PATENT DOCUMENT

Publication Number: US-10381381-B1
Application Number: US-201615274546-A
Country: US
Kind Code: B1

Title: Display with light transmitting windows

Abstract:
A display may have an array of pixels with light-emitting diodes that emit light to form images. The display may have a substrate with thin-film transistor circuitry for supplying signals to the light-emitting diodes. Anodes may be formed on the thin-film transistor circuitry, emissive material may be formed on the anodes, and a cathode layer may overlap the anodes. During operation, currents may flow between the anodes and the cathode layer to illuminate the diodes. An array of electrical components such as an array of light sensors in an integrated circuit may be mounted under the substrate. An array of corresponding light transmitting windows may be formed in the display each of which may allow light to pass through the display to a corresponding one of the light sensors. Light transmitting windows may be formed by patterning the cathode layer and supplying the windows with antireflection layers.

Claims:
What is claimed is: 
     
       1. A display, comprising:
 a substrate; 
 thin-film circuitry on the substrate that comprises an array of light-emitting diodes, wherein the thin-film circuitry includes a cathode layer that overlaps the array of light-emitting diodes and wherein each light-emitting diode includes an anode and includes emissive material interposed between the anode of that light-emitting diode and the cathode layer, wherein the thin-film circuitry comprises a pixel definition layer that has openings, and wherein each of the openings in the pixel definition layer is aligned with a respective one of the anodes; and 
 electrical components, wherein the substrate is interposed between the electrical components and the thin-film circuitry, wherein the thin-film circuitry is configured to form light transmitting windows each of which is aligned with a corresponding one of the electrical components, wherein the cathode layer has openings that overlap the light transmitting windows to enhance light transmission through the light transmitting windows, and wherein the light transmitting windows overlap portions of the pixel definition layer without openings. 
 
     
     
       2. The display defined in  claim 1  wherein the electrical components comprise light sensors. 
     
     
       3. The display defined in  claim 2  wherein the light sensors are part of an integrated circuit. 
     
     
       4. The display defined in  claim 3  wherein the integrated circuit has through-silicon vias and is mounted to a flexible printed circuit. 
     
     
       5. The display defined in  claim 2  wherein openings in the cathode layer comprise laser-ablated openings. 
     
     
       6. A display having an array of pixels configured to display images, the display comprising:
 a substrate; 
 thin-film circuitry on the substrate that comprises an array of light-emitting diodes, wherein the thin-film circuitry includes a cathode layer that overlaps the array of light-emitting diodes and wherein each light-emitting diode includes an anode and includes emissive material interposed between the anode of that light-emitting diode and the cathode layer; and 
 electrical components, wherein the substrate is interposed between the electrical components and the thin-film circuitry, wherein the thin-film circuitry is configured to form light transmitting windows interspersed with at least a portion of the array of pixels, wherein each of the light transmitting windows is aligned with a corresponding one of the electrical components, wherein the windows have antireflection layers, wherein the antireflection layers include at least one inorganic dielectric layer interposed between the cathode layer and the emissive material in the windows. 
 
     
     
       7. The display defined in  claim 6  wherein the electrical components comprise light sensors. 
     
     
       8. The display defined in  claim 7  wherein the antireflection layers further includes a second layer between the cathode layer and an organic capping layer and a third layer. 
     
     
       9. The display defined in  claim 7  wherein the at least one inorganic dielectric layer is a silicon oxide layer. 
     
     
       10. The display defined in  claim 9  wherein the antireflection layers further include at least one silicon nitride layer. 
     
     
       11. The display defined in  claim 7  wherein none of the inorganic dielectric antireflection layer is interposed between the cathode layer and the emissive material in the light-emitting diodes. 
     
     
       12. The display defined in  claim 7  wherein the cathode layer has a first area that does not overlap the windows and has a second area that overlaps that windows and wherein the cathode layer is thinner in the second area than in the first area. 
     
     
       13. The display defined in  claim 12  wherein the light sensors are part of an integrated circuit. 
     
     
       14. The display defined in  claim 13  wherein the integrated circuit has through-silicon vias and is mounted to a flexible printed circuit. 
     
     
       15. A display, comprising:
 a substrate; 
 thin-film circuitry on the substrate that comprises an array of light-emitting diodes, wherein the thin-film circuitry includes a cathode layer that overlaps the array of light-emitting diodes and wherein each light-emitting diode includes an anode and includes emissive material interposed between the anode of that light-emitting diode and the cathode layer; and 
 an array of light sensors, wherein the substrate is interposed between the array of light sensors and the thin-film circuitry and wherein the thin-film circuitry is configured to form light transmitting windows each of which is aligned with a corresponding one of the light sensors, wherein the cathode layer has a first thickness in a first region of the thin-film circuitry that overlaps the array of light sensors and wherein the cathode layer has a second thickness that is greater than the first thickness in a second region of the thin-film circuitry that overlaps the array of light-emitting diodes and does not overlap the array of light sensors.

