PATENT DOCUMENT

Publication Number: US-9059427-B2
Application Number: US-201213610757-A
Country: US
Kind Code: B2

Title: Device and method for top emitting AMOLED

Abstract:
Embodiments of the present disclosure relate to devices and methods for reducing the resistance level of top electrodes in top emission AMOLED displays. By way of example, one embodiment includes disposing a metal frame between the top electrode and an insulating layer. The present disclosure also relates to methods for making such a display in reduced number of process steps, including certain techniques for combining certain steps into one process step.

Claims:
What is claimed is: 
     
       1. A display comprising:
 a thin-film transistor (TFT) layer disposed over a backplane, wherein the TFT layer comprises one or more TFTs; 
 an interlayer dielectric (ILD) disposed over the TFT layer, wherein the ILD comprises one or more vias; 
 an insulating layer disposed over the ILD; 
 a pixel electrode disposed over a first portion of the insulating layer, wherein the pixel electrode is coupled to at least one of the one or more TFTs by at least one of the one or more vias in the ILD; 
 a metal frame layer disposed over a second portion of the insulating layer; 
 an organic light emitting diode (OLED) layer disposed over the pixel electrode; and 
 a top electrode disposed over the OLED layer and the metal frame layer, wherein the metal frame layer and the top electrode are conductively coupled together. 
 
     
     
       2. The display of  claim 1 , wherein the second portion of the insulating layer is thicker than the first portion of the insulating layer. 
     
     
       3. The display of  claim 1 , wherein the TFT layer comprises a circuit switching TFT and a driving TFT. 
     
     
       4. The display of  claim 1 , wherein insulating layer is annealed to cover an end of the pixel electrode. 
     
     
       5. The display of  claim 1 , comprising a gate insulating layer disposed between a gate of the one or more TFTs and a channel of the one or more TFTs. 
     
     
       6. The display of  claim 1 , wherein the metal frame forms a grid around one or more pixels in an array of pixels of the display. 
     
     
       7. An electronic device comprising:
 a display comprising:
 a pixel electrode disposed over a first portion of an insulating layer, wherein the pixel electrode is coupled to a thin-film transistor (TFT);
 a conductive layer disposed over a second portion of the insulating layer; 
 an organic light emitting diode (OLED) layer disposed over the pixel electrode; and 
 
 a top electrode disposed over the OLED layer and the conductive layer, wherein the conductive layer and the top electrode are conductively coupled together; 
 wherein the display comprises a plurality of pixels each having a pixel electrode, and 
 
 wherein the conductive layer forms a grid that surrounds each pixel electrode of the plurality of pixels. 
 
     
     
       8. The electronic device of  claim 7 , wherein the conductive layer extends along at least one edge of a pixel of the display. 
     
     
       9. The electronic device of  claim 7 , wherein the first portion of the insulating layer and the second portion of the insulating layer have different thicknesses. 
     
     
       10. A method, comprising:
 forming a thin-film transistor (TFT) layer over a backplane, wherein the TFT layer comprises one or more TFTs; 
 forming an interlayer dielectric (ILD) over the TFT layer; 
 forming one or more vias in the ILD; 
 forming an insulating layer over the ILD; 
 forming a pixel electrode over the insulating layer, wherein the pixel electrode is coupled to at least one of the one or more TFTs by at least one of the one or more vias in the ILD; 
 forming a metal frame over the insulating layer; 
 forming an organic light emitting diode (OLED) layer over the pixel electrode; 
 forming a top electrode over the metal frame and OLED layer; and 
 conductively coupling the metal frame layer and the top electrode. 
 
     
     
       11. The method of  claim 10 , comprising annealing the insulating layer to cause a portion of the insulating layer to flow over an edge of the pixel electrode. 
     
     
       12. The method of  claim 10 , comprising forming the insulating layer to have a first thickness between the metal frame and the ILD and a second thickness between the pixel electrode and the ILD, wherein the first thickness is greater than the second thickness. 
     
