binning the LEDs 100F based on their emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle. Process variations information across the LED wafer 100E could also be determined with the yield program by monitoring the distribution of passing or failing LEDs 100F across the wafer.

[0108] In another embodiment, the image sensor 404 could be a spectroradiometer or colorimeter that is capable of measuring the color, luminance, chromaticity, peak wavelength, and emission angle of the emitted light or electromagnetic radiation emitted from the LEDs 100F.

[0109] In another embodiment, the image sensor 404 comprises of materials or devices that are photon sensitive to the emission wavelength of the light or electromagnetic radiation emitted from the LEDs 100F. Such photon sensitive materials or devices could be diodes or field effect transistors.

[0110] FIG.5A is a schematic view of an imager 400 that is placed on top of a probe card 100G. The emitted electromagnetic radiation from the LEDs 100F will transmit through the probe card substrate 102 and reach on the image sensor 404. The image sensor 404 measuresAttorney Docket No.2000P009-WO and displays information such as emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle.

[0111] FIG.5B is a schematic view of an imager 400 that is attached to the LED wafer 100E. The emitted electromagnetic radiation from the LEDs 100F will transmit through the LED wafer substrate 110 and reach on the image sensor 404. The image sensor 404 measures and displays LED emission information such as emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle. The imager 402 along with the LED wafer 100E could be placed on the chuck of a wafer prober.

[0112] In another embodiment and in continued reference to FIG.5B, the image sensor 404 could be used as an excitation source to cause the LEDs 100F to light up and / or emit electromagnetic radiation. An example of an excitation source is a laser. A vision system 302 could be placed above the LED wafer 100E to measures and displays LED emission information such as emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle.

[0113] FIG.6 is a schematic view of a probe card 100G that is monolithically integrated with photon sensors 602. Each photon sensor 602 is sensitive to the electromagnetic radiation emitted from the light emitting device. An example of the photon sensor is the image sensor 404. The photon sensor 602 has the functions and operation of the image sensor 404 of FIG.4. The photon sensor 602 measures and displays light or electromagnetic radiation information such as emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle.

[0114] FIG.7A is a schematic view of a probe card 100G that is mounted on top of a LED wafer 100E. A vision system 302 is positioned above the probe card 100G. The LED wafer 100E comprises of vertical LEDs 700A with first terminals 112 located at the topside 116 of the LED substrate 110 and second terminals 114 located at the bottom side 118 of the LED substrate 110. The probes 104 are aligned to the first terminals 112 and a potential difference is applied between the probes 104 and second terminals 114 while either the probe card 100G or LED wafer 100E is moved towards each other. The movement of the probe card 100G and / or LED wafer 100E could be performed at constant velocity causing the separation gap 702 to change and induce a motional current to flow in the vertical LED 700A. The flow of current could cause the LED 700A to switch on, light up, and / or emit electromagnetic radiation. A vision system 302 could be used to image the switching on and off of the LEDs 700A as well as measure and display LED emission information such as emission intensity, emission power,Attorney Docket No.2000P009-WO emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle. The LED 700A is switched off when the LED wafer 100E is move away from the probe card 100G.

[0115] FIG.7B is a schematic view of the electrical equivalent circuit of the biased (voltage VA) probe 104 (represented as resistor R13) and material forming a probe tip 108 (represented as resistor R14) in proximity with the first terminal 112 (represented as resistor R15) of the LED 700A. The series resistance of the probe 104 is represented by resistor R13, material forming a probe tip 108 by resistor R14, the separation gap by variable capacitor C3, the resistance of the first terminal is represented by resistor R15, diode D3 represents the vertical light emitting device, capacitor C4 is the internal capacitance of the light emitting device that connects to the second terminal 114, and the second terminal is represented by resistor R16. A potential of voltage VD is applied to the second terminal 114.

