CN114122050A - Mass transfer method for microscopic light-emitting diode displays based on fluidic assembly - Google Patents
Mass transfer method for microscopic light-emitting diode displays based on fluidic assemblyDownload PDFInfo
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Abstract
Translated fromChinese
Description
Technical Field
The present disclosure relates to the field of micro-LED displays, and more particularly, to a system and method for transferring a large amount of micro-LEDs during a manufacturing process of a display.
Background
A red-green-blue (RGB) display is composed of a plurality of pixels that emit light at three wavelengths, corresponding to red, green, and blue light in the visible. The RGB portions of these pixels (each portion referred to as a sub-pixel) are energized in a systematic manner to superimpose to produce colors in the visible spectrum. Different displays also differ in the way they generate RGB images. Liquid Crystal Displays (LCDs) are currently the most popular technology, which produce RGB images by illuminating color filters on sub-pixels with a white light source, typically a fluorescent white LED. A part of the wavelength of light included in the white light is absorbed, and the other part of the wavelength of light is transmitted through the color filter. Thus, the efficiency of an LCD display may be below 4% and its contrast is limited by light leaking from the liquid crystal cells (cells). An Organic Light Emitting Diode (OLED) display directly emits Light of a corresponding wavelength by exciting an Organic Light Emitting material in each sub-pixel, thereby generating RGB Light. OLED pixels are directly emissive and thus the contrast of the display is high, but the organic material degrades over time, resulting in image degradation.
A third display technology, to which this application is directed, is a micro light emitting diode display that uses micro (body diameter of 5-150 micrometers (μm)) inorganic LEDs as subpixels and emits light directly. Inorganic micro-led displays have many advantages over other displays, having a contrast ratio in excess of 50,000:1 and higher efficiency than LCD displays. Unlike OLED displays, inorganic LEDs do not suffer from aging and can achieve significantly higher brightness.
The current mainstream High Definition Television (HDTV) resolution standard has two million pixels (or six million sub-pixels), and the 4K and 8K standards with higher resolution are eight million and three thousand three million pixels, respectively. Even the relatively small display screens used in tablet computers and cell phones have millions of pixels, with the resolution of the display screen exceeding six hundred pixels per inch (ppi). Therefore, the manufacture of display panels using micro-leds requires the assembly of large-area micro-led arrays with different pixel pitches at a low cost, so that displays of various sizes and resolutions can be manufactured. The most conventional micro-led array assembly technique is referred to as pick-and-place because each micro-led is individually picked from a carrier and placed on a substrate, as described below. Since each micro light emitting diode is handled separately, the assembly process is very slow.
Fig. 1A-1C depict a cross-sectional view of a Gallium Nitride (GaN) based LED stack (fig. 1A), cross-sectional views of two fully fabricated vertical micro-LEDs (fig. 1B), and cross-sectional views of a surface mount micro-LED (fig. 1C) (prior art). The high brightness GaN-based LEDs that have been widely used for general illumination have created a complex manufacturing system, and thus the application of micro-LEDs to displays is based on the existing investment in the industry. GaN-based LEDs emitting blue (about 440 nanometers (nm)) wavelengths are fabricated in a complex series of high temperature Metal Organic Chemical Vapor Deposition (MOCVD) steps to produce the vertical LED structure shown in cross-section in fig. 1A. The fabrication process is performed on polished sapphire, silicon or silicon carbide (SiC) substrates having a diameter of 50-200 millimeters (mm). The surface is prepared by depositing undoped GaN and selectively depositing an aluminum nitride (AlN) buffer layer, resulting in a lattice surface with low defects and GaN lattice constant. Since the thickness and temperature of the initial deposition needs to be adjusted to compensate for the lattice mismatch between the substrate and GaN, i.e., the thickness is increased to improve the surface quality, the thickness of the high efficiency device is higher than about 3 μm. Since the MOCVD deposition process is complex and expensive, it is important to optimize the micro-led process to utilize the entire area of the growing wafer most efficiently.
After preliminary growth to form a crystalline GaN surface, a first LED layer is grown by adding silicon doping to form n + GaN for the cathode. Optionally, the stack may comprise layers tuned for electron injection and hole blocking. Next, a layer of indium gallium nitride (In) is depositedxGa1-xN) and GaN alternating layers, wherein the indium content and the thickness of said layers determine the emission wavelength of the device. Increasing the indium content shifts the emission peak to longer wavelengths, but also increases the stress due to lattice mismatch, so that high efficiency GaN devices cannot be made for red emission, and green LEDs are less efficient than blue LEDs. After forming the MQW, the stacked structure may further include layers tailored for electron blocking and hole injection. The MOCVD layer sequence was completed by depositing magnesium (Mg) doped GaN to form a p + anode layer.
LEDs used for general illumination (up to 3-4mm per side) are much larger than micro LEDs (5-150 μm in diameter) used in micro LED displays, and thus the requirements for patterning and electrodes are significantly different. Micro LEDs require bonding to substrate electrodes with solder material or non-symmetric Conductive Film (ACF), while large size LEDs are typically wire bonded or solder paste bonded to lead frames. Since the micro-leds are very small, most of the area on the MOCVD wafer is removed during the patterning process, thereby reducing the available light emitting area per wafer. LED wafers are relatively expensive and the high resolution required to fabricate micro-LEDs further increases costs, and it is therefore important to use the light-emitting area as efficiently as possible to minimize the material costs of the micro-LED display.
In the simplest process flow, by depositing a thin (few nanometers) nickel oxide (NiO)X) To match the p + GaN work function and deposit a layer of Indium Tin Oxide (ITO) with a thickness of 50-300nm to form a transparent conductive electrode on the MOCVD stack. The deposited stack is then patterned and etched, typically using chlorine (Cl) based etching2) Particularly when producing micro-LEDs with high efficiency, the thickness of the LED structure is only 3-5 μm, thus limiting the minimum space that can be successfully etched.
After etching the outline of the LED, additional processing is performed to form electrodes on the anode, as schematically shown in fig. 1C. To prevent electrical leakage and to etch the openings for connecting the ITO layer, a passivation layer is typically provided, which is typically Plasma-enhanced Chemical Vapor Deposition (PECVD) Silicon Dioxide (SiO Dioxide)2) Or alternatively, includes thin Atomic Deposition (ALD) Aluminum Oxide (Al) disposed on the surface2O3) And (3) a layer. The anode structure is completed by depositing an electrode stack structure comprising a material such as indium/tin (In/Sn) or gold, germanium (Au/Ge) alloy.
Fig. 2A depicts the process of removing micro-leds from a sapphire substrate using Laser Lift Off (LLO). Fig. 2B depicts a pick-and-place process in which devices from a carrier wafer are to be moved and placed onto a display substrate. Figure 2C depicts the connection of the micro-led anode to the substrate electrode (prior art). Specifically, in fig. 2A, the fabricated micro-leds are bonded to a carrier wafer by an adhesive layer and simultaneously removed from the sapphire substrate by laser lift-off. In fig. 2B, a micro-led may be removed from the carrier by a pick-up head and placed on a sub-pixel with its anode electrically connected to a corresponding electrode on the substrate. The pixels are completed by coating the micro-leds with a suitable dielectric, such as a lithographically patternable polyimide, while connecting the cathodes of the micro-leds to the electrodes on the substrate. Metal interconnects are deposited and patterned to form connections as shown in fig. 2C.
LEDs emitting red light with a wavelength of about 630nm are typically made of aluminum gallium indium phosphide (AlGaInP) grown on gallium arsenide (GaAs), and since GaAs is opaque, it is not possible to strip the LED from a GaAs substrate using laser lift-off technology. Thus, if it is desired to strip the red LED from the substrate, the substrate may be etched completely, or a selective etch (typically using hydrogen chloride (HCl): acetic acid) may be used to undercut and strip the LED. The size (cross section) of the LED is similar to that of a GaN general illumination LED (the size is 150-. In the patent: AlGaInP LED processes are more fully described in US10,804,426, which is incorporated herein by reference.
The pick-and-place assembly process described above presents several significant problems that result in higher cost and lower throughput. In particular, the assembly process is serial in nature, and therefore, it takes a long time and is costly to assemble millions of micro-leds. The small size of the micro-leds themselves makes the grasping head difficult to fabricate, and the edges of the grasping instrument are likely to interfere with adjacent micro-leds during grasping or with reflector structures between pixels during assembly. The single pick-and-place approach described above can be extended to a parallel process by using a massive transfer head to simultaneously pick and transfer multiple micro-leds. However, the quality of this bulk transfer method may be poor because there are defective elements in a group of micro-leds that are transferred at the same time, and the pitch between each micro-led is determined by the pitch of the elements grown on the wafer.
