Test method, manufacturing method, and microdisplay

Abstract

Provided is a test method for a wafer on which a plurality of pixel ICs are formed, the test method comprising: preparing the wafer, each of the plurality of pixel ICs including a plurality of LEDs, a test driver that drives the plurality of LEDs, and a driver electrode that is different from the test driver and to which a separate driver for driving the plurality of LEDs is to be electrically connected; and optically testing the wafer by driving the plurality of LEDs with the test driver.

Description

Test method, manufacturing method, and microdisplay

[0001] The present invention relates to a test method, a manufacturing method, and a microdisplay.

[0002] According to machine translation, Patent Document 1 states that "When testing a small and medium-sized TFT-LCD, press the test points of the corresponding test panel and connect the corresponding interface cable from the CON20 pin header. When pressing the test hardware switch, the panel can display different colors of red, green, blue, black, white, and various gray scale images, so defective panels can be detected." (0056). According to machine translation, Patent Document 2 states that "The liquid crystal display panel initializes the driving chip according to the initialization setting parameters transmitted from the encoder 28 and displays the image signal transmitted from the encoder 28 according to the timing parameters, thereby realizing the test of the liquid crystal display panel." (0030). According to machine translation, Patent Document 3 states that "The TCON circuit 101 controls the source driving circuit 207 based on the corrected test data to drive the LED display panel, and at the same time performs optical measurement to sense the LED and obtain LED error information." (0031). [Prior art documents] [Patent documents] [Patent Document 1] CN202434176U [Patent Document 2] CN204807860U [Patent Document 3] US20190139497A1 General disclosure

[0003] In a first aspect of the present invention, a test method for a wafer on which a plurality of pixel ICs are formed is provided. The test method includes preparing the wafer, wherein each of the plurality of pixel ICs includes a plurality of LEDs, a test driver for driving the plurality of LEDs, and an electrode for a driver to which a separate driver for driving the plurality of LEDs, different from the test driver, is electrically connected, and driving the plurality of LEDs with the test driver to optically test the wafer.

[0004] In the above-described test method, the optical test may include outputting a test image of a monochromatic or geometric pattern, consisting of at least one of an illuminated state and a non-illuminated state, from the test driver to the plurality of LEDs.

[0005] In any of the above test methods, the optical test may include probing into the package electrodes included in each of the plurality of pixel ICs, without probing into the electrodes for the driver, and sending an electrical signal to the plurality of LEDs for optically testing the wafer.

[0006] In any of the above test methods, the plurality of LEDs may be OLEDs. Any of the above test methods may further include electrically testing the wafer by probing at least one of the package electrodes included in each of the plurality of pixel ICs and the cathode electrodes exposed in the region where the OLEDs will be deposited, before the OLEDs are deposited on the wafer.

[0007] In any of the above test methods, the plurality of LEDs may be microLEDs. The above test method may further comprise testing the wafer electrically by probing at least one of the package electrodes included in each of the plurality of pixel ICs and the cathode electrodes exposed in the region where the microLEDs will be transferred, before the microLEDs are transferred to the wafer.

[0008] Any of the above test methods may further include determining whether each of the plurality of pixel ICs is a good product based on the results of the electrical test and the optical test.

[0009] A second aspect of the present invention provides a method for manufacturing a microdisplay. The manufacturing method comprises preparing a wafer on which a plurality of pixel ICs are formed, wherein each of the plurality of pixel ICs includes a plurality of LEDs, a test driver for driving the plurality of LEDs, and driver electrodes to which a separate driver, different from the test driver, will be electrically connected for driving the plurality of LEDs; optically testing the wafer by driving the plurality of LEDs with the test driver; determining whether each of the plurality of pixel ICs is good or not based on the results of the optical test; cutting out the plurality of pixel ICs from the wafer; and assembling the microdisplay by attaching the separate driver to the pixel ICs determined to be good and electrically connecting the separate driver to the plurality of LEDs via the driver electrodes.

[0010] In the above manufacturing method, the optical test may include probing into the package electrodes included in each of the plurality of pixel ICs, without probing into the electrodes for the driver, and sending an electrical signal to the plurality of LEDs for optically testing the wafer.

[0011] Any of the above manufacturing methods may further include, at least after the optical test, grounding the package electrodes used to pass the electrical signal for optically testing the wafer to the plurality of LEDs.

[0012] In any of the above manufacturing methods, the plurality of LEDs may be OLEDs. The above manufacturing method may further include electrically testing the wafer by probing at least one of the package electrodes included in each of the plurality of pixel ICs and the cathode electrodes exposed in the region where the OLEDs will be deposited, before the OLEDs are deposited on the wafer.

