Patent Publication Number: US-2021193694-A9

Title: Array substrate and display panel comprising barrier as doping mask overlapping gate electrode

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This patent application is a National Stage Entry of PCT/CN2017/115424 filed on Dec. 11, 2017, which claims the benefit and priority of Chinese Patent Application No. 201710426034.0 filed on Jun. 8, 2017, the disclosures of which are incorporated herein by reference in their entirety as part of the present application. 
    
    
     BACKGROUND 
     The present disclosure relates to the field of display technology. More specifically, it relates to an array substrate, a method for fabricating the same, a display panel, and a display device. 
     Thin film transistors (TFTs) are widely used in display technology. However, a crystal-damaged region caused by doping may occur in the TFT. This damaged region tends to cause hot carrier stress. For example, when electrons accelerate from the source region to the drain region, they may penetrate the gate insulating layer or the metal oxide semiconductor (MOS) interface. In addition, hot carrier stress may reduce the electron mobility and may also increase the off-current. This will have an adverse effect on the TFT. 
     An aging process has been proposed to reduce the leakage current in the TFT. However, the aging process will bring about new adverse effects. For example, it will lead to burns, new bright spots, abnormal display and so on. 
     Another known solution is to use a lightly doped drain region (LDD) to reduce the leakage current in the TFT. However, the process of the LDD in prior art is a complicated process and is also difficult to design. 
     BRIEF DESCRIPTION 
     A first aspect of the present disclosure provides an array substrate. The array substrate includes a channel region, source/drain regions positioned on both sides of the channel region, and a lightly doped drain region between the channel region and the source/drain regions, a gate electrode and a first electrode positioned on the active layer, a first insulating layer positioned on the gate electrode and the first electrode, a barrier and a second electrode positioned on the first insulating layer, wherein a projection of the second electrode on the substrate at least partially overlaps a projection of the first electrode on the substrate, wherein a projection of the barrier on the substrate covers a projection of the lightly doped drain region on the substrate, wherein the projection of the barrier on the substrate does not overlap projections of the source/drain regions on the substrate, and wherein the barrier and the second electrode are disposed in the same layer. 
     In an embodiment, the barrier has an opening, wherein a projection of the opening on the substrate at least partially overlaps the projection of the gate electrode on the substrate. 
     In an embodiment, a width of the lightly doped drain region ranges from about 0.5 μm to 1 μm. 
     In an embodiment, the array substrate further includes a second insulating layer disposed between the active layer and the gate electrode, a via penetrating through the first insulating layer and the second insulating layer, source/drain electrodes positioned on the first insulating layer, the source/drain electrodes being in contact with the source/drain regions via the via. 
     In an embodiment, a doping concentration of the source/drain region is greater than a doping concentration of the lightly doped drain region, and wherein the doping concentration of the source/drain region ranges from about 4.5×10 15  to about 6×10 15  ions/cm 3  and the doping concentration of the lightly doped drain region ranges from about 5×10 12  to about 4.5×10 15  ions/cm 3 . 
     A second aspect of the present disclosure provides a display panel. The display panel includes the array substrate as described above. 
     A third aspect of the present disclosure provides a display device. The display device includes the display panel as described above. 
     A fourth aspect of the present disclosure provides a method for fabricating an array substrate. The method for fabricating an array substrate includes forming an active layer on a substrate, forming a gate electrode and a first electrode on the active layer, forming a first insulating layer on the gate electrode and the first electrode, forming a barrier material layer on the first insulating layer, performing one patterning process on the barrier material layer to form a barrier and a second electrode, wherein a projection of the second electrode on the substrate at least partially overlaps a projection of the first electrode on the substrate, wherein a projection of a portion of the barrier extending outward from a side of the gate electrode on the substrate is within a projection of a portion of the active layer extending outward from a side of the active layer on the substrate, performing a first doping on the active layer by using the barrier as a mask to form source/drain regions on both sides of the channel region of the active layer and a lightly doped drain region between the channel region and the source/drain regions. 
