JPH06188267A - Manufacture of thin film transistor array - Google Patents

Abstract

PURPOSE:To eliminate a short-circuit failure of a TFT due to a step by burying a metal film serving as a metal wiring for making an electrode contact with the TFT in the surface of an insulating substrate and reduce a resistance value of the metal wiring remarkably by forming a large sectional area of the metal wiring. CONSTITUTION:First, protrusions 22 of a stamper 21 made of a polycarbonate resin are brought into contact with paste materials 23 containing Ta, and the paste materials 23 are bonded on the tops of the protrusions 22. On the other hand, a gel film 20 is applied to the surface of a soda-lime glass substrate 1. The side of the protrusions 22 of the stamper 21 is pushed on the surface of the gel film 20 and the glass substrate 1 is heat treated under this condition. The stamper 21 is removed and the glass substrate 1 is heat-treated and a glass body 25 is formed on the glass substrate 1. Next using an electrolytic plating process, a crystal growth of Ta films 26 is performed on recesses 24, and the surface is polished and the surfaces of the glass body 25 and the Ta films 26 are smoothed. Then, a TFT is formed on the glass substrate 1 and the Ta films 26 are used as a gate wiring and a gate electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improving the performance of thin film transistor arrays used in liquid crystal displays, image sensors and the like.

[0002]

2. Description of the Related Art Active matrix drive liquid crystal displays are becoming the mainstream of liquid crystal displays because of their high display quality. However, the conventional liquid crystal drive display has various problems in order to display a large area and a large capacity.

FIG. 5 shows a sectional structure of a thin film transistor (TFT) used in a conventional liquid crystal display. In the figure, 1 is a glass substrate, 41 is a gate electrode, and 42.
Is a gate insulating film, 43 is a pixel electrode, and 44 is an amorphous silicon layer. Further, 45 is a drain electrode connected to the pixel electrode 43, and 46 is an n-type amorphous silicon layer for making an ohmic contact between the amorphous silicon layer 44 and the drain electrode 45. Further, 47 is a source electrode for sending an image signal from the outside, which is connected to the amorphous silicon layer 44 through the n-type amorphous silicon layer 48. Further, the source electrode 47 is connected to the electrode 49. The electrode 49 is a wiring for supplying an image signal to the TFT of each pixel.

FIG. 6 shows a plan view of the TFT array. In the figure, 51 is a gate selection line. The gate selection line 51 is electrically connected to the gate electrode 41 of FIG. 5, and the gate electrode 41 and the gate selection line 51 are formed of a metal thin film made of the same material. 50 is TF
T is shown.

In order to operate the TFT array of FIG. 6, a selection voltage is applied to the gate selection line 51, and by this application, all the TFTs connected to one gate selection line 51.
50 is turned on. When the pixel signal voltage is applied to the electrode 49 at this timing, the voltage is written in the pixel electrode 43. Adjacent gate selection line 51 at the next timing
When the selection voltage is applied to the
It is written in the pixel electrode 43 connected to T. By repeating these, the orientation of the liquid crystal formed on the TFT array can be controlled to display an image.

[0006]

However, various problems have occurred as the display capacity of liquid crystal displays has increased. These issues are summarized below.

(1) That is, as the display capacity increases, the area allocated to one pixel inevitably decreases. On the other hand, since the area occupied by the TFT 50, the gate selection line 51, and the image power supply line cannot be made very small, the aperture ratio (the ratio of the displayable area to the entire area) becomes small. Therefore, the utilization efficiency of the illumination light is reduced, and the displayed image becomes dark.

(2) If the width of the gate selection line 51 is narrowed to improve the aperture ratio, the resistance value of the gate selection line 51 increases, and the response speed of the gate selection line 51 decreases in relation to the parasitic capacitance. Will end up. Therefore, the voltage applied to the gate of the TFT 50 becomes insufficient, and the pixel electrode writing of the image signal becomes insufficient. This phenomenon becomes a particular problem in a large area and large capacity display. As a method to solve this problem,
It is conceivable to increase the thickness of the wiring thin film. However, if the film thickness is made thick, the film thickness of the gate electrode 41 shown in FIG. 5 becomes thick and the step becomes large. For this reason, a short circuit is induced in the step portion, which becomes a problem in the manufacturing process of the TFT.