[0013] In any of the above manufacturing methods, the plurality of LEDs may be microLEDs. The above manufacturing method may further include electrically testing the wafer by probing at least one of the package electrodes included in each of the plurality of pixel ICs and the cathode electrodes exposed in the region where the microLEDs will be placed, before the microLEDs are transferred to the wafer.

[0014] In any of the above manufacturing methods, determining whether each of the plurality of pixel ICs is a good product may include determining whether each of the plurality of pixel ICs is a good product based on the results of the electrical test and the results of the optical test.

[0015] Any of the above manufacturing methods may further include, after the assembly of the microdisplay, driving the plurality of LEDs with the separate driver to optically test the microdisplay.

[0016] In any of the above manufacturing methods, optical testing of the microdisplay may include probing the package electrodes included in the pixel IC and sending an electrical signal for optical testing of the microdisplay to the plurality of LEDs.

[0017] Any of the above manufacturing methods may further include electrically testing the microdisplay by probing the package electrodes included in the pixel IC after the microdisplay has been assembled.

[0018] In any of the above manufacturing methods, the test driver may be formed with looser design rules than the separate driver.

[0019] A third embodiment of the present invention provides a microdisplay. The microdisplay comprises a pixel IC including a plurality of LEDs and a test driver, and a separate driver attached to the pixel IC, which is different from the test driver, and which drives the plurality of LEDs.

[0020] In the above-mentioned microdisplay, the test driver may be designed with looser design rules than the separate driver.

[0021] In any of the above microdisplays, the pixel IC may include a package electrode that is grounded while electrically connected to the test driver.

[0022] It should be noted that the above summary of the invention does not enumerate all of its features. Furthermore, subcombinations of these features may also constitute an invention.

[0023] This is a flowchart illustrating an example of the operation flow for manufacturing a microdisplay 50 in a manufacturing line 10 according to one embodiment. This is a flowchart illustrating an example of the manufacturing flow for manufacturing a microdisplay 50 in a manufacturing line 10 according to one embodiment. This is a schematic plan view showing an example of a pixel IC (Integrated Circuit) 100. This is a schematic plan view showing an example of a microdisplay 50.

[0024] The present invention will be described below through embodiments, but these embodiments are not intended to limit the scope of the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0025] Figures 1 and 2 are flowcharts illustrating an example of a manufacturing flow for manufacturing a microdisplay 50 in a manufacturing line 10 according to one embodiment. In Figures 1 and 2, the manufacturing line 10 is shown with a dashed frame. In Figure 1, a portion of the manufacturing line 10 is omitted with a wavy line, and this omitted portion is shown in Figure 2. In Figures 1 and 2, the flow direction of the manufacturing flow is indicated by white arrows, the way in which objects such as wafers enter and exit various devices included in the manufacturing line 10 is indicated by thick black arrows, and the flow direction of information such as test results is indicated by thin arrows.

[0026] The manufacturing line 10 according to this embodiment manufactures and tests microdisplays 50 and ships the microdisplays 50 that are determined to be good products. The microdisplays 50 manufactured on the manufacturing line 10 are display devices that display images with a resolution of 2K or higher, for example, 2K or 4K resolution, and are packaged by bonding together a pixel IC 100 and a driver 200 manufactured from separate wafers, namely a pixel IC wafer 60 and a driver wafer 70. The manufacturing line 10 not only tests the manufactured microdisplays 50, but also tests the pixel IC wafer 60 and the driver wafer 70, and more specifically enables optical testing of the pixel IC wafer 60.

[0027] The microdisplay 50 can be used, for example, as a Near Eye Display to provide VR (Virtual Reality), AR (Augmented Reality), or MR (Mixed Reality). The microdisplay 50 may be a microOLED display or the like, and in this embodiment, it is a microOLED display.

[0028] The pixel IC wafer 60 has multiple pixel ICs 100 formed on it. In this embodiment, the pixel IC wafer 60 uses a silicon substrate as a backplane for driving. The pixel IC wafer 60 is disc-shaped. The pixel IC wafer 60 is an example of a wafer on which multiple pixel ICs 100 are formed. In Figure 1, 18 pixel ICs 100 are shown on the pixel IC wafer 60 simply for the purpose of clarifying the explanation, but any number of pixel ICs 100 can be formed on the pixel IC wafer 60.

[0029] Figure 3 is a schematic plan view showing an example of a pixel IC 100. Each of the multiple pixel ICs 100 in this embodiment comprises multiple OLEDs (Organic Light Emitting Diodes) 110, a test driver 120, a driver electrode 130, and a package electrode 140. In Figure 3, for the sole purpose of clarifying the explanation, the various components of the multiple OLEDs 110 and other components of the pixel IC 100 are shown in enlarged view, and the dimensional ratios of each component are not limited to those shown in Figure 3. Also, in Figure 3, for the sole purpose of clarifying the explanation, only some of the OLEDs 110 are shown, and the remaining OLEDs 110 are omitted with dotted lines.