     In an embodiment, the barrier has an opening, and wherein a projection of the opening on the substrate at least partially overlaps a projection of the gate electrode on the substrate. 
     In an embodiment, the width of the lightly doped drain region ranges from about 0.5 μm to about 1 μm. 
     In an embodiment, a doping energy of the first doping is about 30 Kev˜40 Kev. 
     In an embodiment, a doping concentration of the source/drain regions is greater than a doping concentration of the lightly doped drain region, and wherein the doping concentration of the source/drain regions is about 4.5×10 15  to about 6×10 15  ions/cm 3 , and the doping concentration of the lightly doped drain (LDD) region is about 5×10 12  to about 4.5×10 15  ions/cm 3 . 
     In an embodiment, a conductivity type of the channel region is N-type, and wherein a conductivity type of the lightly doped drain region and a conductivity type of doping regions of the source/drain regions are P type. 
     In an embodiment, the method for fabricating the array substrate further includes before forming the gate electrode and the first electrode, forming a second insulating layer on the active layer, after forming the source/drain regions, forming a via penetrating through the first insulating layer and the second insulating layer, and forming source/drain electrodes on the first insulating layer, wherein the source/drain electrodes are in contact with the source/drain regions through the via. 
     In an embodiment, forming the gate electrode and the first electrode includes forming a gate electrode material layer on the second insulating layer, patterning the gate electrode material layer to form the gate electrode and the first electrode. 
     In an embodiment, the fabricating method of the array substrate further includes, after forming the gate electrode and the first electrode, doping the active layer by using the gate electrode as a mask to define a channel region of the active layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to more clearly explain the technical solutions of the embodiments of the present disclosure, the following will briefly explain the drawings of the embodiments. It should be understood that the drawings described below merely relate to some embodiments of the present disclosure but are not intended to limit the present disclosure, in which: 
         FIG. 1A  is a schematic view of an array substrate according to an embodiment of the present disclosure; 
         FIG. 1B  is a schematic view of an array substrate according to an embodiment of the present disclosure; 
         FIG. 2  is a schematic view of an array substrate according to an embodiment of the present disclosure; 
         FIG. 3  is a schematic view of an array substrate according to an embodiment of the present disclosure; 
         FIG. 4  is a schematic flowchart of a method for fabricating an array substrate according to an embodiment of the present disclosure; 
         FIG. 5  is a schematic flowchart of a method for fabricating an array substrate according to an embodiment of the present disclosure; 
         FIGS. 6A-6F  are process flow diagrams of a method for fabricating an array substrate according to an embodiment of the present disclosure; 
         FIG. 7  is a schematic view of a display panel according to an embodiment of the present disclosure; and 
         FIG. 8  is a schematic view of a display device according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In order that technical solutions and advantages of embodiments of the present disclosure will become more apparent, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are a part of the embodiments of the present disclosure, but not all embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without the need for creative work fall within the scope of the present disclosure. 
     When describing elements of the disclosure and their embodiments, the articles “a,” “an,” “this” and “the” are intended to indicate the presence of one or more elements. Words “contain”, “comprise”, “have” and “with” are intended to be inclusive and mean that additional elements other than the listed elements may be present. As used herein and in the appended claims, the singular form of a word includes the plural, and vice versa, unless the context clearly dictates otherwise. Thus, the references “a”, “an”, and “the” are generally inclusive of the plurals of the respective terms. Similarly, the words “comprise”, “comprises”, and “comprising” are to be interpreted inclusively rather than exclusively. Likewise, the terms “include”, “including” and “or” should all be construed to be inclusive, unless such a construction is clearly prohibited from the context. Where used herein the term “examples,” particularly when followed by a listing of terms is merely exemplary and illustrative, and should not be deemed to be exclusive or comprehensive. 
