Patent Grant
12236825
The present invention relates generally to pixel arrangements in flat-panel color displays, for example active-matrix micro-LED displays.
Flat-panel color displays comprise an array of pixels arranged in rows and columns over a display substrate. Each pixel in the array of pixels comprises one or more light emitters. In color displays, the pixels typically comprise three color light emitters: a red-light emitter, a green-light emitter, and a blue-light emitter. Each pixel in an active-matrix display includes a local control-and-storage circuit that receives data from a display controller (often comprising a row controller that provides row-control signals to each row of pixels and a column controller) that provides column-data signals to each column of pixels). Once the pixel data is stored in each pixel, the pixel controller controls the light emitter(s) in the pixel to output the pixel data independently of other pixels. In contrast, passive-matrix displays do not include a local control-and-storage circuit. Instead, rows of pixels are controlled at a time to emit light by external row and column controllers.
Conventional liquid crystal displays (LCDs) use a backlight to generate light that is controlled by liquid crystal. Organic light-emitting diode (OLED) displays comprise thin layers of organic material to emit light in response to a current passing through the organic material layers. An example of such an active-matrix OLED display device is disclosed in U.S. Pat. No. 5,550,066. In both LCD and OLED displays, the pixels are made as large as possible to increase brightness and lifetime for the displays. Displays using inorganic light-emitting diodes (ILEDs) are also known.
Typical flat-panel displays use thin-film electronic semiconductor materials (such as amorphous or polycrystalline silicon layers) coated on a display substrate to provide active-matrix control circuits for each pixel. The substrate and thin layer of semiconductor material can be photolithographically processed to define electronically active components, such as thin-film transistors. Transistors may also be formed in thin layers of organic materials. In these devices, the display substrate is often made of glass, for example Corning Eagle or Jade glass designed for display applications.
Another method for providing an array of control circuits on a substrate is described in U.S. Pat. No. 7,943,491. In an exemplary embodiment of this approach, small integrated circuits are formed on a semiconductor wafer. The small integrated circuits, or chiplets, are released from the wafer by etching a layer formed beneath the circuits. A PDMS stamp is pressed against the wafer and the process side of the chiplets is adhered to the stamp. The chiplets are pressed against a destination substrate or backplane and adhered to the destination substrate. In another example, U.S. Pat. No. 8,722,458 entitled Optical Systems Fabricated by Printing-Based Assembly teaches transferring light-emitting, light-sensing, or light-collecting semiconductor elements from a wafer substrate to a destination substrate or backplane.
In some cases, however, not all of the elements are transferred from the wafer to the destination substrate by the stamp, for example due to process or material abnormalities or undesired particles on the stamp, the wafer, or the destination substrate. It is also possible that the elements themselves are defective due to materials or manufacturing process errors in the source wafer. Such problems can reduce manufacturing yields, increase product costs, and necessitate expensive repair or rework operations.
There is a need, therefore, for matrix-addressed systems with small high-resolution elements and circuits that are tolerant of manufacturing and materials variability and particle contamination and enable repair.
In one aspect, the present invention is directed to a redundant pixel layout for a display comprises a display substrate and an array of pixels disposed on or over the display substrate. Each pixel comprises a first subpixel and a redundant second subpixel. Each first subpixel comprises a first subpixel controller electrically connected to controller wires and a first light emitter electrically connected to a first-light-emitter wire. Each first light emitter is controlled by the first subpixel controller at least through the first-light-emitter wire. The second subpixel comprises a second-subpixel-controller location comprising electrical connections to the controller wires and a second-light-emitter location comprising a second-light-emitter wire. The first light emitter is adjacent to the second-light-emitter location and the first light emitter and the second-light-emitter location are closer together than are any two pixels in the array of pixels.
In some embodiments of the present invention, for at least one pixel in the array of pixels, the second subpixel of the pixel comprises a second subpixel controller electrically connected to the controller wires in the second-subpixel-controller location and a second light emitter electrically connected to the second-light-emitter wire in the second-light-emitter location. The second light emitter is controlled by the second subpixel controller at least through the second-light-emitter wire.
In some embodiments of the present invention, for the at least one pixel, the first subpixel controller has an area that is greater than an area of the first light emitter or the second subpixel controller has an area that is greater than an area of the second light emitter, or both.
In some embodiments of the present invention, for the at least one pixel, the first subpixel is faulty. In some embodiments of the present invention, for the at least one pixel, the second subpixel is faulty. In some embodiments of the present invention, for the at least one pixel, a controller wire, the first-light-emitter wire, the second-light-emitter wire, a power wire, or a ground wire in a pixel is cut. In some embodiments, the cut wire is in a faulty subpixel.
