JPH06104282A - Formation of conductive film pattern - Google Patents

Abstract

PURPOSE:To prevent breaking of an electrode and a bus line or a defective breakdown strength of an insulating film by forming mask protecting a conductive film from chemical reaction and selectively converting the conductive film to be expressed from a mask into an insulator by chemical reaction so as to generate no difference in level. CONSTITUTION:For instance, an aluminum film 10 covering one surface of a substrate consisting of glass is piled up, and thereon a mask 11 in the shape of a gate electrode 3 and a gate bus line 1 is formed. An aluminum thin film 10 of a part expressed from the mask 11 is selectively oxidized, for instance, by an anodic oxidation method. As a result, an aluminum thin film in the shape of the gate bus line 1 and the electrode 3 remains, and its periphery is converted into a transparent anode oxide film (oxide aluminum film) 31. The substrate surface after removing the mask 11 comes into the state where the gate electrode or the like are not projected while having the surface form where the surface height is almost uniform or the gate electrode or the like are rather recessed. Accordinly, a coverage defect caused by difference in level is not generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive film pattern applied to a thin film transistor (TFT) matrix arranged in a matrix on a substrate, and more particularly to a method of forming a gate electrode and a gate bus line.

[0002]

2. Description of the Related Art The gate electrode and gate bus line of a TFT matrix used for a large-screen or high-resolution liquid crystal display are required to have a low resistivity, so that an aluminum (Al) thin film is required. Often formed by. Such an aluminum thin film is patterned as a gate electrode or a gate bus line, and then an oxide film is formed on its surface by a method such as anodic oxidation. This oxide film is provided as a gate insulating film or an interlayer insulating film.

FIG. 5 is a plan view (a) of a gate bus line 1 and a gate electrode 3 made of an aluminum thin film, and a XX sectional view (b) in the same figure. In FIG. 5B, the surface of the gate electrode 3 is covered with, for example, an anodic oxide film 31. By the way, the initial thickness of this aluminum thin film is 4000
Å, thickness left after anodization is 1000Å, anodized film 31
Is about 3000Å. Therefore, the gate electrode 3
And the step between the upper surface of the gate bus line 1 and the surrounding surface reaches about 4000 Å.

As shown in FIG. 6, a gate insulating film 7, a semiconductor active layer 8, a contact layer 14 and a source / drain electrode layer 15 are formed on the surface of the substrate on which the gate electrode 3 and the gate bus line 1 are formed. The deposited layers, except the gate insulating film 7, are patterned into the structure shown in FIG. 7 to form the source electrode 4 and the drain electrode 5. Then, a drain bus line (not shown) connected to the drain electrodes 5 arranged on the same column is formed. The drain bus line extends so as to intersect the gate bus line 1.

By the way, the step difference between the gate electrode 3 and the gate bus line 1 is about 4000 Å,
The thickness of the gate insulating film 7 is about 1000Å, and the thickness of the other layers is the same or less than this, which is far from the thickness at which the steps due to the gate electrode 3 and the gate bus line 1 are flattened. Therefore, it is unavoidable that the coverage (coverage) of these films or layers on the side surfaces of the gate electrode 3 and the like becomes low. As a result,
Increased resistance or disconnection of drain electrode or drain bus line,
There has been a problem that the frequency of occurrence of dielectric breakdown or the like between the gate electrode 3 and the source / drain electrode or at the intersection of the gate bus line 1 and the drain bus line is high.

The present invention provides a method for forming a pattern of a gate electrode or the like that does not cause the above-mentioned step difference due to the use of an aluminum thin film, and thus is unlikely to cause disconnection of electrodes or bus lines or defective withstand voltage of an insulating film. The purpose is to do.

[0007]

[Means for Solving the Problems] The above-mentioned object is a mask for forming a conductive film that produces an insulator by a chemical reaction on one surface of a substrate and protecting the conductive film in a predetermined region on the surface of the substrate from the chemical reaction. And a step of selectively converting the conductive film exposed from the mask into the insulator by the chemical reaction, the method for forming a conductive film pattern according to the present invention. .