     
       13. The method of  claim 10 , wherein forming the insulating layer over the ILD comprises forming the insulating layer using a graytone mask so that the insulating layer comprises a varying thickness. 
     
     
       14. The method of  claim 10 , wherein the pixel electrode and the metal frame are formed together. 
     
     
       15. The method of  claim 10 , wherein the top electrode and the metal frame are conductively coupled together. 
     
     
       16. The method of  claim 10 , wherein forming the TFT comprises:
 forming an active layer; 
 doping the active layer to form a doped active layer; 
 forming a gate electrode over the doped active layer; and 
 doping the doped active layer with lightly doped drain (LDD) self-aligning doping. 
 
     
     
       17. The method of  claim 10 , wherein forming the TFT comprises:
 forming an active layer; 
 forming a gate electrode over the active layer; and 
 doping the active layer after the gate electrode is formed. 
 
     
     
       18. An array of pixels for a display comprising:
 a plurality of conductive frames, wherein each pixel in the array of pixels is surrounded by one of the plurality of conductive frames; 
 a plurality of top electrodes, wherein each pixel in the array of pixels comprises one of the plurality of top electrodes; and 
 wherein at least one of the plurality of top electrodes is conductively coupled to one of the plurality of conductive frames. 
 
     
     
       19. The array of pixels of  claim 18 , wherein at least one pixel in the array of pixels comprises an organic light emitting diode (OLED) layer. 
     
     
       20. The array of pixels of  claim 18 , wherein at least one pixel in the array of pixels comprises a thin-film transistor (TFT). 
     
     
       21. The array of pixels of  claim 18 , wherein at least one pixel in the array of pixels comprises a pixel electrode. 
     
     
       22. The array of pixels of  claim 18 , wherein the display comprises a top emission active matrix organic light emitting diode (AMOLED) display. 
     
     
       23. A display comprising:
 a thin-film transistor (TFT) disposed over a backplane; 
 a pixel electrode; 
 a top electrode; 
 an organic light emitting diode (OLED) layer disposed between the pixel electrode and the top electrode; and 
 a low-resistance metal member disposed beneath the top electrode, wherein the metal member and the top electrode are conductively coupled together.