In embodiments of the present invention, for the at least one pixel, the first subpixel of each pixel comprises two or more first light emitters that each emit light of a different color from others of the first light emitters and the second subpixel of the at least one pixel comprises two or more second light emitters that each emit light of a different color from others of the second light emitters.
In embodiments of the present invention, for the at least one pixel, the first light emitters of the pixel are adjacent and the second light emitters are adjacent, the first light emitters and the second light emitters are disposed in a common line, the first light emitters are disposed in a first line and the second light emitters are disposed in a second line different from the first line, the first light emitters are adjacent to the second light emitters, or the first light emitters are interdigitated with the second light emitters in a line.
In some embodiments of the present invention, for the at least one pixel, the first subpixel comprises a red first light emitter that emits red light, a green first light emitter that emits green light, and a blue first light emitter that emits blue light, and the second subpixel comprises a red second light emitter that emits red light, a green second light emitter that emits green light, and a blue second light emitter that emits blue light. In some configurations, the red first light emitter is adjacent to the blue second light emitter, the green first light emitter is adjacent to the green second light emitter, and the blue first light emitter is adjacent to the red second light emitter. In some configurations, the red first light emitter is adjacent to the red second light emitter, the green first light emitter is adjacent to the green second light emitter, and the blue first light emitter is adjacent to the blue second light emitter.
In some embodiments of the present invention, for the at least one pixel, the first light emitters are between the first subpixel controller and the second light emitters and the second light emitters are between the second subpixel controller and the first light emitters.
In some embodiments, for the at least one pixel, the first subpixel controller has an area that is greater than the combined areas of the first light emitters or the second subpixel controller has an area that is greater than the combined areas of the second light emitters, or both.
In some embodiments of the present invention, the first subpixel controller is adjacent to the second subpixel controller.
In some embodiments of the present invention, the second subpixel is disposed in a rotated arrangement with respect to the first subpixel. The rotation can be 45 degrees, 90 degrees, 135 degrees, 180 degrees, 225 degrees, 270 degrees, or 315 degrees, or any other rotation.
In some embodiments of the present invention, the redundant pixel layout comprises an array of pixel substrates disposed on or over the display substrate. Each pixel is disposed on or over a corresponding pixel substrate. Any one or all of the pixel substrates, the first subpixel controllers, or the first light emitters can each comprise a broken or separated tether. For the at least one pixel, any one or all of the second subpixel controllers and the second light emitters can each comprise a broken or separated tether.
In some embodiments of the present invention, the redundant pixel layout comprises an array of first pixel substrates disposed on or over the display substrate and an array of second pixel substrates disposed on or over the display substrate. Each first subpixel is disposed on or over a corresponding first pixel substrate and each second subpixel is disposed on or over a corresponding second pixel substrate. Any one or all of the first pixel substrates, the second pixel substrates, the first subpixel controllers, or the first light emitters can each comprise a broken or separated tether. For the at least one pixel, any one or all of the second subpixel controllers and the second light emitters can each comprise a broken or separated tether.
In some embodiments, no other light emitter or subpixel controller in the first subpixel is closer to the second-light-emitter location than the first light emitter.
In another aspect, the present invention is directed to a method of making a redundant pixel layout comprises providing a redundant pixel layout for a display. For each pixel in the array of pixels, the method further comprises providing a second subpixel controller electrically connected to the controller wires and a second light emitter electrically connected to the second-light-emitter wire, where the second light emitter is controlled by the second subpixel controller at least through the second-light-emitter wire, and testing the first subpixels in the array of pixels to identify bad first subpixels. The first subpixels can each comprise a power wire and a ground wire and the method further comprises cutting at least one power wire, one ground wire, one controller wire, or the first-light-emitter wire in at least one bad first subpixel. The second subpixels in the array of pixels can be tested to identify second bad subpixels. The second subpixels can each comprise a power wire and a ground wire and the method can further comprise cutting at least one power wire, one ground wire, one controller wire, or the second-light-emitter wire in at least one bad second subpixel.
According to embodiments of the present invention, a method of making a redundant pixel layout comprises providing a redundant pixel layout for a display and testing the first subpixels in the array of pixels to identify bad first subpixels. For each bad first subpixel, the method further comprises disposing a second subpixel controller electrically connected to the controller wires and a second light emitter electrically connected to the second-light-emitter wire, where the second light emitter is controlled by the second subpixel controller at least through the second-light-emitter wire. The first subpixels can each comprise a power wire and a ground wire and comprising cutting at least one power wire, one ground wire, one controller wire, or the first-light-emitter wire in at least one bad first subpixel.
