Patent ID: 12203971

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

FIG.1Ais a schematic diagram showing that energy band is bent when the first electrode and the second electrode of an LED die are open.FIG.1Bis a schematic diagram showing that energy band is not bent when the first electrode and the second electrode of an LED die are short-circuited.FIG.2shows the spectrum of secondary light measured after an LED die is irradiated with excitation light when the first electrode and the second electrode of the LED die are open and short-circuited.

Referring toFIG.1A, an embodiment of the disclosure utilizes the Quantum Confined Stark Effect (QCSE) to bend the energy band of LED dies100to be inspected. Under the action of an electric field, the spatial distribution and overlapping state of the wave functions of electrons and holes in the quantum wells of the LED dies100to be inspected are changed, so that the energy band of the LED dies100to be inspected is bent, resulting in a shift in the emission wavelength or a change in the light intensity of the LED dies100to be inspected. In an embodiment of the disclosure, the QCSE is applied to the inspection of the LED dies100, and an excitation light L1is used to irradiate the plurality of LED dies100to be inspected, so that the LED dies100to be inspected are excited by the excitation light L1to emit secondary light (not shown inFIG.1A).

Referring toFIG.1AandFIG.2, when the excitation light L1irradiates the LED dies100to be inspected to generate electrons and holes in the LED dies100to be inspected, since first electrodes102and second electrodes104of the LED dies100to be inspected are in an open-circuit state, electrons and holes generated in the LED dies100to be inspected are accumulated near the first electrodes102and the second electrodes104, respectively, and therefore a stronger internal electric field is formed in the LED dies100to be inspected. When the excitation light L1is irradiated on the LED dies100to be inspected in which the first electrodes102and the second electrodes104are in an open-circuit state, the stronger internal electric field formed in the LED dies100to be inspected causes the secondary light emitted by the LED dies100to be inspected to have a longer wavelength and a higher intensity. The wavelength includes the peak wavelength or dominant wavelength of the secondary light, and the intensity includes the intensity of the peak wavelength of the secondary light or the intensity of the overall spectrum of the secondary light. Here, the dominant wavelength refers to a weighted average value obtained by multiplying each wavelength by the weight thereof.

Referring toFIG.1BandFIG.2, when the excitation light L1irradiates the LED dies100to be inspected to generate electrons and holes in the LED dies100to be inspected, since the first electrodes102and the second electrodes104of the LED dies100to be inspected are in a short-circuit state, electrons and holes generated in the LED dies100to be inspected are not accumulated. Instead, the conductive first electrodes102and second electrodes104achieve electrical neutralization, thereby forming a weaker internal electric field reduction in the LED dies100to be inspected. When the excitation light L1is irradiated on the LED dies100to be inspected in which the first electrodes102and the second electrodes104are in a short-circuit state, the weaker internal electric field or lack of internal electric field formed in the LED dies100to be inspected causes the secondary light emitted by the LED dies100to be inspected to have a shorter wavelength and a lower intensity (compared to the state when the first electrodes102and the second electrodes104are in an open-circuit state). The wavelength includes the peak wavelength or dominant wavelength of the secondary light, and the intensity includes the intensity of the peak wavelength of the secondary light or the intensity of the overall spectrum of the secondary light.

As shown inFIG.2, if the LED dies100to be inspected are in a normal state, when the first electrodes102and the second electrodes104in the LED dies100are in a short-circuit state, the secondary light emitted by the LED dies100after being irradiated by the excitation light L1have a shorter wavelength and a smaller intensity, and when the first electrodes102and the second electrodes104in the LED dies100are in an open-circuit state, the secondary light emitted by the LED dies100have a longer wavelength and a higher intensity. In other words, during the inspection process, if it is observed that the secondary light emitted by the LED dies100after being irradiated by the excitation light L1have a certain degree of difference in wavelength and intensity under different states (i.e., the open-circuit state and the short-circuit state), then it may be determined that the LED dies100to be inspected are in a normal state. In contrast, during the inspection process, if it is observed that the secondary light emitted by the LED dies100does not have a certain degree of difference in wavelength or intensity under different states (i.e., the open-circuit state and the short-circuit state), it may be determined that the LED dies100to be inspected are in an abnormal state.

FIG.3shows the spectrum of secondary light measured after an LED die is irradiated with excitation light when different inspection bias voltages are applied between the first electrode and the second electrode of the LED die.

