PATENT DOCUMENT

Publication Number: US-9818976-B2
Application Number: US-201514705364-A
Country: US
Kind Code: B2

Title: Encapsulation layers with improved reliability

Abstract:
An electronic device may include a display having an array of organic light-emitting diodes formed on a substrate. An encapsulation layer may be formed over the array of organic light-emitting diodes to protect the organic light-emitting diodes from moisture and other contaminants. The encapsulation layer may include a transparent sheet of material interposed between upper and lower inorganic films. The reliability of the encapsulation layer is increased by dividing one or both of the inorganic films into multiple sub-layers. The sub-layers may have different densities and may be deposited in sequential steps. Additional moisture protection may be provided by forming a conformal thin-film coating over the organic light-emitting diodes. The conformal thin-film coating may be an aluminum oxide layer that is formed using atomic layer deposition techniques.

Claims:
What is claimed is: 
     
       1. An encapsulation layer for encapsulating organic light-emitting diodes, comprising:
 a first inorganic layer having multiple sub-layers; 
 a second inorganic layer; and 
 a transparent dielectric layer interposed between the first and second inorganic layers, wherein the transparent dielectric layer comprises a layer of polymer. 
 
     
     
       2. The encapsulation layer defined in  claim 1  wherein the first and second inorganic layers comprise silicon nitride. 
     
     
       3. The encapsulation layer defined in  claim 2  wherein the sub-layers have different respective densities. 
     
     
       4. The encapsulation layer defined in  claim 2  wherein the sub-layers have different respective indices of refraction. 
     
     
       5. The encapsulation layer defined in  claim 1  further comprising a conformal thin-film coating formed on a surface of the organic light-emitting diodes. 
     
     
       6. The encapsulation layer defined in  claim 5  wherein the conformal thin-film coating comprises aluminum oxide. 
     
     
       7. The encapsulation layer defined in  claim 1  further comprising a conformal thin-film coating interposed between the second inorganic layer and the transparent dielectric layer. 
     
     
       8. The encapsulation layer defined in  claim 7  wherein the conformal thin-film coating comprises aluminum oxide. 
     
     
       9. An encapsulation layer for encapsulating organic light-emitting diodes, comprising:
 a first inorganic layer having multiple sub-layers; 
 a second inorganic layer; and 
 a transparent dielectric layer interposed between the first and second inorganic layers, wherein the transparent dielectric layer comprises a layer of glass. 
 
     
     
       10. A method for forming an encapsulation layer for encapsulating organic light-emitting diodes, comprising:
 with deposition equipment, depositing a first inorganic layer over the organic light-emitting diodes; 
 depositing a transparent dielectric layer over the first inorganic layer; and 
 with the deposition equipment, depositing a second inorganic layer over the transparent dielectric layer, where depositing the second inorganic layer comprises depositing a first sub-layer of inorganic material over the transparent dielectric layer and depositing a second sub-layer of inorganic material over the first sub-layer of inorganic material. 
 
     
     
       11. The method defined in  claim 10  further comprising:
 with atomic layer deposition equipment, forming a conformal film over the organic light-emitting diodes. 
 
     
     
       12. The method defined in  claim 10  wherein the deposition equipment comprises plasma-enhanced chemical vapor deposition equipment. 
     
     
       13. The method defined in  claim 10  wherein a refractive index of the first sub-layer of inorganic material is different than a refractive index of the second sub-layer of inorganic material. 
     
     
       14. The method defined in  claim 10  wherein the first and second sub-layers of inorganic material comprise silicon nitride and wherein depositing the second sub-layer of inorganic material comprises depositing the second sub-layer of inorganic material after depositing the first sub-layer of inorganic material. 
     
     
       15. A display, comprising:
 a substrate; 
 an array of organic light-emitting diodes formed on the substrate; and 
 an encapsulation layer formed over the organic light-emitting diodes, wherein the encapsulation layer comprises a transparent sheet of material interposed between first and second inorganic films, wherein at least the first inorganic film comprises first and second sub-layers. 
 
     
     
       16. The display defined in  claim 15  wherein the first and second sub-layers have different indices of refraction. 
     
     
       17. The display defined in  claim 15  wherein the transparent sheet of material comprises a transparent polymer sheet and wherein the first and second inorganic films comprise silicon nitride. 
     
