JPH0327024A - Thin-film diode - Google Patents

Abstract

PURPOSE:To decrease the influence of an etchant and obtain the thin-film diodes having excellent display characteristics by forming a semiconductor layer to a region enclosing the overlap part of a transparent conductive film electrode and a metallic electrode. CONSTITUTION:A picture element electrode 1A and a scanning electrode 1B of transparent conductive film are formed on a glass substrate 4, then the semiconductor film 2C is formed. The semiconductor layer 2C is then patterned in such a manner that the metallic electrodes 3A, 3B to be formed next include the part to be superposed on the already formed transparent conductive film electrode and thereafter, the metallic electrodes 3A, 3B are patterned. As a result, the substrate is directly coated by using only the semiconductor layer 2C with the region of the substrate where the transparent conductive film electrodes 1A, 1B are not formed; therefore, the exposed part of the substrate is reduced and the influence of the etching liquid is lessened over the entire part. The diode having the excellent display characteristics is thus obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a thin film diode used in an active matrix type liquid crystal display device, and in particular to a thin film diode that prevents the influence of a glass substrate and enables excellent display characteristics. Regarding diodes. [Conventional technology] Liquid crystal displays with a large number of pixels have a high contrast ratio. The active matrix method is effective for providing high-quality displays with wide viewing angles. This method is equipped with one or more nonlinear elements (electrical elements with nonlinear voltage-current characteristics) for every pixel, and reduces the influence of electrical leakage when driving other pixels, thereby reducing the image signal. Improve display quality by improving the S/N ratio of There are two types of nonlinear elements: 3@child and 2-terminal devices, but the 2-terminal method is easier to manufacture and is superior to the 3-terminal method in terms of cost. In particular, ring diodes made of non-quality silicon utilize the forward characteristics of diodes,
Excellent image uniformity. Figure 3 shows the equivalent circuit of an active matrix. In FIG. 3, 13 is a ring diode +'IA, and a pixel electrode 15 is a counter electrode. 16 is a liquid crystal, 1B is a scanning line (scanning: n. Same as electrode). l2 is a data line (same as the counter electrode). FIG. 4 shows a conventional ring diode, FIG. 4+a+ is a plan view, and FIG. This ring diode is connected to pixel electrodes IA, scanning electrodes IB. It consists of a semiconductor layer 2A and metal electrodes 3A and 3B. Such a ring diode is prepared as follows. ITO (indium 1
A transparent conductive mill made of tin oxide)! The pixel electrode IA and the scanning electrode 1B are formed by patterning using a photoprocessing method. Next, pin layers of non-quality silicon are sequentially laminated and then patterned using a photo process to form the semiconductor layer 2B. Next, a metal film for metal electrodes was deposited and patterned using a photoprocessing method to form gold m1.
i-pole 3A. Form 3B. Subsequently, metal electrode 3A3B
Using this as a mask, the semiconductor layer 2B can be etched to obtain the semiconductor layer 2A. In this way, the ring diode can be manufactured by three photoprocessing steps (four times if etching using the metal electrode as a mask is included), and the manufacturing method is simple. [Problems to be Solved by the Invention] However, in a substrate equipped with such a ring diode, the area of the substrate where the transparent conductive film is not affected is exposed to corrosive agents such as etching gas or etching solution during the patterning process. There was a problem in that the display characteristics of liquid crystals deteriorated due to the influence of these corrosive agents. This effect is particularly noticeable in the exposed glass substrate area. This invention has been made in view of the above points, and its purpose is to reduce the exposed area of the substrate as much as possible.
The purpose of this invention is to provide an FjI film diode that provides excellent display characteristics. [Means for Solving the Problems] According to the present invention, the above object is to provide a scanning electrode, which is a transparent conductive film electrode, a pixel electrode, and a semiconductor layer on a substrate. In a thin film diode formed by laminating metal electrodes, a transparent conductive film electrode I
This can be achieved by providing a shaped semiconductor layer 2C in a region surrounding the overlapping portions of A, IB and gold III electrodes 3A, 3B.