The present invention provides displays including arrays of pixels on a display substrate that are addressed using active-matrix-addressing methods. The systems can include a redundant layout and redundant components in pixels to improve manufacturability and visual quality. The systems can also employ small integrated circuits at a high resolution that are transfer printed to the display substrate.
The foregoing and other objects, aspects, features, and advantages of the present disclosure will become more apparent and better understood by referring to the following description taken in conjunction with the accompanying drawings, in which:
The features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The figures are not drawn to scale since the variation in size of various elements in the Figures is too great to permit depiction to scale.
The present invention provides, inter alia, structures and methods for an active-matrix display with small high-resolution elements that is tolerant of manufacturing and materials variability, particle contamination, and defects and that enables repair, thereby improving manufacturing yields and reducing costs. Moreover, certain embodiments of the present invention can provide improved visual color integration of multiple light emitters in a pixel that emit different colors of light. Certain embodiments of the present invention provide these advantages by providing redundant active-matrix controllers with redundant and adjacent light emitters in each pixel. In the event of a component failure in a pixel, redundant controllers or light emitters in the pixel can provide the operational capabilities of the failed component (e.g., wherein redundant controllers or light emitters continue to operate after failure of a component). In some embodiments, redundant controllers and redundant light emitters are disposed in redundant locations and electrically connected in every pixel. In certain embodiments, pixels can be tested and electrical connections to faulty controllers or faulty light emitters (or both) can be cut. In some embodiments, pixels with redundant controller locations and redundant light-emitter locations are tested to determine faulty pixels and redundant controllers and redundant light emitters disposed and electrically connected in locations of the faulty pixels to correct the fault.
Referring to the perspective of
First subpixel controllers 31 and second subpixel controllers 32 are collectively referred to as subpixel controllers 30; first light emitters 41 and second light emitters 42 that emit light of any color are collectively referred to as light emitters 40.
Second-subpixel-controller locations 33 are elements comprising one or more control wires 70 (e.g., portion(s) thereof), one or more electrically conductive elements (e.g., contact pads 74), or both that are disposed on, in, or over display substrate 10 (e.g., an area or portion thereof) on, over, or in which second subpixel controllers 32 can be disposed such that when disposed, the second subpixel controllers 32 are electrically connected to controller wires 70 and contact pads 74 to operate as intended (e.g., to control one or more second light emitters 42). Similarly, second-light-emitter locations 43 are elements comprising one or more second-light-emitter wires 72 (e.g., areas or portion(s) thereof), one or more electrically conductive elements (e.g., contact pads 74), or both disposed on, in, or over display substrate 10 (e.g., an area or portion thereof) on, over, or in which second light emitters 42 can be disposed such that when disposed, the second light emitters are electrically connected to second-light-emitter wire 72 and contact pads 74 to operate as intended (e.g., to emit light in response to control signals from a second subpixel controller 32).
Controller wires 70 can be electrically connected in common to both first and second subpixel controllers 31, 32 since the second subpixel 22 is redundant to the first subpixel 21. Controller wires 70, as used herein, can refer to, but are not limited to, wires that are used to provide control signals and power or ground (e.g., row lines 14, column lines 12, power wire 16, and ground wire 17) to first and second subpixels 21, 22. (The word “line” also refers to a “wire” and vice versa. Both are electrical conductors that convey electrical signals, voltages, or currents.) First subpixel controller 31 controls first light emitter 41 at least through first-light-emitter wire 71. Ground wire 17 can be electrically connected to first light emitter 41, second light emitter 42, first subpixel controller 31, and second subpixel controller 32 and can be considered any combination or all of a controller wire 70, a first-light-emitter wire 71, and a second-light-emitter wire 72. First-light-emitter wire 71 is electrically connected to both first light emitter 41 and first subpixel controller 31 to enable first subpixel controller 31 to control first light emitter 41. Similarly, second-light-emitter wire 72 is electrically connected to both second-light-emitter location 43 and second-subpixel-controller location 33 to enable control of second light emitter 42, as shown in
As used herein, a second subpixel 22 is redundant to first subpixel 21 if the second subpixel 22 is intended to replicate and have substantially identical functions and components (e.g., within manufacturing tolerances) as the first subpixel 21. For example, in certain embodiments, a second subpixel 22 comprising a second-subpixel location is redundant to a first subpixel 21 if, when a second subpixel controller 32 is disposed in a second-pixel-controller location 33 and electrically connected to controller wires 70 and a second light emitter 42 is disposed in a second-light-emitter location 43 and electrically connected to second-light-emitter wire 72, then the second subpixel 22 replicates and has substantially identical function to the first subpixel 21. Thus, first subpixel 21 can be electrically connected in parallel with second subpixel 22. In some such embodiments, second subpixel controller 32 is intended to be functionally identical to first subpixel controller 31 and second light emitter 42 is intended to be functionally identical to first light emitter 41 and second subpixel 22 is intended to be substantially identically electrically connected to the same inputs and outputs (if any) as first subpixel 21. Thus, in certain embodiments, if both first and second subpixels 21, 22 are operating properly, they will respond to the same input signals in the same way and at the same time to perform the same function.