Description:
BACKGROUND 
     The present disclosure relates generally to displays and, more particularly, a top emission active matrix organic light emitting diode (AMOLED) having a top electrode with reduced resistance, such that brightness and uniformity of the display is improved. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     Electronic displays, such as AMOLED displays are commonly used in electronic devices such as televisions, computers, phones, tablets, and the like. A common form an AMOLED display is a top-emission AMOLED display, in which light emitted from organic electroluminescent material is transmitted directly through the top of the display via a transparent top electrode. Top emission AMOLED displays have certain advantages, such as having high pixel aperture ratios and high brightness levels. However, in certain large sized top emission AMOLED displays, the internal resistance level of the top electrode may be higher than desired. This may negatively impact display quality such as brightness and display uniformity. 
     SUMMARY 
     A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     Embodiments of the present disclosure relate to devices and methods for reducing the resistance level of top electrodes in top emission AMOLED displays. By way of example, one embodiment includes disposing a metal frame between the top electrode and an insulating layer. The metal frame may be conductively coupled to the top electrode. The increased conductive area may help decrease the internal resistance of the top electrode. The present disclosure also relates to methods for making such a display in a reduced number of process steps, including certain techniques for combining certain steps into one process step. 
     Various refinements of the features noted above may be made in relation to various aspects of the present disclosure. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. The brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of embodiments of the present disclosure without limitation to the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a block diagram of exemplary components of an electronic device, in accordance with aspects of the present disclosure; 
         FIG. 2  is a front view of a handheld electronic device in accordance with aspects of the present disclosure; 
         FIG. 3  is a view of a computer in accordance with aspects of the present disclosure; 
         FIG. 4  is a cross-sectional view of a portion of a display, in accordance with aspects of the present disclosure; 
         FIG. 5  is a flowchart of a manufacturing process for making the display of 
         FIG. 4 , in accordance with aspects of the present disclosure; 
         FIGS. 6A-6C  illustrate portions of the manufacturing process described in the flowchart of  FIG. 5 , in accordance with aspects of the present disclosure; 
         FIG. 7  illustrates a method of forming an insulating layer of the display using a graytone technique, in accordance with aspects of the present disclosure; 
         FIG. 8A  illustrates portions of the manufacturing process described in the flowchart of  FIG. 5 , in accordance with aspects of the present disclosure; 
         FIG. 8B  is a top view of a pixel array of the display illustrated in  FIG. 8A , in accordance with aspects of the present disclosure; and 
         FIG. 9  illustrates portions of the manufacturing process described in the flowchart of  FIG. 5 , in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     As mentioned above, embodiments of the present disclosure relate to electronic displays, particularly top-emitting AMOLED displays, and electronic devices incorporating such displays which employ a device, method, or combination thereof for providing a simplified process and structure of the display. The result of which allows the display to be made in fewer steps, thereby streamlining the manufacturing process. Additionally, embodiments of the present disclosure include a metal frame conductively coupled to a top electrode, which reduces the resistance of the top electrode, improving the quality of display (e.g., brightness, uniformity). 
     With the foregoing in mind, a general description of suitable electronic devices that may employ electronic displays having top electrodes with decreased resistance is described below. In particular,  FIG. 1  is a block diagram depicting various components that may be present in an electronic device suitable for use with such a display.  FIGS. 2 and 3  respectively illustrate perspective and front views of a suitable electronic device, which may be, as illustrated, a notebook computer or a handheld electronic device. 
       FIG. 1  is a block diagram illustrating the components that may be present in such an electronic device  8  and which may allow the device  8  to function in accordance with the techniques discussed herein. Those of ordinary skill in the art will appreciate that the various functional blocks shown in  FIG. 1  may comprise hardware elements (including circuitry), software elements (including computer code stored on a computer-readable medium) or a combination of both hardware and software elements. It should further be noted that  FIG. 1  is merely one example of a particular implementation and is merely intended to illustrate the types of components that may be present in a device  8 . For example, in the presently illustrated embodiment, these components may include a display  10 , I/O ports  12 , input structures  14 , one or more processors  16 , a memory device  18 , a non-volatile storage  20 , expansion card(s)  22 , a networking device  24 , and a power source  26 . As will be appreciated, the overall quality of image data shown on the display  10  may be affected by the resistance of top electrodes of the display  10 . 