By the way, in the conventional TFT array,
When a Ta metal material is used for the gate electrode 41, its film thickness is usually 0.3 μm and its width is about 10 μm. Also,
The electric resistivity of Ta itself is 12 μΩ / cm, that is, 0.
Since it is 4Ω / □, the wiring resistance is about 40Ω / mm.

In a conventional large-sized liquid crystal display having a side length of about 30 cm, the resistance value up to the end of the substrate is about 12 kΩ. When considering driving a parasitic capacitance of 1000 pF with this resistance value, the RC time constant is 12 μs. Therefore, it takes 24 μs including the rise and fall only with the RC time constant. On the other hand, from the television system, writing must be completed in 30 μs or less per line. Complete writing of image data requires at least 2-3 times the RC time constant, that is, about 75 μs. Therefore, even if sufficient data can be written near the feeding point of the gate selection line 51,
In the vicinity of the end of the gate selection line 51, data writing becomes insufficient, resulting in deterioration of image quality.

The present invention has been made in order to solve the above-mentioned conventional problems, and a manufacturing process and a large area can be easily performed, a large area and a large capacity display can be performed, and a stepless TFT array. It is intended to provide a manufacturing method.

[0012]

[Means for Solving the Problems] That is, according to a first manufacturing method of the present invention, after a gel film having a property of forming an insulator by hydrolysis / condensation is applied to the surface of an insulating substrate, at least the tip portion of the convex portion is applied. The convex side of the mold material having the metal film is pressed against the gel film surface, and in this state, the gel film is dried and heat-treated to form a concave part on the surface of the insulating substrate and an insulating film having a metal film on the bottom surface of the concave part. This is accomplished by forming another metal film on the metal film of the recess by using a plating method so as to be substantially flush with the surface of the insulation film, and then forming a TFT on the insulation substrate.

In the second manufacturing method of the present invention, a gel film having a property of forming an insulator by hydrolysis / condensation is applied to the surface of an insulating substrate, and then a convex portion made of a metal film is formed on the surface of the gel film. The convex side of the mold material is pressed, the gel film is dried and heat-treated in this state to form an insulating film on the insulating substrate, and then the mold material is removed from the insulating film to transform the metal film into an insulating film. This is achieved by leaving the TFT and forming a TFT on the insulating substrate.

FIG. 1 is a cross-sectional view of a main part of a TFT array manufactured by the manufacturing method of the present invention. In the figure, 1
Is a glass substrate as an example of an insulating substrate, and 2 is a metal wiring whose surface portion is formed flush with the insulating film 3 on the glass substrate 1. The structure of the TFT 12 formed on the surfaces of the metal wiring 2 and the insulating film 3 is almost the same as the structure of the conventional TFT. That is, the metal wiring 2
And the gate insulating film 4 is formed on the insulating film 3, and the pixel electrode 5 and the amorphous silicon layer 6 are formed on a part of the gate insulating film 4.
And an n-type amorphous silicon layer 7 for making ohmic contact between the amorphous silicon layer 6 and the drain electrode 9 is formed on the amorphous silicon layer 6. Also,
Reference numeral 10 is a source electrode for sending a pixel signal from the outside,
It is connected to the amorphous silicon layer 6 through the n-type amorphous silicon layer 8. In addition, 11 is a protective layer.

As the glass substrate 1, soda lime glass, quartz glass, borosilicate glass or the like can be used. As the metal wiring 2, a low-resistivity metal material such as Ta, Al, Cr, or Cu can be used.

Next, the manufacturing method of the present invention will be described with reference to FIGS. 2, 3 and 4. 2 is a partial cross-sectional view showing a manufacturing process according to the first method of the present invention, and FIG.
4 and FIG. 4 are partial cross-sectional views showing the manufacturing process according to the second method of the present invention.