Description:
This application claims the benefit of provisional patent application No. 62/244,112, filed Oct. 20, 2015, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices, and, more particularly, to electronic devices with displays. 
     Electronic devices often include displays. Displays such as organic light-emitting diode displays have pixels with light-emitting diodes. The pixels may be arranged in an array and used to display images for a user. 
     It may be desirable to incorporate electrical components into an array of pixels. If care is not taken, electrodes and other circuitry in a display may interfere with these components. 
     It would therefore be desirable to be able to provide improved display arrangements for accommodating electrical components. 
     SUMMARY 
     A display may have an array of pixels with light-emitting diodes that emit light to form images. The display may have a substrate with thin-film transistor circuitry. The thin-film transistor circuitry may form pixel circuits that supply signals to the light-emitting diodes. 
     Anodes may be formed on the thin-film transistor circuitry, emissive material may be formed on the anodes, and a cathode layer may be formed that covers the emissive material. During operation, currents may flow between the anodes and the cathode layer to illuminate the array of diodes in a desired pattern. 
     An array of electrical components such as an array of light sensors in an integrated circuit may be mounted under the substrate. An array of corresponding light transmitting windows may be formed in the display. The light transmitting windows may be more transparent than other portions of the display. Each light transmitting window may allow light to pass through the display to a corresponding one of the light sensors. 
     Light transmitting windows may be formed by patterning the cathode layer to create regions of enhanced light transmission. Windows may also be provided with antireflection layers. Techniques for patterning the cathode layer may involve lift-off, shadow masking of the cathode, and laser processing. 
     Further features will be more apparent from the accompanying drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device having a display in accordance with an embodiment. 
         FIG. 2  is a top view of an illustrative display in an electronic device in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of a portion of an illustrative organic light-emitting diode display in accordance with an embodiment. 
         FIG. 4  is diagram of an illustrative pixel cell having pixels of different colors in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of a display with an array of electrical components in accordance with an embodiment. 
         FIGS. 6, 7, 8, and 9  are cross-sectional side views of a display that is being fabricated using lift-off techniques to create optical windows to accommodate light-based electrical components in accordance with an embodiment. 
         FIG. 10  is a top view of an illustrative touch sensor in accordance with an embodiment. 
         FIGS. 11, 12, and 13  are cross-sectional side views of a display showing how touch sensors may be fabricated in accordance with an embodiment. 
         FIG. 14  is a top view of an illustrative shadow mask with vertical mask elements that may be used during a first cathode layer deposition operation in accordance with an embodiment. 
         FIG. 15  is a top view of a display in which a cathode layer has been deposited through a shadow mask of the type shown in  FIG. 14  to create vertical strips that are free of cathode material in accordance with an embodiment. 
         FIG. 16  is a top view of an illustrative shadow mask with horizontal mask elements that may be used during a second cathode layer deposition operation in accordance with an embodiment. 
         FIG. 17  is a top view of an illustrative display following cathode layer deposition operations using the masks of  FIGS. 14 and 16  in accordance with an embodiment. 
         FIG. 18  is a top view of an illustrative shadow mask with horizontal masking strips in accordance with an embodiment. 
         FIG. 19  is a top view of an illustrative display having horizontal strips of cathode material that have been formed using a mask of the type shown in  FIG. 18  and that includes vertical metal lines that short the horizontal strips together in accordance with an embodiment. 
         FIG. 20  is a cross-sectional side view of the display of  FIG. 19  showing how cathode material may be shorted to metal lines in accordance with an embodiment. 
         FIGS. 21 and 22  are cross-sectional side views of displays being processed using illustrative laser processing systems to form optically transparent windows in the displays in accordance with an embodiment. 
         FIG. 23  is a cross-sectional side view of a portion of a display showing how antireflection structures may be used to create optically transparent windows in the display in accordance with an embodiment. 
         FIG. 24  is a top view of a display showing how a portion of the display may have an array of light transmitting windows in accordance with an embodiment. 
         FIGS. 25 and 26  are top views of illustrative patterns that may be used in depositing portions of a cathode in accordance with an embodiment. 
         FIG. 27  is a cross-sectional side view of an illustrative cathode layer that has been processed to form a locally thinned region that can overlap an array of light transmitting windows in accordance with an embodiment. 
         FIG. 28  is a cross-sectional side view of an illustrative light transmitting window that has been formed in a region of a display that has a locally thinned cathode layer in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with a display is shown in  FIG. 1 . Device  10  may be a portable computer, a cellular telephone, a wrist-watch device, a monitor, a desktop computer, a tablet computer, or other suitable electronic equipment. As shown in  FIG. 1 , electronic device  10  may have control circuitry  16 . Control circuitry  16  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  16  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     Input-output circuitry in device  10  such as input-output devices  12  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  12  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, data ports, and other electrical components. A user can control the operation of device  10  by supplying commands through input-output devices  12  and may receive status information and other output from device  10  using the output resources of input-output devices  12 . 