     With regard to each of these components, the display  10  may be used to display various images generated by the device  8 . In one embodiment, the display  10  may be an organic light emitting diode (OLED) display. Specifically, in certain embodiments, the display  10  may be an active matrix organic light emitting diode (AMOLED) display. Additionally, in certain embodiments of the electronic device  8 , the display  10  may be provided in conjunction with a touch-sensitive element, such as a touch screen, that may be used as part of the control interface for the device  8 . 
     The I/O ports  12  may include ports configured to connect to a variety of external devices, such as a power source, headset or headphones, or other electronic devices (e.g., such as handheld devices and/or computers, printers, projectors, external displays, modems, docking stations, and so forth). The I/O ports  12  may support any interface type, such as a universal serial bus (USB) port, a video port, a serial connection port, an IEEE-1394 port, an Ethernet or modem port, and/or an AC/DC power connection port. 
     The input structures  14  may include the various devices, circuitry, and pathways by which user input or feedback is provided to the processor  16 . Such input structures  14  may be configured to control a function of the device  8 , applications running on the device  8 , and/or any interfaces or devices connected to or used by the electronic device  8 . For example, the input structures  14  may allow a user to navigate a displayed user interface or application interface. Examples of the input structures  14  may include buttons, sliders, switches, control pads, keys, knobs, scroll wheels, keyboards, mice, touchpads, and so forth. 
     In certain embodiments, an input structure  14  and display  10  may be provided together, such as in the case of a touchscreen where a touch sensitive mechanism is provided in conjunction with the display  10 . In such embodiments, the user may select or interact with displayed interface elements via the touch sensitive mechanism. In this way, the displayed interface may provide interactive functionality, allowing a user to navigate the displayed interface by touching the display  10 . 
     User interaction with the input structures  14 , such as to interact with a user or application interface displayed on the display  10 , may generate electrical signals indicative of the user input. These input signals may be routed via suitable pathways, such as an input hub or bus, to the processor(s)  16  for further processing. 
     The processor(s)  16  may provide the processing capability to execute the operating system, programs, user and application interfaces, and any other functions of the electronic device  8 . The processor(s)  16  may include one or more microprocessors, such as one or more “general-purpose” microprocessors, one or more special-purpose microprocessors and/or ASICS, or some combination of such processing components. For example, the processor  16  may include one or more reduced instruction set (RISC) processors, as well as graphics processors, video processors, audio processors, and/or related chip sets. 
     The instructions or data to be processed by the processor(s)  16  may be stored in a computer-readable medium, such as a memory  18 . Such a memory  18  may be provided as a volatile memory, such as random access memory (RAM), and/or as a non-volatile memory, such as read-only memory (ROM). The memory  18  may store a variety of information and may be used for various purposes. For example, the memory  18  may store firmware for the electronic device  8  (e.g., such as a basic input/output instruction or operating system instructions), various programs, applications, or routines executed on the electronic device  8 , user interface functions, processor functions, and so forth. In addition, the memory  18  may be used for buffering or caching during operation of the electronic device  8 . 
     The components may further include other forms of computer-readable media, such as a non-volatile storage  20 , for persistent storage of data and/or instructions. The non-volatile storage  20  may include flash memory, a hard drive, or any other optical, magnetic, and/or solid-state storage media. The non-volatile storage  20  may be used to store firmware, data files, software, wireless connection information, and any other suitable data. 