The first manufacturing method will be described. First, the gel film 20 is applied on the glass substrate 1 (see FIG. 3).
a). On the other hand, a mold material (stamper) 21 having a convex portion 22
Is brought into contact with a paste-like material 23 containing a metal material (FIG. 2B), and the paste-like material 23 is attached to the tip end portion of the convex portion 22 of the mold material 21 (FIG. 2C). Next, the convex portion 22 of the mold material 21 is pressed against the surface of the gel film 20 (FIG. 8D). In this state, the glass substrate 1 is
Perform preliminary heat treatment at ~ 80 ° C for about 15-30 minutes,
The recess 24 is formed on the surface of the gel film 20 and the recess 24 is formed.
A metal film 23 is formed on the bottom surface of the.

As the gel film 20, for example, a gel film obtained by hydrolyzing and condensing a raw material solution containing an organometallic compound containing an alkoxyl group can be used. The shape of the mold material 21 is not limited as long as it has a convex portion 22 capable of forming a desired concave portion 24 on the gel film 20, and for example, a mold material 21 made of nickel or polycarbonate resin is used. Can be used.

When forming the concave portion 24 on the surface of the gel film 20, the mold depth of the mold material 21 (the convex portion 22) is formed.
It is preferable that the height of the gel film 20 is equal to or smaller than the thickness of the gel film 20.

The metallic material forming the paste 23 is not particularly limited, and may be, for example, Ta, Al, C described above.
r or Cu can be used. The binder (binder) for maintaining the metal material in the paste-like material 23 in a stable and uniform dispersion state is, for example, polyester resin, epoxy resin, phenol resin, olefin, rubber, acrylic resin, urethane resin or these. 2 or more types of compositions and the like. The solvent is also not particularly limited as long as it dissolves the resin to be used, for example, a hydrocarbon solvent or a halogenated hydrocarbon solvent (preferably having a boiling point of 50 to 200 ° C., such as toluene, cyclohexane, acetic acid. Ester, xylene, etc.).

The above components are mixed and dispersed at an appropriate ratio, and the metallic material is reacted with the functional groups of the binder to form a paste 23.
To create. The viscosity of the paste 23 is 4
About 0 to 120 poise is preferable.

Subsequently, the mold material 21 is removed from the gel film 20, and the glass substrate 1 is heat-treated at 300 to 400 ° C. for 0.5 to 24 hours, so that the recess 24 is formed on the glass substrate 1. A glass body 25 is obtained (e in the figure).

After that, a metal film 26 is formed on the metal film 23 in the recess 24. As a film forming method, a plating method capable of forming a film at high speed is adopted. The plating method may be either electrolytic plating method or electroless plating method. Moreover, although a metal material such as Ta, Al, Cr, or Cu can be used as the metal film 26 to be formed, it is preferable to use a metal material having good adhesion to the metal film 23.

Instead of the order of the steps, it is possible to form the metal film 26 on the metal film 23 of the recess 24 and then heat the glass substrate 1 to obtain the glass body 25.

After that, a TFT is formed on the glass body 25 on which the metal film 26 to be the metal wiring is formed by a conventionally known method.

Next, the second manufacturing method will be described with reference to FIGS.

Similar to the case of the first manufacturing method, first, the gel film 20 is applied on the glass substrate 1 (FIGS. 3a and 4).
a). On the other hand, the mold material 21 includes a glass plate 27, a resin layer 28,
Alternatively, a metal film 29 may be laminated (FIG. 3b), and the metal film 29 may be selectively removed by photolithography to form a pattern, which is used as a protrusion (FIG. 3c). Alternatively, a paste-like material 23 containing a metal material is printed in a pattern on the resin layer 28 (see FIG. 4).
b) In addition, it is also possible to use the one in which the convex portion made of the metal film 29 is formed with the paste-like material 23 as the nucleus by the plating method (FIG. 4c).

The resin layer 28 is made of a resin that is soluble in an organic solvent (eg acetone, ethyl acetate, ethylene chloride, formic acid, toluene, etc.).
MA (polymethylmethacrylate resin) is a suitable material. Further, as the metal film 29, for example, the above-mentioned Ta, Al, Cr or Cu can be used.