FIGS. 3A-3H depict an example of a bulk transfer method (prior art). The mass transfer method is to transfer a plurality of micro light emitting diodes arranged in an array as a whole onto a display substrate, and has been widely developed to solve the problem of low throughput of serial pick-and-place assembly. In the simplest mass transfer process, a rectangular stamping stamp picks up a rectangular array of micro-leds from a carrier and presses the micro-leds against a display substrate, bonding each micro-led to a respective electrode. Since manufacturing RGB displays requires consideration of micro-leds of different colors, the transfer stamp is arranged to pick up every third micro-led, thereby leaving room for micro-leds of the other two sub-pixel colors. For the surface mount micro led shown in fig. 2C, the assembly process proceeds as follows:
1) separate MOCVD wafers are prepared for each color of micro-leds, with appropriate size and spacing between each micro-led. The spacing between adjacent micro-leds is referred to as pitch. Please refer to fig. 3A. Each micro-led has a cathode and an anode for connection to a display substrate. The micro-led array is removed from the growth wafer by laser lift-off and held on a carrier substrate (not shown).
2) The display substrate (fig. 3B) is provided with a plurality of sets of cathode electrodes and anode electrodes, and the distance between each set of electrodes is several times of the distance between each micro-led on the wafer, so that the positions of the electrodes and the micro-leds on the transfer stamp are matched with each other. This spacing determines the ultimate resolution of the display. The electrodes may be copper, indium tin oxide/aluminum (ITO/Al), gold, or a solder such as tin/indium (Sn/In). An ACF film may also be used to cover the electrodes. By determining the materials of the electrodes and the micro light emitting diodes on the display panel, ohmic contacts can be formed through a subsequent bonding process in step 5 described below.
3) Preparing an imprint stamp based on the position of the pickup point matching the sub-pixel pitch on the display. Current pick-up mechanisms applied to mount each micro-led include elastomers, adhesive tape, static electricity and magnetic fields. Fig. 3C depicts an imprint stamp of 3 x 3 pixels in size, but in practice an imprint stamp will typically fit hundreds of pixels.
4) Referring to fig. 3D, the stamp is placed in alignment with the carrier substrate carrying the micro-leds of the first color and the stamp is brought into contact with the carrier substrate so that the securing structure can grasp the plurality of micro-leds and remove them from the carrier substrate.
5) Referring to FIG. 3E, the filled imprint stamp is placed in alignment with the electrodes on the first set of display substrates.
6) Referring to fig. 3F, the stamp is pressed against and contacts the display substrate, and is typically heated to form a bonding structure between the micro light emitting diode electrodes and the electrodes on the display substrate. After the bond is formed and cooled sufficiently to secure the micro light emitting diodes, the embossed seal is removed for reuse.
7) The same operations are performed for the micro-leds of the second and third colors, respectively, as shown in fig. 3G-3H, thereby forming an RGB display array.
The mass transfer method described above is feasible and has been applied to the manufacture of displays, but there are still some problems resulting in low product yield and high product cost. First, in fig. 3B, the pitch of the display in the x-direction and the y-direction can only be an integer multiple of the pitch between the micro leds on the MOCVD wafer, which is illustrated as 3 × 2. A well-established display manufacturing technology must be able to produce screens of different sizes, such as 4K (3840 × 2160 pixels), that meet industry standards, and therefore a technology (pitch spreading) is needed that can change the pitch of the micro-leds on the stamp. The size of the micro-leds on the MOCVD wafer can also be customized for each display with respect to size and resolution, but this adds unnecessary cost. Secondly, the pick-up device must be balanced in the magnitude of the bonding strength, and if the bonding strength is too low, some of the micro-leds will not detach from the carrier substrate, leaving gaps in the array. On the contrary, if the connection strength is too high, the micro light emitting diode is also forcibly removed after being soldered on the substrate. In both cases, the brightness of the sub-pixels is reduced, which cannot be tolerated in a display. Finally, the structure of the transfer stamp is complex and difficult to manufacture. The connection points must be smaller than the pitch between the micro-leds to avoid interference of the stamp with adjacent micro-leds. This is difficult for complex fixation methods that require the generation of local fields (e.g. electrostatic or magnetic forces). Imprint stamps are also susceptible to contamination and damage, especially those made of elastomers such as Polydimethylsiloxane (PDMS), and it is therefore important to effectively clean the stamp for repeated use.
To illustrate the drawbacks of the high volume transfer imprint process, FIG. 3H depicts several possible failure scenarios:
and a fault a: lack of micro light emitting diodes due to poor adhesion of the stamp upon picking up;
and b, fault b: the micro light-emitting diode is misplaced due to the pollution on the stamping seal;
and c, fault: particles due to contamination of the transfer stamp;
and d, fault: a broken micro light emitting diode;
and e, fault: short-circuiting of the micro-leds due to defects of the MOCVD process:
and f, fault: the micro light emitting diode is forcibly removed by the stamp to cause the damage of the electrode.
Fig. 4A and 4B depict exemplary area coverage using a 14mm stamp (fig. 4A) for stamp picking on a 100mm wafer. Wherein 20% of the micro-leds are eventually retained on the wafer, there are three imprint stamps with defective micro-leds. Another limitation of the mass transfer process described above is the square shape of the stamp, which does not match the round wafers used to produce LEDs in MOCVD. Figure 4A shows a typical arrangement when using a 14 x 14mm stamp on a 100mm wafer. The use of large area imprinting stamps increases the speed of assembly at the expense of leaving more micro-leds on the growth wafer. Because of the requirement to fill all imprint stamps, a larger area on the wafer cannot be used with imprint stamps. In the above example, the discarded quality-qualified micro-leds account for approximately 20% of the total, which directly increases the cost. In addition, for defective micro-leds, the affected stamping stamp must be repaired or discarded. The above example describes three random defects for illustrative purposes only, and if a defective stamp is discarded in this example, only about 70% of the original micro-leds can be used for display manufacturing.
The bulk transfer method has a significant advantage in that the binding process is performed under pressure applied to the micro-leds, so that there is good mechanical contact between the two bonding electrodes. This ensures a large area of contact between the electrodes. Mechanical contact also destroys the insulating oxides on the surface, improving the wettability of the solder material. ACF bonding also requires pressure to make the conductive fill material into hard contact with the micro light emitting diodes and electrodes on the display substrate.
It would be advantageous to have a structure and method that would fill the bulk transfer of assembled carrier substrates for micro-led displays and that would improve assembly flexibility and yield in the following manner:
1. any display resolution can be realized through simple space expansion;
2. a series of micro light emitting diodes (known to be good chips) can be manufactured without device defects such as missing, damage or short circuits;
3. the assembly speed of huge transfer can be improved by filling and transferring the stamping seal by a large-scale parallel transfer method;
4. the simple transfer stamping stamp is used, has lower manufacturing cost and can be reused by strong cleaning;
5. a simple imprinting mechanism which does not damage the display substrate can be adopted;
6. excess micro-leds can be recovered from defective stamping stamps.
Disclosure of Invention
The present application provides a method of fabricating a micro-led array by fluid assembly on a carrier substrate or transfer stamp and related structures. The assembled micro-leds can be applied to a display substrate and bound by a mass transfer method. Micro-leds are fabricated on a wafer by conventional MOCVD methods, with shapes selected to facilitate fluid assembly and imprinting onto a display substrate.
Accordingly, the present application provides a micro led bulk transfer imprinting system comprising an imprinting stamp substrate having a top surface. The top surface is formed with impression stamp substrate trapping positions arranged in an array, and each trapping position is provided with a columnar groove for temporarily fixing a keel extending from the bottom surface of the micro light-emitting diode. When the micro light emitting diode is a surface mount type, it has a planar top surface including a first electrode and a second electrode. When the micro-led is vertical, it has a planar top surface with a first electrode, and the keel is a conductive second electrode. The imprinting system further comprises a fluid assembly carrier substrate having an array of wells formed on a planar top surface of the carrier substrate, the array of wells having a pitch separating adjacent wells matching a pitch separating adjacent trapping sites on the imprinting stamp substrate.