[0116] FIG.7C is a schematic view of the electrical equivalent circuit of the biased (voltage VA) probe 104 (represented as resistor R17) and material forming a probe tip 108 (represented as resistor R18) in contact with the first terminal 112 (represented as resistor R19) of the LED 700A. The series resistance of the probe 104 is represented by resistor R17, material forming a probe tip 108 by resistor R18, the resistance of the first terminal is resistor R19, diode D4 represents the vertical light emitting device, capacitor C6 is the internal capacitance of the light emitting device that connects to the second terminal 114, and the second terminal is represented by 114. A potential of voltage VD is applied to the second terminal 114. The bias (voltage VD) to the second terminal 114 could be applied by the chuck of a wafer prober.

[0117] In another embodiment, and with continued reference to FIG.7A, with the probe 104 aligned to the first terminal 112 and a separation gap 702 fixed, an AC or high frequency signal is applied to probes 104 while the second terminals 114 are electrically grounded. The high frequency signal could be a radiofrequency (RF), microwave signal, infrared signal, or terahertz signal. If the frequency of the AC signal or high frequency signal corresponds to the resonance frequency of the light emitting device 700A, then a resonance current could be produced within the light emitting device 700A. At the resonance frequency, there is an internal amplification of the motional current flowing through the light emitting device. The resonance current will cause the light emitting device to emit light or electromagnetic radiation. Since the AC or high frequency signal is an alternating signal, in one cycle, the light emitting device could be switched on and off. The intensity or brightness of the emission is directly proportional to the amplitude or magnitude of the applied AC or high frequency signal. The technique of switching on and off a light emitting device at its resonance frequency is knownAttorney Docket No.2000P009-WO as resonance probing. A high frequency vision system 302 could be used to measure the emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle of the light emitting devices 700A. To turn off the LED 700A, the LED wafer 100E is moved away from the probe card 100G.

[0118] FIG. 8 is a schematic view of a probe card 100G that is mounted on top of a LED wafer 100E. An imager 400 is positioned above the probe card 100G. The LED wafer 100E comprises vertical LEDs 700A with first terminal 112 located on the topside 116 of the LED wafer substrate 110 and the second terminals 114 located at the bottom side 118 of the LED wafer substrate 110. With the probes 104 aligned to the first terminals 112, a potential difference is applied between the probes 104 and the second terminals 114 while either the probe card 100G and / or LED wafer 100E is moved towards each other. The movement of the probe card 100G and / or LED wafer 100E could be performed at constant velocity causing the separation gap 702 to change and induce a motional current to flow within the vertical LED 700A. The flow of current could cause the LED 700A to switch on, light up, and / or emit electromagnetic radiation. The image sensor 404 could be used to image the switching on and off of the LEDs 700A as well as measure and display LED emission information such as emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle. To turn off the LED 700A, the LED wafer 100E is moved away from the probe card 100G.

[0119] FIG. 9 is a schematic view of a probe card 100G that is mounted on top of a LED wafer 100E. The probe card 100G is monolithically integrated with photon sensors 602. The LED wafer 100E comprises of vertical LEDs 700A with first terminals 112 located at the topside 116 of the LED substrate 110 and the second terminals 114 located at the bottom side 118 of the LED wafer substrate 110. The probes 104 are aligned to the first terminals 112 and a potential difference is applied between the probes 104 and the second terminals 114 while either the probe card 100G and / or LED wafer 100E is moved towards each other. The movement of the probe card 100G and / or LED wafer 100E could be performed at constant velocity causing the separation gap 702 to change and induce a motional current to flow in the vertical LED 700A. The flow of current could cause the LED 700A to switch on. The photon sensors 602 could be used to image the switching on and off of the LEDs 700A as well as measure and display LED emission information such as emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, andAttorney Docket No.2000P009-WO emission angle. To turn off the LED 700A, the LED wafer 100E is moved away from the probe card 100G.

