Patent Publication Number: US-2023148207-A1

Title: Semiconductor device having flexible substrate

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Pat. Application Serial No. 17/077,233, filed on Oct. 22, 2020, which, in turn, is a continuation of U.S. Pat. Application Serial No. 16/752,779 (now U.S. Pat. No. 10,816,836), filed on Jan. 27, 2020, which, in turn, is a continuation of U.S. Pat. Application Serial No. 16/182,694 (now U.S. Pat. No. 10,578,898), filed on Nov. 7, 2018, which, in turn, is a continuation of U.S. Pat. Application Serial No. 15/968,820 (now U.S. Pat. No. 10,151,942), filed on May 2, 2018, which, in turn, is a continuation of U.S. Pat. Application Serial No. 15/296,111 (now U.S. Pat. No. 9,989,791), filed on Oct. 18, 2016. Further, this application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2016-034269, filed on Feb. 25, 2016, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     One embodiment of the present invention is related to a substrate structure of a display device having flexibility. 
     BACKGROUND 
     A display device is disclosed in which an electroluminescent element or liquid crystal element is used as a display element and a circuit for driving the display element is formed using a thin film transistor. One form of a display device is disclosed in which it is possible to bend and curve using a substrate having flexibility (for example, Japanese Laid Open Patent Publication No. 2015-169711). 
     A display device includes a circuit element such as a thin film transistor or capacitor element and the like above a substrate, and a wiring part connecting the circuit element. In addition, an organic insulation film and inorganic insulation film buried between these layers or an organic insulation film arranged above each electrode for example is arranged on roughly the entire surface of a substrate. Here, when a substrate having flexibility is curved, stress is applied to a thin film arranged above the substrate and defects such as cracks and the like are produced which is a problem. That is, even if a substrate has flexibility, since a thin film such as an inorganic insulation film and the like arranged thereupon does not always include the same flexibility, defects such as cracks and the like are produced in the thin film when the flexible substrate is bent. For example, when defects such as cracks and the like are produced in an inorganic insulation film above a flexible substrate, water infiltrates from the defects and causes degradation of a display element in a pixel region. 
     SUMMARY 
     According to one embodiment of the present invention, a display device is provided including a first substrate having flexibility, the first substrate including a curved part, an organic film covering a first surface of the first substrate and a second surface opposing the first surface in the curved part; and a pixel part and a drive circuit part arranged on the first surface. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a planar view diagram showing a structure of a display device related to the present embodiment; 
         FIG.  2    is a cross-sectional diagram showing a structure of a display device related to the present embodiment and shows a structure along the line A-B shown in  FIG.  1   ; 
         FIG.  3    is a cross-sectional diagram showing a structure of a display device related to the present embodiment and shows a structure along the line C-D shown in  FIG.  1   ; 
         FIG.  4    is a cross-sectional diagram showing a structure of a display device related to the present embodiment and shows a state where a substrate is curved in the structure along the line A-B shown in  FIG.  1   ; 
         FIG.  5    is a cross-sectional diagram showing a structure of a display device related to the present embodiment and shows a state where a substrate is curved in the structure along the line A-B shown in  FIG.  1   ; and 
         FIG.  6    is a cross-sectional diagram showing a structure of a display device related to the present embodiment and shows a structure along the line C-D shown in  FIG.  1   . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     One aim of an embodiment of the present invention is to control a drop in reliability due to defects such as cracks and the like even in the case where a substrate is curved in a display device using a substrate having flexibility. 
     The embodiments of the present invention are explained below while referring to the diagrams. However, it is possible to perform the present invention using various different forms, and the present invention should not be limited to the content described in the embodiments exemplified herein. Although the width, thickness and shape of each component are shown schematically compared to their actual form in order to better clarify explanation, the drawings are merely an example and should not limit an interpretation of the present invention. In addition, in the specification and each drawing, the same reference symbols are attached to similar elements and elements that have been mentioned in previous drawings, and therefore a detailed explanation may be omitted where appropriate. 