[0008]

1 is a plan view of (a), and (b) is a sectional view taken along line XX in (a). An aluminum film 10 covering one surface of a substrate 9 made of glass, for example, is deposited, and the gate electrode 3 and the gate bus line 1 are deposited on the aluminum film 10.
A mask 11 having the shape of is formed. The aluminum thin film 10 exposed from the mask 11 is selectively oxidized by, for example, an anodic oxidation method. As a result, gate bus line 1
And an aluminum thin film in the shape of the gate electrode 3 remains, and the periphery thereof is converted into a transparent anodic oxide film (aluminum oxide film) 31. After the mask 11 is removed, the surface of the substrate does not have a protruding gate electrode or the like, and the surface height is almost uniform, or rather the surface shape is such that the gate electrode or the like is recessed. Therefore, even if a gate insulating film, a semiconductor active layer, a source / drain electrode layer is formed on top of this, or even if a drain bus line that intersects with the gate bus line is formed, coverage failure due to the conventional step difference is caused. As a result, the frequency of disconnection defects of electrodes and bus lines and breakdown voltage defects of interlayer insulating layers is reduced.

[0009]

2 to 4 are process explanatory views of an embodiment of the present invention, in which (a1) to (j1) are plan views and (a2) to (j2) are corresponding XX sectional views.

For example, on one surface of the substrate 9 made of glass,
An aluminum thin film and a chromium thin film, both having a thickness of 1000 Å, are sequentially deposited by a well-known sputtering method, and then a resist layer having a pattern of the gate electrode 3 and the gate bus line 1 is formed thereon by a well-known lithographic technique. Then, the chromium thin film exposed from the resist layer is etched using, for example, a mixed solution of perchloric acid and cerium diammonium nitrate. As a result, Fig. 2 (a
As shown in 1) and (a2), a mask consisting of a chromium thin film.
11 is formed on the aluminum thin film 10.

Next, the substrate 9 is immersed in an electrolytic solution composed of, for example, a tartaric acid solution, and anodization is performed until the aluminum thin film 10 around the mask 11 becomes transparent. The conditions for this anodic oxidation are, for example, a current density of 50 A / cm ² and time of 15 minutes.
As a result, as shown in Fig. 2 (b1) and (b2), the mask 11
The aluminum thin film 10 remains only underneath, and the periphery thereof becomes the anodic oxide film 31.

Then, the substrate 9 is placed in an oxygen atmosphere at 300 ° C.
Heat treatment is performed for 60 minutes, or oxygen plasma treatment is performed in a plasma CVD (chemical vapor deposition) apparatus. By this heat treatment or oxygen plasma treatment, the oxide film becomes dense and the breakdown voltage is improved, and the unoxidized aluminum is completely oxidized, and the transmittance is improved. After that, Figure 2 (c1)
As shown in (c2) and
Are selectively removed by, for example, etching using an aqueous solution containing cerium secondary ammonium nitrate as a main component. As a result, the gate electrode 3 made of the aluminum thin film 10 and the gate bus line 1 appear.

Next, as shown in FIGS. 2 (d1) and 2 (d2), the gate insulating film 7 made of Si ₃ N ₄ and having a thickness of about 4000 Å and amorphous silicon are formed on the surface of the substrate 9 by, for example, the well-known plasma CVD method. Active layer 8 consisting of about 150 Å thick,
Then, a protective layer 12 made of Si ₃ N ₄ and having a thickness of about 1200 Å is sequentially deposited. These films and layers are formed on an almost flat surface.

Next, a positive type resist is applied on the protective layer 12, and the resist is irradiated with ultraviolet rays from the back surface of the substrate 9 and then developed. This results in Figure 3 (e1) and
As shown in (e2), a resist mask 13 self-aligned with the gate electrode 3 is formed. Gate bus line 1
The resist is removed by additional exposure using a mask that selectively covers the gate electrode 3.

Next, as shown in FIGS. 3 (f1) and 3 (f2), the protective layer 12 exposed from the resist mask 13 is removed by etching. As shown in Fig. 3 (g1) and (g2), the thickness of the n-type amorphous silicon is about 50
A contact layer 14 of 0 Å and a source / drain electrode layer 15 of titanium having a thickness of about 1000 Å are sequentially deposited. The formation of these layers may be performed by the well-known plasma CVD method and sputtering method, respectively.