[0120] FIG.10 is a schematic view of a probe card 100G that is mounted on top of a LED wafer 100E. The probe card 100G comprises of a single probe 104 and material forming a probe tip 108. The probe 104 could be made of transparent metal oxide such as indium tin oxide (ITO) and the material forming the probe tip 108 could be made from a transparent material such as polydimethylsiloxane (PDMS) or epoxy-based photoresist such as SU-8. The material forming the probe tip 108 could also be a memristive material. Probe 104 and probe tip 108 could be as large as the size of the LED wafer 100E to allow for parallel testing of all vertical light emitting devices on the LED wafer 100E. The LED wafer 100E comprises of vertical LEDs 700A with first terminals 112 located at the topside 116 of the LED substrate 110 and second terminals 114 located at the bottom side 118 of the LED substrate 110. A potential difference is applied between the probe 104 and LED second terminals 114 while either the probe card 100G and / or LED wafer 100E is moved towards each other. The movement of the probe card 100G and / or LED wafer 100E could be performed at constant velocity causing the separation gap 702 to change and induce a motional current to flow in the vertical LED 700A. The flow of current could cause the LED 700A to switch on. Photon sensors 602 or vision system 302 could be used to image the switching on and off of the LEDs 700A as well as measure and display LED emission information such as emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle. To turn off the LED 700A, the LED wafer 100E is moved away from the probe card 100G.

[0121] With continued reference to FIG. 10, the LED wafer 100E could be scanned below the probe card 100G by move the XYZ translational stages of the wafer prober. As an example, the LED wafer 100E is placed on the chuck of a wafer prober, and at each location a velocity probing or resonance probing is performed. Thereafter, the chuck is translated in the XY plane then a new velocity or resonance probing is performed. At each location, a vision system 302 could be used to acquire an image of a single or an array of light emitting devices. A map of the emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle could be acquired and displayed on a computer monitor during the scanning process.

[0122] FIG.11A is a schematic view of a probe card 100G that is placed on top of an LED wafer 100E. The probe 104 is intentionally misaligned by a misalignment length 1102 in relation to the first terminals 112 and probe 106 is also intentionally misaligned by aAttorney Docket No.2000P009-WO misalignment length 1102 in relation to the second terminal 114. A fixed separation gap 1104 exist between the probes 104, 106, and first terminals 112 and second terminals 114. Switching on of the light emitting devices is achieved by applying a potential difference between the probes 104 and 106 and moving either the probe card 100G or LED wafer 100E in the x- direction (lateral direction) such that the probes 104 are aligned to the first terminals 112 and probes 106 are aligned to the second terminals 114 as shown in FIG. 11B. This lateral movement of either the probe card 100G or the LED wafer 100E at a constant velocity result in a forward motional current that flows from the probes 104 through material forming a probe tip 108 across the separation gap 1104 into first terminals 112 then through the LED then out from the second terminals 114 through the separation gap 1104 through material forming a probe tip 108 then into probes 106. The motional current could be expressed as: Equation 4where ^^is the motional current, ^^^ସ̴^^^is the potential difference between probes 104 and 106, ^^^is the change in the overlapping capacitance across the material forming the probe tip 108 and first terminal 112, ^^ is the incremental lateral movement of the movable stage, and ^^ is the time it takes for the movable stage to make an incremental lateral step movement. From Equation 4 above, the amount of motional current that flows through the light emitting device is a function of the velocityడ௫డ௧of the lateral movement of either the probe card 100G or the LED wafer 100E.

[0123] With continued reference to FIG.11A, FIG 11B, and Equation 4, at a fixed separation gap 1104, the capacitance between the probe tip 108 and first terminal 112 is given by:

[0124] Equation 5where ^^is the overlapping capacitance, ^ is the permittivity of the substance or gas that is present in the separation gap 1104, ^ is the overlapping area between the material forming the probe tip 108 and first terminal 112, and ^ is the separation gap 1104. When the material forming the probe tip 108 is misaligned with the first terminal 112, then the overlapping areaAttorney Docket No.2000P009-WO ^ ൌ ^ and the overlapping capacitance ^^ൌ ^. Thus, no motional current flows within the LED when there is a full misalignment. Furthermore, Equation 5 could be expressed as: ^^^ Equation 6 ^^ൌ ^ where ^ and ^ are the width and length (1106) of the first terminal 112, respectively, and ^ is the separation gap 1104. From Equation 6, the rate of change of the overlapping capacitance as a function of the length 1106 of the first terminal 112 could be expressed as: Equation 7