     In the present specification, in the case where certain parts or regions are given as [above (or below)] other parts or regions, as long as there is no particular limitation, these include parts which are not only directly above (or directly below) other parts or regions but also in an upper direction (or lower direction). That is, in the case where certain parts or regions are given as [above (or below)] other parts or regions, other structural elements may be included between other parts or regions in an upper direction (or lower direction). 
       FIG.  1    shows a structure of a display device  100  related to one embodiment of the present invention. In addition, in the display device  100  shown in  FIG.  1   , a cross-sectional structure along the line A-B is shown in  FIG.  2    and a cross-sectional structure along the line C-D is shown in  FIG.  3   . These diagrams are referred to in the explanation below. 
     The display device  100  includes a pixel part  104  arranged with a pixel  106  in a first surface  10  of a first substrate  102 . The display device  100  includes a drive circuit part for driving the pixel  106  in a region (periphery region) on the exterior of the pixel  104  in the first substrate  102 . The drive circuit includes a first drive circuit  108  which outputs a scanning signal and a second drive circuit  110  which outputs a video signal synchronized with the scanning signal. The second drive circuit 110is a driver IC for example mounted above the first substrate  102 . In addition, a terminal part  112  which is input with signals is arranged in a region on the exterior side of the first substrate  102 . The terminal part  112  includes a terminal which is input with a video signal. The terminal part  112  is electrically connected to a wiring substrate  118 . The driver IC described above, that is, the second driver circuit  110 , may be mounted above the wiring substrate  118 . 
     The first drive circuit  108 , the second drive circuit  110  and the pixel part  104  are connected via wiring. This connection region includes wiring formed from a conductive film and an insulation layer buried with this wiring. In the present specification, this connection region in a region between a pixel part and a drive circuit part is referred to as a wiring part. The display device  100  includes a first wiring part  114  between the pixel part  104  and the first drive circuit  108 , and a second wiring part  116  between the pixel part  104  and the second drive circuit  110 . 
     In the present embodiment, the first substrate  102  includes flexibility. A resin material is used for the first substrate  102  which includes flexibility. It is preferred that a high molecular material including recurring units of imide bonds is used as the resin material, polyimide for example. Specifically, a film substrate with polyimide molded into a sheet shape may be used as the first substrate  102 . In addition, as another form of the first substrate  102 , it is possible to use a thin metal substrate, a compound substrate in which a resin film is bonded to a thin metal substrate, or a compound substrate in which a resin film is bonded to a thin glass substrate. 
     The display device  100  is arranged with a sealing member  126   opposing the first substrate  102 . The sealing member  126  is also referred to as a second substrate opposing the first substrate  102 . The pixel part  104  is covered by the sealing member  126 . The sealing member  126  is formed from a cover film using a resin material or a sheet shaped component. 
     At least one part of the display device  100  includes a curved part  120 . That is, by providing the first substrate  102  with flexibility, it is possible to provide a bent state to at least a part of the display device  100 . The curved part  120  is a region in which the first substrate  102  bends or curves. When the first substrate  102  curves, parts which overlap with at least the curved part  120  within the pixel part, the drive circuit part and wiring part also curve together with the first substrate  102 . 
     The display device  100  is arranged with a support member  122  in a second surface  20  opposing the first surface  10  of the first substrate  102 . Although the support member  122  is arranged so as to cover roughly the entire surface of the first substrate  102 , a notch part  124  is also included in at least a part of the support member  122 . The support member  122  which is arranged close to the first substrate  102  essentially operates in the same way as increasing the thickness of a substrate. That is, the support member  122  controls bending of the first substrate  102 . On the other hand, since the thickness of the first substrate  102  is maintained by the notch part  124  of the support member  122 , the first substrate  102  may easily bend compared to regions where the support member  122  is arranged. A region of the first substrate  102  corresponding to the notch part  124  of the support member  122  becomes the curved part  120 . 
     The support member  122  is formed from the same resin material as the first substrate  102  or a component which is harder than the first substrate  102 . A resin substrate formed from a silicon resin and the like or a substrate such as an acrylic plate may be used as the support member  122 . Furthermore, in the present embodiment, the support member  122  is not an essential structural component but a structural component which can be used appropriately. However, as described above, by using the support member  122 , bending of the first substrate  102  is controlled, and by arranging the notch part  124 , it is possible to set the position of the curved part  120  of the display device  100 . 