     The embodiment illustrated in  FIG. 1  may also include one or more card or expansion slots. The card slots may be configured to receive an expansion card  22  that may be used to add functionality, such as additional memory, I/O functionality, or networking capability, to the electronic device  8 . Such an expansion card  22  may connect to the device through any type of suitable connector, and may be accessed internally or external to the housing of the electronic device  8 . For example, in one embodiment, the expansion card  22  may be a flash memory card, such as a SecureDigital (SD) card, mini- or microSD, CompactFlash card, Multimedia card (MMC), or the like. 
     The components depicted in  FIG. 1  also include a network device  24 , such as a network controller or a network interface card (NIC). In one embodiment, the network device  24  may be a wireless NIC providing wireless connectivity over any 802.11 standard or any other suitable wireless networking standard. The network device  24  may allow the electronic device  8  to communicate over a network, such as a Local Area Network (LAN), Wide Area Network (WAN), or the Internet. Further, the electronic device  8  may connect to and send or receive data with any device on the network, such as portable electronic devices, personal computers, printers, and so forth. Alternatively, in some embodiments, the electronic device  8  may not include a network device  24 . In such an embodiment, a NIC may be added as an expansion card  22  to provide similar networking capability as described above. 
     Further, the components may also include a power source  26 . In one embodiment, the power source  26  may be one or more batteries, such as a lithium-ion polymer battery or other type of suitable battery. The battery may be user-removable or may be secured within the housing of the electronic device  8 , and may be rechargeable. Additionally, the power source  26  may include AC power, such as provided by an electrical outlet, and the electronic device  8  may be connected to the power source  26  via a power adapter. This power adapter may also be used to recharge one or more batteries if present. 
     With the foregoing in mind,  FIG. 2  illustrates an electronic device  8  in the form of a handheld device  30 , here a cellular telephone. It should be noted that while the depicted handheld device  30  is provided in the context of a cellular telephone, other types of handheld devices (e.g., such as media players for playing music and/or video, personal data organizers, handheld game platforms, and/or combinations of such devices) may also be suitably provided as the electronic device  8 . Further, a suitable handheld device  30  may incorporate the functionality of one or more types of devices, such as a media player, a cellular phone, a gaming platform, a personal data organizer, and so forth. 
     For example, in the depicted embodiment, the handheld device  30  is in the form of a cellular telephone that may provide various additional functionalities (such as the ability to take pictures, record audio and/or video, listen to music, play games, and so forth). As discussed with respect to the general electronic device of  FIG. 1 , the handheld device  30  may allow a user to connect to and communicate through the Internet or through other networks, such as LANs or WANs. The handheld electronic device  30 , may also communicate with other devices using short-range connections, such as Bluetooth and near field communication. By way of example, the handheld device  30  may be a model of an iPod® or iPhone® available from Apple Inc. of Cupertino, Calif. 
     In the depicted embodiment, the handheld device  30  includes an enclosure or body that protects the interior components from physical damage and shields them from electromagnetic interference. The enclosure may be formed from any suitable material such as plastic, metal or a composite material and may allow certain frequencies of electromagnetic radiation to pass through to wireless communication circuitry within the handheld device  30  to facilitate wireless communication. 
     In the depicted embodiment, the enclosure includes user input structures  14  through which a user may interface with the device. Each user input structure  14  may be configured to help control a device function when actuated. For example, in a cellular telephone implementation, one or more of the input structures  14  may be configured to invoke a “home” screen or menu to be displayed, to toggle between a sleep and a wake mode, to silence a ringer for a cell phone application, to increase or decrease a volume output, and so forth. 
     In the depicted embodiment, the handheld device  30  includes a display  10  in the form of an organic light emitting diode (OLED) display  32 . The OLED  32  may be used to display a graphical user interface (GUI)  34  that allows a user to interact with the handheld device  30 . The GUI  34  may include various layers, windows, screens, templates, or other graphical elements that may be displayed in all, or a portion, of the display  10 . Generally, the GUI  34  may include graphical elements that represent applications and functions of the handheld device  30 . The graphical elements may include icons  36  and other images representing buttons, sliders, menu bars, and the like. The icons  36  may correspond to various applications of the handheld device  30  that may open upon selection of a respective icon  36 . Furthermore, selection of an icon  36  may lead to a hierarchical navigation process, such that selection of an icon  36  leads to a screen that includes one or more additional icons or other GUI elements. The icons  36  may be selected via a touch screen included in the display  10 , or may be selected by a user input structure  14 , such as a wheel or button. 