     
       18. The display defined in  claim 15  further comprising a conformal thin-film interposed between the transparent sheet of material and the organic light-emitting diodes. 
     
     
       19. The display defined in  claim 18  wherein the conformal thin-film comprises aluminum oxide.

Description:
This application claims the benefit of provisional patent application No. 61/992,727, filed May 13, 2014, 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. For example, cellular telephones and portable computers often include displays for presenting information to a user. 
     Displays such as organic light-emitting diode displays often use an encapsulation layer to encapsulate the organic light-emitting diodes. However, conventional encapsulation layers may be unreliable. If care is not taken, moisture may allowed to penetrate the encapsulation layer which can in turn damage the organic light-emitting diodes. 
     It would therefore be desirable to be able to provide improved displays for electronic devices. 
     SUMMARY 
     An electronic device may be provided with a display. The display may be formed from an array of organic light-emitting diode display pixels. Each display pixel may have an organic light-emitting diode having an anode and a cathode. An associated pixel circuit in each display pixel may be used to control the light-emitting diode of that display pixel. 
     An encapsulation layer may be formed over the array of organic light-emitting diodes to protect the organic light-emitting diodes from moisture and other contaminants. The encapsulation layer may include a transparent sheet of material interposed between upper and lower inorganic films. The transparent sheet of material may be a layer of glass, polymer, or other suitable transparent dielectric material. 
     The reliability of the encapsulation layer is increased by dividing one or both of the inorganic films on the transparent sheet into multiple sub-layers. The sub-layers may have different densities and may be deposited in sequential steps. By depositing sub-layers of inorganic material in the encapsulation layer in sequential steps, an interface may be formed between the sub-layers. The presence of the interface may improve the moisture barrier properties of the encapsulation layer. For example, any pinholes, cracks, or other defects in a lower thin-film sub-layer may be covered by an upper thin-film sub-layer layer. 
     Additional moisture protection may be provided by forming a conformal thin-film coating over the organic light-emitting diodes. The conformal thin-film coating may be an aluminum oxide layer that is formed using atomic layer deposition techniques. 
     Further features, their nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device such as a laptop computer with a display in accordance with an embodiment of the present invention. 
         FIG. 2  is a perspective view of an illustrative electronic device such as a handheld electronic device with a display in accordance with an embodiment of the present invention. 
         FIG. 3  is a perspective view of an illustrative electronic device such as a tablet computer with a display in accordance with an embodiment of the present invention. 
         FIG. 4  is a perspective view of an illustrative electronic device such as a computer display with display structures in accordance with an embodiment of the present invention. 
         FIG. 5  is a perspective view of an illustrative display in accordance with an embodiment of the present invention. 
         FIG. 6  is a cross-sectional side view of an electronic device with a display in accordance with an embodiment of the present invention. 
         FIG. 7  is a cross-sectional side view of an illustrative bottom emission organic light-emitting diode display in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional side view of an illustrative top emission organic light-emitting diode display with a reflection suppression layer formed from a circular polarizer in accordance with an embodiment of the present invention. 
         FIGS. 9-12  show cross-sectional side views of illustrative encapsulation layers that may be use to encapsulate organic light-emitting diodes in accordance with embodiments of the present invention. 
         FIG. 13  is a flow chart of illustrative steps involved in forming an encapsulation layer for encapsulating organic light-emitting diodes in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may include displays. The displays may be used to display images to a user. Illustrative electronic devices that may be provided with displays are shown in  FIGS. 1, 2, 3, and 4 . 
       FIG. 1  shows how electronic device  10  may have the shape of a laptop computer having upper housing  12 A and lower housing  12 B with components such as keyboard  16  and touchpad  18 . Device  10  may have hinge structures  20  that allow upper housing  12 A to rotate in directions  22  about rotational axis  24  relative to lower housing  12 B. Display  14  may be mounted in upper housing  12 A. Upper housing  12 A, which may sometimes referred to as a display housing or lid, may be placed in a closed position by rotating upper housing  12 A towards lower housing  12 B about rotational axis  24 . 