If first subpixel 21 is defective, missing, or improperly connected to its electrical connections, a properly functional and electrically connected second subpixel 22 can operate in the place of first subpixel 21, or vice versa. In some embodiments of the present invention, first subpixel 21 is faulty. In some embodiments of the present invention, second subpixel 22 is faulty. In some embodiments of the present invention, a controller wire 70, first-light-emitter wire 71, second-light-emitter wire 72, a power wire 16, or a ground wire 17 in a pixel 20 is cut (e.g., to prevent operation of a faulty subpixel). In some embodiments, the cut wire is in a faulty first subpixel 21 or a faulty second subpixel 22, or both.
Referring to
According to some embodiments of the present invention, substantially identical components, functionality, operation, and electrical connections need not be exactly identical. Those familiar with manufacturing process control will understand that variations in materials and processes will result in corresponding differences in structures and functions in manufactured devices. As intended herein, “substantially identical” components, functions, or connections are intended to operate identically but can differ in their operation within manufacturing variability and tolerances. For example, first light emitter 41 can differ from substantially identical second light emitter 42 in efficiency, color of light emission, lifetime, and other operating characteristics or parameters if first and second light emitters 41, 42 are designed and intended to be the same.
As used herein, elements (e.g., light emitters 40, subpixel controllers 30, light-emitter locations 43, or subpixel-controller locations 33) disposed on or over display substrate 10 within a common pixel 20 that are “adjacent” have no spatially intervening element (e.g., no spatially intervening functionally similar element) on or over display substrate 10 in a direction D substantially parallel to a surface of display substrate 10 on which the elements are disposed. Hence, no other element within a common pixel 20 is between adjacent elements on or over the surface of display substrate 10. Thus, a first light emitter 41 in a first subpixel 21 is adjacent to a second light emitter 42 (or second-light-emitter location 43) in a second subpixel 22 in a common pixel 20 when there is no other first or second light emitter 41, 42 (or first-light-emitter location or second light-emitter location 43) in the first or second subpixel 21, 22 between them. Furthermore, in some embodiments, no subpixel controller 30 is closer to the adjacent first and second light emitters 41, 42. As used herein, elements are only “adjacent” when part of a common pixel 20 (i.e., the term is only applicable within a pixel 20). Thus, for example, light emitters 40 in a common pixel 20 can be adjacent or subpixel controllers 30 in a common pixel 20 can be adjacent, but light emitters 40 in different pixels 20 cannot be adjacent and subpixel controllers 30 in different pixels 20 cannot be adjacent. Components in different pixels 20 are not considered adjacent. As used herein, adjacent components can only include subpixel controllers 30, light emitters 40, and light emitter locations 43. Furthermore, controller wires 70, first light-emitter wires 71, and second light-emitter wires 72 are not considered adjacent and are not considered to intervene between adjacent light emitters 40, light emitter locations 43, subpixel controllers 30, or subpixel-controller locations 33, even if present. In some embodiments, a first element (e.g., light emitter 40, light-emitter location 43, subpixel controller 30, or subpixel-controller location 33) is adjacent to a second element (e.g., light emitter, 40, light-emitter location 43, subpixel controller 30, or subpixel-controller location 33) when there is no other element (e.g., light emitter 40, light-emitter location 43, subpixel controller 30, or subpixel-controller location 33) disposed therebetween and also the elements are equally close or closer together than any other element (e.g., light emitter 40, light-emitter location 43, subpixel controller 30, or subpixel-controller location 33) is to the first element. In some embodiments, for example, a first light emitter 41 in a first subpixel 21 is adjacent to a second light emitter 42 in a second subpixel 22 when no element (e.g., light emitter 40 or subpixel controller 30 of any subpixel (e.g., first or second subpixels 21, 22)) is disposed therebetween and the second light emitter 42 is the closest element (e.g., of the second subpixel 22) to the first light emitter 41 (or, in some embodiments, is equally close to the first light emitter 42 as another light emitter 40 (e.g., in the first subpixel 21 or second subpixel 22)).