     The handheld electronic device  30  also may include various input and output (I/O) ports  12  that allow connection of the handheld device  30  to external devices. For example, one I/O port  12  may be a port that allows the transmission and reception of data or commands between the handheld electronic device  30  and another electronic device, such as a computer. Such an I/O port  12  may be a proprietary port from Apple Inc. or may be an open standard I/O port. 
     In addition to handheld devices  30 , such as the depicted cellular telephone of  FIG. 2 , an electronic device  8  may also take the form of a computer or other type of electronic device. Such computers may include computers that are generally portable (such as laptop, notebook, and tablet computers) as well as computers that are generally used in one place (such as conventional desktop computers, workstations and/or servers). In certain embodiments, the electronic device  8  in the form of a computer may be a model of a MacBook®, MacBook® Pro, MacBook Air®, iMac®, Mac® mini, Mac Pro®, or iPad® available from Apple Inc. By way of example, an electronic device  8  in the form of a laptop computer  50  is illustrated in  FIG. 3  in accordance with one embodiment. The depicted computer  50  includes a housing  52 , a display  10  (such as the depicted OLED  32 ), input structures  14 , and input/output ports  12 . 
     In one embodiment, the input structures  14  (such as a keyboard and/or touchpad) may be used to interact with the computer  50 , such as to start, control, or operate a GUI or applications running on the computer  50 . For example, a keyboard and/or touchpad may allow a user to navigate a user interface or application interface displayed on the display  10 . 
     As depicted, the electronic device  8  in the form of computer  50  may also include various input and output ports  12  to allow connection of additional devices. For example, the computer  50  may include an I/O port  12 , such as a USB port or other port, suitable for connecting to another electronic device, a projector, a supplemental display, and so forth. In addition, the computer  50  may include network connectivity, memory, and storage capabilities, as described with respect to  FIG. 1 . As a result, the computer  50  may store and execute a GUI and other applications. 
     It should be noted that the electronic device  8  having the presently disclosed display  10  may include devices other than those discussed as examples. Further, the electronic device may also include any device having a display  10  such as a television, a stand-alone display device, and so forth. 
       FIG. 4  illustrates a cross-sectional view of a pixel area  100  of the display  10 . The display  10  may be formed from several layers and components. Specifically, the display  10  includes a backplane  102 , and one or more thin-film transistors (TFTs)  104  disposed on the backplane  102 . In certain embodiments, such as the embodiment illustrated in  FIG. 4 , the display  10  may include a circuit switching TFT  106  as well as a driving TFT  108 . In other embodiments, the display  10  may include more than one circuit switching TFTs  106  and/or driving TFTs  108 . In certain embodiments, a gate insulator layer  110  is disposed over a source  111 , a channel  113 , and a drain  115  of the TFTs  104  and backplane  102  as shown. The gate insulator  110  insulates the channel  113  of each TFT  104  from a gate electrode  112  of each TFT  104 . 
     As illustrated, the gate electrode  112  of each TFT  104  is positioned over the gate insulator layer  110  of each TFT  104  to form the gates of the TFTs  104 . An interlayer dielectric (ILD)  114  is disposed over the gate electrodes  112  and the gate insulator layer  110 . One or more contacts  116  are disposed over the ILD  114  and coupled to the source  111  and drain  115  of the TFTs  104  via respective vias  118  extending through the ILD  114  and the gate insulator layer  110 . An insulating layer  120 , such as an organic planarization layer, is disposed on the ILD  114  and the contacts  116 . As illustrated, the insulating layer  120  may have different thicknesses at different areas. For example, in the illustrated embodiment, the insulating layer  120  is thicker near the switch TFT  106  than near the driving TFT  108 . Thus, the insulating layer  120  forms an upper portion  122  and a lower portion  124 . 