       FIG. 2  shows how electronic device  10  may be a handheld device such as a cellular telephone, music player, gaming device, navigation unit, or other compact device. In this type of configuration for device  10 , housing  12  may have opposing front and rear surfaces. Display  14  may be mounted on a front face of housing  12 . Display  14  may, if desired, have openings for components such as button  26 . Openings may also be formed in display  14  to accommodate a speaker port (see, e.g., speaker port  28  of  FIG. 2 ). 
       FIG. 3  shows how electronic device  10  may be a tablet computer. In electronic device  10  of  FIG. 3 , housing  12  may have opposing planar front and rear surfaces. Display  14  may be mounted on the front surface of housing  12 . As shown in  FIG. 3 , display  14  may have an opening to accommodate button  26  (as an example). 
       FIG. 4  shows how electronic device  10  may be a computer display or a computer that has been integrated into a computer display. With this type of arrangement, housing  12  for device  10  may be mounted on a support structure such as stand  27 . Display  14  may be mounted on a front face of housing  12 . 
     The illustrative configurations for device  10  that are shown in  FIGS. 1, 2, 3, and 4  are merely illustrative. In general, electronic device  10  may be a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     Housing  12  of device  10 , which is sometimes referred to as a case, may be formed of materials such as plastic, glass, ceramics, carbon-fiber composites and other fiber-based composites, metal (e.g., machined aluminum, stainless steel, or other metals), other materials, or a combination of these materials. Device  10  may be formed using a unibody construction in which most or all of housing  12  is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements or other internal housing structures). 
     Display  14  may be a touch sensitive display that includes a touch sensor or may be insensitive to touch. Touch sensors for display  14  may be formed from an array of capacitive touch sensor electrodes, a resistive touch array, touch sensor structures based on acoustic touch, optical touch, or force-based touch technologies, or other suitable touch sensor components. 
     Display  14  for device  10  includes display pixels formed from organic light-emitting diode components or other suitable display pixel structures. 
     A display cover layer may cover the surface of display  14  or a display layer such as a color filter layer, polarizer layer, polymer film, or other portion of a display may be used as the outermost (or nearly outermost) layer in display  14 . The outermost display layer may be formed from a transparent glass sheet, a clear plastic layer, or other transparent member. 
     A perspective view of an illustrative display is shown in  FIG. 5 . As shown in  FIG. 5 , display  14  may have an array of display pixels  30 . Control signals may be supplied to display pixels  30  on vertical control lines  32  and horizontal control lines  34 . By controlling display pixels  30 , control circuitry in device  10  may display images for a user of device  10  on display  14 . 
     Display pixels  30  may be arranged in a rectangular array in the center of display  14 . During use of device  10 , display pixels  30  form images, so display pixels  30  in display  14  are sometimes said to form an active area AA of display  14 . Active area AA may be bounded by dashed line rectangle  36  in the example of  FIG. 5 . An inactive area IA may border some or all of the edges of active area AA. For example, a rectangular ring-shaped inactive area IA may form a border that surrounds active area AA, as shown in  FIG. 5 . Display  14  typically includes signal lines (e.g., metal traces) and other support circuitry for operating display  14  (i.e., circuitry for driving signals into display pixels  30 ) in inactive border region IA. The support circuitry in inactive area IA does not produce light for images on display  14 . 
     To prevent structures in inactive area IA from being visible to a user of device  10 , it may be desirable to cover areas IA with an opaque mask. The opaque mask may have the shape of a rectangular ring (i.e., the same shape as inactive area IA in  FIG. 5 ) or may have other suitable shapes. Opaque masking material such as organic materials and/or inorganic materials may be used in forming an opaque masking layer in area IA. Examples of opaque masking material that may be used in forming an opaque masking layer include black chrome (chrome oxide), other metal oxides, black ink, ink of other colors (e.g., white ink, red ink, etc.), polymers, metals, oxides, nanotubes such as carbon nanotubes, black silicon (e.g., black silicon processed using a laser), nitrides, and other opaque materials. Materials such as opaque ink may be deposited using pad printing, screen printing, ink-jet printing, and other deposition techniques. Materials such as metal oxides and other inorganic materials may be deposited using vacuum coating (e.g., physical vapor deposition using an evaporator or sputtering tool). Shadow masking and/or photolithography may be used in patterning deposited masking material. If desired, opaque masking material may also be deposited using lamination techniques. 