     Input-output devices  12  may include one or more displays such as display  14 . Display  14  may be a touch screen display that includes a touch sensor for gathering touch input from a user or display  14  may be insensitive to touch. A touch sensor for display  14  may be based on an array of capacitive touch sensor electrodes, acoustic touch sensor structures, resistive touch components, force-based touch sensor structures, light-based touch sensor components, or other suitable touch sensor arrangements. 
     Control circuitry  16  may be used to run software on device  10  such as operating system code and applications. During operation of device  10 , the software running on control circuitry  16  may display images on display  14  using an array of pixels in display  14 . 
     Display  14  may be an organic light-emitting diode display or may be a display based on other types of display technology. Configurations in which display  14  is an organic light-emitting diode display are sometimes described herein as an example. This is, however, merely illustrative. Any suitable type of display may be used, if desired. 
     Display  14  may have a rectangular shape (i.e., display  14  may have a rectangular footprint and a rectangular peripheral edge that runs around the rectangular footprint), may have an oval or circular shape, or may have other suitable shapes. Display  14  may be planar or may have a curved profile. 
     A top view of a portion of display  14  is shown in  FIG. 2 . As shown in  FIG. 2 , display  14  may have an array of pixels  22  formed on substrate  36 . Substrate  36  may be formed from glass, metal, plastic, ceramic, or other substrate materials. Pixels  22  may receive data signals over signal paths such as data lines D and may receive one or more control signals over control signal paths such as horizontal control lines G (sometimes referred to as gate lines, scan lines, emission control lines, etc.). There may be any suitable number of rows and columns of pixels  22  in display  14  (e.g., tens or more, hundreds or more, or thousands or more). Each pixel  22  may have a light-emitting diode  26  that emits light  24  under the control of a pixel circuit formed from thin-film transistor circuitry such as thin-film transistors  28  and thin-film capacitors). Thin-film transistors  28  may be polysilicon thin-film transistors, semiconducting-oxide thin-film transistors such as indium gallium zinc oxide transistors, or thin-film transistors formed from other semiconductors. Pixels  22  may contain light-emitting diodes of different colors (e.g., red, green, and blue diodes for red, green, and blue pixels, respectively) to provide display  14  with the ability to display color images. 
     Display driver circuitry may be used to control the operation of pixels  22 . The display driver circuitry may be formed from integrated circuits, thin-film transistor circuits, or other suitable circuitry. Display driver circuitry  30  of  FIG. 2  may contain communications circuitry for communicating with system control circuitry such as control circuitry  16  of  FIG. 1  over path  32 . Path  32  may be formed from traces on a flexible printed circuit or other cable. During operation, the control circuitry (e.g., control circuitry  16  of  FIG. 1 ) may supply circuitry  30  with information on images to be displayed on display  14 . 
     To display the images on display pixels  22 , display driver circuitry  30  may supply image data to data lines D while issuing clock signals and other control signals to supporting display driver circuitry such as gate driver circuitry  34  over path  38 . If desired, circuitry  30  may also supply clock signals and other control signals to gate driver circuitry on an opposing edge of display  14 . In the example of  FIG. 2 , circuitry  30  is located along the upper edge of display  14  and circuitry  34  is located along the left and/or right edge of display  14 . Display driver circuitry may also be provided along different sets of edges or along only a single edge of display  14 . 
     Gate driver circuitry  34  (sometimes referred to as horizontal control line control circuitry) may be implemented as part of an integrated circuit and/or may be implemented using thin-film transistor circuitry. Horizontal control lines G in display  14  may carry gate line signals (scan line signals), emission enable control signals, and other horizontal control signals for controlling the pixels of each row. There may be any suitable number of horizontal control signals per row of pixels  22  (e.g., one or more, two or more, three or more, four or more, etc.). 
     A cross-sectional side view of a portion of an illustrative organic light-emitting diode display that includes a light-emitting diode (diode  26 ) and thin-film transistor circuitry for an associated pixel circuit (thin-film transistor circuitry  48 ) is shown in  FIG. 3 . As shown in  FIG. 3 , display  14  may include a substrate layer such as substrate layer  36 . Substrate  36  may be a planar layer or a non-planar layer and may be formed from plastic (e.g., a sheet of polyimide or other polymer), glass, ceramic, sapphire, metal, or other suitable materials. The surface of substrate  36  may, if desired, be covered with one or more buffer layers  62 . 
     A pixel circuit may be formed from thin-film circuitry  48  on substrate  36 . The thin film transistor circuitry may include transistors, capacitors, and other thin-film structures. As shown in  FIG. 3 , a transistor such as thin-film transistor  28  may be formed from thin-film semiconductor layer  60 . Semiconductor layer  60  may be a polysilicon layer, a semiconducting-oxide layer such as a layer of indium gallium zinc oxide, or other semiconductor layer. Gate layer  56  may be a conductive layer such as a metal layer that is separated from semiconductor layer  60  by an intervening layer of dielectric such as dielectric  58  (e.g., an inorganic gate insulator layer such as a layer of silicon oxide and/or silicon nitride). Dielectric  62  (e.g., one or more buffer layers) may be used to separate semiconductor layer  60  from substrate  36 . Underlying structures such as shield layer  64  may be formed under gate  56  (e.g., between buffer layers  62 ). Layers  62  may be formed from inorganic dielectric materials such as silicon oxide and/or silicon nitride, or may be formed form other insulating materials. 