     A pixel electrode  126  is disposed along the lower portion  124  of the insulating layer  120  and adjacent to the upper portion  122  of the insulating layer  120 . As illustrated, the pixel electrode  126  may be conductively coupled to the driving TFT  108  by one of the contacts  116  and a lead  128 . An organic light emitting diode (OLED) layer  130  is disposed directly over the pixel electrode  126 . The OLED layer  130  may emit light in response to an electric current flowing through the OLED layer  130 . Specifically, the OLED layer  130  may emit light when there is current flowing between the pixel electrode  126  and a top electrode  132  (e.g., through the OLED layer  130 ). The top electrode  132  is generally disposed over the OLED layer  130  and the upper portion  122  of the insulating layer  120  that was not covered by the pixel electrode  126  or the OLED layer  130 . The top electrode  132  is generally made of a transparent material which transmits the light emitted from the OLED layer  130 . Thus, in the present embodiment, the display  10  may be a top emission display  10 . Additionally, a metal frame  134  is disposed between the upper portion  122  of the insulating layer  120  and the top electrode  132 . The metal frame  134 , which may be made of a low resistance material (e.g., substantially conductive material), may be conductively coupled to the top electrode  132  such that the resistance level of the top electrode  132  is decreased by the low resistance of the metal frame  134 . 
     As mentioned previously, the present disclosure also provides a simplified process of making the abovementioned display  10 .  FIG. 5  illustrates a flowchart of a manufacturing process for forming the display  10 .  FIGS. 6A-9  illustrate portions of the manufacturing process for forming the display  10 . Accordingly,  FIGS. 6A-9  will be discussed concurrently with  FIG. 5  to give visual descriptions of the manufacturing process described in the flowchart of  FIG. 5 . Referring now to  FIG. 5 , a manufacturing process  150  for forming the display  10  may include forming an active layer (block  152 ) over the backplane  102 . In certain embodiments, the gate insulator  110  may be formed over the active layer. 
     Accordingly,  FIG. 6A  illustrates an active layer  170  formed over the backplane  102 . As may be appreciated, in certain embodiments, the active layer  170  may be formed over the backplane  102  then etched to the illustrated configuration. Furthermore, the gate insulator  110  may be formed over the active layer  170  and the backplane  102 . The manufacturing process of  FIG. 5  also includes doping the active layer  170  (block  154 ) and then forming the gate electrode  112  (block  156 ) on the gate insulator  110  over the active layer  170 . In some embodiments, the active layer  170  may be doped (block  154 ) before the gate electrode  112  is formed (block  156 ). During such doping, the source  111 , the channel  113 , and the drain  115  of each TFT  104  are formed. Furthermore, after the gate electrode  112  is formed, a lightly doped drain (LDD) self aligning doping may be applied to the active layer  170  (block  158 ) to induce additional doping between the source and the channel, and between the drain and the channel, which may decrease TFT leakage current. In certain other embodiments, the gate electrode  112  may be formed and then the active layer  170  may be doped in the same step (block  160 ), using the gate electrode  112  to aid in a self align doping in order to form the source  111 , the channel  113 , and the drain  115  of each TFT  104 . In such an embodiment, the LDD doping (block  158 ) may be skipped due to the circuit design, yet the doping may still decrease TFT leakage current. Accordingly,  FIG. 6B  illustrates the doped active layer  170  (having the source  111 , the channel  113 , and the drain  115 ) and gate electrodes  112 . In certain embodiments, the active layer  170  may be doped with a P-type dopant, such as Boron, for example. Generally, these portions of the manufacturing process form the TFTs  104  in the display  10 , such as the circuit switching TFT  106  and the driving TFT. 
     Returning to  FIG. 5 , the manufacturing process  150  also includes forming the ILD  114  (block  162 ).  FIG. 6C  shows the ILD  114  formed over the gate insulator layer  110  and the gate electrodes  112 . The manufacturing process  150  of  FIG. 5  may further include forming the vias  118  through the ILD  114  and the contacts  116  over the ILD  114 , thereby establishing a conductive path between the contacts  116  and the TFTs  104  (block  164 ). Specifically, in certain embodiments, the contacts  116  may include source electrodes and drain electrodes which are coupled to respective sources  111  and drains  115  of the TFTs  104  via the vias  118  in the ILD  114 . The vias  118  and the contacts  116  are illustrated in  FIG. 6C  and are respectively coupled to the source  111  and the drain  115  of each TFT  104 . Additionally, the lead  128  may also be formed in conjunction with the vias  118  and the contacts  116 . As previously discussed, the lead  128  may be configured to conductively couple the driving TFT  108  to the pixel electrode  126 . 
     Further, the manufacturing process  150  of  FIG. 5  may include forming the insulating layer  120  (block  166 ). Specifically, the insulating layer  120  may be a multi-level insulating layer  120 , such as the insulating layer  120  illustrated in  FIG. 7 . In certain embodiments, the multi-level insulating layer  120  may be formed using a halftone or graytone mask, as further shown in  FIG. 7 . As may be appreciated, the insulating layer  120  may be made from photosensitive material that is removed though photolithography etching, in which designated portions of the material is removed when subjected to an intense light. In certain embodiments, the various thicknesses of the insulating layer  120  may be created in a single portion of the manufacturing process through the use of a halftone or graytone mask  178 . 