[Effect]

When a semiconductor layer is formed in a region that includes the overlapping portion, a region of the substrate that is not covered by a transparent conductive film electrode is directly covered with only the semiconductor layer, and an exposed portion of the substrate is formed. This reduces the overall effect of the corrosive agent. [Example] Next, an example of this invention will be explained based on the drawings. FIG. 1 shows a ring diode according to an embodiment of the present invention.
-A arrow view. This ring diode differs from the conventional ring diode shown in FIG. 4 in the region of the semiconductor layer. In a conventional ring diode, semiconductor 2A is within the area defined by metal electrodes 3A, 3B. The semiconductor 1'l2C of the present invention is a region that includes the overlapping portion of the transparent conductive film electrode and the metal electrode. Such a ring diode can be manufactured as follows. ITO is deposited as a transparent conductive film on the glass substrate 4 and patterned with a first pattern to form the pixel electrode IA.
Then, non-quality silicon is deposited and plasma etched using a mixed gas of CP4 and 0■ to pattern the amorphous silicon and form the semiconductor layer 2C. Give form. In this process, the semiconductor layer is patterned so that the metal electrode that will be formed in the next step includes the part that will overlap with the already formed transparent conductive film electrode without touching it. Next, Mo was deposited as a metal electrode and phosphoric acid was applied in a third pattern. nitric acid. Etching the MO using a mixed solution of acetic acid to form metal electrodes 3A,
Form 3B by patterning. In this way there is an area of the glass substrate that is directly covered with only the semiconductor layer, and the area of the exposed glass substrate that is not covered by any layer is reduced. Since the exposed area of the glass substrate is the area that undergoes many buttering processes,
The effect of corrosive agents is due to the large exposed group Fi in this region.
By reducing the fil region, the influence of corrosive agents is reduced as a whole, and the display characteristics of the liquid crystal are improved. For example, the crystal display device I having the thin film diode according to this embodiment was heated at 70°C.
When a durability test was conducted at a temperature of On the other hand, in the conventional liquid crystal display device with ¥I# diode, 20
Contrast decreased over time. This is because the thin film diode according to the embodiment of the present invention is less affected by corrosive agents, and lowering of the resistance of the liquid crystal is prevented. Note that the conventional thin film diode manufacturing method requires four patterning steps, but the thin film diode manufacturing method according to the embodiment of the present invention requires only three patterning steps, which simplifies the manufacturing process.

FIG. 2 shows a thin film diode according to a modified example of the present invention, and FIG. 2(b) is a plan view of FIG.
-B arrow view. The layer structure of the transparent conductive film electrode and the metal electrode is reversed from that shown in FIG. That is, the metal electrode consisting of the chest is patterned in the first pattern, and the transparent conductive film electrode II is patterned in the third pattern. In the thin film diode shown in Figure 2, M has low light transmittance.
Since the olll is formed under the semiconductor layer, it has the advantage of being able to prevent photodeterioration of the semiconductor layer due to light from the bottom of the glass substrate. [Effects of the Invention] According to this invention, a transparent conductor is formed on a substrate! Scanning electrodes and pixels are membrane electrodes! In a thin film diode formed by laminating a electrode, a semiconductor layer, and a metal electrode, the semiconductor layer is formed in a region surrounding the overlapping part of the transparent conductive film electrode and the metal electrode, so the area of the substrate where the transparent conductive film electrode is not affected As a result, there is a portion directly covered only by the semiconductor layer, which reduces the exposed area of the substrate, resulting in a thin film diode which reduces the influence of corrosive agents and allows for excellent display properties of liquid crystals.

[Brief explanation of drawings]

FIG. 1 shows a ring diode according to an embodiment of the present invention, and FIG.
2 shows a ring diode according to a modification of the present invention, and FIG. 2 (al is a plan view, and FIG. 2 (
bl is a view taken along the line B-B in Fig. 2 (l1), Fig. 3 is an equivalent circuit diagram of a ring diode, Fig. 4 is a conventional ring diode, Fig. 4 fat is a plan view, and Fig. 4 ( 'b) is a C-C arrow view of Figure 4 (al. IA:ii!!i
Element Et & (Transparent thin film electrode) 1B = Scanning electrode (Transparent thin film electrode)
I! J electrode) 2C: Semiconductor layer, Fig. 1 Fig. 2

Claims (1)

[Claims] 1) In a thin film diode in which a scanning electrode, which is a transparent conductive film electrode, a pixel electrode, a semiconductor layer, and a metal electrode are laminated on a substrate, a semiconductor formed in a region surrounding the overlapping part of the transparent conductive film electrode and the metal electrode. A thin film diode characterized in that it comprises a layer.