JPH03188422A - Production of thin-film transistor array - Google Patents

Abstract

PURPOSE:To enhance the transmittance of picture elements by forming the tantalum films on auxiliary electrodes as electrodes for anodic oxidation and anodizing tantalum to form insulating films. CONSTITUTION:A power source is connected to the tantalum electrodes on the auxiliary electrodes to form the electrodes for anodic oxidation and is chemically converted up to 180V in a 1wt.% citric acid soln. to form the 1st insulating film 5 which is the anodized tantalum transparent over the entire surface. SiNx which is the 2nd insulating film 6 is then formed at 3,000Angstrom , a semiconductor layer 7 consisting of an amorphous silicon film at 2,000Angstrom , and a semiconductor layer 8 for ohmic contact consisting of phosphorus-doped amorphous silicon at 500Angstrom , continuously by a P-CVD method. The semiconductor layer 7 and the semiconductor layer 8 for ohmic contact are then worked to island shapes and further, ITO is laminated at 1,500Angstrom and transparent electrodes 9 for picture elements are formed. Cr is then laminated at 2,000Angstrom and drain electrodes 10 and source electrodes 11 are produced. The transmittance in the picture element parts is increased in this way and the defects by shorting, etc., are extremely decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is applicable to fil! used, for example, in switching elements of liquid crystal display devices. ) relates to transistor arrays.

[Conventional technology]

Thin film transistors used to drive liquid crystal display elements, etc., have become cheaper and cheaper due to the spread of liquid crystal display office equipment such as laptop computers and word processors, and liquid crystal televisions.
Active development is underway to reduce defects, increase surface area, and increase density.

In the thin film transistor array, gate electrodes and source electrodes are wired in an XY matrix to drive pixels on the edge side. Therefore, a short circuit at the intersection between the gate electrode and the source electrode becomes a major problem.

In addition, in order to provide a margin for driving a liquid crystal display device, a thin film transistor having a structure in which an additional capacitance electrode is provided has been considered, but the intersection of the additional capacitance electrode, wiring electrode, and pixel electrode is For fishing, 5iNT4 film or St
In this case, dust in the chamber due to the P-CVD method and pinholes due to abnormal growth are
This can cause short circuits and lead to defects.

Therefore, the inventors of the present invention disclosed in Japanese Patent Application No. 1-289186 that after patterning a gate electrode as shown in FIG. A transparent insulating film is formed, and SiNx
They proposed a structure that prevents defects due to short circuits between electrodes by forming an insulating film with a two-layer structure with a film or a SiO□ film.

[Problem to be solved by the invention]

However, in the conventional manufacturing method of a thin film transistor array that uses anodized tantalum as an insulating film between transparent electrodes for additional capacitance and transparent electrodes for pixels, a tantalum film that becomes an insulating layer after anodization is formed on the gate electrode. A power source was connected to the tantalum film on the non-pixel portion of the substrate, and the pixel portion was immersed in a solution to perform anodic oxidation. However, during anodic oxidation, the tantalum near the solution interface is completely anodized first, and that part becomes insulated, and the supply of current stops on the solution side near the interface, so tantalum cannot be completely anodized. As shown in Figure 4, it is difficult to
Unoxidized tantalum 13 remained thin and uneven, which significantly lowered the transmittance of the pixel.

In view of the above-mentioned problems, the present invention has been made for the purpose of providing a method for manufacturing a thin film transistor array using an anodized tantalum film having high transmittance.

[Means to solve problems]

That is, the present invention provides a method for manufacturing a thin film transistor array in which an insulating film made of an anodized tantalum film is interposed between a transparent electrode for an additional capacitor and a transparent electrode for a pixel. (b) forming a tantalum film on the entire surface of the glass substrate on which the gate electrode and the auxiliary electrode are formed; (c) using the tantalum film on the auxiliary electrode as an anode; The above problems were solved by a method for manufacturing a thin film transistor array that includes the steps of using an oxidizing electrode and anodizing tantalum to form an insulating film.

[Effect]

In the present invention, since the tantalum on the gate electrode and the auxiliary electrode connected to the gate electrode is used as the anodizing electrode, the current flows evenly through the gate electrode in the insulating film formation area, so that the insulating layer can be completely anodized. Therefore, it is possible to manufacture a thin film transistor array with high transmittance in the pixel portion and with very few defects such as short circuits.