[0030] In a plan view, the pixel IC 100 can be divided into three parts: a panel portion 101, a bonding portion 102, and an end portion 103. In Figure 3, these three parts are shown by dashed lines. As shown in Figure 3, the panel portion 101 occupies most of the pixel IC 100, the bonding portion 102, which has a smaller area than the panel portion 101, is adjacent to the panel portion 101, and the end portions 103, which have a smaller area than the panel portion 101, are adjacent to both ends of the panel portion 101 and the bonding portion 102. Note that the arrangement of the three parts shown in Figure 3 for the pixel IC 100 is merely an example, and other arrangements are also possible.

[0031] Multiple OLEDs 110 are formed by depositing onto a silicon substrate of the panel portion 101. After packaging, the multiple OLEDs 110 constitute the pixel array of the panel of the microdisplay 50. OLEDs 110 are light-emitting diodes that use organic materials as light-emitting materials, and can also be called organic ELs. They emit light themselves when an electric current is passed through them. Therefore, OLEDs 110 do not require a backlight. The light-emitting method of the OLEDs 110 may be an RGB method in which three light-emitting elements of RGB (Red, Green, Blue) included as subpixels in each pixel are lit as needed, or a color filter method in which a white light-emitting element expresses color through an RGB color filter. In this embodiment, the color filter method is used.

[0032] The silicon substrate of the panel portion 101 on which the OLED 110 is formed by vapor deposition has, for example, a CMOS (Complementary Metal Oxide Semiconductor) transistor combining n-channel and p-channel transistors, and wiring fabricated on it. Before the vapor deposition of the OLED 110, the cathode electrode 111 of the transistor is exposed at the location where each OLED 110 will be deposited. In Figure 3, the cathode electrode 111 corresponding to each of the illustrated OLEDs 110 is schematically shown by a dashed frame.

[0033] The silicon substrate of the panel section 101 has a pixel circuit, which is a pixel control circuit that controls each pixel. If the packaged microdisplay 50 displays an image with a resolution of 4K, then pixel control circuits for four colors (RGB plus white), i.e., 12K, are arranged on the silicon substrate of the panel section 101, and the pixel control circuits occupy the majority of the silicon substrate of the pixel IC 100.

[0034] The test driver 120 is electrically connected to the multiple OLEDs 110 via a pixel control circuit formed in the panel section 101, and the pixel control circuit drives the multiple OLEDs 110. The test driver 120 is formed in the bonding section 102 around the area where the driver electrode 130 is formed. It can also be said that the test driver 120 is formed in an unused area of ​​the diffusion layer on the silicon substrate of the pixel IC 100 where the multiple OLEDs 110, package electrode 140, and driver electrode 130 are not formed. In Figure 3, the test driver 120 is shown by a thick dashed line on one end of the bonding section 102 as an example. In the bonding section 102, at least the silicon substrate in the area where the test driver 120 is formed has the above-mentioned CMOS transistor and wiring fabricated in it, similar to the panel section 101.

[0035] The test driver 120 displays a test image used for optical testing of the pixel IC wafer 60 on multiple OLEDs 110 using a pixel control circuit. The test image is a dedicated image for the optical test and is a very low-resolution image compared to the image displayed on the microdisplay 50 after packaging. Therefore, the number of transistors in the test driver 120 is extremely small compared to the number of transistors in the aforementioned driver 200 used to display the image on the microdisplay 50.

[0036] The test driver 120 may be made unusable for other purposes after being used for optical testing of the pixel IC wafer 60. Note that the test driver 120 is an example of a test driver that drives multiple OLEDs 110.

[0037] The driver electrode 130 is electrically connected to the multiple OLEDs 110 via a pixel control circuit formed in the panel section 101, thereby electrically connecting the aforementioned driver 200. In other words, the driver electrode 130 is an electrode for electrically connecting the driver 200, which is attached to the pixel IC 100, to the pixel control circuit. Because the driver 200 is attached to the driver electrode 130, it is not exposed to the outside in the microdisplay 50 after packaging. Note that the driver electrode 130 is an example of a driver electrode to which the driver 200 that drives the multiple OLEDs 110 is electrically connected, and is different from the test driver 120.

[0038] Multiple driver electrodes 130 are formed on the silicon substrate of the bonding portion 102. That is, the driver electrodes 130 are formed in a small area at the corner of the pixel IC 100 where no image control circuit is formed. The driver electrodes 130 are formed in the same way as the cathode electrodes 111 of the transistors in the panel portion 101, and are softer and more easily damaged than the package electrodes 140. Therefore, if a probe needle is brought into contact with the driver electrodes 130 for probing, for example, the driver electrodes 130 may be damaged, which could lead to poor connection with the bonded driver 200, resulting in reduced yield and increased costs. For this reason, the driver electrodes 130 are not used for other applications such as power-on testing of the OLED 110.