[0125] Equation 7 suggests that the motional current through the light emitting device could be further increased by increasing the permittivity value of the substance or gas that is present in the separation gap 1104, and / or increasing the width of the first terminal 112, and / or decreasing the separation gap 1104. As the movable stage is laterally moved to align probes 104 to first terminal 112 and probe 106 to second terminal 114, a motional current flow within the LED as the misalignment length 1102 decreases. Maximum motional current is achieved when the misalignment length approaches zero and the probes and terminals are fully aligned. When the lateral movement of either the probe card 100G or LED wafer 100E ceases, the motional current stops and the LED is switched off. To reset the light emitting device, either the probe card 100G or LED wafer 100E is moved back to its original position to misalign the probes 104, 106 to first terminals 112 and second terminal 114. Reset is performed with the lateral movement of the stage at the same or slower velocityడ௫డ௧while maintaining the potential difference^^^ସ̴^^^and separation gap g. A vision system 302 could be used to observe the switching on and off of the light emitting devices. The testing technique described in this section is referred to as lateral probing.

[0126] The lateral probing technique described in the previous paragraph could also be used to parallel test vertical light emitting devices such as those in FIG.7A. Referencing FIG.7A, initially, the probes 104 are misaligned with the first terminals 112 of the light emitting device 700A. A potential difference (^^^ସ̴^^ସ) is applied between the probes 104 and the second terminals 114 while the separation gap 702 is fixed. Either the probe card 100G or LED waferAttorney Docket No.2000P009-WO 100E is moved in the x-direction (lateral direction) at a constant velocityడ௫to generate a motional current in the LED device 700A. The LED is switched off when the movement of either the probe card 100G or LED wafer 100E ceases. To reset the light emitting device, either the probe card 100G or LED wafer 100E is moved back to its original position with the same or slower velocityడ௫while maintaining the potential difference^^^ସ̴^^ସand separation gap g. A vision system 302 could be used to observe the switching on and off of the LED devices 700A.

[0127] FIG.12 is a schematic view of a probe card 100G that is mounted on top of a LED wafer 100E. The probe card 100G comprises of a single probe 104 and material forming a probe tip 108. The probe 104 could be made of transparent metal oxide such as indium tin oxide (ITO) and the material forming the probe tip 108 could be made from a transparent material such as polydimethylsiloxane (PDMS) or epoxy-based photoresist such as SU-8. To prevent material forming the probe tip 108 from scratching or damaging terminals 112 upon contact, the material forming the probe tip 108 could be made from a polymer that is reversibly deformable. Probe 104 and probe tip 108 could be as large as the size of the LED wafer 100E to allow for parallel testing of all vertical light emitting devices on the LED wafer 100E. The LED wafer 100E comprises of vertical LEDs 700A with first terminals 112 located at the topside 116 of the LED substrate 110 and second terminals 114 located at the bottom side 118 of the LED substrate 110. A potential difference is applied between the probe 104 and LED second terminals 114 while either the probe card 100G and / or LED wafer 100E is moved towards each other. The movement of the probe card 100G and / or LED wafer 100E could be performed at constant velocity causing the separation gap 702 to change and induce a motional current to flow in the vertical LED 700A. The flow of current could cause the LED 700A to switch on. The movable stage ceases to move when material forming the probe tip 108 makes mechanical contact with terminals 112. A motion sensor 1202 could be monolithically integrated into the probe card 100G or LED wafer 100E to detect when the material forming the probe tip 108 makes contact or is in proximity with the first terminals 112. An example of the motion sensor 1202 could be a force sensor, capacitive sensor, proximity sensor, light sensor, etc. The LEDs 700A are switched off when the LED wafer 100E is separated from the probe card 100G. Photon sensors 602 or vision system 302 could be used to image the switching on and off of the LEDs 700A as well as measure and display LED emission information such as emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle.Attorney Docket No.2000P009-WO

[0128] It should be noted that the testing techniques described in previous paragraphs are not limited to the testing of light emitting devices with first terminal 112 and second terminal 114. The probe cards 100G could be used to test light emitting devices that have no terminals. The probes 104 and / or 106 along with the material forming the probe tip 108 could land directly on the LED 100F or 700A to test it. In addition, all movements of the movable stage could be performed while also ramping the potential difference between the at least a probe and at least a terminal of the light emitting device to cause the light emitting device to switch on, light up, and / or emit electromagnetic radiation. It should be noted that the non-contact testing techniques described in this application are non-destructive.