     Semiconductor layer  60  of transistor  28  may be contacted by source and drain terminals formed from source-drain metal layer  52 . One or more interlayer dielectric layers or other insulating material such as dielectric layer  54  (e.g., an inorganic dielectric layer with one or more sublayers of material such as silicon oxide, silicon nitride, etc.) may separate gate metal layer  56  from source-drain metal layer  52 . A dielectric passivation layer (e.g., a layer of silicon oxide or other inorganic layer) such as passivation layer  68  may cover source-drain metal layer  52 . 
     Thin-film transistor circuitry  48  (e.g., source-drain metal layer  52 ) may be shorted to anode  42  of light-emitting diode  26  using a metal via such as via  66  that passes through dielectric planarization layer  70  and passivation layer  68 . Passivation layer  68  may be formed from a layer of inorganic dielectric (as an example). Planarization layer  70  may be formed from an organic dielectric material such as a polymer. The thickness of planarization layer  70  may be 2 microns, 1-3 microns, less than 4 microns, more than 1.5 microns, or other suitable thickness. The index of refraction of layer  70  may be about 1.5. 
     Light-emitting diode  26  is formed from thin-film circuitry such as light-emitting diode layers  40  on thin-film transistor circuitry  48 . Each light-emitting diode has a lower electrode and an upper electrode. In a top emission display, the lower electrode may be formed from a reflective conductive material such as patterned metal to help reflect light that is produced by the light-emitting diode in the upwards direction out of the display. The upper electrode (sometimes referred to as the counter electrode) may be formed from a transparent or semi-transparent conductive layer (e.g., a thin layer of transparent or semitransparent metal and/or a layer of indium tin oxide or other transparent conductive material). This allows the upper electrode to transmit light outwards that has been produced by emissive material in the diode. In a bottom emission display, the lower electrode may be transparent (or semi-transparent) and the upper electrode may be reflective. 
     In configurations in which the anode is the lower electrode, layers such as a hole injection layer, hole transport layer, emissive material layer, and electron transport layer may be formed above the anode and below the upper electrode, which serves as the cathode for the diode. In inverted configurations in which the cathode is the lower electrode, layers such as an electron transport layer, emissive material layer, hole transport layer, and hole injection layer may be stacked on top of the cathode and may be covered with an upper layer that serves as the anode for the diode. Both electrodes may reflect light. 
     In general, display  14  may use a configuration in which the anode electrode is closer to the display substrate than the cathode electrode or a configuration in which the cathode electrode is closer to the display substrate than the anode electrode. In addition, both bottom emission and top emission arrangements may be used. Top emission display configurations in which the anode is located on the bottom and the cathode is located on the top are sometimes described herein as an example. This is, however, merely illustrative. Any suitable display arrangement may be used, if desired. 
     In the illustrative configuration of  FIG. 3 , display  14  has a top emission configuration and lower electrode  42  is an anode and upper electrode  46  is a cathode. Layers  40  include a patterned metal layer that forms anodes such as anode  42 . Each anode  42  is formed under a respective opening in pixel definition layer  72 . Pixel definition layer  72  may be formed from a patterned photoimageable polymer (e.g., polyimide). 
     In each light-emitting diode, organic emissive material  44  is interposed between a respective anode  42  and cathode  46 . The thickness of material  44  may be about 140 nm or other suitable thickness. Anodes  42  may be patterned from a layer of metal on planarization layer  70 . Cathode  46  may be formed from a common conductive layer that is deposited on top of pixel definition layer  72  and that overlaps diodes  26 . Cathode  46  is transparent so that light  24  may exit light emitting diode  26  as current is flowing through emissive material  44  between anode  42  and cathode  46 . 
     Organic light-emitting diode display structures such as the layer of emissive material  44  and other thin-film circuitry in display  14  may be sensitive to moisture. Accordingly, organic light-emitting diode layers  40  may be covered with encapsulation layers such as layer  74 . Encapsulation layer  74  may include organic and inorganic sublayers that serve as moisture barrier materials, planarization layers, adhesive layers, buffer layers, and other structures for protecting diode  26 , transistor  28 , and other thin-film circuitry in display  14 . 
     If desired, display  14  may have a protective outer display layer such as cover layer  78 . The outer display layer may be formed from a material such as sapphire, glass, plastic, clear ceramic, or other transparent material. 
     Functional layers  76  may be interposed between layer  74  and cover layer  78 . Functional layers  76  may include a touch sensor layer, a circular polarizer layer, and other layers. A circular polarizer layer may help reduce light reflections from reflective structures such as anodes  42  and/or other thin-film circuitry in display  14 . A touch sensor layer may be formed from an array of capacitive touch sensor electrodes on a flexible polymer substrate. The touch sensor layer may be used to gather touch input from the fingers of a user, from a stylus, or from other external objects. Layers of optically clear adhesive may be used to attach cover layer  78  and functional layers  76  to underlying display layers such as layer  74 . If desired, touch sensor electrodes may be incorporated into the thin-film layers of light-emitting diode layer  40  and/or thin-film transistor circuitry  48 . 
     Organic layer  44  may include an organic emissive layer (e.g., a red emissive layer in red diodes  26  that emits red light, a green emissive layer in green diodes  26  that emits green light, and a blue emissive layer in blue diodes  26  that emits blue light, etc.). The emissive material may include a material such as a phosphorescent material or fluorescent material that emits light during diode operation. Quantum dots may be used to form quantum dot light emitting diodes. 