       FIG. 6  is a cross-sectional side view of an illustrative electronic device with a display. As shown in  FIG. 6 , device  10  may include housing  12 . Display  14  may be mounted in housing  12 . Display  14  may include an array of display pixels  30  in display structures  38 . Display structures  38  may be based on organic light-emitting diode display structures including layers such as a substrate layer, an encapsulation layer, and an organic light-emitting diode layer containing organic light-emitting diode display pixels  30 . In the example of  FIG. 6 , organic light-emitting diode display layers  38  are attached to the lower surface of an external display layer such as display cover layer  40 . Display cover layer  40  may be formed from a layer of transparent glass, a clear plastic layer, or other transparent member (e.g., one or more clear sheets of material). Display cover layer  40  may help to protect underlying display structures such as organic light-emitting diode display structures  38 . In inactive area IA, display structures  38  (e.g., the organic light-emitting diode layer of structures  38 ) may contain metal lines and other support circuitry  42 . An opaque masking layer may be formed in inactive area IA to block the support circuitry from view. Display pixels  30  may form a rectangular array in active area AA. 
     Device  10  may have internal components  43  mounted on substrate  44 . Components  43  may include integrated circuits such as microprocessors, application-specific integrated circuits, microcontrollers, and other processing circuitry. Components  43  may also include storage circuitry such as memory circuits and other memory devices. Input-output circuitry such as sensors, buttons, and other input-output circuitry may also be included in components  43 . Substrates such as substrate  44  may be used to interconnect the circuitry of components  43 . Substrate  44  may be a rigid printed circuit board (e.g., a fiberglass-filled epoxy board) or a flexible printed circuit (e.g., a printed circuit formed from a flexible substrate such as polyimide or other polymer layer). 
     Display  14  may be based on organic light-emitting diode display pixels or display pixels formed using other display technologies. Configurations for display  14  in which display pixels  30  are formed from organic light-emitting diodes and in which display  14  is an organic light-emitting diode display may sometimes be described herein as an example. This is, however, merely illustrative. Device  10  may, in general, include any suitable type of display. 
     A cross-sectional side view of display  14  in a configuration using a bottom emission organic light-emitting diode display configuration is shown in  FIG. 7 . As shown in  FIG. 7 , bottom emission organic light-emitting diode display  14  may have a substrate layer such as substrate  48 . Substrate  48  may include one or more transparent layers such as one or more glass layers, one or more plastic layers, or other transparent substrate layers. As an example, substrate  48  may be formed from a layer of clear glass. 
     Organic light-emitting diode layer  50  may be formed on substrate  48  (i.e., on the surface of substrate  48  that is the lower or innermost of the two opposing surfaces of substrate  48  in the orientation of  FIG. 7 ). During operation, light from display pixels  30  in organic light-emitting diode layer  50  may pass through substrate  48  (i.e., through substrate layer  48  on which the organic light-emitting diodes, thin-film-transistors, and other organic light-emitting diode circuitry have been formed) in direction Z, as illustrated by light ray  54 . 
     In active area AA, organic light-emitting diode layer  50  includes organic light-emitting diode structures  60  (e.g., anode electrode structures, cathode electrode structures, emissive layers, signal lines, thin-film transistors, etc.). For example, active area organic light-emitting diode structures  60  in organic light-emitting diode layer  50  may include metal structures  62  (e.g., anode and cathode structures and metal traces for signal lines). The light produced by the organic light-emitting diode structures in active area AA of organic light-emitting diode layer  50  such as light ray  54  produces an image for a viewer such as viewer  56  who is viewing display  14  in direction  58 . 