Referring toFIG.1AandFIG.3, in addition to that the first electrodes102and the second electrodes104of the LED dies100are in an open-circuit state (as shown inFIG.1A) or a short-circuit state (as shown inFIG.1B), during the inspection process of the LED dies100, different inspection bias voltages may be applied between the first electrodes102and the second electrodes104of the LED dies100, and then the LED dies100to be inspected are irradiated with the excitation light L1, and the spectrum of the secondary light emitted by the LED dies100to be inspected under different inspection bias voltages is measured. In an embodiment of the disclosure, inspection bias voltages are less than the threshold voltage (Vth) of the LED dies100.

As shown inFIG.3, during the inspection process of the LED dies100, different inspection bias voltages such as −3.0V, −2.0V, −1.0V, +1.0V, +1.5V, +2.5V, +2.6V are applied between the first electrodes102and the second electrodes104by using a probe to spot the diode dies, then the LED dies100to be inspected are irradiated with the excitation light L1, and the spectrum of the secondary light emitted by the LED dies100to be inspected under different inspection bias voltages is measured. It may be known fromFIG.3that when the inspection bias voltages applied between the first electrode102and the second electrode104are higher, the secondary light emitted by the normal LED die100to be inspected has a longer wavelength and a higher intensity. Similarly, during the inspection process of the LED dies100in the disclosure, an external inspection bias voltage may be applied between the first electrodes102and the second electrodes104of the LED dies100. If the LED dies100to be inspected are in a normal state, when different inspection bias voltages are applied between the first electrodes102and the second electrodes104of the LED dies100, the secondary light emitted by the LED dies100exhibits the change trend shown inFIG.3. During the inspection process, if it is observed that the change trend of the wavelength and intensity of the secondary light emitted by the LED dies100after being irradiated by the excitation light L1under different inspection bias voltage states is similar to the change trend inFIG.3, it may be determined that the LED dies100to be inspected are in a normal state. In contrast, during the inspection process, if it is observed that the change trend of the wavelength and intensity of the secondary light emitted by the LED dies100under different inspection bias voltage states is different from the change trend inFIG.3, it may be determined that the LED dies100to be inspected are in an abnormal state. For example, when the applied voltage is gradually increased from −3.0V to +2.6V, the corresponding peak wavelength of the secondary light is sequentially increased from 445 nm to 460 nm by about 2.5 nm to 3 nm. At this point, the change trend is similar to the change trend inFIG.3, and it may be determined that the LED dies100to be inspected are in a normal state; under the same applied voltage range, if the range in which the corresponding peak wavelength of the secondary light is sequentially increased exceeds a reasonable range (for example, sequentially increased by about 17 nm or about 0.2 nm, the overall size is larger or smaller), it may be determined that the LED dies100to be inspected are in an abnormal state. In other embodiments, the average value of the peak wavelengths of a plurality of LED dies to be inspected increasing with the increase of the applied voltage (hereinafter referred to as the peak wavelength incremental average value) may be used as a comparison benchmark. For example, assuming that the incremental average value of the peak wavelengths of a plurality of LED dies to be inspected is 2 nm as a comparison benchmark, when the incremental average value of the peak wavelength of a certain LED die to be inspected is about 2 nm, it may be determined that the LED die100to be inspected is in a normal state; if the incremental average value of the peak wavelength of a certain LED die to be inspected is 17 nm, then it may be determined that the LED die100to be inspected is in an abnormal state.

In other embodiments, under the same applied voltage, the average value of the peak wavelengths of a plurality of LED dies to be inspected (hereinafter referred to as the average value of peak wavelengths) may be used as a comparison benchmark. For example, assuming that the average value of the peak wavelengths of the plurality of LED dies to be inspected is Aa as a comparison benchmark, when the peak wavelength of a certain LED die to be inspected falls within the range of λa±(0.02λa), it may be determined that the LED die100to be inspected is in a normal state; if the peak wavelength of a certain LED die to be inspected does not fall within the range of (λa±0.02λa), it may be determined that the LED die100to be inspected is in an abnormal state. The above is an example where a deviation of 2% from the average value is regarded as abnormal. The threshold value may be changed according to requirements.

FIG.4A,FIG.4B,FIG.5A,FIG.5B,FIG.6A, andFIG.6Bare schematic diagrams showing an apparatus for inspecting LED dies according to the first embodiment of the disclosure.