[0039] The package electrodes 140 are electrically connected to a plurality of OLEDs 110 formed on the panel portion 101. Multiple package electrodes 140 are formed on the silicon substrate at the end 103. The package electrodes 140 can be bonded when packaging the pixel IC 100 and the driver 200. The package electrodes 140 are larger, taller, and more scratch-resistant than the cathode electrodes 111 and the driver electrodes 130. The package electrodes 140 may be used for current-on tests of the OLEDs 110, etc.

[0040] For example, the package electrode 140 is about 5 to 10 μm higher than the cathode electrode 111 and the driver electrode 130. Therefore, when probing multiple package electrodes 140 using multiple probe needles extending uniformly from a probe card, for example, the multiple probe needles will not come into contact with the cathode electrode 111 and the driver electrode 130.

[0041] At least one of the multiple package electrodes 140 is electrically connected to the test driver 120 for optical testing of the pixel IC wafer 60 by the test driver 120. In Figure 3, as an example, the wiring electrically connecting one package electrode 140A and the test driver 120 is schematically shown as a straight line.

[0042] On the driver wafer 70, a plurality of drivers 200 are formed. In the present embodiment, a silicon substrate is used as a backplane for driving, and the above-described CMOS transistors and wirings are formed at least in the region where the drivers 200 are formed. The driver wafer 70 has a disk shape. In FIG. 1, for the purpose of simply clarifying the description, 82 drivers 200 are shown on the driver wafer 70, but an arbitrary number of drivers 200 can be formed on the driver wafer 70.

[0043] When the driver 200 is packaged together with the pixel IC 100, it is electrically connected to a plurality of OLEDs 110 via a driver electrode 130 formed at the bonding portion 102 of the pixel IC 100 and a pixel control circuit formed in the panel portion 101, and drives the plurality of OLEDs 110 by the pixel control circuit. After packaging, the driver 200 causes the pixel control circuit to display an image displayed on the microdisplay 50 after packaging on the plurality of OLEDs 110. That is, the driver 200 after packaging causes the pixel control circuit to display an image having a resolution of 2K or higher on the plurality of OLEDs 110.

[0044] When the resolution becomes as high as 2K or higher, the quality of the image also becomes high, and the number of internal data also becomes extremely large. Just in terms of the number of pixels, when changing from full HD to 4K, for still images, it becomes more than four times, and for moving images, the number of data also increases in the time axis direction, so the amount of data to be handled becomes extremely large. The driver 200 that handles this has to handle an extremely large amount of data among limited data lines, so it is extremely fast. For example, in the case of 4K, the amount of data is four times that of full HD, so a higher transfer rate is required. In order to handle data at high speed, the speed of the transistors has to be high.

[0045] For example, if only making the panel of the microdisplay, a silicon substrate created with design rules such as a minimum pitch of line and space of 90 nm, 120 nm, etc. is used. However, for a high-speed driver, since it uses a silicon substrate created with more stringent design rules such as a minimum pitch of 40 nm, 28 nm, etc., it costs more. In the panel, as described above, the image display part occupies almost the entire area of the silicon, and the space where a driver similar to the driver 200 can be incorporated is extremely small. Nevertheless, if a silicon substrate created with stringent design rules is used as the base for the entire microdisplay only for this driver, the cost will increase significantly. When incorporating the driver into the panel, it is conceivable to optimize the cost of the panel by changing the above-mentioned minimum pitch between the panel and the part of the driver, but it is preferable to separately manufacture the panel and the driver and then bond and package them.

[0046] On the other hand, when separately manufacturing the panel and the driver and then bonding and packaging them, the optical defects of the panel cannot be detected until after packaging. As the panel has a higher resolution, the risk of an increase in the optical defects of the panel increases. If the optical defects of the panel are detected after packaging, neither the packaged driver nor the panel can be used, resulting in a decrease in yield and an increase in cost.

[0047] Therefore, in the present embodiment, without using a silicon substrate created with the above-mentioned stringent design rules for the pixel IC 100, the above-mentioned test driver 120 is incorporated into the unused area of the diffusion layer in the pixel IC 100, so that the optical defects of the pixel IC 100 can be detected by the test driver 120 before the driver 200 and the pixel IC 100 are packaged.

