JP3006994B2 - Active matrix substrate manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an active matrix substrate which constitutes a display device in combination with a display medium such as a liquid crystal.

[0002]

2. Description of the Related Art Conventionally, an active matrix display device in which picture element electrodes are arranged in a matrix on an insulating substrate and these picture element electrodes are selectively driven via switching elements has been put to practical use. In this active matrix display device, a drive voltage is applied to a selected picture element electrode and a counter electrode facing the selected picture element electrode, and the optical characteristics of a display medium sandwiched between these electrodes change. This change in optical characteristics is visually recognized as a display pattern. Among such active matrix display devices, a liquid crystal display device using a liquid crystal as a display medium is widely used because it has advantages such as thinness, low power consumption, full color, and the like. In particular, a thin film transistor (hereinafter referred to as TF)
A large-sized, high-density, high-contrast display is realized by an active matrix display device using (T) as a switching element.

FIG. 5 is a plan view of a conventional active matrix substrate using a TFT as a switching element.
In FIG. 5, between pixel electrodes 1 arranged in a matrix, gate bus lines 2 functioning as scanning lines are provided in parallel with each other, and a gate electrode 3 branches from these gate bus lines 2. . On this gate electrode 3, a TFT 4 as a switching element is formed. At right angles to the gate bus lines 2, source bus lines 5 functioning as signal lines are provided in parallel. T
The source electrode 6 of the FT 4 is connected to the source bus line 5. The drain electrode 7 of the TFT 4 is connected to the pixel electrode 1.
It is connected to the. A gate insulating film formed on the entire surface of the substrate is interposed between the gate bus wiring 2 and the source bus wiring 5. A display medium such as a liquid crystal is sealed between the active matrix substrate thus configured and the opposing substrate to form an active matrix display device.

FIG. 6 is a sectional view of the display device using the active matrix substrate shown in FIG. In FIG. 6, a gate electrode 3 made of Ta is formed on a glass substrate 11 to a thickness of 2500 angstroms, and an anodic oxide film 12 made of Ta ₂ O ₅ is formed on the gate electrode 3 to a thickness of 3000 angstroms. Is formed. A gate insulating film 13 made of SiNx is formed on the entire surface of the glass substrate 11 so as to cover the anodic oxide film 12.
Is deposited to a thickness of 3000 Angstroms.

Further, an intrinsic semiconductor amorphous silicon (hereinafter a-S) is formed on the gate insulating film 13 above the gate electrode 3.
i (i)) is formed to a thickness of 1000 angstroms. Further, a source electrode 6 and a drain electrode 7 are formed on the semiconductor layer 14. The source electrode 6 has a contact layer 6a located thereunder and a source electrode part 6b located thereabove. Similarly, the drain electrode 7 has a lower contact layer 7a and a drain electrode portion 7b located thereon. These contact layers 6a, 7a
Is made of n + type semiconductor amorphous silicon (hereinafter referred to as a-Si (n +)) having a thickness of 500 angstroms. Further, the source electrode portion 6b and the train electrode portion 7b
It is made of Ti having a thickness of 000 angstroms.

On the gate insulating film 13 and the drain electrode 7, a picture element electrode 1 made of ITO is formed.
The pattern is formed to a thickness of 00 angstroms. Furthermore, a protective film 15 made of SiNx having a thickness of 3000 Å is formed on the entire surface of the substrate, and an alignment film 16 is formed thereon.

[0007] A glass substrate 17 is provided on the opposing substrate facing the active matrix substrate formed as described above.
Color film 18 and black stripe 19 on top
Are formed. Further, the entire surface of the color film 18 and the black stripe 19 of the opposing substrate is covered with ITO.
A counter electrode 20 made of and an alignment film 21 are formed. A liquid crystal layer 22 is sealed between the alignment films 16 and 21 to form an active matrix display device.

[0008]

In the above-mentioned conventional active matrix display device, a parasitic capacitance is generated at a portion where the gate electrode 3 and the drain electrode 7 overlap. Due to this parasitic capacitance, the voltage of the pixel electrode 1 connected to the drain electrode 7 also changes according to the voltage change of the gate electrode 3. Since the chemical characteristics of the display medium change in accordance with the voltage applied between the picture element electrode 1 and the counter electrode 20, the picture element electrode 1
The change in the voltage has a great effect on the contrast of the display screen. In particular, when a liquid crystal is used as a display medium,
To prevent a DC component from being applied to the liquid crystal layer 22, the counter electrode 2
The AC drive is performed by adjusting the DC component of the voltage applied to 0 equal to the DC component applied to the picture element electrode 1. However, since the counter electrode 20 is common to all the pixel electrodes 1, if the parasitic capacitance is not constant for each of the pixel electrodes 1, the voltage of the counter electrode 20 is adjusted for all of the pixel electrodes 1. I can't. As described above, when there is a distribution in which the parasitic capacitance changes abruptly in the adjacent area on the liquid crystal display screen, display unevenness occurs on the screen.