     For the purpose of the following description of the surface, as in the direction in which they are marked, the terms “upper”, “lower”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom” and their derivatives shall relate to the disclosure. The terms “overlying”, “on top of”, “positioned on”, or “positioned on top of” means that a first element, such as a first structure, is present on a second element, such as a second structure, wherein an intermediate element such as an interface structure may exist between the first element and the second element. The term “contact” means connecting a first element, such as a first structure, and a second element, such as a second structure, with or without other elements at the interface of the two elements. 
     Embodiments of the present disclosure provide an array substrate including an active layer positioned on a substrate, the active layer including a channel region, source/drain regions positioned on both sides of the channel region, and a lightly doped drain region between the channel region and the source/drain regions, a gate electrode and a first electrode positioned on the active layer, a first insulating layer positioned on the gate electrode and the first electrode, a barrier provided on the first insulating layer and the second electrode, wherein a projection of the second electrode on the substrate at least partially overlaps a projection of the first electrode on the substrate, a projection of the barrier on the substrate covers a projection of the lightly doped drain region on the substrate, the projection of the barrier on the substrate does not overlay with a projection of the source/drain regions on the substrate, and wherein the barrier and the second electrode layer are disposed in the same layer. Here, being disposed in the same layer means being formed by the same film. 
     The embodiments of the present disclosure will be further described below with reference to the accompanying drawings. 
       FIG. 1A  is a schematic view of an array substrate according to an embodiment of the present disclosure. As shown in  FIG. 1A , an array substrate according to an embodiment of the present disclosure includes an active layer  11  positioned on a substrate  10 , the active layer  11  including a channel region  11 C, source/drain regions  11 SD positioned on sides of the channel region  11 C and a lightly doped drain region  11 L disposed between the channel region  11 C and the source/drain regions  11 SD, a gate electrode  121  and a first electrode  122  positioned on the active layer  11 , a first insulating layer  13  provided on the gate electrode  121  and the first electrode  122 , a barrier  141  and a second electrode  142  provided on the first insulating layer  13 . A projection of the second electrode  142  on the substrate  10  at least partially overlaps a projection of the first electrode  122  on the substrate  10 . A projection of the barrier  141  on the substrate  10  covers a projection of the lightly doped drain region  11 L on the substrate  10 , and the projection of the barrier  141  on the substrate  10  does not overlap a projection of the source/drain regions  11 SD on the substrate  10  do not overlap (in other words, the edge of the barrier  141  away from the gate electrode  121  is aligned with the edge of the lightly doped drain region  11 L away from the gate electrode  121 ). The barrier  141  and the second electrode  142  are disposed in the same layer and have the same material. Herein, the “the edge of the barrier away from the gate electrode is aligned with the edge of the lightly doped drain region away from the gate electrode” refers to the outer boundary of the projection of the barrier on the substrate and the outer boundary of the projection of the lightly doped drain region substantially overlap. 
     The first electrode and the second electrode may form a capacitance to maintain a stable voltage. For example, when being used in an OLED structure, since the capacitance including the first electrode and the second electrode can maintain the stability of the voltage of the driving transistor in one cycle, the current of the OLED in one cycle is also stabilized. Therefore, OLED&#39;s luminous uniformity and stability can be ensured. 
     In  FIG. 1A , a lightly doped drain region  11 L is exemplified as being provided on both sides of the channel region. However, the position of the lightly doped drain region can be set according to actual needs. For example, as shown in  FIG. 1B , the lightly doped drain region may be located only on one side of the channel region.  FIG. 1B  shows the case where a region of the source/drain regions far from the first electrode is used as a drain region, and a lightly doped drain can be provided only on the side of the channel region far from the first electrode. Of course, when a region of the source/drain regions close to the first electrode is used as a drain region, a lightly doped drain region may also be provided only on the side of the channel region near the first electrode. 
     By the lightly doped drain region, the leakage current of the thin film transistor can be reduced. Due to the same layer arrangement of the second electrode and the barrier, the two can be formed using a single patterning process. In this way, when forming the second electrode and the barrier, only one mask is used, the fabricating process of the array substrate thus can be simplified. The production yield can be improved and the cost can also be saved. 