The metal film 29 side of the mold material 21 is pressed against the surface of the gel film 20 (FIGS. 3d and 4d), 30 to 80 ° C.
Then, preliminary heat treatment is performed for about 15 minutes. Then, the glass substrate 1 is immersed in an organic solvent to form the resin layer 28 of the mold material 21.
Dissolve. Then, the glass plate 27 is removed from the glass substrate 1 to leave the metal film 29 on the glass body 25 (FIGS. 3e and 4e). Heat treatment is performed in this state to obtain the glass body 25 on the glass substrate 1. The heat treatment time and temperature are in the same range as in the case of the first manufacturing method. In the mold material 21, the glass plate 27 may be omitted and the resin layer 28 and the metal film 29 may be formed into two layers.

The surface of the metal film 29 is the glass body 25.
When it is formed in a recessed state as compared with the surface, a metal film 29 can be further formed on the surface of the metal film 29 by a plating method to smooth the surface of the glass body 25.
Alternatively, when the surface of the metal film 29 is formed so as to project from the surface of the glass body 25, the surface of the metal film 29 may be polished to smooth the surface of the metal film 29 and the surface of the glass body 25. .

After that, a TFT is formed on the glass body on which the metal film to be the metal wiring is formed by a conventionally known method.

[0032]

According to the present invention, since the metal film serving as the metal wiring for making electrode contact with the TFT is embedded in the surface of the insulating substrate and there is no step, the metal wiring is not short-circuited and the metal wiring is disconnected. A large area can be taken. Therefore,
It is possible to greatly reduce the resistance value of the metal wiring, and it is possible to solve the problem of gate line propagation delay caused by the internal parasitic resistance of the metal wiring. Further, since the surface of the insulating substrate is smooth, the TFT formation and the coupling efficiency on the insulating substrate are improved.

Furthermore, it is also possible to form metal wirings having different widths while keeping the resistance value of the metal wiring constant, which can contribute to the improvement of the aperture ratio.

[0034]

Example 1 First, the convex portion 22 of a stamper 21 made of a polycarbonate resin was brought into contact with a paste-like material 23 containing Ta, and the paste-like material 23 was formed on the tip portion of the convex portion 22 to a thickness of about 5 μm. Made to adhere to On the other hand, the gel film 20 formed by the sol-gel method was applied to the surface of the soda lime glass substrate 1.

The protrusion 22 side of the stamper 21 is attached to the gel film 20.
Press on the surface, and in this state the glass substrate 1 at 60 ° C for 3
Heat treatment was performed for 0 minutes. After that, when the stamper 21 was removed, a recess 24 was formed on the surface of the gel film 20,
The Ta film 23 was formed on the bottom surface of the recess 24.
Further, this glass substrate 1 was heat-treated at 350 ° C. for 15 minutes to form a glass body 25 on the glass substrate 1.

Next, the recess 24 is formed by using an electroplating method.
Then, the Ta film 26 was crystal-grown. Further, the surface of the Ta film 26 on which the crystal was grown was polished to smooth the surface of the glass body 25 and the surface of the Ta film 26. Then, a TFT was formed on the glass substrate 1 and the Ta film 26 was made to function as a gate wiring and a gate electrode.

Example 2 First, PM is placed on the glass plate 27.
The MA resin layer 28 was formed into a film having a thickness of 2 μm by spin coating, and A was formed on the PMMA resin layer 28 by vacuum deposition.
1 film 29 was formed to a thickness of 5 μm. Then, the Al film 29 is selectively removed by a photolithography method,
This was used as the convex portion of the stamper 21. On the other hand, the gel film 20 formed by the sol-gel method was applied to the surface of the soda lime glass substrate 1.

The convex side of the stamper 21 is attached to the gel film 20.
Press on the surface, and in this state, glass substrate 1 at 80 ° C for 1
After performing a preliminary heat treatment for 5 minutes, the glass substrate 1 was immersed in an ethyl acetate solution and kept in this state for 30 minutes to dissolve the PMMA resin layer 28. further,
Heat treatment was performed at 350 ° C. for 15 minutes to vitrify.

An Al film 29 was formed on the glass body 25 so that its surface was substantially flush with the surface of the glass body 25. Then, a TFT is formed on the glass substrate 1 and the Al
The film 29 was made to function as a gate wiring and a gate electrode.

