BRIEF DESCRIPTION OF THE DRAWINGS
The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
FIGS. 1
a to 1e are crosssections of a conventional method for fabricating electroluminescent devices;
FIG. 2 is a top view illustrating the pixel structure of an embodiment of an active matrix substrate employed in a flat panel display; and
FIGS. 3
a to 3h are crosssections of an embodiment of a method for fabricating electroluminescent devices with the COA process.
FIG. 4 schematically shows another embodiment of a system for displaying images.
DETAILED DESCRIPTION OF THE INVENTION
The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
A method for manufacturing electroluminescent devices with the COA process prevents the color filter layer, the planarization, and photoresists from directly contacting the metal conductive layer (i.e. drain electrode and pad electrode), thereby protective the thin film transistor against electrostatic discharge. Thus, the yield of the fabrication process is improved.
FIG. 2 is a partial top view of an embodiment of an electroluminescent device comprising an active matrix substrate. The active matrix substrate comprises a substrate 110 which is defined as an active region 112, and a pad region 114. Gate pads 116 and data pads 118 are formed in the pad region 114, wherein the gate pads 116 electrically connect to a gate electrode 126 through a gate line 122, and the data pads 118 electrically connect to a source electrode 128 through a data line 124.
FIGS. 3
a to 3h are sectional diagrams of FIG. 2 along lines A-A′ and B-B′, showing the method for fabricating electroluminescent devices.
First, referring to FIG. 3a, the substrate 110 with the active region 112 and the pad region 114 is provided. A thin film transistor (TFT) 120 is formed on the active region 112 and a pad structure 130 is formed on the pad region 114. The thin film transistor 120 comprises a semiconductor layer 121, a gate electrode 123, a gate insulator 125, a source electrode 127, and a drain electrode 129, and the pad structure 130 comprise a pad electrode 133. The thin film transistor 120 can be an amorphous-silicon thin film transistor, low temperature poly-silicon thin film transistor (LTPS-TFT), organic thin film transistor (OTFT), or others. The structure of the thin film transistor 120 illustrated is an example, and is not intended to be limitative of the invention. Herein, the gate insulator 125 can be a silicon nitride, and the substrate 110 can be a transparent insulating material such as glass or plastic. Further, the source electrode 127 and drain electrode 129, and pad electrode 133 can be of the same material and formed by the same process
Next, referring to FIG. 3b, a protective layer 140 is completely formed on the substrate 110 to cover the thin film transistor 120 and the pad structure 130. Suitable material of the protective layer 140 can comprise silicon nitride, silicon oxide, BPSG, PSG or organic resin film.
Next, referring to FIG. 3c, color filter patterns 145 are formed on the protective layer 140 of the active region 112, wherein the color filter patterns 145 are separated by first contact holes 146. The color filter patterns 145 can comprise red, green, or blue color-filtering units, to achieve a full-color display. Since the protective layer 140 completely covers the drain electrode 129 and pad electrode 133, no color filter or photoresist directly contacts the metal conductive layer (drain electrode 129 and pad electrode 133) during the step of forming color filter patterns 145.
Next, referring to FIG. 3d, a planarization layer 150 is blanketly formed on the substrate 110. Herein, the planarization layer 150 can be SiOx, SiNx (x≧1), spin-on glass (SOG) or insulating organic compound. It should be noted that the planarization layer 150 and the metal conductive layer (drain electrode 129 and pad electrode 133) are separated by the protective layer 140.
Next, referring to FIG. 3e, the planarization layer 150 is patterned to form a second contact hole 151 and a third contact hole 152 passing therethrough. The second contact hole 151 exposes the surface of the protective layer 140 directly on the drain electrode 129, and the third contact hole 152 exposes the surface of the protective layer 140 directly on the pad electrode 133. Wherein, the second contact hole and the third contact hole are formed by the same process.
Next, referring to FIG. 3f, a photoresist layer 160 is formed on the planarization layer 150. Specifically, the photoresist layer 160 is formed on the side wall of the planarization layer in the second and third contact holes 151 and 152. The protective layer is etched with the photoresist layer 160 acting as a mask, forming a drain via hole 170 and a pad via hole 172, resulting in the second and third contact holes directly lying on the drain and pad via hole respectively. Referring to FIG. 3g, the photoresist layer 160 is then removed. The drain via hole 170 exposes the drain electrode 129, and the pad via hole 172 exposes the pad electrode 133. Specifically, the drain via hole 170 and the pad via hole 172 are formed by the same process after the formation of the color filter patterns 145 and the planarization layer 150. It should be noted that the size 181 of the second contact hole 151 is larger than the size 182 of the drain via hole 170, casing the first contact hole 146 exposing the top surface of the protective layer 140 around the drain via hole 170. Further, the size 183 of the third contact hole 152 is larger than the size 184 of the pad via hole, casing the third contact hole 152 exposing the top surface of the protective layer 140 around the pad via hole 172.
Referring to FIG. 3h, an organic light emitting diode 180 is formed on the planarization layer 150, wherein organic light emitting diode 180 comprises an anode electrode 181, electroluminescent layers 182, and a cathode electrode 183. Specifically, the anode electrode 181 is electrically connected to the drain electrode 129. Thus, fabrication of the thin film transistor is completed. In an embodiment of the invention, the organic light-emitting diode exhibits white emission.
Since the color filter layer, planarization layer and photoresist layer do not directly contact the drain electrode (or the pad electrode) through the drain via hole (or pad via hole), electrostatic discharge (ESD) damage to the electrode of the thin film transistor can be prevented.
FIG. 4 schematically shows another embodiment of a system for displaying images which, in this case, is implemented as a display panel 400 or an electronic device 600. The described active matrix organic electroluminescent device can be incorporated into a display panel that can be an OLED panel. As shown in FIG. 4, the display panel 400 comprises an active matrix organic electroluminescent device, such as the active matrix organic electroluminescent device 100 shown in FIG. 2. The display panel 400 can form a portion of a variety of electronic devices (in this case, electronic device 600). Generally, the electronic device 600 can comprise the display panel 400 and an input unit 500. Further, the input unit 500 is operatively coupled to the display panel 400 and provides input signals (e.g., an image signal) to the display panel 400 to generate images. The electronic device 600 can be a mobile phone, digital camera, PDA (personal data assistant), notebook computer, desktop computer, television, car display, or portable DVD player, for example.
While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
Patent Application
20080032431