An associated micro led bulk transfer method comprises: providing the fluid assembly carrier substrate with the trap array and providing the stamping stamp substrate, wherein each trapping position in the array is provided with a columnar groove matched with the trap on the carrier substrate. The method uses a fluid assembly process such that micro light emitting diodes are filled into wells of the carrier substrate. The method comprises pressing the top surface of the stamp base plate against the top surface of the carrier substrate with each of said capture locations corresponding to a respective well, thereby transferring the micro light-emitting diodes from the carrier substrate to the stamp base plate. The grooves of each capture location carry keels extending from the bottom surface of the micro light emitting diode and the micro light emitting diodes are secured to the stamp substrate by constraining the keels. The use of a carrier substrate eliminates the limitations imposed by the spacing between micro-leds on an MOCVD wafer, allowing the application of various stamped stamp substrate spacings in different display substrate sizes and resolutions.
The method also provides a display substrate having an array of micro-led bond pads, wherein each micro-led bond pad includes at least one electrode formed on a top surface thereof, the electrode being electrically connected to an underlying matrix of column and row control lines. The connection pads have a spacing separating adjacent locations that matches a spacing separating adjacent capture locations in the imprint stamp substrate. The method presses a top surface of an imprint stamp substrate against a top surface of a display substrate, each capture location is connected to a corresponding micro-light emitting diode location, and transfers a plurality of micro-light emitting diodes from the imprint stamp substrate to a plurality of connection pads of the display substrate. In one aspect, the step of transferring the micro light emitting diodes onto the connection pads of the display substrate includes heating the display substrate to bind the plurality of micro light emitting diodes to the plurality of connection pads. In the case of RGB display, the method may sequentially press-fit the stamp substrate having the first wavelength micro light-emitting diode, the second wavelength micro light-emitting diode, and the third wavelength micro light-emitting diode disposed at the capture position, or a single stamp substrate corresponding to one wavelength micro light-emitting diode.
The present application further provides a micro Light Emitting Diode (LED) bulk transfer method that employs assembling an imprint stamp substrate with a fluid having a planar top surface with a plurality of capture locations formed thereon having a first perimeter shape, a depth, and a planar bottom surface. The capture site may be filled by a fluid assembly process with a micro-light emitting diode having a first perimeter shape, the micro-light emitting diode having a thickness greater than the depth of the capture site, a bottom surface in contact with the bottom surface of the capture site, a planar top surface and a first electrode extending beyond the capture site, and a securing mechanism. In one aspect, the securing mechanism is a keel formed on a top surface of the micro light emitting diode, the keel being either a conductive keel connected to the first electrode or a temporary non-conductive keel that is removed after the micro light emitting diode is secured to the stamp substrate. In another aspect, the fixing mechanism is a first component comprising a pair of conjugated biomolecules disposed on the bottom surface of each micro light emitting diode. In this case, the bottom surface of each capture site is provided with a second component comprising a pair of conjugated biomolecules.
As described above, the method provides a display substrate having a planar top surface and an array of micro LED bond pads, each including a first electrode formed on the top surface in electrical communication with a matrix of column and row control lines underlying its substrate. The distance between the wells adjacent to the display substrate is matched with the distance between the capture positions adjacent to the stamp substrate. The method imprints the top surface of the stamp substrate against the top surface of the display substrate, fills each capture location with a micro-light emitting diode, and transfers the plurality of micro-light emitting diodes from the imprinted stamp substrate to the micro-light emitting diode connection pads of the display substrate. Also, during the transfer process, the display substrate may be heated, thereby facilitating electrode bonding.
The application also provides a huge transfer method of the axial micro light-emitting diode. The method provides a fluid assembly stamp substrate having a planar top surface with a plurality of capture sites formed thereon, the capture sites having a first perimeter shape, a central portion having a planar first depth, a distal end having a planar second depth (the second depth being less than the first depth), and a proximal end having a planar second depth. The method comprises filling the axial micro-leds into trapping locations by a fluid assembly process, each micro-led occupying a respective trapping location having the first perimeter shape, a body connected to the central portion, and a vertical planar body having a thickness greater than the first depth but less than twice the first depth. A distal electrode horizontally bisects the body and is in contact with the distal end of the capture site, the distal electrode having a vertical plane with an electrode thickness greater than the second depth of the capture site but less than twice the second depth. A proximal electrode having the same thickness as the distal electrode, horizontally bisecting the body and in contact with the proximal end of the capture site.
The method provides a display substrate having a planar top surface and an array of micro-led bonding pads, each micro-led bonding pad comprising a pair of electrodes formed on the top surface and electrically connected to a matrix of column and row control lines therebelow. The display substrate has a spacing separating adjacent wells that matches a spacing separating adjacent capture locations on the imprint stamp substrate. The method presses the top surface of the stamp substrate against the top surface of the display substrate, contacts each capture location with a corresponding micro-light emitting diode, and transfers the micro-light emitting diodes from the stamp substrate to the display substrate, typically with the application of heat to promote bonding of the electrodes.
The above-described system and method will be described in detail below.
Drawings
Fig. 1A-1C are cross-sectional views of a GaN-based LED (fig. 1A), two vertical micro-LEDs (fig. 1B), and one surface mount micro-LED (fig. 1C) (prior art).
Fig. 2A is a process of removing a micro light emitting diode from a sapphire growth substrate using a laser lift-off technique (prior art).
Fig. 2B illustrates a pick-and-place process (prior art) for moving and positioning a device from a carrier wafer onto a display substrate.
Fig. 2C shows a process of connecting the anode of the micro light emitting diode to the substrate electrode (prior art).
Fig. 3A-3H are steps of an exemplary bulk transfer process (prior art).
Fig. 4A-4B are examples of coverage areas for imprint pickup on a 100mm wafer using a 14mm imprint stamp (fig. 4A), with 20% micro leds left on the wafer and three micro leds on the imprint stamp with defects (fig. 4B) (prior art).
Fig. 5 is a partial cross-sectional view showing a typical backplane arrangement of surface mount micro light-emitting diodes and power transistors controlling the brightness of the micro light-emitting diodes.
Fig. 6A-6B are top and cross-sectional views, respectively, of a surface mount micro-led for fluid assembly.
Fig. 7 is a schematic diagram of a micro led wafer after selective picking.
Fig. 8 is a short depiction of the fluidic effect that allows 100% of the micro-leds to be assembled with the electrodes facing down in the correct orientation.
FIGS. 9A-9D illustrate steps in a macro transfer imprint system using micro-LEDs.
Fig. 10A-10D are cross-sectional views of a process for transferring micro-leds from a carrier substrate to a display substrate.
FIGS. 11A-11D are schematic views of an imprint system in which the micro-LEDs are vertical micro-LEDs.
Fig. 12A-12B are partial cross-sectional views of an attraction force generator for assisting in securing micro-leds to capture locations of a carrier substrate.
FIGS. 13A-13K are schematic diagrams of a micro-LED bulk transfer imprinting system using fluid assembly to imprint a stamp substrate.
Fig. 14A and 14B are schematic views of the use of an electrostatic force generator and a magnetic force generator as an auxiliary device to assist in securing a micro-led to a fluid assembly trapping site, respectively.
FIGS. 15A-15I are schematic diagrams of a micro-LED bulk transfer system using fluid embossing and axial micro-LEDs.
FIG. 16 is a flow chart of a micro-LED bulk transfer method corresponding to the system shown in FIGS. 9A-9D.
FIG. 17 is a flow chart of the micro LED bulk transfer method for assembling an imprint stamp substrate using a fluid shown in FIGS. 13A-13K.
Fig. 18 is a flow chart of the axial (lead) micro led bulk transfer method shown in fig. 15A-15I.
FIG. 19 is a flow chart of a method for expanding the transmission time interval of a micro light emitting diode.
Description of the main elements
Stampingstamps
Micro light emitting diodebottom surface 908
Microlight emitting diode 910
Surface mount microlight emitting diodes
Micro light emitting diodetop surface 912
Carriersubstrate top surface 1002
Carriersubstrate bottom surface 1008
Vertical microlight emitting diode 1100
Vertical micro light emittingdiode top surface 1102
Vertical micro-ledfirst electrode 1104
Insulatinglayer 1106
Depth 1306
Catchsite bottom surface 1308
Micro light emittingdiode thickness 1310
Micro light emittingdiode bottom surface 1312
Micro light emittingdiode top surface 1314
Grooves 1320
Thiol Biotin bifunctional molecule/first component 1322
ACF 1325
Streptavidin molecule/first component 1327
Afirst depth 1508
Axial microlight emitting diode 1516
Dielectric thin film 1530
The following detailed description will further illustrate the present application in conjunction with the above-described figures.