       FIG. 2  is a schematic view of an array substrate according to an embodiment of the present disclosure. As shown in  FIG. 2 , the barrier may have an opening P. A projection of the opening P on the substrate  10  at least partially overlaps a projection of the gate electrode  121  on the substrate  10 . By providing such an opening in the barrier, it is possible to prevent or reduce the parasitic capacitance that may be generated between the barrier and the gate electrode. 
     In an embodiment, the width of the lightly doped drain region (which also corresponds to a distance d between the projection of the edge of the barrier  141  away from the gate electrode  121  on the substrate  10  and the projection of the channel region  11 C on the substrate  10 ) ranges from about 0.5 μm to about 1 μm. With such a distance setting, it is possible to better reduce the leakage current of the transistor. 
       FIG. 3  is a schematic view of an array substrate according to an embodiment of the present disclosure. As shown in  FIG. 3 , the array substrate according to an embodiment of the present disclosure further includes a second insulating layer  15  disposed between the active layer  11  and the gate electrode  121 , a via  15  penetrating through the first insulating layer  13  and the second insulating layer, source/drain electrodes  16  provided on the first insulating layer  13 . The source/drain electrodes  16  are in contact with the source/drain regions  11 SD through the via V. 
     In an embodiment, the conductivity type of the channel region may be N type, and the doping type of the lightly doped drain region, and the conductivity type of the doped region of the source/drain regions may be P type. It can be understood that the doping concentration of the source/drain regions is greater than the doping concentration of the lightly doped drain region. In an embodiment, the doping concentration of the source/drain regions may range from about 4.5×10 15  to about 6×10 15  ions/cm 3 , and the doping concentration of the lightly doped drain (LDD) region may range from about 5×10 12  to about 4.5×10 15  ions/cm 3 . 
     Another aspect of the present disclosure provides a method for fabricating an array substrate. 
       FIG. 4  is a schematic flowchart of a method for fabricating an array substrate according to an embodiment of the present disclosure. As shown in  FIG. 4 , a fabricating method of an array substrate according to an embodiment of the present disclosure includes: 
     S 101 : forming an active layer on the substrate; 
     S 103 : forming a gate electrode and a first electrode on the active layer; 
     S 105 : forming a first insulating layer on the gate electrode and the first electrode; 
     S 107 : forming a barrier material layer on the first insulating layer; 
     S 109 : performing a patterning process on the barrier material layer to form a barrier and a second electrode. A projection of the second electrode on the substrate at least partially overlaps a projection of the first electrode on the substrate. A projection of a portion of the barrier extending outward from a side of the gate electrode on the substrate is within a projection of a portion of the active layer extending outward from a side of the active layer on the substrate. 
     S 111 : performing a first doping on the active layer, by using the barrier as a mask, to form source/drain regions on both sides of the channel region of the active layer and a lightly doped drain region between the channel region and the source/drain regions. 
     In an embodiment, the barrier may have an opening. A projection of the opening on the substrate at least partially overlaps a projection of the gate electrode on the substrate. By the opening in the barrier, it is possible to prevent or reduce the parasitic capacitance that may be generated between the barrier and the gate electrode. 
     In an embodiment, a width of the lightly doped drain region (corresponding to the distance d between the projection of the edge of the barrier far from the gate electrode on the substrate and the projection of the channel region onto the substrate) is approximately 0.5 μm˜1 μm. With such a distance setting, it is possible to better reduce the leakage current of the transistor. 
     In an embodiment, the first doped doping energy may be about 30 Key to about 40 Key. The conductivity type of the channel region may be N type, and the doping type of the lightly doped drain region and the conductivity type of the doped region of the source/drain regions may be P type. The doping concentration of the source/drain regions may range from about 4.5×10 15  to about 6×10 15  ions/cm 3 , and the doping concentration of the lightly doped drain (LDD) region may range from about 5×10 12  to about 4.5×10 15  ions/cm 3 . 