     By varying the transmittance of the mask  178 , the insulating layer  120  may be exposed to different light intensity, which may result in the removal of different amount of the insulating layer  120 . For example, in areas where the mask  178  is dark  180  such as in the upper portion  122 , less light or less intense light (e.g., low transmittance) reaches the insulating layer  120 , which allows more material to remain, and the insulating layer  120  may be thicker, as shown. Likewise, in areas where the mask  178  is lighter  182 , such as with the use of a gray tone, more light or more intense light (e.g., medium transmittance) may reach the insulating layer  120 , and more of the insulating layer  120  material may be removed through photolithography etching. Thus, the insulating layer  120  may be made thinner as less material remains, such as in the lower portion  124 . 
     Furthermore, the area where the mask  178  is generally transparent  184  allows most of the light through the mask  178  (e.g., high transmittance). This may remove all of the insulating layer  120 , as illustrated. Generally, if the mask  178  is darker, a greater amount of the insulating layer  120  may remain, and as the mask  178  gets light, less of the insulating layer  120  material remains. Thus, the different thickness levels of the insulating layer  120  may all be made in a single portion of the manufacturing process by using an appropriately designed halftone or graytone mask  178 . 
     Returning to  FIG. 5 , the manufacturing process  150  also includes forming the pixel electrode  126  and the metal frame  134  (block  168 ). Generally, the pixel electrode  126  and the metal frame  134  may be formed over certain portions of the insulating layer  120  during a single portion of the manufacturing process.  FIG. 8A  illustrates the display  10  after the pixel electrode  126  and the metal frame  134  are formed. Generally, the metal frame  134  may be formed on the upper portion  122  of the insulating layer  120  and the pixel electrode  126  may be formed on the lower portion  124  of the insulating layer  120 . Furthermore, the pixel electrode  126  may be conductively coupled to the lead  128 , thereby electrically connecting the pixel electrode  126  to the drain  115  of the driving TFT  108 . Forming the pixel electrode  126  and the metal frame  134  in the same portion of the manufacturing process may simplify the manufacturing process. 
     Additionally, in some embodiments, the pixel electrode  126  and/or the insulating layer  120  may be subject to annealing after the pixel electrode  126  is formed over the insulating layer  120 . In such an embodiment, the display  10  is heated to a high temperature. Accordingly, the insulating layer  120  may flow and cover the edge of the pixel electrode  126 . Specifically, the insulating layer  120  may flow into a gap  190  between the pixel electrode  126  and the insulating layer  120 . The resulting interaction between the insulating layer  120  and the pixel electrode  126  can be seen in  FIG. 4  in which the gap  190  of  FIG. 8A  is removed. This flow of the insulating layer  120  that occurs through annealing may aid to reduce current leakage from the pixel electrode  126 . 
     The metal frame  134  may form a rectangular structure around the pixel electrodes  126 . Accordingly,  FIG. 8B  illustrates a top view of a portion of an array  200  of pixels  202  in the display  10 . Each rectangle in the array  200  represents a pixel  202 . As may be appreciated, the display  10  may include a much larger number of pixels  202  than shown. As shown, each pixel  202  includes the pixel electrode  126  bound by the metal frame  134 , which forms a grid in the array  200 . 
     Returning to the flowchart of  FIG. 5 , the manufacturing process  150  further includes forming the OLED layer  130  and the top electrode  132  (block  169 ).  FIG. 9  shows that the OLED layer  130  is formed over the pixel electrode  126 , and the top electrode  132  is formed over the metal frame  134 , the insulating layer  120 , and the OLED layer  130  of the display  10 . The top electrode  132  is conductively coupled to the metal frame  134  to reduce the internal resistance of the top electrode  132 . 
     The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.

Metadata:
Filing Date: 20120911
Publication Date: 20150616
Grant Date: 20150616
Priority Date: 20120911
Inventors: Chen yu cheng
CHANG SHIH CHANG
Assignee: APPLE INC
CPC Classifications: [{"code": "H01L2251/5315", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L27/3248", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L51/5228", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K50/824", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K2102/3026", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/123", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K2102/3026", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/80522", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 50232346