Detailed Description
The general process of fabricating micro-LED displays using inorganic LEDs and fluid assembly on a display backplane has been reported in U.S. patents 9,825,202 and 10,418,527, which are incorporated herein by reference. In particular, U.S. 9,825,202 describes a process flow for manufacturing a suitable display backplane starting from column 13 and row 26, as shown in fig. 17. The electrical requirements of which are described in unpublished patent application 16/727,186, which is also incorporated herein by reference. The display substrate used here has the same row and column arrangement and Thin Film Transistor (TFT) circuitry as described in fig. 14B and 14C of patent 9,825,202, but without the well layers, since the bulk transfer stamp locates the micro-leds.
Fig. 5 is a partial cross-sectional view showing a typical backplane arrangement of surface mount micro light-emitting diodes and power transistors controlling the brightness of the micro light-emitting diodes.
The fluid assembly techniques proposed in U.S. patents 9,825,202, 10,418,527, and 10,543,486 (incorporated herein by reference) are suitable for direct random assembly of low-cost micro-led display fabrication. The same assembly technique is used to prepare an imprint stamp for the purpose of alternately binding the micro-leds to the electrodes of the display substrate. The advantage of this approach over the direct fluid assembly strategy is that ohmic contact between the micro-leds and the display is facilitated by the use of an imprint stamp and the application of pressure during the binding process. As used herein, transfer stamp is arranged to have an array of capture positions, with the pitch between capture positions matching the pitch between display pixels. The stamp may be made of glass, quartz or monocrystalline silicon, and the trapping sites (also referred to as wells) may be made by etching the stamp or disposing a layer of film, such as patterned polyimide, over the stamp, and patterning the wells using photolithographic techniques. The capture site is the same shape as the micro-leds and may be slightly larger than that shown in figure 8 of united states patent 10,804,426, which is hereby incorporated by reference. The system described herein is unique in that the depth of the capture location may be less than at least one point of the micro-led thickness, so that the micro-led may contact the assembly tool or display substrate without interference from the top surface of the stamp. The wells etched into the stamp (capture sites) may be more robust and thus may be more thoroughly cleaned, but control of the depth of the capture sites may become more difficult. In contrast, the depth of the trap sites formed on the polyimide or a deposited film can be controlled by the thickness of the film, but are more susceptible to damage.
The imprinting system described herein is compatible with a variety of configurations of micro-LEDs, but the conventional LED structure shown in fig. 2C is not suitable because it lacks a means for positioning during fluid assembly, and thus the electrodes cannot be properly positioned on the display substrate for bonding. The disc-shaped surface mount micro-leds described in us10,804,426 were designed as a range of solutions constrained in the fluidic assembly described in us 9,825,202, as shown in 12 columns 56 and fig. 16, and therefore these devices were used to describe the imprint system described in this application. It should be understood that other micro-led shapes, such as square, rectangular and triangular shaped devices, such as fig. 8 of us 9,825,202 and fig. 4 of us10,516,084 (incorporated herein by reference), may be used in the same manner. Likewise, the imprint system is not limited to surface mount micro-leds. Vertical micro-leds can also use this method, using a single bottom electrode, and fabricated after assembly to make the top electrode. Such variations will be readily apparent to those skilled in the art and, in the interest of brevity, will not be described in any great detail herein.
Fig. 6A and 6B depict a top view and a cross-sectional view, respectively, of a surface mount micro-led for fluid assembly. The device is typically constructed with a diameter of 20-100 microns (mum), a thickness of 4-6 μm, and includes a keel having a height of 5-10 μm. In this case the well depth is typically 3.5-4.5 μm to accommodate the thickness of the micro-leds. The detailed manufacturing process flow can be seen in line 56 of column 8 of U.S. patent 10/804,426 and in fig. 6. The shape of the disk matches the cylindrical shape of the capture site, which is typically less deep than the thickness of the micro-leds and slightly larger in diameter than the micro-leds. The surface mount electrodes are usually made of tin/indium or gold/germanium solder, and the bonding surfaces of the P-connection pad and the N-connection pad must be on the same plane for contact.
Fig. 7 depicts the micro led wafer after selective picking. Defects were identified by light microscopy, Scanning Electron Microscopy (SEM) images, cathodoluminescence or photoluminescence. The aim is to identify all defects which may cause errors in the display pixels, so that the defective product can be removed from the suspension of micro-leds used for manufacturing. Combining the defect map with known patterns, such as edge bead maps and alignment structures, all known locations of the micro-leds with defects can be obtained. Using a printing process, the micro-leds with defects are covered with a capture material to avoid their being picked up. As shown, the selective pick-up stamping stamp process will take all the acceptable micro-leds and leave the micro-leds with defects. Combining high utilization with prevention of mixing in of defective devices is a significant advantage of fluid assembly techniques. The selective pick-up method is described in greater detail in unpublished application No.16,875,994, which is incorporated herein by reference.
After the micro light emitting diode is manufactured, the growth wafer is attached to a carrier wafer through an adhesive layer, the micro light emitting diode is peeled off from the sapphire wafer through a laser lift-off (LLO) technology, and keels are patterned on the bottom surface of the micro light emitting diode.
The micro-leds suspension was dispersed on a carrier substrate and assembled as described in figure 7 of us10,418,527 and us10,804,426. For the mass transfer method, it is important to avoid surface contaminants from interfering with the exposed surface of the micro-leds and the surface of the target site. Therefore, any extra micro-leds that are not assembled on the surface are removed and recycled after assembly, so that an efficient cleaning method is also important.
Fig. 8 provides a simple overview of the fluidic effect that enables 100% micro-leds to be assembled with the correct orientation with the electrodes facing down. The assembled substrate is inspected and if some wells are not filled or other defects such as excess unassembled micro-leds are present, the stamp is simply rinsed with solvent to remove the micro-leds and the solvent is captured in a reservoir to recover the micro-leds. The empty stamp would be further washed, dried and inspected to ensure that there is no surface contamination or residue at the capture location. This ability is important for conventional stamp stamps that use elastomers or adhesive glues to hold the micro-leds because they are difficult to clean and reuse. In the conventional technology, the stamping stamp with the contaminated or missing micro light emitting diode is usually discarded, so that the intact micro light emitting diode on the stamping stamp cannot be recycled.
FIGS. 9A-9D illustrate steps in the use of a micro-LED macro-transfer imprinting system. The system includes animprint stamp substrate 900 having atop surface 902. An array of stampsubstrate capture locations 904 is formed ontop surface 902. Eachcapture location 904 is configured as a cylindrical recess to temporarily secure akeel 906 extending from abottom surface 908 of a micro-led 910. As shown, the microlight emitting diodes 910 are surface mount micro light emitting diodes, each microlight emitting diode 910 includes a planartop surface 912, and afirst electrode 914 and asecond electrode 916 are disposed on thetop surface 912. In this case, thekeel 906 is not conductive. In this particular example, the second electrode is a full or partial ring around the first electrode, as shown in fig. 6A. For the systems of FIGS. 9A-9D or 11A-11D (see below), the micro-LEDs may be attached to a capture location by patterning the stamp substratetop surface 902 with an adhesive glue or elastomer.
The filledcarrier substrate 1000 is the basis for a bulk transfer to thedisplay substrate 918 using thestamp substrate 900, illustrated as a single micro-led. Although not explicitly shown, it is obvious that the electrode connection pads of the display substrate are connected to a network of rows and columns to operate the micro-leds, for details see the U.S. patent 9,825,202. In this case, thecarrier substrate 1000 is a planar surface substrate with wells, and local protrusions (optionally adhesive glue or elastomer) near the imprint stamphead capture locations 904 can be brought into contact with each micro-led (as shown in fig. 9B). Since the micro-leds are usually held in the carrier by gravity alone, the relatively weak adhesion forces cause the micro-leds to be removed from the carrier during the transfer process by means of an optional adhesive glue or elastomer. The imprint stamp is aligned with and pressed against the electrodes on the display substrate, such that a hard contact is formed between the electrodes of the micro light emitting diode and the electrodes on the display substrate, and a solder bond is formed by heating (fig. 9C). In another embodiment, the connection may be made by an additional ACF film (not shown). When the binding is complete, the transfer stamp is recovered and detached from the micro light emitting diode (fig. 9D). Thetransfer head 900 andcarrier substrate 1000 may be cleaned for reuse and cycled to fill the entire area of thedisplay substrate 918.