Referring toFIG.4A,FIG.4B,FIG.5A,FIG.5B,FIG.6A, andFIG.6B, an apparatus200for inspecting LED dies is suitable for inspecting the plurality of LED dies100to be inspected at the same time. In some embodiments, the LED dies100to be inspected include a plurality of LED dies in a semiconductor wafer. In other embodiments, the LED dies100to be inspected include a plurality of LED dies bonded to a driving backplane. In the present embodiment, the LED dies100include the first electrodes102, the second electrodes104, and epitaxial layers106, wherein the first electrodes102and the second electrodes104are respectively distributed on the upper and lower sides of the epitaxial layers106, and the first electrodes102and the second electrodes104are electrically insulated from each other, and the first electrodes102and the second electrodes104are respectively electrically connected to different types of doped epitaxial material layers (e.g., P-type doped epitaxial material layer and N-type doped epitaxial material layer) in the epitaxial layers106. In other words, the LED dies100in the present embodiment are vertical-type LED dies.

As shown inFIG.4A,FIG.4B,FIG.5A,FIG.5B,FIG.6A, andFIG.6B, the apparatus200for inspecting LED dies includes an inspection substrate210, a light source220, an optical sensor230, and a computer240. In some embodiments, the inspection apparatus200may further include an optical device222and an optical device224, wherein the optical device222is a long-pass filter or a bandpass filter that may improve the spectral purity of a secondary light L2received by the optical sensor230, and the optical device224is a beam splitter or a dichroic filter capable of reflecting the excitation light L1or the secondary light L2. In some embodiments, the inspection substrate210has a conductive layer212, and the inspection substrate210is a rigid substrate or a flexible substrate that may be moved in the vertical direction. Via proper movement of the inspection substrate210, the conductive layer212on the inspection substrate210may make the first electrodes102and the second electrodes104of the LED dies100to be inspected be in different states. In other possible embodiments, the inspection substrate210has the conductive layer212, and the inspection substrate210is a rigid substrate or a flexible substrate disposed at different positions according to inspection requirements, and via proper setting of the inspection substrate210, the conductive layer212on the inspection substrate210may make the first electrodes102and the second electrodes104of the LED dies100to be inspected be in different states (e.g., short-circuit state, open-circuit state, or biased state). When the conductive layer212on the inspection substrate210is in contact with a conductive pad108B and the second electrodes104at the same time, the first electrodes102and the second electrodes104of the LED dies100to be inspected are in a short-circuit state, as shown inFIG.4AandFIG.4B. When a sufficient distance is maintained between the conductive layer212on the inspection substrate210and the second electrodes104of the conductive pad108B, the first electrodes102and the second electrodes104of the LED dies100to be inspected are in an open-circuit state, as shown inFIG.5AandFIG.5B. When a distance is maintained between the conductive layer212on the inspection substrate210and the conductive pad108B and the second electrodes104to enable non-contact electrical coupling, and when matched with a bias voltage applying device250electrically connected to the conductive layer212and the conductive pad108B, the LED dies100to be inspected are in a biased state, as shown inFIG.6AandFIG.6B. Here, non-contact electrical coupling means that the conductive layer212and the second electrodes104and the conductive pad108B are not in direct contact, but voltage is applied with an intermediate medium, such as: air or water gaps and a capacitive-like effect is formed.

As shown inFIG.4AandFIG.4B, the first electrode102of each of the LED dies100to be inspected may be electrically connected to the second electrode104of each of the LED dies100to be inspected via a conductive layer108A, the conductive pad108B, and the conductive layer212of the inspection substrate210. In other possible embodiments, the first electrode102of each of the LED dies100to be inspected may be integrated with the conductive layer108A to form the same conductive layer. In other words, the first electrode102may be omitted, and the conductive layer108A may be directly used as the electrode of each of the LED dies100to be inspected. As shown inFIG.4A, the optical device224reflects the excitation light L1and allows the secondary light L2to pass through, and the optical device222is used to improve the spectral purity of the secondary light L2passing through the optical device224. As shown inFIG.4B, the optical device224allows the excitation light L1to pass through and reflects the secondary light L2, and the optical device222is used to improve the spectral purity of the secondary light L2reflected by the optical device224.