[0048] Compared to the test driver 120, which only displays the test image described above, the driver 200 is designed with stricter line width rules to achieve higher speeds. In other words, the test driver 120 is designed with looser rules than the driver 200. It can also be defined that the test driver 120 is designed with design rules from one or more generations ago than the driver 200. Furthermore, it can be defined that the test driver 120 has a larger pitch for the lines and / or spaces it can form, that is, a wider line and / or space width than the driver 200. The number of transistors in the driver 200 is significantly larger than the number of transistors in the test driver 120. Note that the driver 200 is an example of a separate driver that drives multiple OLEDs 110, distinct from the test driver 120. The driver 200 may also be called a DDIC (Display Driver IC).

[0049] The manufacturing line 10 includes, as an example, a WF (Wafer) testing device 11, a first good product determination device 12, a first cutting device 13, a WF electrical testing device 14, a vapor deposition device 15, a WF optical testing device 16, a second good product determination device 17, a second cutting device 18, an assembly device 21, an MD (Micro Display) electrical testing device 22, an MD optical testing device 23, and a third good product determination device 24. In this example, the WF testing device 11 and the first good product determination device 12 are part of the configuration of the first test determination device D1, that is, the test and determination of the test subject are performed within a single device. Similarly, the WF optical testing device 16 and the second good product determination device 17 are part of the configuration of the second test determination device D2, that is, the test and determination of the test subject are performed within a single device. Similarly, the WF optical testing apparatus 16 and the second good product determination apparatus 17 are part of the configuration of the second test and determination apparatus D2, that is, the test and determination of the test subject are performed within a single apparatus. The MD optical testing apparatus 23 and the third good product determination apparatus 24 are part of the configuration of the third test and determination apparatus D3, that is, the test and determination of the test subject are performed within a single apparatus. Note that these multiple testing apparatuses and determination apparatuses may each be separate devices.

[0050] The multiple devices included in the manufacturing line 10 may be installed in one facility or in multiple facilities. The manufacturing line 10 may also include equipment for manufacturing one or both of the pixel IC wafers 60 and the driver wafers 70. That is, one or both of the pixel IC wafers 60 and the driver wafers 70 may be manufactured in the manufacturing line 10, or they may be manufactured elsewhere and then brought into the manufacturing line 10. Therefore, the manufacturing method for the microdisplay 50 and the testing method for the pixel IC wafers 60 according to this embodiment can also be applied to pixel IC wafers 60 and driver wafers 70 manufactured elsewhere.

[0051] The manufacturing flow shown in Figures 1 and 2 begins, for example, when any transport means, such as a handler, loads the driver wafer 70 into the WF test apparatus 11. The driver wafer 70, driver 200, pixel IC wafer 60, pixel IC 100, and microdisplay 50 shown in Figures 1 and 2 may be transported between the multiple apparatuses shown in Figures 1 and 2 by any transport means.

[0052] In the first test and determination device D1, the WF test device 11 tests the driver wafer 70 (step S101), and the first good product determination device 12 receives the test results from the WF test device 11 and determines whether the driver wafer 70 is a good product (step S103). The WF test device 11 performs a functional test (FT) of the driver wafer 70, for example. The WF test device 11 may perform the FT on all of the multiple drivers 200 of the driver wafer 70 simultaneously, or it may divide them into several groups and perform the FT on all of the multiple drivers 200 in each group simultaneously, and then perform this sequentially for each group. The WF test device 11 may also perform the FT to individually check the operation of the multiple drivers 200 of the driver wafer 70. The first good product determination device 12 may determine whether the driver wafer 70 as a whole is a good or bad product without identifying each of the multiple drivers 200 individually. The first good product determination device 12 may determine a driver wafer 70 as good if the test results meet predetermined conditions. For example, the first good product determination device 12 may determine the driver wafer 70 as a whole to be defective if the number of drivers 200 determined to be defective exceeds a predetermined threshold. The first good product determination device 12 may discontinue the use of a driver wafer 70 that has been determined to be defective.

[0053] The first cutting device 13 cuts out multiple drivers 200 from the driver wafer 70 that was determined to be good in step S103 (step S105). The first cutting device 13 may also separate driver wafers 70 that were determined to be defective in step S103 into multiple drivers 200. In this case, the good drivers 200 cut out from the driver wafer 70 that were determined to be defective in step S103 may be used in the next process. The drivers 200 cut out from the driver wafer 70 may also be called DDIC chips.

[0054] Next, a pixel IC wafer 60 on which multiple pixel ICs 100 are formed is prepared, and an arbitrary transport means loads the pixel IC wafer 60 into the WF electrical test apparatus 14, which then electrically tests the pixel IC wafer 60 (step S107). More specifically, the WF electrical test apparatus 14 probes the package electrode 140 with a probe needle 14A and conducts an electrical test on each of the multiple OLEDs 110 via the package electrode 140. The WF electrical test apparatus 14 in Figure 1 schematically shows the manner of this probing. Step S107 is an example of electrically testing the pixel IC wafer 60 by probing the package electrode 140 contained in each of the multiple pixel ICs 100 before the OLEDs 110 are deposited on the pixel IC wafer 60.