     The notch part  124  of the support member  122  can be arranged at an arbitrary position and an arbitrary width.  FIG.  2    shows a form in which the notch part  124  of the display device  100  is arranged between the pixel part  104  and second drive circuit  110 . In other words, a region which overlaps with the second wiring part  116  of the display device  100  shown in  FIG.  2    becomes the curved part  120 . 
     As is shown in  FIG.  2    and  FIG.  3   , the display device  100  includes an organic film  128  in a region including the curved part  120 . The organic film  128  is arranged so as to cover an upper surface of the second wiring part  116  in the first surface of the first substrate  102 . In other words, the organic film  128  is arranged in a region between the pixel part  104  and the second drive circuit part  110 . The second wiring part  116  is covered and protected by the organic film  128 . The organic film  128  is also arranged on the side of the second surface  20  of the first substrate  102 . In addition, the organic film  128  is arranged to cover a region between the first surface  10  and second surface  20  of the first substrate  102 , that is, to cover a side surface part of the first substrate  102 . By arranging the organic film  128  in the first substrate  102  in this way, it is possible to use the organic film  128  as a protection film of the curved part  120 . For example, even in the case where stress is concentrated on one part of the curved part  120  and defects such as cracks occur in the second wiring part  116 , by arranging the organic film  128  continuously in the first surface  10  and second surface  20  of the first substrate  102 , it is possible to ensure that defects are not exposed to the air. 
       FIG.  4    shows a state of the display device  100  when the first substrate  102  is made to curve in the curved part  120 . The first substrate  102  curves so that the second drive circuit  110  is arranged on the rear surface side of the pixel part  104 . Bending stress is applied to the curved part  120  of the first substrate  102 . For example, bending stress is applied to the second wiring part  116  when the first substrate  102  is bent. That is, bending stress is applied to wiring included in the second wiring part  116  and an insulation layer buried with this wiring. In this case, although a metal film which forms the wiring is resistant to bending due to flexibility, defects such as cracks occur since at least an inorganic insulation layer among the insulation layers buried with the wiring is brittle. Defects such as cracks occurring in the second wiring part  116  proceed (grow) towards the pixel part  104 . Supposing that defects such as cracks in the second wiring part  116  are exposed to the air, water and the like infiltrates to the pixel part  104  from the cracks which affects reliability of the display device  100 . 
     The display device  100  related to the present embodiment is arranged with the organic film  128  covering the second wiring part  116 . As is shown in  FIG.  3    and  FIG.  4   , the organic film  128  is not arranged in the entire region of the display device  100  but in a part of the display device  100  which includes at least the curved part  120 . In this part, the organic film  128  is arranged continuously in the first surface  10 , second surface  20  and a side surface which intersects both the first surface  10  and second surface  20 . In other words, the organic film  128  is arranged across the entire periphery of one part of the display device  100  including at least the curved part  120 . Since the organic film  128   includes flexibility the same as the first substrate  102 , the organic film  128  has a high resistance to bending and it is difficult for defects such as cracks to occur. The organic film  128  is also arranged along a curved surface of the first substrate  102  in the curved part  120 . As a result, even if defects such as cracks occur in an insulation layer of the second wiring part  116 , such defects are not exposed to the exterior. In addition, the display device  100  includes a part (non-curved part) which is different to the curved part  120  and the non-curved part includes a region in which the organic film  128  is not formed. That is, it is not the case that the organic film  128  is arranged continuously in the entire periphery (that is, all of the first surface  10 , second surface  20  and side surface intersecting both the first surface  10  and second surface  20 ) of the display device  100 . 
     Furthermore, by using a cover film with low moisture permeability (high resistance to gas or high moisture resistance) as the organic film  128 , it is possible to maintain reliability of the display device  100  even if defects such as cracks occur in the second wiring part  116 . It is desirable that a material which has excellent non-moisture permeability properties (gas barrier properties) and mechanical characteristics (resistance to bending) be used as the organic film  128 . 