Fig. 10A-10D are cross-sectional views illustrating a process of transferring a micro light emitting diode from a carrier substrate to a display substrate. The system includes fluidassembly carrier substrates 1000a-1000c having a planartop surface 1002 andwells 1004 arrayed on the carriersubstrate top surface 1002 with aspacing 1006 between adjacent wells, thespacing 1006 matching the spacing separating adjacent capture sites on the stamp substrate. The well 1004 of the carrier substrate has a first perimeter shape (circular in this embodiment) and aplanar well floor 1008. The surface mount microlight emitting diodes 910a-910c each have a first perimeter shape and a planartop surface 912 to contact thewell floor 1008 through afirst electrode 914 and a second electrode 916 (as shown in figure 9A).
In the case of an RGB display, the imprint system may further include a first fluidset carrier substrate 1000a, and an array of wells disposed on the top surface of the carrier substrate, with aspacing 1006 between adjacent wells to match the capture locations of the imprint stamp substrate (fig. 10B). The microlight emitting diodes 910a are configured to emit light at a first wavelength, each occupying a respective well in thefirst carrier substrate 1000 a. Similarly, second fluidset carrier substrate 1000b includes an array of wells disposed on the top surface of the carrier substrate with aspacing 1006 between adjacent wells to match the capture locations of the stamp substrate. The microlight emitting diodes 910b are configured to emit light at a second wavelength, each occupying a respective well in thesecond carrier substrate 1000 b. The third fluidassembly carrier substrate 1000c includes an array of wells disposed on the top surface of the carrier substrate with aspacing 1006 between adjacent wells to match the capture locations of the stamp substrate. The microlight emitting diodes 910c are configured to emit light at a third wavelength, each occupying a respective well in thethird carrier substrate 1000 c.
In order to manufacture the three colors required for the RGB display, the three-color micro light emitting diodes need to be sequentially subjected to assembly and imprinting operations, as shown in fig. 10A to 10D. The three carrier substrate capture location array designs will be spaced according to thepitch 1006 of the display pixels. The process flow of the micro-LEDs of different colors or the performance gap of the LEDs may be large, which may determine that the micro-LEDs of different colors have different sizes and/or shapes. For example, the red micro-leds may be made of aluminum indium gallium phosphide (AlInGaP), as described in U.S. patent 10,804,426, in which case the red micro-leds may be thicker than the GaN-based blue and green devices. Since blue and green micro-leds have different quantum efficiencies and the human visual system is more sensitive to green, it may be desirable to fabricate blue and green micro-leds with different emission regions. An example of these differences is shown in fig. 10A, where each carrier substrate is tailored to meet the requirements of a micro-led of a corresponding color. The stamp substrate 900a captures the blue micro-leds 910a in an array from the carrier substrate and moves onto thedisplay substrate 918, aligning the stamp 900a with the vacant areas on the display substrate and bringing the electrodes of the micro-leds into physical contact with the matching electrodes on the display substrate (fig. 10B). The pressure andheating device 1010 is used to enhance the intimate contact between the electrodes, thereby melting the metallic material and forming a solder bond. In fig. 10C and 10D, green microlight emitting diodes 910b and red micro light emitting diodes 910C are transferred and bound in the same manner (stamp 900b, stamp 900C). The bonding between the micro-leds and the bonding pads may use materials such as au/ge to cu, in/zn to cu, and au/ACF/cu. If ACF is used, the material of the display electrode can be chosen more widely, such as Mo/Al/Mo.
The fluid assembly used in the present application achieves several improvements over the simple stamping process of the prior art:
1) no gaps in the array pattern due to defects or lack of micro-leds;
2) selective pick-up and fluid assembly make full use of all intact micro-leds on one wafer;
3) the micro light-emitting diode is recycled in the assembling process and on the defective carrier substrate, so that waste can be prevented;
4) the carrier substrate is manufactured according to the distance of the capture locations on the display, and the pitch spreading can be done simply.
Fig. 11A-11D depict an imprinting system in which the micro-leds are vertical micro-leds, each vertical micro-led 1100 having a planartop surface 1102 with afirst electrode 1104 and aconductive runner 906 as a second electrode. As with the surface mount micro-leds, thecarrier substrate well 1004 has a first perimeter shape (e.g., circular) and aplanar well floor 1008. Each vertical microlight emitting diode 1100 has a first perimeter-shaped and planartop surface 1102, thetop surface 1102 being in contact with acorresponding well floor 1008 via afirst electrode 1104.
For smaller micro leds, there is not enough space to fabricate two electrodes on the same surface as a surface mount micro led, and the same assembly process can be applied to vertical micro leds. In this case, the micro-leds are configured with a single anode electrode on the top surface and a cathode electrode on the bottom surface as a conductive post (keel) or with gold or copper plating on the bottom surface. The conductive posts may also act as keels when fluidly assembled on a carrier plate (substrate).
The assembly and binding sequence of the conductive keel vertical micro light emitting diode is shown. A micro light emitting diode suspension was prepared by the above selective acquisition method, dispensed onto the surface of a carrier substrate provided with wells having a display pitch, and then assembled according to a conventional procedure. The stamp is aligned with the carrier substrate and the micro-leds are removed from the carrier substrate as shown in fig. 11A. The filled imprint stamp is aligned with the display substrate and a mechanical contact is made between the cathode electrode on the micro light emitting diode and the P-pad electrode on the display substrate by applying pressure (as shown in fig. 11B). Aheating device 1010 is used to form the solder bonds and then the stamp is removed and cleaned and reused. An insulatinglayer 1106, such as polyimide, is used to fill the gap between the micro-leds and the reflective wells to prevent shorting and planarize the surface for metal deposition (fig. 11C). The keels protrude from the insulatinglayer 1106 and form self-aligned contacts to each micro-led through the short O2Plasma etching to remove a portion of the insulating layer may improve the contact effect. The conductive pillars of the micro light emitting diodes are connected to Vss (power supply) by patterned metal as shown in fig. 11D to form a circuit.
12A and 12B are partial cross-sectional views of a force generator for assisting in securing a micro light emitting diode to a capture location of a carrier substrate. In which FIG. 12A shows anelectrostatic force generator 1200 and FIG. 12B shows amagnetic force generator 1202. Although surface mount micro leds are illustrated, the force generator described above may also be applied to vertical micro leds.
FIGS. 13A-13K depict steps of a micro light emitting diode bulk transfer imprint system using fluid assembly to imprint a stamp substrate. To further simplify the assembly process, the imprint stamps may be filled directly using fluidic assembly, thereby omitting the carrier substrate. The micro-leds shown in fig. 6 use a keel structure on the bottom surface, hereinafter referred to as a securing mechanism, to secure the micro-leds to the electrodes of the fluid assembly collection site. For the direct assembly process, the electrode position must be "up" in the stamp, so the keel structure is fabricated on the top surface of the micro-led, as shown in fig. 13A. Fluid assembly is performed in a conventional manner, with the micro-leds assembled in an array in the capture position with the keel structure and electrodes facing up. The material used to make the keel structure is typically a photosensitive polyimide that can be removed with a solvent or etched using an oxygen plasma. After assembly and drying, the keels are removed (as shown in fig. 13B) to facilitate bonding of the electrodes to the display substrate. The stamp is made in the same way as in the previous embodiment, but the well structure must not be affected by the removal of the keels, and therefore an organic film cannot be used, a preferred solution being to etch directly on the substrate to form the trapping site structure. The imprint stamp may contain micro-leds under the influence of gravity and van der waals forces, and if the imprint stamp is inverted, the micro-leds may fall out of the imprint stamp. It is therefore necessary to transfer the assembly and bonding with the surface of the stamp facing upwards and to press the display substrate down on the stamp upon heating (fig. 13C).