[0055] The electrical test is performed on silicon on which the OLED 110 has not been deposited. In such silicon, the test verifies whether the wiring from one electrode to another conducts as designed, whether one wire is short-circuited with an adjacent wire, etc. In this electrical test, instead of or in addition to probing the package electrode 140 with the probe needle 14A, the cathode electrode 111 exposed in the area where the OLED 110 will be deposited may be probed with the probe needle 14A.

[0056] The deposition apparatus 15 deposits OLEDs 110 onto the panel portion 101 of the pixel IC wafer 60 (step S109). In the second test determination apparatus D2, the WF optical test apparatus 16 optically tests the pixel IC wafer 60 (step S111). More specifically, as described above, the WF optical test apparatus 16 does not probe the driver electrode 130, but probes the package electrode 140 with a probe needle 16A to send an electrical signal for optically testing the pixel IC wafer 60 to the multiple OLEDs 110. The WF optical test apparatus 16 is schematically shown within the frame of the WF optical test apparatus 16 in Figure 1. The WF optical test apparatus 16 drives the multiple OLEDs 110 with a test driver 120 to display a test image on the multiple OLEDs 110.

[0057] The optical test of the pixel IC wafer 60 may, for example, be a test in which the entire panel portion 101 of each pixel IC 100 is illuminated, or it may be a test in which the panel portion 101 of each pixel IC 100 is divided into several regions and illuminated with different gradations in each region. Regarding the latter, for example, optical testing of the pixel IC wafer 60 may include outputting a test image of a monochrome or geometric pattern consisting of at least one of an illuminated state and a non-illuminated state from the test driver 120 to a plurality of OLEDs 110. The test image displayed on the panel portion 101 may be, for example, entirely white, entirely black, several gradations between black and white, black and white stripes, black and white checkerboard patterns, and other geometric patterns. When displaying such a test image, the test driver 120 only needs to control such patterns for each pixel according to certain rules, and does not need to have memory or complex circuits. Note that there are several types of manufacturing methods for the OLEDs 110, and the way defects occur differs depending on the manufacturing method. The circuit for the test driver 120 can be made to match each method of making the OLED 110, or it can be made to be applicable to several methods of making the OLED 110.

[0058] In the second test determination device D2, the second good product determination device 17 receives the test results of the electrical test from the WF electrical test device 14 and the test results of the optical test from the WF optical test device 16, and determines whether each of the multiple pixel ICs 100 is a good product or not based on these test results (step S113). The second good product determination device 17 may determine a pixel IC 100 as a good product if both test results satisfy predetermined conditions. The second good product determination device 17 may also determine a pixel IC 100 as a good product if either one of the test results satisfies predetermined conditions. The second good product determination device 17 may also determine whether the pixel IC wafer 60 as a whole is a good or bad product without identifying each of the multiple pixel ICs 100 individually. For example, the second good product determination device 17 may determine the pixel IC wafer 60 as a whole to be a bad product if the number of pixel ICs 100 determined to be defective is greater than or equal to a predetermined threshold. The second good product determination device 17 may discontinue the use of the pixel IC wafer 60 that it has determined to be defective. Steps S107, S111, and S113 described above are just one example of a method for testing the pixel IC wafer 60.

[0059] The second cutting device 18 cuts out the pixel ICs 100 that were determined to be good in step S113 from the pixel IC wafer 60 (step S115). In step S113, the second cutting device 18 may also cut out the pixel IC wafer 60 into individual pixel ICs 100 if it determines that the pixel IC wafer 60 as a whole is defective. The pixel ICs 100 cut out from the pixel IC wafer 60 may also be called pixel IC chips. Steps S107 to S115 described above may be executed in parallel with steps S101 to S105, or before steps S101 to S105, instead of being executed after steps S101 to S105.

[0060] The assembly apparatus 21 assembles the microdisplay 50 by attaching the driver 200 to the pixel IC 100 which was determined to be a good product in steps S105 and S115 described above, and by electrically connecting the driver 200 to the plurality of OLEDs 110 via the driver electrode 130 (step S117). The assembly apparatus 21 in Figure 2 schematically shows the manner of attachment within its frame, and the direction of attachment is indicated by a dashed arrow. At least after the optical test in step S111, for example, in step S117, the assembly apparatus 21 may ground the package electrode 140A that was used to send electrical signals to the plurality of OLEDs 110 for optical testing of the pixel IC wafer 60. This prevents the packaged test driver 120 from moving. Alternatively, instead of grounding the signal line used for the test driver 120, the test driver 120 may be prevented from moving by making the signal line a power line.