     Display  14  may contain an array of pixels  22  to display images. In some areas of display  14  such as area  90 , the structures of display  14  may be configured to form a transparent area. The transparent area may be more transparent than surrounding portions of display  14  and may therefore sometimes be referred to as a region of enhanced transparency or enhanced light transmission, an optical window, a transparent window, a light transmitting window, or a light window (as examples). Windows such as window  90  of  FIG. 3  may be formed in an array, in a single location on display  14 , in a sparse array pattern or other pattern that is interspersed with a portion or all of the array of pixels  22  in display  14 , or may be located in other suitable portions of display  14 . During operation of device  10 , light from outside of device  10  such as light  92  may pass through window  90  and may be received by a light sensor or other light-based component in device  10  (e.g., a part of a light sensor array integrated circuit or other device that is located within the interior of device  10  under display  14 ). Light  92  may be light  24  from display  14  that has reflected from an external object, may be ambient light, may be light that has been emitted by device  10  without using pixels  22  of display  14 , or may be other suitable light. If desired, light may pass outwardly through window  90  (e.g., from a light-emitting diode, laser, or other light source inside device  10 ). 
     Display  14  may have an array of pixels  22  of different colors to provide display  14  with the ability to display color images. As shown in  FIG. 4 , each pixel cell  22 P in display  14  may contain a red pixel  22 R, a green pixel  22 G, and a blue pixel  22 B (as an example). These pixels, which may sometimes be referred to as subpixels, may have rectangular emissive areas (e.g., rectangular anode shapes) and/or may have emissive areas of other suitable shapes. White pixels, yellow pixels, and pixels of other colors may also be included in display  14 , if desired. 
     It may be desirable to incorporate electrical components into display  14  and/or device  10 . As shown in  FIG. 5 , for example, electrical components  84  may be mounted under display layers  94  (e.g., a substrate, thin-film transistor circuitry, light-emitting diode circuitry, etc.). Electrical components  84  may be audio components (e.g., microphones, speakers, etc.), radio-frequency components, haptic components (e.g., piezoelectric structures, vibrators, etc.), may be capacitive touch sensor components or other touch sensor structures, may be temperature sensors, pressure sensors, magnetic sensors, or other sensors, or may be any other suitable type of electrical component. With one suitable arrangement, which may sometimes be described herein as an example, electrical components  84  may be light-based components (e.g., components that emit and/or detect visible light, infrared light, and/or ultraviolet light). 
     Components  84  may be light sensors and/or light emitters that are aligned with corresponding windows  90 . Components  84  may, as an example, be light sensors that are formed as part of a common integrated circuit such as device  82  (e.g., a light-sensor integrated circuit, sometimes referred to as a camera or light sensor array). Device  82  may have through-silicon vias such as vias  95  to couple front-side circuitry (e.g., circuitry including components  84 ) to metal traces on substrate  97 . Substrate  97  may be a printed circuit (e.g., a rigid printed circuit board formed from a rigid printed circuit board material such as fiberglass-filled epoxy or a flexible printed circuit formed from a flexible layer of polyimide or other sheet of polymer). Device  82  or one or more discrete light sensors may be mounted on substrate  97  using solder connections, anisotropic conductive film connections, or connections formed using other conductive material. If desired, components  84  and/or device  82  may be integrated into the layers that make up display  14  and/or may be mounted in alignment with display  14 . 
     Light-based components  84  may emit and/or detect light that passes through transparent windows  90  in display  14 . Windows  90  may be formed in regions located between pixels  22  and may include transparent materials (e.g., clear plastic, glass, etc.) and/or holes (e.g., air-filled openings or openings filled with transparent material that pass partly or fully through substrate  36  and other display layers  94  of display  14 ). There may be a window  90  between each pair of pixels  22  or, more preferably, there may be a window  90  may be associated with a set of multiple pixels  22  (e.g., a set of tens, hundreds, or thousands of pixels). In some configurations, windows  90  may be formed in an array in a portion of display  14 . 
     Examples of light-based components  84  that emit light include light-emitting diodes (e.g., organic light-emitting diodes, discrete crystalline light-emitting diode dies, etc.), lasers, and lamps. Examples of light-based components that detect light include light detectors such as photodiodes and phototransistors. Some components may, if desired, include both light emitters and detectors. For example, components  84  may emit infrared light or light at other wavelengths and may include light detector structures for detecting a portion of the emitted light that has reflected from nearby objects such as object  96 . Components of this type may be used to implement a proximity detector, a light-based fingerprint sensor (e.g., when object  96  is the finger of a user), or other light-based sensor. If desired, light-based sensors such as these may be implemented by illuminating object  96  with light  24  from one or more of pixels  22  and/or light  98  from one or more supplemental light sources such as discrete light-emitting diodes  100 , while using light-detecting components  84  to gather reflected light from object  86 . 
     Control circuitry  16  may be used in controlling the emission of light from light sources such as pixels  22 , components  84 , and/or light sources  100  and may be used in processing corresponding detected light from components  84  (e.g., to generate a proximity sensor signal based on light reflected from object  96 , to generate a fingerprint reading based on light reflected from object  96 , to process a captured digital image of a far-field object that is captured using components  84 , etc.). 