For example, according to some embodiments of the present invention and as shown in
According to some embodiments of the present invention, first and second light emitters 41, 42 are disposed closer together on or over display substrate 10 and in a direction D substantially parallel to a surface of display substrate 10 on or over which the first and second light emitters 41, 42 are disposed than are any two pixels 20 in an array of pixels 20. According to some embodiments, first and second light emitters 41, 42 are disposed closer together on or over display substrate 10 and in a direction D substantially parallel to a surface of display substrate 10 on or over which the first and second light emitters 41, 42 are disposed than any two subpixel controllers 30 in different pixels 20 in the array of pixels 20. Since an objective of certain embodiments of the present invention is to provide robust pixels 20 that can operate in the presence of failed subpixel controllers 30 or light emitters 40, or both, and provide improved color integration of the light from pixels 20, it is desirable that the redundant components operate electrically, optically, visually, and spatially identically. By disposing first and second light emitters 41, 42 relatively close together, first and second light emitters 41, 42 are less visually distinguishable and therefore more readily appear as a single light emitter 40 at a single light-emitter location. As is well known in the art, the human visual system is sensitive to visible spatial discontinuities or disruptions in regular structures, such as an array of pixels 20 in a display 98. Thus, redundant second light emitters 42 that are not located in the same location as first light emitters 41 or in close proximity could be visible as an anomaly to a viewer. By disposing redundant second light emitters 42 in a subpixel location adjacent to and very close to the location of a first light emitter 41, any such visible anomalies or abnormalities are reduced or eliminated.
Referring to
In operation, system controller 96 of display 98 provides control signals to row controllers 94 and data signals to column controllers 92 through bus 18. Row and column controllers 94, 92 distribute the signals over row and column lines 14, 12 to pixels 20 to provide active-matrix control to the display 98. In a fully functional display 98, as illustrated in
If a first subpixel 21 in a pixel 20 is faulty, the second subpixel 22 can emit the desired amount of light from the pixel 20, or vice versa. In such embodiments, in operation the control and data signals are received by both first and second subpixel controllers 31, 32. Because first subpixel controller 31 or first light emitter 41 is faulty (or, e.g., the controller wire 70 or first-light-emitter wire 71 is faulty), light is not emitted as desired. However, second subpixel controller 32 can control second light emitter 42 to emit light as desired from pixel 20. Similarly, if second subpixel 22 is faulty, first subpixel 21 can provide the light desired from pixel 20. In some embodiments, pixels 20 are tested to determine any faulty first or second subpixels 21, 22 and the results of testing can be used to properly produce signals (e.g., from system controller 96 and/or first or second subpixel controllers 31, 32) to drive first and second subpixels 21, 22.
Display substrate 10 can be any suitable substrate having a surface on or over which pixels 20, first and second subpixels 21, 22, subpixel controllers 30, and light emitters 40 can be disposed, for example and without limitation, a substrate comprising glass, plastic, ceramic, quartz, sapphire, or a semiconductor as are used in the integrated circuit or display industry. Subpixel controllers 30, system controller 96, row controller 94, and column controller 92 can be integrated circuits or discrete components and can be analog, digital, or mixed-signal circuits and can be silicon circuits made using integrated circuit methods and materials. Light emitters 40 can be light-emitting diodes such as inorganic light-emitting diodes (ILEDs). Light emitters 40 can be formed in any one or more of a variety of doped or undoped compound semiconductors, such as, for example and without limitation, one or more of GaN, InGaN, GaAs, AlGaAs, GaAsP, GaP, AlGaInP, SiC, CdSe, CdS, and ZnSe.
In some embodiments, subpixel controllers 30, light emitters 40, or both, are provided in separate components with independent and separate substrates and are disposed on display substrate 10, for example using surface mount technology and assembly or using transfer printing. In some embodiments, subpixel controllers 30 or light emitters 40 comprise or are bare unpackaged die, integrated circuits, or unpackaged integrated circuits. In some embodiments, subpixel controllers 30 or light emitters 40 can be or include one or more of electronic circuits, optical circuits, transducers, light-emitting diodes, micro-light-emitting diodes, sensors, capacitive sensors, touch sensors, photo-sensors, electromagnetic radiation sensors, and piezo-electric sensors.