[0061] After the assembly of the microdisplay 50 in step S117, the MD electrical test apparatus 22 electrically tests the microdisplay 50 by probing the package electrode 140 included in the pixel IC 100 with a probe needle 22A (step S119). After the assembly of the microdisplay 50, the MD optical test apparatus 23 in the third test determination apparatus D3 optically tests the microdisplay 50 by driving a plurality of OLEDs 110 with a driver 200 (step S121). Optical testing of the microdisplay 50 may also include probing the package electrode 140 included in the pixel IC 100 with a probe needle 23A and sending an electrical signal for optical testing of the microdisplay 50 to the plurality of OLEDs 110. The respective frames of the MD electrical test apparatus 22 and the MD optical test apparatus 23 in Figure 2 schematically show the manner of probing.

[0062] In the third test determination device D3, the third good product determination device 24 receives the test results of the electrical test from the MD electrical test device 22 and the test results of the optical test from the MD optical test device 23. Based on these test results, it determines whether the microdisplay 50 is a good product or not (step S123), selects the microdisplay 50 that has been determined to be a good product for shipment, and the flow ends. The third good product determination device 24 may also determine that a microdisplay 50 is a good product if both test results satisfy predetermined conditions. The third good product determination device 24 may also determine that a microdisplay 50 is a good product if either one of the test results satisfies predetermined conditions.

[0063] Figure 4 is a schematic plan view showing an example of a microdisplay 50. As described above, the microdisplay 50 comprises a pixel IC 100 and a driver 200. As described above, the pixel IC 100 includes a plurality of OLEDs 110 and a test driver 120. The plurality of OLEDs 110 are formed on the panel portion 101, and the test driver 120 is formed on the bonding portion 102. The pixel IC 100 also includes a plurality of package electrodes 140, as described above, and the plurality of package electrodes 140 are formed on the end portion 103.

[0064] As described above, the test driver 120 is formed to drive a plurality of OLEDs 110 to optically test the wafer 60 for the pixel IC and is not used in the microdisplay 50. In order to restrict the use of the test driver 120 in the microdisplay 50, as an example in this embodiment, as described above, at least one package electrode 140A included in the pixel IC 100 is grounded while being electrically connected to the test driver 120.

[0065] The driver 200 is attached to the pixel IC 100. The driver 200 drives the multiple OLEDs 110 of the pixel IC 100. As mentioned above, the test driver 120 is constructed with looser design rules than the driver 200.

[0066] In the embodiments described above, the pixel IC 100 was described as including a plurality of OLEDs 110 in the panel portion 101. Alternatively, the pixel IC 100 may include a plurality of microLEDs in the panel portion 101. In this case, in the manufacturing flow of Figures 1 and 2, step S109 is a step of transferring microLEDs to the pixel IC wafer 60 instead of a deposition step. More specifically in this step, a wafer on which a plurality of microLEDs are formed on a sapphire substrate is attached to the panel portion 101 of each pixel IC 100 on the pixel IC wafer 60, and then the sapphire substrate is removed, leaving the microLEDs on the panel portion 101. In this case, further, in the optical test of the pixel IC wafer 60, before the microLEDs are transferred to the pixel IC wafer 60, the pixel IC wafer 60 is electrically tested by probing at least one of the package electrodes 140 included in each of the plurality of pixel ICs 100 and the cathode electrodes 111 exposed in the area where the microLEDs will be transferred. In the case of micro-LEDs, the method of generating light differs from that of OLEDs, so the circuit configurations of the test driver 120 and driver 200 may differ from those of OLEDs.

[0067] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above embodiments. It will be clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention.

[0068] It should be noted that the execution order of operations, procedures, steps, and stages in the apparatus, systems, programs, and methods shown in the claims, specifications, and drawings is not explicitly stated as "before," "prior to," etc., and that these processes can be implemented in any order unless the output of a previous process is used in a later process. Even if the manufacturing flow described in the claims, specifications, and drawings uses phrases such as "first," "next," etc., for convenience, this does not mean that it is mandatory to perform the processes in that order.

[0069] 10 Manufacturing Line D1 First Test and Judgment Device 11 WF Test Device 12 First Good Product Judgment Device 13 First Cutting Device 14 WF Electrical Test Device 14A Probe Needle 15 Evaporation Device D2 Second Test and Judgment Device 16 WF Optical Test Device 16A Probe Needle 17 Second Good Product Judgment Device 18 Second Cutting Device 21 Assembly Device 22 MD Electrical Test Device 22A Probe Needle D3 Third Test and Judgment Device 23 MD Optical Test Device 23A Probe Needle 24 Third Good Product Judgment Device 50 Microdisplay 60 Wafer for Pixel IC 70 Wafer for Driver 100 Pixel IC 101 Panel Section 102 Bonded Section 103 Edge 110 OLED 111 Cathode Electrode 120 Test Driver 130 Driver Electrode 140, 140A Package electrode 200 driver

Claims

1. A method for testing a wafer on which multiple pixel ICs are formed, comprising: preparing the wafer, wherein each of the multiple pixel ICs includes: a plurality of LEDs; a test driver for driving the plurality of LEDs; and driver electrodes to which a separate driver, different from the test driver, for driving the plurality of LEDs is electrically connected; and optically testing the wafer by driving the plurality of LEDs with the test driver.