     Cathode  46  is preferably formed from a conductive material that is sufficiently transparent to allow light  24  to be emitted from pixel  22 , as shown in  FIG. 3 . As an example, cathode  46  may be formed from a thin layer of metal (e.g., a metal alloy) such as silver magnesium silver (AgMg). Arrangements in which cathode  46  is formed from silver or other metals, wide bandgap semiconductors such as indium tin oxide that serve as transparent conductors, or other conductive materials may also be used, if desired. If the thickness of cathode  46  is sufficiently small (e.g., 20-30 nm or other suitable thickness for an illustrative AgMg cathode), cathode  46  will have a transmittance of 50% or more (as an example). 
     If desired, the transmittance of windows  90  can be enhanced relative to the transmittance of other portions of display  14  by modifying the portions of cathode  46  that overlap windows  90  and/or by modifying other portions of display  14  in windows  90 . 
     With one suitable arrangement, portions of cathode  46  may be selectively removed to form windows  90 . Windows  90  formed from cathode-free areas of display  14  may exhibit higher light transmission than areas of display  14  that are covered with cathode material. The cathode-free areas may therefore serve as effective light transmission windows for components  84 . 
       FIGS. 6, 7, 8, and 9  show how a lift-off technique may be used in forming regions of display  14  that do not include cathode material and which therefore exhibit enhanced transmittance for windows  90 . 
     As shown in  FIG. 6 , in a first process step, a passivation layer such as passivation layer  102  may be used to cover pixel definition layer  72 . Passivation layer  102  may be formed from an inorganic dielectric or other suitable masking material. The presence of passivation layer  102  may help protect pixel definition layer  72  from damage during wet etching operations. 
     As shown in  FIG. 7 , photoresist  104  (e.g., a photoimageable polymer) can then be deposited and patterned on a portion of display  14  that does not overlap one of anodes  42  or other light-blocking thin-film circuit structures. For example, photoresist  104  may be placed in a location between pixels  22  (i.e., between light-emitting diodes  26 ). 
     Organic emissive layer  44  and cathode layer  46  may then be deposited. The thickness of cathode layer  46  may be about 20-30 nm or other suitable thickness. 
     Due to the presence of photoresist  104 , portion  44 ′ of emissive material layer  44  and portion  46 ′ of blanket cathode layer  46  can be removed by a lift off process (e.g., photoresist  104 , portion  44 ′, and portion  46 ′ may be removed by exposure to liquid photoresist solvent). The removal of these structures creates an opening in cathode layer  46  that forms window  90  of  FIG. 9 . As shown in  FIG. 9 , one or more layers such as layer  106  (e.g., one or more layers such as layers  74 ,  76 , and  78  of  FIG. 3 ) may cover display  14  after formation of window  90 . Windows in display  14  such as window  90  of  FIG. 9  may be free of opaque structures such as opaque anode metal. 
     Multiple lift-off operations may be performed if it is desired to cap the maximum cathode layer film thickness that is removed in any one lift-off operation. The illustrative lift-off process of  FIGS. 6, 7, 8, and 9  uses a single lift-off operation. 
     If desired, patterned islands of photoresist such as photoresist  104  may be used in connection with dry processing techniques to pattern conductive layers such as cathode  46 . For example, these techniques may be to pattern transparent conductive material (AgMg or other thin metal layers, indium tin oxide, etc.) in touch sensors for displays. The touch sensors may be capacitive touch sensors that are integrated into displays and/or that are formed on separate touch panel substrates. Consider, as an example, capacitive touch sensor  108  of  FIG. 10 . Touch sensor circuitry  110  may process signals from transparent conductive capacitive touch sensor electrodes  112  to gather information on touch gestures and other touch input from a user of device  10 . Electrodes  112  may also serve as a part of the cathode for pixels  22  (i.e., cathode  46 ). 
     Electrodes  112  may have any suitable shapes (squares, diamonds, horizontal and/or vertical strips, etc.). To separate adjacent electrodes  112  from each other, gaps such as gap  114  may be formed. 
       FIGS. 11, 12, and 13  show how photoresist  104  may be used in forming gaps  114 . A cross-sectional side view of illustrative touch sensor  108  of  FIG. 10  taken along line  116  and viewed in direction  118  is shown in  FIG. 11 . In the arrangement of  FIG. 11 , pixel definition layer  72  has been deposited on thin-film transistor circuitry  48  on substrate  36 . If desired, layer  72  may be a patterned polymer layer on other types of substrate. The use of a display substrate in the example of  FIG. 11  is merely illustrative. 
       FIG. 12  is a cross-sectional side view of the structures of  FIG. 11  following deposition and patterning of photoresist  104  onto a region of pixel definition layer  72  between adjacent anodes  42 . 
     As shown in the cross-sectional side view of  FIG. 13 , after patterned photoresist  104  has been formed, emissive layer  44  and cathode layer  46  may be deposited. The shape of photoresist  104  prevents the material of cathode layer  46  from depositing in gaps  114 , thereby separating the cathode into cathode portions  46 - 1 ,  46 - 2 , and  46 - 3  (e.g., to form respective capacitive touch sensor electrodes  112  of  FIG. 10 ). If desired, the electrodes formed from cathode portions  46 - 1  and  46 - 2  may be used in handling current flowing through respective first and second sets of one or more light-emitting diodes  26  in corresponding pixels  22  for display  14 . Techniques of the type shown in  FIGS. 11, 12, and 13  may also be used to pattern touch sensor electrodes in touch sensor panels that do not contain any pixels. The example of  FIGS. 11, 12, and 13  in which conductive cathode layer structures are used both to form diode cathodes and capacitive touch sensor electrodes is presented as an example. 
     If desired, shadow masking techniques may be used to pattern layers of display  14  such as cathode layer  46  to form cathode-free regions for windows  90 . 