〔Example〕

Embodiments of the present invention will be described in detail using the drawings. FIG. 1 is a plan view showing a gate electrode pattern of a thin film transistor array according to the present invention, FIG. 2 is a cross-sectional view showing a configuration example of the thin film transistor array, and FIG. 3 is a plan view showing a gate electrode pattern of a thin film transistor array according to a conventional method. It is a diagram.

A transparent electrode 2 for additional capacitance made of ITO is placed on a glass substrate 1 (
After patterning to a thickness of 1,500 layers, a tantalum film of 2,000 layers is formed by sputtering and processed into the gate electrode 3. At this time, the gate electrode pattern is not the independent one shown in FIG. 3, but a pattern having an auxiliary electrode 4 that connects each gate electrode in common as shown in FIG. Form a film.

A power source is connected to the tankle film on the auxiliary electrode, used as an anodizing electrode, and anodized to 180 V in a 0.1% by weight citric acid solution to form a first insulating film 5 made of anodized tantalum that is completely transparent. Formed. Although anodic oxidation can be performed satisfactorily at an anodizing voltage lower than this value, unoxidized tantalum remains and causes unevenness, reducing the transmittance. The surfaces of the gate electrode 3 and the auxiliary electrode 4 are also partially oxidized, but not completely.

Next, by P-CVD method, SiN, which is the second insulating film 6,
3,000 people formed the semiconductor layer 7 made of amorphous silicon film, 2000 people formed the semiconductor layer 7 made of an amorphous silicon film, and 500 people formed the semiconductor layer 8 for ohmic contact made of phosphorous-doped amorphous silicon.
processed into an island shape, and then laminated with 1500 layers of ITO.
A transparent electrode 9 for the pixel is formed, 2000 Cr layers are laminated,
A drain electrode IO and a source electrode 11 were produced. Finally, 3,000 SiNx layers, which are the passivation film 12, were deposited using the P-CVD method to complete the thin film transistor array.

Note that the auxiliary electrodes are separated after the panel is formed.

[Comparative example]

A gate electrode pattern is formed by a manufacturing method similar to that of the previous embodiment. The gate pattern at this time is an independent pattern one by one as shown in FIG.

Next, 1000 tantalum films are formed by sputtering. When an electrode is connected to this film and anodic oxidation is performed, the area near the solution interface is completely oxidized and becomes transparent, but the current does not reach the solution side near the interface and unoxidized tantalum remains in spots. In addition, it is not preferable to increase the formation voltage in order to cause current to flow because dielectric breakdown occurs near the interface in this case.

Even if the thin film transistor array is then completed using the same manufacturing process as in the example, it will look like the one shown in Figure 4, so the transmittance of the pixel portion in the visible region measured by a spectrometer will be 100% of the transmittance of the glass substrate before processing. This is 40% lower than that of the previous year.

〔Effect of the invention〕

Thanks to the present invention, the transmittance of the pixel portion of the conventional thin film transistor array in the visible region measured by a spectrometer is 90%, compared to 40% when the unprocessed glass substrate is 100%. A high-performance thin film transistor array can be fabricated, and image quality has improved. In addition, there were very few defects due to short circuits, etc., and the yield was improved.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an example of a gate electrode and auxiliary electrode pattern of a thin film transistor array of the present invention;
FIG. 2 is a sectional view showing one embodiment of the structure of a thin film transistor array according to the present invention. FIG. 3 is a plan view showing an example of a gate electrode pattern of a conventional thin film transistor array, and FIG. 4 is a sectional view showing an example of the configuration of a conventional thin film transistor array. 1...Glass substrate 2...Transparent electrode for additional capacitance 3...Gate electrode 4...Auxiliary electrode 5...First insulating film 6...Second insulating film 7...Semiconductor layer 8 ...Semiconductor layer for ohmic contact 9...Transparent electrode for pixel 10...Drain electrode 11...Source electrode 12...Passivation film 13...Unoxidized tantalum Patent application Hitotoppan Printing Co., Ltd. Company representative Kazuo Suzuki Figure 2

Claims (1)

[Claims] (1) In the method for manufacturing a thin film transistor array in which an insulating film made of an anodized tantalum film is interposed between a transparent electrode for additional capacitance and a transparent electrode for pixels, (a) gate electrodes are formed using tantalum on a glass substrate; (b) forming a tantalum film on the entire surface of the glass substrate on which the gate electrode and the auxiliary electrode are formed; (c) forming a tantalum film on the auxiliary electrode as an anodizing electrode; and a step of anodizing tantalum to form an insulating film, a method for manufacturing a thin film transistor array comprising at least the above steps.