Transfer printing materials and methods can dispose very small devices on a substrate such as display substrate 10, for example having at least one of a length and a width less than or equal to 200, 100, 50, 20, or 10 microns. According to some embodiments of the present invention, such small devices can improve display resolution and the visual quality of display 98 by enabling the disposition of second light emitters 42 very close to first light emitters 41, so that viewers cannot readily visually distinguish second light emitters 42 from first light emitters 41 and substantially preventing spatial visual anomalies from displays 98 using redundant second light emitters 42 to improve display 98 yields and visual quality.
Referring to
According to some embodiments of the present invention, for example as shown in
In some embodiments, either first or second light emitters 41, 42 are reordered so that red first light emitter 41R is adjacent to red second light emitter 42R, green first light emitter 41G is adjacent to green second light emitter 42G, and blue first light emitter 41B is adjacent to blue second light emitter 42B, thus providing a compact layout and disposing first and second light emitters 41, 42 of each color closer.
Referring to
Certain embodiments of the present invention provide advantages in manufacturing repair and yields, as well as in color integration from light emitters 40 in a pixel 20, for example enabled by micro-transfer printing very small light emitters 40 such as inorganic micro-LEDs. In some embodiments, for example as shown in
Certain exemplary embodiments of the present invention have been constructed using micro-transfer printing. In an exemplary micro-transfer printing process, components such as light emitters 40 or subpixel controllers 30 are constructed on substrates of native source wafers, for example crystalline semiconductors. The native substrates can be of different types, for example compound semiconductors for light emitters 40 (e.g., when light emitters 40 are inorganic light emitting diodes) and silicon for subpixel controllers 30. The components are disposed over sacrificial portions separated by anchor portions of a sacrificial layer on the native wafers. The sacrificial portions are etched, for example with a liquid chemical etchant, to release the components from the native wafer leaving the components attached to the anchor portions by one or more tethers 60. A stamp, for example a PDMS stamp having a post for each component, is pressed against the components so that a component is adhered to each post, the stamp is removed so that the tethers 60 fracture or separate, leaving the components adhered to the stamp posts. The components on the posts are then pressed against a destination substrate to adhere the components to the destination substrate, and the stamp is removed, leaving components with fractured or separated tethers 60 on the destination substrate, where they can be further processed, for example photolithographically processed to electrically interconnect the components, or can be tested.
In some embodiments of the present invention, referring to
In some embodiments of the present invention, referring to
In certain embodiments, one or more of light emitters 40 and subpixel controllers 30 comprise one or more connection posts for making appropriate electrical connection to electrical connections disposed on pixel substrate 50 (if present), subpixel substrate 51, 52 (if present), or display substrate 10. In certain embodiments, one or more of first light emitters 41, second light emitters 42, first subpixel controllers 31, and second subpixel controllers 32 can comprise one or more connection posts for making appropriate electrical connection to electrical connections disposed on first subpixel substrate 51 or second subpixel substrate 52. Connections posts, methods of fabrication, and methods for making electrical connection using connections posts are described in U.S. Patent Publication No. 2017/0048976 A1, the disclosure of which is hereby incorporated by reference in it is entirety.
In some embodiments of the present invention, a pixel 20 comprising a pixel substrate 50 or first or second subpixel 21, 22 comprising first or second subpixel substrates 51, 52, respectively, further comprises one or more connection posts extending from the substrate in a direction such that when transferred onto or over a display substrate 10, the one or more connection posts extend toward display substrate 10. In this way, pixel 20 or first or second subpixel 21, 22 can be transferred (e.g., micro-transfer printed) onto display substrate 10, which comprises electrical connections (e.g., one or more of controller wires 70 (e.g., power wire 16, ground wire 17, row line 14, column line 12) and contact pads 74) such that upon transfer, pixel 20 or first or second subpixel 21, 22 becomes electrically connected through the one or more connection posts to be operable as intended. A curable adhesive can be used between pixel substrate 50 or first or second subpixel substrate 51, 52 and cured as a part of a transfer process to improve adhesion of pixel 20 or first or second subpixel 21, 22 to display substrate 10. Optionally, curing of a curable adhesive can improve or cause electrical interconnection between pixel 20 or subpixel 21, 22, respectively. First-light-emitter wire(s) 71 and second-light-emitter wire(s) 72 can be pre-patterned on pixel substrate 50 or subpixel substrate 51, 52, respectively. Use of pixels 20 comprising a pixel substrate 50 and one or more connection posts or subpixels 21, 22 comprising a first or second subpixel substrate 51, 52 and one or more connection posts can reduce or eliminate the need to photolithographically form wires after transfer of pixels 20 or first or second subpixels 21, 22 to a display substrate 10 thereby reducing manufacturing costs.