     An illustrative shadow mask with vertically oriented mask elements is shown in  FIG. 14 . Mask  122  may have a frame such as frame  124 . Vertical mask elements  126  may extend vertically (in the orientation of  FIG. 14 ) across frame  124 . Mask elements  126  may be high tension string-shaped elements (e.g., metal wire, carbon fibers coated with metal, etc.). Elements  126  that are formed from fibers may have diameters of about 3-10 microns (as an example). There may be hundreds of fibers or other elongated mask elements  126  in mask  122 . 
     Mask  122  may be used as a shadow mask when depositing cathode  46  (e.g., by physical vapor deposition). This creates vertical strips of cathode  46  separated by respective gaps  128  (e.g., narrow gaps having widths comparable to the horizontal dimensions of elements  126 ). 
     A second layer of cathode material may then be deposited through a second shadow mask such as shadow mask  130  of  FIG. 16 . Shadow mask  130  may have horizontal mask elements  134  (e.g., fibers such as metal wire, carbon-fiber strands coated with metal, etc.). Elements  134  may run perpendicular to elements  126 , so that following deposition of the second layer of cathode material, cathode  46  has a pattern of the type shown in  FIG. 17 . As shown in  FIG. 17 , cathode-free windows  90  have been created in an array of locations corresponding to the positions at which elements  126  and perpendicular elements  134  intersect and overlap. In these locations, cathode material from the first shadow mask deposition operation was blocked by elements  126  and cathode material from the second shadow mask deposition operation was blocked by elements  134 , resulting in an array of cathode-free areas. 
     In the illustrative configuration of  FIG. 18 , cathode shadow mask  136  has horizontal masking elements such as strip-shaped masking elements  140  that are supported by frame  138 . Mask  136  may be a fine metal mask that blocks cathode deposition along horizontally extending strips such as strip  142  of  FIG. 19 . Strips  142  create cathode-free areas where windows  90  may be formed on display  14 , but create a potential for electrical isolation between respective portions of cathode  46 . 
     To electrically short these horizontal strips of cathode  46  together, vertical metal lines such as lines  144  of  FIG. 19  (sometimes referred to as ELVSS lines) may be provided on display  14 . Lines  144  may be coupled to regions of cathode layer  46  using vias  146 , thereby forming a single electrically connected cathode for display  14 . Light transmitting windows  90  may be located in regions of display  14  that are free of cathode material such as location  90 - 1  (e.g., in an opening in an ELVSS line) and location  90 - 2 . Data lines D and other display routing lines may extend throughout display  14  in portions that do not overlap the light transmitting windows (e.g., data lines D may run vertically between respective ELVSS lines). 
     A cross-sectional side view of a portion of display  14  of  FIG. 19  taken along line  148  and viewed in direction  150  is shown in  FIG. 20 . Data lines D and ELVSS lines  144  may be formed from patterned portions of source-drain metal layer  52  or other suitable metal layer on display  14 . Layers  152  may include a substrate layer and thin-film layers of the type shown in  FIG. 3 . Dielectric layer  154  may be an inorganic and/or organic layer within the thin-film layers of display  14 . Openings in dielectric  154  may form vias  146  to short cathode layer  46  to lines  144  and thereby ensure that the cathode voltage distributed by the cathode in display  14  is uniform. If desired, an ELVSS metal ring may surround the periphery of display  14  to help enhance cathode voltage uniformity. 
     Laser processing techniques may be used to form some or all of windows  90 . In the example of  FIG. 21 , laser system  156  is producing laser light  158 . Light  158  may be divided into multiple parallel beams using an optical system formed from a grating that creates an M×N pattern of light beams and an associated focusing lens. Light  158  may also be generated in individual spots (e.g., by using a movable mirror, translation stages, and/or other systems for steering light  158  into desired areas on display  14 ). Light  158  may be ultraviolet light, visible light (e.g., green light at 532 nm in wavelength), or infrared light. Light  158  may be pulsed or may be continuous. Light  158  is preferably strongly absorbed by cathode  46  and minimally absorbed by intervening layers such as encapsulation layer  74 . Light  158  may be focused to a spot size of 1 to 250 square microns or other suitable size. 
     When exposed to light  158 , portion  160  of cathode  46  may be heated and otherwise modified so as to interact with adjacent materials (e.g., to form a light-transparent aggregate incorporating materials from layers such as emissive layer  44  and/or encapsulation layer  74 ). When converted to a transparent form in this way, portion  160  of cathode  46  can serve as a transparent layer within window  90 . If desired, light  158  may be applied with sufficient intensity (e.g., in energetic short pulses) to ablate material from display  14 , thereby creating a physical opening through layer  46  for window  90  ( FIG. 22 ). 
     If desired, antireflection structures may be provided over portions of display  14  to create light-transmitting windows  90 . This type of arrangement is shown in the cross-sectional side view of display  14  of  FIG. 23 . As shown in  FIG. 23 , display  14  may have thin-film transistor circuitry  48  on substrate  36 . Anodes  42 , pixel definition layer  72 , and cathode  46  may be formed on circuitry  48 . Encapsulation layer  74  may include layers such as organic capping layer CP and moisture barrier layers MB 1 , MB 2 , and MB 3 . Capping layer CP may be an organic layer having a thickness of about 50 nm. Moisture barrier layer MB 1  may be an inorganic dielectric layer such as a 1.5 micron layer of silicon nitride. Moisture barrier layer MB 2  may be a dielectric layer such as an 18 micron organic layer. Moisture barrier layer MB 3  may be an inorganic dielectric layer such as a 1.5 micron silicon nitride layer. 
     To form an antireflection structure that enhances transparency through display in window region  90 , dielectric antireflection layers may be selectively introduced above and below cathode  46  in window region  90 . For example, a 97.5 nm silicon oxide layer may be formed at location A above layer MB 3 , a 157.1 nm layer of silicon oxide may be formed at location B between layer CP and cathode  46 , and a 40.1 nm silicon nitride layer may be formed at location C between cathode layer  46  and emissive material  44 . 