As shown inFIG.5AandFIG.5B, the conductive layer212on the inspection substrate210may be kept a sufficient distance from the first electrodes102and the second electrodes104of the LED dies100to be inspected via proper movement or proper setting of the inspection substrate210, so that the first electrodes102and the second electrodes104of the LED dies100to be inspected are in an open-circuit state. In other possible embodiments, the first electrode102of each of the LED dies100to be inspected may be integrated with the conductive layer108A to form the same conductive layer. In other words, the first electrode102may be omitted, and the conductive layer108A may be directly used as the electrode of each of the LED dies100to be inspected. As shown inFIG.5A, the optical device224reflects the excitation light L1and allows the secondary light L2to pass through, and the optical device222is used to improve the spectral purity of the secondary light L2passing through the optical device224. As shown inFIG.5B, the optical device224allows the excitation light L1to pass through and reflects the secondary light L2, and the optical device222is used to improve the spectral purity of the secondary light L2reflected by the optical device224.

As shown inFIG.6AandFIG.6B, via the proper movement or proper setting of the inspection substrate210and with the bias voltage applying device250electrically connected to the conductive layer212, the conductive layer108A, and the conductive pad108B, the bias voltage applying device250may apply various inspection bias voltages between the first electrodes102and the second electrodes104of the LED dies100to be inspected via the conductive layer212and the conductive pad108B on the inspection substrate210. In other possible embodiments, the first electrode102of each of the LED dies100to be inspected may be integrated with the conductive layer108A to form the same conductive layer. In other words, the first electrode102may be omitted, and the conductive layer108A may be directly used as the electrode of each of the LED dies100to be inspected. As shown inFIG.6A, the optical device224reflects the excitation light L1and allows the secondary light L2to pass through, and the optical device222is used to improve the spectral purity of the secondary light L2passing through the optical device224. As shown inFIG.6B, the optical device224allows the excitation light L1to pass through and reflects the secondary light L2, and the optical device222is used to improve the spectral purity of the secondary light L2reflected by the optical device224.

The light source220provides the excitation light L1to irradiate the LED dies100to be inspected on the inspection substrate210, and the LED dies100to be inspected emit the secondary light L2after being irradiated by the excitation light L1, and the wavelength of L2is greater than the wavelength of L1. In some embodiments, the light source220includes UV light or other light sources sufficient to excite the LED dies100to be inspected to generate secondary light, such as an LED light source or a laser light source. In some embodiments, the excitation light L1provided by the light source220may be irradiated to some or all of the LED dies100to be inspected. The light source220is disposed below the inspection substrate210, and the optical sensor230is also disposed below the inspection substrate210. In other words, the light source220and the optical sensor230are disposed on the same side of the inspection substrate210.

When the first electrodes102and the second electrodes104of the LED dies100to be inspected are short-circuited, the optical sensor230captures the secondary light L2emitted by each of the LED dies100to be inspected, and the wavelength of L2is greater than the wavelength of L1. In some embodiments, the optical capture range of the optical sensor230covers a portion of the LED dies100to be inspected. In other words, the optical sensor230needs multiple optical captures to capture the secondary light L2emitted by all the LED dies100to be inspected. In other embodiments, the optical capture range of the optical sensor230may cover all the LED dies100to be inspected. In other words, the optical sensor230may capture the secondary light L2emitted by all the LED dies100to be inspected simply via a single optical capture.

In some embodiments, the optical sensor230includes a spectrometer that may be used to measure the peak wavelength, the dominant wavelength, and the intensity of the peak wavelength of the secondary light L2emitted by the LED dies100to be inspected. In the present embodiment, the spectrometer includes a line spectrometer, an area spectrometer, or other types of spectrometers. In other embodiments, the optical sensor230includes an image sensor capable of measuring the peak wavelength, the dominant wavelength, and the overall spectral intensity of the secondary light L2emitted by the LED dies100to be inspected. For example, an area light sensor with a filter or grating may be used to measure the peak wavelength or dominant wavelength of the secondary light L2emitted by the LED dies100to be inspected. In addition, an area light sensor may be used to measure the spectral intensity of the secondary light L2emitted by the LED dies100to be inspected.

FIG.7A,FIG.7B,FIG.8A, andFIG.8Bare schematic diagrams showing an apparatus for inspecting LED dies according to the second embodiment of the disclosure.