Next, using the same resist mask (not shown), the source / drain electrode layer 15, the contact layer 14 and the active layer 8 are selectively etched sequentially as shown in FIGS. 3 (h1) and 3 (h2). To do. In this way, the gate electrode 3, the source electrode 4 and the drain electrode 5 and the active layer 8 are
A TFT is formed in which the TFTs are separated.

Next, for example, by a well-known sputtering method, molybdenum (Mo) having a thickness of about 2000Å is formed on the entire surface of the substrate 9.
A thin film is deposited and patterned to form a drain bus line 2 connected to the drain electrode 5 and intersecting the gate bus line 1 as shown in FIGS. 3 (i1) and (i2).

Then, by the well-known sputtering method,
An indium tin oxide (ITO) film is deposited on the entire surface of the substrate 9,
This is patterned to form a pixel electrode 6 connected to the source electrode 4, as shown in FIGS. 3 (i1) and (i2).
In this way, a TFT matrix having the gate electrode 3 made of an aluminum thin film and the gate bus line 1 is completed.

In the above description, the case where the present invention is applied to the TFT matrix is taken up, but the formation of the conductive film pattern according to the present invention can be applied to the internal wiring or the wiring substrate in other electronic devices. Needless to say.

[0020]

According to the present invention, the side surface step due to the gate electrode and the gate bus line of the TFT matrix formed on the one surface of the substrate is almost eliminated, and as a result, the poor coverage at the step portion as in the conventional case is caused. It is possible to avoid an increase in the resistance of the source / drain electrode and the drain bus line, a disconnection, or a breakdown voltage failure. As a result, the quality and reliability of the liquid crystal display device using the TFT matrix and the manufacturing yield are improved.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is a process explanatory view of the embodiment of the present invention (No. 1)

FIG. 3 is a process explanatory diagram of the embodiment of the present invention (No. 2)

FIG. 4 is a process explanatory diagram of the embodiment of the present invention (No. 3)

FIG. 5 is an explanatory diagram of conventional problems (No. 1)

FIG. 6 is an explanatory diagram of a conventional problem (No. 2)

FIG. 7 is an explanatory diagram of a conventional problem (No. 3)

[Explanation of symbols]

1 gate bus line 9 substrate 2 drain bus line 10 aluminum thin film 3 gate electrode 11 mask 4 source electrode 12 protective layer 5 drain electrode 13 resist mask 6 pixel electrode 14 contact layer 7 gate insulating film 15 source / drain electrode layer 8 active layer 31 Anodized film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location H01L 21/3205 (72) Inventor Katsuyuki Miyazaki 1015 Ueodachu, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (8)

[Claims] 1. A step of forming a conductive film which produces an insulator by a chemical reaction on one surface of a substrate, and a step of forming a mask which protects the conductive film in a predetermined region on the surface of the substrate from the chemical reaction. And a step of selectively converting the conductive film exposed from the mask into the insulator by the chemical reaction. 2. The method for forming a conductive film pattern according to claim 1, wherein the conductive film is made of a material that produces the transparent insulator by the chemical reaction. 3. The conductive film pattern includes a plurality of bus line portions extending in one direction parallel to each other on the substrate surface, and a plurality of gate electrodes extending parallel to each other from the bus line portions. The method for forming a conductive film pattern according to claim 1, wherein the conductive film pattern is formed. 4. The method for forming a conductive film pattern according to claim 1, wherein the chemical reaction is anodic oxidation. 5. The method for forming a conductive film pattern according to claim 4, wherein an oxidation treatment is performed in an oxygen atmosphere after the anodization. 6. The method of forming a conductive film pattern according to claim 4, wherein the mask is made of a metal film that is not anodized. 7. The conductive film is made of aluminum and the mask is made of a chromium film, and the aluminum conductive film exposed from the chromium film mask is selectively anodized to be converted into the insulator. 7. The method for forming a conductive film pattern according to claim 6. 8. The method of forming a conductive film pattern according to claim 5, wherein the oxidation treatment in the oxygen atmosphere is plasma oxidation.