[0129] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0130] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

[0131] The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and / or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements can optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified.

[0132] As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e., “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.”

[0133] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elementsAttorney Docket No.2000P009-WO and not excluding any combinations of elements in the list of elements. This definition also allows that elements can optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified.

[0134] It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.

[0135] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively.

[0136] The above-described examples of the described subject matter can be implemented in any of numerous ways. For example, some aspects can be implemented using hardware, software, or a combination thereof. When any aspect is implemented at least in part in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single device or computer or distributed among multiple devices / computers.

[0137] The present disclosure can be implemented as a system, a method, and / or a computer program product at any possible technical detail level of integration. The computer program product can include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present disclosure.

[0138] The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium can be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such asAttorney Docket No.2000P009-WO punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.

[0139] Computer readable program instructions described herein can be downloaded to respective computing / processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and / or a wireless network. The network can comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and / or edge servers. A network adapter card or network interface in each computing / processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing / processing device.

[0140] Computer readable program instructions for carrying out operations of the present disclosure can be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state- setting data, configuration data for integrated circuitry, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++, or the like, and procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions can execute entirely on the user’s computer, partly on the user's computer, as a stand-alone software package, partly on the user’s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider). In some examples, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) can execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present disclosure.Attorney Docket No.2000P009-WO

[0141] Aspects of the present disclosure are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to examples of the disclosure. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer readable program instructions.

[0142] The computer readable program instructions can be provided to a processor of a, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. These computer readable program instructions can also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and / or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function / act specified in the flowchart and / or block diagram or blocks.

[0143] The computer readable program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus, or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0144] The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various examples of the present disclosure. In this regard, each block in the flowchart or block diagrams can represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks can occur out of the order noted in the Figures. For example, two blocks shown in succession can, in fact, be executed substantially concurrently, or the blocks can sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and / or flowchart illustration, and combinations of blocks in the block diagrams and / or flowchart illustration, can be implemented by special purposeAttorney Docket No.2000P009-WO hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.

[0145] Other implementations are within the scope of the following claims and other claims to which the applicant can be entitled.

[0146] While various examples have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the function and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the examples described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings is / are used. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, many equivalents to the specific examples described herein. It is, therefore, to be understood that the foregoing examples are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, examples can be practiced otherwise than as specifically described and claimed. Examples of the present disclosure are directed to each individual feature, system, article, material, kit, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and / or methods, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent, is included within the scope of the present disclosure.

Claims

Attorney Docket No.2000P009-WO Claims WHAT IS CLAIMED IS:

1. A method for testing light emitting devices, comprising the steps of: providing a probe card with at least two probes; applying a potential difference across a first probe and a second probe of the at least two probes; aligning the first probe and the second probe to a first terminal and a second terminal, respectively, of a light emitting device; and instructing a movable stage to bring the first probe and the second probe into proximity with the first terminal and the second terminal of the light emitting device; wherein a velocity of movement of the movable stage causes a motional current to be generated within the light emitting device; wherein the generated motional current causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation; wherein switching off the light emitting device is achieved by ceasing to move the movable stage and / or increasing a separation gap between one of the at least two probes and one of the first terminal or the second terminal of the light emitting device.

2. The method of Claim 1, wherein the first terminal and the second terminal of the light emitting device are located on the same side of a substrate of the light emitting device.

3. The method of Claim 1, wherein the first terminal and the second terminal of the light emitting device are located on opposite sides of a substrate of the light emitting device.

4. The method of Claim 1, wherein the first terminal is an anode and the second terminal is a cathode, or wherein the first terminal is a cathode and the second terminal is an anode.Attorney Docket No.2000P009-WO 5. The method of Claim 1, wherein the light emitting device wafer is scanned across a biased probe of the at least two probes while an imaging sensor generates an image of the light emitting devices.

6. The method of Claim 1, wherein an intensity or a power of the emitted light or electromagnetic radiation is directly proportional to the generated motional current that flows within the light emitting device.