Referring to
Referring to
Referring to
Display substrate 10 can be a printed circuit board or a glass, metal, ceramic, resin, semiconductor, quartz, sapphire, or polymer substrate. Subpixel controllers 30 or light emitters 40 can be chiplets that are micro-transfer printed onto display substrate 10. Electrically conductive row lines 14, column lines 12 can be patterned wires, conductive traces, cured conductive ink, or other electrical conductors suitable for pattern-wise conducting electricity on a substrate and can be made of copper, silver, gold, aluminum, titanium, tantalum, conductive metal, transparent conductive oxides (TCOs) such as indium tin oxide, or any other conductive material. Conductive row lines 14 or column lines 12 can be patterned and interconnected or electrically isolated over display substrate 10 using photolithographic or printed circuit board techniques. Generally, controller wires 70, whether disposed on an intermediate substrate (e.g., a pixel substrate 50 or a first or second subpixel substrate 51, 52) or a display substrate 10 can be formed lithographically. Controller wires 70 can be formed, for example, either before or after transfer of any one or combination of a pixel 20, subpixel 21, 22, subpixel controller 30, or light emitter 40. That is, one or more (e.g., all) of controller wires 70 can be disposed in some embodiments at least partially (and in some embodiments exclusively) under, over, or on a side (e.g., wrapping up onto the side) of a light emitter 40, subpixel controller 30, pixel substrate 50, or subpixel substrate 51, 52.
Pixels 20 are matrix addressed through row and column lines 14, 12 by supplying signals on the row and column lines 14, 12. Additional power wires 16 and ground wires 17 or other control signals can be provided to pixels 20 (not shown in
In operation, row controller 94 and column controller 92 matrix address pixels 20 in display 98. Row controller 94 selects a row by providing a row select signal (for example a voltage or a digital signal such as a digital HIGH value or a one) on row line 14 corresponding to the row of pixels 20 that are addressed. Column controller 92 provides data on column lines 12 and the data is combined with the row select signal (for example using a digital AND gate or a voltage differential between row and column lines 14, 12) by subpixel controllers 30 to enter data into subpixel controllers 30 and cause light emitters 40 to operate and emit light. Thus, one row of pixels 20 is addressed at one time. After one row of pixels 20 are addressed, another row can be addressed in the same way, for example a neighboring row, until all of the rows have been addressed. The data provided on column lines 12 can be provided by system controller 96 through column controller 92, for example by shifting data values along a serial shift register until the data is aligned with the column of pixels 20 for which the data is intended for the selected row. System, row, and column controllers 96, 94, 92 can be digital integrated circuits with appropriate driver circuits, such as transistors, for providing electrical signals on row and column lines 14, 12.
As will be understood by those knowledgeable in the art, the terms “row” and “column” are arbitrary appellations that can be exchanged without affecting the functionality or structure of the present invention. Hence, the terms row and column can be interchanged without affecting the structure or operation of the present invention and are included in the present invention. Further, it is understood that the terms “first” and “second” as used herein throughout are arbitrary designations and any description of a “first” element or “second” element could likewise written as a corresponding description of a “second” element or “first” element, respectively.
In some embodiments of the present invention, subpixel controllers 30 or light emitters 40 can be defective (or, as used interchangeably, “faulty” or “failed”), for example having failed circuitry or failed electrical connections to controller wires 70 or first- or second-light-emitter wires 71, 72. In this context, a failure can include, for example: (i) a shorted wire or one that is overly conductive; (ii) a non-conductive wire or an electrical open; (iii) a non-reactive or non-functional subpixel controller 30 or light emitter 40; (iv) an absent subpixel controller 30 or light emitter 40 such as one that failed to print or adhere adequately to display substrate 10, pixel substrate 50, or one of first and second subpixel substrate 51, 52, or is printed to a wrong location; (v) a subpixel controller 30 or light emitter 40 with unintended output, for example the wrong brightness, light output distribution, or color; or (vi) a subpixel controller 30 or light emitter 40 that functions only intermittently. In certain embodiments, a pixel 20 or subpixel 21, 22 is tested to determine whether one or more of (i)-(vi) is true. Testing can be optical, electrical, or both optical and electrical testing.