Example 3 First, PMMA having a thickness of 2 μm
A paste-like material containing Cr was printed in a pattern on the resin layer 28 by a silk screen printing method. Next, using this printed pattern as a core, a 5 μm thick Cr film 29 was formed on the printed pattern by electrolytic plating. On the other hand, the gel film 20 formed by the sol-gel method was applied to the surface of the soda lime glass substrate 1.

The Cr film 29 side of the stamper 21 is pressed against the surface of the gel film 20. In this state, the glass substrate 1
Heat treatment was performed at 15 ° C for 15 minutes.

Thereafter, the glass substrate 1 is dipped in an acetone solution and kept in this state for 25 minutes,
The PMMA resin layer 28 was dissolved. Further, it was vitrified by heat treatment at 350 ° C. for 15 minutes.

A Cr film 29 was formed on the glass body 25 so that its surface was substantially flush with the surface of the glass body 25. Then, a TFT is formed on the glass substrate 1 and the Cr
The film 29 was made to function as a gate wiring and a gate electrode.

[0044]

As described above, in the TFT array of the present invention, it is possible to obtain an insulating substrate in which a metal film to be a metal wiring is buried by a simple manufacturing process.

Further, since the metal wiring is embedded in the surface of the insulating substrate, the resistance of the metal wiring can be greatly reduced, and the short circuit failure of the TFT due to the step can be eliminated, so that a large-capacity, large-area display can be obtained. Even when applied, the propagation delay of the metal wiring can be reduced and the image quality deterioration can be prevented. Furthermore, by forming a metal wiring having a large aspect ratio, the width of the metal wiring can be narrowed and the aperture ratio can be increased.

[Brief description of drawings]

FIG. 1 is a sectional structural view of a TFT of the present invention.

FIG. 2 is a partial cross-sectional view showing a manufacturing process according to the first method of the present invention.

FIG. 3 is a partial cross-sectional view showing a manufacturing process according to a second method of the present invention.

FIG. 4 is a partial sectional view showing another embodiment of FIG.

FIG. 5 is a sectional structural view of a conventional TFT array.

FIG. 6 is a plan view of a conventional TFT array.

[Explanation of symbols]

 1 glass substrate 2 metal wiring 3 insulating film 4 gate insulating film 5 pixel electrode 6 amorphous silicon layer 7 n-type amorphous silicon layer 8 n-type amorphous silicon layer 9 drain electrode 10 source electrode 11 protective film 12 TFT

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display area H01L 21/3205

Claims (4)

[Claims] 1. A method of manufacturing a thin film transistor, which comprises the following steps: (A) a step of applying a gel film having a property of forming an insulator by hydrolysis and condensation on the surface of an insulating substrate; B) After pressing the convex side of a mold material having a metal film on at least the tip of the convex part against the gel film surface, the gel film is dried and heat-treated in this state to form a concave part on the surface on the insulating substrate. And a step of forming an insulating film having the metal film on the bottom surface of the recess, (C) forming another metal film on the metal film on the bottom surface of the recess by a plating method so as to be substantially flush with the surface of the insulation film. Step (D) A step of forming a thin film transistor on the insulating substrate obtained in the step (C). 2. A method of manufacturing a thin film transistor, which comprises the following steps: (A) a step of applying a gel film having a characteristic of forming an insulator by hydrolysis and condensation on the surface of an insulating substrate; B) A step of forming an insulating film on the insulating substrate by pressing the convex side of a mold material having a convex part made of a metal film against the surface of the gel film and then drying and heat treating the gel film in this state. (C) By removing the mold material from the insulating film,
A step of leaving the metal film on the insulating film; (D) a step of forming a thin film transistor on the insulating substrate obtained in the step (C). 3. After the step (C), (C ′) a step of forming another metal film on the metal film so as to be substantially flush with the surface of the insulating film by a plating method. The method of manufacturing a thin film transistor according to claim 2. 4. The step (C) after the step (C), the step of: (C ′) polishing the insulative film surface to form the metal film surface substantially flush with the insulating film surface. Item 3. A method of manufacturing a thin film transistor according to Item 2.