     In inactive area IA, organic light-emitting diode layer  50  includes inactive area organic light-emitting diode display structures such as inactive area structures  64 . Inactive area structures  64  may include support circuitry such as metal traces for signal lines, thin-film circuitry such as driver circuitry, and other circuitry that does not produce light  54  for viewer  56 . For example, inactive area structures  64  of organic light-emitting diode layer  50  may include metal structures such as metal traces for signal lines  66 . 
     To suppress ambient light reflections from metal structures  62  (e.g., from reflective cathode structures in bottom emission display  14 ), display  14  may be provided with a reflection suppressing layer such as circular polarizer layer  46 . Circular polarizer  46  may, if desired, overlap with inactive area IA, as shown in  FIG. 7 . 
     Encapsulant layer  52  may be formed on organic light-emitting diode layer  50  (i.e., on the lower surface of layer  50  in the orientation of  FIG. 7 ). Encapsulant layer  52  may be used to encapsulate the organic light-emitting diode structures of organic light-emitting diode layer  50 . Encapsulant layer  52  may be formed from a glass or plastic layer, may be formed from a glass or plastic layer coated with a thin film such as an inorganic coating, may be formed from a layer of metal (e.g., a metal plate, metal can, or metal foil), or may be formed from a metal coating on a substrate layer such as a glass layer or plastic layer (as examples). If desired, a coating of water-absorbing and/or oxygen absorbing material may be formed on a glass layer or other encapsulant layer to help sequester oxygen and water. As illustrated by dashed line  70 , encapsulant layer  52  may contain two or more sublayers (e.g., a glass plate and a coating, a metal layer on a glass or polymer substrate or other dielectric layer, etc.). 
     A cross-sectional side view of display  14  in a configuration using a top emission organic light-emitting diode display configuration is shown in  FIG. 8 . As shown in  FIG. 8 , top emission organic light-emitting diode display  14  may have a substrate layer such as substrate  90 . Substrate  90  may include one or more transparent layers such as one or more glass layers, one or more plastic layers, or other transparent substrate layers. As an example, substrate  90  may be formed from a layer of glass. 
     Organic light-emitting diode layer  72  may be formed on substrate  90  (i.e., on the upper surface of substrate  90  in the orientation of  FIG. 8 ). During operation, light from display pixels  30  in organic light-emitting diode layer  72  may pass upwards in Z, as illustrated by light ray  88 . 
     In active area AA, organic light-emitting diode layer  72  includes organic light-emitting diode structures  94  (e.g., anode electrode structures, cathode electrode structures, emissive layers, signal lines, thin-film transistors, etc.). For example, active area organic light-emitting diode structures  94  in organic light-emitting diode structures layer  72  may include reflective structures  80  (e.g., anode and cathode structures and metal traces for signal lines such as a reflective anode formed from a metal such as aluminum or a metal such as aluminum that has been covered with a coating such as indium tin oxide). The light produced by the organic light-emitting diode structures in active area AA of organic light-emitting diode layer  72  such as light ray  88  produces an image for a viewer such as viewer  56  who is viewing display  14  in direction  58 . 
     In inactive area IA, organic light-emitting diode layer  72  includes inactive area organic light-emitting diode display structures such as inactive area structures  86 . Inactive area structures  86  may include supporting circuitry such as metal traces for signal lines, and other circuitry that does not produce light  88  for viewer  56  but that supports the operation of the display pixels in active area AA. For example, inactive area structures  86  of organic light-emitting diode layer  72  may include metal structures such as metal traces for signal lines  82 . 
     To suppress ambient light reflections from metal structures  80  (e.g., from reflective anode structures in top emission display  14 ), display  14  may be provided with a reflection suppressing layer (reflection suppression layer) such as circular polarizer layer  78 . Circular polarizer  78  may, if desired, overlap inactive area IA and may cover support circuitry  86 , as shown in  FIG. 8 . 
     Encapsulant layer  74  may be formed on layer  72  under polarizer  78  and may be used to encapsulate the organic light-emitting diode structures of organic light-emitting diode layer  72 . Encapsulant layer  74  may be formed from a transparent material such as a clear glass layer, a clear layer of polymer, a clear inorganic thin-film, or other clear materials. As an example, layer  74  may be formed from a sheet of transparent glass. As illustrated by dashed line  92 , encapsulant layer  74  may contain two or more sublayers. For example, encapsulant layer  74  may be formed from a glass plate that is covered with an inorganic thin-film coating. 