     It is preferred that polychloropyroxyline is used as the organic film  128  or the organic film  128  contains polychloropyroxyline. Various types of polychloropyroxyline are known that have different molecular structures such as parylene C, parylene N and parylene D. Although any one of parylene C, parylene N and parylene D may be used as the organic film  128 , among these it is preferred that parylene C is used since it is has the highest resistance to moisture. 
     A polychloropyroxyline thin film as the organic film  128  can be manufactured using a vacuum deposition method. A polychloropyroxyline thin film manufactured using a vacuum deposition method grows at molecular units. As a result, regardless of the shape of a deposition surface, it is possible to uniformly form a polychloropyroxyline thin film even in fine gaps. A polychloropyroxyline thin film can be formed using a vacuum deposition method with a thickness from a few micrometers to a few tens of micrometers and it is possible to exhibit sealing capabilities even at this thickness. Furthermore, when arranging the organic film  128  in the curved part  12 , a shadow mask including an aperture part corresponding to the curved part  120  of the first substrate  102  may be used when forming the polychloropyroxyline thin film. By using a shadow mask when forming a film, it is possible to selectively grow a polychloropyroxyline thin film in the curved part  120  without forming the organic film  128  in other regions such as the pixel part  104 . 
     In this way, according to one embodiment of the present invention, it is possible to prevent a drop in reliability due to defects such as cracks even in the case where a substrate is curved in a display device using a substrate having flexibility. 
     Next, details of the display device  100  related to the present embodiment are explained while referring to  FIG.  5    and  FIG.  6   . A cross-sectional structure corresponding to the line A-B shown in  FIG.  1    is shown in  FIG.  5    and a cross-sectional structure corresponding to the line C-D is shown in  FIG.  6   . Furthermore,  FIG.  5    shows a state in which the display device  100  is bent by the curved part  120  and  FIG.  6    shows a cross-sectional view of the curved part  120 . 
     In the display device  100 , the first substrate  102  is curved by the curved part  120  and the second drive circuit  110  and terminal part  112  are arranged on the rear surface side (second surface  20  side) of the pixel part  104 . The second wiring part  116  is arranged between the pixel part  104  and the second drive circuit  110 . The second wiring part  116  is arranged along a curved surface of the curved part  120 . 
     The pixel part  104  is arranged in the first surface  10  of the first substrate  102 . The example shown in  FIG.  5    shows a form in which a transistor  130 , light emitting element  132 , first capacitor element  134  and second capacitor element  136  are included in a pixel  106 . The light emitting element  132  is electrically connected with the transistor  130 . The first capacitor element  134  stores a gate voltage of the transistor  130  and the second capacitor element  136  is additionally arranged in order to adjust the amount of current flowing to the light emitting element  132 . Furthermore, the pixel  106  shown in  FIG.  5    is only an example and a pixel may be formed by a transistor and a light emitting element or by a transistor, light emitting element and a first capacitor element. Alternatively, elements other than a transistor, light emitting element and first capacitor element may also be added to form a pixel. 
     The transistor  130  includes a structure in which a semiconductor film  138 , gate insulation film  140  and gate electrode  142  are stacked. A source/ drain electrode  152  is arranged on an upper surface of the first insulation film  144 . The source/drain electrode  152  contacts a source region of the semiconductor film  138  or a region corresponding to a drain region for achieving electrical conduction. A second insulation film  146  is arranged as a planarized layer above the source/drain electrode  152 . In addition, the light emitting element  132  is arranged above the second insulation film  146 . The first insulation film  144  is formed using an inorganic insulation material and the second insulation film  145  is formed using an organic insulation material as the structure of the pixel  104 . The first capacitor element  134  is formed including a region in which the semiconductor film  138  and a first capacitor electrode  154  overlap using the gate insulation film  140  as a conductive film, and a region in which the source/drain electrode  152  and the first capacitor electrode  154  overlap using the gate insulation film  140  as a conductive film. The second capacitor element  136  is formed in a region in which the first electrode  158  and second capacitor electrode  156  overlap using a third insulation film  148  arranged above the second insulation film  146  as a conductive film. The third insulation film  148  is formed from an inorganic insulation material such as silicon oxide, silicon nitride or silicon oxynitride. 