2. The test method according to claim 1, wherein the optical test comprises outputting a test image of a monochromatic or geometric pattern consisting of at least one of an illuminated state and a non-illuminated state from the test driver to the plurality of LEDs.

3. The test method according to claim 1, wherein the optical test includes probing to the package electrodes contained in each of the plurality of pixel ICs, without probing to the electrodes for the driver, and passing an electrical signal to the plurality of LEDs for optically testing the wafer.

4. The test method according to claim 1, wherein the plurality of LEDs are OLEDs, and further comprises probing at least one of the package electrodes included in each of the plurality of pixel ICs and the cathode electrodes exposed in the region where the OLEDs will be deposited onto the wafer, before the OLEDs are deposited onto the wafer, to electrically test the wafer.

5. The test method according to claim 1, wherein the plurality of LEDs are microLEDs, and further comprises probing at least one of the package electrodes included in each of the plurality of pixel ICs and the cathode electrodes exposed in the region where the microLEDs will be transferred, before the microLEDs are transferred to the wafer, to electrically test the wafer.

6. The test method according to claim 4 or 5, further comprising determining whether each of the plurality of pixel ICs is a good product based on the results of the electrical test and the results of the optical test.

7. A method for manufacturing a microdisplay, comprising: preparing a wafer on which a plurality of pixel ICs are formed, wherein each of the plurality of pixel ICs includes: a plurality of LEDs; a test driver for driving the plurality of LEDs; and driver electrodes to which a separate driver, different from the test driver, for driving the plurality of LEDs is electrically connected; optically testing the wafer by driving the plurality of LEDs with the test driver; determining whether each of the plurality of pixel ICs is good or not based on the results of the optical test; cutting out the plurality of pixel ICs from the wafer; and assembling the microdisplay by attaching the separate driver to the pixel ICs determined to be good and electrically connecting the separate driver to the plurality of LEDs via the driver electrodes.

8. The manufacturing method according to claim 7, wherein the optical testing includes probing to the package electrodes contained in each of the plurality of pixel ICs, without probing to the electrodes for the driver, and sending an electrical signal to the plurality of LEDs for optical testing the wafer.

9. The manufacturing method according to claim 8, further comprising, at least after the optical test, grounding the package electrodes used to transmit the electrical signals for optically testing the wafer to the plurality of LEDs.

10. The manufacturing method according to claim 7, wherein the plurality of LEDs are OLEDs, and the manufacturing method further comprises probing at least one of the package electrodes included in each of the plurality of pixel ICs and the cathode electrodes exposed in the region where the OLEDs will be deposited onto the wafer, before the OLEDs are deposited onto the wafer, to electrically test the wafer.

11. The manufacturing method according to claim 7, wherein the plurality of LEDs are microLEDs, and the manufacturing method further comprises probing at least one of the package electrodes included in each of the plurality of pixel ICs and the cathode electrodes exposed in the region where the microLEDs will be transferred, before the microLEDs are transferred to the wafer, to electrically test the wafer.

12. The manufacturing method according to claim 10 or 11, wherein determining whether each of the plurality of pixel ICs is a good product includes determining whether each of the plurality of pixel ICs is a good product based on the results of the electrical test and the results of the optical test.

13. The manufacturing method according to claim 7, further comprising, after the assembly of the microdisplay, driving the plurality of LEDs with the separate driver to optically test the microdisplay.

14. The manufacturing method according to claim 13, wherein optical testing of the microdisplay includes probing into the package electrodes included in the pixel IC and sending an electrical signal for optical testing of the microdisplay to the plurality of LEDs.

15. The manufacturing method according to claim 7, further comprising probing the package electrodes included in the pixel IC after the assembly of the microdisplay.

16. The manufacturing method according to claim 7, wherein the test driver is formed with looser design rules than the separate driver.

17. A microdisplay comprising a pixel IC including a plurality of LEDs and a test driver, and a separate driver attached to the pixel IC, distinct from the test driver, which drives the plurality of LEDs.

18. The microdisplay according to claim 17, wherein the test driver is formed with looser design rules than the separate driver.

19. The microdisplay according to claim 17, wherein the pixel IC includes a package electrode that is grounded while electrically connected to the test driver.

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