     The total number of antireflection layers used for windows  90  and the thicknesses, locations, indices of refraction, and materials used in forming the additional antireflection layers for windows  90  may be adjusted to ensure visible light transparency or non-visible light transparency in a desired range of wavelengths. For example, three antireflection layers were incorporated into the window areas of display  14  of  FIG. 23 , but more than three layers or fewer than three layers (e.g., two or more layers, etc.) may be used. Antireflection layers may be single layers of material, may be multi-layer stacks of multiple materials, may include organic layer(s), may include inorganic layer(s), etc. A shadow mask may be used during physical vapor deposition operations to ensure that the antireflection films are deposited only in areas of display  14  that are associated with windows  90  and not in areas that overlap diodes  26 , thereby avoiding interference with the operation of diodes  26 . If desired, blanket films may be used in forming the antireflection layers at locations A, B, and C by adjusting the structures of diodes  26 . Moreover, different moisture barrier structures may be formed on display  14 . The configuration of  FIG. 23  is merely illustrative. 
     If desired, cathode  46  may be locally thinned in a portion of display  14  that overlaps windows  90 . Consider, as an example, an arrangement of the type shown in  FIG. 24 .  FIG. 24  is a top view of device  10  in an arrangement in which display  14  covers the front face of device  10 . Device  10  may be, for example, a cellular telephone or other portable device. An array of windows  90  may be formed in region  90 R of display  14  (e.g., using a rectangular array with rows and columns, using an array in which windows  90  are placed at horizontally staggered locations in successive rows as shown in  FIG. 24 , or using other suitable array patterns). This allows components  84  on device  82  to form a light-based fingerprint sensor (e.g., a button that senses the presence of a user&#39;s finger in region  90 R and that captures an image of the fingerprint of the user&#39;s finger using light sensors  84  that are aligned with respective windows  90 ). Region  90 R may contain pixels  22  for displaying a portion of the image that is displayed on display  14 . To ensure that these pixels receive a desired cathode voltage via cathode layer  46 , at least some of cathode layer  46  is preferably present in region  90 R. To help enhance light transmission in windows  90 , the thickness of cathode layer  46  may be reduced in region  90 R relative to the other portions of display  14 . As an example, the thickness of cathode  46  in the portions of display  14  that overlap pixels  22  but that do not overlap components  84  may be 20-30 nm, whereas the thickness of cathode  46  in the region of display  14  that overlaps the array of components  84  (and the pixels in that region) may be about 10 nm or less. The lowered thickness of cathode layer  46  will increase the resistivity of cathode layer  46  in region  90 R slightly, but voltage variations due to the IR drop across this portion of cathode layer  46  will generally be acceptable, because of the relatively small size of region  90 R and the position of region  90 R at the lower edge of device  10  where a horizontal metal power supply path may be used to distribute cathode voltage ELVSS to cathode layer  46 . 
     Any suitable cathode patterning technique may be used to form a cathode layer with multiple thicknesses. With one illustrative arrangement, one cathode deposition step is used to deposit a blanket film of cathode material (e.g., cathode layer  46 A of  FIG. 25 ) with a thickness T 1  over the surface of display  14 . Another cathode deposition step, which may be performed before or after the deposition of layer  46 A, may be used to deposit another cathode layer (e.g., cathode layer  46 B of  FIG. 26 ) with a thickness T 2 . During the deposition of cathode layer  46 B (e.g., using physical vapor deposition techniques), a shadow mask may be used to prevent cathode material from being deposited in region  90 R. A cross-sectional side view of the resulting cathode layer (cathode layer  46  of  FIG. 27 ) taken through region  90 R is shown in  FIG. 27 . As shown in  FIG. 27 , the thickness of cathode  46  is T 1 +T 2  in the portion of display  14  that is not overlapped by region  90 R and is thinner (having thickness T 1 ) in the portion of display  14  within region  90 R. The relatively small thickness of the cathode material in region  90 R may allow high transparency windows  90  to be formed in display  14  within region  90 R without requiring that windows  90  be free of cathode material. 
     A cross-sectional side view of a portion of region  90 R in display  14  that has an illustrative window  90  is shown in  FIG. 28 . Moisture barrier layer  74  of  FIG. 28  may be formed using organic capping layer CP and layers MB 1 , MB 2 , and MB 3  of  FIG. 23 . If desired, antireflection layers may be incorporated into window  90  of  FIG. 28  and other windows  90  in selectively thinned cathode region  90 R, as described in connection with  FIG. 23 . 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20160923
Publication Date: 20190813
Grant Date: 20190813
Priority Date: 20151020
Inventors: CHOI, MINHYUK
Visweswaran, Bhadrinarayana Lalgudi
CHEN, CHENG
LIN, CHIN-WEI
HO, MENG-HUAN
LIU, RUI
CHANG, SHIH CHANG
PARK, SOOJIN
Moh, Sarfaraz
LEE, JUNGMIN
ZHONG, JOHN Z.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01L31/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/1288", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/124", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L27/1218", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/451", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/411", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/0231", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/441", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10F55/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/60", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/60", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10D86/451", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K59/60", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/1201", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/121", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/8791", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 67543765