The fluidassembly stamp substrate 1300 has a planartop surface 1302. Formed on the imprint stampsubstrate top surface 1302 are an array ofcapture sites 1304, each having a first perimeter shape, a depth 1306, and a planar capturesite bottom surface 1308. As with the previous embodiment, the first perimeter shape is circular, but the system is not limited to this shape. The micro-leds 910 are disposed in thecapture sites 1304 and have a first perimeter shape, athickness 1310 that is greater than the depth 1306 of the capture sites, aplanar bottom surface 1312 that contacts thebottom surface 1308, a planartop surface 1314 that has afirst electrode 1316 and extends beyond the capture sites, and a protection mechanism (explained below). The micro-leds have the same electrical connection relationship as the vertical micro-leds 1100, the vertical micro-leds 1100 have the second electrode formed on the bottom surface 1312 (as shown in fig. 13D) or the same electrical connection relationship as a surface mount micro-led 910, and the surface mount micro-led 910 has thefirst electrode 1316 and thesecond electrode 1324 formed on the surface 1314 (see fig. 13A and 13E).
As shown in fig. 13A, the securing mechanism is akeel 906 formed on the top surface of the micro-leds, thekeel 906 being a temporary non-conductive keel, thekeel 906 being removed before the micro-leds are in contact with the display substrate 1315. Alternatively, as shown in fig. 13D and 13E, the securing mechanism may be aconductive keel 906 connected to afirst electrode 1316. in fig. 13D, the micro light emitting diode is a vertical microlight emitting diode 1100.
In another embodiment, instead of using a non-conductive keel, a conductive center post is used in a direct stamp transfer process, and the structure can be used as both a keel in a fluid assembly process and an anode electrode (fig. 13E). In this case, the stamp is a simple plate with an array of capture positions, the capture position pitch being the same as the display pixel pitch. In the display substrate 1318, the P-pad electrode is located below the N-pad electrode, leaving a space for the conductive post forming the anode electrode on the micro led (fig. 13F). Due to process variation, the difference between the height of the conductive post and the depth of the P-pad groove may occur, so the ACF1325 may be disposed to connect the micro light emitting diode and the display substrate, thereby compensating for the difference.
Thus, the micro light emitting diode in fig. 13E is a surface mount microlight emitting diode 910a, while the display substrate 1318 in fig. 13F includes a recess 1320 for receiving theconductive runner 906.
Another mechanism for positioning and fixing the micro-leds in the transfer stamp is to use a preferential link between conjugated biomolecule pairs (e.g., streptavidin-biotin pairs). After the LLO, a functionalized micro-led is fabricated by depositing a thinsilicon dioxide film 1326 on the back side of thedevice 1312, as shown in fig. 13. The surface of the micro light emitting diode is exposed to hydrogen ions or a basic compound and then silanized by interaction with an amine-terminated molecule such as 3-aminopropyltrimethoxysilane (3-aminopropyl-trimethoxysilane). The surface is washed with streptavidin solution, binding thestreptavidin molecules 1327 to the amine ends, thereby forming streptavidin-functionalized micro-leds (as shown in fig. 13H). Prior to assembly, the capture sites on the transfer stamp can be similarly treated with biotin-terminated ligands, or the well floor can be a gold surface and exposed to thiol biotinbifunctional molecules 1322, as shown in fig. 13I.
Thus, FIGS. 13G-13K depict a micro-LED using conjugated biomolecule pairs as the "immobilization mechanism". Wherein thebottom surface 1308 of the stamp substrate is coated with afirst component 1322 comprising a conjugated biomolecule pair. The micro-led mounting structure is asecond component 1327 comprising conjugated biomolecule pairs coated on thebottom surface 1312 of each micro-led. During assembly, a relatively low depth of capture sites (about 1 μm) can make it easier to remove the misoriented micro-leds by fluid perturbation, while the correctly oriented micro-leds can be chemically bound to the bottom surface of the capture sites and by being bound to a better mark in the capture site. In fig. 13J, the bio-conjugate is shown in an extremely enlarged Z scale (Z scale) to illustrate the binding effect. In fact, the binding layer is very thin, and the presentation in fig. 13K is more accurate. Alternative exemplary chemical pairings of biotin-streptavidin systems, such as thiol-maleimide and azide-alkyne, may be advantageous in terms of stability and ease of processing, but the order of preparation is similar.
Fig. 14A and 14B depict the use of anelectrostatic force generator 1400 and the use of amagnetic force generator 1402 as an assist mechanism to assist in securing the micro-leds in a fluid assembly trapping location (with or without a keel), respectively. In fig. 14A and 14B, the primary securing mechanism may be gravity. In addition, in FIG. 14A, the immobilization mechanism is a conjugated biomolecule (not shown). In other embodiments (not shown), the force generator in FIG. 14A can also be a magnetic force generator, and the force generator in FIG. 14B can also be an electrostatic force generator. Although FIGS. 14A and 14B illustrate only a fluid-assembled stamp substrate, it should be understood that the force generator may also be used with stamp substrates having the groove configuration of FIGS. 9B-9D and 11A-11B.
At the expense of added complexity, some securing structure may be added to the stamp structure to prevent the micro-leds from becoming dislodged from the capture location when the stamp is inverted. The use of an adhesive for bonding is not attractive since the securing mechanism can be removed from the micro-leds after bonding. By providing the porous layer between the substrate bearing surface and the trapping site formation layer, vacuum conditions are introduced into the imprint system, but the liquid of the fluid assembly may flow into the porous layer, resulting in failure of the drying work. The most practical structure for fixing the micro light emitting diode in the stamp is a magnetic or electrostatic force structure. For electrostatic force immobilization, the micro-leds have a dielectric film deposited on a surface corresponding to the surface mount electrode (i.e., the bottom surface), and the imprint stamp includes a power electrode below the capture site structure. For magnetic attachment, the micro-led electrode structure may comprise a magnetic material, such as nickel, with permanent magnets or electromagnets on the stamp.
These fixing mechanisms are switchable at individual points in the array, so that the defective stamping stamp can be repaired using the following procedure:
1) checking the stamping seal to find the micro light-emitting diode with the defect;
2) starting the fixing mechanism for all the good micro light-emitting diodes;
3) removing the defective micro light-emitting diode by washing;
4) additional micro-led suspensions were placed and assembled.
In one aspect, the stamp may include a light sensor that, when pressed onto the display substrate, activates all capture locations (simultaneously or sequentially) that are temporarily electrically connected to the micro light emitting diodes on the stamp. The stamp and associated drive circuitry are connected to a system for recording which micro leds are intact. The fixture on the stamp was activated to hold the intact micro-leds in the capture position and assembly continued until all of the micro-leds were tested intact as shown in flows 2) -4) above. And then performing a binding process.
FIGS. 15A-15I depict a micro-LED bulk transfer imprinting system that uses fluid imprinting stamp substrates and axial micro-LEDs. The bulk transfer method of mixed fluid assembly can also be applied to the axial micro-light emitting diode described in application No.16/846,493. In order to reduce cost and increase density (density), the micro-leds are configured as vertical devices with a light emitting area of 5 × 8 μm, as shown in fig. 15G. The leaf-shaped micro-led electrodes may be plated copper or gold. The dimensions of all of the above features are adjustable, but their relative shapes are important to facilitate assembly of the fluids into a directional array.
Fig. 15A-15C illustrate a process for making an axialmicro-led display substrate 1525.Electrode 1528 is deposited and patterned from a conductive material, such as molybdenum/copper (Mo/Cu), forming connection pads for receiving the cathode and anode of the micro-leds. A dielectric film 1530, which may be silicon dioxide, silicon nitride (Si), is deposited over the electrode3N4) Or polyimide, and patterned and etched out of the dielectric film 1530Contact openings, as shown in fig. 15B. Using the metal electrodes as a hard mask, abody recess 1532 is etched to accommodate the micro light emitting diode body, as shown in fig. 15B. Finally, the N-connection pad 1536 and the P-connection pad 1534 are formed by electroplating, sputtering or evaporation, as shown in FIG. 15C.
For the shape of the axial micro light emitting diode, the manufacturing process of the stamping stamp is more complicated, and two trapping positions with different depths are required. As shown in fig. 15D, afirst recess 1538 is etched in the substrate, thefirst recess 1538 having a depth and profile for accommodating a micro light emitting diode body protruding below the axial electrode surface. In fig. 15E, asecond recess 1504 is formed by etching for receiving an axial electrode. The second recess may also be made of a thin film material (e.g., a photolithographic polyimide) after thefirst recess 1538 is formed.
A well-known axial micro-led suspension is applied to the stamp and assembled into a micro-led array (as shown in fig. 15F). The assembled embossed seal is inspected, matched with the display substrate and pressed together to bind the electrodes of the LED with the electrodes on the display substrate (as shown in fig. 15I). After binding is complete, the stamp is withdrawn, cleaned and inspected for reuse.
