BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a process chart to explain essential portion of a process for manufacturing a first substrate (thin-film transistor substrate), which constitutes a liquid crystal display panel of the present invention;
FIG. 2 represents drawings to explain a process for manufacturing the thin-film transistor of Embodiment 1 of the liquid crystal display panel of the present invention in concrete details;
FIG. 3 represents drawings continued from FIG. 2 to explain a process for manufacturing the thin-film transistor of Embodiment 1 of the liquid crystal display panel of the present invention in concrete details;
FIG. 4 represents drawings continued from FIG. 3 to explain a process for manufacturing the thin-film transistor of Embodiment 1 of the liquid crystal display panel of the present invention in concrete details;
FIG. 5 represents drawings continued from FIG. 4 to explain a process for manufacturing the thin-film transistor of Embodiment 1 of the liquid crystal display panel of the present invention in concrete details;
FIG. 6 represents drawings continued from FIG. 5 to explain a process for manufacturing the thin-film transistor of Embodiment 1 of the liquid crystal display panel of the present invention in concrete details;
FIG. 7 represents diagrams to explain equivalent circuit of an active matrix type liquid crystal display system;
FIG. 8 is a schematical cross-sectional view to explain an example of approximate arrangement of a typical longitudinal electric field type (the so-called TN type) liquid crystal display system;
FIG. 9 represents schematical drawings to explain an arrangement of a pixel of the liquid crystal display panel explained in FIG. 8 and an arrangement of the thin-film transistor to make up the pixel; and
FIG. 10 represents process charts to compare number of processes in the conventional photolithographic method and an ink jet direct drawing method to manufacture gate electrodes and source-drain electrodes in essential portion of a process for manufacturing thin-film transistor of a first panel PNL1.
DETAILED DESCRIPTION THE PREFERRED EMBODIMENT
Detailed description will be given below on an embodiment of the invention referring to the attached drawings.
FIG. 1 is a process chart to explain an essential portion of a process for manufacturing a first substrate (a thin-film transistor substrate) to be used in a liquid crystal display panel of the present invention. First, a gate electrode and a gate line are prepared by direct drawing of ink jet on inner surface (above an underlying film) of a first substrate (thin-film transistor substrate), which is preferably made of a glass substrate. The direct drawing of the gate electrode and the gate line is the same as the gate direct drawing process as explained the lower portion of FIG. 10.
In the island forming process, after the formation of the gate, a gate insulator film, a silicon semiconductor layer, and an n+ silicon layer, which is to be turned to a contact layer, are deposited in this order by CVD method (3-layer CVD method). A photosensitive resist is coated on this silicon layer, and an island pattern of the resist is prepared by photolithographic process including the light exposure using a light exposure mask and development process. Then, etching is performed, and an island as required is prepared after removing off the photoresist and rinsing.
In the source-drain electrode forming process (S-D forming process), an electroconductive ink for forming the source-drain electrodes is applied by direct drawing of ink jet, thereby leaving a gap between the opposed ends of the source electrode and the drain electrode, and a channel is prepared in the island.
In the process for forming the interlayer insulator film, an interlayer insulator film is formed on the entire region on the substrate including the source-drain electrodes. By photolithographic process, at least the channel region including the opposed ends of the source electrode and the drain electrode is exposed.
In the pixel forming process, a transparent conductive film TCF preferably made of ITO is formed first by sputtering to cover the exposed channel region and the interlayer insulator film. A photoresist is coated on the sputtered transparent conductive film TCF. The resist of the channel region is removed by the photolithographic process. A gap is prepared, which is narrower than the gap between the opposed ends of the source electrode and the drain electrode formed by direct drawing of ink jet. In this case, the photoresist is also removed on free ends of the data line, the gate line, and the gate electrode so that the pixel electrode can be separated from the data line and the gate line.
On the portion where the photoresist has been removed a transparent conductive film TCF is prepared by etching. Then, the remaining photoresist is removed off and rinsed. Gap etching is performed on channel region. Thus, an opposed structure of the source electrode and the drain electrode of the transparent conductive film TCF, positioned opposite to each other with a narrow gap, is formed. In this case, the pixel electrode connected to the source electrode is also prepared. Then, an orientation film is deposited, and after rubbing process, the thin-film transistor substrate is completely formed.
FIG. 2 to FIG. 6 each represents drawings to explain a process for manufacturing the thin-film transistor as described above in concrete details. FIG. 2(a) to FIG. 4(a) each represents a plan view, and FIG. 2(b) to FIG. 4(b) each represents a cross-sectional view of an essential portion along a dotted line. First, as shown in FIG. 2, a gate insulator film GI is formed on a gate line GL and a gate electrode GT, which have been prepared on inner surface of a glass substrate SUB1 (i.e. a first substrate) by the ink jet method. On this gate insulator film GI, a silicon semiconductor layer SI and an n+ contact layer nSI are deposited, and the island to form an active layer of the thin-film transistor is prepared by photolithographic process.