7. The method of Claim 1, wherein an amount of the motional current is directly proportional to the velocity of the movement of the movable stage.

8. The method of Claim 1, wherein an amount of the motional current is directly proportional to the potential difference applied across the first terminal and the second terminal of the light emitting device.

9. The method of Claim 1, wherein an amount of motional current is inversely proportional to the separation gap between the one of the at least two probes and the one of the first terminal or the second terminal of the light emitting device.

10. The method of Claim 1, wherein an amount of motional current is directly proportional to an area of one of the first terminal or the second terminal of the light emitting device.

11. The method of Claim 1, wherein an amount of motional current is directly proportional to a permittivity value of a substance or a gas that is located between a probe tip of one of the at least two probes and one of the first terminal or the second terminal of the light emitting device.

12. The method of Claim 1, wherein the emitted light or electromagnetic radiation is measured with a vision system.

13. The method of Claim 12, wherein the vision system is capable of measuring emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and emission angle.Attorney Docket No.2000P009-WO 14. The method of Claim 1, wherein the probe card comprises: a substrate; the at least two probes made from a conductive material; wherein one of the at least two probes has a probe tip comprising a memristive material or a polymer.

15. The probe card of Claim 14, wherein the memristive material is configured to switch its state from conducting to insulating and vice versa.

16. The probe card of Claim 14, wherein the memristive material is a deformable material configured to reversibly deform when pushed against a device under test.

17. The probe card of Claim 14, wherein the memristive material comprises metal oxides, chalcogenides, amorphous silicon, carbon, and / or polymer- nanoparticles.

18. The probe card of Claim 14, wherein the memristive material is a phase change material.

19. The phase change material of Claim 18, wherein the phase change material comprises chalcogenide glass or Germanium Antimony Telluride.

20. The probe card of Claim 14, wherein the polymer is a deformable material configured to reversibly deform when pushed against a device under test.

21. The probe card of Claim 14, wherein the polymer comprises polydimethylsiloxane (PDMS) or an epoxy-based photoresist.

22. The probe card of Claim 14, wherein an active or passive switch matrix is monolithically integrated with the probe card.

23. The probe card of Claim 14, wherein at least a photon sensor is monolithically integrated into the probe card.Attorney Docket No.2000P009-WO 24. The probe card of Claim 23, wherein the photon sensor is configured to measure and display emitted light or electromagnetic radiation emission information such as emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, and / or emission angle.

25. A method for testing light emitting devices, comprising the steps of: providing a probe card with at least one probe; aligning a first probe of the at least one probe to a first terminal of a light emitting device; applying a potential difference across the first probe and a second terminal of the light emitting device; and instructing a movable stage to bring the first probe into proximity or contact with the first terminal of the light emitting device; wherein a velocity of movement of the movable stage causes a motional current to be generated within the light emitting device; wherein the generated motional current causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation; wherein switching off the light emitting device is achieved by ceasing to move the movable stage and / or increasing a separation gap between the first probe and one of the first terminal or the second terminal of the light emitting device.

26. The method of Claim 25, wherein the movement of the movable stage ceases when a motion sensor detects that a probe tip of the at least one probe is in proximity or contact with the first terminal of the light emitting device.

27. The method of Claim 26, wherein the motion sensor is monolithically integrated into the probe card or a substrate of the light emitting device wafer.

28. The method of Claim 26, wherein the motion sensor is a force sensor, capacitive sensor, proximity sensor, or a light sensor.

29. A method for testing light emitting devices, comprising the steps of: providing a probe card with at least two probes;Attorney Docket No.2000P009-WO aligning a first probe of the at least two probes to a first terminal of a light emitting device as well as aligning a second probe of the at least two probes to a second terminal of the light emitting device; applying a potential difference across the first probe and the second probe; and instructing a movable stage to bring the first probe and the second probe into contact with the first terminal and the second terminal of the light emitting device, respectively; wherein a velocity of the movable stage causes a motional current to be generated within the light emitting device; wherein the generated motional current is configured to cause the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation; wherein upon the first probe and the second probe establishing contact with the first terminal and the second terminal, respectively, a DC current flows within the light emitting device; wherein the DC current causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation; wherein switching off the light emitting device is achieved by ceasing to move the movable stage and increasing a separation gap between one of the at least two probes and one of the first terminal or the second terminal of the light emitting device.