Referring toFIG.7A,FIG.7B,FIG.8A, andFIG.8B, an apparatus200′ for inspecting LED dies is suitable for inspecting a plurality of LED dies100′ to be inspected at the same time. In some embodiments, the LED dies100′ to be inspected include a plurality of LED dies in a semiconductor wafer. In other embodiments, the LED dies100′ to be inspected include a plurality of LED dies bonded to a driving backplane. In the present embodiment, the LED dies100′ include first electrodes102′, second electrodes104′, and epitaxial layers106′, wherein the first electrodes102′ and the second electrodes104′ are distributed on the same side (for example, the upper side) of the epitaxial layers106′, and the first electrodes102′ and the second electrodes104′ are electrically insulated from each other, and the first electrodes102′ and the second electrodes104′ are respectively electrically connected to different types of doped epitaxial material layers (e.g., P-type doped epitaxial material layer and N-type doped epitaxial material layer) in the epitaxial layers106′. In other words, the LED dies100′ in the present embodiment are horizontal-type LED dies. As shown inFIG.7AandFIG.8A, the optical device224reflects the excitation light L1and allows the secondary light L2to pass through, and the optical device222is used to improve the spectral purity of the secondary light L2passing through the optical device224. As shown inFIG.7BandFIG.8B, the optical device224allows the excitation light L1to pass through and reflects the secondary light L2, and the optical device222is used to improve the spectral purity of the secondary light L2reflected by the optical device224.

The apparatus200for inspecting the LED dies shown inFIG.7A,FIG.7B,FIG.8A, andFIG.8Bis the same as the apparatus200for inspecting the LED dies shown inFIG.4A,FIG.4B,FIG.5A,FIG.5B,FIG.6AandFIG.6B, and therefore the structural details of the inspection apparatus200are not repeated herein.

In the present embodiment, the inspection substrate210has a conductive layer212, and the inspection substrate210is a rigid substrate or a flexible substrate that may be moved in the vertical direction. Via proper movement of the inspection substrate210, the conductive layer212on the inspection substrate210may make the first electrodes102′ and the second electrodes104′ of the LED dies100′ to be inspected be in different states. When the conductive layer212on the inspection substrate210is in contact with the first electrodes102′ and the second electrodes104′ at the same time, the first electrodes102′ and the second electrodes104′ of the LED dies100′ to be inspected are in a short-circuit state, as shown inFIG.7AandFIG.7B. When a sufficient distance is maintained between the conductive layer212on the inspection substrate210and the first electrodes102′ and the second electrodes104′, the first electrodes102′ and the second electrodes104′ of the LED dies100′ to be inspected are in an open-circuit state, as shown inFIG.8AandFIG.8B.

Referring toFIG.4A,FIG.4B,FIG.5A,FIG.5B,FIG.7A,FIG.7B,FIG.8A, andFIG.8B, the computer240is electrically connected to the optical sensor230to receive the output of the optical sensor230.

In some embodiments, the output of the optical sensor230includes a plurality of first spectra captured when the first electrodes102and102′ and the second electrodes104and104′ of the LED dies100and100′ to be inspected are in an open-circuit state (as shown inFIG.5A,FIG.5B,FIG.8A, andFIG.8B), and a plurality of second spectra captured when the first electrodes102and102′ and the second electrodes104and104′ of the plurality of LED dies100and100′ to be inspected are in a short-circuit state (as shown inFIG.4A,FIG.4B,FIG.7A, andFIG.7B). Moreover, the computer240may be used to compare the difference between the first spectra and the second spectra. Here, the difference between the first spectra and the second spectra includes a difference in peak wavelength, a difference in dominant wavelength, a difference in peak wavelength intensity, or a difference in spectral intensity.

In some embodiments, the output of the optical sensor230includes a plurality of first spectra captured when the first electrodes102and102′ and the second electrodes104and104′ of the LED dies100and100′ to be inspected are in an open-circuit state (as shown inFIG.5A,FIG.5B,FIG.8A, andFIG.8B), and a plurality of third spectra captured when the first electrodes102and102′ and the second electrodes104and104′ of the LED dies100and100′ to be inspected are subjected to an inspection voltage bias (as shown inFIG.6AandFIG.6B). Moreover, the computer240may be used to compare the difference between the first spectra and the third spectra, and the difference between the first spectra and the third spectra includes a difference in peak wavelength, a difference in dominant wavelength, a difference in peak wavelength intensity, or a difference in spectral intensity.