       FIG. 9  is a cross-sectional side view of an illustrative encapsulation layer such as encapsulation layer  74  that may be formed over an organic light-emitting diode layer such as organic light-emitting diode layer  72 . As shown in  FIG. 9 , encapsulation layer  74  may include a polymer layer such as transparent polymer substrate layer  102  (e.g., a layer of epoxy, polyimide, polyethylene, polypropylene, or other polymeric film) interposed between first and second inorganic films such as inorganic thin-films  100  and  104 . Inorganic films  100  and  104  may be formed from an inorganic material such as silicon nitride (Si 3 N 4  or SiN x ), silicon dioxide, other inorganic materials, a combination of any two or more of these materials, etc. 
     Polymer substrate layer  102  may have a thickness T 2  of about 20 microns, whereas thicknesses T 1  and T 3  of inorganic films  100  and  104  may each be equal to about 1 micron (as an example). This is, however, merely illustrative. If desired, layers  100 ,  102 , and  104  may have other thicknesses. For example, layers  100  and  104  may each be between 0.5 and 1 microns, between 0.5 and 2 microns, less than 2 microns, more than 2 microns, etc. Layer  102  may be 15 microns, 15-20 microns, 18-22 microns, more than 20 microns, less than 20 microns, etc. 
     Inorganic thin-films  100  and  104  may be deposited using plasma-enhanced chemical vapor deposition (PECVD) techniques (e.g., low temperature PECVD processing techniques) or other suitable thin-film deposition techniques. 
     The reliability of encapsulation layer  74  may be enhanced by forming inorganic film layer  100  and/or inorganic film layer  104  as multi-layer films rather than single-layer films. Forming one or both of inorganic film layers  100  and  104  as multi-layer films may improve the moisture barrier properties of the inorganic films. 
     As shown in  FIG. 9 , inorganic film  100  may be formed with multiple thin-film sub-layers layers such as thin-film sub-layers  106  and  108 . Thin-film sub-layers  106  and  108  may have equal thicknesses or non-equal thicknesses. As an example, thin-film sub-layers  106  and  108  may each have a thickness of about 0.5 microns. This is, however, merely illustrative. If desired, thin-film layers  106  and  108  may have different respective thicknesses. 
     Thin-film sub-layers  106  and  108  may be deposited in separate steps. For example, thin-film layer  108  may be deposited over polymer substrate layer  102  in a first step, and thin-film layer  106  may be deposited over thin-film layer  108  in a second step. By depositing layers  108  and  106  in separate steps, an interface such as interface  130  may be formed between sub-layers  106  and  108 . The presence of interface  130  may improve the moisture barrier properties of inorganic film  100 . For example, any pinholes, cracks, or other defects in thin-film layer  108  may be covered by thin-film layer  106 . In this way, moisture or other contaminants may be prevented from penetrating from the upper surface of inorganic film  100  to the lower surface of inorganic film  100  through a single pinhole. 
     The example of  FIG. 9  in which inorganic film  100  includes two sub-layers is merely illustrative. If desired, inorganic film  100  may include three sub-layers deposited in three separate steps, four sub-layers deposited in four separate steps, etc. In general, inorganic film  100  may include N sub-layers (e.g., sub-layers such as sub-layers  106  and  108 ) deposited in N separate steps. Arrangements in which inorganic film  100  includes two sub-layers  106  and  108  are sometimes described herein as an example. 
     The moisture barrier properties of inorganic film  100  may also be enhanced by adjusting the density of one or more of sub-layers  106  and  108 . For example, the density of sub-layer  106  and/or sub-layer  108  may correspond to a refractive index of 1.8 to 1.85, 1.85 to 1.9, 1.9 to 1.95, 1.95 to 2.0, higher than 2.0, lower than 2.0, etc. Using higher density silicon nitride materials (e.g., silicon nitride materials with higher refractive indices) to form sub-layer  106  and/or sub-layer  108  may improve the moisture barrier properties of inorganic film  100 . 
     In one suitable arrangement, both sub-layer  106  and sub-layer  108  may be formed from a relatively high density silicon nitride material (e.g., a silicon nitride material with a refractive index of 1.85-2.0). In another suitable arrangement, one sub-layer (e.g., sub-layer  108 ) may be formed with a relatively low density silicon nitride material (e.g., a silicon nitride material with a refractive index of 1.8-1.85) while the other sub-layer (e.g., sub-layer  106 ) may be formed with a relatively high density silicon nitride material (e.g., a silicon nitride material with a refractive index of 1.85-2.0). This is, however, merely illustrative. If desired, both sub-layers  106  and  108  may be formed with relatively low density silicon nitride material (e.g., a silicon nitride material with a refractive index of 1.8-1.85). 