Thus, the system includes a fluid-assembledstamp substrate 1500 having a planartop surface 1502.Arrayed capture locations 1504 formed in the stampsubstrate top surface 1502 include: a first perimeter shape (substantially rectangular), acentral portion 1506 having a planarfirst depth 1508, adistal end 1510 having a planarsecond depth 1512, thesecond depth 1512 being less than thefirst depth 1508, and aproximal end 1514 having a planarsecond depth 1512.
Referring to fig. 15F and 15G, an axial micro-led 1516 occupies thecorresponding capture site 1504 and has the first perimeter shape, with thebody 1518 in contact with thecentral portion 1506 of the capture site, and a verticalplanar portion thickness 1520 greater than the capture sitefirst depth 1508 but less than twice the capture sitefirst depth 1508. Adistal electrode 1522 horizontally bisects thebody 1518 and contacts the capture sitedistal end 1510. Thedistal electrode 1522 has a vertically orientedelectrode thickness 1524 that is greater than the capture sitesecond depth 1512 but less than twice the capture sitesecond depth 1512. Aproximal electrode 1526 horizontally bisects thebody 1518 and is in contact with the capture siteproximal end 1514, theproximal electrode 1526 having anelectrode thickness 1524.
As shown in fig. 15I, the process of transferring the micro-leds to the display substrate is similar to the process described in fig. 13C, and the aligned display substrate is pressed down onto the fluid assembly stamp substrate, bringing the electrodes of the micro-leds into contact with the electrodes on the corresponding display substrate. The transfer and binding is accomplished by heating the solder while applying pressure. Alternatively, an ACF film (not shown) may be interposed between the respective electrodes to achieve electrical and mechanical connection without metal phase transition.
Although not specifically shown, the stamp substrate of the present embodiment may include an electrostatic force or a magnetic force generator as shown in fig. 14A and 14B.
FIG. 16 is a flow chart illustrating a micro LED bulk transfer method corresponding to the system shown in FIGS. 9A-9D. Although the method is described as including a series of numbered steps for ease of understanding, the numbering does not necessarily indicate the order of the steps. It should be understood that some steps may be skipped, performed at the same time, or performed without the requirement of a strict order of sequence. However, the method may generally be performed in a numerical order of steps. The method starts atstep 1600.
In one aspect, constraining the keel instep 1604 includes constraining a surface mounted LED having a non-conductive keel that includes a planar surface having a first electrode and a second electrode.Step 1604, on the other hand, circumscribes a conductive keel and is connected to the second electrode, the vertical LED comprising a planar surface with the first electrode (i.e., the keel is the second electrode).
In one aspect,step 1602 provides an imprint stamp substrate having spaced capture locations.Step 1601a provides a fluid assembly carrier substrate having a planar top surface and a plurality of wells arranged in an array on the top surface of the carrier substrate, with a spacing between adjacent wells matching a spacing between capture locations on the stamp substrate. Instep 1601b, the micro light emitting diodes are filled into wells of a carrier substrate by a fluid assembly process. In one aspect,step 1601b may use electrostatic or magnetic forces to secure the micro light emitting diodes into the wells.Step 1603b presses the top surface of the imprint stamp substrate against the top surface of the carrier substrate with each capture location in contact with a respective well, and step 1603c transfers the micro light emitting diodes from the carrier substrate bulk onto the imprint stamp substrate.
Specifically,step 1601a may provide a carrier substrate having a plurality of wells including a first perimeter shape and a planar well floor. Then, instep 1601b, a micro light emitting diode is filled into each well, wherein the surface mount micro light emitting diode filled into the well has a first perimeter shape, a planar top surface in contact with the well bottom surface, which includes a first electrode and a second electrode. In other embodiments, the vertical micro-leds filled into the wells instep 1601b have a first perimeter shape, a planar top surface in contact with the bottom surface of the wells, which includes a first electrode.
In the case of an RGB display, the carrier substrate provided instep 1601a comprises:
a first fluid assembly carrier substrate comprising an array of wells disposed on a top surface of the carrier substrate, a distance between adjacent wells matching a spacing of adjacent capture locations on the imprint stamp base;
a second fluid assembly carrier substrate comprising an array of wells disposed on a top surface of the carrier substrate, a distance between adjacent wells matching a spacing of adjacent capture locations on the imprint stamp substrate;
a third fluid assembly carrier substrate comprising an array of wells disposed on a top surface of the carrier substrate, a distance between adjacent wells matching a spacing of adjacent capture locations on the imprint stamp base plate. Then, the process of filling the wells of the carrier substrate instep 1601b includes:
filling a well on a first carrier substrate with a first micro light emitting diode configured to emit light at a first wavelength;
filling wells on a second carrier substrate with a second micro light emitting diode configured to emit light at a second wavelength; and
wells on a third carrier substrate configured to emit light at a third wavelength are filled with a third micro light emitting diode. Transferring the micro-leds from the carrier substrate to the stamp substrate in step 1603c includes transferring the micro-leds from the first, second, and third carrier substrates to the corresponding stamp substrate. As shown in fig. 10A and 10B, for RGB micro light emitting diodes having different shapes, it is necessary to use carrier substrates of different sizes. In addition, if the diameters of the RGB micro-leds are equal, one carrier substrate may be used to fill the micro-leds with different wavelengths, and then transferred to the imprint stamp substrate.
In the case of RGB display, the display substrate instep 1608 includes a plurality of connection pads for the first micro light emitting diodes for emitting light of the first wavelength; a plurality of connection pads for a second micro light emitting diode for emitting light of a second wavelength; and a plurality of connection pads for a third micro light emitting diode for emitting light of a third wavelength. Thereafter, the process of pressing the top surface of the stamp substrate to the top surface of the display substrate instep 1610 includes pressing the stamp substrate filled with the first micro light emitting diode, the second micro light emitting diode, and the third micro light emitting diode, respectively. One stamp substrate may be used for each wavelength of micro-leds, or if all micro-leds are similar in shape, the same substrate may be used to fill in and transfer micro-leds of different wavelengths to the display substrate.
FIG. 17 is a flow chart of a method for micro LED bulk transfer using a fluid assembly stamp substrate as shown in FIGS. 13A-13K. The method starts atstep 1700.Step 1702 provides a fluid assembly imprint stamp substrate having a planar top surface with capture locations disposed thereon having a first perimeter shape, a depth, and a planar capture location bottom surface. In the fluid assembly process, the micro light emitting diode filled into the trapping site instep 1704 has: a first perimeter shape, a thickness greater than the depth of the capture site, a planar bottom surface in contact with the bottom surface of the capture site, and a top surface having a plane of the first electrode extending beyond the capture site. The micro light-emitting diode also comprises a fixing mechanism. The capture sites may be filled 1704 with micro-leds having a second electrode on the bottom surface or surface mount micro-leds having a first electrode and a second electrode on the top surface.
In one aspect, providing the imprint stamp substrate instep 1702 includes providing an imprint stamp substrate having spaced apart capture positions.Step 1706 provides a display substrate having a planar bottom surface and an array of micro-led connection pads, each micro-led connection pad including a first electrode formed on the top surface and electrically connected to an underlying matrix of column and row control lines. The spacing between adjacent bond pad locations on the display substrate matches the spacing between adjacent capture locations on the imprint stamp substrate. Instep 1708, the top surface of the stamp substrate is pressed onto the top surface of the display substrate such that each capture location contacts a micro led pad. Instep 1710, the micro led bulk on the stamp substrate is transferred to the micro led bonding pads of the display substrate.Step 1710 may include applying a heating process to cause the micro light emitting diodes to be bonded to the bonding pads of the display substrate.
In one aspect,step 1704 provides for forming a securing mechanism in the form of a keel on the top surface of the micro-led, the keel being either a conductive keel connected to the first electrode (as in fig. 13D and 13E) or a temporary (removable) non-conductive keel (as in fig. 13A). On the other hand,step 1702 provides an imprint stamp substrate having a bottom surface of each capture location coated with a first composition comprising a conjugated biomolecule pair. The immobilization mechanism referred to instep 1704 is then a second component having a conjugated biomolecule pair that coats the bottom surface of each micro-led. Examples of conjugated biomolecule pairs include biotin-streptavidin, thiol-maleimide, and azide-alkyne. The stamp substrate may be further provided with an electrostatic force or magnetic force generator as shown in fig. 14A and 14B.