     The material of the second conductive layer may be selected from Molybdenum (Mo), MoNb, Al, AlNd, Ti, Cu, or combinations thereof. 
       FIG. 5  is a schematic flowchart of a method for fabricating an array substrate according to an embodiment of the present disclosure. As shown in  FIG. 5 , in an embodiment, the method for fabricating an array substrate further includes: 
     S 102 : Before forming the gate electrode and the first electrode, forming a second insulating layer on the active layer. 
     S 104 : After forming the gate electrode and the first electrode, doping the active layer with the gate electrode as a mask to define a channel region of the active layer. 
     S 113 : After forming the source/drain regions, forming a via penetrating through the first insulating layer and the second insulating layer. 
     S 115 : Forming source/drain electrodes on the first insulating layer, wherein the source/drain electrodes are in contact with the source/drain regions through the via. 
     In an embodiment, forming the gate electrode and the first electrode includes forming a gate electrode material layer on the second insulating layer, and patterning the gate electrode material layer to form the gate electrode and the first electrode. 
       FIGS. 6A-6F  are process flow diagrams of a method for fabricating an array substrate according to an embodiment of the present disclosure. A method for fabricating an array substrate according to an embodiment of the present disclosure will be further described below with reference to  FIGS. 6A-6F . 
     As shown in  FIG. 6A , a method for fabricating an array substrate according to an embodiment of the present disclosure includes form the active layer  11  on the substrate  10 . The substrate may include a glass substrate, and may also include any material suitable for a substrate such as a high molecular polymer, a metal foil, or the like. The active layer may include a silicon material. Since the low temperature polysilicon material has an electron mobility superior to that of the amorphous silicon material, the active layer may include a polysilicon material. In an embodiment, an amorphous silicon layer may be formed on a substrate, then an amorphous silicon may be subjected to an excimer laser annealing (ELA) process so that the amorphous silicon becomes polysilicon. Then perform a doping with a first conductivity type on the polysilicon. For example, when the first conductivity type is N-type, a doping dose of 1×10 12  to 2×10 12  ions/cm 3  may be used. In an embodiment, P-type silicon may be provided and then an N-well may be formed on the P-type silicon. The upper surface of the N-well is on the same surface as the upper surface of the P-type silicon. Of course, it is understood that the active layer having the first conductivity type may also be directly provided without the above-described doping step. 
     Next, a second insulating layer  15  is formed on the active layer  11 . The material of the second insulating layer may be selected from the group consisting of silicon oxide (SiOx), silicon nitride (SiNx), hafnium oxide (HfOx), silicon nitride oxide (SiON), AlOx, and any combination thereof. 
     Then, the gate electrode  121  and the first electrode  122  are formed on the second insulating layer  15 . Specifically, a gate electrode material layer may be formed on the second insulating layer, and then the gate electrode material layer may be patterned to form the gate electrode  121  and the first electrode  122 . The gate electrode material layer may be selected from a group consisting of Molybdenum (Mo), MoNb, Al, AlNd, Ti, and Cu, and any combinations thereof. A doping with a second conductivity type is then performed with the gate electrode and the first electrode as masks. For example, when the first conductivity type of the active layer is N-type, the second conductivity type is then P-type. In the situation that the second conductivity type is P-type, a doping dose ranging from 5×10 12  to 4.5×10 15  ions/cm 3  may be used. 
     As shown in  FIG. 6B , a first insulating layer  13  is further formed on the gate electrode  121  and the first electrode  122 . The material of the first insulating layer may be selected from a group consisting of silicon oxide (SiOx), silicon nitride (SiNx), hafnium oxide (HfOx), silicon nitride oxide (SiON), AlOx, and any combination thereof. 
     As shown in  FIG. 6C , a barrier material layer  14  is further formed on the first insulating layer  13 . The barrier material layer may be selected from a group consisting of Molybdenum (Mo), MoNb, Al, AlNd, Ti, and Cu, and any combinations thereof. 