     The example of  FIG. 9  in which upper inorganic film  100  is a multi-layer inorganic film while lower inorganic film  104  is a single-layer inorganic film is merely illustrative. If desired, lower inorganic film  104  may be a multi-layer film. For example, as shown in  FIG. 10 , lower inorganic layer  104  may include multiple sub-layers such as thin-film sub-layers  110  and  112 . As with the example of  FIG. 9 , thin-film sub-layers  110  and  112  may be deposited in separate steps such that any pinholes or defects in one sub-layer are covered by the other sub-layer. Thin-film sub-layers  110  and  112  may have equal densities or may have different densities (as described in connection with layers  106  and  108 ). 
     If desired, additional moisture barrier layers may be incorporated into encapsulation layer  74 . For example, as shown in  FIG. 11 , a moisture barrier layer such as moisture barrier layer  114  may be incorporated into encapsulation layer  74 . Moisture barrier layer  114  may be a thin-film (e.g., a thin-film of aluminum oxide or other material) deposited using atomic layer deposition (ALD) techniques (as an example). Using atomic layer deposition techniques to deposit moisture barrier layer  114  over organic light-emitting diode layer  72  may result in a thin conformal coating that fills any voids, crevices, or air gaps present on the surface of organic light-emitting diode layer  72 . This type of conformal thin-film coating may effectively moisture-seal organic light-emitting diode layer  72  to prevent moisture and other contaminants from penetrating organic light-emitting diode layer  72 . 
     The example of  FIG. 11  in which conformal coating  114  (sometimes referred to as ALD film  114 ) is deposited on the surface of organic light-emitting diode layer  72  is merely illustrative. If desired, conformal coating  114  may be deposited over lower inorganic film  104 . For example, as shown in  FIG. 12 , conformal coating  114  may be interposed between inorganic film  104  and polymer substrate layer  102 . If desired, more than one conformal coating  114  may be incorporated into or formed on encapsulation layer  74 . 
       FIG. 13  is a flow chart of illustrative steps involved in forming an encapsulation layer (e.g., an encapsulation layer of the type shown in  FIG. 11 ). 
     At step  200 , an organic light-emitting diode layer such as layer  72  of  FIG. 8  may be deposited on a substrate such as substrate  90 . 
     At step  204 , a conformal thin-film such as a thin-film of aluminum oxide may be formed on the organic light-emitting diode layer using atomic layer deposition equipment. This may include, for example, depositing first and second chemicals (precursors) in sequential steps onto the surface of the organic light-emitting diode layer (e.g., in a vacuum). The thin-film resulting from the atomic layer deposition process may form a conformal coating over the organic light-emitting diode layer that fills any voids, crevices, or air gaps present on the surface of the organic light-emitting diode layer. 
     At step  206 , plasma-enhanced chemical vapor deposition equipment may be used to deposit a thin-film of inorganic material such as silicon nitride over the conformal thin-film and the organic light-emitting diode layer. 
     At step  208 , a polymer substrate layer may be formed over the inorganic material (e.g., using screen printing tools or other suitable equipment). 
     At step  210 , plasma-enhanced chemical vapor deposition equipment may be used to deposit a first thin-film sub-layer of inorganic material such as silicon nitride over the polymer substrate layer. The first thin-film sub-layer of inorganic material may, if desired, have a refractive index of 1.8 (as an example). 
     At step  212 , plasma-enhanced chemical vapor deposition equipment may be used to deposit a second thin-film sub-layer of inorganic material such as silicon nitride over the first thin-film sub-layer. The second thin-film sub-layer of inorganic material may, if desired, have a refractive index of 1.85 (as an example). 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20150506
Publication Date: 20171114
Grant Date: 20171114
Priority Date: 20140513
Inventors: POON STEPHEN S.
YANG CHIH JEN
BOESCH DAMIEN S.
VISWESWARAN BHADRINARAYANA L.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01L51/56", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L51/5253", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L27/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K71/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K50/844", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K59/8731", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 54539237