In some embodiments, the output of the optical sensor230includes a plurality of second spectra captured when the first electrodes102and102′ and the second electrodes104and104′ of the LED dies100and100′ to be inspected are in a short-circuit state (as shown inFIG.4A,FIG.4B,FIG.7A, andFIG.7B), and a plurality of third spectra captured when the first electrodes102and102′ and the second electrodes104and104′ of the LED dies100and100′ to be inspected are subjected to an inspection voltage bias (as shown inFIG.6AandFIG.6B). Moreover, the computer240may be used to compare the difference between the second spectra and the third spectra, and the difference between the second spectra and the third spectra includes a difference in peak wavelength, a difference in dominant wavelength, a difference in peak wavelength intensity, or a difference in spectral intensity.

In some embodiments, the output of the optical sensor230includes a plurality of second spectra captured when the first electrodes102and102′ and the second electrodes104and104′ of the LED dies100and100′ to be inspected are in a short-circuit state (as shown inFIG.4A,FIG.4B,FIG.7A, andFIG.7B), and the computer240may be used to compare the difference of the second spectra, and the difference of the second spectra includes a difference in peak wavelength, a difference in dominant wavelength, a difference in peak wavelength intensity, or a difference in spectral intensity. It should be noted that although the above method may not detect the short-circuit defect in the LED dies100and100′ to be inspected themselves, in addition to the above situation, in the above method, the computer240may still compare the difference of the second spectra, and then determine whether the LED dies100and100′ to be inspected have other abnormal conditions or classify them into different grades.

In some embodiments, the output of the optical sensor230includes a plurality of third spectra captured when the first electrodes102and102′ and the second electrodes104and104′ of the LED dies100and100′ to be inspected are subjected to a plurality of inspection bias voltages, and the computer240may be used to compare the difference of the third spectra, and the difference of the third spectra includes a difference in peak wavelength, a difference in dominant wavelength, a difference in peak wavelength intensity, or a difference in spectral intensity.

In some embodiments, the output of the optical sensor230includes a plurality of third spectra captured when the first electrodes102and102′ and the second electrodes104and104′ of the LED dies100and100′ to be inspected are subjected to the same inspection bias voltage, and the computer240may be used to compare the difference of the third spectra, and the difference of the third spectra includes a difference in peak wavelength, a difference in dominant wavelength, a difference in peak wavelength intensity, or a difference in spectral intensity.

FIG.9shows the spectrum of secondary light measured when a normal LED die is irradiated with different excitation light.

Referring toFIG.9, in the present embodiment, when the P and N electrodes of the LED die are in an open-circuit state and a short-circuit state, the LED die to be inspected is irradiated with excitation light of three different intensities I1, I2, and I3, respectively, wherein the excitation light of three different intensities I1, I2, and I3are obtained by the light source passing through different intensity attenuators (for example, OD0.6, OD1, OD2), wherein the intensity I1is the largest, the intensity I2is smaller, and the intensity I3is the smallest. When the P and N electrodes of the LED die are in an open-circuit state, the normal LED die to be inspected is irradiated with the excitation light of the intensity I1, and the optical sensor may capture a spectrum I1 openof the secondary light; when the P and N electrodes of the LED die are in a short-circuit state, the normal LED die to be inspected is irradiated with excitation light of intensity I1, and the optical sensor may capture a spectrum I1 shortof the secondary light; when the P and N electrodes of the LED die are in an open-circuit state, the normal LED die to be inspected is irradiated with the excitation light of the intensity I2, and the optical sensor may capture a spectrum I2 openof the secondary light; when the P and N electrodes of the LED die are in a short-circuit state, the normal LED die to be inspected is irradiated with the excitation light of the intensity I2, and the optical sensor may capture a spectrum I2 shortof the secondary light; when the P and N electrodes of the LED die are in an open-circuit state, the normal LED die to be inspected is irradiated with the excitation light of the intensity I3, and the optical sensor may capture a spectrum I3 openof the secondary light; and when the P and N electrodes of the LED die are in a short-circuit state, the normal LED die to be inspected is irradiated with the excitation light of the intensity I3, and the optical sensor may capture a spectrum I3 shortof the secondary light.

It may be known fromFIG.9that for a normal LED die to be inspected, the peak wavelengths or dominant wavelengths of the spectra I1 open, I2 open, and I3 openof the secondary light captured by the optical sensor are respectively greater than the peak wavelengths or dominant wavelengths of the spectra I1 short, I2 short, and I3 short. In other words, compared to the spectra I1 open, I2 open, I3 open, the spectra I1 short, I2 short, and I3 shorthave a phenomenon of blue shift, wherein the amount of the blue shift is related to the intensities I1, I2, and I3of the excitation light. In an embodiment, the difference between the peak wavelength or dominant wavelength in a short-circuit condition and the peak wavelength or dominant wavelength in an open-circuit condition may be 5 nm to 30 nm. Moreover, the peak wavelength intensities or spectral intensities of the spectra I1 open, I2 open, and I3 openare respectively greater than the peak wavelength intensities or spectral intensities of the spectra I1 short, I2 short, and I3 short. In an embodiment, the peak wavelength intensity, dominant wavelength intensity, or spectral intensity in a short-circuit condition may be 0.5× to 1× the peak wavelength intensity, dominant wavelength intensity, or spectral intensity in an open-circuit condition.

FIG.10shows the spectrum of secondary light measured when different excitation light is irradiated on an LED die with significant leakage current phenomenon.

Referring toFIG.10, when the P and N electrodes of the LED die are in an open-circuit state, the LED die to be inspected with significant leakage current phenomenon is irradiated with the excitation light of the intensity I1, and the optical sensor may capture the spectrum I1 openof the secondary light; when the P and N electrodes of the LED die are in a short-circuit state, the LED die to be inspected with significant leakage current phenomenon are irradiated with excitation light of intensity I1, and the optical sensor may capture the spectrum I1 shortof the secondary light; when the P and N electrodes of the LED die are in an open-circuit state, the LED die to be inspected with significant leakage current phenomenon is irradiated with the excitation light of the intensity I2, and the optical sensor may capture the spectrum I2 openof the secondary light; when the P and N electrodes of the LED die are in a short-circuit state, the LED die to be inspected with significant leakage current phenomenon is irradiated with the excitation light of the intensity I2, and the optical sensor may capture the spectrum I2 shortof the secondary light; when the P and N electrodes of the LED die are in an open-circuit state, the LED die to be inspected with significant leakage current phenomenon is irradiated with the excitation light of the intensity I3, and the optical sensor may capture the spectrum I3 openof the secondary light; and when the P and N electrodes of the LED die are in a short-circuit state, the LED die to be inspected with significant leakage current phenomenon is irradiated with the excitation light of the intensity I3, and the optical sensor may capture the spectrum I3 shortof the secondary light.

It may be known fromFIG.10that for the LED die to be inspected with significant leakage current phenomenon, the peak wavelengths or dominant wavelengths of the spectra I1 open, I2 open, and I3 openof the secondary light captured by the optical sensor may be close to or even consistent with the peak wavelengths or dominant wavelengths of the spectra I1 short, I2 short, and I3 short. In other words, compared with the spectra I1 open, I2 open, and I3 open, the blue-shift phenomenon of the spectra I1 short, I2 short, and I3 shortis less significant or even disappears. In addition, the peak wavelength intensities or spectral intensities of the spectra I1 open, I2 open, and I3 openmay be close to or even consistent with the peak wavelength intensities or spectral intensities of the spectra I1 short, I2 short, and I3 short.

FIG.11shows the spectrum of secondary light measured when excitation light with weaker intensity is irradiated on an LED die with slight leakage current.

Referring toFIG.11, when the P and N electrodes of the LED die are in an open-circuit state, the LED die to be inspected with a slight leakage current phenomenon is irradiated with the excitation light of intensity I2, and the optical sensor may capture the spectrum I2 openof the secondary light; when the P and N electrodes of the LED die are in a short-circuit state, the LED die to be inspected with a slight leakage current phenomenon is irradiated with the excitation light of the intensity I2, and the optical sensor may capture the spectrum I2 shortof the secondary light; when the P and N electrodes of the LED die are in an open-circuit state, the LED die to be inspected with a slight leakage current phenomenon is irradiated with the excitation light of intensity I3, and the optical sensor may capture the spectrum I3 openof the secondary light; and when the P and N electrodes of the LED die are in a short-circuit state, the LED die to be inspected with a slight leakage current phenomenon is irradiated with the excitation light of the intensity I3, and the optical sensor may capture the spectrum I3 shortof the secondary light.

It may be known fromFIG.11that, for the LED die to be inspected with slight leakage current, the peak wavelengths or dominant wavelengths of the spectra I2 openand I3 openof the secondary light captured by the optical sensor are close to or even consistent with the peak wavelengths or dominant wavelengths of the spectra I2 shortand I3 short. In other words, relative to the spectrum I3 open, the blue shift phenomenon of the spectrum I3 shortis less significant or even disappears. As described above, by properly selecting the intensity of the excitation light, the slight leakage current phenomenon of the LED die to be inspected may be detected.

FIG.12andFIG.13respectively show the spectrum of secondary light measured when an LED die with abnormal forward voltage (Vf) is irradiated with excitation light of weaker intensity I2and I3, andFIG.14shows the spectrum of secondary light measured when an LED die with abnormal forward voltage (Vf) is irradiated with excitation light of weaker intensity.

Referring toFIG.12andFIG.13, when the P and N electrodes of the LED die are in an open-circuit state, the LED die to be inspected with abnormal forward voltage (Vf) is irradiated with the excitation light of intensity I2, and the optical sensor may capture the spectrum I2 openof the secondary light; when the P and N electrodes of the LED die are in a short-circuit state, the LED die to be inspected with abnormal forward voltage (Vf) is irradiated with the excitation light of the intensity I2, and the optical sensor may capture the spectrum I2 shortof the secondary light; when the P and N electrodes of the LED die are in an open-circuit state, the LED die to be inspected with abnormal forward voltage (Vf) is irradiated with the excitation light of intensity I3, and the optical sensor may capture the spectrum I3 openof the secondary light; and when the P and N electrodes of the LED die are in a short-circuit state, the LED die to be inspected with abnormal forward voltage (Vf) is irradiated with the excitation light of the intensity I3, and the optical sensor may capture the spectrum I3 shortof the secondary light.

It may be known fromFIG.12that, for the LED die to be inspected with abnormal forward voltage (Vf), the peak wavelength or dominant wavelength of the spectrum I2 openof the secondary light captured by the optical sensor is close to or even consistent with the peak wavelength or dominant wavelength of the spectrum I2 short. In other words, relative to the spectrum I2 open, the blue shift phenomenon of the spectrum I2 shortis less significant or even disappears. In addition, the peak wavelength intensity, dominant wavelength intensity, or spectral intensity of spectrum I2 shortis less than one-half of the peak wavelength intensity, dominant wavelength intensity, or spectral intensity of spectrum I2 open.

It may be known fromFIG.13that, for the LED die to be inspected with abnormal forward voltage (Vf), the peak wavelength or dominant wavelength of the spectrum I3 openof the secondary light captured by the optical sensor is less than the peak wavelength or dominant wavelength of the spectrum I3 short. In other words, compared to the spectrum I3 open, the spectrum I3 shortmay have a red shift phenomenon. In addition, the peak wavelength intensity, dominant wavelength intensity, or spectral intensity of spectrum I2 shortis less than one-half of the peak wavelength intensity, dominant wavelength intensity, or spectral intensity of spectrum I2 open. As mentioned above, by properly selecting the intensity of the excitation light, the abnormal phenomenon of the forward voltage (Vf) of the LED die to be inspected may be detected.

It may be known fromFIG.14that, for the LED die to be inspected with abnormal forward voltage (Vf), the peak wavelength intensity, dominant wavelength intensity, or spectral intensity of the spectrum I3 shortof the secondary light captured under a suitable excitation light intensity is less than one-third of the peak wavelength intensity, dominant wavelength intensity, or the spectral intensity of the spectrum I3 open. As mentioned above, by properly selecting the intensity of the excitation light, the abnormal phenomenon of the forward voltage (Vf) of the LED die to be inspected may be detected.

In the embodiments of the disclosure, by performing statistics and analysis on the spectra of a large number of captured secondary light, and by the methods described inFIG.9toFIG.13, abnormal LED dies with outlier data may be found. For example, when the spectral data of the secondary light emitted by a certain LED die to be inspected is different from the spectral data of the secondary light emitted by other LED dies to be inspected, and when the difference exceeds a certain threshold, the LED die to be inspected may be determined as abnormal or classified into a different grade.

Based on the above, the electrodes of the LED dies to be inspected in the above embodiments of the disclosure provide excitation light under different conditions (e.g., open-circuit, short-circuit, and/or subject to inspection bias voltage), the secondary light emitted by the LED dies is captured under the above different conditions, and whether the LED dies are abnormal or not or classified is determined according to the captured secondary light. Therefore, the embodiments of the disclosure may efficiently inspect all LED dies in the wafer, all LED dies mounted on the driving backplane but not fully electrically connected to the driving backplane, or all LED dies bonded to the driving backplane.