In some embodiments of the present invention, subpixel controllers 30 or light emitters 40 are small integrated circuits, for example chiplets, having a thin substrate with a thickness of only a few microns, for example less than or equal to 25 microns, less than or equal to 15 microns, or less than or equal to 10 microns, and at least one of a width and length of between 5-1000 microns (e.g., 5-10 microns, 10-50 microns, 50-100 microns, or 100-200 microns, 200-500 microns, or 500-1000 microns). Such chiplets can be made in a source semiconductor wafer (e.g., a silicon or GaN wafer) having a process side and a back side used to handle and transport the wafer. Chiplets are formed using lithographic processes in an active layer on or in the process side of the source wafer. In certain embodiments, an empty release layer space is formed beneath the chiplets with tethers 60 connecting the chiplets to the source wafer in such a way that pressure applied against or tension applied to the chiplets breaks or separates the tethers 60 to release the chiplets from the source wafer, for example with a micro-transfer printing stamp. Methods of forming and transferring such structures are described, for example, in U.S. Pat. No. 8,889,485 the disclosure of which is incorporated by reference herein in its entirety.
Lithographic processes for forming chiplets in a source wafer, for example transistors, wires, and capacitors, can be found in the integrated circuit art. The chiplets can be constructed using foundry fabrication processes used in the art. Layers of materials can be used, including materials such as metals, oxides, nitrides and other materials used in the integrated-circuit art. Each chiplet can be a complete semiconductor integrated circuit and can include, for example, transistors. The chiplets can have different sizes, for example, 1000 square microns or 10,000 square microns, 100,000 square microns, or 1 square mm, or larger, and can have variable aspect ratios, for example 1:1, 2:1, 5:1, or 10:1. The chiplets can be rectangular or can have other shapes. In certain embodiments, electrically conducting wires, such as controller wires 70, include patterned metal layers forming contact pads 74. The contact pads 74 can be made using integrated circuit photolithographic methods.
According to some embodiments of the present invention, native source wafers can be provided with the chiplets, release layer, and tethers 60 already formed, or they can be constructed as part of a method in accordance with certain embodiments of the present invention.
The chiplets can be constructed using foundry fabrication processes used in the art. Layers of materials can be used, including materials such as metals, oxides, nitrides and other materials used in the integrated-circuit art. Each chiplet can be a complete semiconductor integrated circuit and can include, for example, transistors. The chiplets can have different sizes, for example, 1000 square microns or 10,000 square microns, 100,000 square microns, or 1 square mm, or larger, and can have variable aspect ratios, for example 1:1, 2:1, 5:1, or 10:1. The chiplets can be rectangular or can have other shapes.
A source wafer and chiplets and display substrate 10 can be made separately and at different times or in different temporal orders or locations and provided in various process states.
Matrix-addressed systems according to certain embodiments of the present invention can be constructed using display and thin-film manufacturing method independently of or in combination with micro-transfer printing methods, for example as are taught in U.S. Pat. No. 9,520,537 entitled Micro Assembled Micro LED Displays and Lighting Elements and in U.S. patent application Ser. No. 14/822,868 filed Sep. 25, 2014, entitled Compound Micro-Assembly Strategies and Devices, the contents of which are incorporated by reference herein in their entirety.
As is understood by those skilled in the art, the terms “over” and “under” are relative terms and can be interchanged in reference to different orientations of the layers, elements, and substrates included in the present invention. For example, a first layer on a second layer, in some implementations means a first layer directly on and in contact with a second layer. In other implementations a first layer on a second layer includes a first layer and a second layer with another layer therebetween.
Having described certain implementations of embodiments, it will now become apparent to one of skill in the art that other implementations incorporating the concepts of the disclosure may be used. Therefore, the disclosure should not be limited to certain implementations, but rather should be limited only by the spirit and scope of the following claims.
Throughout the description, where apparatus and systems are described as having, including, or comprising specific components, or where processes and methods are described as having, including, or comprising specific steps, it is contemplated that, additionally, there are apparatus, and systems of the disclosed technology that consist essentially of, or consist of, the recited components, and that there are processes and methods according to the disclosed technology that consist essentially of, or consist of, the recited processing steps.
It should be understood that the order of steps or order for performing certain action is immaterial so long as the disclosed technology remains operable. Moreover, two or more steps or actions in some circumstances can be conducted simultaneously. The invention has been described in detail with particular reference to certain embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
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