The reason why the parasitic capacitance generated at the overlapping portion of the gate electrode 3 and the drain electrode 7 is not constant for each picture element is that the area of the overlapping portion between the drain electrode portion 7b and the contact layer 7a and the gate electrode 3 is different from each other. There is variation in picture elements. The variation in the area of the overlapping portion is caused by the difference between the drain electrode portion 7 b and the contact layer 7.
This is caused by the fact that “a” is formed so as to be shifted from the normal position as a result of mask alignment with respect to the gate electrode 3. In particular,
In the case of forming a large-sized display device, such overlay is easily shifted due to shrinkage of the substrate or divisional exposure. When performing divided exposure, it is possible to prevent a rapid change in the amount of misalignment near the division boundary line caused by a manufacturing error of the photo mask, a distribution of lens distortion, etc. from becoming a sudden change in the area of the superimposed portion. Absent.

On the other hand, as a conventional countermeasure, a method of preventing display unevenness by newly forming a compensation pattern so that display unevenness does not occur on the screen even when a shift occurs in superposition (Japanese Patent Laid-Open No. However, the aperture ratio is reduced because the effective pixel area is reduced. As another method, a method of improving the superposition accuracy of the drain electrode on the gate electrode by exposing the back surface from the glass substrate using a negative resist (Japanese Patent Laid-Open No. Sho 62
However, the formation of the drain electrode requires two photolithographic etching steps including formation of a pattern with a positive resist.

The present invention solves the above-mentioned conventional problem, and forms a pattern in which a parasitic capacitance formed at an overlapping portion of a gate electrode and a drain electrode is constant for each picture element in an adjacent region by one time. An object of the present invention is to provide a method for manufacturing an active matrix substrate by etching.

[0012]

According to a method of manufacturing an active matrix substrate of the present invention, a light-shielding gate bus wiring is formed in a matrix on a light-transmitting insulating substrate, and the gate bus wiring is formed on the gate bus wiring or A method for manufacturing an active matrix substrate, wherein a thin film transistor is formed on a light-shielding gate electrode branched from the gate bus wiring, and a pixel electrode is electrically connected to a drain electrode of the thin film transistor.
In forming the pattern of the drain electrode of the thin film transistor, the resist pattern of the source electrode and the drain electrode is collectively formed without hard bake processing with a positive type characteristic using a positive type image inversion corresponding photoresist, and then the insulating substrate is formed. Performing a matching exposure by the gate electrode by exposing from the back surface of the substrate, and forming a resist pattern for separating the source electrode and the drain electrode with negative-type characteristics by image inversion processing. The above object is achieved.

[0013]

According to the above structure, the image inversion resist is used for the resist pattern forming process of the active matrix substrate, so that the light-shielding gate electrode formed on the light-transmitting insulating substrate can be used as the source electrode and the drain electrode. A necessary portion is formed as a resist pattern, and furthermore, in order to uniformly form the area of the overlapping portion of the source electrode and the drain electrode, the light-transmissive insulating film is formed by the image reversing process using the characteristics of a negative image reversal resist. The same resist can be used to separate and form a source electrode and a drain electrode by performing self-alignment using the right and left light wraparound of the gate electrode from the back surface of the conductive substrate.

[0014]

Embodiments of the present invention will be described below.

FIG. 1 shows a main part of an active matrix substrate according to an embodiment of the present invention, wherein a is a plan view thereof, and b is a
13 is a cross-sectional view taken along the line BB ′ of FIG. Components having the same functions as those in FIGS. 5 and 6 are denoted by the same reference numerals, and description thereof will be omitted.

Gate electrode 3 on transparent insulating substrate 11
In order to form a source electrode and a drain electrode via the anodic oxide film 12, the gate insulating film 13 and the semiconductor layer 14, contact layers serving as contact layers 6c and 7c which determine the area of the source electrode and the drain electrode are formed above. Deposit. Then, on this contact layer, an image reversal-compatible photoresist (manufactured by Hoechst Japan, product number: AZ5214)
Is applied with a film thickness of 1.2 μm. A contact layer including a contact layer 6c below the source electrode and a contact layer 7c below the drain electrode is collectively exposed to ultraviolet (UV) light on the resist-coated substrate, and then exposed to an alkali developer (T
Perform development processing at a MAH concentration of 2.38% (bake processing)
None). In other words, the resist that is exposed to light
Organic acid is generated and dissolved by neutralization reaction with organic alkali.
Understand. Accordingly, a positive resist pattern P1 shown in FIG.