30. A method for testing light emitting devices, comprising the steps of: providing a probe card with at least one probe; aligning a first probe to a first terminal of the light emitting device; creating a fixed separation gap between the first probe and the first terminal of the light emitting device; applying an AC or high frequency signal to the first probe, wherein a frequency of the AC or high frequency signal is at a resonance frequency of the light emitting device; electrically grounding a second terminal of the light emitting device; and generating a resonance current within the light emitting device which causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation.

31. A method for testing light emitting devices, comprising the steps of:Attorney Docket No.2000P009-WO providing a probe card with at least two probes; aligning a first probe of the at least two probes to a first terminal of the light emitting device as well as aligning a second probe of the at least two probes to a second terminal of the light emitting device; creating a fixed separation gap between the first probe and the first terminal of the light emitting device; applying an AC or high frequency signal to the first probe while electrically grounding the second probe, wherein a frequency of the AC or high frequency signal is at a resonance frequency of the light emitting device; and generating a resonance current within the light emitting device which causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation.

32. The method of Claim 30 and Claim 31, wherein an intensity or brightness of the emitted light or electromagnetic radiation is directly proportional to an amplitude or magnitude of the applied AC or high frequency signal.

33. The method of Claim 30 and Claim 31, wherein the high frequency signal is a radiofrequency signal, a microwave signal, an infrared signal, or a terahertz signal.

34. The method of Claim 32, wherein a vision system is used to measure emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, or emission angle.

35. The method of Claim 30 and Claim 31, wherein an image sensor is attached to the probe card or a substrate of the light emitting device.

36. The method of Claim 35, wherein the image sensor is configured to measure emission intensity, emission power, emission color, emission luminance, emission chromaticity, emission peak wavelength, or emission angle.Attorney Docket No.2000P009-WO 37. The method of Claim 35, wherein the image sensor comprises materials or devices that are photon sensitive to an emission wavelength of the light or electromagnetic radiations emitted from the light emitting device.

38. The method of Claim 37, wherein the materials or devices are diodes or field effect transistors.

39. The method of Claim 37, wherein the image sensor is an excitation source configured to excite the light emitting device to cause it to switch on, light up, emit light, and / or emit electromagnetic radiation.

40. The method of Claim 39, wherein the excitation source is a laser.

41. A method for testing light emitting devices, comprising the steps of: providing a probe card with at least one probe; creating a separation gap between a first probe of the at least one probe and a first terminal of a light emitting device; misaligning the first probe to the first terminal of the light emitting device; applying a potential difference across the first probe and a second terminal of the light emitting device; and instructing a movable stage to laterally align the first probe to the first terminal of the light emitting device; wherein a velocity of the movable stage causes a motional current to be generated within the light emitting device; wherein the generated motional current causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation; wherein switching off the light emitting device is achieved by ceasing to laterally move the movable stage and / or misaligning the first probe to the first terminal of the light emitting device.

42. A method for testing light emitting devices, comprising the steps of: providing a probe card with at least two probes; creating a first separation gap between at least a first probe of the at least two probes and a first terminal of a light emitting device;Attorney Docket No.2000P009-WO creating a second separation gap between a second probe of the at least two probes and a second terminal of the light emitting device; misaligning the first probe to the first terminal of the light emitting device; misaligning the second probe to the second terminal of the light emitting device; applying a potential difference across the first probe and the second probe; and instructing a movable stage to laterally align the first probe and the second probe to the first terminal and the second terminal of the light emitting device, respectively; wherein a velocity of the movable stage causes a motional current to be generated within the light emitting device; wherein the generated motional current causes the light emitting device to switch on, light up, emit light, or emit electromagnetic radiation; wherein switching off the light emitting device is achieved by ceasing to laterally move the movable stage and / or misaligning the first probe and the second probe to the first terminal and the second terminal of the light emitting device.

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