On this active layer with the center on the channel region of the thin-film transistor, a conductive layer including a source electrode SD1 a data line DL, and a drain electrode SD2 is formed by direct drawing of ink jet. In this case, a gap (distance) D between the source electrode SD1 and the drain electrode SD2 is 10 μm or more, which is the limitation in the direct drawing of ink jet. The source electrode and the drain electrode may be switched over to each other, while it is explained here as if these are fixed as shown in the drawings.
As shown in FIG. 3, an interlayer insulator film INS is deposited to cover a conductive layer, which is to be turned to the source electrode SD1, the data line DL, and the drain electrode SD2. The interlayer insulator film INS on the channel region formed on the opposed portions of the source electrode SD1 and the drain electrode SD2 is removed by photolithographic process, and the conductive end portion, which is to be turned to the source electrode SD1 and the drain electrode SD2 as well as the n+ contact layer nSI, are exposed.
The transparent conductive film TCF preferably made of ITO is formed by sputtering on the entire region of the substrate including the conductive end portion, which is to be turned to the source electrode SD1 and the drain electrode SD2, and the exposed portion of the n+ contact layer nSI, and a photoresist RG is coated on it. The photoresist on the channel region is removed by the photolithographic process, and a groove V is formed on this photoresist RG. The groove V has a gap narrower than the gap between the opposed ends of the source electrode and the drain electrode prepared by direct drawing of ink jet. In this case, on the photoresist RG, a light exposure mask with a pattern is used to remove free end portions of the data line, the gate line and the gate electrode so that the pixel electrode is separated from the data line and the gate line (see FIG. 4).
The transparent conductive film TCF on the portion where the photoresist RG has been removed is prepared by etching. Then, as shown in FIG. 5, the remaining photoresist is removed off and rinsed, and the transparent conductive film is exposed. On a portion connected to the transparent conductive film laminated on the source electrode layer SD1, the pixel electrode PX is prepared. Then, gap etching is performed on the transparent conductive film on the channel region. And an opposed structure of the source electrode SD1 and the drain electrode SD2 of the transparent conductive film TCF is obtained, which is opposed to each other with a gap “d” smaller than the gap “D” between the opposed ends of the source electrode SDLA and the drain electrode SD2A prepared by direct drawing of ink jet.
Then, as shown in FIG. 6, the n+ contact layer nSI is processed by etching, and a channel is formed on the underlying silicon semiconductor layer SI. Further, the orientation film is deposited and rubbing process is performed, and the thin-film transistor substrate is prepared. A color filter substrate (not shown) is attached on the thin-film transistor substrate. After a liquid crystal is sealed in it, a liquid crystal display panel is prepared. A driving circuit, a backlight and other structural members are combined with the liquid crystal display panel, and a liquid crystal display system is completed.
FIG. 7 represents diagrams to explain equivalent circuit of an active matrix type liquid crystal display system. FIG. 7(a) is a circuit diagram of the entire liquid crystal display panel, and FIG. 7(b) is an enlarged view of a pixel portion PXL shown in FIG. 7(a). In FIG. 7(a), a multiple of pixel portions PXLs are arranged in matrix form on the display panel PNL. Each pixel portion PXL is selected by a gate line driving circuit GDR and it is turned on according to a display data signal sent from a data line (also called source line) driving circuit DDR.
Specifically, to match the gate line GL selected by the gate line driving circuit GDR, a display data (voltage) is supplied to the thin-film transistor TFT on the pixel portion PXL of the liquid crystal display panel PNL via the data line DL from the data line driving circuit DDR.
As shown in FIG. 7(b), the thin-film transistor TFT to make up the pixel portion PXL is provided at an intersection of the gate line GL and the data line DL. The gate electrode GT of the thin film transistor TFT is connected to the gate line GL, and the data line DL is connected to the drain electrode or the source electrode (drain electrode in this case) SD2 of the thin-film transistor TFT.
The drain electrode or the source electrode (source electrode in this case) SD1 of the thin-film transistor TFT is connected to the pixel electrode PX of the liquid crystal (element) LC. The liquid crystal LC is positioned between the pixel electrode PX and the common electrode CT and is driven by the data (voltage) supplied to the pixel electrode PX. An auxiliary capacity Ca to temporarily maintain the data is connected between the drain electrode SD2 and an auxiliary capacity line CL.
The drain electrode or the source electrode as shown in FIG. 7 is prepared in the embodiment of the present invention as described above.
Patent Application
20080055508