     The light emitting element  132  includes a structure in which the first electrode  158  (pixel electrode) electrically connected with the transistor  140 , light emitting layer  160 , and second electrode  162  (common electrode) are stacked. The light emitting element  132  controls emitted light by controlling the potential between the first electrode  158  and second electrode  162 . The pixel part  104  includes a bank layer  164  which covers a periphery edge of the first electrode  158  and exposes an interior region. The light emitting layer  160  is arranged across the bank layer  164  from an upper surface of the first electrode  158 . The second electrode  162  covers an upper surface of the light emitting layer  160  and is arranged across roughly the entire surface of the pixel part  104 . 
     The light emitting layer  160  is a layer including an organic electroluminescence material as a light emitting material. The light emitting layer  160  is formed using a low molecular or high molecular organic material. In the case where a low molecular material is used for the light emitting layer  160 , in addition to the light emitting layer which includes an organic material with light emitting properties, one or a plurality of a hole injection layer, electron injection layer, hole transport layer and electron transport layer sandwiching the light emitting layer may also be included. Since the light emitting layer  160  degrades due to water, a fourth insulation film  150  is arranged above the second electrode  162 . The fourth insulation film  150  is arranged on roughly the entire surface of the pixel part  104 . 
     A single layer of or stacked layer body of an inorganic insulation film such as silicon nitride, silicon oxide or aluminum oxide is used as the fourth insulation film  150 . Furthermore, an insulation film comprised from a stacked layer body of an organic insulation film and inorganic insulation film may be arranged above the fourth insulation film  150 . A sealing member  126  is arranged on an upper surface side of the fourth insulation film  150 .  FIG.  5    shows the case where the sealing member  126  is a sheet shaped substrate. In this case, the sealing member  126  is fixed to the first substrate  102  by a sealing material  172  which encloses the outer periphery of the pixel part  104 . Gaps are present between the fourth insulation film  150  and sealing member  126  and these gaps may be filled with a filler material. A resin material is used for the filler material. 
     An aperture part  168  which splits the second insulation film  146  and bank layer  164  is included between an end part (region contacting the sealing material  172 ) of the pixel part  104  and a pixel  106 . The third insulation film  148  formed from an inorganic material and the second electrode  162  are arranged so as to cover a side surface and bottom surface of the aperture part  168 . In other words, a region is included in which the third insulation film  148  and second electrode  162  contact in the aperture part  168 . By adopting this type of structure, the light emitting layer  160  is essentially enclosed and sealed by the third insulation film  148  and second electrode  162 . That is, by adopting this type of sealing structure, water and the like is prevented from passing through the second insulation film  146  which is formed from an organic resin material and the bank layer  164 , and infiltrating the light emitting layer  160 . In addition, the pixel part  104  is arranged with a connection part  170  in which the second electrode  162  is electrically connected with lower layer wiring. 
     The first substrate  102  is arranged with first wiring  166  from the pixel part  104  to the second drive circuit  110 . A region in which the first wiring  166  is arranged is also a region corresponding to the curved part  120 . For example, the first wiring  166  is formed in the same layer as the source/drain electrode  152 . For example, the first wiring  166  includes a structure in which an aluminum film (Al) and a metal film with a high melting point such as titanium (Ti) or molybdenum (Mo) are stacked above and below the aluminum film. The third insulation film  148  and fourth insulation film  150  arranged extending from the pixel part  104  are stacked above the first wiring  166 . Although the curved part  120  exists in a region on the outer side of the sealing member  126 , by arranging the third insulation film  148  and fourth insulation film  150 , the first wiring  166  is protected by these insulation films and is never exposed directly to the air. 
     The organic film  128  is arranged in the curved part  120 . That is, the organic film  128  is arranged in a region on the outer side of the sealing member  126 . The organic film  128  is preferred to be arranged as the outermost layer in the curved part  120 .  FIG.  5    includes a structure in which the gate insulation film  140 , first insulation film  144 , first wiring  166 , third insulation film  148  and fourth insulation film  150  are stacked above the first substrate  102  in the curved part  120 . Furthermore, the organic film  128  is arranged above the fourth insulation film  150 . 