Next, the resist pattern P1 remaining on the substrate is treated as a negative resist pattern in which the light is applied.
V) After performing the entire surface exposure as a matching exposure for a time (300 mj / cm ² ) sufficient for the left and right light to wrap around the gate electrode 3 evenly inside, heat treatment called reversal bake is performed to crosslink the resist ( 120 ° C, 5
Minutes) , the resist exposed to the light is developed
It is difficult to dissolve in water. In addition, flood flood exposure (120
mj / cm ² ) to increase solubility in developer
The overall contrast to dissolution
I can take it. By the phenomenon treatment again, as shown in FIG. 3, a negative resist pattern P2 having a predetermined indentation amount (2 μm) obtained by uniformly irradiating light inward from the gate electrode 3 to the inside is uniformly formed over the entire substrate. Figure 1
(A) and (b), as shown in FIG.
Contact layers 6c and 7c are obtained. Since the amount of indentation determines the substantial area of the source electrode and the drain electrode, the source electrode and the drain electrode can be uniformly formed over the entire substrate by hard baking and etching after the phenomenon. For this substrate, the subsequent steps are processed in the same manner as in the prior art. As described above, in the method of manufacturing the active matrix substrate, by arranging the source electrode and the drain electrode above the gate electrode 3 uniformly over the entire substrate, a high-quality active matrix substrate without display unevenness can be formed. .

The source electrode on a large-area insulating substrate,
When the pattern of the drain electrode was formed, the boundary divided into a plurality of blocks by division exposure or the like was confirmed by the above-described manufacturing method, but no display unevenness was observed at the division boundary. FIG. 4 shows a comparison between the pattern of the conventional method in FIG. 4B and the pattern of the present invention in FIG.

[0019]

As described above, according to the present invention, by using an image inversion resist for forming a pattern of a large active matrix substrate with divisional exposure, a parasitic capacitance formed at an overlapping portion of a gate electrode and a drain electrode can be obtained. Can form a constant pattern for each of the picture elements in the proximity region, and a liquid crystal display device having no display unevenness can be configured.

In addition, since unnecessary patterns such as compensation patterns are unnecessary and the source electrode and the drain electrode are self-aligned, the overlapping design can be reduced, and
The effective pixel area can be increased in conjunction with the miniaturization of.

Further, a pattern can be formed utilizing the characteristics of the negative / positive screen by one-time resist coating, and the manufacturing process can be shortened.

[Brief description of the drawings]

FIG. 1 shows a main part of an active matrix substrate manufactured according to the present invention, wherein a is a plan view and b is a BB ′ cross-sectional view of a.

FIG. 2 shows a main part of an active matrix substrate in a first step of pattern formation according to the present invention, wherein a is a plan view thereof;
FIG. 2B is a cross-sectional view taken along line CC ′ of FIG.

FIG. 3 shows a main part of an active matrix substrate in a second step of pattern formation according to the present invention, wherein a is a plan view thereof;
b is a DD ′ sectional view of a.

FIG. 4 is a plan view showing a main part of an active matrix substrate according to the present invention, and FIG. 4b is a plan view showing a main part of a conventional active matrix substrate;

FIG. 5 is a plan view of an active matrix substrate used in a conventional active matrix display device.

6 is a cross-sectional view of the display device using the active matrix substrate shown in FIG. 5, taken along the line AA 'in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Picture element electrode 2 Gate bus wiring 3 Gate electrode 4 TFT 6 Source electrode 6c, 7c Contact layer 7 Drain electrode 11 Insulating substrate P1 Positive resist pattern P2 Negative resist pattern

Claims (1)

(57) [Claims] 1. A light-shielding gate bus wiring is formed in a matrix on a light-transmitting insulating substrate, and a thin film transistor is formed on the gate bus wiring or on a light-shielding gate electrode branched from the gate bus wiring. A method of manufacturing an active matrix substrate in which a pixel electrode is electrically connected to a drain electrode of the thin film transistor, wherein a pattern of the drain electrode of the thin film transistor is formed by using a positive type image inversion corresponding photoresist. After the resist pattern of the source electrode and the drain electrode is collectively formed without hard baking processing, the resist is exposed from the back surface of the insulating substrate to perform the matching exposure by the gate electrode. Forming a resist pattern that separates the source electrode and the drain electrode with the characteristics of Method of manufacturing a Torikusu board.