     Then, as shown in  FIG. 6D , the barrier material layer  14  is processed by one patterning process to form the barrier  141  and the second electrode  142 . For example, the specific steps may be: forming a photoresist on the barrier material layer, exposing the photoresist with a mask including a pattern of the barrier and the second electrode, performing a developing, and then using the photoresist as a protective layer to etch the barrier material layer, and finally remove the photoresist. As can be seen from  FIG. 6D , the projection of the second electrode  142  on the substrate  10  at least partially overlaps the projection of the first electrode  122  on the substrate, and the portion  141   p  of the barrier  141  extending outward from a side of the gate electrode  121  is within the projection of the portion  11   p  of the active layer  11  extending outward from the side of the gate electrode  121  on the substrate (in other words, a projection of the edge  141   e  of the barrier  141  away from the gate electrode  121  on the substrate  10  is between a projection of the edge  11   e  of the active layer  11  away from the gate electrode  121  on the substrate  10  and a projection of the corresponding edge  121   e  of the gate electrode  121  on the substrate  10 ). In the process of forming the barrier and the second electrode, only one mask is used, thus the process can be simplified. Therefore, the cost can be saved and the yield can be improved. 
     The barrier may have an opening P. The projection of the opening P on the substrate  10  at least partially overlaps the projection of the gate electrode  121  on the substrate  10 . By such an opening in the barrier, it is possible to prevent or reduce the parasitic capacitance that may be generated between the barrier and the gate electrode. 
     The distance of the projection of the edge of the barrier away from the gate electrode on the substrate to a projection of the channel region to the substrate (corresponding to the width of the subsequently formed lightly doped drain region) may range from about 0.5 μm to about 1 μm. With such a distance setting, it is possible to better reduce the leakage current of the transistor. 
     Then, as shown in  FIG. 6E , a first doping is performed on the active layer  11  using the barrier as a mask  141  to form source/drain regions  11 SD on both sides of the channel region  11 C of the active layer  11  and a lightly doped drain region  11 L disposed between the channel region  11 C and the source/drain regions  11 SD. For the case where the conductivity type of the active layer is an N type, P type doping may be used so that the conductivity type of the lightly doped drain region and the doped region of the source/drain regions formed after this doping is P type. The doping energy may range from about 30 Kev to about 40 Kev. It can be understood that the doping concentration of the source/drain regions is greater than the doping concentration of the lightly doped drain region. In an embodiment, the formed source/drain regions may have a doping concentration ranges from about 4.5×10 15  to about 6×10 15  ions/cm 3 , and the lightly doped drain region may have a doping concentration ranges from about 5×10 12  to about 4.5×10 15  ions/cm 3 . 
     Next, as shown in  FIG. 6F , vias V is formed through the first insulating layer  13  and the second insulating layer  15 , and the source/drain electrodes  16  are formed on the first insulating layer  13 . It can be seen that the source/drain electrodes  16  are in contact with the source/drain regions  11 SD through the vias V. 
     The embodiments of the present disclosure also provide a display panel and a display device.  FIG. 7  is an example embodiment of a display panel  2000  that includes an array substrate  1000 . The display panel  2000  in the embodiment of the present disclosure includes the array substrate  1000  as described in  FIGS. 1A, 1B, 2, and 3 . 
       FIG. 8  is an example embodiment of a display device  3000  that includes a display panel  2000 , and the display panel  2000  includes an array substrate  1000 . In this example embodiment, the display panel  2000  is a display panel as shown in  FIG. 7 , and the array substrate  1000  is an array substrate as shown in  FIGS. 1A, 1B, 2, and 3 . The display device in the embodiments of the present disclosure may be any product or component having a display function such as a mobile phone, a tablet computer, a television, a notebook computer, a digital photo frame, a navigator, and the like. 
     Having described certain specific embodiments, these embodiments have been presented by way of example only, and are not intended to limit the scope of the present disclosure. Indeed, the novel embodiments described herein may be embodied in various other forms; furthermore, various omissions, substitutions, and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure.