JPH06104435A - Manufacture of film transistor substrate - Google Patents

Abstract

PURPOSE:To form a wiring pattern without causing the occurrence of Ta residue by etching the Al-Ta alloy film on a glass substrate in mixed acid where F<-> ions are added. CONSTITUTION:Oxie silicon films SiO are formed on both sides of a transparent glass substrate SUB1 by dipping and then are baked. The first conductive film g1 of a Cr film is sputtered to do photolithography processing, and then it is etched using ammonium cerium nitrate solution. Hereby, a gate terminal GTM, a drain terminal DTM, an anodized bus line and pad are formed. Next, the second conductive film g2 of AlTa0.85 is sputtered, and after photolithography processing, and etchant containing F<-> ions is prepared by adding 0.05-0.3% NH4F (40%) to the Al etchant consisting of the mixed acid (phosphorus acid: nitric acid: acetic acid: water = 16:1:2:1), and selective is applied. Ta residue never remain in the electrode pattern after processing, and a TFT substrate good in yield rate and high in reliability can be gotten.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thin film transistor substrate, and particularly to a thin film transistor (hereinafter, referred to as T
The present invention relates to a method for manufacturing an active matrix liquid crystal display device substrate using FT) and other TFT substrates.

[0002]

2. Description of the Related Art An active matrix type liquid crystal display device is a type of display device in which a TFT for driving a pixel is formed on a glass plate which is a substrate thereof and a switching operation is performed for each pixel. Compared with liquid crystal display devices, it has the feature that it can reproduce images with high contrast.

This pixel driving TFT has a glass substrate on which a source, a drain, a gate and other electrodes are formed of pure Al or Al-.
A thin film formed of Pd, Al-Si is formed by etching with an Al etching solution (phosphoric acid: nitric acid: acetic acid: water = 16: 1: 2: 1), and Al is formed on the thin film.
Is provided with an anodic oxide film. A TFT liquid crystal display device of this type is disclosed, for example, in "12.5 type active matrix color liquid crystal display employing a redundant configuration" (Nikkei Electronics, page 193-).
No. 210, December 15, 1986, published by Nikkei McGraw-Hill Co., Ltd.) or JP-A-2-85826.

[0004]

When pure Al is used as a gate line material of a thin film transistor, there is a problem of so-called hillock generation. As a countermeasure against this, Al containing Ta is used.
It is considered to use alloys. According to the study by the present inventors, as an etching solution for an Al.Ta alloy, an ordinary mixed solution of phosphoric acid, nitric acid, acetic acid, and water (for example, 16:
It has been found that the use of 1: 2: 1) results in a Ta residue.

The presence of this Ta residue makes it difficult to form a wiring pattern with certainty, which lowers the manufacturing yield and deteriorates the reliability of the element. In order to solve this, there is a problem that the manufacturing process becomes complicated and the cost becomes high. An object of the present invention is to solve the above-mentioned problems of the prior art, and in a TFT substrate using an Al.Ta alloy film as a material of a scanning signal line and a gate electrode, Ta residue is generated in an electrode pattern obtained by etching the alloy thin film. It is an object of the present invention to provide a method for manufacturing a TFT substrate, which is capable of obtaining a highly reliable and highly reliable TFT substrate with a high production yield.

[0006]

In order to achieve the above object, the present invention provides a method of manufacturing a thin film transistor substrate in which an Al.Ta alloy film formed on a glass substrate is patterned with an Al etching solution to form wiring. In addition, the wiring is formed without causing generation of Ta residue by adding F ⁻ ions to the Al etching solution containing mixed acid for the alloy film.

[0007]

(Function) (NH ₄ F) is added to an Al etching solution (phosphoric acid: nitric acid: acetic acid: water = 16: 1: 2: 1) consisting of a mixed acid to obtain an etching solution containing F ⁻ ions. By etching the Al.Ta alloy film with, the generation of Ta residue can be prevented and a reliable wiring pattern can be formed.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 is a plan view showing one pixel and its peripheral portion of an active matrix type color liquid crystal display device to which a method for manufacturing a TFT substrate according to the present invention is applied, and FIG. 2 is a sectional view taken along line 1-1 in FIG. 3 is a sectional view taken along line 2-2 of FIG.

As shown in FIG. 1, each pixel has two adjacent pixels.
Scanning signal lines (gate signal lines or horizontal signal lines) GL
And an adjacent two video signal lines (drain signal line or vertical signal line) DL intersect with each other (a region surrounded by four signal lines). Each pixel is a thin film transistor T
FT, transparent pixel electrode ITO1 and storage capacitor element Cad
It is configured to include d.

The scanning signal lines GL extend in the column direction and a plurality of scanning signal lines GL are arranged in the row direction. The video signal lines DL extend in the row direction and a plurality of video signal lines DL are arranged in the column direction. As shown in FIG. 2, the lower transparent glass substrate SUB1 based on the liquid crystal LC is used.
On the side, a thin film transistor TFT and a transparent pixel electrode IT
O1 is formed, and a color filter FIL and a light-shielding black matrix pattern BM are formed on the upper transparent glass substrate SUB2 side.

The lower transparent glass substrate SUB1 has a thickness of, for example, about 1.1 mm, and has a transparent glass substrate SUB.
Silicon oxide films SIO formed by dip processing or the like are provided on both surfaces of 1 and SUB2. Therefore, even if there are scratches on the surfaces of the transparent glass substrates SUB1 and SUB2, the scratches can be covered with the silicon film SIO, and the film quality of the scanning signal lines GL, the light-shielding film BM, and the like deposited on them can be made uniform. Can be kept.

Although not shown, a sealing material is formed so as to seal the liquid crystal LC along the entire periphery of the transparent glass substrates SUB1 and SUB2 excluding the liquid crystal inlet. This sealing material is made of, for example, an epoxy resin. The common transparent pixel electrode ITO2 on the upper transparent glass substrate SUB2 side is
At least one place is connected to an external lead wiring formed on the lower transparent glass substrate SUB1 side with a silver paste material. This external lead wire is formed in the same manufacturing process as the gate terminal and the drain terminal.

The respective layers of the alignment films ORI1, ORI2, the transparent pixel electrode ITO1, and the common transparent pixel electrode ITO2 are formed inside the sealing material, and the polarizing plates POL1,
The POL2 is formed on the outer surface of the lower transparent glass substrate SUB1 and the upper transparent glass substrate SUB2, respectively. The liquid crystal LC is a lower alignment film ORI1 that sets the orientation of liquid crystal molecules.
And the upper alignment film ORI2, and sealed with a sealing material.

The lower orientation film ORI1 is formed on the protective film PSV1 on the lower transparent glass substrate SUB1 side. Inside the upper transparent glass substrate SUB2 (on the liquid crystal LC side), the light shielding film BM, the color filter FIL, the protective film PSV2, the common transparent pixel electrode ITO2 (COM), and the upper alignment film O are provided.
RI2 is sequentially laminated and provided.

In this liquid crystal display device, various layers are separately stacked on the side of the lower transparent glass substrate SUB1 and the upper transparent glass substrate SUB2, and then the lower transparent glass substrate SUB1 and the upper transparent glass substrate SUB2 are overlapped with each other to form the lower transparent glass substrate. It is assembled by enclosing the liquid crystal LC between the substrate SUB1 and the upper transparent glass substrate SUB2.

The thin film transistor TFT has a gate electrode G
When a positive bias is applied to T, it operates so as to increase the channel resistance between the source and drain. The thin film transistor TFT of each pixel is composed of two (plural) divided thin film transistors TFT1 and TFT2 in the pixel. Split thin film transistors TFT1, TFT2
Each has a gate electrode GT, a gate insulating film GI, an i-type semiconductor layer AS made of i-type (intrinsic) amorphous Si, a pair of source electrodes SDI, and a drain electron gun SD2.

The source and drain are originally determined by the bias polarity between them, and in the circuit of this liquid crystal display device, the polarity is reversed during operation, so the source and drain are switched during operation. However, here, for convenience, one of the sources will be described and the other will be described as the drain. FIG. 4 is a schematic view showing only the second conductive film g2 and the i-type semiconductor layer AS in FIG. 1 for explaining the gate electrode.

The gate electrode GT is formed in a T-shaped branch so as to project in the vertical direction (upward direction in the drawing) from the scanning signal line GL. The gate electrode GT projects so as to extend beyond the respective active regions of the divided thin film transistors TFT1 and TFT2, and
The gate electrodes GT of the TFT1 and the TFT2 are integrated to form a common gate electrode and are formed continuously with the scanning signal line GL. Here, the gate electrode GT is formed of the single-layer second conductive film g2.

This second conductive film g2 is formed by sputtering 100.
It is an Al-Ta film formed to a thickness of about 0 to 5500 angstroms. In addition, 1 is provided on the gate electrode GT.
An Al anodic oxide film AOF having a thickness of about 800 Å is provided. This second conductive film g
An Al-Ta film is used as 2, and the patterning is performed by an etching treatment with an Al etching solution in which fluorine ion (F ⁻ ) is added to mixed acid, so that Ta residue does not occur and so-called hillock does not occur. A quality conductive film is formed.

Next, a method of manufacturing an electrode using the Al-Ta film including the second conductive film will be described with reference to FIGS. 5, FIG. 6, and FIG. 7 are process diagrams illustrating one embodiment of a method of manufacturing a thin film transistor substrate according to the present invention.
FIG. 6 is a cross-sectional view of a pixel portion and a gate terminal portion on the lower transparent glass substrate SUB1 side. In each drawing, the central character is the abbreviation of the process name, the left side is the pixel portion in FIG. 2, and the right side is the processing flow as seen in the cross section near the gate terminal. And FIG.
The steps (A) to (I) except for the step (D) are classified according to each photographic process, and the processing after the photographic process is finished in any sectional view of each process, and the photoresist is removed. The stages are shown.

First, in FIG. 5A, a silicon oxide film SIO is formed on both surfaces of a lower transparent glass substrate SUB1 made of 7059 glass (trade name) by a dip process, and then baked at 500 ° C. for 60 minutes. To do. A film thickness of 10 is formed on the lower transparent glass substrate SUB1.
First conductive film g1 made of a Cr film of 00 angstrom
Is provided by sputtering, and the first conductive film g1 is selectively etched using a cerium ammonium nitrate solution as an etching solution after the photographic processing.

Thus, the gate terminal GTM, the drain terminal DTM, the anodizing bus line (not shown) connecting the gate terminal GTM, the bus line (not shown) shorting the drain terminal DTM, and the anodizing bus line are connected. Anodized pad (not shown) is formed. Next, as shown in FIG. 7B, a second conductive film g2 made of Al-Ta having a film thickness of 3000 angstrom is provided by sputtering. The Al-Ta used is Al-8.5 wt% Ta (AlTa _0.85 ).

After the second conductive film g2 was photographically processed, NH ₄ F (40%) was added to an Al etching solution composed of a mixed acid of (phosphoric acid: nitric acid: acetic acid: water = 16: 1: 2: 1) in an amount of 0. 05-
Selective etching is performed by adding 0.3% to form an etching solution containing F ⁻ ions. By using this Al etching solution, T can be applied to the electrode pattern after the etching process.
a Residue does not occur.

Then, as shown in FIG. 3C, after coating with an anodic oxidation mask AO and subjecting it to photographic processing, a solution of 3% tartaric acid adjusted to pH 7 ± 0.5 with ammonia was added with ethylene glycol solution 1 The lower transparent glass substrate SUB1 is immersed in an anodizing solution made of a solution diluted to 9 and adjusted so that the anodizing current density is 0.5 mA / cm ² (constant current anodizing), and predetermined Al ₂ The anodic oxidation treatment is performed until the anodic oxidation voltage 144V required to obtain the O ₃ film thickness is reached. It is desirable to hold this state for several minutes to several tens minutes (constant voltage anodization). This is important in obtaining a uniform anodic oxide film AOF. . As a result, the second conductive film g2 is anodized, and the scanning signal line G
The film thickness is 200 on the L, the gate electrode GT and the electrode PL1.
An anodic oxide film AOF of 0 angstrom is formed.

According to a study by the present inventors, it was found that the anodic oxide film of Al.Ta alloy has less pinholes and hillocks and has a higher insulating property than the anodic oxide film of pure Al or Al.Pd alloy. It was After this, as shown in FIG.
The lower transparent glass substrate SUB1 is set in a plasma CVD apparatus, ammonia gas, silane gas, and nitrogen gas are introduced to form a silicon nitride film GI having a film thickness of 2000 angstrom, and then silane gas and hydrogen gas are introduced to make the film thickness. Of 2000 angstrom i-type amorphous Si film AS
And then a hydrogen gas and a phosphine gas are introduced to form an N (+) type amorphous Si film d having a film thickness of 300 angstroms.
Form 0.

In the figure (E), after photoprocessing, SF ₆ and CCl ₄ are used as dry etching gas and N
By selectively etching the (+) type amorphous Si film d0 and the i type amorphous Si film AS, the i type amorphous Si film A
Form an island of S. After that, as shown in FIG. 6F, after the photographic processing, silicon nitride (SiN) GI is selectively etched using SF ₆ as a dry etching gas.

Then, as shown in FIG. 7G, a first ITO film having a film thickness of 1000 angstrom is formed.
The conductive film d1 is formed by sputtering. After the photographic processing, the first conductive film d1 is selectively etched with a mixed acid solution of hydrochloric acid and nitric acid as an etching solution to form the uppermost layers of the gate terminal GTM and the drain terminal DTM and the transparent pixel electrode ITO1.

Then, as shown in (H), the film thickness is 1
Second conductive film d of 000 angstrom Cr film
2 is formed by sputtering, and the film thickness is 400
A third conductive film d3 made of an Al-Ta (AlTa _0.85 ) film of 0 angstrom is formed by sputtering. After the photo processing, the third conductive film d3 is formed on the third conductive film d3 by the same Al etching solution as that shown in FIG. 5A (phosphoric acid: nitric acid: acetic acid: water = 16:
1: 2: NH ₄ F to 1 of mixed acid from 0.008 to 0.08%
Etching is performed using an etching solution containing F ⁻ ions added to the image signal line DL and the source electrode SD.
1, the drain electrode SD2 is formed.

Next, using a dry etching apparatus, CCl ₄ and SF ₆ were introduced as etching gas to introduce N (+).
The N (+) type semiconductor layer d0 between the source and the drain is selectively removed by etching the type amorphous Si film. Finally, as shown in FIG.
A protective film PSV1 is formed by selectively etching the silicon nitride film by using a VD source and introducing ammonia gas, silane gas, and nitrogen gas as etching gas by a photo-etching technique using SF ₄ .

FIG. 8 is an explanatory diagram of the amount of fluorine ions added to the Al etching solution and the glass etching rate. The horizontal axis shows the Al etching solution (phosphoric acid: nitric acid: acetic acid: water = 16: 1: 2 :) composed of mixed acid. 40% added to 1)
The added amount (vol%) of (NH ₄ F) is shown by taking the etching rate (angstrom / min) of the immersion glass on the vertical axis.

In the figure, when fluorine ions are added to the Al etching solution, Ta in the AlTa _0.85 film is dissolved and removed, and the degree of the etching action of the fluorine ions on the lower transparent glass substrate is shown.
Ta is removed by adding ₄ F), but the etching action of the lower transparent glass substrate cannot be ignored if the amount added is too large. Therefore, in order to select this (NH ₄ F) addition amount within an appropriate range. Explaining the grounds for.

As shown in the figure, 40% (NH
_From the balance of the addition amount of 4F) and the etching action of the lower transparent glass substrate, the range of 0.05 to 0.3% is practical, and preferably 0.1 to 0.2%. I understand. By passing through the manufacturing steps described in the embodiments of the present invention described above, Ta residues are not generated in the electrodes formed by etching the AlTa _0.85 film, and reliable wiring can be formed.

In the above embodiment, the fluorine ion (F
^-) was used as a means of adding (NH ₄ F), or by using a low concentration of hydrogen fluoride (HF) in place of this. In addition, although the above-mentioned examples have been described in the case of using an Al alloy having Ta of 8.5% by weight, it has been found that the etching method in which fluorine ions are added has the same effect even if the weight ratio of Ta changes. ing.

[0034]

As described above, according to the present invention,
For example, (NH ₄ F) is added to an Al etching solution (phosphoric acid: nitric acid: acetic acid: water = 16: 1: 2: 1) consisting of a mixed acid as shown in the examples to contain an F ⁻ ion. And Al-8.5 wt% Ta with this etching solution.
By etching the film, generation of Ta residue can be prevented, a reliable wiring pattern can be formed, and a highly reliable and highly reliable TFT substrate can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing one pixel and its peripheral portion of an active matrix type color etching display device to which a method for manufacturing a TFT substrate according to the present invention is applied.

2 is a cross-sectional view taken along line 1-1 of FIG.

FIG. 3 is a cross-sectional view taken along line 2-2 of FIG.

FIG. 4 is a schematic view showing only a second conductive film and an i-type semiconductor layer in FIG. 1 for explaining a gate electrode.

FIG. 5 is a partial process diagram illustrating an embodiment of a method of manufacturing a thin film transistor substrate according to the present invention.

FIG. 6 is a partial process diagram illustrating an embodiment of a method of manufacturing a thin film transistor substrate according to the present invention.

FIG. 7 is a partial process diagram illustrating an embodiment of a method of manufacturing a thin film transistor substrate according to the present invention.

FIG. 8 is an explanatory diagram of the amount of fluorine ions added to the Al etching solution and the glass etching rate.

[Explanation of symbols]

 SUB1 Lower transparent glass substrate SUB2 Upper transparent glass substrate GL Scan signal line DL Video signal line GI Insulating film GT Gate electrode AS i type semiconductor layer SD Source or drain electrode PSV Protective film BM Light-shielding film LC Liquid crystal TFT TFT Thin film transistor ITO Transparent pixel electrode g , D Conductive film Cadd Storage capacitor AOF Anodized film AO Anodized mask GTM Gate terminal DTM Drain terminal

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[Procedure amendment]

[Submission date] October 7, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] Figure 8

[Correction method] Change

[Correction content]

[Figure 8]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Tsuki 3300 Hayano, Mobara-shi, Chiba Hitachi Ltd. Mobara factory

Claims (1)

[Claims] 1. A method of manufacturing a thin film transistor substrate, wherein an Al alloy film containing Ta formed on a glass substrate is patterned with an Al etching solution made of mixed acid to form wiring. In the method, F ⁻ ions are added to the Al alloy film. A method for manufacturing a thin film transistor substrate, characterized in that the wiring is formed without causing generation of Ta residue by etching with the Al etching solution described above.