     When the first substrate  102  is curved, bending stress is applied to the second wiring part  116 . At this time, since the first wiring  166  is a metal film, it is possible to be deform in response to bending of the substrate which is flexible. However, since the third insulation film  148   and fourth insulation film  150  are formed from an inorganic material, when the first substrate  102  is curved, defects such as cracks occur due to brittleness. When defects such as cracks which occur in these inorganic insulation films spread towards the pixel part  104 , water and the like in the air infiltrates the pixel part  104  from these defects. For example, when the first substrate  102  is repeatedly bent by the curved part  120 , stress is repeatedly applied to the second wiring part  116  and thereby defects such as cracks occurring in an inorganic insulation film grow. 
     As described previously, a water blocking structure is adopted for the display device  100  in which the third insulation film  148  and second electrode  162  are in close contact in the aperture part  168 . As a result, the display device  100  can to a certain extent prevent water from infiltrating to the light emitting layer  160 . However, a contact hole which electrically connects the first electrode  158  and the source/drain electrode  152 , and a contact hole which electrically connects the source/drain electrode  152  and the semiconductor film  138  are arranged in a pixel  106 . These contact holes are formed in the first insulation film  144  or second insulation film  146 . Water and the like which infiltrates from the exterior to the pixel part  104  can form a path which infiltrates to a region in which the light emitting layer  160  is arranged via a contact hole which passes through the first insulation film  144  or second insulation film  146 . Due to this, degradation of a light emitting element  132  in the pixel part  104  occurs after manufacture of the display device  100  which leads to a decrease in display quality. 
     However, in the present embodiment, the organic film  128  covers the top of the fourth insulation film  150  in the curved part  120 . As a result, it is possible to prevent defective parts from being exposed to the air even when these defects such as cracks occur in either the gate insulation film  140 , first insulation film  144 , third insulation film  148  and fourth insulation film  150  which are inorganic insulation films. 
     Defects such as cracks which occur in the second wiring part  116  also easily occur in an end part of the first substrate  102  where stress is easily concentrated. However, as is shown in  FIG.  6   , by arranging the organic film  128  to cover the entire periphery of the first substrate  102 , it is possible to ensure that defects are not exposed to the air even when defects such as cracks occur in an end part of the first substrate  102 . 
     In addition, as is shown in  FIG.  6   , the second wiring  116  is mixed with a region in which the gate insulation film  140 , first insulation film  144 , first wiring  166 , third insulation film  148  and fourth insulation film  150  are stacked above the first substrate  102  from the first substrate  102  side, and a region in which the gate insulation film  140 , first insulation film  144 , third insulation film  148  and fourth insulation film  150  are stacked. Stress is concentrated in a boundary between these two regions when the first substrate  102  bends due to a difference in their stacked structures. For example, it is possible that stress is concentrated in the third insulation film  148  which covers the first wiring  166 . Even in this case, by arranging the organic film  128  in an outermost layer, it is possible to prevent defective parts from being exposed to the air even when defects occur in the third insulation film  148 . 
      Although a form is shown in the present embodiment in which the curved part  120  of the display device  100  is arranged in a region overlapping the second wiring part  116 , the present invention is not limited to this structure. For example, the curved part  120  may also be arranged to overlap the first wiring substrate  114 . In addition, the curved part  120  may also be arranged to intersect the pixel part  104 . In either case, by arranging the organic film  128  as an outermost layer in the curved part  120  where the first substrate  102  bends, it is possible to increase resistance to problems that can occur due to bending of the first substrate  102 . 
     Although a form is shown in the present embodiment in which the light emitting element  132  is arranged in the pixel part  104  as a display element, the light emitting element can also be applied to display devices formed with a pixel using other display elements. For example, the structure shown in the present embodiment can also be applied to a liquid crystal display device using liquid crystal elements as a display element. 
      Based on the display device described in the embodiments of the present invention, a person ordinarily skilled in the art could appropriately perform an addition or removal of structural components or design modification or an addition of processes or an omission or change in conditions which are included in the scope of the present invention as long as they do not depart from the subject matter of the present invention. 
     In addition, other effects that are different from those provided by the embodiments described above are obvious from the description in the specification, and effects that could be easily conceived of by a person ordinarily skilled in the art should be interpreted as also being provided by the present invention.