FIG. 18 is a flow chart of an axial micro-LED bulk transfer method for the system shown in FIGS. 15A-15I. The method starts atstep 1800.Step 1802 provides a fluid assembly imprint stamp substrate having a planar top surface with a plurality of capture locations formed thereon, each capture location having a first perimeter shape, a central portion having a planar first depth, a distal end having a planar second depth less than the first depth, and a proximal end having a second depth. Under the fluid assembly process,step 1804 fills the capture locations with axial micro-leds, each micro-led occupying a respective capture location and having the first perimeter shape and a body portion conforming to the central portion, the body portion having a vertical body thickness greater than the first depth of the capture location but less than twice the first depth. The micro-led also has a distal electrode that is horizontally bisecting the body portion, the distal electrode engaging the distal portion of the capture site, the distal electrode having an electrode thickness in a vertical plane that is greater than the second depth of the capture site but less than twice the second depth. The micro-led also has a proximal electrode that horizontally bisects the body portion, is attached to the proximal portion of the capture site, and has an electrode thickness. In one aspect, the stamp electrode may further include an electrostatic force or a magnetic force generator, as shown in fig. 14A and 14B.
In one aspect, providing the imprint stamp substrate instep 1802 includes providing an imprint stamp substrate having spaced apart capture locations.Step 1806 provides a display substrate having a planar top surface and an array of micro light emitting diode connection pads, each including a first electrode and a second electrode formed on the top surface, the plurality of electrodes being electrically connected to an underlying matrix of column and row control lines. The display substrate includes a plurality of connection pads separated by a spacing that matches a spacing that separates capture locations on the imprint stamp substrate. Atstep 1808, the top surface of the stamp substrate is pressed onto the top surface of the display substrate such that each capture location is aligned with a micro LED connection pad. Instep 1810, the micro light emitting diodes are substantially transferred from the stamp substrate to the micro light emitting diode connection pads of the display substrate. Alternatively, bonding between the micro light emitting diodes and the display substrate connection pad electrodes may be facilitated by heating.
FIG. 19 is a flow chart of a pitch spreading method for micro LED transfer. The method begins atstep 1900.Step 1902 provides a micro-led MOCVD wafer having a first pitch between adjacent micro-leds.Step 1904 releases the micro-leds into the fluid assembly suspension.Step 1906 provides a carrier substrate having wells arranged in an array with a second pitch between adjacent wells, the second pitch being different from the first pitch. The micro light emitting diodes are filled into the wells of the carrier substrate instep 1908 by a fluid assembly process.Step 1910 provides an imprint stamp substrate including an array of capture locations, adjacent capture locations being spaced apart by a second spacing. Atstep 1912, the top surface of the stamp substrate is pressed against the top surface of the carrier substrate such that each capture location is in contact with a respective well. Atstep 1914, the micro-leds are bulk transferred from the carrier substrate to the stamp substrate.
In one aspect, steps 1906, 1908, 1912, and 1914 are bypassed and the micro-leds are filled directly into the capture locations of the imprint stamp substrate by anadditional step 1911, i.e., using a fluid assembly process.
Systems and methods for micro led bulk transfer are provided. Examples of specific LED, carrier substrate and stamp substrate configurations are given to illustrate the present application. However, the present application is not limited to the above examples. Other variations and embodiments of the present application will occur to those skilled in the art.
Claims (38)
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| CN202310739434.2ACN116632125A (en) | 2020-11-23 | 2021-10-29 | Fluid-Assembled Carrier Substrate System for Mass Transfer of Micro-LEDs |
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| US17/101,016US11894350B2 (en) | 2014-10-31 | 2020-11-23 | Fluidic assembly enabled mass transfer for microLED displays |
| US17/101016 | 2020-11-23 |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI866482B (en)* | 2022-11-25 | 2024-12-11 | 南韓商樂金顯示科技股份有限公司 | Light-emitting device, display apparatus including the same and method for manufacturing the same |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20240021588A1 (en)* | 2022-07-13 | 2024-01-18 | Kookmin University Industry Academy Cooperation Foundation | Ultra-thin fin led electrode assembly, manufacturing method thereof and light source comprising the same |
| TWI800448B (en)* | 2022-08-23 | 2023-04-21 | 創新服務股份有限公司 | Mass transfer method and device for magnetic electronic components |
| TWI817771B (en)* | 2022-10-14 | 2023-10-01 | 友達光電股份有限公司 | Display device |
| CN118156398B (en)* | 2024-05-10 | 2024-07-12 | 汕头超声显示器技术有限公司 | A method for manufacturing an LED array device |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109148352A (en)* | 2018-08-02 | 2019-01-04 | 上海天马微电子有限公司 | Transfer head array, transfer head and method for transferring inorganic light emitting diode |
| US20190319015A1 (en)* | 2014-10-31 | 2019-10-17 | eLux Inc. | Emissive Display Substrate for Surface Mount Micro-LED Fluidic Assembly |
| KR20200030514A (en)* | 2020-03-02 | 2020-03-20 | 엘지전자 주식회사 | A substrate for manufacturing display device and a manufacturing method using the same |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8860635B2 (en) | 2005-04-04 | 2014-10-14 | The Invention Science Fund I, Llc | Self assembling display with substrate |
| US7874474B2 (en) | 2008-01-22 | 2011-01-25 | University Of Washington | Self-assembly of elements using microfluidic traps |
| US9773750B2 (en) | 2012-02-09 | 2017-09-26 | Apple Inc. | Method of transferring and bonding an array of micro devices |
| US11251166B2 (en) | 2014-10-31 | 2022-02-15 | eLux, Inc. | Fluidic assembly emissive display using axial light emitting diodes (LEDs) |
| US9892944B2 (en)* | 2016-06-23 | 2018-02-13 | Sharp Kabushiki Kaisha | Diodes offering asymmetric stability during fluidic assembly |
| KR101754528B1 (en)* | 2016-03-23 | 2017-07-06 | 한국광기술원 | Transfer assembly with dry adhesion structure and method for transferring led structure assembly using the same and led structure assembly |
| CN107833954B (en)* | 2016-09-15 | 2020-01-24 | 伊乐视有限公司 | Displays with Surface Mount Light Emitting Elements |
| KR102102818B1 (en)* | 2017-08-10 | 2020-05-29 | 고려대학교산학협력단 | Light emitting devices and Substrates and Alignment method and Apparatus thereof |
| KR102646798B1 (en)* | 2018-10-16 | 2024-03-13 | 주식회사 루멘스 | Method for arraying micro LED chips for manufacturing a LED display and a multi-chip carrier |
| US11152328B2 (en)* | 2018-12-13 | 2021-10-19 | eLux, Inc. | System and method for uniform pressure gang bonding |
| CN111033737B (en)* | 2019-03-25 | 2024-02-06 | 湖北三安光电有限公司 | Microluminescent component, microluminescent diode and microluminescent diode transfer method |
- 2021
- 2021-10-29CNCN202111275465.4Apatent/CN114122050A/enactivePending
- 2021-10-29CNCN202310739434.2Apatent/CN116632125A/enactivePending
- 2021-11-11TWTW110142091Apatent/TWI805070B/enactive
- 2021-11-23KRKR1020210161850Apatent/KR102687841B1/enactiveActive
- 2023
- 2023-06-26KRKR1020230081554Apatent/KR20230104098A9/ennot_activeCeased
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20190319015A1 (en)* | 2014-10-31 | 2019-10-17 | eLux Inc. | Emissive Display Substrate for Surface Mount Micro-LED Fluidic Assembly |
| CN109148352A (en)* | 2018-08-02 | 2019-01-04 | 上海天马微电子有限公司 | Transfer head array, transfer head and method for transferring inorganic light emitting diode |
| KR20200030514A (en)* | 2020-03-02 | 2020-03-20 | 엘지전자 주식회사 | A substrate for manufacturing display device and a manufacturing method using the same |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI866482B (en)* | 2022-11-25 | 2024-12-11 | 南韓商樂金顯示科技股份有限公司 | Light-emitting device, display apparatus including the same and method for manufacturing the same |
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| TWI805070B (en) | 2023-06-11 |
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| TW202335140A (en) | 2023-09-01 |
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| KR20220072777A (en) | 2022-06-02 |
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| CN116632125A (en) | 2023-08-22 |
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